WorldWideScience

Sample records for trophic levels effects

  1. Reef Fishes at All Trophic Levels Respond Positively to Effective Marine Protected Areas

    Science.gov (United States)

    Soler, German A.; Edgar, Graham J.; Thomson, Russell J.; Kininmonth, Stuart; Campbell, Stuart J.; Dawson, Terence P.; Barrett, Neville S.; Bernard, Anthony T. F.; Galván, David E.; Willis, Trevor J.; Alexander, Timothy J.; Stuart-Smith, Rick D.

    2015-01-01

    Marine Protected Areas (MPAs) offer a unique opportunity to test the assumption that fishing pressure affects some trophic groups more than others. Removal of larger predators through fishing is often suggested to have positive flow-on effects for some lower trophic groups, in which case protection from fishing should result in suppression of lower trophic groups as predator populations recover. We tested this by assessing differences in the trophic structure of reef fish communities associated with 79 MPAs and open-access sites worldwide, using a standardised quantitative dataset on reef fish community structure. The biomass of all major trophic groups (higher carnivores, benthic carnivores, planktivores and herbivores) was significantly greater (by 40% - 200%) in effective no-take MPAs relative to fished open-access areas. This effect was most pronounced for individuals in large size classes, but with no size class of any trophic group showing signs of depressed biomass in MPAs, as predicted from higher predator abundance. Thus, greater biomass in effective MPAs implies that exploitation on shallow rocky and coral reefs negatively affects biomass of all fish trophic groups and size classes. These direct effects of fishing on trophic structure appear stronger than any top down effects on lower trophic levels that would be imposed by intact predator populations. We propose that exploitation affects fish assemblages at all trophic levels, and that local ecosystem function is generally modified by fishing. PMID:26461104

  2. Reef Fishes at All Trophic Levels Respond Positively to Effective Marine Protected Areas.

    Directory of Open Access Journals (Sweden)

    German A Soler

    Full Text Available Marine Protected Areas (MPAs offer a unique opportunity to test the assumption that fishing pressure affects some trophic groups more than others. Removal of larger predators through fishing is often suggested to have positive flow-on effects for some lower trophic groups, in which case protection from fishing should result in suppression of lower trophic groups as predator populations recover. We tested this by assessing differences in the trophic structure of reef fish communities associated with 79 MPAs and open-access sites worldwide, using a standardised quantitative dataset on reef fish community structure. The biomass of all major trophic groups (higher carnivores, benthic carnivores, planktivores and herbivores was significantly greater (by 40% - 200% in effective no-take MPAs relative to fished open-access areas. This effect was most pronounced for individuals in large size classes, but with no size class of any trophic group showing signs of depressed biomass in MPAs, as predicted from higher predator abundance. Thus, greater biomass in effective MPAs implies that exploitation on shallow rocky and coral reefs negatively affects biomass of all fish trophic groups and size classes. These direct effects of fishing on trophic structure appear stronger than any top down effects on lower trophic levels that would be imposed by intact predator populations. We propose that exploitation affects fish assemblages at all trophic levels, and that local ecosystem function is generally modified by fishing.

  3. Trophic assimilation efficiency markedly increases at higher trophic levels in four-level host-parasitoid food chain.

    Science.gov (United States)

    Sanders, Dirk; Moser, Andrea; Newton, Jason; van Veen, F J Frank

    2016-03-16

    Trophic assimilation efficiency (conversion of resource biomass into consumer biomass) is thought to be a limiting factor for food chain length in natural communities. In host-parasitoid systems, which account for the majority of terrestrial consumer interactions, a high trophic assimilation efficiency may be expected at higher trophic levels because of the close match of resource composition of host tissue and the consumer's resource requirements, which would allow for longer food chains. We measured efficiency of biomass transfer along an aphid-primary-secondary-tertiary parasitoid food chain and used stable isotope analysis to confirm trophic levels. We show high efficiency in biomass transfer along the food chain. From the third to the fourth trophic level, the proportion of host biomass transferred was 45%, 65% and 73%, respectively, for three secondary parasitoid species. For two parasitoid species that can act at the fourth and fifth trophic levels, we show markedly increased trophic assimilation efficiencies at the higher trophic level, which increased from 45 to 63% and 73 to 93%, respectively. In common with other food chains, δ(15)N increased with trophic level, with trophic discrimination factors (Δ(15)N) 1.34 and 1.49‰ from primary parasitoids to endoparasitic and ectoparasitic secondary parasitoids, respectively, and 0.78‰ from secondary to tertiary parasitoids. Owing to the extraordinarily high efficiency of hyperparasitoids, cryptic higher trophic levels may exist in host-parasitoid communities, which could alter our understanding of the dynamics and drivers of community structure of these important systems. © 2016 The Authors.

  4. Influence of Climate Change and Trophic Coupling across Four Trophic Levels in the Celtic Sea

    Science.gov (United States)

    Lauria, Valentina; Attrill, Martin J.; Pinnegar, John K.; Brown, Andrew; Edwards, Martin; Votier, Stephen C.

    2012-01-01

    Climate change has had profound effects upon marine ecosystems, impacting across all trophic levels from plankton to apex predators. Determining the impacts of climate change on marine ecosystems requires understanding the direct effects on all trophic levels as well as indirect effects mediated by trophic coupling. The aim of this study was to investigate the effects of climate change on the pelagic food web in the Celtic Sea, a productive shelf region in the Northeast Atlantic. Using long-term data, we examined possible direct and indirect ‘bottom-up’ climate effects across four trophic levels: phytoplankton, zooplankton, mid-trophic level fish and seabirds. During the period 1986–2007, although there was no temporal trend in the North Atlantic Oscillation index (NAO), the decadal mean Sea Surface Temperature (SST) in the Celtic Sea increased by 0.66±0.02°C. Despite this, there was only a weak signal of climate change in the Celtic Sea food web. Changes in plankton community structure were found, however this was not related to SST or NAO. A negative relationship occurred between herring abundance (0- and 1-group) and spring SST (0-group: p = 0.02, slope = −0.305±0.125; 1-group: p = 0.04, slope = −0.410±0.193). Seabird demographics showed complex species–specific responses. There was evidence of direct effects of spring NAO (on black-legged kittiwake population growth rate: p = 0.03, slope = 0.0314±0.014) as well as indirect bottom-up effects of lagged spring SST (on razorbill breeding success: p = 0.01, slope = −0.144±0.05). Negative relationships between breeding success and population growth rate of razorbills and common guillemots may be explained by interactions between mid-trophic level fish. Our findings show that the impacts of climate change on the Celtic Sea ecosystem is not as marked as in nearby regions (e.g. the North Sea), emphasizing the need for more research at regional scales. PMID:23091621

  5. Influence of climate change and trophic coupling across four trophic levels in the Celtic Sea.

    Directory of Open Access Journals (Sweden)

    Valentina Lauria

    Full Text Available Climate change has had profound effects upon marine ecosystems, impacting across all trophic levels from plankton to apex predators. Determining the impacts of climate change on marine ecosystems requires understanding the direct effects on all trophic levels as well as indirect effects mediated by trophic coupling. The aim of this study was to investigate the effects of climate change on the pelagic food web in the Celtic Sea, a productive shelf region in the Northeast Atlantic. Using long-term data, we examined possible direct and indirect 'bottom-up' climate effects across four trophic levels: phytoplankton, zooplankton, mid-trophic level fish and seabirds. During the period 1986-2007, although there was no temporal trend in the North Atlantic Oscillation index (NAO, the decadal mean Sea Surface Temperature (SST in the Celtic Sea increased by 0.66 ± 0.02 °C. Despite this, there was only a weak signal of climate change in the Celtic Sea food web. Changes in plankton community structure were found, however this was not related to SST or NAO. A negative relationship occurred between herring abundance (0- and 1-group and spring SST (0-group: p = 0.02, slope = -0.305 ± 0.125; 1-group: p = 0.04, slope = -0.410 ± 0.193. Seabird demographics showed complex species-specific responses. There was evidence of direct effects of spring NAO (on black-legged kittiwake population growth rate: p = 0.03, slope = 0.0314 ± 0.014 as well as indirect bottom-up effects of lagged spring SST (on razorbill breeding success: p = 0.01, slope = -0.144 ± 0.05. Negative relationships between breeding success and population growth rate of razorbills and common guillemots may be explained by interactions between mid-trophic level fish. Our findings show that the impacts of climate change on the Celtic Sea ecosystem is not as marked as in nearby regions (e.g. the North Sea, emphasizing the need for more research at regional scales.

  6. Complexity of plant volatile-mediated interactions beyond the third trophic level

    NARCIS (Netherlands)

    Poelman, E.H.; Kos, M.

    2016-01-01

    Food chains of plant-associated communities typically reach beyond three trophic levels. The predators and parasitoids in the third trophic level are under attack by top predators or parasitised by hyperparasitoids. These higher trophic level organisms respond to plant volatiles in search of their

  7. Trophic levels of fish species of commercial importance in the Colombian Caribbean

    Directory of Open Access Journals (Sweden)

    Camilo B García

    2011-09-01

    Full Text Available Ecological studies on commercial important fish species are of great value to support resource management issues. This study calculated trophic levels of those Colombian Caribbean fish species whose diet has been locally described. Usable diet data of 119 species resulted in 164 trophic level estimates. An ordinary regression model relating trophic level and fish size was formulated. The regression slope was positive and significantly different from zero (p<0.05 suggesting a scaling of trophic level with fish size. Both the list of trophic levels and the regression model should be of help in the formulation of trophic indicators and models of neotropical ecosystems. Rev. Biol. Trop. 59 (3: 1195-1203. Epub 2011 September 01.

  8. Meta-analysis review of fish trophic level at marine protected areas based on stable isotopes data

    Directory of Open Access Journals (Sweden)

    J. J. de LOPE ARIAS

    2016-04-01

    Full Text Available Stable isotopes (δ15N are used to determine trophic level in marine food webs. We assessed if Marine Protected Areas (MPAs affect trophic level of fishes based on stable isotopes on the Western Mediterranean. A total of 22 studies including 600 observations were found and the final dataset consisted of 11 fish species and 146 observations comparing trophic level inside and outside MPAs. The database was analysed by meta-analysis and the covariate selected was the level of protection (inside vs. outside MPAs. The results indicate significant difference between trophic levels inside and outside MPAs. However, results differ from expectations since the trophic level inside was lower than outside MPAs. Three habitats were analysed (coastal lagoons, demersal and littoral and significant differences were found among them. Trophic level was higher in demersal habitats than in coastal lagoons and littoral areas. No significant differences were found in species classified by trophic functional groups. We consider several hypotheses explaining the obtained results linked to protection level of the MPAs, time since protection and MPAs size. We debate the suitability of using the stable isotope (δ15N as direct indicator of trophic level in evaluating MPAs effects on food webs.

  9. Examining predator–prey body size, trophic level and body mass across marine and terrestrial mammals

    Science.gov (United States)

    Tucker, Marlee A.; Rogers, Tracey L.

    2014-01-01

    Predator–prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator–prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator–prey ratio across terrestrial (n = 51) and marine (n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator–prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities. PMID:25377460

  10. Food web analysis reveals effects of pH on mercury bioaccumulation at multiple trophic levels in streams

    International Nuclear Information System (INIS)

    Jardine, Timothy D.; Kidd, Karen A.; O’ Driscoll, Nelson

    2013-01-01

    Highlights: ► We examine biomagnification of Hg through stream food webs using δ15 N. ► Slopes of methyl Hg vs. trophic level were higher than total Hg vs. trophic level. ► Biomagnification from predatory insects to fish was related to pH of the water. ► Biomagnification at lower trophic levels was related to dietary concentrations. ► These trends can explain variation in field-measured Hg in food webs. -- Abstract: Biomagnification processes and the factors that govern them, including those for mercury (Hg), are poorly understood in streams. Total and methyl Hg concentrations and relative trophic position (using δ 15 N) were analyzed in biofilm and invertebrates from 21 streams in New Brunswick, Canada to assess food web biomagnification leading to the common minnow blacknose dace (Rhinichthys atratulus), a species known to have Hg concentrations that are higher in low pH waters. Biomagnification slopes within stream food webs measured using Hg vs. δ 15 N or corresponding trophic levels (TL) differed depending on the chemical species analyzed, with total Hg exhibiting increases of 1.3–2.5 per TL (mean slope of total Hg vs. δ 15 N = 0.14 ± 0.06 S.D., range = 0.06–0.20) and methyl Hg showing a more pronounced increase of 2.8 to 6.0 per TL (mean slope of methyl Hg vs. δ 15 N = 0.30 ± 0.08 S.D., range = 0.22–0.39). While Hg biomagnification slopes through the entire food web (Trophic Magnification Factors, TMFs) were not influenced by water chemistry (pH), dietary concentrations of methyl Hg strongly influenced biomagnification factors (BMFs) for consumer-diet pairs within the food web at lower trophic levels, and BMFs between dace and predatory invertebrates were significantly higher in low pH waters. These analyses, coupled with observations of higher Hg in primary producers in streams with low pH, suggest that pH influences both baseline concentrations and biomagnification of Hg in these systems. Because higher Hg concentrations in the diets

  11. Food web analysis reveals effects of pH on mercury bioaccumulation at multiple trophic levels in streams

    Energy Technology Data Exchange (ETDEWEB)

    Jardine, Timothy D., E-mail: tim.jardine@usask.ca [Canadian Rivers Institute and Department of Biology, University of New Brunswick, Saint John, NB E2L 4L5 (Canada); Kidd, Karen A. [Canadian Rivers Institute and Department of Biology, University of New Brunswick, Saint John, NB E2L 4L5 (Canada); O’ Driscoll, Nelson [Department of Earth and Environmental Sciences, Acadia University, Wolfville, NS B4P 2R6 (Canada)

    2013-05-15

    Highlights: ► We examine biomagnification of Hg through stream food webs using δ15 N. ► Slopes of methyl Hg vs. trophic level were higher than total Hg vs. trophic level. ► Biomagnification from predatory insects to fish was related to pH of the water. ► Biomagnification at lower trophic levels was related to dietary concentrations. ► These trends can explain variation in field-measured Hg in food webs. -- Abstract: Biomagnification processes and the factors that govern them, including those for mercury (Hg), are poorly understood in streams. Total and methyl Hg concentrations and relative trophic position (using δ{sup 15}N) were analyzed in biofilm and invertebrates from 21 streams in New Brunswick, Canada to assess food web biomagnification leading to the common minnow blacknose dace (Rhinichthys atratulus), a species known to have Hg concentrations that are higher in low pH waters. Biomagnification slopes within stream food webs measured using Hg vs. δ{sup 15}N or corresponding trophic levels (TL) differed depending on the chemical species analyzed, with total Hg exhibiting increases of 1.3–2.5 per TL (mean slope of total Hg vs. δ{sup 15}N = 0.14 ± 0.06 S.D., range = 0.06–0.20) and methyl Hg showing a more pronounced increase of 2.8 to 6.0 per TL (mean slope of methyl Hg vs. δ{sup 15}N = 0.30 ± 0.08 S.D., range = 0.22–0.39). While Hg biomagnification slopes through the entire food web (Trophic Magnification Factors, TMFs) were not influenced by water chemistry (pH), dietary concentrations of methyl Hg strongly influenced biomagnification factors (BMFs) for consumer-diet pairs within the food web at lower trophic levels, and BMFs between dace and predatory invertebrates were significantly higher in low pH waters. These analyses, coupled with observations of higher Hg in primary producers in streams with low pH, suggest that pH influences both baseline concentrations and biomagnification of Hg in these systems. Because higher Hg

  12. Examining predator-prey body size, trophic level and body mass across marine and terrestrial mammals.

    Science.gov (United States)

    Tucker, Marlee A; Rogers, Tracey L

    2014-12-22

    Predator-prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator-prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator-prey ratio across terrestrial (n = 51) and marine (n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator-prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  13. Divergent trophic levels in two cryptic sibling bat species.

    Science.gov (United States)

    Siemers, Björn M; Greif, Stefan; Borissov, Ivailo; Voigt-Heucke, Silke L; Voigt, Christian C

    2011-05-01

    Changes in dietary preferences in animal species play a pivotal role in niche specialization. Here, we investigate how divergence of foraging behaviour affects the trophic position of animals and thereby their role for ecosystem processes. As a model, we used two closely related bat species, Myotis myotis and M. blythii oxygnathus, that are morphologically very similar and share the same roosts, but show clear behavioural divergence in habitat selection and foraging. Based on previous dietary studies on synanthropic populations in Central Europe, we hypothesised that M. myotis would mainly prey on predatory arthropods (i.e., secondary consumers) while M. blythii oxygnathus would eat herbivorous insects (i.e., primary consumers). We thus expected that the sibling bats would be at different trophic levels. We first conducted a validation experiment with captive bats in the laboratory and measured isotopic discrimination, i.e., the stepwise enrichment of heavy in relation to light isotopes between consumer and diet, in insectivorous bats for the first time. We then tested our trophic level hypothesis in the field at an ancient site of natural coexistence for the two species (Bulgaria, south-eastern Europe) using stable isotope analyses. As predicted, secondary consumer arthropods (carabid beetles; Coleoptera) were more enriched in (15)N than primary consumer arthropods (tettigoniids; Orthoptera), and accordingly wing tissue of M. myotis was more enriched in (15)N than tissue of M. blythii oxygnathus. According to a Bayesian mixing model, M. blythii oxygnathus indeed fed almost exclusively on primary consumers (98%), while M. myotis ate a mix of secondary (50%), but also, and to a considerable extent, primary consumers (50%). Our study highlights that morphologically almost identical, sympatric sibling species may forage at divergent trophic levels, and, thus may have different effects on ecosystem processes.

  14. Trophic level stability-inducing effects of predaceous early juvenile fish in an estuarine mesocosm study.

    Directory of Open Access Journals (Sweden)

    Ryan J Wasserman

    Full Text Available Classically, estuarine planktonic research has focussed largely on the physico-chemical drivers of community assemblages leaving a paucity of information on important biological interactions.Within the context of trophic cascades, various treatments using in situ mesocosms were established in a closed estuary to highlight the importance of predation in stabilizing estuarine plankton abundances. Through either the removal (filtration or addition of certain planktonic groups, five different trophic systems were established. These treatments contained varied numbers of trophic levels and thus different "predators" at the top of the food chain. The abundances of zooplankton (copepod and polychaete, ciliate, micro-flagellate, nano-flagellate and bacteria were investigated in each treatment, over time. The reference treatment containing apex zooplanktivores (early juvenile mullet and plankton at natural densities mimicked a natural, stable state of an estuary. Proportional variability (PV and coefficient of variation (CV of temporal abundances were calculated for each taxon and showed that apex predators in this experimental ecosystem, when compared to the other systems, induced stability. The presence of these predators therefore had consequences for multiple trophic levels, consistent with trophic cascade theory.PV and CV proved useful indices for comparing stability. Apex predators exerted a stabilizing pressure through feeding on copepods and polychaetes which cascaded through the ciliates, micro-flagellates, nano-flagellates and bacteria. When compared with treatments without apex predators, the role of predation in structuring planktonic communities in closed estuaries was highlighted.

  15. Interannual variability in lower trophic levels on the Alaskan Shelf

    Science.gov (United States)

    Batten, Sonia D.; Raitsos, Dionysios E.; Danielson, Seth; Hopcroft, Russell; Coyle, Kenneth; McQuatters-Gollop, Abigail

    2018-01-01

    This study describes results from the first 16 years of the Continuous Plankton Recorder (CPR) program that has sampled the lower trophic levels (restricted to larger, hard-shelled phytoplankton and robust zooplankton taxa) on the Alaskan shelf. Sampling took place along transects from the open ocean across the shelf (to the entrance to Prince William Sound from 2000 to 2003 and into Cook Inlet from 2004 to 2015) to provide plankton abundance data, spring through autumn of each year. We document interannual variability in concentration and composition of the plankton community of the region over this time period. At least in part and through correlative relationships, this can be attributed to changes in the physical environment, particularly direct and indirect effects of temperature. For example; spring mixed layer depth is shown to influence the timing of the spring diatom peak and warmer years are biased towards smaller copepod species. A significant positive relationship between temperature, diatom abundance and zooplankton biomass existed from 2000 to 2013 but was not present in the warm years of 2014 and 2015. These results suggest that anomalous warming events, such as the "heat wave" of 2014-2015, could fundamentally influence typical lower trophic level patterns, possibly altering trophic interactions.

  16. Effects of dietary nicotine on the development of an insect herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels

    NARCIS (Netherlands)

    Harvey, J.A.; Dam, van N.M.; Witjes, L.M.A.; Soler, R.; Gols, R.

    2007-01-01

    1. Allelochemicals in herbivore diet are known to affect the development of higher trophic levels, such as parasitoids and predators. 2. This study examines how differing levels of nicotine affects the development of a herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels.

  17. Distributions and natural levels of related metals in a trophic pathway

    International Nuclear Information System (INIS)

    Lemons, J.D.

    1976-06-01

    The first objective was to test the hypothesis that metal distributions and trends in organisms are, in part, a function of metal positions in the periodic table in unpolluted ecosystems. The data have shown that large soil crustal abundance differences of related elements (e.g. alkali metals) are proportionately approximated in higher organisms. Concentration factors for related nutritious and nonessential and toxic metals were determined along a trophic pathway. When the concentration factors were reported as the concentration of a particular metal by itself, all metal concentrations increased along the trophic pathway. The second objective of this study was to test the hypothesis that distributions and natural levels of chemically related nonessential and toxic metals can better be known when the metals are reported as a ratio, in ash, of the nonessential or toxic metal to its chemically related nutritious metal (e.g. strontium/calcium) as the metals are transferred through trophic pathways. The data have shown that when this method of reporting metal abundances in trophic levels is used, nonessential and toxic metals are discriminated against, relative to their chemically related nutritious metal, as the metals are transferred through the trophic pathway levels. The third objective was designed to test the hypothesis that surface deposition of toxic metals upon plants influences the trends of metal abundances through trophic pathways. This study indicates that metal pollution in the form of deposition upon plant surfaces bypasses the discrimination mechanisms in plants, and consequently elevates the total body burden in herbivores. It is likely that there is no herbivore defense for this type of metal exposure, because herbivores have probably come to rely, in part, upon the discriminatory mechanism of plants throughout the course of evolutionary history to keep toxic metal burdens low

  18. PCBs and DDE, but not PBDEs, increase with trophic level and marine input in nestling bald eagles

    International Nuclear Information System (INIS)

    Hamish Elliott, Kyle; Cesh, Lillian S.; Dooley, Jessica A.; Letcher, Robert J.; Elliott, John E.

    2009-01-01

    Concentrations of persistent contaminants often vary widely among individuals within a population. We hypothesized that such variation was caused mainly by differences in diet (biomagnification) and in coastal systems by the tendency of marine systems to act as contaminant sinks. We examined the relationship between contaminant concentrations and stable isotope ratios in nestling plasma from an apex predator with a particularly broad diet. Our study included freshwater, estuarine, inshore and pelagic breeding sites. Bald eagles (Haliaeetus leucocephalus) at the pelagic marine sites showed high trophic level and marine input, eagles at the freshwater sites showed low trophic level and marine input, and eagles at the estuarine and inshore marine sites had intermediate values. The relationship between trophic level and marine input may reflect longer food chains in pelagic compared to terrestrial ecosystems. ΣPCBs and DDE concentrations generally increased with trophic level and marine input, with the exception of the freshwater sites, while ΣPBDEs, hydroxylated-PBDEs and hydroxylated-PCBs increased with marine input, but were independent of trophic level. The relationships for ΣPCBs and DDE were often slightly stronger with marine input than trophic level, suggesting that oceanographic processes may be more important than trophic level. At freshwater locations, spatial variation may be more important than trophic level due to the heterogeneity of contaminant profiles between feeding locations (lakes, rivers, agricultural fields). Adults had similar isotopic composition to their chicks but higher contamination. Based on nests where prey composition was determined independently, isotopic enrichment values for nestling plasma were 1.6 ± 0.1 (δ 15 N) and - 0.4 ±0.2 (δ 13 C). We conclude that trophic level and marine influence are significant factors influencing PCB and DDE concentrations in eagles. However, trophic level in particular did not influence PBDEs

  19. Fate of ethinylestradiol in the aquatic environment and the associated effects on organisms of different trophic levels

    OpenAIRE

    Maes, Hanna

    2011-01-01

    The accumulation kinetics of an important, highly effective, and persistent xeno-estrogen, 17alpha-ethinylestradiol (EE2), in the aquatic environment were investigated in indicator species representing the different trophic levels of an ecosystem: a primary producer (Desmodesmus suspicatus), a primary consumer of the water phase (Daphnia magna) and one of the sediment (Chironomus riparius), and a secondary consumer (Danio rerio). Algae highly concentrated 14C-EE2 (72 h Calgae/Cwater: 2200 L/k...

  20. Biodiversity enhances ecosystem multifunctionality across trophic levels and habitats

    Science.gov (United States)

    Lefcheck, Jonathan S.; Byrnes, Jarrett E. K.; Isbell, Forest; Gamfeldt, Lars; Griffin, John N.; Eisenhauer, Nico; Hensel, Marc J. S.; Hector, Andy; Cardinale, Bradley J.; Duffy, J. Emmett

    2015-01-01

    The importance of biodiversity for the integrated functioning of ecosystems remains unclear because most evidence comes from analyses of biodiversity's effect on individual functions. Here we show that the effects of biodiversity on ecosystem function become more important as more functions are considered. We present the first systematic investigation of biodiversity's effect on ecosystem multifunctionality across multiple taxa, trophic levels and habitats using a comprehensive database of 94 manipulations of species richness. We show that species-rich communities maintained multiple functions at higher levels than depauperate ones. These effects were stronger for herbivore biodiversity than for plant biodiversity, and were remarkably consistent across aquatic and terrestrial habitats. Despite observed tradeoffs, the overall effect of biodiversity on multifunctionality grew stronger as more functions were considered. These results indicate that prior research has underestimated the importance of biodiversity for ecosystem functioning by focusing on individual functions and taxonomic groups. PMID:25907115

  1. Long-chain omega-3 from low-trophic-level fish provides value to farmed seafood.

    Science.gov (United States)

    Bibus, Douglas M

    2015-03-01

    Low-trophic-level fish are a crucial source of long-chain (LC) omega-3 fatty acids for farmed fish and humans. Many farm-raised fish species have a clear need for these nutrients. Farmed fish deposit the LC omega-3s in their flesh and transfer them up the food chain. However, the content of LC omega-3s in farm-raised seafood continues to decline, while the content of shorter-chain plant-sourced omega-3s, and pro-inflammtory omega-6s continue to increase. This reduces its nutritional worth. The value of low-trophic-level fish is often viewed merely as its price at the dock. Some reports and metrics steer public attention towards the mass balance between quantities of low-trophic-level fish and farmed seafood. However, the the nutritional value of seafood is more important than its mere quantities. The role of low-trophic-level fish in human nutrition, health, and wellbeing is a fundamental component of its economic value to society.

  2. Responses of trophic structure and zooplankton community to salinity and temperature in Tibetan lakes: Implication for the effect of climate warming.

    Science.gov (United States)

    Lin, Qiuqi; Xu, Lei; Hou, Juzhi; Liu, Zhengwen; Jeppesen, Erik; Han, Bo-Ping

    2017-11-01

    Warming has pronounced effects on lake ecosystems, either directly by increased temperatures or indirectly by a change in salinity. We investigated the current status of zooplankton communities and trophic structure in 45 Tibetan lakes along a 2300 m altitude and a 76 g/l salinity gradient. Freshwater to hyposaline lakes mainly had three trophic levels: phytoplankton, small zooplankton and fish/Gammarus, while mesosaline to hypersaline lakes only had two: phytoplankton and large zooplankton. Zooplankton species richness declined significantly with salinity, but did not relate with temperature. Furthermore, the decline in species richness with salinity in lakes with two trophic levels was much less abrupt than in lakes with three trophic levels. The structural variation of the zooplankton community depended on the length of the food chain, and was significantly explained by salinity as the critical environmental variable. The zooplankton community shifted from dominance of copepods and small cladoceran species in the lakes with low salinity and three trophic levels to large saline filter-feeding phyllopod species in those lakes with high salinity and two trophic levels. The zooplankton to phytoplankton biomass ratio was positively related with temperature in two-trophic-level systems and vice versa in three-trophic-level systems. As the Tibetan Plateau is warming about three times faster than the global average, our results imply that warming could have a considerable impact on the structure and function of Tibetan lake ecosystems, either via indirect effects of salinization/desalinization on species richness, composition and trophic structure or through direct effects of water temperature on trophic interactions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Ecosystem regime shifts disrupt trophic structure.

    Science.gov (United States)

    Hempson, Tessa N; Graham, Nicholas A J; MacNeil, M Aaron; Hoey, Andrew S; Wilson, Shaun K

    2018-01-01

    Regime shifts between alternative stable ecosystem states are becoming commonplace due to the combined effects of local stressors and global climate change. Alternative states are characterized as substantially different in form and function from pre-disturbance states, disrupting the delivery of ecosystem services and functions. On coral reefs, regime shifts are typically characterized by a change in the benthic composition from coral to macroalgal dominance. Such fundamental shifts in the benthos are anticipated to impact associated fish communities that are reliant on the reef for food and shelter, yet there is limited understanding of how regime shifts propagate through the fish community over time, relative to initial or recovery conditions. This study addresses this knowledge gap using long-term data of coral reef regime shifts and recovery on Seychelles reefs following the 1998 mass bleaching event. It shows how trophic structure of the reef fish community becomes increasingly dissimilar between alternative reef ecosystem states (regime-shifted vs. recovering) with time since disturbance. Regime-shifted reefs developed a concave trophic structure, with increased biomass in base trophic levels as herbivorous species benefitted from increased algal resources. Mid trophic level species, including specialists such as corallivores, declined with loss of coral habitat, while biomass was retained in upper trophic levels by large-bodied, generalist invertivores. Recovering reefs also experienced an initial decline in mid trophic level biomass, but moved toward a bottom-heavy pyramid shape, with a wide range of feeding groups (e.g., planktivores, corallivores, omnivores) represented at mid trophic levels. Given the importance of coral reef fishes in maintaining the ecological function of coral reef ecosystems and their associated fisheries, understanding the effects of regime shifts on these communities is essential to inform decisions that enhance ecological

  4. Phenological sensitivity to climate across taxa and trophic levels

    DEFF Research Database (Denmark)

    Thackeray, Stephen J.; Henrys, Peter; Hemming, Deborah

    2016-01-01

    Differences in phenological responses to climate change among species can desynchronise ecological interactions and thereby threaten ecosystem function. To assess these threats, we must quantify the relative impact of climate change on species at different trophic levels. Here, we apply a Climate...

  5. Comparison of contaminants from different trophic levels and ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Dietz, R.; Riget, F. [Department of Arctic Environment, Ministry of Environment and Energy, National Environmental Research Institute, Tagensvej 135, 4 floor, DK-2200 Copenhagen (Denmark); Cleemann, M. [Department of Environmental Chemistry, Ministry of Environment and Energy, National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Aarkrog, A. [Risoe National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Johansen, P. [Department of Arctic Environment, Ministry of Environment and Energy, National Environmental Research Institute, Tagensvej 135, 4 floor, DK-2200 Copenhagen (Denmark); Hansen, J.C. [Risoe National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)

    2000-01-17

    The present paper provides an overview of the priority contaminants and media from the Greenland part of the Arctic Monitoring and Assessment Program. Levels and accumulation patterns of heavy metals, POPs and a radionuclide (137Cs) are compared from the terrestrial, freshwater and marine ecosystems. Of the nine compounds presented, seven (Cd, Hg, Se, {sigma}PCB, {sigma}DDT, {sigma}HCH, HCB) increased in concentration towards higher trophic levels. For these contaminants the concentrations in soil and aquatic sediment were in the same order of magnitude, whereas the concentrations in marine biota were higher than found in the freshwater and terrestrial ecosystems probably due to the presence of longer food chains. Pb and 137Cs showed the reverse pattern compared with the other compounds. The concentrations in soil and aquatic sediments decreased in the order terrestrial, freshwater and marine ecosystems, which was reflected in the biota as well. Reindeer had similar or lower levels of Pb and 137Cs than lichens. Levels of Pb and 137Cs in marine biota did not show the same clear increase towards higher trophic as found for the other analysed compounds. Greenland Inuit contains considerably less mercury but higher levels of {sigma}PCB, {sigma}DDT and HCB than other Arctic marine top consumers.

  6. Effects of trophic skewing of species richness on ecosystem functioning in a diverse marine community.

    Directory of Open Access Journals (Sweden)

    Pamela L Reynolds

    Full Text Available Widespread overharvesting of top consumers of the world's ecosystems has "skewed" food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs, while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms generally emerged in communities with greater predator to prey richness (the more top-rich food webs. These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions.

  7. Evaluation of the Trophic Level of Kune and Vain Lagoons in Albania, Using Phytoplankton as a Bioindicator

    Directory of Open Access Journals (Sweden)

    Anni Koci Kallfa

    2014-03-01

    Full Text Available Concentration of chlorophyll is an adequate parameter for assessing the trophic state of lagoon ecosystems. Objectives of this study are: selection of a system of bioindicators to enable a good qualitative evaluation of the trophic state of the lagoons and their dynamics; evaluation of seasonal water quality variability and comparison between lagoons. The trophic state of the lagoons is analysed every month over the year. Water samples are retrieved at four different sites (exact coordinates each month, sites that are representative of different water circulation systems at each lagoon. The trophic level in the respective lagoons is thus assessed through selection of an adequate system of bioindicators, in order to observe the oscillations of the amount of chlorophyll and therefore to determine the level of eutrophication. Based on the above parameters, the comparison of the trophic state in these two lagoons has shown that they have different trophic states.

  8. Predator-prey dynamics driven by feedback between functionally diverse trophic levels.

    Directory of Open Access Journals (Sweden)

    Katrin Tirok

    Full Text Available Neglecting the naturally existing functional diversity of communities and the resulting potential to respond to altered conditions may strongly reduce the realism and predictive power of ecological models. We therefore propose and study a predator-prey model that describes mutual feedback via species shifts in both predator and prey, using a dynamic trait approach. Species compositions of the two trophic levels were described by mean functional traits--prey edibility and predator food-selectivity--and functional diversities by the variances. Altered edibility triggered shifts in food-selectivity so that consumers continuously respond to the present prey composition, and vice versa. This trait-mediated feedback mechanism resulted in a complex dynamic behavior with ongoing oscillations in the mean trait values, reflecting continuous reorganization of the trophic levels. The feedback was only possible if sufficient functional diversity was present in both trophic levels. Functional diversity was internally maintained on the prey level as no niche existed in our system, which was ideal under any composition of the predator level due to the trade-offs between edibility, growth and carrying capacity. The predators were only subject to one trade-off between food-selectivity and grazing ability and in the absence of immigration, one predator type became abundant, i.e., functional diversity declined to zero. In the lack of functional diversity the system showed the same dynamics as conventional models of predator-prey interactions ignoring the potential for shifts in species composition. This way, our study identified the crucial role of trade-offs and their shape in physiological and ecological traits for preserving diversity.

  9. Trophic level responses differ as climate warms in Ireland

    Science.gov (United States)

    Donnelly, Alison; Yu, Rong; Liu, Lingling

    2015-08-01

    Effective ecosystem functioning relies on successful species interaction. However, this delicate balance may be disrupted if species do not respond to environmental change at a similar rate. Here we examine trends in the timing of spring phenophases of groups of species occupying three trophic levels as a potential indicator of ecosystem response to climate warming in Ireland. The data sets were of varying length (1976-2009) and from varying locations: (1) timing of leaf unfolding and May Shoot of a range of broadleaf and conifer tree species, (2) first appearance dates of a range of moth species, and (3) first arrival dates of a range of spring migrant birds. All three groups revealed a statistically significant ( Pphenology that was driven by rising spring temperature ( P<0.05; 0.45 °C /decade). However, the rate of advance was greater for moths (1.8 days/year), followed by birds (0.37 days/year) and trees (0.29 days/year). In addition, the length of time between (1) moth emergence and leaf unfolding and (2) moth emergence and bird arrival decreased significantly ( P<0.05 and P<0.001, respectively), indicating a decrease in the timing between food supply and demand. These differing trophic level response rates demonstrate the potential for a mismatch in the timing of interdependent phenophases as temperatures rise. Even though these data were not specifically collected to examine climate warming impacts, we conclude that such data may be used as an early warning indicator and as a means to monitor the potential for future ecosystem disruption to occur as climate warms.

  10. First direct evidence of a vertebrate three-level trophic chain in the fossil record.

    Science.gov (United States)

    Kriwet, Jürgen; Witzmann, Florian; Klug, Stefanie; Heidtke, Ulrich H J

    2008-01-22

    We describe the first known occurrence of a Permian shark specimen preserving two temnospondyl amphibians in its digestive tract as well as the remains of an acanthodian fish, which was ingested by one of the temnospondyls. This exceptional find provides for the first time direct evidence of a vertebrate three-level food chain in the fossil record with the simultaneous preservation of three trophic levels. Our analysis shows that small-sized Lower Permian xenacanthid sharks of the genus Triodus preyed on larval piscivorous amphibians. The recorded trophic interaction can be explained by the adaptation of certain xenacanthids to fully freshwater environments and the fact that in these same environments, large temnospondyls occupied the niche of modern crocodiles. This unique faunal association has not been documented after the Permian and Triassic. Therefore, this Palaeozoic three-level food chain provides strong and independent support for changes in aquatic trophic chain structures through time.

  11. Application of indicator kriging to the complementary use of bioindicators at three trophic levels

    International Nuclear Information System (INIS)

    Figueira, Rui; Tavares, Paula C.; Palma, Luis; Beja, Pedro; Sergio, Cecilia

    2009-01-01

    The use of biological indicators is widespread in environmental monitoring, although it has long been recognised that each bioindicator is generally associated with a range of potential limitations and shortcomings. To circumvent this problem, this study adopted the complementary use of bioindicators representing different trophic levels and providing different type of information, in an innovative approach to integrate knowledge and to estimate the overall health state of ecosystems. The approach is illustrated using mercury contamination in primary producers (mosses), primary consumers (domestic pigeons and red-legged partridges) and top predators (Bonelli's eagles) in southern Portugal. Indicator kriging geostatistics was used to identify the areas where mercury concentration was higher than the median for each species, and to produce an index that combines mercury contamination across trophic levels. Spatial patterns of mercury contamination were consistent across species. The combined index provided a new level of information useful in incorporating measures of overall environmental contamination into pollution studies. - Mercury levels in bioindicators at three trophic levels were combined using geostatistics to build an integrated environmental contamination index.

  12. Application of indicator kriging to the complementary use of bioindicators at three trophic levels

    Energy Technology Data Exchange (ETDEWEB)

    Figueira, Rui, E-mail: rui.figueira@iict.p [Jardim Botanico Tropical, Instituto de Investigacao Cientifica Tropical, Trav. Conde da Ribeira, 9, 1300-142 Lisboa (Portugal); CERENA, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Tavares, Paula C. [CVRM-Geo-Systems Centre, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Palma, Luis [CCMAR, Universidade do Algarve, FCMA, Campus de Gambelas, 8005-139 Faro (Portugal); Beja, Pedro [ERENA, Ordenamento e Gestao de Recursos Naturais, Rua Robalo Gouveia, 1-1A, 1900-392 Lisboa (Portugal); CIBIO, Centro de Investigacao em Biodiversidade e Recursos Geneticos, Campus Agrario de Vairao, Universidade do Porto, Vairao (Portugal); Sergio, Cecilia [Jardim Botanico, Museu Nacional de Historia Natural, Universidade de Lisboa, R. Escola Politecnica, 58, 1250-102 Lisboa (Portugal); CBA, Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, Edificio C2, 1749-016 Lisboa (Portugal)

    2009-10-15

    The use of biological indicators is widespread in environmental monitoring, although it has long been recognised that each bioindicator is generally associated with a range of potential limitations and shortcomings. To circumvent this problem, this study adopted the complementary use of bioindicators representing different trophic levels and providing different type of information, in an innovative approach to integrate knowledge and to estimate the overall health state of ecosystems. The approach is illustrated using mercury contamination in primary producers (mosses), primary consumers (domestic pigeons and red-legged partridges) and top predators (Bonelli's eagles) in southern Portugal. Indicator kriging geostatistics was used to identify the areas where mercury concentration was higher than the median for each species, and to produce an index that combines mercury contamination across trophic levels. Spatial patterns of mercury contamination were consistent across species. The combined index provided a new level of information useful in incorporating measures of overall environmental contamination into pollution studies. - Mercury levels in bioindicators at three trophic levels were combined using geostatistics to build an integrated environmental contamination index.

  13. Trophic calculations reveal the mechanism of population-level variation in mercury concentrations between marine ecosystems: Case studies of two polar seabirds

    International Nuclear Information System (INIS)

    Brasso, Rebecka L.; Polito, Michael J.

    2013-01-01

    Highlights: • Ecosystem-specific baseline and consumer δ 15 N paired for population-specific trophic level. • Source of population-level variation in mercury exposure identified in two seabirds. • High mercury and trophic position suggests trophic driver of population-level variation. • Trophic similarities, differing mercury reveals geographic differences in bioavailability. -- Abstract: The incorporation of quantitative trophic level analysis in ecotoxicological studies provides explanatory power to identify the factors, trophic or environmental, driving population-level variation in mercury exposure at large geographic scales. In the Antarctic marine ecosystem, mercury concentrations and stable isotope values in Adélie penguins (Pygoscelis adeliae) were compared between the Antarctic Peninsula and the Ross Sea. Correcting tissue δ 15 N values for baseline δ 15 N values revealed population-level differences in trophic position which contributes to differences in mercury. Data from Thick-billed murres (Uria lomvia) were synthesized from published values from Baffin Bay and Svalbard to demonstrate the utility of baseline δ 15 N values in identifying differences in environmental mercury exposure independent of diet. Here, we demonstrate the importance of calculating population-specific trophic level data to uncover the source of variation in mercury concentrations between geographically distinct populations of marine predators

  14. The interacting effects of temperature and food chain length on trophic abundance and ecosystem function.

    Science.gov (United States)

    Beveridge, Oliver S; Humphries, Stuart; Petchey, Owen L

    2010-05-01

    1. While much is known about the independent effects of trophic structure and temperature on density and ecosystem processes, less is known about the interaction(s) between the two. 2. We manipulated the temperature of laboratory-based bacteria-protist communities that contained communities with one, two, or three trophic levels, and recorded species' densities and bacterial decomposition. 3. Temperature, food chain length and their interaction produced significant responses in microbial density and bacterial decomposition. Prey and resource density expressed different patterns of temperature dependency during different phases of population dynamics. The addition of a predator altered the temperature-density relationship of prey, from a unimodal trend to a negative one. Bacterial decomposition was greatest in the presence of consumers at higher temperatures. 4. These results are qualitatively consistent with a recent model of direct and indirect temperature effects on resource-consumer population dynamics. Results highlight and reinforce the importance of indirect effects of temperature mediated through trophic interactions. Understanding and predicting the consequences of environmental change will require that indirect effects, trophic structure, and individual species' tolerances be incorporated into theory and models.

  15. Assessing mesozooplankton trophic levels in the Baltic Sea and North Sea: A stable isotope study

    OpenAIRE

    Agurto, Cristian

    2007-01-01

    For decades, ecologists have studied trophic interaction in aquatic systems, and described the food web structure of dominant ecological groups based on gut content analyses. The conception of these interactions may, however, be biased by the lack of couplings to the microbial food web and direct errors in diet analyses (e.g. differences in digestion rate between food types). In this thesis, I examined the planktonic food web by analyzing the trophic structure (i.e. trophic levels) with an al...

  16. Tri-trophic insecticidal effects of African plants against cabbage pests.

    Directory of Open Access Journals (Sweden)

    Blankson W Amoabeng

    Full Text Available Botanical insecticides are increasingly attracting research attention as they offer novel modes of action that may provide effective control of pests that have already developed resistance to conventional insecticides. They potentially offer cost-effective pest control to smallholder farmers in developing countries if highly active extracts can be prepared simply from readily available plants. Field cage and open field experiments were conducted to evaluate the insecticidal potential of nine common Ghanaian plants: goat weed, Ageratum conyzoides (Asteraceae, Siam weed, Chromolaena odorata (Asteraceae, Cinderella weed, Synedrella nodiflora (Asteraceae, chili pepper, Capsicum frutescens (Solanaceae, tobacco, Nicotiana tabacum (Solanaceae cassia, Cassia sophera (Leguminosae, physic nut, Jatropha curcas (Euphorbiaceae, castor oil plant, Ricinus communis (Euphorbiaceae and basil, Ocimum gratissimum (Lamiaceae. In field cage experiments, simple detergent and water extracts of all botanical treatments gave control of cabbage aphid, Brevicoryne brassicae and diamondback moth, Plutella xylostella, equivalent to the synthetic insecticide Attack® (emamectin benzoate and superior to water or detergent solution. In open field experiments in the major and minor rainy seasons using a sub-set of plant extracts (A. conyzoides, C. odorata, S. nodiflora, N. tabacum and R. communis, all controlled B. brassicae and P. xylostella more effectively than water control and comparably with or better than Attack®. Botanical and water control treatments were more benign to third trophic level predators than Attack®. Effects cascaded to the first trophic level with all botanical treatments giving cabbage head weights, comparable to Attack® in the minor season. In the major season, R. communis and A conyzoides treatment gave lower head yields than Attack® but the remaining botanicals were equivalent or superior to this synthetic insecticide. Simply-prepared extracts from

  17. Tri-trophic insecticidal effects of African plants against cabbage pests.

    Science.gov (United States)

    Amoabeng, Blankson W; Gurr, Geoff M; Gitau, Catherine W; Nicol, Helen I; Munyakazi, Louis; Stevenson, Phil C

    2013-01-01

    Botanical insecticides are increasingly attracting research attention as they offer novel modes of action that may provide effective control of pests that have already developed resistance to conventional insecticides. They potentially offer cost-effective pest control to smallholder farmers in developing countries if highly active extracts can be prepared simply from readily available plants. Field cage and open field experiments were conducted to evaluate the insecticidal potential of nine common Ghanaian plants: goat weed, Ageratum conyzoides (Asteraceae), Siam weed, Chromolaena odorata (Asteraceae), Cinderella weed, Synedrella nodiflora (Asteraceae), chili pepper, Capsicum frutescens (Solanaceae), tobacco, Nicotiana tabacum (Solanaceae) cassia, Cassia sophera (Leguminosae), physic nut, Jatropha curcas (Euphorbiaceae), castor oil plant, Ricinus communis (Euphorbiaceae) and basil, Ocimum gratissimum (Lamiaceae). In field cage experiments, simple detergent and water extracts of all botanical treatments gave control of cabbage aphid, Brevicoryne brassicae and diamondback moth, Plutella xylostella, equivalent to the synthetic insecticide Attack® (emamectin benzoate) and superior to water or detergent solution. In open field experiments in the major and minor rainy seasons using a sub-set of plant extracts (A. conyzoides, C. odorata, S. nodiflora, N. tabacum and R. communis), all controlled B. brassicae and P. xylostella more effectively than water control and comparably with or better than Attack®. Botanical and water control treatments were more benign to third trophic level predators than Attack®. Effects cascaded to the first trophic level with all botanical treatments giving cabbage head weights, comparable to Attack® in the minor season. In the major season, R. communis and A conyzoides treatment gave lower head yields than Attack® but the remaining botanicals were equivalent or superior to this synthetic insecticide. Simply-prepared extracts from readily

  18. Tri-Trophic Insecticidal Effects of African Plants against Cabbage Pests

    Science.gov (United States)

    Amoabeng, Blankson W.; Gurr, Geoff M.; Gitau, Catherine W.; Nicol, Helen I.; Stevenson, Phil C.

    2013-01-01

    Botanical insecticides are increasingly attracting research attention as they offer novel modes of action that may provide effective control of pests that have already developed resistance to conventional insecticides. They potentially offer cost-effective pest control to smallholder farmers in developing countries if highly active extracts can be prepared simply from readily available plants. Field cage and open field experiments were conducted to evaluate the insecticidal potential of nine common Ghanaian plants: goat weed, Ageratum conyzoides (Asteraceae), Siam weed, Chromolaena odorata (Asteraceae), Cinderella weed, Synedrella nodiflora (Asteraceae), chili pepper, Capsicum frutescens (Solanaceae), tobacco, Nicotiana tabacum (Solanaceae) cassia, Cassia sophera (Leguminosae), physic nut, Jatropha curcas (Euphorbiaceae), castor oil plant, Ricinus communis (Euphorbiaceae) and basil, Ocimum gratissimum (Lamiaceae). In field cage experiments, simple detergent and water extracts of all botanical treatments gave control of cabbage aphid, Brevicoryne brassicae and diamondback moth, Plutella xylostella, equivalent to the synthetic insecticide Attack® (emamectin benzoate) and superior to water or detergent solution. In open field experiments in the major and minor rainy seasons using a sub-set of plant extracts (A. conyzoides, C. odorata, S. nodiflora, N. tabacum and R. communis), all controlled B. brassicae and P. xylostella more effectively than water control and comparably with or better than Attack®. Botanical and water control treatments were more benign to third trophic level predators than Attack®. Effects cascaded to the first trophic level with all botanical treatments giving cabbage head weights, comparable to Attack® in the minor season. In the major season, R. communis and A conyzoides treatment gave lower head yields than Attack® but the remaining botanicals were equivalent or superior to this synthetic insecticide. Simply-prepared extracts from readily

  19. Incorporating anthropogenic effects into trophic ecology: predator–prey interactions in a human-dominated landscape

    Science.gov (United States)

    Dorresteijn, Ine; Schultner, Jannik; Nimmo, Dale G.; Fischer, Joern; Hanspach, Jan; Kuemmerle, Tobias; Kehoe, Laura; Ritchie, Euan G.

    2015-01-01

    Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface. PMID:26336169

  20. Do stage-specific functional responses of consumers dampen the effects of subsidies on trophic cascades in streams?

    Science.gov (United States)

    Sato, Takuya; Watanabe, Katsutoshi

    2014-07-01

    Resource subsidies often weaken trophic cascades in recipient communities via consumers' functional response to the subsidies. Consumer populations are commonly stage-structured and may respond to the subsidies differently among the stages yet less is known about how this might impact the subsidy effects on the strength of trophic cascades in recipient systems. We show here, using a large-scale field experiment, that the stage structure of a recipient consumer would dampen the effects of terrestrial invertebrate subsidies on the strength of trophic cascade in streams. When a high input rate of the terrestrial invertebrates was available, both large and small fish stages switched their diet to the terrestrial subsidy, which weakened the trophic cascade in streams. However, when the input rate of the terrestrial invertebrates was at a moderate level, the terrestrial subsidy did not weaken the trophic cascade. This discrepancy was likely due to small fish stages being competitively excluded from feeding on the subsidy by larger stages of fish and primarily foraging on benthic invertebrates under the moderate input level. Although previous studies using single fish stages have clearly demonstrated that the terrestrial invertebrate input equivalent to our moderate input rate weakened the trophic cascade in streams, this subsidy effect might be overestimated given small fish stage may not switch their diet to the subsidy under competition with large fish stage. Given the ubiquity of consumer stage structure and interaction among consumer stages, the effects we saw might be widespread in nature, requiring future studies that explicitly involve consumer's stage structure into community ecology. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

  1. Effects of chemical elements in the trophic levels of natural salt marshes.

    Science.gov (United States)

    Kamiński, Piotr; Barczak, Tadeusz; Bennewicz, Janina; Jerzak, Leszek; Bogdzińska, Maria; Aleksandrowicz, Oleg; Koim-Puchowska, Beata; Szady-Grad, Małgorzata; Klawe, Jacek J; Woźniak, Alina

    2016-06-01

    The relationships between the bioaccumulation of Na, K, Ca, Mg, Fe, Zn, Cu, Mn, Co, Cd, and Pb, acidity (pH), salinity (Ec), and organic matter content within trophic levels (water-soil-plants-invertebrates) were studied in saline environments in Poland. Environments included sodium manufactures, wastes utilization areas, dumping grounds, and agriculture cultivation, where disturbed Ca, Mg, and Fe exist and the impact of Cd and Pb is high. We found Zn, Cu, Mn, Co, and Cd accumulation in the leaves of plants and in invertebrates. Our aim was to determine the selectivity exhibited by soil for nutrients and heavy metals and to estimate whether it is important in elucidating how these metals are available for plant/animal uptake in addition to their mobility and stability within soils. We examined four ecological plant groups: trees, shrubs, minor green plants, and water macrophytes. Among invertebrates, we sampled breastplates Malacostraca, small arachnids Arachnida, diplopods Diplopoda, small insects Insecta, and snails Gastropoda. A higher level of chemical elements was found in saline polluted areas (sodium manufactures and anthropogenic sites). Soil acidity and salinity determined the bioaccumulation of free radicals in the trophic levels measured. A pH decrease caused Zn and Cd to increase in sodium manufactures and an increase in Ca, Zn, Cu, Cd, and Pb in the anthropogenic sites. pH increase also caused Na, Mg, and Fe to increase in sodium manufactures and an increase in Na, Fe, Mn, and Co in the anthropogenic sites. There was a significant correlation between these chemical elements and Ec in soils. We found significant relationships between pH and Ec, which were positive in saline areas of sodium manufactures and negative in the anthropogenic and control sites. These dependencies testify that the measurement of the selectivity of cations and their fluctuation in soils provide essential information on the affinity and binding strength in these environments. The

  2. Comparison of contaminants from different trophic levels and ecosystems

    DEFF Research Database (Denmark)

    Dietz, R.; Riget, F.; Cleemann, M.

    2000-01-01

    The present paper provides an overview of the priority contaminants and media from the Greenland part of the Arctic Monitoring and Assessment Program. Levels and accumulation patterns of heavy metals, POPs and a radionuclide (Cs-137) are compared from the terrestrial, freshwater and marine...... ecosystems. Of the nine compounds presented, seven (Cd, Hg, Se, Sigma PCB, Sigma DDT, Sigma HCH, HCB) increased in concentration towards higher trophic levels. For these contaminants the concentrations in soil and aquatic sediment were in the same order of magnitude, whereas the concentrations in marine...

  3. Ecosystem Responses To Plant Phenology Across Scales And Trophic Levels

    Science.gov (United States)

    Stoner, D.; Sexton, J. O.; Nagol, J. R.; Ironside, K.; Choate, D.; Longshore, K.; Edwards, T., Jr.

    2015-12-01

    Plant phenology in arid and semi-arid ecoregions is constrained by water availability and governs the life history characteristics of primary and secondary consumers. We related the behavior, demography, and distribution of mammalian herbivores and their principal predator to remotely sensed vegetation and climatological indices across the western United States for the period 2000-2014. Across scales, terrain and topographic position moderates the effects of climatological drought on primary productivity, resulting in differential susceptibility among plant functional types to water stress. At broad scales, herbivores tie parturition to moist sites during the period of maximum increase in local forage production. Consequently, juvenile mortality is highest in regions of extreme phenological variability. Although decoupled from primary production by one or more trophic levels, carnivore home range size and density is negatively correlated to plant productivity and growing season length. At the finest scales, predation influences the behavior of herbivore prey through compromised habitat selection, in which maternal females trade nutritional benefits of high plant biomass for reduced mortality risk associated with increased visibility. Climate projections for the western United States predict warming combined with shifts in the timing and form of precipitation. Our analyses suggest that these changes will propagate through trophic levels as increased phenological variability and shifts in plant distributions, larger consumer home ranges, altered migration behavior, and generally higher volatility in wildlife populations. Combined with expansion and intensification of human land use across the region, these changes will likely have economic implications stemming from increased human-wildlife conflict (e.g., crop damage, vehicle collisions) and changes in wildlife-related tourism.

  4. Effects of trophic level and metamorphosis on discrimination of hydrogen isotopes in a plant-herbivore system

    Science.gov (United States)

    Peters, Jacob M.; Wolf, Nathan; Stricker, Craig A.; Collier, Timothy R.; Martinez del Rio, Carlos

    2012-01-01

    The use of stable isotopes in ecological studies requires that we know the magnitude of discrimination factors between consumer and element sources. The causes of variation in discrimination factors for carbon and nitrogen have been relatively well studied. In contrast, the discrimination factors for hydrogen have rarely been measured. We grew cabbage looper caterpillars (Trichoplusia ni) on cabbage (Brassica oleracea) plants irrigated with four treatments of deuterium-enriched water (δD = -131, -88, -48, and -2‰, respectively), allowing some of them to reach adulthood as moths. Tissue δD values of plants, caterpillars, and moths were linearly correlated with the isotopic composition of irrigation water. However, the slope of these relationships was less than 1, and hence, discrimination factors depended on the δD value of irrigation water. We hypothesize that this dependence is an artifact of growing plants in an environment with a common atmospheric δD value. Both caterpillars and moths were significantly enriched in deuterium relative to plants by ~45‰ and 23‰ respectively, but the moths had lower tissue to plant discrimination factors than did the caterpillars. If the trophic enrichment documented here is universal, δD values must be accounted for in geographic assignment studies. The isotopic value of carbon was transferred more or less faithfully across trophic levels, but δ15N values increased from plants to insects and we observed significant non-trophic 15N enrichment in the metamorphosis from larvae to adult.

  5. Climate change and unequal phenological changes across four trophic levels: constraints or adaptations?

    Science.gov (United States)

    Both, Christiaan; van Asch, Margriet; Bijlsma, Rob G; van den Burg, Arnold B; Visser, Marcel E

    2009-01-01

    1. Climate change has been shown to affect the phenology of many organisms, but interestingly these shifts are often unequal across trophic levels, causing a mismatch between the phenology of organisms and their food. 2. We consider two alternative hypotheses: consumers are constrained to adjust sufficiently to the lower trophic level, or prey species react more strongly than their predators to reduce predation. We discuss both hypotheses with our analyses of changes in phenology across four trophic levels: tree budburst, peak biomass of herbivorous caterpillars, breeding phenology of four insectivorous bird species and an avian predator. 3. In our long-term study, we show that between 1988 and 2005, budburst advanced (not significantly) with 0.17 d yr(-1), while between 1985 and 2005 both caterpillars (0.75 d year(-1)) and the hatching date of the passerine species (range for four species: 0.36-0.50 d year(-1)) have advanced, whereas raptor hatching dates showed no trend. 4. The caterpillar peak date was closely correlated with budburst date, as were the passerine hatching dates with the peak caterpillar biomass date. In all these cases, however, the slopes were significantly less than unity, showing that the response of the consumers is weaker than that of their food. This was also true for the avian predator, for which hatching dates were not correlated with the peak availability of fledgling passerines. As a result, the match between food demand and availability deteriorated over time for both the passerines and the avian predators. 5. These results could equally well be explained by consumers' insufficient responses as a consequence of constraints in adapting to climate change, or by them trying to escape predation from a higher trophic level, or both. Selection on phenology could thus be both from matches of phenology with higher and lower levels, and quantifying these can shed new light on why some organisms do adjust their phenology to climate change, while

  6. Effect of zink oxyde nanoparticles on the test function of water organisms of different trophic levels

    Science.gov (United States)

    Morgalev, Yu; Morgaleva, T.; Gosteva, I.; Morgalev, S.; Kulizhskiy, S.; Astafurova, T.

    2015-11-01

    The toxicity of zinc oxide nanoparticles (nZnO) with particle size Δ50 = 20 nm was evaluated according to the degree of toxicity of the aqueous disperse system (DS) with biological testing methods using a set of test organisms representing the major trophic levels.We observed the influence of the concentration degree of nZnO on toxic effects level on the fluorescence of the bacterial biosensor "Ekolyum-13", the chemotactic response of ciliates Paramecium caudatum, the rate of growth of unicellular algae Chlorella vulgaris Bayer, mortality of entomostracans Daphnia magna Straus and fish Danio rerio. The detected values of L(E)C50 are: for biosensor "Ekolyum-13" - 0.30 mg/L, for ciliates Paramecium caudatum - 0.14 mg/L, for Chlorella vulgaris Bayer - 0.17 mg/L and for Daphnia magna Straus - 0.52 mg/L. No toxicity of nZnO was detected in relation to fish Danio rerio, L(E)C50 > 100 mg/L. In assessing the maximum effect of nZnO according to GHS and EU Directive 93/67/ EEC, it is assigned to dangerous substances with a high degree of toxicity "Acute toxicity 1".

  7. Spider foraging strategy affects trophic cascades under natural and drought conditions.

    Science.gov (United States)

    Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

    2015-07-23

    Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests.

  8. Ecological and evolutionary consequences of tri-trophic interactions: Spatial variation and effects of plant density.

    Science.gov (United States)

    Abdala-Roberts, Luis; Parra-Tabla, Víctor; Moreira, Xoaquín; Ramos-Zapata, José

    2017-02-01

    The factors driving variation in species interactions are often unknown, and few studies have made a link between changes in interactions and the strength of selection. We report on spatial variation in functional responses by a seed predator (SP) and its parasitic wasps associated with the herb Ruellia nudiflora . We assessed the influence of plant density on consumer responses and determined whether density effects and spatial variation in functional responses altered natural selection by these consumers on the plant. We established common gardens at two sites in Yucatan, Mexico, and planted R. nudiflora at two densities in each garden. We recorded fruit output and SP and parasitoid attack; calculated relative fitness (seed number) under scenarios of three trophic levels (accounting for SP and parasitoid effects), two trophic levels (accounting for SP but not parasitoid effects), and one trophic level (no consumer effects); and compared selection strength on fruit number under these scenarios across sites and densities. There was spatial variation in SP recruitment, whereby the SP functional response was negatively density-dependent at one site but density-independent at the other; parasitoid responses were density-independent and invariant across sites. Site variation in SP attack led, in turn, to differences in SP selection on fruit output, and parasitoids did not alter SP selection. There were no significant effects of density at either site. Our results provide a link between consumer functional responses and consumer selection on plants, which deepens our understanding of geographic variation in the evolutionary outcomes of multitrophic interactions. © 2017 Botanical Society of America.

  9. Protection by GDNF and other trophic factors against the dopamine-depleting effects of neurotoxic doses of methamphetamine.

    Science.gov (United States)

    Cass, Wayne A; Peters, Laura E; Harned, Michael E; Seroogy, Kim B

    2006-08-01

    Repeated methamphetamine (METH) administration to animals can result in long-lasting decreases in striatal dopamine (DA) content. It has previously been shown that glial cell line-derived neurotrophic factor (GDNF) can reduce the DA-depleting effects of neurotoxic doses of METH. However, there are several other trophic factors that are protective against dopaminergic toxins. Thus, the present experiments further investigated the protective effect of GDNF as well as the protective effects of several other trophic factors. Male Fischer-344 rats were given an intracerebral injection of trophic factor (2-10 microg) 1 day before METH (5 mg/kg, s.c., 4 injections at 2-h intervals). Seven days later DA levels in the striatum were measured using high-performance liquid chromatography (HPLC). Initial experiments indicated that only intrastriatal GDNF, and not intranigral GDNF, was protective. Thereafter, all other trophic factors were administered into the striatum. Members of the GDNF family (GDNF, neurturin, and artemin) all provided significant protection against the DA-depleting effects of METH, with GDNF providing the greatest protection. Brain-derived neurotrophic factor, neurotrophin-3, acidic fibroblast growth factor, basic fibroblast growth factor, ciliary neurotrophic factor, transforming growth factor-alpha (TGF-alpha), heregulin beta1 (HRG-beta1), and amphiregulin (AR) provided no significant protection at the doses examined. These results suggest that the GDNF family of trophic factors can provide significant protection against the DA-depleting effects of neurotoxic doses of METH.

  10. Effect of zink oxyde nanoparticles on the test function of water organisms of different trophic levels

    International Nuclear Information System (INIS)

    Morgalev, Yu; Morgaleva, T; Gosteva, I; Morgalev, S; Kulizhskiy, S; Astafurova, T

    2015-01-01

    The toxicity of zinc oxide nanoparticles (nZnO) with particle size Δ 50 = 20 nm was evaluated according to the degree of toxicity of the aqueous disperse system (DS) with biological testing methods using a set of test organisms representing the major trophic levels.We observed the influence of the concentration degree of nZnO on toxic effects level on the fluorescence of the bacterial biosensor 'Ekolyum-13', the chemotactic response of ciliates Paramecium caudatum, the rate of growth of unicellular algae Chlorella vulgaris Bayer, mortality of entomostracans Daphnia magna Straus and fish Danio rerio. The detected values of L(E)C 50 are: for biosensor 'Ekolyum-13' – 0.30 mg/L, for ciliates Paramecium caudatum – 0.14 mg/L, for Chlorella vulgaris Bayer – 0.17 mg/L and for Daphnia magna Straus – 0.52 mg/L. No toxicity of nZnO was detected in relation to fish Danio rerio, L(E)C 50 > 100 mg/L. In assessing the maximum effect of nZnO according to GHS and EU Directive 93/67/ EEC, it is assigned to dangerous substances with a high degree of toxicity 'Acute toxicity 1'. (paper)

  11. Influence of trophic level, and calcification on the uptake of plutonium observed, in situ, in marine organisms

    International Nuclear Information System (INIS)

    Guary, J.C.; Fraizier, A.

    1977-01-01

    A study has been made of the transport mechanisms of plutonium in the marine environment. This work has shown that a relationship exists between the concentration of plutonium in marine plant and animal species and the trophic level of these organisms; this relation is evidenced by a decrease in the concentration of the radioelement as the trophic level of the species increases. Three modes of transport - via water, sediment and food - have been studied. Direct contact between sea water and organisms, the principal mode of transfer to marine species belonging to lower trophic levels (the primary producers and consumers), seems to play an important role in the uptake of plutonium. On the other hand, the sediment in contact with which certain species live does not appear to constitute an important transfer vector. The trophic relations between animal species lead one to assume that plutonium is transported also via the food-chain without necessarily implying that there is a concentration of the radioelement along the whole chain leading from the primary producers to the tertiary consumers. In addition, it has been possible to establish that there is a relation between the rate of plutonium uptake and the calcified structures of certain marine species comparable to that which exists in the bone tissue of terrestrial mammals. (author)

  12. Indirect effects and traditional trophic cascades: a test involving wolves, coyotes, and pronghorn.

    Science.gov (United States)

    Berger, Kim Murray; Gese, Eric M; Berger, Joel

    2008-03-01

    The traditional trophic cascades model is based on consumer resource interactions at each link in a food chain. However, trophic-level interactions, such as mesocarnivore release resulting from intraguild predation, may also be important mediators of cascades. From September 2001 to August 2004, we used spatial and seasonal heterogeneity in wolf distribution and abundance in the southern Greater Yellowstone Ecosystem to evaluate whether mesopredator release of coyotes (Canis latrans), resulting from the extirpation of wolves (Canis lupus), accounts for high rates of coyote predation on pronghorn (Antilocapra americana) fawns observed in some areas. Results of this ecological perturbation in wolf densities, coyote densities, and pronghorn neonatal survival at wolf-free and wolf-abundant sites support the existence of a species-level trophic cascade. That wolves precipitated a trophic cascade was evidenced by fawn survival rates that were four-fold higher at sites used by wolves. A negative correlation between coyote and wolf densities supports the hypothesis that interspecific interactions between the two species facilitated the difference in fawn survival. Whereas densities of resident coyotes were similar between wolf-free and wolf-abundant sites, the abundance of transient coyotes was significantly lower in areas used by wolves. Thus, differential effects of wolves on solitary coyotes may be an important mechanism by which wolves limit coyote densities. Our results support the hypothesis that mesopredator release of coyotes contributes to high rates of coyote predation on pronghorn fawns, and demonstrate the importance of alternative food web pathways in structuring the dynamics of terrestrial systems.

  13. Trophic transfer of microplastics in aquatic ecosystems: Identifying critical research needs.

    Science.gov (United States)

    Au, Sarah Y; Lee, Cindy M; Weinstein, John E; van den Hurk, Peter; Klaine, Stephen J

    2017-05-01

    To evaluate the process of trophic transfer of microplastics, it is important to consider various abiotic and biotic factors involved in their ingestion, egestion, bioaccumulation, and biomagnification. Toward this end, a review of the literature on microplastics has been conducted to identify factors influencing their uptake and absorption; their residence times in organisms and bioaccumulation; the physical effects of their aggregation in gastrointestinal tracts; and their potential to act as vectors for the transfer of other contaminants. Limited field evidence from higher trophic level organisms in a variety of habitats suggests that trophic transfer of microplastics may be a common phenomenon and occurs concurrently with direct ingestion. Critical research needs include standardizing methods of field characterization of microplastics, quantifying uptake and depuration rates in organisms at different trophic levels, quantifying the influence that microplastics have on the uptake and/or depuration of environmental contaminants among different trophic levels, and investigating the potential for biomagnification of microplastic-associated chemicals. More integrated approaches involving computational modeling are required to fully assess trophic transfer of microplastics. Integr Environ Assess Manag 2017;13:505-509. © 2017 SETAC. © 2017 SETAC.

  14. Biogeographical region and host trophic level determine carnivore endoparasite richness in the Iberian Peninsula.

    Science.gov (United States)

    Rosalino, L M; Santos, M J; Fernandes, C; Santos-Reis, M

    2011-05-01

    We address the question of whether host and/or environmental factors might affect endoparasite richness and distribution, using carnivores as a model. We reviewed studies published in international peer-reviewed journals (34 areas in the Iberian Peninsula), describing parasite prevalence and richness in carnivores, and collected information on site location, host bio-ecology, climate and detected taxa (Helminths, Protozoa and Mycobacterium spp.). Three hypotheses were tested (i) host based, (ii) environmentally based, and (iii) hybrid (combination of environmental and host). Multicollinearity reduced candidate variable number for modelling to 5: host weight, phylogenetic independent contrasts (host weight), mean annual temperature, host trophic level and biogeographical region. General Linear Mixed Modelling was used and the best model was a hybrid model that included biogeographical region and host trophic level. Results revealed that endoparasite richness is higher in Mediterranean areas, especially for the top predators. We suggest that the detected parasites may benefit from mild environmental conditions that occur in southern regions. Top predators have larger home ranges and are likely to be subjected to cascading effects throughout the food web, resulting in more infestation opportunities and potentially higher endoparasite richness. This study suggests that richness may be more affected by historical and regional processes (including climate) than by host ecological processes.

  15. Use of Stable Carbon and Nitrogen Isotopes for Trophic Level Evaluation and Food Webs Reconstruction in the Bay of Biscay : Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Chouvelon, T.; Caurant, F.; Mendez Fernandez, P.; Bustamante, P. [Littoral Environnement et Societes, La Rochelle (France); Spitz, J. [Centre de Recherche sur les Mammiferes Marins, La Rochelle (France)

    2013-07-15

    Assessing species' trophic level is one key aspect of ecosystem models, providing an indicator to monitor trophic links and ecosystem changes. The stable isotope ratios (SIR) of carbon and nitrogen provide longer term information on the average diet of consumers than the traditional stomach content method. However, using SIR in predators implies a good knowledge of the factors influencing prey species signature and lower trophic levels themselves, such as spatial and temporal variations. In this study, 129 species belonging to several taxa (i.e. crustaceans, molluscs, fish, marine mammals) from the Bay of Biscay where analysed for their isotopic signatures. Results confirmed the existence of several trophic food webs with probable different baseline signatures in this area, an essential consideration when using the isotopic tool for calculating species trophic level and potential evolution in space and time. Results demonstrated a spatial gradient from the shoreline to the oceanic domain for both carbon and nitrogen. (author)

  16. Trophic level transfer of microplastic: Mytilus edulis (L.) to Carcinus maenas (L.)

    International Nuclear Information System (INIS)

    Farrell, Paul; Nelson, Kathryn

    2013-01-01

    This study investigated the trophic transfer of microplastic from mussels to crabs. Mussels (Mytilus edulis) were exposed to 0.5 μm fluorescent polystyrene microspheres, then fed to crabs (Carcinus maenas). Tissue samples were then taken at intervals up to 21 days. The number of microspheres in the haemolymph of the crabs was highest at 24 h (15 033 ml −1 ± SE 3146), and was almost gone after 21 days (267 ml −1 ± SE 120). The maximum amount of microspheres in the haemolymph was 0.04% of the amount to which the mussels were exposed. Microspheres were also found in the stomach, hepatopancreas, ovary and gills of the crabs, in decreasing numbers over the trial period. This study is the first to show ‘natural’ trophic transfer of microplastic, and its translocation to haemolymph and tissues of a crab. This has implications for the health of marine organisms, the wider food web and humans. -- Highlights: ► Microplastic transferred in marine food chain. ► Microplastic transferred to haemolymph when ingested in food. ► Microplastic remains in organism for at least 21 days. -- This communication demonstrates trophic level transfer of microplastic particles from Mytilus edulis to Carcinus maenas

  17. [Effects of different trophic modes on growth characteristics, metabolism and cellular components of Chlorella vulgaris].

    Science.gov (United States)

    Kong, Weibao; Wang, Yang; Yang, Hong; Xi, Yuqin; Han, Rui; Niu, Shiquan

    2015-03-04

    We studied the effects of trophic modes related to glucose and light (photoautotrophy, mixotrophy and heterotrophy) on growth, cellular components and carbon metabolic pathway of Chlorella vulgaris. The parameters about growth of algal cells were investigated by using spectroscopy and chromatography techniques. When trophic mode changed from photoautotrophy to mixotrophy and to heterotrophy successively, the concentrations of soluble sugar, lipid and saturated C16/C18 fatty acids in C. vulgaris increased, whereas the concentrations of unsaturated C16, C18 fatty acids, proteins, photosynthetic pigments and 18 relative amino acids decreased. Light and glucose affect the growth, metabolism and the biochemical components biosynthesis of C. vulgaris. Addition of glucose can promote algal biomass accumulation, stimulate the synthesis of carbonaceous components, but inhibit nitrogenous components. Under illumination cultivation, concentration and consumption level of glucose decided the main trophic modes of C. vulgaris. Mixotrophic and heterotrophic cultivation could promote the growth of algal cells.

  18. Trophic redundancy reduces vulnerability to extinction cascades.

    Science.gov (United States)

    Sanders, Dirk; Thébault, Elisa; Kehoe, Rachel; Frank van Veen, F J

    2018-03-06

    Current species extinction rates are at unprecedentedly high levels. While human activities can be the direct cause of some extinctions, it is becoming increasingly clear that species extinctions themselves can be the cause of further extinctions, since species affect each other through the network of ecological interactions among them. There is concern that the simplification of ecosystems, due to the loss of species and ecological interactions, increases their vulnerability to such secondary extinctions. It is predicted that more complex food webs will be less vulnerable to secondary extinctions due to greater trophic redundancy that can buffer against the effects of species loss. Here, we demonstrate in a field experiment with replicated plant-insect communities, that the probability of secondary extinctions is indeed smaller in food webs that include trophic redundancy. Harvesting one species of parasitoid wasp led to secondary extinctions of other, indirectly linked, species at the same trophic level. This effect was markedly stronger in simple communities than for the same species within a more complex food web. We show that this is due to functional redundancy in the more complex food webs and confirm this mechanism with a food web simulation model by highlighting the importance of the presence and strength of trophic links providing redundancy to those links that were lost. Our results demonstrate that biodiversity loss, leading to a reduction in redundant interactions, can increase the vulnerability of ecosystems to secondary extinctions, which, when they occur, can then lead to further simplification and run-away extinction cascades. Copyright © 2018 the Author(s). Published by PNAS.

  19. Damped trophic cascades driven by fishing in model marine ecosystems

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Pedersen, Martin

    2010-01-01

    The largest perturbation on upper trophic levels of many marine ecosystems stems from fishing. The reaction of the ecosystem goes beyond the trophic levels directly targeted by the fishery. This reaction has been described either as a change in slope of the overall size spectrum or as a trophic...... cascade triggered by the removal of top predators. Here we use a novel size- and trait-based model to explore how marine ecosystems might react to perturbations from different types of fishing pressure. The model explicitly resolves the whole life history of fish, from larvae to adults. The results show...... that fishing does not change the overall slope of the size spectrum, but depletes the largest individuals and induces trophic cascades. A trophic cascade can propagate both up and down in trophic levels driven by a combination of changes in predation mortality and food limitation. The cascade is damped...

  20. Ecosystem Functions across Trophic Levels Are Linked to Functional and Phylogenetic Diversity

    Science.gov (United States)

    Thompson, Patrick L.; Davies, T. Jonathan; Gonzalez, Andrew

    2015-01-01

    In experimental systems, it has been shown that biodiversity indices based on traits or phylogeny can outperform species richness as predictors of plant ecosystem function. However, it is unclear whether this pattern extends to the function of food webs in natural ecosystems. Here we tested whether zooplankton functional and phylogenetic diversity explains the functioning of 23 natural pond communities. We used two measures of ecosystem function: (1) zooplankton community biomass and (2) phytoplankton abundance (Chl a). We tested for diversity-ecosystem function relationships within and across trophic levels. We found a strong correlation between zooplankton diversity and ecosystem function, whereas local environmental conditions were less important. Further, the positive diversity-ecosystem function relationships were more pronounced for measures of functional and phylogenetic diversity than for species richness. Zooplankton and phytoplankton biomass were best predicted by different indices, suggesting that the two functions are dependent upon different aspects of diversity. Zooplankton community biomass was best predicted by zooplankton trait-based functional richness, while phytoplankton abundance was best predicted by zooplankton phylogenetic diversity. Our results suggest that the positive relationship between diversity and ecosystem function can extend across trophic levels in natural environments, and that greater insight into variation in ecosystem function can be gained by combining functional and phylogenetic diversity measures. PMID:25693188

  1. Effect of the riparian vegetation removal on the trophic network of Neotropical stream fish assemblage

    Directory of Open Access Journals (Sweden)

    Pedro Sartori Manoel

    2018-02-01

    Full Text Available The study of the diet of fish is an important tool to assess different levels of environmental degradation, since the availability of food in the environment is a key factor for the fish occurrence. The removal of riparian vegetation usually degrades environmental quality, as this vegetation has an important role in providing energy to the ecosystem. This study investigates the effects of the removal of riparian vegetation on the fish assemblage trophic network. The study was carried out in two stretches of a southeastern Brazilian stream, one in a forest fragment and another in a pasture, during the wet and dry seasons of 2014. We analyzed the items consumed by each fish species using the frequency of occurrence and area of each item, which were combined to calculate the alimentary index, which was used to determine the food niche overlap of the fish and the specialization index of the trophic network. Aquatic Hexapoda, vegetal debris and organic matter dominated the trophic network of the two stretches. We detected higher values of food niche overlap in the forested stretch and more complex trophic networks in the pasture stretch. We found few seasonal variations in the items consumed and calculated indices in both stretches studied. The presence of grass on the banks in the pasture stretch and the importation of food resources from the upstream area may have provided a higher diversity of resources and consequently showed a more complex trophic network when compared to the forested stretch.

  2. Feeding habits and trophic levels of some demersal fish species in the Persian Gulf (Bushehr Province) using Ecopath model

    OpenAIRE

    Vahabnezhad, Arezoo

    2015-01-01

    A trophic study was carried out in February of 2012 to January 2013 on the ecosystem in the Persian Gulf, Bushehr provience. A total of 2,948 samples of stomach contents were analyzed based on the weight and number of food items and were identified about 40 preys. Crustacean and bony fish were as a main prey in most of the stomach contents . The mean average trophic level was estimated at 3.6 by Ecopath software. In this research, the mean level were studied between eight species varied fr...

  3. Effects of soybean resistance on variability in life history traits of the higher trophic level parasitoid Meteorus pulchricornis (Hymenoptera: Braconidae).

    Science.gov (United States)

    Li, X; Li, B; Xing, G; Meng, L

    2017-02-01

    To extrapolate the influence of plant cultivars varying in resistance levels to hosts on parasitoid life history traits, we estimated variation in parasitoid developmental and reproductive performances as a function of resistance in soybean cultivars, which were randomly chosen from a line of resistant genotypes. Our study showed that the parasitoid Meteorus pulchricornis varied widely in offspring survival and lifetime fecundity, but varied slightly in development time and adult body size, in response to the soybean cultivars that varied in resistance to the host Spodoptera litura. Furthermore, the variability in survival and lifetime fecundity was different between attacking the 2nd and the 4th instar host larvae, varying more in survival but less in lifetime fecundity when attacking the 4th than 2nd instar larvae. Our study provides further evidence supporting that plant resistance to herbivorous hosts have variable effects on different life history traits of higher trophic level parasitoids.

  4. Perfluorinated compounds: Levels, trophic web enrichments and human dietary intakes in transitional water ecosystems

    International Nuclear Information System (INIS)

    Renzi, Monia; Guerranti, Cristiana; Giovani, Andrea; Perra, Guido; Focardi, Silvano E.

    2013-01-01

    Highlights: • PFOA/S levels in a trophic web of a heavily human-stressed lagoon are measured. • High levels were found in mussels, clams and crabs. • The principal PFCs inflow sources for the ecosystem is the river. • Biota (i.e. macroalgae proliferation) contributes to redistribute pollutants in the lagoon. • Human daily dietary intakes are below maximum tolerable levels suggested by the EFSA. -- Abstract: The results of a study on levels of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), analyzed in terms of HPLC-ESI-MS in water, sediment, macrophyte, bivalve, crustacean and fish samples, are reported here. The aim of the research is to define, for the first time, PFOA/S levels in a heavily human-stressed transitional water ecosystem (Orbetello lagoon, Italy) and evaluate trophic web enrichments and human dietary intakes. The results obtained show that: (i) levels significantly higher than those reported in the literature were found in mussels, clams and crabs; (ii) the river is a significant pollution source; (iii) although absolute levels are relatively low, macroalgae proliferation contributes to redistribute pollutants from river-affected areas throughout the entire lagoon basin; (iv) to the best of our current knowledge, water-filtering species considered in this study are the most exposed to PFOA/S pollution; (v) human daily dietary intakes of PFOA/S through Slow Food-endorsed product consumption are below maximum tolerable levels suggested by the EFSA

  5. Trophic transfer of metal nanoparticles in freshwater ecosystems

    DEFF Research Database (Denmark)

    Tangaa, Stine Rosendal

    freshwater ecosystems range from a few ng/L in surface waters and up to mg/kg in sediments. Several studies have shown Ag ENPs to be toxic, bioaccumulative and harmful to aquatic biota within these concentration ranges. However, research on potential trophic transfer of Ag ENPs is limited. To investigate...... the aquatic ecosystems, Ag ENPs will undergo several transformation processes, ultimately leading to particles settling out of the water column. This will likely result in an increased concentration of ENPs in the sediment. In fact, predicted environmental concentrations of Ag ENPs in Danish and European...... freshwater food web. Future studies should concentrate on the internal distribution of Me-ENPs after uptake in both prey and predator, as this will increase the understanding of fate and effects of Me-ENPs on aquatic biota. Trophic transfer studies including more trophic levels, and higher pelagic organisms...

  6. Selective and context-dependent effects of chemical stress across trophic levels at the basis of marine food webs.

    Science.gov (United States)

    Mensens, Christoph; De Laender, Frederik; Janssen, Colin R; Rivera, Frances Camille; Sabbe, Koen; De Troch, Marleen

    2018-04-26

    Human activities increasingly impact the functioning of marine food webs, but anthropogenic stressors are seldom included in ecological study designs. Diet quality, as distinct from just diet quantity, has moreover rarely been highlighted in food web studies in a stress context. We measured the effects of metal and pesticide stress (copper and atrazine) on the contribution of a benthic intertidal diatom community to two processes that are key to the functioning of intertidal systems: biomass (diet quantity) and lipid (diet quality) production. We then examined if stressors affected diatom functioning by selectively targeting the species contributing most to functioning (selective stress effects) or by changing the species' functional contribution (context-dependent effects). Finally, we tested if stress-induced changes in diet quality altered the energy flow to the diatoms' main grazers (harpacticoid copepods). Diatom diet quantity was reduced by metal stress but not by low pesticide levels due to the presence of an atrazine-tolerant, mixotrophic species. Selective effects of the pesticide reduced diatom diet quality by 60% and 75% at low and high pesticide levels respectively, by shifting diatom community structure from dominance by lipid-rich species toward dominance by an atrazine-tolerant, but lipid-poor, species. Context-dependent effects did not affect individual diatom lipid content at low levels of both stressors, but caused diatoms to lose 40% of their lipids at high copper stress. Stress-induced changes in diet quality predicted the energy flow from the diatoms to their copepod consumers, which lost half of their lipids when feeding on diatoms grown under low and high pesticide and high metal stress. Selective pesticide effects were a more important threat for trophic energy transfer than context-dependent effects of both stressors, with shifts in diatom community structure affecting the energy flow to their copepod grazers at stress levels where no

  7. A comprehensive assessment of mercury exposure in penguin populations throughout the Southern Hemisphere: Using trophic calculations to identify sources of population-level variation

    International Nuclear Information System (INIS)

    Brasso, Rebecka L.; Chiaradia, André; Polito, Michael J.; Raya Rey, Andrea; Emslie, Steven D.

    2015-01-01

    Highlights: • Mercury concentrations documented for 10 species of penguins (26 breeding populations). • Mercury concentrations ⩽2.00 ppm in feathers from 18/26 penguin populations. • Trophic level calculations revealed source of population-level variation in mercury. • First documentation of geographic mercury ‘hotspots’ for penguin populations. - Abstract: The wide geographic distribution of penguins (Order Sphenisciformes) throughout the Southern Hemisphere provided a unique opportunity to use a single taxonomic group as biomonitors of mercury among geographically distinct marine ecosystems. Mercury concentrations were compared among ten species of penguins representing 26 geographically distinct breeding populations. Mercury concentrations were relatively low (⩽2.00 ppm) in feathers from 18/26 populations considered. Population-level differences in trophic level explained variation in mercury concentrations among Little, King, and Gentoo penguin populations. However, Southern Rockhopper and Magellanic penguins breeding on Staten Island, Tierra del Fuego, had the highest mercury concentrations relative to their conspecifics despite foraging at a lower trophic level. The concurrent use of stable isotope and mercury data allowed us to document penguin populations at the greatest risk of exposure to harmful concentrations of mercury as a result of foraging at a high trophic level or in geographic ‘hot spots’ of mercury availability

  8. Trophic signatures of seabirds suggest shifts in oceanic ecosystems

    Science.gov (United States)

    Gagne, Tyler O.; Hyrenbach, K. David; Hagemann, Molly E.; Van Houtan, Kyle S.

    2018-01-01

    Pelagic ecosystems are dynamic ocean regions whose immense natural capital is affected by climate change, pollution, and commercial fisheries. Trophic level–based indicators derived from fishery catch data may reveal the food web status of these systems, but the utility of these metrics has been debated because of targeting bias in fisheries catch. We analyze a unique, fishery-independent data set of North Pacific seabird tissues to inform ecosystem trends over 13 decades (1890s to 2010s). Trophic position declined broadly in five of eight species sampled, indicating a long-term shift from higher–trophic level to lower–trophic level prey. No species increased their trophic position. Given species prey preferences, Bayesian diet reconstructions suggest a shift from fishes to squids, a result consistent with both catch reports and ecosystem models. Machine learning models further reveal that trophic position trends have a complex set of drivers including climate, commercial fisheries, and ecomorphology. Our results show that multiple species of fish-consuming seabirds may track the complex changes occurring in marine ecosystems. PMID:29457134

  9. Oligotrophy as a major driver of mercury bioaccumulation in medium-to high-trophic level consumers: A marine ecosystem-comparative study.

    Science.gov (United States)

    Chouvelon, Tiphaine; Cresson, Pierre; Bouchoucha, Marc; Brach-Papa, Christophe; Bustamante, Paco; Crochet, Sylvette; Marco-Miralles, Françoise; Thomas, Bastien; Knoery, Joël

    2018-02-01

    Mercury (Hg) is a global contaminant of environmental concern. Numerous factors influencing its bioaccumulation in marine organisms have already been described at both individual and species levels (e.g., size or age, habitat, trophic level). However, few studies have compared the trophic characteristics of ecosystems to explain underlying mechanisms of differences in Hg bioaccumulation and biomagnification among food webs and systems. The present study aimed at investigating the potential primary role of the trophic status of systems on Hg bioaccumulation and biomagnification in temperate marine food webs, as shown by their medium-to high-trophic level consumers. It used data from samples collected at the shelf-edge (i.e. offshore organisms) in two contrasted ecosystems: the Bay of Biscay in the North-East Atlantic Ocean and the Gulf of Lion in the North-West Mediterranean Sea. Seven species including crustaceans, sharks and teleost fish, previously analysed for their total mercury (T-Hg) concentrations and their stable carbon and nitrogen isotope compositions, were considered for a meta-analysis. In addition, methylated mercury forms (or methyl-mercury, Me-Hg) were analysed. Mediterranean organisms presented systematically lower sizes than Atlantic ones, and lower δ 13 C and δ 15 N values, the latter values especially highlighting the more oligotrophic character of Mediterranean waters. Mediterranean individuals also showed significantly higher T-Hg and Me-Hg concentrations. Conversely, Me-Hg/T-Hg ratios were higher than 85% for all species, and quite similar between systems. Finally, the biomagnification power of Hg was different between systems when considering T-Hg, but not when considering Me-Hg, and was not different between the Hg forms within a given system. Overall, the different parameters showed the crucial role of the low primary productivity and its effects rippling through the compared ecosystems in the higher Hg bioaccumulation seen in organisms

  10. Effect of grazers and viruses on bacterial community structure and production in two contrasting trophic lakes

    Directory of Open Access Journals (Sweden)

    Domaizon Isabelle

    2011-04-01

    Full Text Available Abstract Background Over the last 30 years, extensive studies have revealed the crucial roles played by microbes in aquatic ecosystems. It has been shown that bacteria, viruses and protozoan grazers are dominant in terms of abundance and biomass. The frequent interactions between these microbiological compartments are responsible for strong trophic links from dissolved organic matter to higher trophic levels, via heterotrophic bacteria, which form the basis for the important biogeochemical roles of microbial food webs in aquatic ecosystems. To gain a better understanding of the interactions between bacteria, viruses and flagellates in lacustrine ecosystems, we investigated the effect of protistan bacterivory on bacterial abundance, production and structure [determined by 16S rRNA PCR-DGGE], and viral abundance and activity of two lakes of contrasting trophic status. Four experiments were conducted in the oligotrophic Lake Annecy and the mesotrophic Lake Bourget over two seasons (early spring vs. summer using a fractionation approach. In situ dark vs. light incubations were performed to consider the effects of the different treatments in the presence and absence of phototrophic activity. Results The presence of grazers (i.e. Conclusions Our results highlight the importance of a synergistic effect, i.e. the positive influence of grazers on viral activities in sustaining (directly and indirectly bacterial production and affecting composition, in both oligotrophic and mesotrophic lakes.

  11. Adaptive evolution of body size subject to indirect effect in trophic cascade system.

    Science.gov (United States)

    Wang, Xin; Fan, Meng; Hao, Lina

    2017-09-01

    Trophic cascades represent a classic example of indirect effect and are wide-spread in nature. Their ecological impact are well established, but the evolutionary consequences have received even less theoretical attention. We theoretically and numerically investigate the trait (i.e., body size of consumer) evolution in response to indirect effect in a trophic cascade system. By applying the quantitative trait evolutionary theory and the adaptive dynamic theory, we formulate and explore two different types of eco-evolutionary resource-consumer-predator trophic cascade model. First, an eco-evolutionary model incorporating the rapid evolution is formulated to investigate the effect of rapid evolution of the consumer's body size, and to explore the impact of density-mediate indirect effect on the population dynamics and trait dynamics. Next, by employing the adaptive dynamic theory, a long-term evolutionary model of consumer body size is formulated to evaluate the effect of long-term evolution on the population dynamics and the effect of trait-mediate indirect effect. Those models admit rich dynamics that has not been observed yet in empirical studies. It is found that, both in the trait-mediated and density-mediated system, the body size of consumer in predator-consumer-resource interaction (indirect effect) evolves smaller than that in consumer-resource and predator-consumer interaction (direct effect). Moreover, in the density-mediated system, we found that the evolution of consumer body size contributes to avoiding consumer extinction (i.e., evolutionary rescue). The trait-mediate and density-mediate effects may produce opposite evolutionary response. This study suggests that the trophic cascade indirect effect affects consumer evolution, highlights a more comprehensive mechanistic understanding of the intricate interplay between ecological and evolutionary force. The modeling approaches provide avenue for study on indirect effects from an evolutionary perspective

  12. Existence of limit cycles in a three level trophic chain with Lotka–Volterra and Holling type II functional responses

    International Nuclear Information System (INIS)

    Castellanos, Víctor; Chan-López, Ramón E.

    2017-01-01

    In this paper we analyze a three level trophic chain model, considering a logistic growth for the lowest trophic level, a Lotka–Volterra and Holling type II functional responses for predators in the middle and in the cusp in the chain, respectively. The differential system is based on the Leslie–Gower scheme. We establish conditions on the parameters that guarantee the coexistence of populations in the habitat. We find that an Andronov–Hopf bifurcation takes place. The first Lyapunov coefficient is computed explicitly and we show the existence of a stable limit cycle. Numerically, we observe a strange attractor and there exist evidence of the model to exhibit chaotic dynamics.

  13. Mercury biomagnification in a contaminated estuary food web: Effects of age and trophic position using stable isotope analyses

    International Nuclear Information System (INIS)

    Coelho, J.P.; Mieiro, C.L.; Pereira, E.; Duarte, A.C.; Pardal, M.A.

    2013-01-01

    Highlights: ► High trophic magnification potential of mercury in a temperate contaminated estuary. ► The use of age adjusted data provided better fitting to linear regression curves. ► Similar TMFs in other studies suggest stable magnification regardless of latitude. -- Abstract: The main aim of this study was to ascertain the biomagnification processes in a mercury-contaminated estuary, by clarifying the trophic web structure through stable isotope ratios. For this purpose, primary producers (seagrasses and macroalgae), invertebrates (detritivores and benthic predators) and fish were analysed for total and organic mercury and for stable carbon and nitrogen isotopic signatures. Trophic structure was accurately described by δ 15 N, while δ 13 C reflected the carbon source for each species. An increase of mercury levels was observed with trophic level, particularly for organic mercury. Results confirm mercury biomagnification to occur in this estuarine food web, especially in the organic form, both in absolute concentrations and fraction of total mercury load. Age can be considered an important variable in mercury biomagnification studies, and data adjustments to account for the different exposure periods may be necessary for a correct assessment of trophic magnification rates and ecological risk

  14. A comprehensive assessment of mercury exposure in penguin populations throughout the Southern Hemisphere: Using trophic calculations to identify sources of population-level variation.

    Science.gov (United States)

    Brasso, Rebecka L; Chiaradia, André; Polito, Michael J; Raya Rey, Andrea; Emslie, Steven D

    2015-08-15

    The wide geographic distribution of penguins (Order Sphenisciformes) throughout the Southern Hemisphere provided a unique opportunity to use a single taxonomic group as biomonitors of mercury among geographically distinct marine ecosystems. Mercury concentrations were compared among ten species of penguins representing 26 geographically distinct breeding populations. Mercury concentrations were relatively low (⩽2.00ppm) in feathers from 18/26 populations considered. Population-level differences in trophic level explained variation in mercury concentrations among Little, King, and Gentoo penguin populations. However, Southern Rockhopper and Magellanic penguins breeding on Staten Island, Tierra del Fuego, had the highest mercury concentrations relative to their conspecifics despite foraging at a lower trophic level. The concurrent use of stable isotope and mercury data allowed us to document penguin populations at the greatest risk of exposure to harmful concentrations of mercury as a result of foraging at a high trophic level or in geographic 'hot spots' of mercury availability. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Trophic interactions, ecosystem structure and function in the southern Yellow Sea

    Science.gov (United States)

    Lin, Qun; Jin, Xianshi; Zhang, Bo

    2013-01-01

    The southern Yellow Sea is an important fishing ground, providing abundant fishery resources. However, overfishing and climate change have caused a decline in the resource and damaged the ecosystem. We developed an ecosystem model to analyze the trophic interactions and ecosystem structure and function to guide sustainable development of the ecosystem. A trophic mass-balance model of the southern Yellow Sea during 2000-2001 was constructed using Ecopath with Ecosim software. We defined 22 important functional groups and studied their diet composition. The trophic levels of fish, shrimp, crabs, and cephalopods were between 2.78 and 4.39, and the mean trophic level of the fisheries was 3.24. The trophic flows within the food web occurred primarily in the lower trophic levels. The mean trophic transfer efficiency was 8.1%, of which 7.1% was from primary producers and 9.3% was from detritus within the ecosystem. The transfer efficiency between trophic levels II to III to IV to V to >V was 5.0%, 5.7%, 18.5%, and 19.7%-20.4%, respectively. Of the total flow, phytoplankton contributed 61% and detritus contributed 39%. Fishing is defined as a top predator within the ecosystem, and has a negative impact on most commercial species. Moreover, the ecosystem had a high gross efficiency of the fishery and a high value of primary production required to sustain the fishery. Together, our data suggest there is high fishing pressure in the southern Yellow Sea. Based on analysis of Odum's ecological parameters, this ecosystem was at an immature stage. Our results provide some insights into the structure and development of this ecosystem.

  16. A comparative analysis of feeding and trophic level ecology in stingrays (Rajiformes; Myliobatoidei and electric rays (Rajiformes: Torpedinoidei.

    Directory of Open Access Journals (Sweden)

    Ian P Jacobsen

    Full Text Available Standardised diets and trophic level (T L estimates were calculated for 75 ray species from the suborders Myliobatoidei (67 spp. and Torpedinoidei (8 spp.. Decapod crustaceans (31.71 ± 3.92% and teleost fishes (16.45 ± 3.43% made the largest contribution to the standardised diet of the Myliobatoidei. Teleost fishes (37.40 ± 16.09% and polychaete worms (31.96 ± 14.22% were the most prominent prey categories in the standardised diet of the suborder Torpedinoidei. Cluster analysis identified nine major trophic guilds the largest of which were decapod crustaceans (24 species, teleost fishes (11 species and molluscs (11 species. Trophic level estimates for rays ranged from 3.10 for Potamotrygon falkneri to 4.24 for Gymnura australis, Torpedo marmorata and T. nobiliana. Secondary consumers with a T L <4.00 represented 84% of the species examined, with the remaining 12 species (16% classified as tertiary consumers (T L ≥ 4.00. Tertiary consumers included electric rays (Torpedo, 3 spp. and Hypnos, 1 sp., butterfly rays (Gymnura, 4 spp., stingrays (2 spp. and Potamotrygonid stingrays (2 spp.. Feeding strategies were identified as the primary factor of influence with respect to Myliobatoidei and Torpedinoidei T L estimates with inter-family comparisons providing the greatest insight into Myliobatoidei and Torpedinoidei relationships.

  17. Food-web dynamics and trophic-level interactions in a multispecies community of freshwater unionids

    Science.gov (United States)

    Nichols, S.J.; Garling, D.

    2000-01-01

    We compared feeding habits and trophic-level relationships of unionid species in a detritus-dominated river and an alga-dominated lake using biochemical analyses, gut contents, and stable-isotope ratios. The δ13C ratios for algae and other food-web components show that all unionids from both the river and the lake used bacterial carbons, not algal carbons, as their main dietary source, in spite of positive selection and concentration of diatoms and green algae from the water column in the gut and mantle cavity. Algae did provide key nutrients such as vitamins A and D and phytosterols that were bioaccumulated in the tissues of all species. The δ15N ratios for the multispecies unionid community in the Huron River indicated some differences in nitrogen enrichment between species, the greatest enrichment being found in Pyganadon grandis. These δ15N ratios indicate that unionids may not always feed as primary consumers or omnivores. Stable-isotope data were critical for delineating diets and trophic-level interactions of this group of filter-feeders. Further refinements in identifying bacterial and picoplankton components of the fine particulate organic matter are needed to complete our understanding of resource partitioning between multispecies unionid populations.

  18. Trophic interaction modifications: an empirical and theoretical framework.

    Science.gov (United States)

    Terry, J Christopher D; Morris, Rebecca J; Bonsall, Michael B

    2017-10-01

    Consumer-resource interactions are often influenced by other species in the community. At present these 'trophic interaction modifications' are rarely included in ecological models despite demonstrations that they can drive system dynamics. Here, we advocate and extend an approach that has the potential to unite and represent this key group of non-trophic interactions by emphasising the change to trophic interactions induced by modifying species. We highlight the opportunities this approach brings in comparison to frameworks that coerce trophic interaction modifications into pairwise relationships. To establish common frames of reference and explore the value of the approach, we set out a range of metrics for the 'strength' of an interaction modification which incorporate increasing levels of contextual information about the system. Through demonstrations in three-species model systems, we establish that these metrics capture complimentary aspects of interaction modifications. We show how the approach can be used in a range of empirical contexts; we identify as specific gaps in current understanding experiments with multiple levels of modifier species and the distributions of modifications in networks. The trophic interaction modification approach we propose can motivate and unite empirical and theoretical studies of system dynamics, providing a route to confront ecological complexity. © 2017 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

  19. Trophic cascades linking wolves (Canis lupus), coyotes (Canis latrans), and small mammals

    Science.gov (United States)

    Miller, B.J.; Harlow, H.J.; Harlow, T.S.; Biggins, D.; Ripple, W.J.

    2012-01-01

    When large carnivores are extirpated from ecosystems that evolved with apex predators, these systems can change at the herbivore and plant trophic levels. Such changes across trophic levels are called cascading effects and they are very important to conservation. Studies on the effects of reintroduced wolves in Yellowstone National Park have examined the interaction pathway of wolves (Canis lupus L., 1758) to ungulates to plants. This study examines the interaction effects of wolves to coyotes to rodents (reversing mesopredator release in the absence of wolves). Coyotes (Canis latrans Say, 1823) generally avoided areas near a wolf den. However, when in the proximity of a den, they used woody habitats (pine or sage) compared with herbaceous habitats (grass or forb or sedge)- when they were away from the wolf den. Our data suggested a significant increase in rodent numbers, particularly voles (genus Microtus Schrank, 1798), during the 3-year study on plots that were within 3 km of the wolf den, but we did not detect a significant change in rodent numbers over time for more distant plots. Predation by coyotes may have depressed numbers of small mammals in areas away from the wolf den. These factors indicate a top-down effect by wolves on coyotes and subsequently on the rodents of the area. Restoration of wolves could be a powerful tool for regulating predation at lower trophic levels.

  20. Network structure beyond food webs: mapping non-trophic and trophic interactions on Chilean rocky shores.

    Science.gov (United States)

    Sonia Kéfi; Berlow, Eric L; Wieters, Evie A; Joppa, Lucas N; Wood, Spencer A; Brose, Ulrich; Navarrete, Sergio A

    2015-01-01

    How multiple types of non-trophic interactions map onto trophic networks in real communities remains largely unknown. We present the first effort, to our knowledge, describing a comprehensive ecological network that includes all known trophic and diverse non-trophic links among >100 coexisting species for the marine rocky intertidal community of the central Chilean coast. Our results suggest that non-trophic interactions exhibit highly nonrandom structures both alone and with respect to food web structure. The occurrence of different types of interactions, relative to all possible links, was well predicted by trophic structure and simple traits of the source and target species. In this community, competition for space and positive interactions related to habitat/refuge provisioning by sessile and/or basal species were by far the most abundant non-trophic interactions. If these patterns are orroborated in other ecosystems, they may suggest potentially important dynamic constraints on the combined architecture of trophic and non-trophic interactions. The nonrandom patterning of non-trophic interactions suggests a path forward for developing a more comprehensive ecological network theory to predict the functioning and resilience of ecological communities.

  1. Interactions to the fifth trophic level: secondary and tertiary parasitoid wasps show extraordinary efficiency in utilizing host resources

    NARCIS (Netherlands)

    Harvey, J.A.; Wagenaar, R.; Bezemer, T.M.

    2009-01-01

    1. Parasitoid wasps are highly efficient organisms at utilizing and assimilating limited resources from their hosts. This study explores interactions over three trophic levels, from the third (primary parasitoid) to the fourth (secondary parasitoid) and terminating in the fifth (tertiary

  2. Evaluating trophic cascades as drivers of regime shifts in different ocean ecosystems

    Science.gov (United States)

    Pershing, Andrew J.; Mills, Katherine E.; Record, Nicholas R.; Stamieszkin, Karen; Wurtzell, Katharine V.; Byron, Carrie J.; Fitzpatrick, Dominic; Golet, Walter J.; Koob, Elise

    2015-01-01

    In ecosystems that are strongly structured by predation, reducing top predator abundance can alter several lower trophic levels—a process known as a trophic cascade. A persistent trophic cascade also fits the definition of a regime shift. Such ‘trophic cascade regime shifts' have been reported in a few pelagic marine systems—notably the Black Sea, Baltic Sea and eastern Scotian Shelf—raising the question of how common this phenomenon is in the marine environment. We provide a general methodology for distinguishing top-down and bottom-up effects and apply this methodology to time series from these three ecosystems. We found evidence for top-down forcing in the Black Sea due primarily to gelatinous zooplankton. Changes in the Baltic Sea are primarily bottom-up, strongly structured by salinity, but top-down forcing related to changes in cod abundance also shapes the ecosystem. Changes in the eastern Scotian Shelf that were originally attributed to declines in groundfish are better explained by changes in stratification. Our review suggests that trophic cascade regime shifts are rare in open ocean ecosystems and that their likelihood increases as the residence time of water in the system increases. Our work challenges the assumption that negative correlation between consecutive trophic levels implies top-down forcing.

  3. Changes in the trophic structure of the northern Benguela before ...

    African Journals Online (AJOL)

    The dominant small pelagic fish, characteristic of upwelling systems, were replaced ... as did the weighted trophic level of the community (excluding plankton), after the ... may have altered the trophic control mechanism operating in the system, ...

  4. Assessing cadmium distribution applying neutron radiography in moss trophical levels, located in Szarvasko, Hungary

    Energy Technology Data Exchange (ETDEWEB)

    Varga, J.; Koroesi, F. E-mail: fkorosi@hotmail.com; Balasko, M. E-mail: balasko@sunserv.kfki.hu; Naar, Z

    2004-10-01

    The measuring station of the 10 MW VVR-SM research reactor at the Budapest Neutron Centre (Hungary) was used to perform dynamic neutron radiography (DNR), which was, to our best knowledge, the first time, in a Tortella tortuosa biotope. In the conducted study, two trophical levels, moss and spider Thomisidae sp. juv., were examined. Cadmium penetration routes, distribution and accumulation zones were visualized in the leafy gametophyte life cycle of Tortella tortuosa and in the organs of the spider.

  5. Bioaccumulation and biomagnification of mercury in African lakes: The importance of trophic status

    Energy Technology Data Exchange (ETDEWEB)

    Poste, Amanda E., E-mail: amanda.poste@niva.no [Norwegian Institute for Water Research, Gaustadalléen 21, 0349 Oslo (Norway); Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Muir, Derek C.G. [Aquatic Contaminants Research Division, Environment Canada, 867 Lakeshore Drive, Burlington, ON L7R 4A6 (Canada); Guildford, Stephanie J.; Hecky, Robert E. [Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Large Lakes Observatory, University of Minnesota Duluth, 2205 East Fifth Street, Duluth, MN 55812 (United States)

    2015-02-15

    Despite the global prevalence of both mercury (Hg) contamination and anthropogenic eutrophication, relatively little is known about the behavior of Hg in eutrophic and hypereutrophic systems or the effects of lake trophic status on Hg uptake and trophodynamics. In the current study we explore Hg trophodynamics at 8 tropical East African study sites ranging from mesotrophic to hypereutrophic, in order to assess the influence of lake trophic status on Hg uptake and biomagnification. Comprehensive water, plankton and fish samples were collected for analysis of total mercury (THg) and stable carbon and nitrogen isotopic ratios. We found evidence that uptake of THg into phytoplankton tended to be lower in higher productivity systems. THg concentrations in fish were generally low, and THg trophic magnification factors (TMFs; representing the average increase in contaminant concentrations from one trophic level to the next) ranged from 1.9 to 5.6. Furthermore TMFs were significantly lower in hypereutrophic lakes than in meso- and eutrophic lakes, and were negatively related to chlorophyll a concentrations both across our study lakes, and across African lakes for which literature data were available. These observations suggest that THg concentrations were strongly influenced by trophic status, with year-round high phytoplankton and fish growth rates reducing the potential for high THg in fish in these productive tropical lakes. - Highlights: • We characterized Hg in water and biota from 8 East African study sites. • Hg concentrations in fish were low and should not pose a risk to human consumers. • Hg uptake and biomagnification rates were negatively related to trophic status. • Growth dilution in phytoplankton and consumer trophic levels led to low fish Hg.

  6. Bioaccumulation and biomagnification of mercury in African lakes: The importance of trophic status

    International Nuclear Information System (INIS)

    Poste, Amanda E.; Muir, Derek C.G.; Guildford, Stephanie J.; Hecky, Robert E.

    2015-01-01

    Despite the global prevalence of both mercury (Hg) contamination and anthropogenic eutrophication, relatively little is known about the behavior of Hg in eutrophic and hypereutrophic systems or the effects of lake trophic status on Hg uptake and trophodynamics. In the current study we explore Hg trophodynamics at 8 tropical East African study sites ranging from mesotrophic to hypereutrophic, in order to assess the influence of lake trophic status on Hg uptake and biomagnification. Comprehensive water, plankton and fish samples were collected for analysis of total mercury (THg) and stable carbon and nitrogen isotopic ratios. We found evidence that uptake of THg into phytoplankton tended to be lower in higher productivity systems. THg concentrations in fish were generally low, and THg trophic magnification factors (TMFs; representing the average increase in contaminant concentrations from one trophic level to the next) ranged from 1.9 to 5.6. Furthermore TMFs were significantly lower in hypereutrophic lakes than in meso- and eutrophic lakes, and were negatively related to chlorophyll a concentrations both across our study lakes, and across African lakes for which literature data were available. These observations suggest that THg concentrations were strongly influenced by trophic status, with year-round high phytoplankton and fish growth rates reducing the potential for high THg in fish in these productive tropical lakes. - Highlights: • We characterized Hg in water and biota from 8 East African study sites. • Hg concentrations in fish were low and should not pose a risk to human consumers. • Hg uptake and biomagnification rates were negatively related to trophic status. • Growth dilution in phytoplankton and consumer trophic levels led to low fish Hg

  7. Trophic flexibility and the persistence of understory birds in intensively logged rainforest.

    Science.gov (United States)

    Edwards, David P; Woodcock, Paul; Newton, Rob J; Edwards, Felicity A; Andrews, David J R; Docherty, Teegan D S; Mitchell, Simon L; Ota, Takahiro; Benedick, Suzan; Bottrell, Simon H; Hamer, Keith C

    2013-10-01

    Effects of logging on species composition in tropical rainforests are well known but may fail to reveal key changes in species interactions. We used nitrogen stable-isotope analysis of 73 species of understory birds to quantify trophic responses to repeated intensive logging of rainforest in northern Borneo and to test 4 hypotheses: logging has significant effects on trophic positions and trophic-niche widths of species, and the persistence of species in degraded forest is related to their trophic positions and trophic-niche widths in primary forest. Species fed from higher up the food chain and had narrower trophic-niche widths in degraded forest. Species with narrow trophic-niche widths in primary forest were less likely to persist after logging, a result that indicates a higher vulnerability of dietary specialists to local extinction following habitat disturbance. Persistence of species in degraded forest was not related to a species' trophic position. These results indicate changes in trophic organization that were not apparent from changes in species composition and highlight the importance of focusing on trophic flexibility over the prevailing emphasis on membership of static feeding guilds. Our results thus support the notion that alterations to trophic organization and interactions within tropical forests may be a pervasive and functionally important hidden effect of forest degradation. © 2013 Society for Conservation Biology.

  8. Trait-mediated trophic cascade creates enemy-free space for nesting hummingbirds.

    Science.gov (United States)

    Greeney, Harold F; Meneses, M Rocio; Hamilton, Chris E; Lichter-Marck, Eli; Mannan, R William; Snyder, Noel; Snyder, Helen; Wethington, Susan M; Dyer, Lee A

    2015-09-01

    The indirect effects of predators on nonadjacent trophic levels, mediated through traits of intervening species, are collectively known as trait-mediated trophic cascades. Although birds are important predators in terrestrial ecosystems, clear examples of trait-mediated indirect effects involving bird predators have almost never been documented. Such indirect effects are important for structuring ecological communities and are likely to be negatively impacted by habitat fragmentation, climate change, and other factors that reduce abundance of top predators. We demonstrate that hummingbirds in Arizona realize increased breeding success when nesting in association with hawks. An enemy-free nesting space is created when jays, an important source of mortality for hummingbird nests, alter their foraging behavior in the presence of their hawk predators.

  9. Mesoscale eddies are oases for higher trophic marine life

    KAUST Repository

    Godø , Olav R.; Samuelsen, Annette; Macaulay, Gavin J.; Patel, Ruben; Hjø llo, Solfrid Sæ tre; Horne, John; Kaartvedt, Stein; Johannessen, Johnny A.

    2012-01-01

    Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur. By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean. Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life. 2012 God et al.

  10. Mesoscale eddies are oases for higher trophic marine life

    KAUST Repository

    Godø, Olav R.

    2012-01-17

    Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur. By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean. Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life. 2012 God et al.

  11. Mesoscale eddies are oases for higher trophic marine life.

    Directory of Open Access Journals (Sweden)

    Olav R Godø

    Full Text Available Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur. By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean. Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life.

  12. Bioaccumulation and trophic transfer of perfluorinated compounds in a eutrophic freshwater food web

    International Nuclear Information System (INIS)

    Xu, Jian; Guo, Chang-Sheng; Zhang, Yuan; Meng, Wei

    2014-01-01

    In this study, the bioaccumulation of perfluorinated compounds from a food web in Taihu Lake in China was investigated. The organisms included egret bird species, carnivorous fish, omnivorous fish, herbivorous fish, zooplankton, phytoplankton, zoobenthos and white shrimp. Isotope analysis by δ 13 C and δ 15 N indicated that the carnivorous fish and egret were the top predators in the studied web, occupying trophic levels intermediate between 3.66 and 4.61, while plankton was at the lowest trophic level. Perfluorinated carboxylates (PFCAs) with 9–12 carbons were significantly biomagnified, with trophic magnification factors (TMFs) ranging from 2.1 to 3.7. The TMF of perfluorooctane sulfonate (PFOS) (2.9) was generally comparable to or lower than those of the PFCAs in the same food web. All hazard ratio (HR) values reported for PFOS and perfluorooctanoate (PFOA) were less than unity, suggesting that the detected levels would not cause any immediate health effects to the people in Taihu Lake region through the consumption of shrimps and fish. -- Highlights: • Biomagnification of PFCs in the food web of a eutrophic freshwater lake was studied. • Carnivorous fish and egret were the top predators while plankton was at the lowest trophic level. • PFCAs with 9–12 carbons were significantly biomagnified. • TMF of PFOS was comparable to or lower than those of the PFCAs in the same food web. • PFOS and PFOA would not cause health effects to the people via diet consumption. -- PFCs were found to be bioaccumulated and biomagnified in a food web from a eutrophic freshwater lake in subtropical area

  13. Zebra mussel filter feeding and food-limited production of Daphnia: Recent changes in lower trophic level dynamics of Oneida Lake, New York, U.S.A.

    Science.gov (United States)

    Horgan, M.J.; Mills, E.L.

    1999-01-01

    Exotic zebra mussels can alter lower trophic level dynamics in lakes that they colonize by consuming large quantities of phytoplankton. We simulated the indirect effects of zebra mussel grazing on Daphnia by artificially reducing phytoplankton concentration for in situ Daphnia reproduction experiments. The response of Daphnia reproduction to reduced phytoplankton was evaluated for both the in situ experiments and field observations in Oneida Lake, New York, U.S.A. Oneida Lake has had an abundant population of zebra mussels since 1992. Our experiments revealed that fecundity of individuals from two species of Daphnia was positively related to phytoplankton concentration during the spring clearwater phase, although there was no discernible effect of food concentration on fecundity in summer cyanobacteria-dominated assemblages. The experimental results suggest that Daphnia fecundity responds to chlorophyll a concentrations zebra mussels became abundant in Oneida Lake have been characterized by high water clarity, low chlorophyll concentrations, long clearwater phases, and low Daphnia biomass compared with the previous 17 years. The food web effects of zebra mussel grazing are complex and it will take more years for impacts at higher trophic levels to develop and be identified.

  14. Tri-trophic level impact of host plant linamarin and lotaustralin on Tetranychus urticae and its predator Phytoseiulus persimilis.

    Science.gov (United States)

    Rojas, M Guadalupe; Morales-Ramos, Juan Alfredo

    2010-12-01

    The impact of linamarin and lotaustralin content in the leaves of lima beans, Phaseolus lunatus L., on the second and third trophic levels was studied in the two-spotted spider mite, Tetranychus urticae (Koch), and its predator Phytoseiulus persimilis Athias-Henriot. The content of linamarin was higher in terminal trifoliate leaves (435.5 ppm) than in primary leaves (142.1 ppm) of Henderson bush lima beans. However, linamarin concentrations were reversed at the second trophic level showing higher concentrations in spider mites feeding on primary leaves (429.8 ppm) than those feeding on terminal trifoliate leaves (298.2 ppm). Concentrations of linamarin in the predatory mites were 18.4 and 71.9 ppm when feeding on spider mites grown on primary and terminal leaves, respectively. The concentration of lotaustralin in primary lima bean leaves was 103.12 ppm, and in spider mites feeding on these leaves was 175.0 ppm. Lotaustralin was absent in lima bean terminal trifoliate leaves and in mites feeding on these leaves. Fecundity of spider mites feeding on lima bean leaves (primary or trifoliate) was not significantly different from mites feeding on red bean, Phaseolus vulgaris L., primary leaves. However, the progeny sex ratio (in females per male) of spider mites feeding on lima bean leaves was significantly lower than progeny of spider mites feeding on red bean leaves (control). Fecundity and progeny sex ratio of P. persimilis were both significantly affected by the concentration of linamarin present in the prey. Changes in concentration of linamarin in living tissue across the three trophic levels are discussed.

  15. Multispecies interactions across trophic levels at macroscales: retrospective and future directions

    NARCIS (Netherlands)

    Kissling, W.D.; Schleuning, M.

    2015-01-01

    Trophic interactions among multiple species are ubiquitous in nature and their importance for structuring ecological communities has been extensively demonstrated at local spatial scales. However, how local species interactions scale-up to large spatial scales and how they contribute to shape

  16. Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system.

    Science.gov (United States)

    Scharler, U M; Ulanowicz, R E; Fogel, M L; Wooller, M J; Jacobson-Meyers, M E; Lovelock, C E; Feller, I C; Frischer, M; Lee, R; McKee, K; Romero, I C; Schmit, J P; Shearer, C

    2015-11-01

    Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

  17. Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system

    Science.gov (United States)

    Scharler, U.M.; Ulanowicz, Robert E.; Fogel, M.L.; Wooller, M.J.; Jacobson-Meyers, M.E.; Lovelock, C.E.; Feller, I.C.; Frischer, M.; Lee, R.; Mckee, Karen L.; Romero, I.C.; Schmit, J.P.; Shearer, C.

    2015-01-01

    Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

  18. Impacts of an invasive tree across trophic levels: species richness, community composition and resident species’ traits

    Czech Academy of Sciences Publication Activity Database

    Hejda, Martin; Hanzelka, J.; Kadlec, T.; Štrobl, M.; Pyšek, Petr

    2017-01-01

    Roč. 23, č. 9 (2017), s. 997-1007 ISSN 1366-9516 R&D Projects: GA ČR GB14-36079G; GA ČR(CZ) GA14-21715S Grant - others:AV ČR(CZ) AP1002 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:67985939 Keywords : invasions * impact * trophic level Subject RIV: EH - Ecology, Behaviour OBOR OECD: Biodiversity conservation Impact factor: 4.391, year: 2016

  19. Multi-trophic resilience of boreal lake ecosystems to forest fires.

    Science.gov (United States)

    Lewis, Tyler L; Lindberg, Mark S; Schmutz, Joel A; Bertram, Mark R

    2014-05-01

    Fires are the major natural disturbance in the boreal forest, and their frequency and intensity will likely increase as the climate warms. Terrestrial nutrients released by fires may be transported to boreal lakes, stimulating increased primary productivity, which may radiate through multiple trophic levels. Using a before-after-control-impact (BACI) design, with pre- and postfire data from burned and unburned areas, we examined effects of a natural fire across several trophic levels of boreal lakes, from nutrient and chlorophyll levels, to macroinvertebrates, to waterbirds. Concentrations of total nitrogen and phosphorus were not affected by the fire. Chlorophyll a levels were also unaffected, likely reflecting the stable nutrient concentrations. For aquatic invertebrates, we found that densities of three functional feeding groups did not respond to the fire (filterers, gatherers, scrapers), while two groups increased (shredders, predators). Amphipods accounted for 98% of shredder numbers, and we hypothesize that fire-mediated habitat changes may have favored their generalist feeding and habitat ecology. This increase in amphipods may, in turn, have driven increased predator densities, as amphipods were the most numerous invertebrate in our lakes and are commonly taken as prey. Finally, abundance of waterbird young, which feed primarily on aquatic invertebrates, was not affected by the fire. Overall, ecosystems of our study lakes were largely resilient to forest fires, likely due to their high initial nutrient concentrations and small catchment sizes. Moreover, this resilience spanned multiple trophic levels, a significant result for ecologically similar boreal regions, especially given the high potential for increased fires with future climate change.

  20. Feeding habits and trophic level of the Panama grunt Pomadasys panamensis, an important bycatch species from the shrimp trawl fishery in the Gulf of California

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Preciado, Jose A.; Amezcua-Martinez, Felipe; Bellgraph, Brian J.; Madrid-Vera, Juan

    2014-10-14

    The Panama grunt is an abundant and commercially important species in the SE Gulf of California, but the research undertaken on this species is scarce despite its ecological and economic importance. We studied the feeding habits of Panama grunt through stomach content analyses as a first step towards understanding the biology of this species in the study area. Our results show that the Panama grunt is a benthic predator throughout its life cycle and feeds mainly on infaunal crustaceans. Diet differences were not found according to size, diet or season. Shannon diversity index results indicate that Panama grunt have a limited trophic niche breadth with a diet dominated by a limited number of taxa. The estimated trophic level of this species is 3.59. Overall, the Panama grunt is a carnivorous fish occupying the intermediate levels of the trophic pyramid.

  1. Productivity, trophic levels and size spectra of zooplankton in northern Norwegian shelf regions

    Science.gov (United States)

    Zhou, Meng; Tande, Kurt S.; Zhu, Yiwu; Basedow, Sünnje

    2009-10-01

    Many studies have been conducted in northern Norwegian shelf regions to assess distributions and abundances of zooplankton in the last decade using towed Scanfish-conductivity, temperature and depth sensors (CTD)-optical plankton counter (OPC), and plankton nets. Significant progresses have been made in understanding dominant species, life histories and behavior, and in using size-structured data to identify dominant species in a certain size range. Using these Scanfish-CTD-OPC data, the analysis of zooplankton community size structures, compositions and their relationships with water types is made along the shelf region from Lofoten, North Cape to Varangerfjorden. From the relationships between the water types and zooplankton communities, the transports and exchanges of zooplankton communities between the Norwegian Coastal and Norwegian Atlantic Waters in regions near Malangsgrunnen and Nordvestbanken are examined. The biovolume (biomass) spectra are further analyzed for the productivity, trophic levels and seasonality of communities in these regions, indicating a steeper slope of the biovolume spectrum for a community dominated by herbivorous species in spring and a flatter slope for a community dominated by carnivorous-omnivorous species in winter. The comparison with the zooplankton biovolume spectra obtained in areas west of Antarctic Peninsula is made to examine and understand the differences in the zooplankton biovolume spectra, their trophic dynamics and potential human impacts between different regions.

  2. Global fishery development patterns are driven by profit but not trophic level.

    Science.gov (United States)

    Sethi, Suresh A; Branch, Trevor A; Watson, Reg

    2010-07-06

    Successful ocean management needs to consider not only fishing impacts but drivers of harvest. Consolidating post-1950 global catch and economic data, we assess which attributes of fisheries are good indicators for fishery development. Surprisingly, year of development and economic value are not correlated with fishery trophic levels. Instead, patterns emerge of profit-driven fishing for attributes related to costs and revenues. Post-1950 fisheries initially developed on shallow ranging species with large catch, high price, and big body size, and then expanded to less desirable species. Revenues expected from developed fisheries declined 95% from 1951 to 1999, and few high catch or valuable fishing opportunities remain. These results highlight the importance of economic attributes of species as leading indicators for harvest-related impacts in ocean ecosystems.

  3. Salinization triggers a trophic cascade in experimental freshwater communities with varying food-chain length.

    Science.gov (United States)

    Hintz, William D; Mattes, Brian M; Schuler, Matthew S; Jones, Devin K; Stoler, Aaron B; Lind, Lovisa; Relyea, Rick A

    2017-04-01

    The application of road deicing salts in northern regions worldwide is changing the chemical environment of freshwater ecosystems. Chloride levels in many lakes, streams, and wetlands exceed the chronic and acute thresholds established by the United States and Canada for the protection of freshwater biota. Few studies have identified the impacts of deicing salts in stream and wetland communities and none have examined impacts in lake communities. We tested how relevant concentrations of road salt (15, 100, 250, 500, and 1000 mg Cl - /L) interacted with experimental communities containing two or three trophic levels (i.e., no fish vs. predatory fish). We hypothesized that road salt and fish would have a negative synergistic effect on zooplankton, which would then induce a trophic cascade. We tested this hypothesis in outdoor mesocosms containing filamentous algae, periphyton, phytoplankton, zooplankton, several macroinvertebrate species, and fish. We found that the presence of fish and high salt had a negative synergistic effect on the zooplankton community, which in turn caused an increase in phytoplankton. Contributing to the magnitude of this trophic cascade was a direct positive effect of high salinity on phytoplankton abundance. Cascading effects were limited with respect to impacts on the benthic food web. Periphyton and snail grazers were unaffected by the salt-induced trophic cascade, but the biomass of filamentous algae decreased as a result of competition with phytoplankton for light or nutrients. We also found direct negative effects of high salinity on the biomass of filamentous algae and amphipods (Hyalella azteca) and the mortality of banded mystery snails (Viviparus georgianus) and fingernail clams (Sphaerium simile). Clam mortality was dependent on the presence of fish, suggesting a non-consumptive interactive effect with salt. Our results indicate that globally increasing concentrations of road salt can alter community structure via both direct

  4. Feeding Habits and Trophic Level of the Panama Grunt Pomadasys panamensis, an Important Bycatch Species from the Shrimp Trawl Fishery in the Gulf of California

    Directory of Open Access Journals (Sweden)

    José A. Rodríguez-Preciado

    2014-01-01

    Full Text Available The Panama grunt is an abundant and commercially important species in the southeastern Gulf of California, but the research undertaken on this species is scarce despite its ecological and economic importance. We studied the feeding habits of Panama grunt through stomach content analyses as a first step towards understanding the biology of this species in the study area. Our results indicate that the Panama grunt is a benthic predator throughout its life cycle and feeds mainly on infaunal crustaceans. Diet differences among grunt were not found according to size, diet, or season. Shannon diversity index results indicate that Panama grunt has a limited trophic niche breadth with a diet dominated by a limited number of taxa as crustaceans. The estimated trophic level of this species is 3.59. Overall, the Panama grunt is a carnivorous fish occupying the intermediate levels of the trophic pyramid.

  5. Feeding habits and trophic level of the Panama grunt Pomadasys panamensis, an important bycatch species from the shrimp trawl fishery in the Gulf of California.

    Science.gov (United States)

    Rodríguez-Preciado, José A; Amezcua, Felipe; Bellgraph, Brian; Madrid-Vera, Juan

    2014-01-01

    The Panama grunt is an abundant and commercially important species in the southeastern Gulf of California, but the research undertaken on this species is scarce despite its ecological and economic importance. We studied the feeding habits of Panama grunt through stomach content analyses as a first step towards understanding the biology of this species in the study area. Our results indicate that the Panama grunt is a benthic predator throughout its life cycle and feeds mainly on infaunal crustaceans. Diet differences among grunt were not found according to size, diet, or season. Shannon diversity index results indicate that Panama grunt has a limited trophic niche breadth with a diet dominated by a limited number of taxa as crustaceans. The estimated trophic level of this species is 3.59. Overall, the Panama grunt is a carnivorous fish occupying the intermediate levels of the trophic pyramid.

  6. Element patterns in albatrosses and petrels: Influence of trophic position, foraging range, and prey type

    International Nuclear Information System (INIS)

    Anderson, O.R.J.; Phillips, R.A.; Shore, R.F.; McGill, R.A.R.; McDonald, R.A.; Bearhop, S.

    2010-01-01

    We investigated the concentrations of 22 essential and non-essential elements among a community of Procellariiformes (and their prey) to identify the extent to which trophic position and foraging range governed element accumulation. Stable isotope analysis (SIA) was used to characterise trophic (δ 15 N) and spatial patterns (δ 13 C) among species. Few consistent patterns were observed in element distributions among species and diet appeared to be highly influential in some instances. Arsenic levels in seabird red blood cells correlated with δ 15 N and δ 13 C, demonstrating the importance of trophic position and foraging range for arsenic distribution. Arsenic concentrations in prey varied significantly across taxa, and in the strength of association with δ 15 N values (trophic level). In most instances, element patterns in Procellariiformes showed the clearest separation among species, indicating that a combination of prey selection and other complex species-specific characteristics (e.g. moult patterns) were generally more important determining factors than trophic level per se. - Trophic position, foraging range, and prey type were found to influence element compositions and concentrations in Procellariiformes from South Georgia.

  7. Biomass changes and trophic amplification of plankton in a warmer ocean

    KAUST Repository

    Chust, Guillem; Allen, Julian Icarus; Bopp, Laurent; Schrum, Corinna; Holt, Jason T.; Tsiaras, Kostas P.; Zavatarelli, Marco; Chifflet, Marina; Cannaby, Heather; Dadou, Isabelle C.; Daewel, Ute; Wakelin, Sarah L.; Machú , Eric; Pushpadas, Dhanya; Butenschö n, Momme; Artioli, Yuri; Petihakis, George; Smith, Chris J M; Garç on, Vé ronique C.; Goubanova, Katerina; Le Vu, Briac; Fach, Bettina A.; Salihoglu, Baris; Clementi, Emanuela; Irigoien, Xabier

    2014-01-01

    Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and

  8. Biomass changes and trophic amplification of plankton in a warmer ocean

    KAUST Repository

    Chust, Guillem

    2014-05-07

    Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and

  9. Biomass changes and trophic amplification of plankton in a warmer ocean.

    Science.gov (United States)

    Chust, Guillem; Allen, J Icarus; Bopp, Laurent; Schrum, Corinna; Holt, Jason; Tsiaras, Kostas; Zavatarelli, Marco; Chifflet, Marina; Cannaby, Heather; Dadou, Isabelle; Daewel, Ute; Wakelin, Sarah L; Machu, Eric; Pushpadas, Dhanya; Butenschon, Momme; Artioli, Yuri; Petihakis, George; Smith, Chris; Garçon, Veronique; Goubanova, Katerina; Le Vu, Briac; Fach, Bettina A; Salihoglu, Baris; Clementi, Emanuela; Irigoien, Xabier

    2014-07-01

    Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and

  10. Economic growth and marine biodiversity: influence of human social structure on decline of marine trophic levels.

    Science.gov (United States)

    Clausen, Rebecca; York, Richard

    2008-04-01

    We assessed the effects of economic growth, urbanization, and human population size on marine biodiversity. We used the mean trophic level (MTL) of marine catch as an indicator of marine biodiversity and conducted cross-national time-series analyses (1960-2003) of 102 nations to investigate human social influences on fish catch and trends in MTL. We constructed path models to examine direct and indirect effects relating to marine catch and MTL. Nations' MTLs declined with increased economic growth, increased urbanization, and increased population size, in part because of associated increased catch. These findings contradict the environmental Kuznets curve hypothesis, which claims that economic modernization will reduce human impact on the environment. To make informed decisions on issues of marine resource management, policy makers, nonprofit entities, and professional societies must recognize the need to include social analyses in overall conservation-research strategies. The challenge is to utilize the socioeconomic and ecological research in the service of a comprehensive marine-conservation movement.

  11. Multiple attractors and boundary crises in a tri-trophic food chain.

    NARCIS (Netherlands)

    Boer, M.P.; Kooi, B.W.; Kooijman, S.A.L.M.

    2001-01-01

    The asymptotic behaviour of a model of a tri-trophic food chain in the chemostat is analysed in detail. The Monod growth model is used for all trophic levels, yielding a non-linear dynamical system of four ordinary differential equations. Mass conservation makes it possible to reduce the dimension

  12. Trophic strategies of unicellular plankton

    DEFF Research Database (Denmark)

    Chakraborty, Subhendu; Nielsen, Lasse Tor; Andersen, Ken Haste

    2017-01-01

    . To this end, we develop and calibrate a trait-based model for unicellular planktonic organisms characterized by four traits: cell size and investments in phototrophy, nutrient uptake, and phagotrophy. We use the model to predict how optimal trophic strategies depend on cell size under various environmental...... unicellulars are colimited by organic carbon and nutrients, and only large photoautotrophs and smaller mixotrophs are nutrient limited; (2) trophic strategy is bottom-up selected by the environment, while optimal size is top-down selected by predation. The focus on cell size and trophic strategies facilitates......Unicellular plankton employ trophic strategies ranging from pure photoautotrophs over mixotrophy to obligate heterotrophs (phagotrophs), with cell sizes from 10-8 to 1 μg C. A full understanding of how trophic strategy and cell size depend on resource environment and predation is lacking...

  13. Trophic transfer of pyrene metabolites between aquatic invertebrates

    International Nuclear Information System (INIS)

    Carrasco Navarro, V.; Leppänen, M.T.; Kukkonen, J.V.K.; Godoy Olmos, S.

    2013-01-01

    The trophic transfer of pyrene metabolites was studied using Gammarus setosus as a predator and the invertebrates Lumbriculus variegatus and Chironomus riparius as prey. The results obtained by liquid scintillation counting confirmed that the pyrene metabolites produced by the aquatic invertebrates L. variegatus and C. riparius were transferred to G. setosus through the diet. More detailed analyses by liquid chromatography discovered that two of the metabolites produced by C. riparius appeared in the chromatograms of G. setosus tissue extracts, proving their trophic transfer. These metabolites were not present in chromatograms of G. setosus exclusively exposed to pyrene. The present study supports the trophic transfer of PAH metabolites between benthic macroinvertebrates and common species of an arctic amphipod. As some PAH metabolites are more toxic than the parent compounds, the present study raises concerns about the consequences of their trophic transfer and the fate and effects of PAHs in natural environments. - Highlights: ► The trophic transfer of pyrene metabolites between invertebrates was evaluated. ► Biotransformation of pyrene by L. variegatus and C. riparius is different. ► Metabolites produced by L. variegatus and C. riparius are transferred to G. setosus. ► Specifically, two metabolites produced by C. riparius were transferred. - Some of the pyrene metabolites produced by the model invertebrates L. variegatus and C. riparius are transferred to G. setosus through the diet, proving their trophic transfer.

  14. Behavioural and physiological responses of limpet prey to a seastar predator and their transmission to basal trophic levels.

    Science.gov (United States)

    Manzur, Tatiana; Vidal, Francisco; Pantoja, José F; Fernández, Miriam; Navarrete, Sergio A

    2014-07-01

    Besides the well-documented behavioural changes induced by predators on prey, predator-induced stress can also include a suite of biochemical, neurological and metabolic changes that may represent important energetic costs and have long-lasting effects on individuals and on the demography of prey populations. The rapid transmission of prey behavioural changes to lower trophic levels, usually associated with alteration of feeding rates, can substantially change and even reverse direction over the long term as prey cope with the energetic costs associated with predation-induced stress. It is therefore critical to evaluate different aspects and assess the costs of non-consumptive predator effects on prey. We investigated the behavioural and physiological responses of an herbivorous limpet, Fissurella limbata, to the presence of chemical cues and direct non-lethal contact by the common seastar predator, Heliaster helianthus. We also evaluated whether the limpets feeding behaviour was modified by the predator and whether this translated into positive or negative effects on biomass of the green alga, Ulva sp. Our experimental results show the presence of Heliaster led to increased movement activity, increased distances travelled, changes in time budget over different environmental conditions and increased feeding rate in the keyhole limpets. Moreover, additional experiments showed that, beyond the increased metabolic rate associated with limpet increased activity, predator chemical cues heighten metabolic rate as part of the induced stress response. Changes in individual movement and displacement distances observed through the 9-day experiment can be interpreted as part of the escape response exhibited by limpets to reduce the risk of being captured by the predator. Increased limpet feeding rate on algae can be visualized as a way individuals compensate for the elevated energetic costs of movement and heightened metabolic rates produced by the predator-induced stress

  15. CNCM I-745 Improves Intestinal Enzyme Function: A Trophic Effects Review

    Directory of Open Access Journals (Sweden)

    Margret I Moré

    2018-02-01

    Full Text Available Several properties of the probiotic medicinal yeast Saccharomyces boulardii CNCM I-745 contribute to its efficacy to prevent or treat diarrhoea. Besides immunologic effects, pathogen-binding and anti-toxin effects, as well as positive effects on the microbiota, S boulardii CNCM I-745 also has pronounced effects on digestive enzymes of the brush border membrane, known as trophic effects. The latter are the focus of this review. Literature has been reviewed after searching Medline and PMC databases. All relevant non-clinical and clinical studies are summarized. S. boulardii CNCM I-745 synthesizes and secretes polyamines, which have a role in cell proliferation and differentiation. The administration of polyamines or S. boulardii CNCM I-745 enhances the expression of intestinal digestive enzymes as well as nutrient uptake transporters. The signalling mechanisms leading to enzyme activation are not fully understood. However, polyamines have direct nucleic acid–binding capacity with regulatory impact. S. boulardii CNCM I-745 induces signalling via the mitogen-activated protein kinase pathway. In addition, effects on the phosphatidylinositol-3 kinase (PI3K pathway have been reported. As an additional direct effect, S. boulardii CNCM I-745 secretes certain enzymes, which enhance nutrient acquisition for the yeast and the host. The increased availability of digestive enzymes seems to be one of the mechanisms by which S. boulardii CNCM I-745 counteracts diarrhoea; however, also people with certain enzyme deficiencies may profit from its administration. More studies are needed to fully understand the mechanisms of trophic activation by the probiotic yeast.

  16. PBDEs and other POPs in urban birds of prey partly explained by trophic level and carbon source

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, John E. [Environment Canada, Science & Technology Branch, Pacific Wildlife Research Centre, Delta, British Columbia V4K 3N2 (Canada); Department of Biological Science, Simon Fraser University, Burnaby, BC V5A 1S6 (Canada); Brogan, Jason [Department of Biological Science, Simon Fraser University, Burnaby, BC V5A 1S6 (Canada); Lee, Sandi L. [Environment Canada, Science & Technology Branch, Pacific Wildlife Research Centre, Delta, British Columbia V4K 3N2 (Canada); Drouillard, Ken G. [Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON N9B 3P4 (Canada); Elliott, Kyle H. [Department of Natural Resource Sciences, McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9 (Canada)

    2015-08-15

    As urban sprawl and agricultural intensification continue to invade prime wildlife habitat, some animals, even apex predators, are managing to adapt to this new environment. Chemical pollution is one of many stressors that wildlife encounter in urban environments. Predators are particularly sensitive to persistent chemical pollutants because they feed at a high trophic level where such pollution is biomagnified. To examine levels of pollution in urban birds of prey in the Lower Mainland region of British Columbia, Canada, we analyzed persistent organic contaminants in adult birds found dead of trauma injury. The hepatic geometric mean concentration of sum polybrominated diphenyl ethers (∑PBDEs) in 13 Cooper's hawks (Accipiter cooperii) from Greater Vancouver was 1873 ng/g (lipid weight) with one bird reaching 197,000 ng/g lipid weight, the highest exposure reported to date for a wild bird. Concentrations of ∑PBDEs, ∑PCBs (polychlorinated biphenyls) and, surprisingly, cyclodiene insecticides were greatest in the urban environment while those of DDE (1,1-dichloroethylene bis[p-chlorophenyl) were highest in a region of intensive agriculture. The level of most chlorinated and brominated contaminants increased with trophic level (δ{sup 15}N). The concentrations of some contaminants, PBDEs in particular, in these birds of prey may have some toxicological consequences. Apex predators in urban environments continue to be exposed to elevated concentrations of legacy pollutants as well as more recent brominated pollutants. - Highlights: • As urban areas expand, many animal species are adapting and invading urban areas. • Urban colonists encounter many new stressors, especially chemical pollution. • Urban birds of prey in Canada had high levels of brominated flame retardants (PBDEs). • One individual had the highest level of PBDEs ever recorded for wildlife. • Such high levels may have had toxicological implications.

  17. PBDEs and other POPs in urban birds of prey partly explained by trophic level and carbon source

    International Nuclear Information System (INIS)

    Elliott, John E.; Brogan, Jason; Lee, Sandi L.; Drouillard, Ken G.; Elliott, Kyle H.

    2015-01-01

    As urban sprawl and agricultural intensification continue to invade prime wildlife habitat, some animals, even apex predators, are managing to adapt to this new environment. Chemical pollution is one of many stressors that wildlife encounter in urban environments. Predators are particularly sensitive to persistent chemical pollutants because they feed at a high trophic level where such pollution is biomagnified. To examine levels of pollution in urban birds of prey in the Lower Mainland region of British Columbia, Canada, we analyzed persistent organic contaminants in adult birds found dead of trauma injury. The hepatic geometric mean concentration of sum polybrominated diphenyl ethers (∑PBDEs) in 13 Cooper's hawks (Accipiter cooperii) from Greater Vancouver was 1873 ng/g (lipid weight) with one bird reaching 197,000 ng/g lipid weight, the highest exposure reported to date for a wild bird. Concentrations of ∑PBDEs, ∑PCBs (polychlorinated biphenyls) and, surprisingly, cyclodiene insecticides were greatest in the urban environment while those of DDE (1,1-dichloroethylene bis[p-chlorophenyl) were highest in a region of intensive agriculture. The level of most chlorinated and brominated contaminants increased with trophic level (δ 15 N). The concentrations of some contaminants, PBDEs in particular, in these birds of prey may have some toxicological consequences. Apex predators in urban environments continue to be exposed to elevated concentrations of legacy pollutants as well as more recent brominated pollutants. - Highlights: • As urban areas expand, many animal species are adapting and invading urban areas. • Urban colonists encounter many new stressors, especially chemical pollution. • Urban birds of prey in Canada had high levels of brominated flame retardants (PBDEs). • One individual had the highest level of PBDEs ever recorded for wildlife. • Such high levels may have had toxicological implications

  18. Inhibition of predator attraction to kairomones by non-host plant volatiles for herbivores: a bypass-trophic signal.

    Directory of Open Access Journals (Sweden)

    Qing-He Zhang

    2010-06-01

    Full Text Available Insect predators and parasitoids exploit attractive chemical signals from lower trophic levels as kairomones to locate their herbivore prey and hosts. We hypothesized that specific chemical cues from prey non-hosts and non-habitats, which are not part of the trophic chain, are also recognized by predators and would inhibit attraction to the host/prey kairomone signals. To test our hypothesis, we studied the olfactory physiology and behavior of a predaceous beetle, Thanasimus formicarius (L. (Coleoptera: Cleridae, in relation to specific angiosperm plant volatiles, which are non-host volatiles (NHV for its conifer-feeding bark beetle prey.Olfactory detection in the clerid was confirmed by gas chromatography coupled to electroantennographic detection (GC-EAD for a subset of NHV components. Among NHV, we identified two strongly antennally active molecules, 3-octanol and 1-octen-3-ol. We tested the potential inhibition of the combination of these two NHV on the walking and flight responses of the clerid to known kairomonal attractants such as synthetic mixtures of bark beetle (Ips spp. aggregation pheromone components (cis-verbenol, ipsdienol, and E-myrcenol combined with conifer (Picea and Pinus spp. monoterpenes (alpha-pinene, terpinolene, and Delta(3-carene. There was a strong inhibitory effect, both in the laboratory (effect size d = -3.2, walking bioassay and in the field (d = -1.0, flight trapping. This is the first report of combining antennal detection (GC-EAD and behavioral responses to identify semiochemical molecules that bypass the trophic system, signaling habitat information rather than food related information.Our results, along with recent reports on hymenopteran parasitoids and coleopteran predators, suggest that some NHV chemicals for herbivores are part of specific behavioral signals for the higher trophic level and not part of a background noise. Such bypass-trophic signals could be of general importance for third trophic level

  19. Species richness and trophic diversity increase decomposition in a co-evolved food web.

    Directory of Open Access Journals (Sweden)

    Benjamin Baiser

    Full Text Available Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.

  20. Ecomorphological patterns of the fish assemblage in a tropical floodplain: effects of trophic, spatial and phylogenetic structures

    Directory of Open Access Journals (Sweden)

    Edson Fontes Oliveira

    Full Text Available Ecomorphological patterns of the fish assemblage from the upper Paraná River floodplain, Brazil, were described and evaluated according to trophic (guilds, spatial (habitats and phylogenetic (taxonomic distances structures. The samples were obtained through the Long Term Research Project (LTER-CNPq/UEM/NUPELIA in August and October 2001. Thirty-five species were analyzed from thirty-one morphological variables. Strong significant correlations (Mantel test between morphology and trophic guilds and between morphology and taxonomy were found, while morphology and habitat revealed a weak correlation. However, the partial Mantel test showed that the correlations between morphology and trophic guilds persist even when the effect of taxonomy is discounted. The ecomorphological pattern shown by the Principal Component Analysis separated species according to locomotion structures used in feeding. At one extreme there are the piscivores and insectivores that exploit lentic habitats and have compressed bodies and well developed anal fins, while at the other there are detritivores and invertivores that exploit lotic and semi-lotic habitats and have depressed bodies and well developed pectoral, pelvic and caudal fins. Canonical Discriminant Analysis using ecomorphological variables successfully predicted 94.5% of the trophic guild ecomorphotypes, but only 57.1% of the habitat ecomorphotypes. These data indicate that the fish assemblage of the upper Paraná River floodplain is structured ecomorphologically mainly according to trophic structure rather than habitat.

  1. Chemical composition and trophic state of shallow saline steppe lakes in central Asia (North Kazakhstan).

    Science.gov (United States)

    Boros, Emil; Jurecska, Laura; Tatár, Enikő; Vörös, Lajos; Kolpakova, Marina

    2017-10-09

    The purpose of this study was to identify the prevailing chemical composition and trophic state of the shallow saline steppe lakes of North Kazakhstan along a wide size range (SO 4 and Na-Cl (n = 16; 64%); the Ca, Mg, HCO 3 , and SO 4 ions precipitate with increasing salinity (2-322 g L -1 ); and ion composition shifts from Na>Mg-Cl>SO 4 to Na-Cl. The most of the chemical variables positively, but chlorophyll a negatively, correlated with total dissolved solids, and the total phosphorus had no significant correlation with any variables. The trophic state of these lakes in most cases exceeded the hypertrophic level. The increase in salinity causes change in chemical composition and effects on the phytoplankton development independently from the size of water surface, and the human disturbances had negligible effect on the trophic state of shallow saline lakes in this region of Kazakhstan.

  2. Quantifying Trophic Interactions and Carbon Flow in Louisiana Salt Marshes Using Multiple Biomarkers

    Science.gov (United States)

    Polito, M. J.; Lopez-Duarte, P. C.; Olin, J.; Johnson, J. J.; Able, K.; Martin, C. W.; Fodrie, J.; Hooper-Bui, L. M.; Taylor, S.; Stouffer, P.; Roberts, B. J.; Rabalais, N. N.; Jensen, O.

    2017-12-01

    Salt marshes are critical habitats for many species in the northern Gulf of Mexico. However, given their complex nature, quantifying trophic linkages and the flow of carbon through salt marsh food webs is challenging. This gap in our understanding of food web structure and function limits our ability to evaluate the impacts of natural and anthropogenic stressors on salt marsh ecosystems. For example, 2010 Deepwater Horizon (DWH) oil spill had the potential to alter trophic and energy pathways. Even so, our ability to evaluate its effects on Louisiana salt marsh food webs was limited by a poor basis for comparison of the pre-spill baseline food web. To be better equipped to measure significant alterations in salt marsh ecosystems in the future, we quantified trophic interactions at two marsh sites in Barataria Bay, LA in May and October of 2015. Trophic structure and carbon flow across 52 species of saltmarsh primary producers and consumers were examined through a combination of three approaches: bulk tissue stable isotope analysis (δ13C, δ15N, δ34S), dietary fatty acid analysis (FAA), and compound-specific stable isotope analysis of essential amino acids (δ13C EAA). Bulk stable isotope analysis indicated similar trophic diversity between sites and seasons with the use of aquatic resources increasing concomitantly with trophic level. FAA and δ13C EAA biomarkers revealed that marsh organisms were largely divided into two groups: those that primarily derive carbon from terrestrial C4 grasses, and those that predominately derive carbon from a combination of phytoplankton and benthic microalgal sources. Differences in trophic structure and carbon flow were minimal between seasons and sites that were variably impacted by the DWH spill. These data on salt marsh ecosystem structure will be useful to inform future injury assessments and restoration initiatives.

  3. A trophic model of fringing coral reefs in Nanwan Bay, southern Taiwan suggests overfishing.

    Science.gov (United States)

    Liu, Pi-Jen; Shao, Kwang-Tsao; Jan, Rong-Quen; Fan, Tung-Yung; Wong, Saou-Lien; Hwang, Jiang-Shiou; Chen, Jen-Ping; Chen, Chung-Chi; Lin, Hsing-Juh

    2009-09-01

    Several coral reefs of Nanwan Bay, Taiwan have recently undergone shifts to macroalgal or sea anemone dominance. Thus, a mass-balance trophic model was constructed to analyze the structure and functioning of the food web. The fringing reef model was comprised of 18 compartments, with the highest trophic level of 3.45 for piscivorous fish. Comparative analyses with other reef models demonstrated that Nanwan Bay was similar to reefs with high fishery catches. While coral biomass was not lower, fish biomass was lower than those of reefs with high catches. Consequently, the sums of consumption and respiratory flows and total system throughput were also decreased. The Nanwan Bay model potentially suggests an overfished status in which the mean trophic level of the catch, matter cycling, and trophic transfer efficiency are extremely reduced.

  4. Invasive ants compete with and modify the trophic ecology of hermit crabs on tropical islands.

    Science.gov (United States)

    McNatty, Alice; Abbott, Kirsti L; Lester, Philip J

    2009-05-01

    Invasive species can dramatically alter trophic interactions. Predation is the predominant trophic interaction generally considered to be responsible for ecological change after invasion. In contrast, how frequently competition from invasive species contributes to the decline of native species remains controversial. Here, we demonstrate how the trophic ecology of the remote atoll nation of Tokelau is changing due to competition between invasive ants (Anoplolepis gracilipes) and native terrestrial hermit crabs (Coenobita spp.) for carrion. A significant negative correlation was observed between A. gracilipes and hermit crab abundance. On islands with A. gracilipes, crabs were generally restricted to the periphery of invaded islands. Very few hermit crabs were found in central areas of these islands where A. gracilipes abundances were highest. Ant exclusion experiments demonstrated that changes in the abundance and distribution of hermit crabs on Tokelau are a result of competition. The ants did not kill the hermit crabs. Rather, when highly abundant, A. gracilipes attacked crabs by spraying acid and drove crabs away from carrion resources. Analysis of naturally occurring N and C isotopes suggests that the ants are effectively lowering the trophic level of crabs. According to delta(15) N values, hermit crabs have a relatively high trophic level on islands where A. gracilipes have not invaded. In contrast, where these ants have invaded we observed a significant decrease in delta(15) N for all crab species. This result concurs with our experiment in suggesting long-term exclusion from carrion resources, driving co-occurring crabs towards a more herbivorous diet. Changes in hermit crab abundance or distribution may have major ramifications for the stability of plant communities. Because A. gracilipes have invaded many tropical islands where the predominant scavengers are hermit crabs, we consider that their competitive effects are likely to be more prominent in

  5. 210Po and 210Pb in a pelagic trophic chain

    International Nuclear Information System (INIS)

    Radakovitch, O.; Strady, E.; Veron, A.; Chiffoleau, J.F.; Tronczynski, J.; Harmelin-Vivien, M.

    2013-01-01

    The ANR-COSTAS program studied the bioaccumulation and biomagnification of organic and inorganic contaminants through the trophic chains of two small pelagic fish, anchovy and sardine, on the continental shelf of the Gulf of Lion (Northwestern Mediterranean Sea). 210 Po and 210 Pb were analysed at various levels of this trophic chain, as well as trace metal elements, lead isotopes and C and N isotopes which provide additional information on both biogeochemical cycles and trophic transfer. To our knowledge, this is the first time that an entire trophic chain is analysed for these two radionuclides. Water, suspended particles, phytoplankton and zooplankton were collected at 7 stations during two contrast seasons. Phyto and zooplankton were separated in 6 classes through size-sieving: 6-60 μm; 60-200; 200-500; 500-1000; 1000-2000 and > 2000 μm. Anchovy and sardine were collected also two times and analyses were performed on muscle and liver independently for both sexes

  6. The trophic effect of ouabain on retinal ganglion cells is mediated by IL-1β and TNF-α

    International Nuclear Information System (INIS)

    Salles von-Held-Ventura, Juliana; Mázala-de-Oliveira, Thalita; Cândida da Rocha Oliveira, Amanda; Granja, Marcelo Gomes; Gonçalves-de-Albuquerque, Cassiano Felippe; Castro-Faria-Neto, Hugo Caire; Giestal-de-Araujo, Elizabeth

    2016-01-01

    Ouabain is a steroid hormone that binds to the enzyme Na + , K + – ATPase and stimulates different intracellular pathways controlling growth, proliferation and cell survival. IL-1β and TNF-α are pleiotropic molecules, conventionally regarded as pro-inflammatory cytokines with well-known effects in the immune system. In addition, IL-1β and TNF-α also play important roles in the nervous system including neuroprotective effects. Previous data from our group showed that ouabain treatment is able to induce an increase in retinal ganglion cell survival kept in mixed retinal cell cultures. The aim of this work was to investigate if IL-1β and TNF-α could be mediating the trophic effect of ouabain on retinal ganglion cells. Our results show that the trophic effect of ouabain on retinal ganglion cell was inhibited by either anti-IL-1β or anti-TNF-α antibodies. In agreement, IL-1β or TNF-α increased the retinal ganglion cells survival in a dose-dependent manner. Accordingly, ouabain treatment induces a temporal release of TNF-α and IL-1β from retinal cell cultures. Interestingly, TNF-α and IL-1β regulate each other intracellular levels. Our results suggest that ouabain treatment triggers the activation of TNF-α and IL-1β signaling pathways leading to an increase in retinal ganglion cell survival. - Highlights: • Pro-inflammatory cytokines regulates the ouabain effect on RGC survival. • Ouabain treatment modulates the intracellular levels of TNF-α and IL-1β. • Ouabain induces the release of TNF-α and IL-1β in retinal cell cultures.

  7. The trophic effect of ouabain on retinal ganglion cells is mediated by IL-1β and TNF-α

    Energy Technology Data Exchange (ETDEWEB)

    Salles von-Held-Ventura, Juliana; Mázala-de-Oliveira, Thalita; Cândida da Rocha Oliveira, Amanda; Granja, Marcelo Gomes [Departamento de Neurobiologia, Programa de Neurociências, Outeiro de São João Batista s/n CEP: 24020-150, Universidade Federal Fluminense, Niterói, RJ (Brazil); Gonçalves-de-Albuquerque, Cassiano Felippe; Castro-Faria-Neto, Hugo Caire [Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Departamento de Fisiologia e Farmacodinâmica, Av., no 4365, Manguinhos, 21045-900, Rio de Janeiro, RJ (Brazil); Giestal-de-Araujo, Elizabeth, E-mail: egiestal@vm.uff.br [Departamento de Neurobiologia, Programa de Neurociências, Outeiro de São João Batista s/n CEP: 24020-150, Universidade Federal Fluminense, Niterói, RJ (Brazil)

    2016-09-09

    Ouabain is a steroid hormone that binds to the enzyme Na{sup +}, K{sup +} – ATPase and stimulates different intracellular pathways controlling growth, proliferation and cell survival. IL-1β and TNF-α are pleiotropic molecules, conventionally regarded as pro-inflammatory cytokines with well-known effects in the immune system. In addition, IL-1β and TNF-α also play important roles in the nervous system including neuroprotective effects. Previous data from our group showed that ouabain treatment is able to induce an increase in retinal ganglion cell survival kept in mixed retinal cell cultures. The aim of this work was to investigate if IL-1β and TNF-α could be mediating the trophic effect of ouabain on retinal ganglion cells. Our results show that the trophic effect of ouabain on retinal ganglion cell was inhibited by either anti-IL-1β or anti-TNF-α antibodies. In agreement, IL-1β or TNF-α increased the retinal ganglion cells survival in a dose-dependent manner. Accordingly, ouabain treatment induces a temporal release of TNF-α and IL-1β from retinal cell cultures. Interestingly, TNF-α and IL-1β regulate each other intracellular levels. Our results suggest that ouabain treatment triggers the activation of TNF-α and IL-1β signaling pathways leading to an increase in retinal ganglion cell survival. - Highlights: • Pro-inflammatory cytokines regulates the ouabain effect on RGC survival. • Ouabain treatment modulates the intracellular levels of TNF-α and IL-1β. • Ouabain induces the release of TNF-α and IL-1β in retinal cell cultures.

  8. Assessing trophic linkages in and around offshore wind farms using two high-speed optical sensors

    Science.gov (United States)

    Dudeck, Tim; Hufnagl, Marc; Auch, Dominik; Eckhardt, André; Möller, Klas-Ove; van Beusekom, Justus; Walter, Bettina; Möllmann, Christian; Floeter, Jens

    2016-04-01

    In search for clean, renewable energy sources European countries have built and planned numerous Offshore Wind Farms (OWF) in the North Sea region. While some research has been carried out on their influence on marine mammals and bottom-dwelling organisms, less is known about fish and lower trophic levels in these areas. Yet, marine mammals purposely seek these structures and there are indications that there are higher chances of fish encounters. However, the local bottom-up effects probably driving these aggregations of higher trophic level organisms are poorly understood. In this study we show preliminary results of primary and secondary production in and around German OWFs in the North Sea using a Laser Optical Particle Counter and a Video Plankton Recorder. With the two sensors working simultaneously on the TRIAXUS system at high speed, we were able to investigate and ground-truth size-spectrum changes on a very high spatial resolution making it possible to detect OWF effects from local to larger scales. Our results show new possibilities in OWF research and the necessity to collect highly resolved field data for meaningful results in these dynamic environments. Furthermore, the use of size spectra simplifies the integration of energy flow through low and medium trophic levels into biogeochemical models by using only a single automatically measurable variable such as size.

  9. Fatty acid trophic markers and trophic links among seston, crustacean zooplankton and the siphonophore Nanomia cara in Georges Basin and Oceanographer Canyon (NW Atlantic

    Directory of Open Access Journals (Sweden)

    Sergio Rossi

    2008-06-01

    Full Text Available Fatty acid concentrations expressed as percentages of total fatty acid pools in seston, stage V copepodites of Calanus finmarchicus, adults of the euphausiid Meganyctiphanes norvegica, and the physonect siphonophore Nanomia cara were used to elucidate trophic links in Georges Basin and Oceanographer Canyon in September 2003. Seston at both locations was refractory and comprised mainly of saturated fatty acids. Phytoplankton did not contribute significantly to the fatty acid composition of seston or higher trophic levels. Only four fatty acids, i.e. 14:0, 16:0, 16:1 (n–7 and 18:1 (n–7, were transferred from seston to C. finmarchicus or M. norvegica, which suggested weak trophic interactions. Fatty acids transferred from the two species of crustaceans to N. cara included the same four fatty acids, along with three polyunsaturated fatty acids found in relatively high concentrations in both crustaceans, i.e. 20:3 (n–6, 20:5 (n–3 and 22:6 (n–3. In addition, 18:1 (n–9, which occurred in relatively high concentrations only in M. norvegica, and 18:0 and 18:2 (n–6, which were found in low concentrations in both crustaceans, also appeared to be transferred to N. cara. Overall, fatty acid trophic markers proved useful for identifying trophic links to N. cara.

  10. Trophic shifts of a generalist consumer in response to resource pulses.

    Directory of Open Access Journals (Sweden)

    Pei-Jen L Shaner

    2011-03-01

    Full Text Available Trophic shifts of generalist consumers can have broad food-web and biodiversity consequences through altered trophic flows and vertical diversity. Previous studies have used trophic shifts as indicators of food-web responses to perturbations, such as species invasion, and spatial or temporal subsidies. Resource pulses, as a form of temporal subsidies, have been found to be quite common among various ecosystems, affecting organisms at multiple trophic levels. Although diet switching of generalist consumers in response to resource pulses is well documented, few studies have examined if the switch involves trophic shifts, and if so, the directions and magnitudes of the shifts. In this study, we used stable carbon and nitrogen isotopes with a Bayesian multi-source mixing model to estimate proportional contributions of three trophic groups (i.e. producer, consumer, and fungus-detritivore to the diets of the White-footed mouse (Peromyscus leucopus receiving an artificial seed pulse or a naturally-occurring cicadas pulse. Our results demonstrated that resource pulses can drive trophic shifts in the mice. Specifically, the producer contribution to the mouse diets was increased by 32% with the seed pulse at both sites examined. The consumer contribution to the mouse diets was also increased by 29% with the cicadas pulse in one of the two grids examined. However, the pattern was reversed in the second grid, with a 13% decrease in the consumer contribution with the cicadas pulse. These findings suggest that generalist consumers may play different functional roles in food webs under perturbations of resource pulses. This study provides one of the few highly quantitative descriptions on dietary and trophic shifts of a key consumer in forest food webs, which may help future studies to form specific predictions on changes in trophic interactions following resource pulses.

  11. The comparative uptake and interaction of several radionuclides in the trophic levels surrounding the Los Alamos Meson Physics Facility (LAMPF) waste water ponds

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, G.H. Jr.

    1989-08-01

    A study was undertaken to examine the uptake, distribution, and interaction of five activation products (Co-57, Be-7, Cs-134, Rb-83, and Mn-54) within the biotic and abiotic components surrounding the waste treatment lagoons of the Los Alamos Meson Physics Facility (LAMPF). The study attempted to ascertain where, and what specific interactions were taking place among the isotopes and the biotic/abiotic components. A statistical approach, utilizing Multivariate Analysis of Variance (MANOVA), was conducted testing the radioisotopic concentrations by (1) the trophic levels (TROPLVL) in each position sampled on the grid, (2) where sampled on the grid (TRAN), (3) where sampled with-in each grid line (PLOT), and (4) the side with which sampled (SIDE). This provided both the dependent and independent variables that would be tested. The Null Hypothesis (Ho) tested the difference in the mean values of the isotopes within/between each of the four independent variables. The Rb-83 statistic indicated an accumulation within the TRAN and PLOT variables within the sampled area. The Co-57 test statistic provided a value which indicated that accumulation of this isotope within TROPLVL was taking place. Mn-54 test values indicated that accumulation was also taking place at the higher trophic levels within the PLOT, TRAN, and SIDE positions. Cs-134 was found to accumulate to third level in this trophic level structure (TROPLVL-(vegetation)), and then decrease from there. The Be-7 component provided no variance from known compartmental transfers. 210 refs., 17 figs., 4 tabs.

  12. The comparative uptake and interaction of several radionuclides in the trophic levels surrounding the Los Alamos Meson Physics Facility (LAMPF) waste water ponds

    International Nuclear Information System (INIS)

    Brooks, G.H. Jr.

    1989-08-01

    A study was undertaken to examine the uptake, distribution, and interaction of five activation products (Co-57, Be-7, Cs-134, Rb-83, and Mn-54) within the biotic and abiotic components surrounding the waste treatment lagoons of the Los Alamos Meson Physics Facility (LAMPF). The study attempted to ascertain where, and what specific interactions were taking place among the isotopes and the biotic/abiotic components. A statistical approach, utilizing Multivariate Analysis of Variance (MANOVA), was conducted testing the radioisotopic concentrations by (1) the trophic levels (TROPLVL) in each position sampled on the grid, (2) where sampled on the grid (TRAN), (3) where sampled with-in each grid line (PLOT), and (4) the side with which sampled (SIDE). This provided both the dependent and independent variables that would be tested. The Null Hypothesis (Ho) tested the difference in the mean values of the isotopes within/between each of the four independent variables. The Rb-83 statistic indicated an accumulation within the TRAN and PLOT variables within the sampled area. The Co-57 test statistic provided a value which indicated that accumulation of this isotope within TROPLVL was taking place. Mn-54 test values indicated that accumulation was also taking place at the higher trophic levels within the PLOT, TRAN, and SIDE positions. Cs-134 was found to accumulate to third level in this trophic level structure [TROPLVL-(vegetation)], and then decrease from there. The Be-7 component provided no variance from known compartmental transfers. 210 refs., 17 figs., 4 tabs

  13. Trophic diversity of Poznań Lakeland lakes

    Directory of Open Access Journals (Sweden)

    Dzieszko Piotr

    2015-06-01

    Full Text Available The main goal of the presented work is to determine the current trophic state of 31 lakes located in Poznań Lakeland. These lakes are included in the lake monitoring programme executed by the Voivodship Environmental Protection Inspectorate in Poznań. The place in the trophic classification for investigated lakes was determined as well as the relationships between their trophic state indices. The trophic state of investigated lakes in the research area is poor. More than a half of the investigated lakes are eutrophic. Depending on the factor that is taken into account the trophic state of investigated lakes differs radically.

  14. Variability in copepod trophic levels and feeding selectivity based on stable isotope analysis in Gwangyang Bay of the southern coast of the Korean Peninsula

    Science.gov (United States)

    Chen, Mianrun; Kim, Dongyoung; Liu, Hongbin; Kang, Chang-Keun

    2018-04-01

    Trophic preference (i.e., food resources and trophic levels) of different copepod groups was assessed along a salinity gradient in the temperate estuarine Gwangyang Bay of Korea, based on seasonal investigation of taxonomic results in 2015 and stable isotope analysis incorporating multiple linear regression models. The δ13C and δ15N values of copepods in the bay displayed significant spatial heterogeneity as well as seasonal variations, which were indicated by their significant relationships with salinity and temperature, respectively. Both spatial and temporal variations reflected those in isotopic values of food sources. The major calanoid groups (marine calanoids and brackish water calanoids) had a mean trophic level of 2.2 relative to nanoplankton as the basal food source, similar to the bulk copepod assemblage; however, they had dissimilar food sources based on the different δ13C values. Calanoid isotopic values indicated a mixture of different genera including species with high δ15N values (e.g., Labidocera, Sinocalanus, and Tortanus), moderate values (Calanus sinicus, Centropages, Paracalanus, and Acartia), and relatively low δ15N values (Eurytemora pacifica and Pseudodiaptomus). Feeding preferences of different copepods probably explain these seasonal and spatial patterns of the community trophic niche. Bayesian mixing model calculations based on source materials of two size fractions of particulate organic matter (nanoplankton at simple energy flow of the planktonic food web of Gwangyang Bay: from primary producers (nanoplankton) and a mixture of primary producers and herbivores (microplankton) through omnivores (Acartia, Calanus, Centropages, and Paracalanus) and detritivores (Pseudodiaptomus, Eurytemora, and harpacticoids) to carnivores (Corycaeus, Tortanus, Labidocera, and Sinocalanus).

  15. Trophic structure and feeding rates of forest soil invertebrate populations

    Energy Technology Data Exchange (ETDEWEB)

    McBrayer, J F; Reichle, D E

    1971-01-01

    Trophic level relationships of a soil invertebrate community were determined using the transient behavior of cesium-137 in experimental soil microcosms. Feeding rates were estimated from radionuclide mass balance equations using radiocesium uptake coefficients, equilibrium concentrations of /sup 137/Cs in consumers, and /sup 137/Cs composition of food bases. The fungivore trophic level included Scatopsidae larvae (Diptera), Enchytraeida (Annelida), Entomobryidae and Onychiuridae (Collembola), Rhodacaridae (Mesostigmata), and Oribatulidae, Camasiidae, Carabodidae, and Cymbaeremaeidae (Oribatei). Approximately 60% of the total faunal biomass occurred in the fungivore trophic level. Fungivores averaged 7.0 +/- 2.4% dry body weight ingested per day. Cecidomyiidae larvae (Diptera), Diplopoda, Isotomidae (Collembola), Uropodina, and Phthiracaridae (Oribatei) were determined to be surface-feeding saprophages. Subsurface-feeding saprophages included Symphyla, Cillibidae (Uropidina), and Palaeacaridae and Epilohmannidae (Oribatei). Surface-feeding saprophages averaged 1.0 +/- 0.4% dry body weight ingested per day. Feeding rates were not calculated for saprophages feeding within the mineral soil horizon. Predators included Dolichopodidae larvae (Diptera), gamasine mites, and the Scutacaridae and other prostigmatid mites. Predators averaged 2.5 +/- 1.0% dry body weight ingested per day. 15 references, 3 figures, 3 tables.

  16. Tri-trophic level Impact of Host Plant Linamarin and Lotaustralin on Tetranychus urticae (Mesostigmata: Tetranychidae) and its predator Phytoseiulus persimilis (Prostigmata: Phytoseiidae)

    Science.gov (United States)

    The impact of linamarin and lotaustralin content in the leaves of Phaseolus lunatus L. on the second and third trophic levels was studied in Tetranychus urticae (Koch) and its predator Phytoseiulus persimilis Athias-Henriot. Chemical analyzes showed that the content of linamarin was higher in termin...

  17. Assessing the Health of Puget Sound's Pelagic Food Web at Multiple Trophic Levels

    Science.gov (United States)

    Rhodes, L. D.; Greene, C. M.; Rice, C. A.; Hall, J. E.; Baxter, A. E.; Naman, S. M.; Chamberlin, J.

    2012-12-01

    Puget Sound is an estuarine fjord in the northwestern United State surrounded by variable upland uses, ranging from industrial and urban to agricultural to forested lands. The quality of Puget Sound's ecosystem is under scrutiny because of the biological resources that depend on its function. In 2011, we undertook a study of the Sound's pelagic food web that measured water quality, microbial parameters, and abundance of higher trophic levels including gelatinous zooplankton, forage fish, and salmon. More than 75 sites spanning the latitudinal expanse of Puget Sound and the range of developed and agricultural land uses were sampled monthly from April to October. Strong relationships between water quality and microbial parameters suggest that microbes may modulate water quality indicators, such as dissolved inorganic nitrogen and pH, and that land use may be an influential factor. Basins within Puget Sound exhibit distinct biological profiles at the microbial and macrobiotic levels, emphasizing that Puget Sound is not a homogenous water body and suggesting that informative food web indicators may vary across the basins.

  18. Long term patterns in the late summer trophic niche of the invasive pumpkinseed sunfish Lepomis gibbosus

    Directory of Open Access Journals (Sweden)

    Gkenas C.

    2016-01-01

    Full Text Available Quantifying the trophic dynamics of invasive species in novel habitats is important for predicting the success of potential invaders and evaluating their ecological effects. The North American pumpkinseed sunfish Lepomis gibbosus is a successful invader in Europe, where it has caused negative ecological effects primarily through trophic interactions. Here, we quantified variations in the late summer trophic niche of pumpkinseed during establishment and integration in the mainstem of the Guadiana river, using stomach content analyses over a period of 40 years. Pumpkinseed showed a shift from trophic specialization during establishment to trophic generalism during integration. These results were concomitant with an increase in diet breadth that was accompanied by higher individual diet specialization particularly in large individuals. Irrespective of their drivers, these changes in trophic niche suggest that the potential ecological effects of pumpkinseed on recipient ecosystems can vary temporally along the invasion process.

  19. Persistence of trophic hotspots and relation to human impacts within an upwelling marine ecosystem.

    Science.gov (United States)

    Santora, Jarrod A; Sydeman, William J; Schroeder, Isaac D; Field, John C; Miller, Rebecca R; Wells, Brian K

    2017-03-01

    Human impacts (e.g., fishing, pollution, and shipping) on pelagic ecosystems are increasing, causing concerns about stresses on marine food webs. Maintaining predator-prey relationships through protection of pelagic hotspots is crucial for conservation and management of living marine resources. Biotic components of pelagic, plankton-based, ecosystems exhibit high variability in abundance in time and space (i.e., extreme patchiness), requiring investigation of persistence of abundance across trophic levels to resolve trophic hotspots. Using a 26-yr record of indicators for primary production, secondary (zooplankton and larval fish), and tertiary (seabirds) consumers, we show distributions of trophic hotspots in the southern California Current Ecosystem result from interactions between a strong upwelling center and a productive retention zone with enhanced nutrients, which concentrate prey and predators across multiple trophic levels. Trophic hotspots also overlap with human impacts, including fisheries extraction of coastal pelagic and groundfish species, as well as intense commercial shipping traffic. Spatial overlap of trophic hotspots with fisheries and shipping increases vulnerability of the ecosystem to localized depletion of forage fish, ship strikes on marine mammals, and pollution. This study represents a critical step toward resolving pelagic areas of high conservation interest for planktonic ecosystems and may serve as a model for other ocean regions where ecosystem-based management and marine spatial planning of pelagic ecosystems is warranted. © 2016 by the Ecological Society of America.

  20. Trophic flow structure of the Danajon ecosystem (Central Philippines) and impacts of illegal and destructive fishing practices

    Science.gov (United States)

    Bacalso, Regina Therese M.; Wolff, Matthias

    2014-11-01

    A trophic model of the shallow Danajon Bank, in the Central Visayas, Philippines was developed using a mass-balance approach (Ecopath) to describe the system characteristics and fisheries interactions. The Ecopath model is composed of 37 functional groups and 17 fishing fleet types reflecting the high diversity of catches and fishing operations in the Danajon Bank. Collectively, the catch is dominated by lower trophic level fish and invertebrates as reflected in the mean trophic level of the fishery (2.95). The low biomass and high exploitation levels for many upper trophic level groups and the little evidence for strong natural physical disturbances suggest that top-down fishery is the main driver of system dynamics. The mixed trophic impacts (MTI) analysis reveals the role of the illegal and destructive fishing operations in influencing the ecosystem structure and dynamics. Furthermore, the illegal fisheries' estimated collective annual harvest is equivalent to nearly a quarter of the entire municipal fisheries catch in the area. Improved fisheries law enforcement by the local government units to curb these illegal and destructive fishing operations could substantially increase the potential gains of the legal fisheries.

  1. Evolutionary trade-offs in plants mediate the strength of trophic cascades.

    Science.gov (United States)

    Mooney, Kailen A; Halitschke, Rayko; Kessler, Andre; Agrawal, Anurag A

    2010-03-26

    Predators determine herbivore and plant biomass via so-called trophic cascades, and the strength of such effects is influenced by ecosystem productivity. To determine whether evolutionary trade-offs among plant traits influence patterns of trophic control, we manipulated predators and soil fertility and measured impacts of a major herbivore (the aphid Aphis nerii) on 16 milkweed species (Asclepias spp.) in a phylogenetic field experiment. Herbivore density was determined by variation in predation and trade-offs between herbivore resistance and plant growth strategy. Neither herbivore density nor predator effects on herbivores predicted the cascading effects of predators on plant biomass. Instead, cascade strength was strongly and positively associated with milkweed response to soil fertility. Accordingly, contemporary patterns of trophic control are driven by evolutionary convergent trade-offs faced by plants.

  2. Are wolves saving Yellowstone's aspen? A landscape-level test of a behaviorally mediated trophic cascade.

    Science.gov (United States)

    Kauffman, Matthew J; Brodie, Jedediah F; Jules, Erik S

    2010-09-01

    Behaviorally mediated trophic cascades (BMTCs) occur when the fear of predation among herbivores enhances plant productivity. Based primarily on systems involving small-bodied predators, BMTCs have been proposed as both strong and ubiquitous in natural ecosystems. Recently, however, synthetic work has suggested that the existence of BMTCs may be mediated by predator hunting mode, whereby passive (sit-and-wait) predators have much stronger effects than active (coursing) predators. One BMTC that has been proposed for a wide-ranging active predator system involves the reintroduction of wolves (Canis lupus) to Yellowstone National Park, USA, which is thought to be leading to a recovery of trembling aspen (Populus tremuloides) by causing elk (Cervus elaphus) to avoid foraging in risky areas. Although this BMTC has been generally accepted and highly popularized, it has never been adequately tested. We assessed whether wolves influence aspen by obtaining detailed demographic data on aspen Stands using tree rings and by monitoring browsing levels in experimental elk exclosures arrayed across a gradient of predation risk for three years. Our study demonstrates that the historical failure of aspen to regenerate varied widely among stands (last recruitment year ranged from 1892 to 1956), and our data do not indicate an abrupt cessation of recruitment. This pattern of recruitment failure appears more consistent with a gradual increase in elk numbers rather than a rapid behavioral shift in elk foraging following wolf extirpation. In addition, our estimates of relative survivorship of young browsable aspen indicate that aspen are not currently recovering in Yellowstone, even in the presence of a large wolf population. Finally, in an experimental test of the BMTC hypothesis we found that the impacts of elk browsing on aspen demography are not diminished in sites where elk are at higher risk of predation by wolves. These findings suggest the need to further evaluate how trophic

  3. Effects of trophic exposure to diclofenac and dexamethasone on hematological parameters and immune response in freshwater fish.

    Science.gov (United States)

    Ribas, João Luiz Coelho; Zampronio, Aleksander R; Silva de Assis, Helena C

    2016-04-01

    The aim of the present study was to evaluate the effects of diclofenac and dexamethasone on hematological parameters and immune response in the fish species Hoplias malabaricus after trophic exposure. Fish were fed twice every week with Astyanax sp., which were given an intraperitoneal inoculation with diclofenac (0 μg/kg, 0.2 μg/kg, 2.0 μg/kg, or 20.0 μg/kg) or dexamethasone (0.03 μg/kg, 0.3 μg/kg, or 3.0 μg/kg). After 12 doses, the hematological parameters and lipopolysaccharide-induced nitric oxide production by head kidney monocytic lineage were evaluated. Exposed fish also received 1 mg/kg of carrageenan intraperitoneal, and cell migration to the peritoneal cavity was evaluated after 4 h. Diclofenac and dexamethasone altered the red blood cell count, as well as hematocrit and hemoglobin levels. The total blood leukocyte count decreased in all groups. A significantly reduced carrageenan-induced leukocyte migration to the peritoneal cavity, particularly of polymorphonuclear cells, was observed at all tested doses, suggesting a possible immunosuppressive effect. The basal nitric oxide synthesis of head kidney cell cultures was reduced at the highest dose of diclofenac and was increased at the highest dose of dexamethasone. The lipopolysaccharide-stimulated nitric oxide production was reduced in all treatments, thus corroborating the immunosuppressive effect. Although some fish responses were variable for different drugs, the results suggested that trophic exposure to diclofenac and dexamethasone can lead to hematological changes and immunotoxic effects, causing negative impacts in aquatic organisms. © 2015 SETAC.

  4. From neurons to epidemics: How trophic coherence affects spreading processes

    Science.gov (United States)

    Klaise, Janis; Johnson, Samuel

    2016-06-01

    Trophic coherence, a measure of the extent to which the nodes of a directed network are organised in levels, has recently been shown to be closely related to many structural and dynamical aspects of complex systems, including graph eigenspectra, the prevalence or absence of feedback cycles, and linear stability. Furthermore, non-trivial trophic structures have been observed in networks of neurons, species, genes, metabolites, cellular signalling, concatenated words, P2P users, and world trade. Here, we consider two simple yet apparently quite different dynamical models—one a susceptible-infected-susceptible epidemic model adapted to include complex contagion and the other an Amari-Hopfield neural network—and show that in both cases the related spreading processes are modulated in similar ways by the trophic coherence of the underlying networks. To do this, we propose a network assembly model which can generate structures with tunable trophic coherence, limiting in either perfectly stratified networks or random graphs. We find that trophic coherence can exert a qualitative change in spreading behaviour, determining whether a pulse of activity will percolate through the entire network or remain confined to a subset of nodes, and whether such activity will quickly die out or endure indefinitely. These results could be important for our understanding of phenomena such as epidemics, rumours, shocks to ecosystems, neuronal avalanches, and many other spreading processes.

  5. Modelling for an improved integrated multi-trophic aquaculture system for the production of highly valued marine species

    Directory of Open Access Journals (Sweden)

    Luana Granada

    2014-05-01

    Full Text Available Integrated multi-trophic aquaculture (IMTA is regarded as a suitable approach to limit aquaculture nutrients and organic matter outputs through biomitigation. Here, species from different trophic or nutritional levels are connected through water transfer. The co-cultured species are used as biofilters, and each level has its own independent commercial value, providing both economic and environmental sustainability. In order to better understand and optimize aquaculture production systems, dynamic modelling has been developed towards the use of models for analysis and simulation of aquacultures. Several models available determine the carrying capacity of farms and the environmental effects of bivalve and fish aquaculture. Also, in the last two decades, modelling strategies have been designed in order to predict the dispersion and deposition of organic fish farm waste, usually using the mean settling velocity of faeces and feed pellets. Cultured organisms growth, effects of light and temperature on algae growth, retention of suspended solids, biodegradation of nitrogen and wastewater treatment are examples of other modelled parameters in aquaculture. Most modelling equations have been developed for monocultures, despite the increasing importance of multi-species systems, such as polyculture and IMTA systems. The main reason for the development of multi-species models is to maximize the production and optimize species combinations in order to reduce the environmental impacts of aquaculture. Some multi-species system models are available, including from the polyculture of different species of bivalves with fish to more complex systems with four trophic levels. These can incorporate ecosystem models and use dynamic energy budgets for each trophic group. In the proposed IMTA system, the bioremediation potential of the marine seaweed Gracilaria vermiculophylla (nutrient removal performance and the Mediterranean filter-feeding polychaete Sabella

  6. Trophic Effects of Dental Pulp Stem Cells on Schwann Cells in Peripheral Nerve Regeneration.

    Science.gov (United States)

    Yamamoto, Tsubasa; Osako, Yohei; Ito, Masataka; Murakami, Masashi; Hayashi, Yuki; Horibe, Hiroshi; Iohara, Koichiro; Takeuchi, Norio; Okui, Nobuyuki; Hirata, Hitoshi; Nakayama, Hidenori; Kurita, Kenichi; Nakashima, Misako

    2016-01-01

    Recently, mesenchymal stem cells have demonstrated a potential for neurotrophy and neurodifferentiation. We have recently isolated mobilized dental pulp stem cells (MDPSCs) using granulocyte-colony stimulating factor (G-CSF) gradient, which has high neurotrophic/angiogenic potential. The aim of this study is to investigate the effects of MDPSC transplantation on peripheral nerve regeneration. Effects of MDPSC transplantation were examined in a rat sciatic nerve defect model and compared with autografts and control conduits containing collagen scaffold. Effects of conditioned medium of MDPSCs were also evaluated in vitro. Transplantation of MDPSCs in the defect demonstrated regeneration of myelinated fibers, whose axons were significantly higher in density compared with those in autografts and control conduits only. Enhanced revascularization was also observed in the MDPSC transplants. The MDPSCs did not directly differentiate into Schwann cell phenotype; localization of these cells near Schwann cells induced several neurotrophic factors. Immunofluorescence labeling demonstrated reduced apoptosis and increased proliferation in resident Schwann cells in the MDPSC transplant compared with control conduits. These trophic effects of MDPSCs on proliferation, migration, and antiapoptosis in Schwann cells were further elucidated in vitro. The results demonstrate that MDPSCs promote axon regeneration through trophic functions, acting on Schwann cells, and promoting angiogenesis.

  7. Modeling lake trophic state: a random forest approach

    Science.gov (United States)

    Productivity of lentic ecosystems has been well studied and it is widely accepted that as nutrient inputs increase, productivity increases and lakes transition from low trophic state (e.g. oligotrophic) to higher trophic states (e.g. eutrophic). These broad trophic state classi...

  8. Simulated tri-trophic networks reveal complex relationships between species diversity and interaction diversity.

    Science.gov (United States)

    Pardikes, Nicholas A; Lumpkin, Will; Hurtado, Paul J; Dyer, Lee A

    2018-01-01

    Most of earth's biodiversity is comprised of interactions among species, yet it is unclear what causes variation in interaction diversity across space and time. We define interaction diversity as the richness and relative abundance of interactions linking species together at scales from localized, measurable webs to entire ecosystems. Large-scale patterns suggest that two basic components of interaction diversity differ substantially and predictably between different ecosystems: overall taxonomic diversity and host specificity of consumers. Understanding how these factors influence interaction diversity, and quantifying the causes and effects of variation in interaction diversity are important goals for community ecology. While previous studies have examined the effects of sampling bias and consumer specialization on determining patterns of ecological networks, these studies were restricted to two trophic levels and did not incorporate realistic variation in species diversity and consumer diet breadth. Here, we developed a food web model to generate tri-trophic ecological networks, and evaluated specific hypotheses about how the diversity of trophic interactions and species diversity are related under different scenarios of species richness, taxonomic abundance, and consumer diet breadth. We investigated the accumulation of species and interactions and found that interactions accumulate more quickly; thus, the accumulation of novel interactions may require less sampling effort than sampling species in order to get reliable estimates of either type of diversity. Mean consumer diet breadth influenced the correlation between species and interaction diversity significantly more than variation in both species richness and taxonomic abundance. However, this effect of diet breadth on interaction diversity is conditional on the number of observed interactions included in the models. The results presented here will help develop realistic predictions of the relationships

  9. Saccharomyces boulardii CNCM I-745 Improves Intestinal Enzyme Function: A Trophic Effects Review.

    Science.gov (United States)

    Moré, Margret I; Vandenplas, Yvan

    2018-01-01

    Several properties of the probiotic medicinal yeast Saccharomyces boulardii CNCM I-745 contribute to its efficacy to prevent or treat diarrhoea. Besides immunologic effects, pathogen-binding and anti-toxin effects, as well as positive effects on the microbiota, S boulardii CNCM I-745 also has pronounced effects on digestive enzymes of the brush border membrane, known as trophic effects. The latter are the focus of this review. Literature has been reviewed after searching Medline and PMC databases. All relevant non-clinical and clinical studies are summarized. S. boulardii CNCM I-745 synthesizes and secretes polyamines, which have a role in cell proliferation and differentiation. The administration of polyamines or S. boulardii CNCM I-745 enhances the expression of intestinal digestive enzymes as well as nutrient uptake transporters. The signalling mechanisms leading to enzyme activation are not fully understood. However, polyamines have direct nucleic acid-binding capacity with regulatory impact. S. boulardii CNCM I-745 induces signalling via the mitogen-activated protein kinase pathway. In addition, effects on the phosphatidylinositol-3 kinase (PI3K) pathway have been reported. As an additional direct effect, S. boulardii CNCM I-745 secretes certain enzymes, which enhance nutrient acquisition for the yeast and the host. The increased availability of digestive enzymes seems to be one of the mechanisms by which S. boulardii CNCM I-745 counteracts diarrhoea; however, also people with certain enzyme deficiencies may profit from its administration. More studies are needed to fully understand the mechanisms of trophic activation by the probiotic yeast.

  10. Trophic dynamics in a simple experimental ecosystem: Interactions among centipedes, Collembola and introduced earthworms

    Science.gov (United States)

    Meixiang Gao; Melanie K. Taylor; Mac A. Callaham

    2017-01-01

    Invasive earthworms in North America are known to have dramatic influences on soil ecosystems, including negative effects on other soil fauna. In general, studies examining this phenomenon have focused on invasive earthworm impacts on organisms at the same or lower trophic level as the earthworms themselves (i.e., detritivores and decomposers). In contrast, there have...

  11. Trophic structure of macroinvertebrates in tropical pasture streams

    Directory of Open Access Journals (Sweden)

    Bruna Neves da Silveira-Manzotti

    Full Text Available Abstract: Aim The aim of this study was to describe the diet of stream macroinvertebrates and to determine their trophic groups. Methods Invertebrates were sampled with D nets in three pasture streams. They were identified to genus level and submitted to gut content analysis, except for fluid feeders such as hemipterans, to which diet data was obtained from the literature. Trophic groups were determined based on a similarity analysis using the Bray-Curtis similarity coefficient. Results Five trophic groups were defined: fine-detritivores (feed mostly on fine particulate organic matter - FPOM, coarse-detritivores/herbivores (feed mostly on coarse particulate organic matter - CPOM - and plant material, omnivores, specialist-predators (prey upon aquatic insects only, and generalist-predators. Ephemeroptera, Diptera (except Tanypodinae, Coleoptera, and Trichoptera (except Smicridea were detritivores. The caddis Macronema (Trichoptera fed exclusively on plant detritus and Tanypodinae and Smicridea were classified as omnivores. The odonate families Calopterygidae and Gomphidae were classified as specialist-predators, while Macrobrachium (Decapoda, Belostoma, and Limnocoris (Hemiptera were generalist-predators. Conclusions The great quantity and frequency of occurrence of FPOM consumed by most taxa highlight the importance of this food resource for macroinvertebrate communities from tropical streams. Furthermore, observed variations on trophic group assignment for some taxa indicate the generalist and opportunistic nature of these aquatic invertebrates. Such findings reinforce the importance of conducting gut content analysis on macroinvertebrates to understand their role in the structure and functioning of tropical streams.

  12. EVALUATION OF TROPHIC STATUS OF AGRAKHAN BAY (THE NORTH CASPIAN SEA AS A PART OF ECOLOGICAL MONITORING OF SPECIALLY PROTECTED AREAS

    Directory of Open Access Journals (Sweden)

    A. A. Gadzhiev

    2013-01-01

    Full Text Available Abstract. Aim. Hydrochemical composition of waters of Agrakhan Bay (the North Caspian Sea, degree of pollution, structure and quantitative characteristics of phytoplankton, zooplankton and zoobenthos is given in the paper. Evaluation of a trophic status of the bay and seasonal trophodynamics are given as a result of study.Material and methods. The study is based on original materials from expeditions of 2012 (Autumn and 2013 (Spring and Summer in Agrakhan Bay. The complex materials are collected on stations with distance 3.5 km. Totally was made 16 marine stations, where samples of water, phytoplankton, zooplankton and benthos were taken.Results. Agrakhan Bay is eutrophic by level of dissolved oxygen and its BOD. However, the oxygen deficiency is not observed. concentration of oxygen is high almost in all seasons, that has a beneficial effect on hydrobionts. Seasonal dynamics indicates that Agrakhansky bay is oligotrophic within a year, but its trophic status increases to mesotrophic and even to hypertrophic in some periods. The northern part ща the bay is eutrophic. Difference in trophic levels of different parts of the bay is the result of significant differences in depth and area of water surface.Conclusions. Anthropogenic impact on Agrakhan Bay increases its trophic status. Seasonal trophic level of Agrakhan Gulf except natural processes depends on the "purity" of the Terek River sediments, which are the main source of biogenic elements. Typically, the absolute concentration of biogenic elements in Agrakhan Bay increases with the increase of eutrophication.

  13. Population growth, trophic level, and reproductive biology of two congeneric archer fishes (Toxotes chatareus, Hamilton 1822 and Toxotes jaculatrix, Pallas 1767) inhabiting Malaysian coastal waters.

    Science.gov (United States)

    Simon, K D; Bakar, Y; Samat, A; Zaidi, C C; Aziz, A; Mazlan, A G

    2009-12-01

    Population growth, trophic level, and some aspects of reproductive biology of two congeneric archer fish species, Toxotes chatareus and Toxotes jaculatrix, collected from Johor coastal waters, Malaysia, were studied. Growth pattern by length-weight relationship (W=aL(b)) for the sexes differed, and exhibited positive allometric growth (male, female and combined sexes of T. chatareus; female and combined sexes of T. jaculatrix) and isometric growth (male samples of T. jaculatrix only). Trophic levels of both species were analyzed based on 128 specimens. The results show that, in both species, crustaceans and insects were the most abundant prey items, and among crustaceans the red clawed crab Sesarma bidens and Formicidae family insects were the most represented taxa. The estimated mean trophic levels for T. chatareus and T. jaculatrix were 3.422+/-0.009 and 3.420+/-0.020, respectively, indicating that they are largely carnivores. Fecundity of T. chatareus ranged from 38 354 to 147 185 eggs for females with total length ranging from 14.5 to 22.5 cm and total body weight from 48.7 to 270.2 g, and T. jaculatrix 25 251 to 150 456 eggs for females with total length ranging from 12.2 to 23.0 cm and total body weight from 25.7 to 275.0 g. Differences in values of gonadosomatic and hepatosomatic indexes calculated for both species in this study may have resulted from uneven sample size ranges.

  14. Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems?

    Science.gov (United States)

    Moullec, Fabien; Gascuel, Didier; Bentorcha, Karim; Guénette, Sylvie; Robert, Marianne

    2017-08-01

    Trophic models are key tools to go beyond the single-species approaches used in stock assessments to adopt a more holistic view and implement the Ecosystem Approach to Fisheries Management (EAFM). This study aims to: (i) analyse the trophic functioning of the Celtic Sea and the Bay of Biscay, (ii) investigate ecosystem changes over the 1980-2013 period and, (iii) explore the response to management measures at the food web scale. Ecopath models were built for each ecosystem for years 1980 and 2013, and Ecosim models were fitted to time series data of biomass and catches. EcoTroph diagnosis showed that in both ecosystems, fishing pressure focuses on high trophic levels (TLs) and, to a lesser extent, on intermediate TLs. However, the interplay between local environmental conditions, species composition and ecosystem functioning could explain the different responses to fisheries management observed between these two contiguous ecosystems. Indeed, over the study period, the ecosystem's exploitation status has improved in the Bay of Biscay but not in the Celtic Sea. This improvement does not seem to be sufficient to achieve the objectives of an EAFM, as high trophic levels were still overexploited in 2013 and simulations conducted with Ecosim in the Bay of Biscay indicate that at current fishing effort the biomass will not be rebuilt by 2030. The ecosystem's response to a reduction in fishing mortality depends on which trophic levels receive protection. Reducing fishing mortality on pelagic fish, instead of on demersal fish, appears more efficient at maximising catch and total biomass and at conserving both top-predator and intermediate TLs. Such advice-oriented trophic models should be used on a regular basis to monitor the health status of marine food webs and analyse the trade-offs between multiple objectives in an ecosystem-based fisheries management context.

  15. Organochlorines in the Vaccares Lagoon trophic web (Biosphere Reserve of Camargue, France)

    Energy Technology Data Exchange (ETDEWEB)

    Roche, H., E-mail: helene.roche@u-psud.f [Ecologie, Systematique et Evolution, UMR8079 CNRS, Universite Paris-Sud, AgroParisTech, F91405 Orsay Cedex (France); Vollaire, Y.; Persic, A.; Buet, A. [Ecologie, Systematique et Evolution, UMR8079 CNRS, Universite Paris-Sud, AgroParisTech, F91405 Orsay Cedex (France); Oliveira-Ribeiro, C. [Departamento de Biologia Celular, Universidade Federal do Parana, Caixa Postal 19031, CEP: 81.531-990, Curitiba, PR (Brazil); Coulet, E. [Nature Reserve of Camargue, La Capeliere, F13200 Arles (France); Banas, D.; Ramade, F. [Ecologie, Systematique et Evolution, UMR8079 CNRS, Universite Paris-Sud, AgroParisTech, F91405 Orsay Cedex (France)

    2009-08-15

    During a decade (1996-2006), ecotoxicological studies were carried out in biota of the Vaccares Lagoon (Biosphere Reserve in Rhone Delta, France). A multicontamination was shown at all levels of the trophic web due to a direct bioconcentration of chemical from the medium combined with a food transfer. Here, the pollutants investigated were organochlorines, among which many compounds banned or in the course of prohibition (or restriction) (PCB, lindane, pp'-DDE, dieldrin, aldrin, heptachlor, endosulfan...) and some substances likely still used in the Rhone River basin (diuron, fipronil). The results confirmed the ubiquity of contamination. It proves to be chronic, variable and tends to regress; however contamination levels depend on the trophic compartment. A biomagnification process was showed. A comparison of investigation methods used in other Mediterranean wetlands provides basis of discussion, and demonstrates the urgent need of modelling to assess the ecotoxicological risk in order to improve the management of such protected areas. - The Vaccares Lagoon trophic web biomagnifies organochlorine pollutants.

  16. Assessment of contaminant levels and trophic relations at a World Heritage Site by measurements in a characteristic shorebird species

    Energy Technology Data Exchange (ETDEWEB)

    Schwemmer, Philipp, E-mail: schwemmer@ftz-west.uni-kiel.de [Research and Technology Centre (Forschungs- und Technologiezentrum), University of Kiel, Hafentörn 1, 25761 Büsum (Germany); Covaci, Adrian, E-mail: adrian.covaci@uantwerpen.be [Toxicological Center, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium); Das, Krishna, E-mail: krishna.das@ulg.ac.be [Laboratory for Oceanology-MARE Research Center, University of Liege, Allée de la Chimie 17, B6C, Institut de Chimie, 4000 Liege (Sart-Tilman) (Belgium); Lepoint, Gilles, E-mail: g.lepoint@ulg.ac.be [Laboratory for Oceanology-MARE Research Center, University of Liege, Allée de la Chimie 17, B6C, Institut de Chimie, 4000 Liege (Sart-Tilman) (Belgium); Adler, Sven, E-mail: sven.adler@slu.se [Swedish University of Agricultural Sciences, 901 83 Umeå (Sweden); Garthe, Stefan, E-mail: garthe@ftz-west.uni-kiel.de [Research and Technology Centre (Forschungs- und Technologiezentrum), University of Kiel, Hafentörn 1, 25761 Büsum (Germany)

    2015-01-15

    The River Elbe is responsible for influxes of contaminants into the Wadden Sea World Heritage Site. We investigated levels of polychlorinated biphenyls (PCBs), oxychlordane (OxC), hexachlorobenzene (HCB), hexachlorocyclohexanes (α-, β-, γ-HCHs), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polybrominated diphenyl ethers (PBDEs) in blood and feathers from Eurasian oystercatchers (Haematopus ostralegus; n=28) at the Elbe and compared it with a non-riverine site about 90 km further north. (1) Mean levels of all contaminants in feathers and serum were significantly higher at the river (∑PCBs: 27.6 ng/g feather, 37.0 ng/ml serum; ∑DDTs: 5.3 ng/g feather, 4.4 ng/ml serum) compared with the non-riverine site (∑PCBs: 6.5 ng/g feather, 1.2 ng/ml serum; ∑DDTs: 1.4 ng/g feather, 0.5 ng/ml serum). Mean ∑HCH and HCB levels were <1.8 ng/g in feather and <1.8 ng/ml in serum at both sites. (2) Levels of most detectable compounds in serum and feathers were significantly related, but levels were not consistently higher in either tissue. (3) There was no significant relationship between trophic level in individual oystercatchers (expressed as δ15N) or the degree of terrestrial feeding (expressed as δ13C) and contaminant loads. (4) PBDEs were not detected in significant amounts at either site. The results of this study indicate that the outflow from one of Europe′s largest river systems is associated with significant historical contamination, reflected by the accumulation of contaminants in body tissues in a coastal benthivore predator. - Highlights: • Contaminants in Oystercatchers from the Elbe river and a non-riverine site were measured. • Mean levels of contaminants were higher at the river than at the non-riverine site. • Levels of most contaminants in serum and feathers were significantly related. • No relationship between trophic level (δ15N) and contaminant level was found. • One of Europe′s largest river systems is associated

  17. Assessment of contaminant levels and trophic relations at a World Heritage Site by measurements in a characteristic shorebird species

    International Nuclear Information System (INIS)

    Schwemmer, Philipp; Covaci, Adrian; Das, Krishna; Lepoint, Gilles; Adler, Sven; Garthe, Stefan

    2015-01-01

    The River Elbe is responsible for influxes of contaminants into the Wadden Sea World Heritage Site. We investigated levels of polychlorinated biphenyls (PCBs), oxychlordane (OxC), hexachlorobenzene (HCB), hexachlorocyclohexanes (α-, β-, γ-HCHs), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polybrominated diphenyl ethers (PBDEs) in blood and feathers from Eurasian oystercatchers (Haematopus ostralegus; n=28) at the Elbe and compared it with a non-riverine site about 90 km further north. (1) Mean levels of all contaminants in feathers and serum were significantly higher at the river (∑PCBs: 27.6 ng/g feather, 37.0 ng/ml serum; ∑DDTs: 5.3 ng/g feather, 4.4 ng/ml serum) compared with the non-riverine site (∑PCBs: 6.5 ng/g feather, 1.2 ng/ml serum; ∑DDTs: 1.4 ng/g feather, 0.5 ng/ml serum). Mean ∑HCH and HCB levels were <1.8 ng/g in feather and <1.8 ng/ml in serum at both sites. (2) Levels of most detectable compounds in serum and feathers were significantly related, but levels were not consistently higher in either tissue. (3) There was no significant relationship between trophic level in individual oystercatchers (expressed as δ15N) or the degree of terrestrial feeding (expressed as δ13C) and contaminant loads. (4) PBDEs were not detected in significant amounts at either site. The results of this study indicate that the outflow from one of Europe′s largest river systems is associated with significant historical contamination, reflected by the accumulation of contaminants in body tissues in a coastal benthivore predator. - Highlights: • Contaminants in Oystercatchers from the Elbe river and a non-riverine site were measured. • Mean levels of contaminants were higher at the river than at the non-riverine site. • Levels of most contaminants in serum and feathers were significantly related. • No relationship between trophic level (δ15N) and contaminant level was found. • One of Europe′s largest river systems is associated

  18. Trophic modeling of the Northern Humboldt Current Ecosystem, Part I: Comparing trophic linkages under La Niña and El Niño conditions

    Science.gov (United States)

    Tam, Jorge; Taylor, Marc H.; Blaskovic, Verónica; Espinoza, Pepe; Michael Ballón, R.; Díaz, Erich; Wosnitza-Mendo, Claudia; Argüelles, Juan; Purca, Sara; Ayón, Patricia; Quipuzcoa, Luis; Gutiérrez, Dimitri; Goya, Elisa; Ochoa, Noemí; Wolff, Matthias

    2008-10-01

    The El Niño of 1997-98 was one of the strongest warming events of the past century; among many other effects, it impacted phytoplankton along the Peruvian coast by changing species composition and reducing biomass. While responses of the main fish resources to this natural perturbation are relatively well known, understanding the ecosystem response as a whole requires an ecotrophic multispecies approach. In this work, we construct trophic models of the Northern Humboldt Current Ecosystem (NHCE) and compare the La Niña (LN) years in 1995-96 with the El Niño (EN) years in 1997-98. The model area extends from 4°S-16°S and to 60 nm from the coast. The model consists of 32 functional groups of organisms and differs from previous trophic models of the Peruvian system through: (i) division of plankton into size classes to account for EN-associated changes and feeding preferences of small pelagic fish, (ii) increased division of demersal groups and separation of life history stages of hake, (iii) inclusion of mesopelagic fish, and (iv) incorporation of the jumbo squid ( Dosidicus gigas), which became abundant following EN. Results show that EN reduced the size and organization of energy flows of the NHCE, but the overall functioning (proportion of energy flows used for respiration, consumption by predators, detritus and export) of the ecosystem was maintained. The reduction of diatom biomass during EN forced omnivorous planktivorous fish to switch to a more zooplankton-dominated diet, raising their trophic level. Consequently, in the EN model the trophic level increased for several predatory groups (mackerel, other large pelagics, sea birds, pinnipeds) and for fishery catch. A high modeled biomass of macrozooplankton was needed to balance the consumption by planktivores, especially during EN condition when observed diatoms biomass diminished dramatically. Despite overall lower planktivorous fish catches, the higher primary production required-to-catch ratio implied a

  19. Replacing fish meal by food waste in feed pellets to culture lower trophic level fish containing acceptable levels of organochlorine pesticides: health risk assessments.

    Science.gov (United States)

    Cheng, Zhang; Mo, Wing-Yin; Man, Yu-Bon; Nie, Xiang-Ping; Li, Kai-Bing; Wong, Ming-Hung

    2014-12-01

    The present study used food waste (collected from local hotels and restaurants) feed pellets in polyculture of low-trophic level fish [bighead (Aristichtys nobilis), grass carp (Ctenopharyngodon idellus), and mud carp (Cirrhina molitorella)] aiming at producing safe and quality products for local consumption. The results indicated that grass carp (hexachlorocyclohexanes (HCHs) waste feed pellets were relatively free of organochlorine pesticides (OCPs). The experimental ponds (water and sediment) were relatively free of OCPs, lowering the possibility of biomagnification of OCPs in the food chains within the ponds. The raw concentrations of OCPs extracted from the fish were not in the bioavailable form, which would ultimately reach bloodstream and exert adverse effects on human body. Health risk assessments based on digestible concentrations are commonly regarded as a more accurate method. The results of health risk assessments based on raw and digestible concentrations showed that the fish fed with food waste feed pellets were safe for consumption from the OCP perspective. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. The effects of anthropogenic organic matter inputs on stable carbon and nitrogen isotopes in organisms from different trophic levels in a southern Mediterranean coastal area

    International Nuclear Information System (INIS)

    Vizzini, Salvatrice; Mazzola, Antonio

    2006-01-01

    Stable isotope ratios were used to determine the impact of anthropogenically derived organic matter from onshore and offshore fish farming and a sewage outfall on organisms at different trophic levels (primary producers and consumers) on the south-east coast of Sicily (Italy, Mediterranean). Representative macroalgae and consumers were collected in three sampling locations: 'Impact' and two putative 'Controls' sited to the north of the impacted location. While δ 13 C values of both organic matter sources and consumers varied little between locations, δ 15 N spatial variability was higher and δ 15 N was shown to be a good descriptor of organic enrichment and uptake of anthropogenically derived material within coastal food webs. Isotopic data were analysed using a multivariate approach. Organic matter sources and benthic components were more sensitive to pollution than nektobenthic species and revealed that the effects of anthropogenic activities seem to be detectable over a wide area. The study site is characterised by wide waste dispersal, which brings a reduction in impact in the area directly affected by organic matter inputs and enlarges the area of moderate impact

  1. Trophic Niche Differentiation in Rodents and Marsupials Revealed by Stable Isotopes.

    Directory of Open Access Journals (Sweden)

    Mauro Galetti

    Full Text Available Tropical rainforests support the greatest diversity of small mammals in the world, yet we have little understanding about the mechanisms that promote the coexistence of species. Diet partitioning can favor coexistence by lessening competition, and interspecific differences in body size and habitat use are usually proposed to be associated with trophic divergence. However, the use of classic dietary methods (e.g. stomach contents is challenging in small mammals, particularly in community-level studies, thus we used stable isotopes (δ13C and δ15N to infer about trophic niche. We investigated i how trophic niche is partitioned among rodent and marsupial species in three Atlantic forest sites and ii if interspecific body size and locomotor habit inequalities can constitute mechanisms underlying the isotopic niche partitioning. We found that rodents occupied a broad isotopic niche space with species distributed in different trophic levels and relying on diverse basal carbon sources (C3 and C4 plants. Surprisingly, on the other hand, marsupials showed a narrow isotopic niche, both in δ13C and δ15N dimensions, which is partially overlapped with rodents, contradicting their description as omnivores and generalists proposed classic dietary studies. Although body mass differences did not explained the divergence in isotopic values among species, groups of species with different locomotor habit presented clear differences in the position of the isotopic niche space, indicating that the use of different forest strata can favor trophic niche partitioning in small mammals communities. We suggest that anthropogenic impacts, such as habitat modification (logging, harvesting, can simplify the vertical structure of ecosystems and collapse the diversity of basal resources, which might affect negatively small mammals communities in Atlantic forests.

  2. Vitamin D and muscle trophicity.

    Science.gov (United States)

    Domingues-Faria, Carla; Boirie, Yves; Walrand, Stéphane

    2017-05-01

    We review recent findings on the involvement of vitamin D in skeletal muscle trophicity. Vitamin D deficiencies are associated with reduced muscle mass and strength, and its supplementation seems effective to improve these parameters in vitamin D-deficient study participants. Latest investigations have also evidenced that vitamin D is essential in muscle development and repair. In particular, it modulates skeletal muscle cell proliferation and differentiation. However, discrepancies still exist about an enhancement or a decrease of muscle proliferation and differentiation by the vitamin D. Recently, it has been demonstrated that vitamin D influences skeletal muscle cell metabolism as it seems to regulate protein synthesis and mitochondrial function. Finally, apart from its genomic and nongenomic effects, recent investigations have demonstrated a genetic contribution of vitamin D to muscle functioning. Recent studies support the importance of vitamin D in muscle health, and the impact of its deficiency in regard to muscle mass and function. These 'trophic' properties are of particular importance for some specific populations such as elderly persons and athletes, and in situations of loss of muscle mass or function, particularly in the context of chronic diseases.

  3. Plant species richness sustains higher trophic levels of soil nematode communities after consecutive environmental perturbations.

    Science.gov (United States)

    Cesarz, Simone; Ciobanu, Marcel; Wright, Alexandra J; Ebeling, Anne; Vogel, Anja; Weisser, Wolfgang W; Eisenhauer, Nico

    2017-07-01

    The magnitude and frequency of extreme weather events are predicted to increase in the future due to ongoing climate change. In particular, floods and droughts resulting from climate change are thought to alter the ecosystem functions and stability. However, knowledge of the effects of these weather events on soil fauna is scarce, although they are key towards functioning of terrestrial ecosystems. Plant species richness has been shown to affect the stability of ecosystem functions and food webs. Here, we used the occurrence of a natural flood in a biodiversity grassland experiment that was followed by a simulated summer drought experiment, to investigate the interactive effects of plant species richness, a natural flood, and a subsequent summer drought on nematode communities. Three and five months after the natural flooding, effects of flooding severity were still detectable in the belowground system. We found that flooding severity decreased soil nematode food-web structure (loss of K-strategists) and the abundance of plant feeding nematodes. However, high plant species richness maintained higher diversity and abundance of higher trophic levels compared to monocultures throughout the flood. The subsequent summer drought seemed to be of lower importance but reversed negative flooding effects in some cases. This probably occurred because the studied grassland system is well adapted to drought, or because drought conditions alleviated the negative impact of long-term soil waterlogging. Using soil nematodes as indicator taxa, this study suggests that high plant species richness can maintain soil food web complexity after consecutive environmental perturbations.

  4. Species co-occurrence networks: Can they reveal trophic and non-trophic interactions in ecological communities?

    Science.gov (United States)

    Freilich, Mara A; Wieters, Evie; Broitman, Bernardo R; Marquet, Pablo A; Navarrete, Sergio A

    2018-03-01

    Co-occurrence methods are increasingly utilized in ecology to infer networks of species interactions where detailed knowledge based on empirical studies is difficult to obtain. Their use is particularly common, but not restricted to, microbial networks constructed from metagenomic analyses. In this study, we test the efficacy of this procedure by comparing an inferred network constructed using spatially intensive co-occurrence data from the rocky intertidal zone in central Chile to a well-resolved, empirically based, species interaction network from the same region. We evaluated the overlap in the information provided by each network and the extent to which there is a bias for co-occurrence data to better detect known trophic or non-trophic, positive or negative interactions. We found a poor correspondence between the co-occurrence network and the known species interactions with overall sensitivity (probability of true link detection) equal to 0.469, and specificity (true non-interaction) equal to 0.527. The ability to detect interactions varied with interaction type. Positive non-trophic interactions such as commensalism and facilitation were detected at the highest rates. These results demonstrate that co-occurrence networks do not represent classical ecological networks in which interactions are defined by direct observations or experimental manipulations. Co-occurrence networks provide information about the joint spatial effects of environmental conditions, recruitment, and, to some extent, biotic interactions, and among the latter, they tend to better detect niche-expanding positive non-trophic interactions. Detection of links (sensitivity or specificity) was not higher for well-known intertidal keystone species than for the rest of consumers in the community. Thus, as observed in previous empirical and theoretical studies, patterns of interactions in co-occurrence networks must be interpreted with caution, especially when extending interaction

  5. Trophic Ecology of Benthic Marine Invertebrates with Bi-Phasic Life Cycles: What Are We Still Missing?

    Science.gov (United States)

    Calado, Ricardo; Leal, Miguel Costa

    2015-01-01

    The study of trophic ecology of benthic marine invertebrates with bi-phasic life cycles is critical to understand the mechanisms shaping population dynamics. Moreover, global climate change is impacting the marine environment at an unprecedented level, which promotes trophic mismatches that affect the phenology of these species and, ultimately, act as drivers of ecological and evolutionary change. Assessing the trophic ecology of marine invertebrates is critical to understanding maternal investment, larval survival to metamorphosis, post-metamorphic performance, resource partitioning and trophic cascades. Tools already available to assess the trophic ecology of marine invertebrates, including visual observation, gut content analysis, food concentration, trophic markers, stable isotopes and molecular genetics, are reviewed and their main advantages and disadvantages for qualitative and quantitative approaches are discussed. The challenges to perform the partitioning of ingestion, digestion and assimilation are discussed together with different approaches to address each of these processes for short- and long-term fingerprinting. Future directions for research on the trophic ecology of benthic marine invertebrates with bi-phasic life cycles are discussed with emphasis on five guidelines that will allow for systematic study and comparative meta-analysis to address important unresolved questions. © 2015 Elsevier Ltd. All rights reserved.

  6. Trophic interactions between native and introduced fish species in a littoral fish community.

    Science.gov (United States)

    Monroy, M; Maceda-Veiga, A; Caiola, N; De Sostoa, A

    2014-11-01

    The trophic interactions between 15 native and two introduced fish species, silverside Odontesthes bonariensis and rainbow trout Oncorhynchus mykiss, collected in a major fishery area at Lake Titicaca were explored by integrating traditional ecological knowledge and stable-isotope analyses (SIA). SIA suggested the existence of six trophic groups in this fish community based on δ(13)C and δ(15)N signatures. This was supported by ecological evidence illustrating marked spatial segregation between groups, but a similar trophic level for most of the native groups. Based on Bayesian ellipse analyses, niche overlap appeared to occur between small O. bonariensis (<90 mm) and benthopelagic native species (31.6%), and between the native pelagic killifish Orestias ispi and large O. bonariensis (39%) or O. mykiss (19.7%). In addition, Bayesian mixing models suggested that O. ispi and epipelagic species are likely to be the main prey items for the two introduced fish species. This study reveals a trophic link between native and introduced fish species, and demonstrates the utility of combining both SIA and traditional ecological knowledge to understand trophic relationships between fish species with similar feeding habits. © 2014 The Fisheries Society of the British Isles.

  7. Trophic structure and mercury distribution in a Gulf of St. Lawrence (Canada) food web using stable isotope analysis

    International Nuclear Information System (INIS)

    Lavoie, Raphael A.; Hebert, Craig E.; Rail, Jean-Francois; Braune, Birgit M.; Yumvihoze, Emmanuel; Hill, Laura G.; Lean, David R.S.

    2010-01-01

    Even at low concentrations in the environment, mercury has the potential to biomagnify in food chains and reaches levels of concern in apex predators. The aim of this study was to relate the transfer of total mercury (THg) and methylmercury (MeHg) in a Gulf of St. Lawrence food web to the trophic structure, from primary consumers to seabirds, using stable nitrogen (δ 15 N) and carbon (δ 13 C) isotope analysis and physical environmental parameters. The energy reaching upper trophic level species was principally derived from pelagic primary production, with particulate organic matter (POM) at the base of the food chain. We developed a biomagnification factor (BMF) taking into account the various prey items consumed by a given predator using stable isotope mixing models. This BMF provides a more realistic estimation than when using a single prey. Lipid content, body weight, trophic level and benthic connection explained 77.4 and 80.7% of the variation in THg and MeHg concentrations, respectively in this food web. When other values were held constant, relationships with lipid and benthic connection were negative whereas relationships with trophic level and body weight were positive. Total Hg and MeHg biomagnified in this food web with biomagnification power values (slope of the relationship with δ 15 N) of 0.170 and 0.235, respectively on wet weight and 0.134 and 0.201, respectively on dry weight. Values of biomagnification power were greater for pelagic and benthopelagic species compared to benthic species whereas the opposite trend was observed for levels at the base of the food chain. This suggests that Hg would be readily bioavailable to organisms at the base of the benthic food chain, but trophic transfer would be more efficient in each trophic level of pelagic and benthopelagic food chains.

  8. Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition.

    Science.gov (United States)

    Potapov, Anton M; Tiunov, Alexei V; Scheu, Stefan

    2018-06-19

    Despite the major importance of soil biota in nutrient and energy fluxes, interactions in soil food webs are poorly understood. Here we provide an overview of recent advances in uncovering the trophic structure of soil food webs using natural variations in stable isotope ratios. We discuss approaches of application, normalization and interpretation of stable isotope ratios along with methodological pitfalls. Analysis of published data from temperate forest ecosystems is used to outline emerging concepts and perspectives in soil food web research. In contrast to aboveground and aquatic food webs, trophic fractionation at the basal level of detrital food webs is large for carbon and small for nitrogen stable isotopes. Virtually all soil animals are enriched in 13 C as compared to plant litter. This 'detrital shift' likely reflects preferential uptake of 13 C-enriched microbial biomass and underlines the importance of microorganisms, in contrast to dead plant material, as a major food resource for the soil animal community. Soil organic matter is enriched in 15 N and 13 C relative to leaf litter. Decomposers inhabiting mineral soil layers therefore might be enriched in 15 N resulting in overlap in isotope ratios between soil-dwelling detritivores and litter-dwelling predators. By contrast, 13 C content varies little between detritivores in upper litter and in mineral soil, suggesting that they rely on similar basal resources, i.e. little decomposed organic matter. Comparing vertical isotope gradients in animals and in basal resources can be a valuable tool to assess trophic interactions and dynamics of organic matter in soil. As indicated by stable isotope composition, direct feeding on living plant material as well as on mycorrhizal fungi is likely rare among soil invertebrates. Plant carbon is taken up predominantly by saprotrophic microorganisms and channelled to higher trophic levels of the soil food web. However, feeding on photoautotrophic microorganisms and non

  9. POTENTIAL FOR DEVELOPMENT OF INTEGRATED MULTI-TROPHIC AQUACULTURE (IMTA IN THE ADRIATIC SEA

    Directory of Open Access Journals (Sweden)

    Danijel Kanski

    2012-12-01

    Full Text Available Over recent years, scientific interest for investigating ecological, economical and social effects of Integrated Multi-trophic Aquaculture (IMTA has increased worldwide. Its development in the Mediterranean, including the Adriatic Sea, is still in the early stages. The main obstacle preventing IMTA to be commercially adopted is the lack of scientific information on choosing compatible species, knowing the carrying capacity of a production area and interactions between species feeding at different trophic levels, as well as its socio–economic impacts. Current experience in the area is based on smaller experimental studies of local importance but they generally give a good insight into potential of IMTA and its interactions with the environment. The aim of this paper was to overview current literature and experiences worldwide and to review the potential for adopting IMTA principles in the Adriatic Sea.

  10. Toxicity and trophic transfer of P25 TiO2 NPs from Dunaliella salina to Artemia salina: Effect of dietary and waterborne exposure.

    Science.gov (United States)

    Bhuvaneshwari, M; Thiagarajan, Vignesh; Nemade, Prateek; Chandrasekaran, N; Mukherjee, Amitava

    2018-01-01

    The recent increase in nanoparticle (P25 TiO 2 NPs) usage has led to concerns regarding their potential implications on environment and human health. The food chain is the central pathway for nanoparticle transfer from lower to high trophic level organisms. The current study relies on the investigation of toxicity and trophic transfer potential of TiO 2 NPs from marine algae Dunaliella salina to marine crustacean Artemia salina. Toxicity was measured in two different modes of exposure such as waterborne (exposure of TiO 2 NPs to Artemia) and dietary exposure (NP-accumulated algal cells are used to feed the Artemia). The toxicity and accumulation of TiO 2 NPs in marine algae D. salina were also studied. Artemia was found to be more sensitive to TiO 2 NPs (48h LC 50 of 4.21mgL -1 ) as compared to marine algae, D. salina (48h LC 50 of 11.35mgL -1 ). The toxicity, uptake, and accumulation of TiO 2 NPs were observed to be more in waterborne exposure as compared to dietary exposure. Waterborne exposure seemed to cause higher ROS production and antioxidant enzyme (SOD and CAT) activity as compared to dietary exposure of TiO 2 NPs in Artemia. There were no observed biomagnification (BMF) and trophic transfer from algae to Artemia through dietary exposure. Histopathological studies confirmed the morphological and internal damages in Artemia. This study reiterates the possible effects of the different modes of exposure on trophic transfer potential of TiO 2 NPs and eventually the consequences on aquatic environment. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. [Trophic niche partitioning of pelagic sharks in Central Eastern Pacific inferred from stable isotope analysis.

    Science.gov (United States)

    Li, Yun Kai; Gao, Xiao di; Wang, Lin Yu; Fang, Lin

    2018-01-01

    As the apex predators of the open ocean ecosystems, pelagic sharks play important roles in stabilizing the marine food web through top-down control. Stable isotope analysis is a powerful tool to investigate the feeding ecology. The carbon and nitrogen isotope ratios can be used to trace food source and evaluate the trophic position of marine organisms. In this study, the isotope values of 130 pelagic sharks from 8 species in Central Eastern Pacific were analyzed and their trophic position and niche were calculated to compare the intra/inter-specific resource partitioning in the Central Eastern Pacific ecosystem. The results exhibited significant differences in both carbon and nitrogen isotope values among the shark species. The trophic levels ranged from 4.3 to 5.4 in the Central Eastern Pacific shark community. The trophic niche of blue sharks and shortfin mako sharks showed no overlap with the other shark species, exhibiting unique ecological roles in the open ocean food web. These data highlighted the diverse roles among pelagic sharks, supporting previous findings that this species is not trophically redundant and the trophic niche of pelagic sharks can not be simply replaced by those of other top predator species.

  12. Trophically available metal - A variable feast

    International Nuclear Information System (INIS)

    Rainbow, Philip S.; Luoma, Samuel N.; Wang Wenxiong

    2011-01-01

    Assimilation of trace metals by predators from prey is affected by the physicochemical form of the accumulated metal in the prey, leading to the concept of a Trophically Available Metal (TAM) component in the food item definable in terms of particular subcellular fractions of accumulated metal. As originally defined TAM consists of soluble metal forms and metal associated with cell organelles, the combination of separated fractions which best explained particular results involving a decapod crustacean predator feeding on bivalve mollusc tissues. Unfortunately TAM as originally defined has subsequently frequently been used in the literature as an absolute description of that component of accumulated metal that is trophically available in all prey to all consumers. It is now clear that what is trophically available varies between food items, consumers and metals. TAM as originally defined should be seen as a useful starting hypothesis, not as a statement of fact. - Trophically Available Metal (TAM), the component of accumulated metal in food that is taken up by a feeding animal, varies with food type and consumer.

  13. Trophically available metal - A variable feast

    Energy Technology Data Exchange (ETDEWEB)

    Rainbow, Philip S., E-mail: p.rainbow@nhm.ac.uk [Department of Zoology, Natural History Museum, Cromwell Rd, London SW7 5BD (United Kingdom); Luoma, Samuel N. [Department of Zoology, Natural History Museum, Cromwell Rd, London SW7 5BD (United Kingdom); John Muir Institute of the Environment, University of California, Davis, CA 95616 (United States); Wang Wenxiong [College of Marine and Environmental Sciences, State Key Laboratory for Marine Environmental Sciences, Xiamen University, Fujian (China)

    2011-10-15

    Assimilation of trace metals by predators from prey is affected by the physicochemical form of the accumulated metal in the prey, leading to the concept of a Trophically Available Metal (TAM) component in the food item definable in terms of particular subcellular fractions of accumulated metal. As originally defined TAM consists of soluble metal forms and metal associated with cell organelles, the combination of separated fractions which best explained particular results involving a decapod crustacean predator feeding on bivalve mollusc tissues. Unfortunately TAM as originally defined has subsequently frequently been used in the literature as an absolute description of that component of accumulated metal that is trophically available in all prey to all consumers. It is now clear that what is trophically available varies between food items, consumers and metals. TAM as originally defined should be seen as a useful starting hypothesis, not as a statement of fact. - Trophically Available Metal (TAM), the component of accumulated metal in food that is taken up by a feeding animal, varies with food type and consumer.

  14. Exploring the Hg pollution in global marginal seas by trophic biomagnification in demersal fishes

    Science.gov (United States)

    Tseng, C. M.; Hsieh, Y. C.; Chiang, C. Y.; Lamborg, C. H.; Chang, N. N.; Shiao, J. C.

    2017-12-01

    Limited knowledge still exists concerning the effects of size composition and trophic level (TL) on mercury levels in the demersal fishes associated with human activities in the marginal seas. In this study, we found evidence of strong control of TL on the Hg in fish and its biomagnification via food webs in the ECS. Total Hg in seven selected fish species, collected during the cruise OR1- 890 in July 2009, ranged from 2.6 and 256.2 ng g-1 (n=72). There were good linear relationships between Hg concentrations and fish body length (R2 = 0.79) and weight (R2 = 0.82), respectively, other than environmental variables (R2 = 0 0.03). It indicates that the Hg concentration in fish is mainly controlled by the growth mechanism of the fish itself through food chain transfer. In order to investigate how Hg levels in fish through trophic magnification associated with environmental changes, we hence developed the empirical method to calculate Hg accumulation rate (MAR) via the relationship of Hg concentration with the fish age for each fish species. The results further showed a significantly positive correlation of MAR with trophic levels, which relationship is Ln MAR =6.1 TL-15.8 (R2 = 0.89) in the ECS shelf. The magnitude of the slope (δMAR/δTL) as a biomagnification index of demersal fish shall provide the feasibility to compare Hg pollution situation among different marine ecosystems. Globally, the biomagnification indicator in the demersal fishes of the ECS is much greater than those in other marginal seas, suggesting high regional Hg pollution impacts from Mainland China.

  15. Fish communities and trophic metrics as measures of ecological degradation: a case study in the tributaries of the river Ganga basin, India.

    Science.gov (United States)

    Dubey, Vineet Kumar; Sarkar, Uttam Kumar; Pandey, Ajay; Lakra, Wazir Singh

    2013-09-01

    In India, freshwater aquatic resources are suffering from increasing human population, urbanization and shortage of all kind of natural resources like water. To mitigate this, all the major rivers have been planned for a river-interlinking through an interlinking canal system under a huge scheme; yet, the baseline information on ecological conditions of those tropical rivers and their fish communities is lacking at present. In view of that, the present study was undertaken to assess the ecological condition by comparing the trophic metrics of the fish community, conservation status and water chemistry of the two tropical rivers of the Ganga basin, from October 2007 to November 2009. The analysis of trophic niches of the available fish species indicated dominancy of carnivorous (19 species) in river Ken and omnivorous (23 species) in Betwa. The trophic level score of carnivorous species was recorded similar (33.33%) in both rivers, whereas omnivorous species were mostly found in Betwa (36.51%) than Ken (28.07%). Relatively undisturbed sites of Betwa (B1, B2 and B3) and Ken (K2, K3 and K5) were characterized by diverse fish fauna and high richness of threatened species. The higher mean trophic level scores were recorded at B4 of Betwa and K4 of Ken. The Bray-Curtis index for trophic level identified the carnivorous species (> 0.32) as an indicator species for pollution. Anthropogenic exposure, reflected in water quality as well as in fish community structure, was found higher especially in the lower stretches of both rivers. Our results suggest the importance of trophic metrics on fish community, for ecological conditions evaluation, which enables predictions on the effect of future morphodynamic changes (in the post-interlinking phases), and provide a framework and reference condition to support restoration efforts of relatively altered fish habitats in tropical rivers of India.

  16. Fish communities and trophic metrics as measures of ecological degradation: a case study in the tributaries of the river Ganga basin, India

    Directory of Open Access Journals (Sweden)

    Vineet Kumar Dubey

    2013-09-01

    Full Text Available In India, freshwater aquatic resources are suffering from increasing human population, urbanization and shortage of all kind of natural resources like water. To mitigate this, all the major rivers have been planned for a river-interlinking through an interlinking canal system under a huge scheme; yet, the baseline information on ecological conditions of those tropical rivers and their fish communities is lacking at present. In view of that, the present study was undertaken to assess the ecological condition by comparing the trophic metrics of the fish community, conservation status and water chemistry of the two tropical rivers of the Ganga basin, from October 2007 to November 2009. The analysis of trophic niches of the available fish species indicated dominancy of carnivorous (19 species in river Ken and omnivorous (23 species in Betwa. The trophic level score of carnivorous species was recorded similar (33.33% in both rivers, whereas omnivorous species were mostly found in Betwa (36.51% than Ken (28.07%. Relatively undisturbed sites of Betwa (B1, B2 and B3 and Ken (K2, K3 and K5 were characterized by diverse fish fauna and high richness of threatened species. The higher mean trophic level scores were recorded at B4 of Betwa and K4 of Ken. The Bray-Curtis index for trophic level identified the carnivorous species (>0.32 as an indicator species for pollution. Anthropogenic exposure, reflected in water quality as well as in fish community structure, was found higher especially in the lower stretches of both rivers. Our results suggest the importance of trophic metrics on fish community, for ecological conditions evaluation, which enables predictions on the effect of future morphodynamic changes (in the post-interlinking phases, and provide a framework and reference condition to support restoration efforts of relatively altered fish habitats in tropical rivers of India.

  17. Modelling impacts of offshore wind farms on trophic web: the Courseulles-sur-Mer case study

    Science.gov (United States)

    Raoux, Aurore; Pezy, Jean-Philippe; Dauvin, Jean-Claude; Tecchio, samuele; Degraer, Steven; Wilhelmsson, Dan; Niquil, Nathalie

    2016-04-01

    The French government is planning the construction of three offshore wind farms in Normandy. These offshore wind farms will integrate into an ecosystem already subject to a growing number of anthropogenic disturbances such as transportation, fishing, sediment deposit, and sediment extraction. The possible effects of this cumulative stressors on ecosystem functioning are still unknown, but they could impact their resilience, making them susceptible to changes from one stable state to another. Understanding the behaviour of these marine coastal complex systems is essential in order to anticipate potential state changes, and to implement conservation actions in a sustainable manner. Currently, there are no global and integrated studies on the effects of construction and exploitation of offshore wind farms. Moreover, approaches are generally focused on the conservation of some species or groups of species. Here, we develop a holistic and integrated view of ecosystem impacts through the use of trophic webs modelling tools. Trophic models describe the interaction between biological compartments at different trophic levels and are based on the quantification of flow of energy and matter in ecosystems. They allow the application of numerical methods for the characterization of emergent properties of the ecosystem, also called Ecological Network Analysis (ENA). These indices have been proposed as ecosystem health indicators as they have been demonstrated to be sensitive to different impacts on marine ecosystems. We present here in detail the strategy for analysing the potential environmental impacts of the construction of the Courseulles-sur-Mer offshore wind farm (Bay of Seine) such as the reef effect through the use of the Ecopath with Ecosim software. Similar Ecopath simulations will be made in the future on the Le Tréport offshore wind farm site. Results will contribute to a better knowledge of the impacts of the offshore wind farms on ecosystems. They also allow to

  18. Drivers of trophic amplification of ocean productivity trends in a changing climate

    Science.gov (United States)

    Stock, C. A.; Dunne, J. P.; John, J. G.

    2014-07-01

    Pronounced projected 21st century trends in regional oceanic net primary production (NPP) raise the prospect of significant redistributions of marine resources. Recent results further suggest that NPP changes may be amplified at higher trophic levels. Here, we elucidate the role of planktonic food web dynamics in driving projected changes in mesozooplankton production (MESOZP) found to be, on average, twice as large as projected changes in NPP by the latter half of the 21st century under a high emissions scenario. Globally, MESOZP was projected to decline by 7.9% but regional MESOZP changes sometimes exceeded 50%. Changes in three planktonic food web properties - zooplankton growth efficiency (ZGE), the trophic level of mesozooplankton (MESOTL), and the fraction of NPP consumed by zooplankton (zooplankton-phytoplankton coupling, ZPC), were demonstrated to be responsible for the projected amplification. Zooplankton growth efficiencies (ZGE) changed with NPP, amplifying both NPP increases and decreases. Negative amplification (i.e., exacerbation) of projected subtropical NPP declines via this mechanism was particularly strong since consumers in the subtropics already have limited surplus energy above basal metabolic costs. Increased mesozooplankton trophic level (MESOTL) resulted from projected declines in large phytoplankton production, the primary target of herbivorous mesozooplankton. This further amplified negative subtropical NPP declines but was secondary to ZGE and, at higher latitudes, was often offset by increased ZPC. Marked ZPC increases were projected for high latitude regions experiencing shoaling of deep winter mixing or decreased winter sea ice - both tending to increase winter zooplankton biomass and enhance grazer control of spring blooms. Increased ZPC amplified projected NPP increases associated with declining sea ice in the Artic and damped projected NPP declines associated with decreased mixing in the Northwest Atlantic and Southern Ocean

  19. Influence of relative trophic position and carbon source on selenium bioaccumulation in turtles from a coal fly-ash spill site

    International Nuclear Information System (INIS)

    Van Dyke, James U.; Hopkins, William A.; Jackson, Brian P.

    2013-01-01

    Selenium (Se) is a bioaccumulative constituent of coal fly-ash that can disrupt reproduction of oviparous wildlife. In food webs, the greatest enrichment of Se occurs at the lowest trophic levels, making it readily bioavailable to higher consumers. However, subsequent enrichment at higher trophic levels is less pronounced, leading to mixed tendencies for Se to biomagnify. We used stable isotopes ( 15 N and 13 C) in claws to infer relative trophic positions and relative carbon sources, respectively, of seven turtle species near the site of a recently-remediated coal fly-ash spill. We then tested whether Se concentrations differed with relative trophic position or relative carbon source. We did not observe a strong relationship between δ 15 N and Se concentration. Instead, selenium concentrations decreased with increasing δ 13 C among species. Therefore, in an assemblage of closely-related aquatic vertebrates, relative carbon source was a better predictor of Se bioaccumulation than was relative trophic position. -- Highlights: •Stable isotope results showed trophic separation among turtle species. •Selenium concentrations did not biomagnify with relative trophic position. •Selenium concentrations decreased with increasing δ 13 C among species. •Carbon source influenced Se bioaccumulation in an assemblage of related vertebrates. -- Stable isotope differences indicate that claw selenium concentrations differ among relative carbon sources, and not among relative trophic positions, in an assemblage of aquatic turtles

  20. Meta-analysis of amino acid stable nitrogen isotope ratios for estimating trophic position in marine organisms.

    Science.gov (United States)

    Nielsen, Jens M; Popp, Brian N; Winder, Monika

    2015-07-01

    Estimating trophic structures is a common approach used to retrieve information regarding energy pathways, predation, and competition in complex ecosystems. The application of amino acid (AA) compound-specific nitrogen (N) isotope analysis (CSIA) is a relatively new method used to estimate trophic position (TP) and feeding relationships in diverse organisms. Here, we conducted the first meta-analysis of δ(15)N AA values from measurements of 359 marine species covering four trophic levels, and compared TP estimates from AA-CSIA to literature values derived from food items, gut or stomach content analysis. We tested whether the AA trophic enrichment factor (TEF), or the (15)N enrichment among different individual AAs is constant across trophic levels and whether inclusion of δ(15)N values from multiple AAs improves TP estimation. For the TEF of glutamic acid relative to phenylalanine (Phe) we found an average value of 6.6‰ across all taxa, which is significantly lower than the commonly applied 7.6‰. We found that organism feeding ecology influences TEF values of several trophic AAs relative to Phe, with significantly higher TEF values for herbivores compared to omnivores and carnivores, while TEF values were also significantly lower for animals excreting urea compared to ammonium. Based on the comparison of multiple model structures using the metadata of δ(15)N AA values we show that increasing the number of AAs in principle improves precision in TP estimation. This meta-analysis clarifies the advantages and limitations of using individual δ(15)N AA values as tools in trophic ecology and provides a guideline for the future application of AA-CSIA to food web studies.

  1. Influence of dispersants on trophic transfer of petroleum hydrocarbons in a marine food chain

    International Nuclear Information System (INIS)

    Wolfe, M. F.; Schwartz, G. J. B.; Singaram, S.; Tjeerdema, R. S.

    1997-01-01

    Experiments were conducted to determine the impact of dispersing agents on petroleum hydrocarbons (PH) bioavailability and trophic transfer in primary levels of a marine food chain. Uptake, bioaccumulation and metabolic transformation of a model PH, ( 1 4C)naphthalene, were measured and compared with Prudhoe Bay Crude Oil (PBCO) dispersed with Corexit 9527, and undispersed preparations of PBCO. The model food chain consisted of a primary algae producer and a primary rotifer consumer. Results showed that uptake of naphthalene increased significantly in the presence of a dispersant in algae. A significant increase in uptake was also recorded in rotifers via trophic transfer. Trophic transfer played a significant, sometimes even dominant, role in uptake and bioaccumulation. 27 refs., 6 figs

  2. Animal water balance drives top-down effects in a riparian forest-implications for terrestrial trophic cascades.

    Science.gov (United States)

    McCluney, Kevin E; Sabo, John L

    2016-08-17

    Despite the clear importance of water balance to the evolution of terrestrial life, much remains unknown about the effects of animal water balance on food webs. Based on recent research suggesting animal water imbalance can increase trophic interaction strengths in cages, we hypothesized that water availability could drive top-down effects in open environments, influencing the occurrence of trophic cascades. We manipulated large spider abundance and water availability in 20 × 20 m open-air plots in a streamside forest in Arizona, USA, and measured changes in cricket and small spider abundance and leaf damage. As expected, large spiders reduced both cricket abundance and herbivory under ambient, dry conditions, but not where free water was added. When water was added (free or within moist leaves), cricket abundance was unaffected by large spiders, but spiders still altered herbivory, suggesting behavioural effects. Moreover, we found threshold-type increases in herbivory at moderately low soil moisture (between 5.5% and 7% by volume), suggesting the possibility that water balance may commonly influence top-down effects. Overall, our results point towards animal water balance as an important driver of direct and indirect species interactions and food web dynamics in terrestrial ecosystems. © 2016 The Author(s).

  3. Laboratory and field assessment of uranium trophic transfer efficiency in the crayfish Orconectes limosus fed the bivalve C. fluminea

    International Nuclear Information System (INIS)

    Simon, Olivier; Garnier-Laplace, Jacqueline

    2005-01-01

    At present, ecotoxicological information regarding the impact of natural uranium (U) on freshwater ecosystems via the trophic contamination route is scarce. We generated an experimental trophic food chain involving the prey species, Corbicula fluminea, and a predator, Orconectes limosus, for a 10-day and a 30-day feeding periods (food ration: one whole soft body/day/crayfish). We studied the efficiency of U trophic transfer and the distribution of U in the predator. During the test, we varied the quantity of dietary U (from beforehand contaminated bivalves at concentrations ranging from 0.9 ± 0.1 to 20.2 ± 9 μg/g fw provided to each crayfish over the 10 days) applying a daily feeding rate equal to 3.9 ± 0.8% fw. The efficiency of U trophic transfer from clams to crayfish varied between 1 and 13% depending on the prey exposure modalities. Accumulation of U was observed in the digestive gland but also in gills, in the muscle, and in the molt of the crayfish after trophic exposure treatments. Under high-level exposure conditions, the digestive gland was the main target-organ, however a significant accumulation was also observed in the stomach. With regard to low levels of trophic exposure, accumulation of U in gills, in the stomach, and in the digestive gland was of the same order of magnitude. Longer exposure period which incorporated a crayfish molt, resulted in a decrease of trophic transfer ratio and a modified U tissue distribution

  4. The exploration of trophic structure modeling using mass balance Ecopath model of Tangerang coastal waters

    Science.gov (United States)

    Dewi, N. N.; Kamal, M.; Wardiatno, Y.; Rozi

    2018-04-01

    Ecopath model approach was used to describe trophic interaction, energy flows and ecosystem condition of Tangerang coastal waters. This model consists of 42 ecological groups, of which 41 are living groups and one is a detritus group. Trophic levels of these groups vary between 1.0 (for primary producers and detritus) to 4.03 (for tetraodontidae). Groups with trophic levels 2≤TLfish, while detritus has a positive impact on the majority of demersal fish. Leiognathidae havea negative impact on phytoplankton, zooplankton and several other groups. System omnivory index for this ecosystem is 0.151. System primary production/respiration (P/R) ratio of Tangerang coastal waters is 1.505. This coastal ecosystem is an immatureecosystem because it hasdegraded. Pedigree index for this model is 0.57. This model describes ecosystem condition affected by overfishing and antropogenic activities. Therefore, through Ecopath model we provide some suggestions about the ecosystem-based fisheries management.

  5. Trophic complexity and the adaptive value of damage-induced plant volatiles.

    Directory of Open Access Journals (Sweden)

    Ian Kaplan

    Full Text Available Indirect plant defenses are those facilitating the action of carnivores in ridding plants of their herbivorous consumers, as opposed to directly poisoning or repelling them. Of the numerous and diverse indirect defensive strategies employed by plants, inducible volatile production has garnered the most fascination among plant-insect ecologists. These volatile chemicals are emitted in response to feeding by herbivorous arthropods and serve to guide predators and parasitic wasps to their prey. Implicit in virtually all discussions of plant volatile-carnivore interactions is the premise that plants "call for help" to bodyguards that serve to boost plant fitness by limiting herbivore damage. This, by necessity, assumes a three-trophic level food chain where carnivores benefit plants, a theoretical framework that is conceptually tractable and convenient, but poorly depicts the complexity of food-web dynamics occurring in real communities. Recent work suggests that hyperparasitoids, top consumers acting from the fourth trophic level, exploit the same plant volatile cues used by third trophic level carnivores. Further, hyperparasitoids shift their foraging preferences, specifically cueing in to the odor profile of a plant being damaged by a parasitized herbivore that contains their host compared with damage from an unparasitized herbivore. If this outcome is broadly representative of plant-insect food webs at large, it suggests that damage-induced volatiles may not always be beneficial to plants with major implications for the evolution of anti-herbivore defense and manipulating plant traits to improve biological control in agricultural crops.

  6. Food wastes as fish feeds for polyculture of low-trophic-level fish: bioaccumulation and health risk assessments of heavy metals in the cultured fish.

    Science.gov (United States)

    Cheng, Zhang; Lam, Cheung-Lung; Mo, Wing-Yin; Nie, Xiang-Ping; Choi, Wai-Ming; Man, Yu-Bon; Wong, Ming-Hung

    2016-04-01

    The major purpose of this study was to use different types of food wastes which serve as the major sources of protein to replace the fish meal used in fish feeds to produce quality fish. Two types of food waste-based feed pellets FW A (with cereals) and FW B (with cereals and meat products) and the commercial feed Jinfeng® were used to culture fingerlings of three low-trophic-level fish species: bighead carp, grass carp, and mud carp (in the ratio of 1:3:1) for 1 year period in the Sha Tau Kok Organic Farm in Hong Kong. Heavy metal concentrations in all of the fish species fed with food waste pellets and commercial pellets in Sha Tau Kok fish ponds were all below the local and international maximum permissible levels in food. Health risk assessments indicated that human consumption of the fish fed with food waste feed pellets was safe for the Hong Kong residents. The present results revealed that recycling of food waste for cultivating low-trophic-level fish (mainly herbivores and detritus feeders) is feasible, and at the same time will ease the disposal pressure of food waste, a common problem of densely populated cities like Hong Kong.

  7. Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae).

    Science.gov (United States)

    Litsios, Glenn; Pellissier, Loïc; Forest, Félix; Lexer, Christian; Pearman, Peter B; Zimmermann, Niklaus E; Salamin, Nicolas

    2012-09-22

    The rate of environmental niche evolution describes the capability of species to explore the available environmental space and is known to vary among species owing to lineage-specific factors. Trophic specialization is a main force driving species evolution and is responsible for classical examples of adaptive radiations in fishes. We investigate the effect of trophic specialization on the rate of environmental niche evolution in the damselfish, Pomacentridae, which is an important family of tropical reef fishes. First, phylogenetic niche conservatism is not detected in the family using a standard test of phylogenetic signal, and we demonstrate that the environmental niches of damselfishes that differ in trophic specialization are not equivalent while they still overlap at their mean values. Second, we estimate the relative rates of niche evolution on the phylogenetic tree and show the heterogeneity among rates of environmental niche evolution of the three trophic groups. We suggest that behavioural characteristics related to trophic specialization can constrain the evolution of the environmental niche and lead to conserved niches in specialist lineages. Our results show the extent of influence of several traits on the evolution of the environmental niche and shed new light on the evolution of damselfishes, which is a key lineage in current efforts to conserve biodiversity in coral reefs.

  8. Trophic interactions among the heterotrophic components of plankton in man-made peat pools

    Directory of Open Access Journals (Sweden)

    Michał Niedźwiecki

    2017-03-01

    Full Text Available Man-made peat pools are permanent freshwater habitats developed due to non-commercial man-made peat extraction. Yet, they have not been widely surveyed in terms of ecosystem functioning, mainly regarding the complexity of heterotrophic components of the plankton. In this study we analysed distribution and trophic interrelations among heterotrophic plankton in man-made peat pools located in different types of peatbogs. We found that peat pools showed extreme differences in environmental conditions that occurred to be important drivers of distribution of microplankton and metazooplankton. Abundance of bacteria and protozoa showed significant differences, whereas metazooplankton was less differentiated in density among peat pools. In all peat pools stress-tolerant species of protozoa and metazoa were dominant. In each peat pool five trophic functional groups were distinguished. The abundance of lower functional trophic groups (bacteria, heterotrophic nanoflagellates (HNF and ciliates feeding on bacteria and HNF was weakly influenced by environmental drivers and was highly stable in all peat pool types. Higher functional trophic groups (naupli, omnivorous and carnivorous ciliates, cladocerans, adult copepods and copepodites were strongly influenced by environmental variables and exhibited lower stability. Our study contributes to comprehensive knowledge of the functioning of peat bogs, as our results have shown that peat pools are characterized by high stability of the lowest trophic levels, which can be crucial for energy transfer and carbon flux through food webs.

  9. Trophic interactions in changing landscapes: responses of soil food webs.

    NARCIS (Netherlands)

    Hedlund, K.; Griffiths, B.; Christensen, S.; Scheu, S.; Setälä, H.; Tscharntke, T.; Verhoef, H.A.

    2004-01-01

    Soil communities in landscapes that are rapidly changing due to a range of anthropogenic processes can be regarded as highly transient systems where interactions between competing species or trophic levels may be seriously disrupted. In disturbed communities dispersal in space and time has a role in

  10. Trophic transfer of toxic elements in the estuarine invertebrate and fish food web of Daliao River, Liaodong Bay, China

    International Nuclear Information System (INIS)

    Guo, Bobo; Jiao, Deqi; Wang, Jing; Lei, Kai; Lin, Chunye

    2016-01-01

    In order to study element accumulation and trophic transfer in the food web, sixteen benthic invertebrate species and nine fish species were collected from the Daliao River estuary for analysis of toxic elements and nitrogen stable isotope in the muscle tissue. The concentrations ranged between 1.44–17.98, 0.01–9.30, 0.17–36.15, 0.7–145.4, 0.01–0.33, 0.14–14.88, 0.10–2.51, 0.02–0.14, and 19.3–221.1 mg kg −1 for As, Cd, Cu, Hg, Ni, Pb, Sb, and Zn, respectively. As, Cd, Cu, and Zn were significantly higher in the benthic invertebrates than in fish, whereas Hg and Sb were significantly lower. In addition, the benthic invertebrates were characterized by the highest bioaccumulation factor (BAF) for Cd, whereas the fish were characterized by the highest BAF for Hg. A significant decrease in Cd, Cr, Cu, and Ni levels, and a significant increase in Hg and Sb levels were observed with increasing trophic levels. - Highlights: • Toxic elements and trophic level were determined in biota from Daliao River estuary. • Benthic invertebrates had higher As, Cd, Cu, Zn and lower Hg and Sb levels than fish. • Benthic invertebrates accumulated high As levels, while fish accumulated high Hg levels. • Cd, Cr, Cu, Ni levels decreased, and Hg and Sb levels increased with trophic levels.

  11. Tempo of trophic evolution and its impact on mammalian diversification.

    Science.gov (United States)

    Price, Samantha A; Hopkins, Samantha S B; Smith, Kathleen K; Roth, V Louise

    2012-05-01

    Mammals are characterized by the complex adaptations of their dentition, which are an indication that diet has played a critical role in their evolutionary history. Although much attention has focused on diet and the adaptations of specific taxa, the role of diet in large-scale diversification patterns remains unresolved. Contradictory hypotheses have been proposed, making prediction of the expected relationship difficult. We show that net diversification rate (the cumulative effect of speciation and extinction), differs significantly among living mammals, depending upon trophic strategy. Herbivores diversify fastest, carnivores are intermediate, and omnivores are slowest. The tempo of transitions between the trophic strategies is also highly biased: the fastest rates occur into omnivory from herbivory and carnivory and the lowest transition rates are between herbivory and carnivory. Extant herbivore and carnivore diversity arose primarily through diversification within lineages, whereas omnivore diversity evolved by transitions into the strategy. The ability to specialize and subdivide the trophic niche allowed herbivores and carnivores to evolve greater diversity than omnivores.

  12. Effects of sexual dimorphism and landscape composition on the trophic behavior of Greater Prairie-Chicken.

    Directory of Open Access Journals (Sweden)

    Beatriz Blanco-Fontao

    Full Text Available Partitioning of ecological niche is expected in lekking species that show marked sexual size dimorphism as a consequence of sex-specific ecological constraints. However, niche partitioning is uncertain in species with moderate sexual dimorphism. In addition, the ecological niche of a species may also be affected by landscape composition; particularly, agricultural fragmentation may greatly influence the trophic behavior of herbivores. We studied trophic niche variation in Greater Prairie-Chickens (Tympanuchus cupido, a grouse species that shows moderate sex-dimorphism. Greater Prairie-Chickens are native to tallgrass prairies of North America, although populations persist in less natural mosaics of cropland and native habitats. We used stable isotope analysis of carbon and nitrogen in blood, claws and feathers to assess seasonal differences in trophic niche breadth and individual specialization between male and female Greater Prairie-Chickens, and between birds living in continuous and fragmented landscapes. We found that females showed broader niches and higher individual specialization than males, especially in winter and autumn. However, differences between females and males were smaller in spring when birds converge at leks, suggesting that females and males may exhibit similar feeding behaviors during the lekking period. In addition, we found that birds living in native prairies showed greater annual trophic variability than conspecifics in agricultural mosaic landscapes. Native habitats may provide greater dietary diversity, resulting in greater diversity of feeding strategies.

  13. V.I. Vernadskiy study of biochemical cycles and role of biocenoses trophic structure in their stabilization under background conditions and at chemical pollution

    International Nuclear Information System (INIS)

    Bezel, V.S.; Bel'skij, E.A.; Bel'skaya, E.A.; Zhujkova, T.V.; Mukhacheva, S.V.; Nesterkov, A.V.

    2008-01-01

    In the present report the participation of different trophic belonging organisms in biogeochemical cycles at the pollution of the environment by aerogenic emissions of metallurgical enterprises are discussed. Investigation in and around southern taiga of Middle Ural in liable to heavy metals contamination areas was made. Several areas with different level of soil contamination from background uncontaminated (at a distance 20-30 km from emission source) to buffer (4-7 km) and impact (1-2 km) were separated out. Mechanism of chemical elements accumulation by different components of terrestrial ecosystems that the aggregate of trophic levels present: depository environment (soil), producers (plants), consumers of several levels (phytophages, zoophages) was studied. Accumulation of chemical elements was considered in biomass of trophic levels both with content of chemical elements in the soil on a regional background level and by their intensive contamination. The findings enable to evaluate the quantity of chemical elements involved in biogenic cycles by different trophic belonging organisms

  14. Unintended consequences of management actions in salt pond restoration: cascading effects in trophic interactions.

    Science.gov (United States)

    Takekawa, John Y; Ackerman, Joshua T; Brand, L Arriana; Graham, Tanya R; Eagles-Smith, Collin A; Herzog, Mark P; Topping, Brent R; Shellenbarger, Gregory G; Kuwabara, James S; Mruz, Eric; Piotter, Sara L; Athearn, Nicole D

    2015-01-01

    Salt evaporation ponds have played an important role as habitat for migratory waterbirds across the world, however, efforts to restore and manage these habitats to maximize their conservation value has proven to be challenging. For example, salinity reduction has been a goal for restoring and managing former salt evaporation ponds to support waterbirds in the South Bay Salt Pond Restoration Project in San Francisco Bay, California, USA. Here, we describe a case study of unexpected consequences of a low-dissolved oxygen (DO) event on trophic interactions in a salt pond system following management actions to reduce salinity concentrations. We document the ramifications of an anoxic event in water quality including salinity, DO, and temperature, and in the response of the biota including prey fish biomass, numerical response by California Gulls (Larus californicus), and chick survival of Forster's Tern (Sterna forsteri). Management actions intended to protect receiving waters resulted in decreased DO concentrations that collapsed to zero for ≥ 4 consecutive days, resulting in an extensive fish kill. DO depletion likely resulted from an algal bloom that arose following transition of the pond system from high to low salinity as respiration and decomposition outpaced photosynthetic production. We measured a ≥ 6-fold increase in biomass of fish dropped on the levee by foraging avian predators compared with weeks prior to and following the low-DO event. California Gulls rapidly responded to the availability of aerobically-stressed and vulnerable fish and increased in abundance by two orders of magnitude. Mark-recapture analysis of 254 Forster's Tern chicks indicated that their survival declined substantially following the increase in gull abundance. Thus, management actions to reduce salinity concentrations resulted in cascading effects in trophic interactions that serves as a cautionary tale illustrating the importance of understanding the interaction of water quality

  15. Unintended consequences of management actions in salt pond restoration: cascading effects in trophic interactions.

    Directory of Open Access Journals (Sweden)

    John Y Takekawa

    Full Text Available Salt evaporation ponds have played an important role as habitat for migratory waterbirds across the world, however, efforts to restore and manage these habitats to maximize their conservation value has proven to be challenging. For example, salinity reduction has been a goal for restoring and managing former salt evaporation ponds to support waterbirds in the South Bay Salt Pond Restoration Project in San Francisco Bay, California, USA. Here, we describe a case study of unexpected consequences of a low-dissolved oxygen (DO event on trophic interactions in a salt pond system following management actions to reduce salinity concentrations. We document the ramifications of an anoxic event in water quality including salinity, DO, and temperature, and in the response of the biota including prey fish biomass, numerical response by California Gulls (Larus californicus, and chick survival of Forster's Tern (Sterna forsteri. Management actions intended to protect receiving waters resulted in decreased DO concentrations that collapsed to zero for ≥ 4 consecutive days, resulting in an extensive fish kill. DO depletion likely resulted from an algal bloom that arose following transition of the pond system from high to low salinity as respiration and decomposition outpaced photosynthetic production. We measured a ≥ 6-fold increase in biomass of fish dropped on the levee by foraging avian predators compared with weeks prior to and following the low-DO event. California Gulls rapidly responded to the availability of aerobically-stressed and vulnerable fish and increased in abundance by two orders of magnitude. Mark-recapture analysis of 254 Forster's Tern chicks indicated that their survival declined substantially following the increase in gull abundance. Thus, management actions to reduce salinity concentrations resulted in cascading effects in trophic interactions that serves as a cautionary tale illustrating the importance of understanding the interaction

  16. Unintended consequences of management actions in salt pond restoration: cascading effects in trophic interactions

    Science.gov (United States)

    Takekawa, John Y.; Ackerman, Joshua T.; Brand, Arriana; Graham, Tanya R.; Eagles-Smith, Collin A.; Herzog, Mark; Topping, Brent R.; Shellenbarger, Gregory; Kuwabara, James S.; Mruz, Eric; Piotter, Sara L.; Athearn, Nicole D.

    2015-01-01

    Salt evaporation ponds have played an important role as habitat for migratory waterbirds across the world, however, efforts to restore and manage these habitats to maximize their conservation value has proven to be challenging. For example, salinity reduction has been a goal for restoring and managing former salt evaporation ponds to support waterbirds in the South Bay Salt Pond Restoration Project in San Francisco Bay, California, USA. Here, we describe a case study of unexpected consequences of a low-dissolved oxygen (DO) event on trophic interactions in a salt pond system following management actions to reduce salinity concentrations. We document the ramifications of an anoxic event in water quality including salinity, DO, and temperature, and in the response of the biota including prey fish biomass, numerical response by California Gulls (Larus californicus), and chick survival of Forster's Tern (Sterna forsteri). Management actions intended to protect receiving waters resulted in decreased DO concentrations that collapsed to zero for ≥ 4 consecutive days, resulting in an extensive fish kill. DO depletion likely resulted from an algal bloom that arose following transition of the pond system from high to low salinity as respiration and decomposition outpaced photosynthetic production. We measured a ≥ 6-fold increase in biomass of fish dropped on the levee by foraging avian predators compared with weeks prior to and following the low-DO event. California Gulls rapidly responded to the availability of aerobically-stressed and vulnerable fish and increased in abundance by two orders of magnitude. Mark-recapture analysis of 254 Forster's Tern chicks indicated that their survival declined substantially following the increase in gull abundance. Thus, management actions to reduce salinity concentrations resulted in cascading effects in trophic interactions that serves as a cautionary tale illustrating the importance of understanding the interaction of water quality

  17. [Strengths, weaknesses, and opportunities of French research in trophic ecology].

    Science.gov (United States)

    Perga, Marie-Élodie; Danger, Michael; Dubois, Stanislas; Fritch, Clémentine; Gaucherel, Cédric; Hubas, Cedric; Jabot, Franck; Lacroix, Gérard; Lefebvre, Sébastien; Marmonier, Pierre; Bec, Alexandre

    2018-05-30

    The French National Institute of Ecology and Environment (INEE) aims at fostering pluridisciplinarity in Environmental Science and, for that purpose, funds ex muros research groups (GDR) on thematic topics. Trophic ecology has been identified as a scientific field in ecology that would greatly benefit from such networking activity, as being profoundly scattered. This has motivated the seeding of a GDR, entitled "GRET". The contours of the GRET's action, and its ability to fill these gaps within trophic ecology at the French national scale, will depend on the causes of this relative scattering. This study relied on a nationally broadcasted poll aiming at characterizing the field of trophic ecology in France. Amongst all the unique individuals that fulfilled the poll, over 300 belonged at least partly to the field of trophic ecology. The sample included all French public research institutes and career stages. Three main disruptions within the community of scientist in trophic ecology were identified. The first highlighted the lack of interfaces between microbial and trophic ecology. The second evidenced that research questions were strongly linked to single study fields or ecosystem type. Last, research activities are still quite restricted to the ecosystem boundaries. All three rupture points limit the conceptual and applied progression in the field of trophic ecology. Here we show that most of the disruptions within French Trophic Ecology are culturally inherited, rather than motivated by scientific reasons or justified by socio-economic stakes. Comparison with the current literature confirms that these disruptions are not necessarily typical of the French research landscape, but instead echo the general weaknesses of the international research in ecology. Thereby, communication and networking actions within and toward the community of trophic ecologists, as planned within the GRET's objectives, should contribute to fill these gaps, by reintegrating microbes within

  18. Analysis of trophic interactions reveals highly plastic response to climate change in a tri-trophic High-Arctic ecosystem

    DEFF Research Database (Denmark)

    Mortensen, Lars O.; Schmidt, Niels Martin; Hoye, Toke T.

    2016-01-01

    As a response to current climate changes, individual species have changed various biological traits, illustrating an inherent phenotypic plasticity. However, as species are embedded in an ecological network characterised by multiple consumer-resource interactions, ecological mismatches are likely...... to arise when interacting species do not respond homogeneously. The approach of biological networks analysis calls for the use of structural equation modelling (SEM), a multidimensional analytical setup that has proven particularly useful for analysing multiple interactions across trophic levels. Here we...

  19. Table scraps: inter-trophic food provisioning by pumas.

    Science.gov (United States)

    Elbroch, L Mark; Wittmer, Heiko U

    2012-10-23

    Large carnivores perform keystone ecological functions through direct predation, or indirectly, through food subsidies to scavengers or trophic cascades driven by their influence on the distributions of their prey. Pumas (Puma concolor) are an elusive, cryptic species difficult to study and little is known about their inter-trophic-level interactions in natural communities. Using new GPS technology, we discovered that pumas in Patagonia provided 232 ± 31 kg of edible meat/month/100 km(2) to near-threatened Andean condors (Vultur gryphus) and other members of a diverse scavenger community. This is up to 3.1 times the contributions by wolves (Canis lupus) to communities in Yellowstone National Park, USA, and highlights the keystone role large, solitary felids play in natural systems. These findings are more pertinent than ever, for managers increasingly advocate controlling pumas and other large felids to bolster prey populations and mitigate concerns over human and livestock safety, without a full understanding of the potential ecological consequences of their actions.

  20. Spatial and temporal variance in fatty acid and stable isotope signatures across trophic levels in large river systems

    Science.gov (United States)

    Fritts, Andrea; Knights, Brent C.; Lafrancois, Toben D.; Bartsch, Lynn; Vallazza, Jon; Bartsch, Michelle; Richardson, William B.; Karns, Byron N.; Bailey, Sean; Kreiling, Rebecca

    2018-01-01

    Fatty acid and stable isotope signatures allow researchers to better understand food webs, food sources, and trophic relationships. Research in marine and lentic systems has indicated that the variance of these biomarkers can exhibit substantial differences across spatial and temporal scales, but this type of analysis has not been completed for large river systems. Our objectives were to evaluate variance structures for fatty acids and stable isotopes (i.e. δ13C and δ15N) of seston, threeridge mussels, hydropsychid caddisflies, gizzard shad, and bluegill across spatial scales (10s-100s km) in large rivers of the Upper Mississippi River Basin, USA that were sampled annually for two years, and to evaluate the implications of this variance on the design and interpretation of trophic studies. The highest variance for both isotopes was present at the largest spatial scale for all taxa (except seston δ15N) indicating that these isotopic signatures are responding to factors at a larger geographic level rather than being influenced by local-scale alterations. Conversely, the highest variance for fatty acids was present at the smallest spatial scale (i.e. among individuals) for all taxa except caddisflies, indicating that the physiological and metabolic processes that influence fatty acid profiles can differ substantially between individuals at a given site. Our results highlight the need to consider the spatial partitioning of variance during sample design and analysis, as some taxa may not be suitable to assess ecological questions at larger spatial scales.

  1. Toxicity evaluation of natural samples from the vicinity of rice fields using two trophic levels.

    Science.gov (United States)

    Marques, Catarina R; Pereira, Ruth; Gonçalves, Fernando

    2011-09-01

    An ecotoxicological screening of environmental samples collected in the vicinity of rice fields followed a combination of physical and chemical measurements and chronic bioassays with two freshwater trophic levels (microalgae: Pseudokirchneriella subcapitata and Chlorella vulgaris; daphnids: Daphnia longispina and Daphnia magna). As so, water and sediment/soil elutriate samples were obtained from three sites: (1) in a canal reach crossing a protected wetland upstream, (2) in a canal reach surrounded by rice fields and (3) in a rice paddy. The sampling was performed before and during the rice culture. During the rice cropping, the whole system quality decreased comparatively to the situation before that period (e.g. nutrient overload, the presence of pesticides in elutriates from sites L2 and L3). This was reinforced by a significant inhibition of both microalgae growth, especially under elutriates. Contrary, the life-history traits of daphnids were significantly stimulated with increasing concentrations of water and elutriates, for both sampling periods.

  2. Cesium accumulation by aquatic organisms at different trophic levels following an experimental release into a small reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Pinder, J.E., E-mail: jepinder@uga.ed [Savannah River Ecology Laboratory, P. O. Drawer E, Aiken, SC 29802 (United States); Hinton, T.G., E-mail: thomas.hinton@irsn.f [Savannah River Ecology Laboratory, P. O. Drawer E, Aiken, SC 29802 (United States); Taylor, B.E., E-mail: TaylorB@dnr.sc.go [Savannah River Ecology Laboratory, P. O. Drawer E, Aiken, SC 29802 (United States); Whicker, F.W., E-mail: ward.whicker@colostate.ed [Department of Environmental and Radiological Health Sciences, Colorado, State University, Fort Collins, CO 80523-1618 (United States)

    2011-03-15

    The rates of accumulation and subsequent loss of stable cesium ({sup 133}Cs) by organisms at different trophic levels within plankton-based and periphyton-based food chains were measured following the addition of {sup 133}Cs into a small reservoir near Aiken, South Carolina, USA. An uptake parameter u (L kg{sup -1} d{sup -1} dry mass) and a loss rate parameter k (d{sup -1}) were estimated for each organism using time-series measurements of {sup 133}Cs concentrations in water and biota, and these parameters were used to estimate maximum concentrations, times to maximum concentrations, and concentration ratios (C{sub r}). The maximum {sup 133}Cs concentrations for plankton, periphyton, the insect larva Chaoborus punctipennis, which feeds on plankton, and the snail Helisoma trivolvis, which feeds on periphyton, occurred within the first 14 days following the addition, whereas the maximum concentrations for the fish species Lepomis macrochirus and Micropterus salmoides occurred after 170 days. The C{sub r} based on dry mass for plankton and C. punctipennis were 1220 L kg{sup -1} and 5570 L kg{sup -1}, respectively, and were less than the C{sub r} of 8630 L kg{sup -1} for periphyton and 47,700 L kg{sup -1} for H. trivolvis. Although the C{sub r} differed between plankton-based and periphyton-based food chains, they displayed similar levels of biomagnification. Biomagnification was also indicated for fish where the C{sub r} for the mostly nonpiscivorous L. macrochirus of 22,600 L kg{sup -1} was three times less than that for mostly piscivorous M. salmoides of 71,500 L kg{sup -1}. Although the C{sub r} for M. salmoides was greater than those for periphyton and H. trivolvis, the maximum {sup 133}Cs concentrations for periphyton and H. trivolvis were greater than that for M. salmoides. - Research highlights: {yields} A simple uptake and loss model described the Cs dynamics in all the various biota. {yields} Concentrations of Cs were greater in periphyton than in plankton

  3. Long-term trends in the trophic structure of the orth Sea fish community : evidence from stable-isotope analysis, size-spectra and community metrics

    NARCIS (Netherlands)

    Jennings, S.; Greenstreet, S.P.R.; Hill, L.; Piet, G.J.; Pinnegar, J.K.; Warr, K.J.

    2002-01-01

    Fishing has wide-ranging impacts on marine ecosystems. One of the most pervasive signs of intensive fishing is "fishing down the food web", with landings increasingly dominated by smaller species from lower trophic levels. Decreases in the trophic level of landings are assumed to reflect those in

  4. Green Turtle Trophic Ecology

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — SWFSC is currently conducting a study of green sea turtle (Chelonia mydas) trophic ecology in the eastern Pacific. Tissue samples and stable carbon and stable...

  5. Trophic flexibility of the Atlantic blue crab Callinectes sapidus in invaded coastal systems of the Apulia region (SE Italy): A stable isotope analysis

    Science.gov (United States)

    Mancinelli, Giorgio; Teresa Guerra, Maria; Alujević, Karla; Raho, Davide; Zotti, Maurizio; Vizzini, Salvatrice

    2017-11-01

    The Atlantic blue crab Callinectes sapidus is recognized as an Invasive Alien Species in the Mediterranean Sea. However, its trophic role and feeding flexibility in invaded benthic food webs have been addressed only recently. Here, field samplings were conducted in winter and summer in five coastal systems of the Apulia region (SE Italy), three located on the Ionian Sea (Mar Piccolo, Torre Colimena, and Spunderati) and two on the Adriatic Sea (Acquatina and Alimini Grande). Captured blue crabs were weighed and had their δ13C and δ15N isotopic signatures measured; their trophic level (TL) was estimated using the mussel Mytilus galloprovincialis as isotopic baseline. C. sapidus abundances varied greatly across systems and seasons, and in Adriatic systems the species was not collected in winter. Trophic levels showed significant spatial and temporal variations, although with no general pattern. In winter, the Mar Piccolo population showed the highest TL values; the lowest estimates were in Torre Colimena and Spunderati, where crabs showed δ13C signatures significantly higher than mussels, suggesting the contribution of 13C-enriched plant material in the diet. In summer, with the exception of the Mar Piccolo, Ionian populations increased their trophic level; both Adriatic populations were characterized by the lowest TL estimates. The analysis performed at the individual scale further indicated body weight-related changes in trophic level. For the Torre Colimena population, in particular, a hump-shaped pattern was observed in both seasons. The present study highlighted a considerable spatial and temporal trophic flexibility of C. sapidus at the population scale, while at the individual scale size-related shifts in trophic level were observed. The ability of the blue crab to vary its energy sources in relation with season, local environmental conditions, and ontogenetic stage is emphasized, suggesting that it may represent a key determinant of its invasion success.

  6. Trophic transfer of trace metals from the polychaete worm Nereis diversicolor to the polychaete N. virens and the decapod crustacean Palaemonetes varians

    Science.gov (United States)

    Rainbow, P.S.; Poirier, L.; Smith, B.D.; Brix, K.V.; Luoma, S.N.

    2006-01-01

    Diet is an important exposure route for the uptake of trace metals by aquatic invertebrates, with trace metal trophic transfer depending on 2 stages - assimilation and subsequent accumulation by the predator. This study investigated the trophic transfer of trace metals from the sediment-dwelling polychaete worm Nereis diversicolor from metal-rich estuarine sediments in southwestern UK to 2 predators - another polychaete N. virens (Cu, Zn, Pb, Cd, Fe) and the decapod crustacean Palaemonetes varians (Cu, Zn, Pb, Cd, Fe, Ag, As, Mn). N. virens showed net accumulation of Cu, Zn, Pb and Cd from the prey; accumulation increased with increasing prey concentration, but a coefficient of trophic transfer decreased with increasing prey concentration, probably because a higher proportion of accumulated metal in the prey is bound in less trophically available (insoluble) detoxified forms. The trace metal accumulation patterns of P. varians apparently restricted significant net accumulation of metals from the diet of N. diversicolor to just Cd. There was significant mortality of the decapods fed on the diets of metal-rich worms. Metal-rich invertebrates that have accumulated metals from the rich historical store in the sediments of particular SW England estuaries can potentially pass these metals along food chains, with accumulation and total food chain transfer depending on the metal assimilation efficiencies and accumulation patterns of the animal at each trophic level. This trophic transfer may be significant enough to have ecotoxicological effects. ?? Inter-Research 2006.

  7. Trophic niche partitioning between two native and two exotic carnivores in SW Portugal

    Directory of Open Access Journals (Sweden)

    M. J. Santos

    2007-05-01

    Full Text Available The introduction of exotic species is one of the most pervasive consequences of the increased human mobility. The most known negative effects are the decrease or extinction of natives. The common-genet, Genetta genetta, and the Egyptian mongoose, Herpestes ichneumon, were introduced in the Iberian Peninsula in the 15th and 19th centuries, respectively. The competitive exclusion principle defines that two ecologically similar species cannot coexist. Thus, some degree of partitioning has to occur in species realized niche, which can occur at the trophic level. To test this hypothesis of partitioning we compared the diet of these two exotic species with that of two native species (stone marten, Martes foina, and red fox, Vulpes vulpes. The results show a high degree of overlap (>45% between the diets of species similar in their feeding strategies (arboreal and ground feeding. Nonetheless, at the finer scale of prey consumed at the species level some differences are found between the native and exotic species. These results suggest that if coexistence is due to trophic niche partitioning it only occurs at the level of the consumed species. However, coexistence may also be due to a combination of different strategies (home-range size, time and space use that structured the different realized niches of each species.

  8. Time- and depth-wise trophic niche shifts in Antarctic benthos.

    Science.gov (United States)

    Calizza, Edoardo; Careddu, Giulio; Sporta Caputi, Simona; Rossi, Loreto; Costantini, Maria Letizia

    2018-01-01

    Climate change is expected to affect resource-consumer interactions underlying stability in polar food webs. Polar benthic organisms have adapted to the marked seasonality characterising their habitats by concentrating foraging and reproductive activity in summer months, when inputs from sympagic and pelagic producers increase. While this enables the persistence of biodiverse food webs, the mechanisms underlying changes in resource use and nutrient transfer are poorly understood. Thus, our understanding of how temporal and spatial variations in the supply of resources may affect food web structure and functioning is limited. By means of C and N isotopic analyses of two key Antarctic benthic consumers (Adamussium colbecki, Bivalvia, and Sterechinus neumayeri, Echinoidea) and Bayesian mixing models, we describe changes in trophic niche and nutrient transfer across trophic levels associated with the long- and short-term diet and body size of specimens sampled in midsummer in both shallow and deep waters. Samplings occurred soon after the sea-ice broke up at Tethys Bay, an area characterised by extreme seasonality in sea-ice coverage and productivity in the Ross Sea. In the long term, the trophic niche was broader and variation between specimens was greater, with intermediate-size specimens generally consuming a higher number of resources than small and large specimens. The coupling of energy channels in the food web was consequently more direct than in the short term. Sediment and benthic algae were more frequently consumed in the long term, before the sea-ice broke up, while consumers specialised on sympagic algae and plankton in the short term. Regardless of the time scale, sympagic algae were more frequently consumed in shallow waters, while plankton was more frequently consumed in deep waters. Our results suggest a strong temporal relationship between resource availability and the trophic niche of benthic consumers in Antarctica. Potential climate-driven changes

  9. Critical assessment and ramifications of a purported marine trophic cascade

    Science.gov (United States)

    Grubbs, R. Dean; Carlson, John K; Romine, Jason G.; Curtis, Tobey H; McElroy, W. David; McCandless, Camilla T; Cotton, Charles F; Musick, John A.

    2016-01-01

    When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions.

  10. Concentrations and trophic magnification of cyclic siloxanes in aquatic biota from the Western Basin of Lake Erie, Canada

    International Nuclear Information System (INIS)

    McGoldrick, Daryl J.; Chan, Cecilia; Drouillard, Ken G.; Keir, Michael J.; Clark, Mandi G.; Backus, Sean M.

    2014-01-01

    We examine the concentrations and food web biomagnification of three cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) using aquatic biota collected from Lake Erie. Concentrations of cVMS in biota were within the range reported for other studies of cVMS in aquatic biota. Trophic magnification factors (TMF) were assessed in various food web configurations to investigate the effects of food web structure. TMF estimates were highly dependent on the inclusion/exclusion of the organisms occupying the highest and lowest trophic levels and were >1 for D4 and D5, indicating biomagnification, in only 1 of the 5 food web configurations investigated and were <1 in the remaining 4 food web configurations. TMF estimates for PCB180 were also dependant on food web configuration, but did not correspond with those obtained for cVMS materials. These differences may be attributed to environmental exposure and/or lipid partitioning differences between PCB180 and cVMS. -- Highlights: • We investigated trophic magnification of siloxanes in aquatic biota from Lake Erie. • Trophic magnification estimates were variable and sensitive to food web structure. • Lipid partitioning of siloxanes and PCBs differ and may contribute to variability. -- Biomagnification estimates for siloxanes in Lake Erie are sensitive to food web structure, contaminant exposure pathways, and lipid partitioning differences between PCBs and siloxanes

  11. Almost there: transmission routes of bacterial symbionts between trophic levels.

    Directory of Open Access Journals (Sweden)

    Elad Chiel

    transmission of symbionts across trophic levels. The possible mechanisms that lead to the differences in transmission of species of symbionts among species of hosts are discussed.

  12. Effect of tidal environment on the trophic balance of mixotrophic hexacorals using biochemical profile and photochemical performance as indicators.

    Science.gov (United States)

    Rosa, Inês C; Rocha, Rui J M; Cruz, Igor; Lopes, Ana; Menezes, Natália; Bandarra, Narcisa; Kikuchi, Ruy; Serôdio, João; Soares, Amadeu M V M; Rosa, Rui

    2018-04-01

    Fluctuations of environmental factors in intertidal habitats can disrupt the trophic balance of mixotrophic cnidarians. We investigated the effect of tidal environments (subtidal, tidal pools and emerged areas) on fatty acid (FA) content of Zoanthus sociatus and Siderastrea stellata. Effect on photophysiology was also accessed as an autotrophy proxy. There was a general tendency of a lower percentage of zooplankton-associated FAs in colonies from emerged areas or tidal pools when compared with colonies from the subtidal environment. Moreover, tidal environment significantly affected the photophysiology of both species. Colonies from the subtidal generally showed lower values of α, ETR max and E k when compared with their conspecifics from tidal pools or emerged areas. However, the absence of consistent patterns in F v /F m and in dinoflagellate-associated FAs, suggest that these corals are well adapted to intertidal conditions. This suggests that intertidal pressures may disturb the trophic balance, mainly by affecting heterotrophy of these species. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. Nutrients distribution and trophic status assessment in the northern Beibu Gulf, China

    Science.gov (United States)

    Lai, Junxiang; Jiang, Fajun; Ke, Ke; Xu, Mingben; Lei, Fu; Chen, Bo

    2014-09-01

    Using historical and 2010 field data, the distribution of nutrients in the northern Beibu Gulf of China is described. There was a decreasing trend in the concentration of nutrients from the north coast to offshore waters of the northern Beibu Gulf, reflecting the influence of inputs from land-based sources. High concentrations of dissolved inorganic nitrogen (DIN) and phosphate (PO4-P) occurred mainly at Fangchenggang Bay, Qinzhou Bay, and Lianzhou Bay. Four different methods were used to assess eutrophication. The trophic status of the Beibu Gulf was characterized using the single factor, Eutrophication index (EI), Trophic index (TRIX) and Assessment of Estuarine Trophic Status (ASSETS) methods. Based on nutrient concentrations, 73.9% of DIN and 26.7% of PO4-P samples exceeded the fourth grade Seawater Quality Standard of China. Eutrophication index values varied widely, but higher levels of eutrophication were generally found in bays and estuaries. TRIX values ranged from 2.61 to 7.27, with an average of 4.98, indicating a mesotrophic and moderately productive system. A positive correlation between TRIX and harmful algal species richness and abundance was observed. The ASSETS model evaluates eutrophication status based on a Pressure-State-Response approach, including three main indices: influencing factors, overall eutrophic condition, and future outlook. The Beibu Gulf was graded as moderate using ASSETS. The single factor and Chinese nutrient index methods were considered inadequate for the assessment of trophic status. TRIX can be used as an indicator of trophic state and ASSETS showed good potential to assess eutrophication. The results of TRIX and ASSETS depend on threshold values. To establish these values, further research is required within the northern Beibu Gulf.

  14. Ecosystem structure and trophic analysis of Angolan fishery landings

    Directory of Open Access Journals (Sweden)

    Ronaldo Angelini

    2011-06-01

    Full Text Available Information on the mean trophic level of fishery landings in Angola and the output from a preliminary Ecopath with Ecosim (EwE model were used to examine the dynamics of the Angolan marine ecosystem. Results were compared with the nearby Namibian and South African ecosystems, which share some of the exploited fish populations. The results show that: (i The mean trophic level of Angola’s fish landings has not decreased over the years; (ii There are significant correlations between the landings of Angola, Namibia and South Africa; (iii The ecosystem attributes calculated by the EwE models for the three ecosystems were similar, and the main differences were related to the magnitude of flows and biomass; (iv The similarity among ecosystem trends for Namibia, South Africa and Angola re-emphasizes the need to continue collaborative regional studies on the fish stocks and their ecosystems. To improve the Angolan model it is necessary to gain a better understanding of plankton dynamics because plankton are essential for Sardinella spp. An expanded analysis of the gut contents of the fish species occupying Angola’s coastline is also necessary.

  15. Trophic availability buffers the detrimental effects of clogging in an alpine stream.

    Science.gov (United States)

    Doretto, Alberto; Bona, Francesca; Piano, Elena; Zanin, Ilaria; Eandi, Anna Chiara; Fenoglio, Stefano

    2017-08-15

    Clogging, the streambed colmation by fine sediments, is an important widespread source of impact affecting freshwaters. Alterations in stream morphology and hydrology, added to the effects of global climate change, are responsible for this phenomenon, that is particularly pernicious in mountainous lotic systems naturally characterized by coarse substrates. Among the studies investigating this issue some were descriptive, while others used artificial substrates to compare ongoing fine sediment accumulation and macroinvertebrate assemblage recruitment. Other studies used from the outset artificial substrates arranged with different levels of clogging. Our study fits into this line, but adding an innovative element simulating different availability of coarse particulate organic matter, i.e. the main trophic input in low-order, mountainous stream. To investigate how clogging and CPOM can influence macroinvertebrate communities, we placed 135 artificial substrates in the upper Po river (NW Italy). We set up a three way factorial design with three different levels of sedimentation and terrestrial leaf material. Artificial substrates were removed on three different dates. Benthic invertebrates were identified and classified according to their bio-ecological traits. We also measured macroinvertebrate dry mass and CPOM degradation in the different trap types. Our findings show that clogging acts as a selective filter influencing taxa richness, density, functional composition and biomass of benthic assemblage. Moreover, fine sediments affect the energetic dynamics in the river ecosystem, decreasing the mass loss rate of terrestrial leaves. Interestingly, our results clearly demonstrate that high availability of CPOM can buffer the negative effect of clogging, suggesting that an adequate input of allochthonous organic matter may lessen the impact of fine sediment deposition. Because land use transformation and removal of wooded riparian areas increase clogging and

  16. Diet and trophic structure of the fish fauna in a subtropical ecosystem: impoundment effects

    Directory of Open Access Journals (Sweden)

    Rosilene Luciana Delariva

    Full Text Available This study examined the diet and trophic structure of the fish fauna, over temporal and spatial scales, as affected by the impoundment of the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Sampling was conducted before (March 1997 - February 1998 and after the impoundment (March 1999 - February 2000, at four sampling sites. The stomach contents were analyzed by the volumetric method. The species could be organized in 10 trophic guilds: algivores, carcinophages, detritivores, herbivores, aquatic insectivores, terrestrial insectivores, invertivores, omnivores, piscivores, and planktivores; the first and last guilds were represented only in the post-impoundment period. Similarity patterns and feeding changes were summarized by a non-metric Multi-dimensional Scaling (nMDS analysis and statistically tested by a Permutational multivariate analysis of variance (PERMANOVA. Most species showed feeding changes, except for the piscivores and detritivores. These changes were related to the temporal factor (impoundment phases, such as reduced intake of benthic organisms and allochthonous food, which were usually replaced by resources from the reservoir itself (algae, microcrustaceans, and fish, simplifying the food spectrum of the fish fauna. A different indicator of food resources (IndVal corroborated these changes in the feeding of the species. The proportions of the trophic guilds evaluated based on the catch per unit of effort (CPUE and tested by ANOSIM were significantly different before and after the impoundment. Herbivores and piscivores were the guilds that contributed (SIMPER to these differences, especially the high increase in biomass of the piscivore guild after the impoundment. Variations in the abundance of trophic guilds were more directly related to changes in the feeding habits of the fish fauna than to increases in the number and biomass of the species that constitute these guilds.

  17. Strontium-90 and cesium-137 migration in trophic chain of cattle

    International Nuclear Information System (INIS)

    Zotov, V.G.; Sirotkin, A.N.; Isamov, N.N.

    1983-01-01

    Technique for determination of factors of radionuclide migration in cattle trophic chain, which can be used for forecasting probable contamination of food and cattle breeding products Under Uzbekistan conditions is suggested. It is shown that the factor of biological absorption (FBA) of strontiUm 90 by plants from grey desert soils is 3.7 times higher, than of cesium 137. Mentioned differences in soil-plants migration link are leveled and their FBA in food-milk, food-bone, food-mUscles links remain practically the same during radionuclide migration from food to milk and meat. During radionuclide migration in trophic chain of cattle in food-bone and food-muscles chains the concentration of strontium 90 in bone tissUe and cesium 137 in muscle tissue takes place

  18. Mercury biomagnification and the trophic structure of the ichthyofauna from a remote lake in the Brazilian Amazon

    Energy Technology Data Exchange (ETDEWEB)

    Azevedo-Silva, Claudio Eduardo, E-mail: ceass@biof.ufrj.br [Laboratório de Radioisótopos Eduardo Penna, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Cidade Universitária, Av. Carlos Chagas Filho s/n, bloco G, Sala 60, Subsolo, Ilha do Fundão, Rio de Janeiro, RJ (Brazil); Almeida, Ronaldo [Instituto Natureza e Cultura, Universidade Federal do Amazonas, Rua 1 de Maio. Colegiado de Ciências Agrárias, Benjamin Constant, Colônia, AM (Brazil); Carvalho, Dario P. [Laboratório de Radioisótopos Eduardo Penna, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Cidade Universitária, Av. Carlos Chagas Filho s/n, bloco G, Sala 60, Subsolo, Ilha do Fundão, Rio de Janeiro, RJ (Brazil); Ometto, Jean P.H.B. [Instituto Nacional de Pesquisas Espaciais, Centro de Ciências do Sistema Terrestre, Avenida dos Astronautas, 1758, Jardim da Granja, São José dos Campos, SP (Brazil); Camargo, Plínio B. de [Laboratório de Ecologia Isotópica, Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Avenida Centenário, 303, São Dimas, Piracicaba, SP (Brazil); and others

    2016-11-15

    The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ{sup 13}C) and nitrogen (δ{sup 15}N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in the calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ{sup 13}C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapó (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ{sup 13}C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively

  19. Mercury biomagnification and the trophic structure of the ichthyofauna from a remote lake in the Brazilian Amazon

    International Nuclear Information System (INIS)

    Azevedo-Silva, Claudio Eduardo; Almeida, Ronaldo; Carvalho, Dario P.; Ometto, Jean P.H.B.; Camargo, Plínio B. de

    2016-01-01

    The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in the calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ 13 C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapó (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ 13 C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively. These findings

  20. Isotopic niche variation in a higher trophic level ectotherm: highlighting the role of succulent plants in desert food webs.

    Directory of Open Access Journals (Sweden)

    Miguel Delibes

    Full Text Available Stable isotope analysis of animal tissues allows description of isotopic niches, whose axes in an n-dimensional space are the isotopic ratios, compared to a standard, of different isotope systems (e.g. δ(13C, δ(15N. Isotopic niches are informative about where an animal, population or species lives and about what it consumes. Here we describe inter- and intrapopulation isotopic niche (bidimensional δ(13C-δ(15N space of the Orange-throated whiptail (Aspidoscelis hyperythra, an arthropodivorous small lizard, in ten localities of Baja California Sur (Mexico. These localities range from extreme arid to subtropical conditions. Between 13 and 20 individuals were sampled at each locality and 1 cm of tail-tip was collected for isotope analysis. As expected, interpopulation niche width variation was much larger than intrapopulation one. Besides, isotopic variation was not related to age, sex or individual size of lizards. This suggests geographic variation of the isotopic niche was related to changes in the basal resources that fuel the trophic web at each locality. The position of Bayesian isotope ellipses in the δ-space indicated that whiptails in more arid localities were enriched in 13C, suggesting most of the carbon they ingested came from CAM succulent plants (cacti, agaves and in minor degree in C4 grasses. Contrarily, whiptails in subtropical areas were depleted in 13C, as they received more carbon from C3 scrubs and trees. Localities closer to sea-level tended to be enriched in 15N, but a clear influence of marine subsidies was detected only at individual level. The study contributes to identify the origin and pathways through which energy flows across the trophic webs of North American deserts.

  1. Isotopic Niche Variation in a Higher Trophic Level Ectotherm: Highlighting the Role of Succulent Plants in Desert Food Webs

    Science.gov (United States)

    Delibes, Miguel; Blazquez, Ma Carmen; Fedriani, Jose Maria; Granados, Arsenio; Soriano, Laura; Delgado, Antonio

    2015-01-01

    Stable isotope analysis of animal tissues allows description of isotopic niches, whose axes in an n-dimensional space are the isotopic ratios, compared to a standard, of different isotope systems (e.g. δ13C, δ15N). Isotopic niches are informative about where an animal, population or species lives and about what it consumes. Here we describe inter- and intrapopulation isotopic niche (bidimensional δ13C-δ15N space) of the Orange-throated whiptail (Aspidoscelis hyperythra), an arthropodivorous small lizard, in ten localities of Baja California Sur (Mexico). These localities range from extreme arid to subtropical conditions. Between 13 and 20 individuals were sampled at each locality and 1 cm of tail-tip was collected for isotope analysis. As expected, interpopulation niche width variation was much larger than intrapopulation one. Besides, isotopic variation was not related to age, sex or individual size of lizards. This suggests geographic variation of the isotopic niche was related to changes in the basal resources that fuel the trophic web at each locality. The position of Bayesian isotope ellipses in the δ-space indicated that whiptails in more arid localities were enriched in 13C, suggesting most of the carbon they ingested came from CAM succulent plants (cacti, agaves) and in minor degree in C4 grasses. Contrarily, whiptails in subtropical areas were depleted in 13C, as they received more carbon from C3 scrubs and trees. Localities closer to sea-level tended to be enriched in 15N, but a clear influence of marine subsidies was detected only at individual level. The study contributes to identify the origin and pathways through which energy flows across the trophic webs of North American deserts. PMID:25973609

  2. Trophic compensation reinforces resistance: herbivory absorbs the increasing effects of multiple disturbances.

    Science.gov (United States)

    Ghedini, Giulia; Russell, Bayden D; Connell, Sean D

    2015-02-01

    Disturbance often results in small changes in community structure, but the probability of transitioning to contrasting states increases when multiple disturbances combine. Nevertheless, we have limited insights into the mechanisms that stabilise communities, particularly how perturbations can be absorbed without restructuring (i.e. resistance). Here, we expand the concept of compensatory dynamics to include countervailing mechanisms that absorb disturbances through trophic interactions. By definition, 'compensation' occurs if a specific disturbance stimulates a proportional countervailing response that eliminates its otherwise unchecked effect. We show that the compounding effects of disturbances from local to global scales (i.e. local canopy-loss, eutrophication, ocean acidification) increasingly promote the expansion of weedy species, but that this response is countered by a proportional increase in grazing. Finally, we explore the relatively unrecognised role of compensatory effects, which are likely to maintain the resistance of communities to disturbance more deeply than current thinking allows. © 2015 John Wiley & Sons Ltd/CNRS.

  3. Characteristics of trophic transfer of polychlorinated biphenyls in marine organisms in Incheon North Harbor, Korea.

    Science.gov (United States)

    Kim, Seung Kyu; Lee, Dong Soo; Oh, Jae Ryong

    2002-04-01

    The trophic transfer of polychlorinated biphenyls (PCBs) was characterized for zooplankton (primarily Paracalanus spp. and Acartia spp.), pacific oyster (Crassostrea gigas), shore crab (Hemigrapsus penicillatus), and goby (Acanthogobius hasta) in the aquatic system of Incheon North Harbor, Korea. The congener pattern in the species was clearly divided by the main PCB uptake route. Compared with zooplankton and oyster, the fraction of heavier homologues increased in crab and goby that take PCBs from food. Linear relationships were observed between log (fugacity in lipid/fugacity in seawater) and log Kow for all the species. For zooplankton and oyster, such an observation should not be regarded as a true absence of superhydrophobicity, because establishment of equilibrium with seawater was not evident. For crab and goby, the absence of superhydrophobicity was evidenced by the trophic transfer factor that continuously increased with Kow up to 10(7.8). These results suggest that superhydrophobicity might be species specific. The trophic transfer factors and the fugacity levels in the lipid phase indicated that bioaccumulation in crab and goby advanced beyond the level in equilibrium with seawater in the harbor basin.

  4. Trophic transfer of persistent organochlorine contaminants (OCs) within an Arctic marine food web from the southern Beaufort-Chukchi Seas

    International Nuclear Information System (INIS)

    Hoekstra, P.F.; O'Hara, T.M.; Fisk, A.T.; Borgaa, K.; Solomon, K.R.; Muir, D.C.G.

    2003-01-01

    The trophic status and biomagnification of persistent OCs within the near-shore Beaufort-Chukchi Seas food web from Barrow, AK is discussed. - Stable isotope values (δ 13 C, δ 15 N) and concentrations of persistent organochlorine contaminants (OCs) were determined to evaluate the near-shore marine trophic status of biota and biomagnification of OCs from the southern Beaufort-Chukchi Seas (1999-2000) near Barrow, AK. The biota examined included zooplankton (Calanus spp.), fish species such as arctic cod (Boreogadus saida), arctic char (Salvelinus alpinus), pink salmon (Oncorhynchus gorbuscha), and fourhorn sculpin (Myoxocephalus quadricornis), along with marine mammals, including bowhead whales (Balaena mysticetus), beluga whales (Delphinapterus leucas), ringed seals (Phoca hispida) and bearded seals (Erignathus barbatus). The isotopically derived trophic position of biota from the Beaufort-Chukchi Seas marine food web, avian fauna excluded, is similar to other coastal food webs in the Arctic. Concentrations of OCs in marine mammals were significantly greater than in fish and corresponded with determined trophic level. In general, OCs with the greatest food web magnification factors (FWMFs) were those either formed due to biotransformation (e.g. p,p'-DDE, oxychlordane) or considered recalcitrant (e.g. β-HCH, 2,4,5-Cl substituted PCBs) in most biota, whereas concentrations of OCs that are considered to be readily eliminated (e.g. γ-HCH) did not correlate with trophic level. Differences in physical-chemical properties of OCs, feeding strategy and possible biotransformation were reflected in the variable biomagnification between fish and marine mammals. The FWMFs in the Beaufort-Chukchi Seas region were consistent with reported values in the Canadian Arctic and temperate food webs, but were statistically different than FWMFs from the Barents and White Seas, indicating that the spatial variability of OC contamination in top-level marine Arctic predators is

  5. Trophic transfer of soil arsenate and associated toxic effects in a plant-aphid-parasitoid system

    Science.gov (United States)

    Lee, Y. S.; Wee, J.; Lee, M.; Hong, J.; Cho, K.

    2017-12-01

    Terrestrial toxic effects of soil arsenic were studied using a model system consisting of soil which artificially treated with arsenic, Capsicum annum,Myzus persicae and Aphidus colemani. We investigated the transfer of arsenic in a soil-plant-aphid system and toxic effect of elevated arsenic through a plant-aphid-parasitoid system. To remove the effect of poor plant growth on aphid performance, test concentrations which have a no effect on health plant growth were selected. Arsenic concentration of growth medium, plant tissues (root, stem, leaf) aphids were measured to observe the arsenic transfer. Correlation matrix was made with arsenic in growth medium which extracted with three extractants (aquaregia, 0.01 M CaCl2 and deionized water), arsenic in plant tissues and plant performance. Toxic effects of elevated arsenic concentrations on each species were investigated at population level. Studied plant performances were dry weight of each tissue, elongation of roots and stems, area of leaves, chlorophyll content of leaves, protein content of leaves and sugar content of leaves. Mean development time, fecundity and honeydew excretion of the aphids and host choice capacity and parasitism success of the parasitoids were examined. In addition, enzyme activities of the plants and the aphids against reactive oxygen species (ROS) induced by arsenic stress were also investigated. The results suggest that arsenic concentration in plant tissues and aphids were elevated with increased concentration of arsenic in soil. Decreased fecundity and honeydew excretion of aphids were observed and decreased eclosion rate of parasitoids were observed with increased arsenic treatment in growth medium. The results showed low concentration of arsenic in soil can transfer through food chain and can impact on higher trophic level species.

  6. Trophic ulcers in the carpal tunnel syndrome

    Directory of Open Access Journals (Sweden)

    Abelardo Q.-C. Araújo

    1993-09-01

    Full Text Available A patient with carpal tunnel syndrome (CTS and trophic ulcers is described. Despite the healing of the ulcers after surgery for CTS, the severe sensory deficit and the electrophysiological tests have not shown any significant improvement. We think these findings argue against the hypothesis of the sensory deficit being responsible for the trophic ulcers. We favor a major role for the sympathetic disturbances as the main cause for those lesions.

  7. Intersexual Trophic Niche Partitioning in an Ant-Eating spider (Araneae: Zodariidae)

    DEFF Research Database (Denmark)

    Pekár, Stanislav; Martisová, Martina; Bilde, T.

    2011-01-01

    lead to higher energy demands in females driven by fecundity selection, while males invest in mate searching. We tested predictions of the two hypotheses underlying intersexual trophic niche partitioning in a natural population of spiders. Zodarion jozefienae spiders specialize on Messor barbarus ants...... that are polymorphic in body size and hence comprise potential trophic niches for the spider, making this system well-suited to study intersexual trophic niche partitioning. Methodology/Principal Findings Comparative analysis of trophic morphology (the chelicerae) and body size of males, females and juveniles...... demonstrated highly female biased SSD (Sexual Size Dimorphism) in body size, body weight, and in the size of chelicerae, the latter arising from sex-specific growth patterns in trophic morphology. In the field, female spiders actively selected ant sub-castes that were larger than the average prey size...

  8. Looplessness in networks is linked to trophic coherence.

    Science.gov (United States)

    Johnson, Samuel; Jones, Nick S

    2017-05-30

    Many natural, complex systems are remarkably stable thanks to an absence of feedback acting on their elements. When described as networks these exhibit few or no cycles, and associated matrices have small leading eigenvalues. It has been suggested that this architecture can confer advantages to the system as a whole, such as "qualitative stability," but this observation does not in itself explain how a loopless structure might arise. We show here that the number of feedback loops in a network, as well as the eigenvalues of associated matrices, is determined by a structural property called trophic coherence, a measure of how neatly nodes fall into distinct levels. Our theory correctly classifies a variety of networks-including those derived from genes, metabolites, species, neurons, words, computers, and trading nations-into two distinct regimes of high and low feedback and provides a null model to gauge the significance of related magnitudes. Because trophic coherence suppresses feedback, whereas an absence of feedback alone does not lead to coherence, our work suggests that the reasons for "looplessness" in nature should be sought in coherence-inducing mechanisms.

  9. Intersexual trophic niche partitioning in an ant-eating spider (Araneae: Zodariidae.

    Directory of Open Access Journals (Sweden)

    Stano Pekár

    2011-01-01

    Full Text Available Divergence in trophic niche between the sexes may function to reduce competition between the sexes ("intersexual niche partitioning hypothesis", or may be result from differential selection among the sexes on maximizing reproductive output ("sexual selection hypothesis". The latter may lead to higher energy demands in females driven by fecundity selection, while males invest in mate searching. We tested predictions of the two hypotheses underlying intersexual trophic niche partitioning in a natural population of spiders. Zodarion jozefienae spiders specialize on Messor barbarus ants that are polymorphic in body size and hence comprise potential trophic niches for the spider, making this system well-suited to study intersexual trophic niche partitioning.Comparative analysis of trophic morphology (the chelicerae and body size of males, females and juveniles demonstrated highly female biased SSD (Sexual Size Dimorphism in body size, body weight, and in the size of chelicerae, the latter arising from sex-specific growth patterns in trophic morphology. In the field, female spiders actively selected ant sub-castes that were larger than the average prey size, and larger than ants captured by juveniles and males. Female fecundity was highly positively correlated with female body mass, which reflects foraging success during the adult stage. Females in laboratory experiments preferred the large ant sub-castes and displayed higher capture efficiency. In contrast, males occupied a different trophic niche and showed reduced foraging effort and reduced prey capture and feeding efficiency compared with females and juveniles.Our data indicate that female-biased dimorphism in trophic morphology and body size correlate with sex-specific reproductive strategies. We propose that intersexual trophic niche partitioning is shaped primarily by fecundity selection in females, and results from sex-differences in the route to successful reproduction where females are

  10. Catchment land-use effects on littoral macroinvertebrates in response to local habitat structure and trophic state

    DEFF Research Database (Denmark)

    McGoff, Elaine; Sandin, Leif Leonard

    2012-01-01

    macroinvertebrate community structure: trophic status, substrate variables or riparian variables. We also investigated what influence each of these groups of variables has on the other. The impact of large scale land use patterns was also investigated, to determine if macroinvertebrates responded differently in two...... different catchment land use types: impaired and unimpaired. Partial canonical ordination analysis showed that substrate variables were the most important for describing macroinvertebrate community variation in both catchment land use classes, followed by riparian descriptors, with the trophic signal only...

  11. Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health.

    Science.gov (United States)

    Carbery, Maddison; O'Connor, Wayne; Palanisami, Thavamani

    2018-06-01

    Plastic litter has become one of the most serious threats to the marine environment. Over 690 marine species have been impacted by plastic debris with small plastic particles being observed in the digestive tract of organisms from different trophic levels. The physical and chemical properties of microplastics facilitate the sorption of contaminants to the particle surface, serving as a vector of contaminants to organisms following ingestion. Bioaccumulation factors for higher trophic organisms and impacts on wider marine food webs remain unknown. The main objectives of this review were to discuss the factors influencing microplastic ingestion; describe the biological impacts of associated chemical contaminants; highlight evidence for the trophic transfer of microplastics and contaminants within marine food webs and outline the future research priorities to address potential human health concerns. Controlled laboratory studies looking at the effects of microplastics and contaminants on model organisms employ nominal concentrations and consequently have little relevance to the real environment. Few studies have attempted to track the fate of microplastics and mixed contaminants through a complex marine food web using environmentally relevant concentrations to identify the real level of risk. To our knowledge, there has been no attempt to understand the transfer of microplastics and associated contaminants from seafood to humans and the implications for human health. Research is needed to determine bioaccumulation factors for popular seafood items in order to identify the potential impacts on human health. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Climate Change and Baleen Whale Trophic Cascades in Greenland

    Science.gov (United States)

    2009-09-30

    DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. Climate Change and Baleen Whale Trophic Cascades in Greenland...SUBTITLE Climate Change And Baleen Whale Trophic Cascades In Greenland 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  13. Time- and depth-wise trophic niche shifts in Antarctic benthos.

    Directory of Open Access Journals (Sweden)

    Edoardo Calizza

    Full Text Available Climate change is expected to affect resource-consumer interactions underlying stability in polar food webs. Polar benthic organisms have adapted to the marked seasonality characterising their habitats by concentrating foraging and reproductive activity in summer months, when inputs from sympagic and pelagic producers increase. While this enables the persistence of biodiverse food webs, the mechanisms underlying changes in resource use and nutrient transfer are poorly understood. Thus, our understanding of how temporal and spatial variations in the supply of resources may affect food web structure and functioning is limited. By means of C and N isotopic analyses of two key Antarctic benthic consumers (Adamussium colbecki, Bivalvia, and Sterechinus neumayeri, Echinoidea and Bayesian mixing models, we describe changes in trophic niche and nutrient transfer across trophic levels associated with the long- and short-term diet and body size of specimens sampled in midsummer in both shallow and deep waters. Samplings occurred soon after the sea-ice broke up at Tethys Bay, an area characterised by extreme seasonality in sea-ice coverage and productivity in the Ross Sea. In the long term, the trophic niche was broader and variation between specimens was greater, with intermediate-size specimens generally consuming a higher number of resources than small and large specimens. The coupling of energy channels in the food web was consequently more direct than in the short term. Sediment and benthic algae were more frequently consumed in the long term, before the sea-ice broke up, while consumers specialised on sympagic algae and plankton in the short term. Regardless of the time scale, sympagic algae were more frequently consumed in shallow waters, while plankton was more frequently consumed in deep waters. Our results suggest a strong temporal relationship between resource availability and the trophic niche of benthic consumers in Antarctica. Potential

  14. Not all jellyfish are equal: isotopic evidence for inter- and intraspecific variation in jellyfish trophic ecology

    Directory of Open Access Journals (Sweden)

    Nicholas E.C. Fleming

    2015-07-01

    Full Text Available Jellyfish are highly topical within studies of pelagic food-webs and there is a growing realisation that their role is more complex than once thought. Efforts being made to include jellyfish within fisheries and ecosystem models are an important step forward, but our present understanding of their underlying trophic ecology can lead to their oversimplification in these models. Gelatinous zooplankton represent a polyphyletic assemblage spanning >2,000 species that inhabit coastal seas to the deep-ocean and employ a wide variety of foraging strategies. Despite this diversity, many contemporary modelling approaches include jellyfish as a single functional group feeding at one or two trophic levels at most. Recent reviews have drawn attention to this issue and highlighted the need for improved communication between biologists and theoreticians if this problem is to be overcome. We used stable isotopes to investigate the trophic ecology of three co-occurring scyphozoan jellyfish species (Aurelia aurita, Cyanea lamarckii and C. capillata within a temperate, coastal food-web in the NE Atlantic. Using information on individual size, time of year and δ13C and δ15N stable isotope values, we examined: (1 whether all jellyfish could be considered as a single functional group, or showed distinct inter-specific differences in trophic ecology; (2 Were size-based shifts in trophic position, found previously in A. aurita, a common trait across species?; (3 When considered collectively, did the trophic position of three sympatric species remain constant over time? Differences in δ15N (trophic position were evident between all three species, with size-based and temporal shifts in δ15N apparent in A. aurita and C. capillata. The isotopic niche width for all species combined increased throughout the season, reflecting temporal shifts in trophic position and seasonal succession in these gelatinous species. Taken together, these findings support previous

  15. Not all jellyfish are equal: isotopic evidence for inter- and intraspecific variation in jellyfish trophic ecology.

    Science.gov (United States)

    Fleming, Nicholas E C; Harrod, Chris; Newton, Jason; Houghton, Jonathan D R

    2015-01-01

    Jellyfish are highly topical within studies of pelagic food-webs and there is a growing realisation that their role is more complex than once thought. Efforts being made to include jellyfish within fisheries and ecosystem models are an important step forward, but our present understanding of their underlying trophic ecology can lead to their oversimplification in these models. Gelatinous zooplankton represent a polyphyletic assemblage spanning >2,000 species that inhabit coastal seas to the deep-ocean and employ a wide variety of foraging strategies. Despite this diversity, many contemporary modelling approaches include jellyfish as a single functional group feeding at one or two trophic levels at most. Recent reviews have drawn attention to this issue and highlighted the need for improved communication between biologists and theoreticians if this problem is to be overcome. We used stable isotopes to investigate the trophic ecology of three co-occurring scyphozoan jellyfish species (Aurelia aurita, Cyanea lamarckii and C. capillata) within a temperate, coastal food-web in the NE Atlantic. Using information on individual size, time of year and δ (13)C and δ (15)N stable isotope values, we examined: (1) whether all jellyfish could be considered as a single functional group, or showed distinct inter-specific differences in trophic ecology; (2) Were size-based shifts in trophic position, found previously in A. aurita, a common trait across species?; (3) When considered collectively, did the trophic position of three sympatric species remain constant over time? Differences in δ (15)N (trophic position) were evident between all three species, with size-based and temporal shifts in δ (15)N apparent in A. aurita and C. capillata. The isotopic niche width for all species combined increased throughout the season, reflecting temporal shifts in trophic position and seasonal succession in these gelatinous species. Taken together, these findings support previous assertions

  16. Bimodality in stable isotope composition facilitates the tracing of carbon transfer from macrophytes to higher trophic levels

    NARCIS (Netherlands)

    Mendonca, R.; Kosten, S.; Lacerot, G.; Mazzeo, N.; Roland, F.; Ometto, J.P.; Paz, A.; Bueno, O.C.; Gomes, A.C.M.M.; Scheffer, M.

    2013-01-01

    Even though the suitability of macrophytes to act as a carbon source to food webs has been questioned by some studies, some others indicate that macrophyte-derived carbon may play an important role in the trophic transfer of organic matter in the food web of shallow lakes. To evaluate the importance

  17. Diet and trophic ecology of the tiger shark (Galeocerdo cuvier from South African waters.

    Directory of Open Access Journals (Sweden)

    Matthew L Dicken

    Full Text Available Knowledge of the diet and trophic ecology of apex predators is key for the implementation of effective ecosystem as well as species-based management initiatives. Using a combination of stomach content data and stable isotope analysis (δ15N and δ13C the current study provides information on size-based and sex-specific variations in diet, trophic position (TP and foraging habitat of tiger sharks (Galeocerdo cuvier caught in the KwaZulu-Natal Sharks Board bather protection program. This study presents the longest time-series and most detailed analysis of stomach content data for G. cuvier worldwide. Prey identified from 628 non-empty stomachs revealed a size-based shift in diet. Reptiles, birds, mysticetes, and large shark species increased in dietary importance with G. cuvier size, concomitant with a decrease in smaller prey such as batoids and teleosts. Seasonal and decadal shifts in diet driven primarily by changes in the importance of elasmobranchs and mammal (cetacean prey were recorded for medium sized (150-220 cm G. cuvier. Both stomach content and stable isotope analysis indicated that G. cuvier is a generalist feeder at the population level. Size-based δ13C profiles indicated a movement to offshore foraging habitats by larger G. cuvier. Calculated TP varied by method ranging from 4.0 to 5.0 (TPSCA for stomach contents and from 3.6 to 4.5 (TPscaled and TPadditive for δ15N. Large (> 220 cm G. cuvier did not feed at discrete trophic levels, but rather throughout the food web. These data provide key information on the ecological role of G. cuvier to improve the accuracy of regional food web modelling. This will enable a better understanding of the ecological impacts related to changes in the abundance of this predator.

  18. Competition influence in the segregation of the trophic niche of otariids: a case study using isotopic Bayesian mixing models in Galapagos pinnipeds.

    Science.gov (United States)

    Páez-Rosas, Diego; Rodríguez-Pérez, Mónica; Riofrío-Lazo, Marjorie

    2014-12-15

    The feeding success of predators is associated with the competition level for resources, and, thus, sympatric species are exposed to a potential trophic overlap. Isotopic Bayesian mixing models should provide a better understanding of the contribution of preys to the diet of predators and the feeding behavior of a species over time. The carbon and nitrogen isotopic signatures from pup hair samples of 93 Galapagos sea lions and 48 Galapagos fur seals collected between 2003 and 2009 in different regions (east and west) of the archipelago were analyzed. A PDZ Europa ANCA-GSL elemental analyzer interfaced with a PDZ Europa 20-20 continuous flow gas source mass spectrometer was employed. Bayesian models, SIAR and SIBER, were used to estimate the contribution of prey to the diet of predators, the niche breadth, and the trophic overlap level between the populations. Statistical differences in the isotopic values of both predators were observed over the time. The mixing model determined that Galapagos fur seals had a primarily teutophagous diet, whereas the Galapagos sea lions fed exclusively on fish in both regions of the archipelago. The SIBER analysis showed differences in the trophic niche between the two sea lion populations, with the western rookery of the Galapagos sea lion being the population with the largest trophic niche area. A trophic niche partitioning between Galapagos fur seals and Galapagos sea lions in the west of the archipelago is suggested by our results. At intraspecific level, the western population of the Galapagos sea lion (ZwW) showed higher trophic breadth than the eastern population, a strategy adopted by the ZwW to decrease the interspecific competition levels in the western region. Copyright © 2014 John Wiley & Sons, Ltd.

  19. Optical properties and composition changes in chromophoric dissolved organic matter along trophic gradients: Implications for monitoring and assessing lake eutrophication.

    Science.gov (United States)

    Zhang, Yunlin; Zhou, Yongqiang; Shi, Kun; Qin, Boqiang; Yao, Xiaolong; Zhang, Yibo

    2017-12-26

    Chromophoric dissolved organic matter (CDOM) is an important optically active substance in aquatic environments and plays a key role in light attenuation and in the carbon, nitrogen and phosphorus biogeochemical cycles. Although the optical properties, abundance, sources, cycles, compositions and remote sensing estimations of CDOM have been widely reported in different aquatic environments, little is known about the optical properties and composition changes in CDOM along trophic gradients. Therefore, we collected 821 samples from 22 lakes along a trophic gradient (oligotrophic to eutrophic) in China from 2004 to 2015 and determined the CDOM spectral absorption and nutrient concentrations. The total nitrogen (TN), total phosphorus (TP), and chlorophyll a (Chla) concentrations and the Secchi disk depth (SDD) ranged from 0.02 to 24.75 mg/L, 0.002-3.471 mg/L, 0.03-882.66 μg/L, and 0.05-17.30 m, respectively. The trophic state index (TSI) ranged from 1.55 to 98.91 and covered different trophic states, from oligotrophic to hyper-eutrophic. The CDOM absorption coefficient at 254 nm (a(254)) ranged from 1.68 to 92.65 m -1 . Additionally, the CDOM sources and composition parameters, including the spectral slope and relative molecular size value, exhibited a substantial variability from the oligotrophic level to other trophic levels. The natural logarithm value of the CDOM absorption, lna(254), is highly linearly correlated with the TSI (r 2  = 0.92, p 10 m -1 , respectively. The results suggested that the CDOM absorption coefficient a(254) might be a more sensitive single indicator of the trophic state than TN, TP, Chla and SDD. Therefore, we proposed a CDOM absorption coefficient and determined the threshold for defining the trophic state of a lake. Several advantages of measuring and estimating CDOM, including rapid experimental measurements, potential in situ optical sensor measurements and large-spatial-scale remote sensing estimations, make it

  20. Spring diet and trophic partitioning in an alpine lizard community ...

    African Journals Online (AJOL)

    The influences of species interactions on habitat use, restrictions in trophic availability and evolutionary history as determinant factors are discussed. Keywords: trophic ecology, communities, pseudocommunity analysis, Lacerta perspicillata, Lacerta andreanszkyi, Podarcis vaucheri, Quedenfeldtia trachyblepharus, Morocco ...

  1. Effect of β-endorphin on catecholamine levels in rat hypothalamus and cerebral cortex

    International Nuclear Information System (INIS)

    Slavnov, V.N.; Valueva, G.V.; Markov, V.V.; Luchitskii, E.V.

    1986-01-01

    The authors studied the effect of beta-endorphin on catecholamine concentrations in the hypothalmus and cerebral cortex in rats, as a contribution to the explanation of the mechanism of action of this peptide on certain pituitary trophic functions. Concentrations of dopamine, noradrenalin, and adrenalin were determined by a radioenzymatic method. A Mark 3 scintillation system was used for radiometric investigation of the samples. The results of these experiments indicate that beta-endorphin has a marked effect on brain catecholamine levels mainly in the hypothalamus

  2. Effect of. beta. -endorphin on catecholamine levels in rat hypothalamus and cerebral cortex

    Energy Technology Data Exchange (ETDEWEB)

    Slavnov, V.N.; Valueva, G.V.; Markov, V.V.; Luchitskii, E.V.

    1986-10-01

    The authors studied the effect of beta-endorphin on catecholamine concentrations in the hypothalmus and cerebral cortex in rats, as a contribution to the explanation of the mechanism of action of this peptide on certain pituitary trophic functions. Concentrations of dopamine, noradrenalin, and adrenalin were determined by a radioenzymatic method. A Mark 3 scintillation system was used for radiometric investigation of the samples. The results of these experiments indicate that beta-endorphin has a marked effect on brain catecholamine levels mainly in the hypothalamus.

  3. Trophic niche of squids: Insights from isotopic data in marine systems worldwide

    Science.gov (United States)

    Navarro, Joan; Coll, Marta; Somes, Christoper J.; Olson, Robert J.

    2013-10-01

    Cephalopods are an important prey resource for fishes, seabirds, and marine mammals, and are also voracious predators on crustaceans, fishes, squid and zooplankton. Because of their high feeding rates and abundance, squids have the potential to exert control on the recruitment of commercially important fishes. In this review, we synthesize the available information for two intrinsic markers (δ15N and δ13C isotopic values) in squids for all oceans and several types of ecosystems to obtain a global view of the trophic niches of squids in marine ecosystems. In particular, we aimed to examine whether the trophic positions and trophic widths of squid species vary among oceans and ecosystem types. To correctly compare across systems, we adjusted squid δ15N values for the isotopic variability of phytoplankton at the base of the food web provided by an ocean circulation-biogeochemistry-isotope model. Studies that focused on the trophic ecology of squids using isotopic techniques were few, and most of the information on squids was from studies on their predators. Our results showed that squids occupy a large range of trophic positions and exploit a large range of trophic resources, reflecting the versatility of their feeding behavior and confirming conclusions from food-web models. Clear differences in both trophic position and trophic width were found among oceans and ecosystem types. The study also reinforces the importance of considering the natural variation in isotopic values when comparing the isotopic values of consumers inhabiting different ecosystems.

  4. Chytrid parasitism facilitates trophic transfer between bloom-forming cyanobacteria and zooplankton (Daphnia).

    Science.gov (United States)

    Agha, Ramsy; Saebelfeld, Manja; Manthey, Christin; Rohrlack, Thomas; Wolinska, Justyna

    2016-10-13

    Parasites are rarely included in food web studies, although they can strongly alter trophic interactions. In aquatic ecosystems, poorly grazed cyanobacteria often dominate phytoplankton communities, leading to the decoupling of primary and secondary production. Here, we addressed the interface between predator-prey and host-parasite interactions by conducting a life-table experiment, in which four Daphnia galeata genotypes were maintained on quantitatively comparable diets consisting of healthy cyanobacteria or cyanobacteria infected by a fungal (chytrid) parasite. In four out of five fitness parameters, at least one Daphnia genotype performed better on parasitised cyanobacteria than in the absence of infection. Further treatments consisting of purified chytrid zoospores and heterotrophic bacteria suspensions established the causes of improved fitness. First, Daphnia feed on chytrid zoospores which trophically upgrade cyanobacterial carbon. Second, an increase in heterotrophic bacterial biomass, promoted by cyanobacterial decay, provides an additional food source for Daphnia. In addition, chytrid infection induces fragmentation of cyanobacterial filaments, which could render cyanobacteria more edible. Our results demonstrate that chytrid parasitism can sustain zooplankton under cyanobacterial bloom conditions, and exemplify the potential of parasites to alter interactions between trophic levels.

  5. The protozooplankton-ichthyoplankton trophic link: an overlooked aspect of aquatic food webs.

    Science.gov (United States)

    Montagnes, David J S; Dower, John F; Figueiredo, Gisela M

    2010-01-01

    Since the introduction of the microbial loop concept, awareness of the role played by protozooplankton in marine food webs has grown. By consuming bacteria, and then being consumed by metazooplankton, protozoa form a trophic link that channels dissolved organic material into the "classic" marine food chain. Beyond enhancing energy transfer to higher trophic levels, protozoa play a key role in improving the food quality of metazooplankton. Here, we consider a third role played by protozoa, but one that has received comparatively little attention: that as prey items for ichthyoplankton. For >100 years it has been known that fish larvae consume protozoa. Despite this, fisheries scientists and biological oceanographers still largely ignore protozoa when assessing the foodweb dynamics that regulate the growth and survival of larval fish. We review evidence supporting the importance of the protozooplankton-ichthyoplankton link, including examples from the amateur aquarium trade, the commercial aquaculture industry, and contemporary studies of larval fish. We then consider why this potentially important link continues to receive very little attention. We conclude by offering suggestions for quantifying the importance of the protozooplankton-ichthyoplankton trophic link, using both existing methods and new technologies.

  6. Stable isotopes, beaks and predators: a new tool to study the trophic ecology of cephalopods, including giant and colossal squids.

    Science.gov (United States)

    Cherel, Yves; Hobson, Keith A

    2005-08-07

    Cephalopods play a key role in the marine environment but knowledge of their feeding habits is limited by lack of data. Here, we have developed a new tool to investigate their feeding ecology by combining the use of their predators as biological samplers together with measurements of the stable isotopic signature of their beaks. Cephalopod beaks are chitinous hard structures that resist digestion and the stable isotope ratios of carbon (delta13C) and nitrogen (delta15N) are indicators of the foraging areas and trophic levels of consumers, respectively. First, a comparison of delta13C and delta15N values of different tissues from the same individuals showed that beaks were slightly enriched in 13C but highly impoverished in 15N compared with lipid-free muscle tissues. Second, beaks from the same species showed a progressive increase in their delta15N values with increasing size, which is in agreement with a dietary shift from lower to higher trophic levels during cephalopod growth. In the same way, there was an increase in the delta15N signature of various parts of the same lower beaks in the order rostrum, lateral walls and wings, which reflects the progressive growth and chitinization of the beaks in parallel with dietary changes. Third, we investigated the trophic structure of a cephalopod community for the first time. Values of delta15N indicate that cephalopods living in slope waters of the subantarctic Kerguelen Islands (n=18 species) encompass almost three distinct trophic levels, with a continuum of two levels between crustacean- and fish-eaters and a distinct higher trophic level occupied by the colossal squid Mesonychoteuthis hamiltoni. delta13C values demonstrated that cephalopods grow in three different marine ecosystems, with 16 species living and developing in Kerguelen waters and two species migrating from either Antarctica (Slosarczykovia circumantarctica) or the subtropics (the giant squid Architeuthis dux). The stable isotopic signature of beaks

  7. Unrevealing Parasitic Trophic Interactions—A Molecular Approach for Fluid-Feeding Fishes

    Directory of Open Access Journals (Sweden)

    Karine O. Bonato

    2018-03-01

    Full Text Available Fish diets have been traditionally studied through the direct visual identification of food items found in their stomachs. Stomach contents of Vandeliinae and Stegophilinae (family Trichomycteridae parasite catfishes, however, cannot be identified by usual optical methods due to their mucophagic, lepidophagic, or hematophagic diets, in such a way that the trophic interactions and the dynamics of food webs in aquatic systems involving these catfishes are mostly unknown. The knowledge about trophic interactions, including difficult relation between parasites and hosts, are crucial to understand the whole working of food webs. In this way, molecular markers can be useful to determine the truly hosts of these catfishes, proving a preference in their feeding behavior for specific organisms and not a generalist. Sequences of cytochrome oxidase subunit 1 (COI were successfully extracted and amplified from mucus or scales found in the stomach contents of two species of stegophilines, Homodiaetus anisitsi, and Pseudostegophilus maculatus, to identify the host species. The two species were found to be obligatory mucus-feeders and occasionally lepidophagic. Selection of host species is associated to host behavior, being constituted mainly by substrate-sifting benthivores. Characiformes are preferred hosts, but host choice depends on what characiform species are available in their environments, usually corresponding to the most abundant species. This is the first time that host species of parasitic fishes bearing mucophagous habits are identified, and demonstrates the effectiveness of the extraction and amplification of mitochondrial DNA from the ingested mucus in gut contents. The molecular markers effectively allowed determine parasite preferences and helps in better understanding the food web and trophic interaction on which fish species are involved. Despite, the methodology applied here can be used for an infinitive of organisms improving ecological

  8. Common carp disrupt ecosystem structure and function through middle-out effects

    Science.gov (United States)

    Kaemingk, Mark A.; Jolley, Jeffrey C.; Paukert, Craig P.; Willis, David W.; Henderson, Kjetil R.; Holland, Richard S.; Wanner, Greg A.; Lindvall, Mark L.

    2016-01-01

    Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and non-unidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes.

  9. Zooplankton trophic niches respond to different water types of the western Tasman Sea: A stable isotope analysis

    Science.gov (United States)

    Henschke, Natasha; Everett, Jason D.; Suthers, Iain M.; Smith, James A.; Hunt, Brian P. V.; Doblin, Martina A.; Taylor, Matthew D.

    2015-10-01

    The trophic relationships of 21 species from an oceanic zooplankton community were studied using stable isotopes of carbon and nitrogen. Zooplankton and suspended particulate organic matter (POM) were sampled in three different water types in the western Tasman Sea: inner shelf (IS), a cold core eddy (CCE) and a warm core eddy (WCE). δ15N values ranged from 3.9‰ for the parasitic copepod Sapphirina augusta to 10.2‰ for the euphausiid, Euphausia spinifera. δ13C varied from -22.6 to -19.4‰ as a result of the copepod Euchirella curticauda and E. spinifera. The isotopic composition of POM varied significantly among water types; as did the trophic enrichment of zooplankton over POM, with the lowest enrichment in the recently upwelled IS water type (0.5‰) compared to the warm core eddy (1.6‰) and cold core eddy (2.7‰). The WCE was an oligotrophic environment and was associated with an increased trophic level for omnivorous zooplankton (copepods and euphausiids) to a similar level as carnivorous zooplankton (chaetognaths). Therefore carnivory in zooplankton can increase in response to lower abundance and reduced diversity in their phytoplankton and protozoan prey. Trophic niche width comparisons across three zooplankton species: the salp Thalia democratica, the copepod Eucalanus elongatus and the euphausiid Thysanoessa gregaria, indicated that both niche partitioning and competition can occur within the zooplankton community. We have shown that trophic relationships among the zooplankton are dynamic and respond to different water types. The changes to the zooplankton isotopic niche, however, were still highly variable as result of oceanographic variation within water types.

  10. Assessing Lake Trophic Status: A Proportional Odds Logistic Regression Model

    Science.gov (United States)

    Lake trophic state classifications are good predictors of ecosystem condition and are indicative of both ecosystem services (e.g., recreation and aesthetics), and disservices (e.g., harmful algal blooms). Methods for classifying trophic state are based off the foundational work o...

  11. Isotope niche dimension and trophic overlap between bigheaded carps and native filter-feeding fish in the lower Missouri River, USA

    Science.gov (United States)

    Wang, Jianzhu; Chapman, Duane C.; Xu, Jun; Wang, Yang; Gu, Binhe

    2018-01-01

    Stable carbon and nitrogen isotope values (δ13C and δ15N) were used to evaluate trophic niche overlap between two filter-feeding fishes (known together as bigheaded carp) native to China, silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), and three native filter-feeding fish including bigmouth buffalo (Ictiobus cyprinellus), gizzard shad (Dorosoma cepedianum) and paddlefish (Polyodon spathula) in the lower Missouri River, USA, using the Bayesian Stable Isotope in R statistics. Results indicate that except for bigmouth buffalo, all species displayed similar trophic niche size and trophic diversity. Bigmouth buffalo occupied a small trophic niche and had the greatest trophic overlap with silver carp (93.6%) and bighead carp (94.1%) followed by gizzard shad (91.0%). Paddlefish had a trophic niche which relied on some resources different from those used by other species, and therefore had the lowest trophic overlap with bigheaded carp and other two native fish. The trophic overlap by bigheaded carp onto native fish was typically stronger than the reverse effects from native fish. Average niche overlap between silver carp and native species was as high as 71%, greater than niche overlap between bighead carp and native fish (64%). Our findings indicate that bigheaded carps are a potential threat to a diverse and stable native fish community.

  12. Characterisation (δ13C and δ15N isotopes) of the food webs in a New Zealand stream in the Waitakere Ranges, with emphasis on the trophic level of the endemic frog Leiopelma hochstetteri

    International Nuclear Information System (INIS)

    Najera-Hillman, E.; Alfaro, A.C.; Breen, B.B.; O'Shea, S.

    2009-01-01

    Leiopelma hochstetteri, the most widespread of New Zealand's native frogs, is recognised as threatened, and is fully protected by legislation. As a first step to characterise the diet and trophic level of L. hochstetteri within streams in the Waitakere Ranges, Auckland, stable carbon and nitrogen isotope analyses were undertaken on a variety of sympatric terrestrial and aquatic plant and animal species, including adult frogs. These results show that: (1) aquatic and terrestrial food webs are linked by terrestrial inputs into the stream; (2) invertebrate and vertebrate predators separate well into distinct trophic groups, and (3) L. hochstetteri occupies an intermediate trophic position among predators, with a diet, at least as an adult, comprising terrestrial invertebrates. Shortfin eels and banded kokopu are identified as potential predators of L. hochstetteri, but data for rats are inconclusive. These results have important implications for the conservation of New Zealand native frog species and riparian stream habitat. (author). 75 refs., 3 figs., 1 tab

  13. Parallel structure among environmental gradients and three trophic levels in a subarctic estuary

    Science.gov (United States)

    Speckman, Suzann G.; Piatt, John F.; Minte-Vera, Carolina V.; Parrish, Julia K.

    2005-07-01

    1999, when fish community structure changed markedly in lower Cook Inlet. Capelin ( Mallotus villosus), walleye pollock ( Theragra chalcogramma), and arrowtooth flounder ( Atheresthes stomias) were caught farther north than in previous years. Waters were significantly colder and more saline in 1999, a La Niña year, than in other years of the study. Interannual fluctuations in environmental conditions in lower Cook Inlet did not have substantial effects on zooplankton community structure, although abundance of individual taxa varied significantly. The abundance and distribution of chlorophyll α, zooplankton and forage fish were affected much more by spatial variability in physical oceanography than by interannual variability. Our examination of physical-biological linkages in lower Cook Inlet supports the concept of “bottom-up control,” i.e., that variability in the physical environment structures higher trophic-level communities by influencing their distribution and abundance across space.

  14. Impact of conservation areas on trophic interactions between apex predators and herbivores on coral reefs.

    Science.gov (United States)

    Rizzari, Justin R; Bergseth, Brock J; Frisch, Ashley J

    2015-04-01

    Apex predators are declining at alarming rates due to exploitation by humans, but we have yet to fully discern the impacts of apex predator loss on ecosystem function. In a management context, it is critically important to clarify the role apex predators play in structuring populations of lower trophic levels. Thus, we examined the top-down influence of reef sharks (an apex predator on coral reefs) and mesopredators on large-bodied herbivores. We measured the abundance, size structure, and biomass of apex predators, mesopredators, and herbivores across fished, no-take, and no-entry management zones in the Great Barrier Reef Marine Park, Australia. Shark abundance and mesopredator size and biomass were higher in no-entry zones than in fished and no-take zones, which indicates the viability of strictly enforced human exclusion areas as tools for the conservation of predator communities. Changes in predator populations due to protection in no-entry zones did not have a discernible influence on the density, size, or biomass of different functional groups of herbivorous fishes. The lack of a relationship between predators and herbivores suggests that top-down forces may not play a strong role in regulating large-bodied herbivorous coral reef fish populations. Given this inconsistency with traditional ecological theories of trophic cascades, trophic structures on coral reefs may need to be reassessed to enable the establishment of appropriate and effective management regimes. © 2014 Society for Conservation Biology.

  15. [Efficacy of compression knee-high socks ULCER X in treatment of venous-genesis trophic ulcers].

    Science.gov (United States)

    Bogdanets, L I; Bogachev, V Iu; Lobanov, V N; Smirnova, E S

    2013-01-01

    The study was aimed at comparatively assessing the efficacy of treatment for venous trophic ulcers at stages II-III of the wound process using special compression knee-length socks of the ULCER X kit (Sigvaris AG, St. Gallen, Switzerland) and long-stretch bandages Lauma. Compression therapy was included into the programme of outpatient treatment of forty 31-to-74-year-old patients presenting with trophic ulcers (stage II-III of the wound process) with an average area of 5,36±1,1 cm2. The Study Group consisting of 20 patients used compression knitted fabrics in the form of knee-length socks ULCER X and the comparison group (n=20) used long-stretch bandages Lauma. The obtained findings (6 months) demonstrated that using compression therapy exerted a positive effect on the process of healing of venous trophic ulcers, also proving advantages of compression therapy with the knee-length socks ULCER X that create an adequate level of pressure on the crus and maintain it in long-term daily use, reliably accelerating the healing of venous trophic ulcers as compared with elastic long-stretch bandages. The use of long-stretch elastic bandages in treatment of venous trophic ulcers turned out to be not only ineffective but fraught with a possibility of the development of various complications. During 6 months of follow up the patients using the special knee-length socks ULCER X were found to have 80 % of ulcers healed (16 patients), mainly within the first 2 months, whereas using elastic bandages resulted in only 30 % of healing (6 patients) by the end of the study. Along with it, we documented a considerable decrease in the malleolar circumference in the study group patients (from 30,05±0,78 to 28,35±0,86 cm) and in the control group from 31,2±30,35 to 30,25±0,75 cm), accompanied and followed by more than a two-fold increase in quality of life of the patients along all the parameters in the study group and a 1.4-fold increase in the control group patients.

  16. Diet compositions and trophic guild structure of the eastern Chukchi Sea demersal fish community

    Science.gov (United States)

    Whitehouse, George A.; Buckley, Troy W.; Danielson, Seth L.

    2017-01-01

    Fishes are an important link in Arctic marine food webs, connecting production of lower trophic levels to apex predators. We analyzed 1773 stomach samples from 39 fish species collected during a bottom trawl survey of the eastern Chukchi Sea in the summer of 2012. We used hierarchical cluster analysis of diet dissimilarities on 21 of the most well sampled species to identify four distinct trophic guilds: gammarid amphipod consumers, benthic invertebrate generalists, fish and shrimp consumers, and zooplankton consumers. The trophic guilds reflect dominant prey types in predator diets. We used constrained analysis of principal coordinates (CAP) to determine if variation within the composite guild diets could be explained by a suite of non-diet variables. All CAP models explained a significant proportion of the variance in the diet matrices, ranging from 7% to 25% of the total variation. Explanatory variables tested included latitude, longitude, predator length, depth, and water mass. These results indicate a trophic guild structure is present amongst the demersal fish community during summer in the eastern Chukchi Sea. Regular monitoring of the food habits of the demersal fish community will be required to improve our understanding of the spatial, temporal, and interannual variation in diet composition, and to improve our ability to identify and predict the impacts of climate change and commercial development on the structure and functioning of the Chukchi Sea ecosystem.

  17. Successional changes in trophic interactions support a mechanistic model of post-fire population dynamics.

    Science.gov (United States)

    Smith, Annabel L

    2018-01-01

    Models based on functional traits have limited power in predicting how animal populations respond to disturbance because they do not capture the range of demographic and biological factors that drive population dynamics, including variation in trophic interactions. I tested the hypothesis that successional changes in vegetation structure, which affected invertebrate abundance, would influence growth rates and body condition in the early-successional, insectivorous gecko Nephrurus stellatus. I captured geckos at 17 woodland sites spanning a succession gradient from 2 to 48 years post-fire. Body condition and growth rates were analysed as a function of the best-fitting fire-related predictor (invertebrate abundance or time since fire) with different combinations of the co-variates age, sex and location. Body condition in the whole population was positively affected by increasing invertebrate abundance and, in the adult population, this effect was most pronounced for females. There was strong support for a decline in growth rates in weight with time since fire. The results suggest that increased early-successional invertebrate abundance has filtered through to a higher trophic level with physiological benefits for insectivorous geckos. I integrated the new findings about trophic interactions into a general conceptual model of mechanisms underlying post-fire population dynamics based on a long-term research programme. The model highlights how greater food availability during early succession could drive rapid population growth by contributing to previously reported enhanced reproduction and dispersal. This study provides a framework to understand links between ecological and physiological traits underlying post-fire population dynamics.

  18. From the epipelagic zone to the abyss: Trophic structure at two seamounts in the subtropical and tropical Eastern Atlantic - Part I zooplankton and micronekton

    Science.gov (United States)

    Denda, Anneke; Stefanowitsch, Benjamin; Christiansen, Bernd

    2017-12-01

    Specific mechanisms, driving trophic interactions within the pelagic community may be highly variable in different seamount systems. This study investigated the trophic structure of zooplankton and micronekton above and around Ampère and Senghor, two shallow seamounts in the subtropical and tropical Eastern Atlantic, and over the adjacent abyssal plains. For the identification of food sources and trophic positions stable isotope ratios (δ13C and δ15N) were used. δ13C ranged from -24.7‰ to -15.0‰ and δ15N covered a total range of 0.9-15.9‰. Based on epipelagic particulate organic matter, zooplankton and micronekton usually occupied the 1st-3rd trophic level, including herbivorous, omnivorous and carnivorous taxa. δ13C and δ15N values were generally lower in zooplankton and micronekton of the subtropical waters as compared to the tropical region, due to the differing nutrient availability and phytoplankton communities. Correlations between δ13C and δ15N values of particulate organic matter, zooplankton, micronekton and benthopelagic fishes suggest a linear food chain based on a single energy source from primary production for Ampère Seamount, but no evidence was found for an autochthonus seamount production as compared to the open ocean reference site. Between Senghor Seamount and the open ocean δ13C signatures indicate that hydrodynamic effects at seamounts may modify the energy supply at times, but evidence for a seamount effect on the trophic structure of the pelagic communities was weak, which supports the assumption that seamount communities rely to a large extent on advected food sources.

  19. The genetic architecture of novel trophic specialists: larger effect sizes are associated with exceptional oral jaw diversification in a pupfish adaptive radiation.

    Science.gov (United States)

    Martin, Christopher H; Erickson, Priscilla A; Miller, Craig T

    2017-01-01

    The genetic architecture of adaptation is fundamental to understanding the mechanisms and constraints governing diversification. However, most case studies focus on loss of complex traits or parallel speciation in similar environments. It is still unclear how the genetic architecture of these local adaptive processes compares to the architecture of evolutionary transitions contributing to morphological and ecological novelty. Here, we identify quantitative trait loci (QTL) between two trophic specialists in an excellent case study for examining the origins of ecological novelty: a sympatric radiation of pupfishes endemic to San Salvador Island, Bahamas, containing a large-jawed scale-eater and a short-jawed molluscivore with a skeletal nasal protrusion. These specialized niches and trophic traits are unique among over 2000 related species. Measurements of the fitness landscape on San Salvador demonstrate multiple fitness peaks and a larger fitness valley isolating the scale-eater from the putative ancestral intermediate phenotype of the generalist, suggesting that more large-effect QTL should contribute to its unique phenotype. We evaluated this prediction using an F2 intercross between these specialists. We present the first linkage map for pupfishes and detect significant QTL for sex and eight skeletal traits. Large-effect QTL contributed more to enlarged scale-eater jaws than the molluscivore nasal protrusion, consistent with predictions from the adaptive landscape. The microevolutionary genetic architecture of large-effect QTL for oral jaws parallels the exceptional diversification rates of oral jaws within the San Salvador radiation observed over macroevolutionary timescales and may have facilitated exceptional trophic novelty in this system. © 2016 John Wiley & Sons Ltd.

  20. Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food Web.

    Science.gov (United States)

    Boon, Jan P; Lewis, Wilma E; Tjoen-A-Choy, Michael R; Allchin, Colin R; Law, Robin J; De Boer, Jacob; Ten Hallers-Tjabbes, Cato C; Zegers, Bart N

    2002-10-01

    The levels of individual PBDE congeners were investigated in the invertebrate species whelk (Buccinum undatum), seastar (Asterias rubens), and hermit crab (Pagurus bernhardus), the gadoid fish species whiting (Merlangius merlangus) and cod (Gadus morhua), and the marine mammal species harbor seal (Phoca vitulina) and harbor porpoise (Phocoena phocoena). These species are all important representatives of different trophic levels of the North Sea food web. All six major PBDE congeners detected (BDEs 28, 47, 99, 100, 153, and 154) are most prevalent in the commercial Penta-BDE formulation. There is no evidence for the occurrence of the Octa-BDE formulation in the North Sea food web, since its dominant congener, BDE183, was never detected. BDE209, the main congener (> 97%) in the Deca-BDE formulation, was detected only in a minority of the samples and always in concentrations around the limit of detection. Since BDE209 is often the major BDE congener in sediments from the area, the main reason for its low concentrations in biota from the North Sea seems to be a relatively low bioaccumulation potential. This can either be due to a low uptake rate of the very large molecule or a relatively rapid excretion after biotransformation. Since all invertebrates investigated are sentinel species, they are highly representative for the area of capture. The highest lipid-normalized concentrations of PBDEs in the invertebrates occurred near the mouth of the river Tees at the East coast of the UK. The geographical distribution of the PBDEs can be explained by the residual currents in the area. The direction of these currents differs between the summer and the winter season as a result of the presence or absence of vertical summer stratification of the deeper waters north of the Dogger Bank. Summer stratification results in the development of a density-driven bottom water current formed after the onset of vertical stratification of the water column in May leaving the UK coast near

  1. New Methods of Treatment for Trophic Lesions of the Lower Extremities in Patients with Diabetes Mellitus

    Directory of Open Access Journals (Sweden)

    S.V. Bolgarska

    2016-08-01

    Full Text Available Introduction. Complications in the form of trophic ulcers of the lower extremities are one of the serious consequences of diabetes mellitus (DM, as they often lead to severe health and social problems, up to high amputations. The aim of the study was the development and clinical testing of diagnostic and therapeutic algorithm for the comprehensive treatment of trophic ulcers of the lower extremities in patients with DM. Materials and methods. Here are presented the results of treatment of 63 patients (42 women and 21 men with neuropathic type of trophic lesions of the lower limbs or postoperative defects at the stage of granulation. Of them, 32 patients (study group received local intradermal injections of hyaluronic acid preparations and sodium succinate (Lacerta into the extracellular matrix. Patients of the comparison group were treated with hydrocolloid materials (hydrocoll, granuflex. The level of glycated hemoglobin, the degree of circulatory disorders (using ankle brachial index, before and after the test with a load and neuropathic disorders (on a scale for the evaluation of neurologic dysfunctions — NDS were assessed in patients. Results. The results of treatment were assessed by the rate of defect healing during 2 or more months. In the study group, 24 patients showed complete healing of the defect (75 %, while in the control group the healing was observed in 16 patients (51.6 %. During the year, relapses occurred in 22.2 % of cases in the study group, and in 46.9 % — in the control one (p < 0.05. Conclusion. The developed method of treatment using Lacerta allowed to increase the effectiveness of therapy, to speed recovery, to decrease a number of complications in patients with DM and trophic ulcers of the lower extremities.

  2. [THE CORRECTION OF TROPHIC DISORDERS IN CHILDREN OF CHRONIC GASTRODUODENITIS WITH METHOD LOW-FREQUENCY LIGHT-MAGNETOTHERAPY].

    Science.gov (United States)

    Kolosova, T A; Sadovnikova, I V; Belousova, T E

    2015-01-01

    The results of a survey of school children with chronic gastroduodenitis when applying at an early period the medical rehabilitation with method low-frequency light-magnetotherapy. During treatment of hospital was evaluated vegetative-trophic status with methods of cardiointervalography and thermovision functional tests. In normalizes clinical parameters was correction in dynamics of the vegetative status in children, it confirms the effectiveness of the therapy. It is proved, that the use of low-frequency light-magnetotherapy has a positive effect on the vegetative--trophic provision an organism and normalizes the vegetative dysfunction.

  3. Use of Shark Dental Protein to Estimate Trophic Position via Amino Acid Compound-Specific Isotope Analysis

    Science.gov (United States)

    Hayes, M.; Herbert, G.; Ellis, G.

    2017-12-01

    The diets of apex predators such as sharks are expected to change in response to overfishing of their mesopredator prey, but pre-anthropogenic baselines necessary to test for such changes are lacking. Stable isotope analysis (SIA) of soft tissues is commonly used to study diets in animals based on the bioaccumulation of heavier isotopes of carbon and nitrogen with increasing trophic level. In specimens representing pre-anthropogenic baselines, however, a modified SIA approach is needed to deal with taphonomic challenges, such as loss of soft tissues or selective loss of less stable amino acids (AAs) in other sources of organic compounds (e.g., teeth or bone) which can alter bulk isotope values. These challenges can be overcome with a compound-specific isotope analysis of individual AAs (AA-CSIA), but this first requires a thorough understanding of trophic enrichment factors for individual AAs within biomineralized tissues. In this study, we compare dental and muscle proteins of individual sharks via AA-CSIA to determine how trophic position is recorded within teeth and whether that information differs from that obtained from soft tissues. If skeletal organics reliably record information about shark ecology, then archaeological and perhaps paleontological specimens can be used to investigate pre-anthropogenic ecosystems. Preliminary experiments show that the commonly used glutamic acid/phenylalanine AA pairing may not be useful for establishing trophic position from dental proteins, but that estimated trophic position determined from alternate AA pairs are comparable to those from muscle tissue within the same species.

  4. Coastal urban lighting has ecological consequences for multiple trophic levels under the sea.

    Science.gov (United States)

    Bolton, D; Mayer-Pinto, M; Clark, G F; Dafforn, K A; Brassil, W A; Becker, A; Johnston, E L

    2017-01-15

    Urban land and seascapes are increasingly exposed to artificial lighting at night (ALAN), which is a significant source of light pollution. A broad range of ecological effects are associated with ALAN, but the changes to ecological processes remain largely unstudied. Predation is a key ecological process that structures assemblages and responds to natural cycles of light and dark. We investigated the effect of ALAN on fish predatory behaviour, and sessile invertebrate prey assemblages. Over 21days fish and sessile assemblages were exposed to 3 light treatments (Day, Night and ALAN). An array of LED spotlights was installed under a wharf to create the ALAN treatments. We used GoPro cameras to film during the day and ALAN treatments, and a Dual frequency IDentification SONar (DIDSON) to film during the night treatments. Fish were most abundant during unlit nights, but were also relatively sedentary. Predatory behaviour was greatest during the day and under ALAN than at night, suggesting that fish are using structures for non-feeding purposes (e.g. shelter) at night, but artificial light dramatically increases their predatory behaviour. Altered predator behaviour corresponded with structural changes to sessile prey assemblages among the experimental lighting treatments. We demonstrate the direct effects of artificial lighting on fish behaviour and the concomitant indirect effects on sessile assemblage structure. Current and future projected use of artificial lights has the potential to significantly affect predator-prey interactions in marine systems by altering habitat use for both predators and prey. However, developments in lighting technology are a promising avenue for mitigation. This is among the first empirical evidence from the marine system on how ALAN can directly alter predation, a fundamental ecosystem process, and have indirect trophic consequences. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Trophic facilitation or limitation? Comparative effects of pumas and black bears on the scavenger community.

    Science.gov (United States)

    Allen, Maximilian L; Elbroch, L Mark; Wilmers, Christopher C; Wittmer, Heiko U

    2014-01-01

    Scavenging is a widespread behaviour and an important process influencing food webs and ecological communities. Large carnivores facilitate the movement of energy across trophic levels through the scavenging and decomposition of their killed prey, but competition with large carnivores is also likely to constrain acquisition of carrion by scavengers. We used an experimental approach based on motion-triggered video cameras at black-tailed deer (Odocoileus hemionus columbianus) carcasses to measure the comparative influences of two large carnivores in the facilitation and limitation of carrion acquisition by scavengers. We found that pumas (Puma concolor) and black bears (Ursus americanus) had different effects on their ecological communities. Pumas, as a top-level predator, facilitated the consumption of carrion by scavengers, despite significantly reducing their observed sum feeding times (165.7 min ± 21.2 SE at puma kills 264.3 min ± 30.1 SE at control carcasses). In contrast, black bears, as the dominant scavenger in the system, limited consumption of carrion by scavengers as evidenced by the observed reduction of scavenger species richness recorded at carcasses where they were present (mean = 2.33 ± 0.28 SE), compared to where they were absent (mean = 3.28 ± 0.23 SE). Black bears also had large negative effects on scavenger sum feeding times (88.5 min ± 19.8 SE at carcasses where bears were present, 372.3 min ± 50.0 SE at carcasses where bears were absent). In addition, we found that pumas and black bears both increased the nestedness (a higher level of order among species present) of the scavenger community. Our results suggest that scavengers have species-specific adaptions to exploit carrion despite large carnivores, and that large carnivores influence the structure and composition of scavenger communities. The interactions between large carnivores and scavengers should be considered in future studies of food webs and ecological communities.

  6. Application of nitrogen and carbon stable isotopes (δ(15N and δ(13C to quantify food chain length and trophic structure.

    Directory of Open Access Journals (Sweden)

    Matthew J Perkins

    Full Text Available Increasingly, stable isotope ratios of nitrogen (δ(15N and carbon (δ(13C are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR using δ(15N, and carbon range (CR using δ(13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15N or δ(13C from source to consumer between trophic levels and among food chains. δ(15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰, and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority

  7. Application of Nitrogen and Carbon Stable Isotopes (δ15N and δ13C) to Quantify Food Chain Length and Trophic Structure

    Science.gov (United States)

    Perkins, Matthew J.; McDonald, Robbie A.; van Veen, F. J. Frank; Kelly, Simon D.; Rees, Gareth; Bearhop, Stuart

    2014-01-01

    Increasingly, stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ15N, and carbon range (CR) using δ13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ15N or δ13C from source to consumer) between trophic levels and among food chains. δ15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems

  8. Application of nitrogen and carbon stable isotopes (δ(15)N and δ(13)C) to quantify food chain length and trophic structure.

    Science.gov (United States)

    Perkins, Matthew J; McDonald, Robbie A; van Veen, F J Frank; Kelly, Simon D; Rees, Gareth; Bearhop, Stuart

    2014-01-01

    Increasingly, stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ(15)N, and carbon range (CR) using δ(13)C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15)N or δ(13)C from source to consumer) between trophic levels and among food chains. δ(15)N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13)C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13)C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of

  9. Mercury biomagnification and the trophic structure of the ichthyofauna from a remote lake in the Brazilian Amazon.

    Science.gov (United States)

    Azevedo-Silva, Claudio Eduardo; Almeida, Ronaldo; Carvalho, Dario P; Ometto, Jean P H B; de Camargo, Plínio B; Dorneles, Paulo R; Azeredo, Antonio; Bastos, Wanderley R; Malm, Olaf; Torres, João P M

    2016-11-01

    The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in the calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ 13 C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapó (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ 13 C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively. These findings

  10. The dynamics the quantitative changes of mycoflora in two lakes differing in trophicity (Poland. I.

    Directory of Open Access Journals (Sweden)

    Teresa Korniłłowicz

    2014-08-01

    Full Text Available It was demonstrated that the number of saprophytic fungi in the population of plankton in mesotrophic lake changing to eutrophic (Lake Piaseczno was mountained a similiar level (average values as in the eutrophic one (Lake Głębokie. The seasonal and annual changes in the number of fungi in the waters of the lake with lower trophicity were markedly stronger than those in the lake with higher trophicity. In the mesotrophic lake this was connected with the intensity of phytoplankton development. The greatest accumulation of fungi occured in the waters of littoral zone in both lakes and in the pelagial metha- and hypolimniun of the Lake Piaseczno.

  11. Trophic roles of scavenger beetles in relation to decomposition stages and seasons

    Directory of Open Access Journals (Sweden)

    Noelia I. Zanetti

    2015-06-01

    Full Text Available Carcasses represent a trophic and reproductive resource or shelter for arthropods, which are a representative component of the decomposition process. Four experiments, one per season, were conducted in a semi-rural area of Bahía Blanca, Argentina, to study the trophic roles of cadaveric beetles, evaluating the abundance, composition and dominance during all decomposition stages and seasons. Species of necrophagous, necrophilous and omnivorous habits were found. Abundance, composition and dominance of beetles in relation to their trophic roles changed according to seasons and decomposition stages. Guilds and patterns of succession were established in relation to those periods. Trophic roles could be an indicator of beetle associations with decomposition stages and seasons.

  12. Aspects of the trophic ecology of Liza falcipinnis (Valenciennes 1836)

    African Journals Online (AJOL)

    Aspects of the trophic ecology of Liza falcipinnis (Valenciennes) were studied in the Cross River Estuary (CRE) east of the Niger Delta (Nigeria). The trophic spectrum showed that L. falcipinnis fed on a wide variety of food resources. From the index of relative importance (IRI), L. falcipinnis fed primarily on diatoms, FPOM, ...

  13. Physical Drivers Vs. Effects of the Wolf-Elk Trophic Cascade on Fluvial Channel Planform, Olympic National Park, Washington

    Science.gov (United States)

    East, A. E.; Jenkins, K. J.; Happe, P. J.; Bountry, J.; Beechie, T. J.; Mastin, M. C.; Sankey, J. B.; Randle, T. J.

    2016-12-01

    Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We use a 74-year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, U.S.A., to investigate whether physical or trophic-cascade-driven ecological factors—excessive elk impacts after wolves were extirpated a century ago—are the dominant controls on channel planform of these gravel-bed rivers. We find that channel width and braiding show strong relationships with recent flood history; all four rivers have widened significantly in recent decades, consistent with increased flood activity since the 1970s. Channel planform also reflects sediment-supply changes, shown, for example, by the response of the Elwha River to a landslide. We surmise that the Hoh River, which shows a multi-decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. These rivers demonstrate rapid transmission of climatic signals through relatively short sediment-routing systems that lack substantial buffering by sediment storage. We infer no correspondence between channel evolution and elk abundance, suggesting that in this system effects of the wolf-driven trophic cascade are subsidiary to physical controls on channel morphology. Our examinations of stage-discharge history, historical maps, photographs, and descriptions, and empirical geomorphic thresholds do not support a previous conceptual model that these rivers underwent a fundamental geomorphic transition (widening, and a shift from single-thread to braided) resulting from large elk populations in the early 20th century. These findings differ from previous interpretations of Olympic National Park river dynamics, and also contrast with previous findings in Yellowstone National Park, where legacy effects of abundant elk nearly a century ago apparently still affect

  14. Disruption of Trophic Inhibitory Signaling in Autism Sepctrum Disorders

    Science.gov (United States)

    2016-12-01

    1 AWARD NUMBER: W81XWH-14-1-0433 TITLE: Disruption of Trophic Inhibitory Signaling in Autism Sepctrum Disorders PRINCIPAL INVESTIGATOR: Anis...SUBTITLE 5a. CONTRACT NUMBER Disruption of Trophic Inhibitory Signaling in Autism Sepctrum Disorders 5b. GRANT NUMBER W81XWH-14-1-0433 5c. PROGRAM...chloride co-transporters that control EGABA could be used as a corrective strategy for the synaptic and circuit disruptions demonstrated in the

  15. Macrophytes shape trophic niche variation among generalist fishes.

    Directory of Open Access Journals (Sweden)

    Ivana Vejříková

    Full Text Available Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation among generalist fishes is facilitated by the presence of macrophytes, which provides niches and predation shelter for fish and their prey items. Based on results from stable nitrogen (δ15N and carbon (δ13C isotopic mixing models, perch (Perca fluviatilis L. and rudd (Scardinius erythrophthalmus (L. showed larger individual variation (i.e., variance in trophic position in Milada as compared to Most, whereas no significant between-lake differences were observed for roach (Rutilus rutilus (L.. Contrary to our hypothesis, all the three species showed significantly lower individual variation in the relative reliance on littoral food resources in Milada than in Most. Rudd relied significantly more whereas perch and roach relied less on littoral food resources in Milada than in Most, likely due to prevalent herbivory by rudd and prevalent zooplanktivory by perch and roach in the macrophyte-rich Milada as compared to macrophyte-poor Most. Our study demonstrates how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation among generalist fishes with different ontogenetic trajectories, and hence

  16. Macrophytes shape trophic niche variation among generalist fishes

    Science.gov (United States)

    Vejřík, Lukáš; Šmejkal, Marek; Čech, Martin; Sajdlová, Zuzana; Frouzová, Jaroslava; Kiljunen, Mikko; Peterka, Jiří

    2017-01-01

    Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation among generalist fishes is facilitated by the presence of macrophytes, which provides niches and predation shelter for fish and their prey items. Based on results from stable nitrogen (δ15N) and carbon (δ13C) isotopic mixing models, perch (Perca fluviatilis L.) and rudd (Scardinius erythrophthalmus (L.)) showed larger individual variation (i.e., variance) in trophic position in Milada as compared to Most, whereas no significant between-lake differences were observed for roach (Rutilus rutilus (L.)). Contrary to our hypothesis, all the three species showed significantly lower individual variation in the relative reliance on littoral food resources in Milada than in Most. Rudd relied significantly more whereas perch and roach relied less on littoral food resources in Milada than in Most, likely due to prevalent herbivory by rudd and prevalent zooplanktivory by perch and roach in the macrophyte-rich Milada as compared to macrophyte-poor Most. Our study demonstrates how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation among generalist fishes with different ontogenetic trajectories, and hence the overall

  17. Assessing effects of a mining and municipal sewage effluent mixture on fathead minnow (Pimephales promelas) reproduction using a novel, field-based trophic-transfer artificial stream.

    Science.gov (United States)

    Rickwood, Carrie J; Dubé, Monique G; Weber, Lynn P; Lux, Sarah; Janz, David M

    2008-01-31

    The Junction Creek watershed, located in Sudbury, ON, Canada receives effluent from three metal mine wastewater treatment plants, as well as a municipal wastewater (MWW) discharge. Effects on fish have been documented within the creek (decreased egg size and increased metal body burdens). It has been difficult to identify the cause of the effects observed due to the confounded nature of the creek. The objectives of this investigation were to assess the: (1) effects of a mine effluent and municipal wastewater (CCMWW) mixture on fathead minnow (FHM; Pimephales promelas) reproduction in an on-site artificial stream and (2) importance of food (Chironomus tentans) as a source of exposure using a trophic-transfer system. Exposures to CCMWW through the water significantly decreased egg production and spawning events. Exposure through food and water using the trophic-transfer system significantly increased egg production and spawning events. Embryos produced in the trophic-transfer system showed similar hatching success but increased incidence and severity of deformities after CCMWW exposure. We concluded that effects of CCMWW on FHM were more apparent when exposed through the water. Exposure through food and water may have reduced effluent toxicity, possibly due to increased nutrients and organic matter, which may have reduced metal bioavailability. More detailed examination of metal concentrations in the sediment, water column, prey (C. tentans) and FHM tissues is recommended to better understand the toxicokinetics of potential causative compounds within the different aquatic compartments when conducting exposures through different pathways.

  18. The trophic responses of two different rodent-vector-plague systems to climate change.

    Science.gov (United States)

    Xu, Lei; Schmid, Boris V; Liu, Jun; Si, Xiaoyan; Stenseth, Nils Chr; Zhang, Zhibin

    2015-02-07

    Plague, the causative agent of three devastating pandemics in history, is currently a re-emerging disease, probably due to climate change and other anthropogenic changes. Without understanding the response of plague systems to anthropogenic or climate changes in their trophic web, it is unfeasible to effectively predict years with high risks of plague outbreak, hampering our ability for effective prevention and control of the disease. Here, by using surveillance data, we apply structural equation modelling to reveal the drivers of plague prevalence in two very different rodent systems: those of the solitary Daurian ground squirrel and the social Mongolian gerbil. We show that plague prevalence in the Daurian ground squirrel is not detectably related to its trophic web, and that therefore surveillance efforts should focus on detecting plague directly in this ecosystem. On the other hand, plague in the Mongolian gerbil is strongly embedded in a complex, yet understandable trophic web of climate, vegetation, and rodent and flea densities, making the ecosystem suitable for more sophisticated low-cost surveillance practices, such as remote sensing. As for the trophic webs of the two rodent species, we find that increased vegetation is positively associated with higher temperatures and precipitation for both ecosystems. We furthermore find a positive association between vegetation and ground squirrel density, yet a negative association between vegetation and gerbil density. Our study thus shows how past surveillance records can be used to design and improve existing plague prevention and control measures, by tailoring them to individual plague foci. Such measures are indeed highly needed under present conditions with prevailing climate change. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  19. The trophic responses of two different rodent–vector–plague systems to climate change

    Science.gov (United States)

    Xu, Lei; Schmid, Boris V.; Liu, Jun; Si, Xiaoyan; Stenseth, Nils Chr.; Zhang, Zhibin

    2015-01-01

    Plague, the causative agent of three devastating pandemics in history, is currently a re-emerging disease, probably due to climate change and other anthropogenic changes. Without understanding the response of plague systems to anthropogenic or climate changes in their trophic web, it is unfeasible to effectively predict years with high risks of plague outbreak, hampering our ability for effective prevention and control of the disease. Here, by using surveillance data, we apply structural equation modelling to reveal the drivers of plague prevalence in two very different rodent systems: those of the solitary Daurian ground squirrel and the social Mongolian gerbil. We show that plague prevalence in the Daurian ground squirrel is not detectably related to its trophic web, and that therefore surveillance efforts should focus on detecting plague directly in this ecosystem. On the other hand, plague in the Mongolian gerbil is strongly embedded in a complex, yet understandable trophic web of climate, vegetation, and rodent and flea densities, making the ecosystem suitable for more sophisticated low-cost surveillance practices, such as remote sensing. As for the trophic webs of the two rodent species, we find that increased vegetation is positively associated with higher temperatures and precipitation for both ecosystems. We furthermore find a positive association between vegetation and ground squirrel density, yet a negative association between vegetation and gerbil density. Our study thus shows how past surveillance records can be used to design and improve existing plague prevention and control measures, by tailoring them to individual plague foci. Such measures are indeed highly needed under present conditions with prevailing climate change. PMID:25540277

  20. Climate change and ocean acidification impacts on lower trophic levels and the export of organic carbon to the deep ocean

    Directory of Open Access Journals (Sweden)

    A. Yool

    2013-09-01

    Full Text Available Most future projections forecast significant and ongoing climate change during the 21st century, but with the severity of impacts dependent on efforts to restrain or reorganise human activity to limit carbon dioxide (CO2 emissions. A major sink for atmospheric CO2, and a key source of biological resources, the World Ocean is widely anticipated to undergo profound physical and – via ocean acidification – chemical changes as direct and indirect results of these emissions. Given strong biophysical coupling, the marine biota is also expected to experience strong changes in response to this anthropogenic forcing. Here we examine the large-scale response of ocean biogeochemistry to climate and acidification impacts during the 21st century for Representative Concentration Pathways (RCPs 2.6 and 8.5 using an intermediate complexity global ecosystem model, MEDUSA-2.0. The primary impact of future change lies in stratification-led declines in the availability of key nutrients in surface waters, which in turn leads to a global decrease (1990s vs. 2090s in ocean productivity (−6.3%. This impact has knock-on consequences for the abundance of the low trophic level biogeochemical actors modelled by MEDUSA-2.0 (−5.8%, and these would be expected to similarly impact higher trophic level elements such as fisheries. Related impacts are found in the flux of organic material to seafloor communities (−40.7% at 1000 m, and in the volume of ocean suboxic zones (+12.5%. A sensitivity analysis removing an acidification feedback on calcification finds that change in this process significantly impacts benthic communities, suggesting that a~better understanding of the OA-sensitivity of calcifying organisms, and their role in ballasting sinking organic carbon, may significantly improve forecasting of these ecosystems. For all processes, there is geographical variability in change – for instance, productivity declines −21% in the Atlantic and increases +59% in

  1. Trophic transference of microplastics under a low exposure scenario: Insights on the likelihood of particle cascading along marine food-webs.

    Science.gov (United States)

    Santana, M F M; Moreira, F T; Turra, A

    2017-08-15

    Microplastics are emergent pollutants in marine environments, whose risks along food-web still need to be understood. Within this knowledge gap, MPs transference and persistence along trophic levels are key processes. We assessed the potential occurrence of these processes considering a less extreme scenario of exposure than used previously, with microplastics present only in the hemolymph of prey (the mussel Perna perna) and absent in the gut cavity. Predators were the crab Callinectes ornatus and the puffer fish Spheoeroides greeleyi. Transference of microplastics occurred from prey to predators but without evidences of particle persistence in their tissues after 10days of exposure. This suggests a reduced likelihood of trophic cascading of particles and, consequently, a reduced risk of direct impacts of microplastics on higher trophic levels. However, the contact with microplastics along food-webs is still concerning, modulated by the concentration of particles in prey and predators' depuration capacity and rate. Copyright © 2017. Published by Elsevier Ltd.

  2. The transfer and fate of Pb from sewage sludge amended soil in a multi-trophic food chain: a comparison with the labile elements Cd and Zn.

    Science.gov (United States)

    Dar, Mudasir Irfan; Khan, Fareed Ahmad; Green, Iain D; Naikoo, Mohd Irfan

    2015-10-01

    The contamination of agroecosystems due to the presence of trace elements in commonly used agricultural materials is a serious issue. The most contaminated material is usually sewage sludge, and the sustainable use of this material within agriculture is a major concern. This study addresses a key issue in this respect, the fate of trace metals applied to soil in food chains. The work particularly addresses the transfer of Pb, which is an understudied element in this respect, and compares the transfer of Pb with two of the most labile metals, Cd and Zn. The transfer of these elements was determined from sludge-amended soils in a food chain consisting of Indian mustard (Brassica juncea), the mustard aphid (Lipaphis erysimi) and a predatory beetle (Coccinella septempunctata). The soil was amended with sludge at rates of 0, 5, 10 and 20 % (w/w). Results showed that Cd was readily transferred through the food chain until the predator trophic level. Zn was the most readily transferred element in the lower trophic levels, but transfer to aphids was effectively restricted by the plant regulating shoot concentration. Pb had the lowest level of transfer from soil to shoot and exhibited particular retention in the roots. Nevertheless, Pb concentrations were significantly increased by sludge amendment in aphids, and Pb was increasingly transferred to ladybirds as levels increased. The potential for Pb to cause secondary toxicity to organisms in higher trophic levels may have therefore been underestimated.

  3. Trophic dynamics of few selected nearshore coastal finfishes with emphasis on prawns as prey item

    Science.gov (United States)

    Velip, Dinesh T.; Rivonker, Chandrashekher U.

    2018-06-01

    A trophic dynamic study of marine finfishes was undertaken based on stomach content analysis of twenty four species (N = 1742) collected from the nearshore coastal waters off Goa, west coast of India (15°29‧07.6″ N to 15°34‧44.3″ N, and 73°38‧10.5″ E to 73°46‧03.1″ E) during November 2010 to May 2013. This study aimed to thoroughly understand the feeding attributes of finfishes, and comprehend the possible effects of bycatch-related loss of biomass on trophic ecology. The study assessed diet preferences of the finfishes, their feeding guilds, significance of prawns as prey items, and the influence of mouth parts in prey selection. Altogether 84 prey taxa were identified from the stomach contents. Percentage Index of Relative Importance (IRI) values revealed that zooplankton (34.74), prawns (21.71), phytoplankton (19.80), and teleosts (18.62) were the major prey categories, and, among prawns, Metapenaeus dobsoni (%IRI = 19.34) was the single-most important prey item. Cluster analysis revealed three major trophic guilds namely 'teleost feeders' (mean Trophic Level (TrL) = 4.06 ± 0.42; mean B = 0.46 ± 0.24), 'zooplankton feeders' (mean TrL = 3.43 ± 0.29; mean B = 0.23 ± 0.13), and 'prawn feeders' (mean TrL = 3.86 ± 0.25; mean B = 0.48 ± 0.32), with low diet overlap among them. Principal Component Analysis of prey categories and mouth parts of finfishes suggested that zooplanktivory is associated with gill raker density as well as number of gill arches bearing rakers, whereas gape height determined the size of large-sized prey (fish and invertebrates). The study identified M. dobsoni, mysis and teleosts as highly influential prey for predatory finfishes. The present results could be useful to resolve broader issues in fisheries management.

  4. Trait- and size-based descriptions of trophic links in freshwater food webs: current status and perspectives

    Directory of Open Access Journals (Sweden)

    David S. Boukal

    2014-04-01

    Full Text Available Biotic interactions in aquatic communities are dominated by predation, and the distribution of trophic link strengths in aquatic food webs crucially impacts their dynamics and stability. Although individual body size explains a large proportion of variation in trophic link strengths in aquatic habitats, current predominately body size-based views can gain additional realism by incorporating further traits. Functional traits that potentially affect the strength of trophic links can be classified into three groups: i body size, ii traits that identify the spatiotemporal overlap between the predators and their prey, and iii predator foraging and prey vulnerability traits, which are readily available for many taxa. Relationship between these trait groups and trophic link strength may be further modified by population densities, habitat complexity, temperature and other abiotic factors. I propose here that this broader multi-trait framework can utilize concepts, ideas and existing data from research on metabolic ecology, ecomorphology, animal personalities and role of habitats in community structuring. The framework can be used to investigate non-additive effects of traits on trophic interactions, shed more light on the structuring of local food webs and evaluate the merits of taxonomic and functional group approaches in the description of predator-prey interactions. Development of trait- and size-based descriptions of food webs could be particularly fruitful in limnology given the relative paucity of well resolved datasets in standing waters. 

  5. Congener-specific accumulation and trophic transfer of polychlorinated biphenyls in spider crab food webs revealed by stable isotope analysis

    Energy Technology Data Exchange (ETDEWEB)

    Bodin, N. [IFREMER, DCN-BE, Technopole Brest-Iroise, Pointe du Diable, 29280 Plouzane (France); LPTC-UMR 5472 CNRS, Universite de Bordeaux 1, 351 cours de la Liberation, 33400 Talence (France)], E-mail: bodin.nathalie@caramail.com; Le Loc' h, F. [IRD, UR 070 RAP, Centre de Recherche Halieutique, Avenue Jean Monnet, B.P. 171, 34203 Sete Cedex (France); Caisey, X.; Le Guellec, A.-M.; Abarnou, A.; Loizeau, V. [IFREMER, DCN-BE, Technopole Brest-Iroise, Pointe du Diable, 29280 Plouzane (France); Latrouite, D. [IFREMER, DCB-STH, Technopole Brest-Iroise, Pointe du Diable, 29280 Plouzane (France)

    2008-01-15

    Polychlorobiphenyls (PCB) and stable isotopes ({delta}{sup 15}N and {delta}{sup 13}C) were analyzed in the spider crab (Maja brachydactyla) food web from the Iroise Sea (Western Brittany) and the Seine Bay (Eastern English Channel). PCB concentrations were all significantly higher in organisms from the Seine Bay than those from the Iroise Sea. PCB patterns were strongly related to the feeding mode of the species, and increased influence of higher chlorinated congeners was highlighted with trophic position of the organisms. PCB concentrations (lipid normalized) were significantly related to the isotopically derived trophic level (TL) in spider crab food webs. The highest trophic magnification factors (TMFs) were calculated for the congeners with 2,4,5-substitution, and were lower in the Seine Bay compared to the Iroise Sea. The confrontation of PCB and TL data also revealed biotransformation capacity of decapod crustaceans for specific congeners based on structure-activity relations. - The influence of feeding mode and trophic position on the fate of PCBs in spider crab food webs is discussed by using a stable isotopic approach.

  6. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ (13)C and δ (15)N).

    Science.gov (United States)

    Stallings, Christopher D; Nelson, James A; Rozar, Katherine L; Adams, Charles S; Wall, Kara R; Switzer, Theodore S; Winner, Brent L; Hollander, David J

    2015-01-01

    Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ (13)C and δ (15)N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ (15)N values in nearly all comparisons. Ethanol also had strong effects on the δ (13)C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and

  7. Adaptive behaviour, tri-trophic food-web stability and damping of chaos

    DEFF Research Database (Denmark)

    Visser, Andre; Mariani, Patrizio; Pigolotti, Simone

    2012-01-01

    We examine the effect of adaptive foraging behaviour within a tri-trophic food web with intra-guild predation. The intra-guild prey is allowed to adjust its foraging effort so as to achieve an optimal per capita growth rate in the face of realized feeding, predation risk and foraging cost. Adapti...

  8. Trace element accumulation and trophic relationships in aquatic organisms of the Sundarbans mangrove ecosystem (Bangladesh)

    International Nuclear Information System (INIS)

    Borrell, Asunción; Tornero, Victoria; Bhattacharjee, Dola; Aguilar, Alex

    2016-01-01

    The Sundarbans forest is the largest and one of the most diverse and productive mangrove ecosystems in the world. Located at the northern shoreline of the Bay of Bengal in the Indian Ocean and straddling India and Bangladesh, the mangrove forest is the result of three primary river systems that originate further north and northwest. During recent decades, the Sundarbans have been subject to increasing pollution by trace elements caused by the progressive industrialization and urbanization of the basins of these three rivers. As a consequence, animals and plants dwelling downstream in the mangroves are exposed to these pollutants in varying degrees, and may potentially affect human health when consumed. The aim of the present study was to analyse the concentrations of seven trace elements (Zn, Cu, Cr, Hg, Pb, Cd and As) in 14 different animal and plant species collected in the Sundarbans in Bangladesh to study their transfer through the food web and to determine whether their levels in edible species are acceptable for human consumption. δ"1"5N values were used as a proxy of the trophic level. A decrease in Zn, Cu, Pb and Cd levels was observed with increasing trophic position. Trace element concentrations measured in all organisms were, in general, lower than the concentrations obtained in other field studies conducted in the same region. When examined with respect to accepted international standards, the concentrations observed in fish and crustaceans were generally found to be safe for human consumption. However, the levels of Zn in Scylla serrata and Cr and Cd in Harpadon nehereus exceeded the proposed health advisory levels and may be of concern for human health. - Highlights: • Trace elements were determined in organisms from the Sundarbans mangrove. • The levels found were similar to those determined in wildlife from other mangroves. • Levels in three edible species were close to threshold limits for human consumption. • Except for Cr, As and Hg

  9. Trace element accumulation and trophic relationships in aquatic organisms of the Sundarbans mangrove ecosystem (Bangladesh)

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, Asunción, E-mail: xonborrell@ub.edu [Department of Animal Biology, Institute of Biodiversity (IRBIO), University of Barcelona, Av. Diagonal, 643, Barcelona (Spain); Tornero, Victoria [Department of Animal Biology, Institute of Biodiversity (IRBIO), University of Barcelona, Av. Diagonal, 643, Barcelona (Spain); Bhattacharjee, Dola [Indian Institute of Science Education & Research — Kolkata, Department of Biological Sciences, Mohanpur Campus, Nadia, West Bengal (India); Aguilar, Alex [Department of Animal Biology, Institute of Biodiversity (IRBIO), University of Barcelona, Av. Diagonal, 643, Barcelona (Spain)

    2016-03-01

    The Sundarbans forest is the largest and one of the most diverse and productive mangrove ecosystems in the world. Located at the northern shoreline of the Bay of Bengal in the Indian Ocean and straddling India and Bangladesh, the mangrove forest is the result of three primary river systems that originate further north and northwest. During recent decades, the Sundarbans have been subject to increasing pollution by trace elements caused by the progressive industrialization and urbanization of the basins of these three rivers. As a consequence, animals and plants dwelling downstream in the mangroves are exposed to these pollutants in varying degrees, and may potentially affect human health when consumed. The aim of the present study was to analyse the concentrations of seven trace elements (Zn, Cu, Cr, Hg, Pb, Cd and As) in 14 different animal and plant species collected in the Sundarbans in Bangladesh to study their transfer through the food web and to determine whether their levels in edible species are acceptable for human consumption. δ{sup 15}N values were used as a proxy of the trophic level. A decrease in Zn, Cu, Pb and Cd levels was observed with increasing trophic position. Trace element concentrations measured in all organisms were, in general, lower than the concentrations obtained in other field studies conducted in the same region. When examined with respect to accepted international standards, the concentrations observed in fish and crustaceans were generally found to be safe for human consumption. However, the levels of Zn in Scylla serrata and Cr and Cd in Harpadon nehereus exceeded the proposed health advisory levels and may be of concern for human health. - Highlights: • Trace elements were determined in organisms from the Sundarbans mangrove. • The levels found were similar to those determined in wildlife from other mangroves. • Levels in three edible species were close to threshold limits for human consumption. • Except for Cr, As and Hg

  10. Platforms of the Nicaraguan Rise: Examples of the sensitivity of carbonate sedimentation to excess trophic resources

    Science.gov (United States)

    Hallock, Pamela; Hine, Albert C.; Vargo, Gabriel A.; Elrod, Jane A.; Jaap, Walter C.

    1988-12-01

    The Nicaraguan Rise is an active tectonic structure in the western Caribbean. Carbonate accumulation on its platforms has not kept pace with relative Holocene sea-level rise, despite a tropical location remote from terrigenous sedimentation. Trophic resources apparently exceed levels favoring coral-reef development because sponge-algal communities dominate the drowning western platforms, in contrast to mixed coral-algal benthos on Pedro Bank and well- developed coral reefs along the north coast of Jamaica. Concentrations of biotic pigments in sea-surface waters show a corresponding west-east gradient; oceanic waters flowing over the western banks carry nearly twice as much biotic pigment as oceanic waters north of Jamaica. Sources enriching the western Caribbean are terrestrial runoff, upwelling off northern South America, and topographic upwelling over the Nicaraguan Rise. That relatively modest levels of trophic resources can suppress coral-reef development holds important implications for understanding carbonate platform drownings in the geologic record.

  11. Spatially Explicit Modeling Reveals Cephalopod Distributions Match Contrasting Trophic Pathways in the Western Mediterranean Sea.

    Directory of Open Access Journals (Sweden)

    Patricia Puerta

    Full Text Available Populations of the same species can experience different responses to the environment throughout their distributional range as a result of spatial and temporal heterogeneity in habitat conditions. This highlights the importance of understanding the processes governing species distribution at local scales. However, research on species distribution often averages environmental covariates across large geographic areas, missing variability in population-environment interactions within geographically distinct regions. We used spatially explicit models to identify interactions between species and environmental, including chlorophyll a (Chla and sea surface temperature (SST, and trophic (prey density conditions, along with processes governing the distribution of two cephalopods with contrasting life-histories (octopus and squid across the western Mediterranean Sea. This approach is relevant for cephalopods, since their population dynamics are especially sensitive to variations in habitat conditions and rarely stable in abundance and location. The regional distributions of the two cephalopod species matched two different trophic pathways present in the western Mediterranean Sea, associated with the Gulf of Lion upwelling and the Ebro river discharges respectively. The effects of the studied environmental and trophic conditions were spatially variant in both species, with usually stronger effects along their distributional boundaries. We identify areas where prey availability limited the abundance of cephalopod populations as well as contrasting effects of temperature in the warmest regions. Despite distributional patterns matching productive areas, a general negative effect of Chla on cephalopod densities suggests that competition pressure is common in the study area. Additionally, results highlight the importance of trophic interactions, beyond other common environmental factors, in shaping the distribution of cephalopod populations. Our study presents

  12. Trophic dynamics of a simple model ecosystem.

    Science.gov (United States)

    Bell, Graham; Fortier-Dubois, Étienne

    2017-09-13

    We have constructed a model of community dynamics that is simple enough to enumerate all possible food webs, yet complex enough to represent a wide range of ecological processes. We use the transition matrix to predict the outcome of succession and then investigate how the transition probabilities are governed by resource supply and immigration. Low-input regimes lead to simple communities whereas trophically complex communities develop when there is an adequate supply of both resources and immigrants. Our interpretation of trophic dynamics in complex communities hinges on a new principle of mutual replenishment, defined as the reciprocal alternation of state in a pair of communities linked by the invasion and extinction of a shared species. Such neutral couples are the outcome of succession under local dispersal and imply that food webs will often be made up of suites of trophically equivalent species. When immigrants arrive from an external pool of fixed composition a similar principle predicts a dynamic core of webs constituting a neutral interchange network, although communities may express an extensive range of other webs whose membership is only in part predictable. The food web is not in general predictable from whole-community properties such as productivity or stability, although it may profoundly influence these properties. © 2017 The Author(s).

  13. Linking cascading effects of fish predation and zooplankton grazing to reduced cyanobacterial biomass and toxin levels following biomanipulation.

    Directory of Open Access Journals (Sweden)

    Mattias K Ekvall

    Full Text Available Eutrophication has been one of the largest environmental problems in aquatic ecosystems during the past decades, leading to dense, and often toxic, cyanobacterial blooms. In a way to counteract these problems many lakes have been subject to restoration through biomanipulation. Here we combine 13 years of monitoring data with experimental assessment of grazing efficiency of a naturally occurring zooplankton community and a, from a human perspective, desired community of large Daphnia to assess the effects of an altered trophic cascade associated with biomanipulation. Lake monitoring data show that the relative proportion of Daphnia spp. grazers in June has increased following years of biomanipulation and that this increase coincides with a drop in cyanobacterial biomass and lowered microcystin concentrations compared to before the biomanipulation. In June, the proportion of Daphnia spp. (on a biomass basis went from around 3% in 2005 (the first year of biomanipulation up to around 58% in 2012. During months when the proportion of Daphnia spp. remained unchanged (July and August no effect on lower trophic levels was observed. Our field grazing experiment revealed that Daphnia were more efficient in controlling the standing biomass of cyanobacteria, as grazing by the natural zooplankton community never even compensated for the algal growth during the experiment and sometimes even promoted cyanobacterial growth. Furthermore, although the total cyanobacterial toxin levels remained unaffected by both grazer communities in the experimental study, the Daphnia dominated community promoted the transfer of toxins to the extracellular, dissolved phase, likely through feeding on cyanobacteria. Our results show that biomanipulation by fish removal is a useful tool for lake management, leading to a top-down mediated trophic cascade, through alterations in the grazer community, to reduced cyanobacterial biomass and lowered cyanobacterial toxin levels. This

  14. Ekologi Trofik Komunitas Ikan di Perairan Segara Menyan, Subang, Jawa Barat (Trophic Ecology of the Fish Community in Segara Menyan Coastal Lagoon, Subang, West Java

    Directory of Open Access Journals (Sweden)

    Ahmad Zahid

    2015-09-01

    Full Text Available Pengetahuan mengenai ekologi trofik merupakan dasar dalam memahami ekosistem secara keseluruhan yang dapat dijelaskan melalui pola hubungan trofik interspesies ataupun interserikat. Penelitian bertujuan untuk menjelaskan ekologi trofik meliputi indeks trofik dan jenis makanan dominan, serikat dan tingkat trofik, dan variasi spasial dan temporal komunitas ikan di estuari Segara Menyan. Pengambilan ikan contoh dilakukan setiap bulan pada zona berbeda. Ikan contoh dipisahkan berdasarkan waktu dan lokasi pengamatan, dianalisis isi saluran pencernaannya. Analisa data meliputi indeks vakuitas, jumlah total organisme makanan, jenis makanan dominan, luas relung makanan, dan tingkat trofik.  Pada pengamatan 106 spesies ikan, sebanyak 1-380 saluran pencernaan ikan diamati. Sebanyak lima dari 106 spesies memiliki nilai indeks vakuitas “0” dan jumlah makanan yang dikonsumsi bervariasi mulai dari empat hingga 27 jenis makanan. Secara umum, luas relung ikan adalah rendah berkisar 0,20-0,78 dan kebanyakan berada pada kisaran 0,20-0,48. Zooplankton merupakan jenis makanan paling dominan dikonsumsi oleh ikan. Komunitas ikan dikelompokkan dalam tujuh serikat trofik, yaitu detritivora, fitoplanktivora, zooplanktivora, zoobentivora, moluskivora, krustasivora, dan pisivora. Tingkat trofik komunitas ikan berkisar 2,05-4,73. Faktor perubahan ontogenetik, persediaan makanan, karakteristik habitat, dan ruaya beberapa spesies ikan memengaruhi variasi spasio-temporal jejaring makanan di Segara Menyan. Kata kunci: interaksi trofik, laguna, ikan, variasi spasio-temporal, serikat trofik Knowledge of trophic ecology is one way to understanding the whole ecosystem which explained by trophic relationship pattern (interspecies or interguild. The objective research was described of the trophic ecology, i.e. trophic index and dominant prey, trophic guild and trophic level, and spatio-temporal variation of fish community in Segara Menyan coastal lagoon. Fish were collected

  15. Trophic diversity in the evolution and community assembly of loricariid catfishes

    Directory of Open Access Journals (Sweden)

    Lujan Nathan K

    2012-07-01

    Full Text Available Abstract Background The Neotropical catfish family Loricariidae contains over 830 species that display extraordinary variation in jaw morphologies but nonetheless reveal little interspecific variation from a generalized diet of detritus and algae. To investigate this paradox, we collected δ13C and δ15N stable isotope signatures from 649 specimens representing 32 loricariid genera and 82 species from 19 local assemblages distributed across South America. We calculated vectors representing the distance and direction of each specimen relative to the δ15N/δ13C centroid for its local assemblage, and then examined the evolutionary diversification of loricariids across assemblage isotope niche space by regressing the mean vector for each genus in each assemblage onto a phylogeny reconstructed from osteological characters. Results Loricariids displayed a total range of δ15N assemblage centroid deviation spanning 4.9‰, which is within the tissue–diet discrimination range known for Loricariidae, indicating that they feed at a similar trophic level and that δ15N largely reflects differences in their dietary protein content. Total range of δ13C deviation spanned 7.4‰, which is less than the minimum range reported for neotropical river fish communities, suggesting that loricariids selectively assimilate a restricted subset of the full basal resource spectrum available to fishes. Phylogenetic regression of assemblage centroid-standardized vectors for δ15N and δ13C revealed that loricariid genera with allopatric distributions in disjunct river basins partition basal resources in an evolutionarily conserved manner concordant with patterns of jaw morphological specialization and with evolutionary diversification via ecological radiation. Conclusions Trophic partitioning along elemental/nutritional gradients may provide an important mechanism of dietary segregation and evolutionary diversification among loricariids and perhaps other taxonomic

  16. Taxonomic composition and trophic structure of the continental bony fish assemblage from the early late cretaceous of Southeastern Morocco.

    Science.gov (United States)

    Cavin, Lionel; Boudad, Larbi; Tong, Haiyan; Läng, Emilie; Tabouelle, Jérôme; Vullo, Romain

    2015-01-01

    The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to 'Stromerichthys' from coeval deposits in Egypt. The ginglymodians were diversified with a large 'Lepidotes' plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

  17. Trigeminal trophic syndrome

    Directory of Open Access Journals (Sweden)

    Parimalam Kumar

    2014-01-01

    Full Text Available Trigeminal trophic syndrome (TTS is a rare cause of facial ulceration, consequent to damage to the trigeminal nerve or its central sensory connections. We reporta case of TTS in a 48-year-old woman with Bell′s palsy following herpes zoster infection. The patient was treated and counseled. There hasnot been any recurrence for 1 year and the patient is being followed-up. The diagnosis of TTS should be suspected when there is unilateral facial ulceration, especially involving the ala nasi associated with sensory impairment.

  18. Sensitivity of secondary production and export flux to choice of trophic transfer formulation in marine ecosystem models

    Science.gov (United States)

    Anderson, Thomas R.; Hessen, Dag O.; Mitra, Aditee; Mayor, Daniel J.; Yool, Andrew

    2013-09-01

    The performance of four contemporary formulations describing trophic transfer, which have strongly contrasting assumptions as regards the way that consumer growth is calculated as a function of food C:N ratio and in the fate of non-limiting substrates, was compared in two settings: a simple steady-state ecosystem model and a 3D biogeochemical general circulation model. Considerable variation was seen in predictions for primary production, transfer to higher trophic levels and export to the ocean interior. The physiological basis of the various assumptions underpinning the chosen formulations is open to question. Assumptions include Liebig-style limitation of growth, strict homeostasis in zooplankton biomass, and whether excess C and N are released by voiding in faecal pellets or via respiration/excretion post-absorption by the gut. Deciding upon the most appropriate means of formulating trophic transfer is not straightforward because, despite advances in ecological stoichiometry, the physiological mechanisms underlying these phenomena remain incompletely understood. Nevertheless, worrying inconsistencies are evident in the way in which fundamental transfer processes are justified and parameterised in the current generation of marine ecosystem models, manifested in the resulting simulations of ocean biogeochemistry. Our work highlights the need for modellers to revisit and appraise the equations and parameter values used to describe trophic transfer in marine ecosystem models.

  19. Measuring variability in trophic status in the Lake Waco/Bosque River Watershed

    Directory of Open Access Journals (Sweden)

    Rodriguez Angela D

    2008-01-01

    Full Text Available Abstract Background Nutrient management in rivers and streams is difficult due to the spatial and temporal variability of algal growth responses. The objectives of this project were to determine the spatial and seasonal in situ variability of trophic status in the Lake Waco/Bosque River watershed, determine the variability in the lotic ecosystem trophic status index (LETSI at each site as indicators of the system's nutrient sensitivity, and determine if passive diffusion periphytometers could provide threshold algal responses to nutrient enrichment. Methods We used the passive diffusion periphytometer to measure in-situ nutrient limitation and trophic status at eight sites in five streams in the Lake Waco/Bosque River Watershed in north-central Texas from July 1997 through October 1998. The chlorophyll a production in the periphytometers was used as an indicator of baseline chlorophyll a productivity and of maximum primary productivity (MPP in response to nutrient enrichment (nitrogen and phosphorus. We evaluated the lotic ecosystem trophic status index (LETSI using the ratio of baseline primary productivity to MPP, and evaluated the trophic class of each site. Results The rivers and streams in the Lake Waco/Bosque River Watershed exhibited varying degrees of nutrient enrichment over the 18-month sampling period. The North Bosque River at the headwaters (NB-02 located below the Stephenville, Texas wastewater treatment outfall consistently exhibited the highest degree of water quality impact due to nutrient enrichment. Sites at the outlet of the watershed (NB-04 and NB-05 were the next most enriched sites. Trophic class varied for enriched sites over seasons. Conclusion Seasonality played a significant role in the trophic class and sensitivity of each site to nutrients. Managing rivers and streams for nutrients will require methods for measuring in situ responses and sensitivities to nutrient enrichment. Nutrient enrichment periphytometers show

  20. Willow on Yellowstone's northern range: evidence for a trophic cascade?

    Science.gov (United States)

    Beyer, Hawthorne L; Merrill, Evelyn H; Varley, Nathan; Boyce, Mark S

    2007-09-01

    Reintroduction of wolves (Canis lupus) to Yellowstone National Park in 1995-1996 has been argued to promote a trophic cascade by altering elk (Cervus elaphus) density, habitat-selection patterns, and behavior that, in turn, could lead to changes within the plant communities used by elk. We sampled two species of willow (Salix boothii and S. geyeriana) on the northern winter range to determine whether (1) there was quantitative evidence of increased willow growth following wolf reintroduction, (2) browsing by elk affected willow growth, and (3) any increase in growth observed was greater than that expected by climatic and hydrological factors alone, thereby indicating a trophic cascade caused by wolves. Using stem sectioning techniques to quantify historical growth patterns we found an approximately twofold increase in stem growth-ring area following wolf reintroduction for both species of willow. This increase could not be explained by climate and hydrological factors alone; the presence of wolves on the landscape was a significant predictor of stem growth above and beyond these abiotic factors. Growth-ring area was positively correlated with the previous year's ring area and negatively correlated with the percentage of twigs browsed from the stem during the winter preceding growth, indicating that elk browse impeded stem growth. Our results are consistent with the hypothesis of a behaviorally mediated trophic cascade on Yellowstone's northern winter range following wolf reintroduction. We suggest that the community-altering effects of wolf restoration are an endorsement of ecological-process management in Yellowstone National Park.

  1. Mapping of trophic states based on nutrients concentration and phytoplankton abundance in Jatibarang Reservoir

    Science.gov (United States)

    Rudiyanti, Siti; Anggoro, Sutrisno; Rahman, Arif

    2018-02-01

    Jatibarang Reservoir is one of the Indonesian Reservoirs, which used for human activities such as tourism and agriculture. These activities will provide input of organic matter and nutrients into the water. These materials will impact water quality and eutrophication process. Eutrophication is the water enrichment by nutrients, especially nitrogen and phosphorus which can promote the growth of phytoplankton. Some indicators of eutrophication are increasing nutrients, trophic states, and change of phytoplankton composition. The relationship between water quality and phytoplankton community can be used as an indicator of trophic states in Jatibarang Reservoir. The aim of this study was to analyze the effect of nutrients concentration and phytoplankton abundance to the trophic states and mapping trophic states based on nutrients concentration and phytoplankton in Jatibarang Reservoir. This study was conducted in June and July 2017 at 9 stations around Jatibarang Reservoir. The results showed that average concentration of nitrate, phosphate, and chlorophyll-a in Jatibarang Reservoir was 0.69 mg/L, 0.27 mg/L, and 1.66 mg/m3, respectively. The phytoplankton abundance ranged 16-62,200 cells/L, consists of 21 genera of four classes, i.e. Chlorophyceae, Cyanophyceae, Bacillariophyceae, and Dinophyceae. Cyanophyceae was a dominant phytoplankton group based on the composition of abundance (>80%). High nutrient concentrations and phytoplankton dominated by Anabaena (Cyanophyceae) which indicated that the waters in Jatibarang Reservoir were eutrophic.

  2. Drivers of trophic amplification of ocean productivity trends in a changing climate

    OpenAIRE

    C. A. Stock; J. P. Dunne; J. G. John

    2014-01-01

    Pronounced projected 21st century trends in regional oceanic net primary production (NPP) raise the prospect of significant redistributions of marine resources. Recent results further suggest that NPP changes may be amplified at higher trophic levels. Here, we elucidate the role of planktonic food web dynamics in driving projected changes in mesozooplankton production (MESOZP) found to be, on average, twice as large as projected changes in...

  3. Weak trophic links between a crab-spider and the effective pollinators of a rewardless orchid

    Science.gov (United States)

    Quintero, Carolina; Corley, Juan C.; Aizen, Marcelo A.

    2015-01-01

    Sit and wait predators hunting on flowers are considered to be exploiters of plant-pollinator mutualisms. Several studies have shown that plant-pollinator interactions can be highly susceptible to the impact of a third trophic level, via consumptive (direct) and non-consumptive (indirect) effects that alter pollinator behavior and, ultimately, plant fitness. However, most flowering plants attract a wide array of flower visitors, from which only a subset will be effective pollinators. Hence, a negative effect of an ambush predator on plant fitness should be expected only when: (i) the effective pollinators are part of the predators' diet and/or (ii) the non-consumptive effects of predator presence (e.g. dead prey) alter the behavior of effective pollinators and pollen movement among individual plants. We analyzed the direct and indirect effects of a crab-spider (Misumenops pallidus), on the pollination and reproductive success of Chloraea alpina, a Patagonian rewardless orchid. Our results indicate that most of the flower visitors do not behave as effective pollinators and most effective pollinators were not observed as prey for the crab-spider. In terms of non-consumptive effects, inflorescences with and without spiders and/or dead-prey did not vary the frequency of flower visitors, nor pollinia removal or deposition. Hence, it is not surprising that M. pallidus has a neutral effect on pollinia removal and deposition as well as on fruit and seed set. Similar to other rewardless orchids, the low reproductive success of C. alpina (∼6% fruit set) was associated with the limited number of visits by effective pollinators. Negative top-down effects of a flower-visitor predator on plant pollination may not be anticipated without studying the direct and indirect effects of this predator on the effective pollinators. In pollination systems where effective pollinators visited flowers erratically, such as in deceptive orchids, we expect weak or no effect of predators on

  4. Ecological impact of transhumance on the trophic state of alpine lakes in Gran Paradiso National Park

    Directory of Open Access Journals (Sweden)

    Tiberti R.

    2014-01-01

    Full Text Available Transhumance – the summer transfer of livestock to highland pastures – is a traditional practice in the European Alps and is considered an integral part of the mountain ecosystem. Mountain lakes are generally oligotrophic systems and are particularly sensitive to the nutrient input caused by livestock. The aim of the present study was to quantify the impact of livestock grazing on the trophic state of high-altitude lakes in an area where transhumance is a traditional practice (Gran Paradiso National Park, Western Italian Alps, taking into account its dual value of ecosystem component and potential threat to lakes’ trophic status. The impact of flocks and herds grazing was estimated on sensitive parameters related to the trophic state of alpine lakes: water transparency, nutrient content, bacterial load and chlorophyll-a concentration. Transhumance produced a significant increase in the trophic state of lakes with high grazing pressure, but little or no effect was found at soft-impacted lakes. Even though heavy-impacted lakes represent a minority of the studied lakes (three out of twenty, we indicated conservation measures such as fencing, wastewater treatment and livestock exclosure to be tested in Gran Paradiso National Park.

  5. Exploring trophic strategies of exotic caprellids (Crustacea: Amphipoda): Comparison between habitat types and native vs introduced distribution ranges

    Science.gov (United States)

    Ros, Macarena; Tierno de Figueroa, José Manuel; Guerra-García, José Manuel; Navarro-Barranco, Carlos; Lacerda, Mariana Baptista; Vázquez-Luis, Maite; Masunari, Setuko

    2014-02-01

    The trophic ecology of non-native species is a key aspect to understand their invasion success and the community effects. Despite the important role of caprellid amphipods as trophic intermediates between primary producers and higher levels of marine food webs, there is very little information on their feeding habits. This is the first comprehensive study on the trophic strategies of two co-occurring introduced caprellids in the Spanish coasts: Caprella scaura and Paracaprella pusilla. The diet of 446 specimens of C. scaura and 230 of P. pusilla was analyzed to investigate whether there were differences in the feeding habits in relation to habitat characteristics (natural vs artificial hard substrata), type of host substrata (bryozoans and hydroids) and native vs introduced distribution ranges (Brazil vs Spain). Results revealed differences in diet preferences of the two species that have important implications for their trophic behaviour and showed a limited food overlap, which may favour their coexistence in introduced areas. In general terms, P. pusilla is a predator species, showing preference by crustacean prey in all of its life stages, while C. scaura feeds mainly on detritus. Although no sex-related diet shifts were observed in either of the species, evidence of ontogenetic variation in diet of C. scaura was found, with juveniles feeding on more amount of prey than adults. No diet differences were found between native and introduced populations within the same habitat type. However, P. pusilla exhibited a shift in its diet when different habitats were compared in the same distribution area, and C. scaura showed a flexible feeding behaviour between different host substrata in the same habitat type. This study shows that habitat characteristics at different scales can have greater influence on the feeding ecology of exotic species than different distribution ranges, and support the hypothesis that a switch between feeding strategies depending on habitat

  6. Predicting the effects of climate change on trophic status of three morphologically varying lakes: Implications for lake restoration and management

    DEFF Research Database (Denmark)

    Trolle, Dennis; Hamilton, David P.; Pilditch, Conrad A.

    2011-01-01

    To quantify the effects of a future climate on three morphologically different lakes that varied in trophic status from oligo-mesotrophic to highly eutrophic, we applied the one-dimensional lake ecosystem model DYRESM-CAEDYM to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu, both in the t....... Therefore, future climate effects should be taken into account in the long-term planning and implementation of lake management as strategies may need to be refined and adapted to preserve or improve the present-day lake water quality....

  7. Modelling emergent trophic strategies in plankton

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Aksnes, Dag L.; Berge, Terje

    2015-01-01

    Plankton are typically divided into phytoplankton and zooplankton in marine ecosystem models. Yet, most protists in the photic zone engage in some degree of phagotrophy, and it has been suggested that trophic strategy is really a continuum between pure phototrophs (phytoplankton) and pure...

  8. Mercury cycling in stream ecosystems. 3. Trophic dynamics and methylmercury bioaccumulation

    Science.gov (United States)

    Chasar, L.C.; Scudder, B.C.; Stewart, A.R.; Bell, A.H.; Aiken, G.R.

    2009-01-01

    Trophic dynamics (community composition and feeding relationships) have been identified as important drivers of methylmercury (MeHg) bioaccumulation in lakes, reservoirs, and marine ecosystems. The relative importance of trophic dynamics and geochemical controls on MeHg bioaccumulation in streams, however, remains poorly characterized. MeHg bioaccumulation was evaluated in eight stream ecosystems across the United States (Oregon, Wisconsin, and Florida) spanning large ranges in climate, landscape characteristics, atmospheric Hg deposition, and stream chemistry. Across all geographic regions and all streams, concentrations of total Hg (THg) in top predator fish and forage fish, and MeHg in invertebrates, were strongly positively correlated to concentrations of filtered THg (FTHg), filtered MeHg (FMeHg), and dissolved organic carbon (DOC); to DOC complexity (as measured by specific ultraviolet absorbance); and to percent wetland in the stream basins. Correlations were strongest for nonurban streams. Although regressions of log[Hg] versus ??15N indicate that Hg in biota increased significantly with increasing trophic position within seven of eight individual streams, Hg concentrations in top predator fish (including cutthroat, rainbow, and brown trout; green sunfish; and largemouth bass) were not strongly influenced by differences in relative trophic position. Slopes of log[Hg] versus ??15N, an indicator of the efficiency of trophic enrichment, ranged from 0.14 to 0.27 for all streams. These data suggest that, across the large ranges in FTHg (0.14-14.2 ng L-1), FMeHg (0.023-1.03 ng L-1), and DOC (0.50-61.0 mg L-1) found in this study, Hg contamination in top predator fish in streams likely is dominated by the amount of MeHg available for uptake at the base of the food web rather than by differences in the trophic position of top predator fish. ?? 2009 American Chemical Society.

  9. Trophic facilitation or limitation? Comparative effects of pumas and black bears on the scavenger community.

    Directory of Open Access Journals (Sweden)

    Maximilian L Allen

    Full Text Available Scavenging is a widespread behaviour and an important process influencing food webs and ecological communities. Large carnivores facilitate the movement of energy across trophic levels through the scavenging and decomposition of their killed prey, but competition with large carnivores is also likely to constrain acquisition of carrion by scavengers. We used an experimental approach based on motion-triggered video cameras at black-tailed deer (Odocoileus hemionus columbianus carcasses to measure the comparative influences of two large carnivores in the facilitation and limitation of carrion acquisition by scavengers. We found that pumas (Puma concolor and black bears (Ursus americanus had different effects on their ecological communities. Pumas, as a top-level predator, facilitated the consumption of carrion by scavengers, despite significantly reducing their observed sum feeding times (165.7 min ± 21.2 SE at puma kills 264.3 min ± 30.1 SE at control carcasses. In contrast, black bears, as the dominant scavenger in the system, limited consumption of carrion by scavengers as evidenced by the observed reduction of scavenger species richness recorded at carcasses where they were present (mean = 2.33 ± 0.28 SE, compared to where they were absent (mean = 3.28 ± 0.23 SE. Black bears also had large negative effects on scavenger sum feeding times (88.5 min ± 19.8 SE at carcasses where bears were present, 372.3 min ± 50.0 SE at carcasses where bears were absent. In addition, we found that pumas and black bears both increased the nestedness (a higher level of order among species present of the scavenger community. Our results suggest that scavengers have species-specific adaptions to exploit carrion despite large carnivores, and that large carnivores influence the structure and composition of scavenger communities. The interactions between large carnivores and scavengers should be considered in future studies of food webs and ecological communities.

  10. Ammonium Transformation in 14 Lakes along a Trophic Gradient

    Directory of Open Access Journals (Sweden)

    Barbara Leoni

    2018-03-01

    Full Text Available Ammonia is a widespread pollutant in aquatic ecosystems originating directly and indirectly from human activities, which can strongly affect the structure and functioning of the aquatic foodweb. The biological oxidation of NH4+ to nitrite, and then nitrate is a key part of the complex nitrogen cycle and a fundamental process in aquatic environments, having a profound influence on ecosystem stability and functionality. Environmental studies have shown that our current knowledge of physical and chemical factors that control this process and the abundance and function of involved microorganisms are not entirely understood. In this paper, the efficiency and the transformation velocity of ammonium into oxidised compounds in 14 south-alpine lakes in northern Italy, with a similar origin, but different trophic levels, are compared with lab-scale experimentations (20 °C, dark, oxygen saturation that are performed in artificial microcosms (4 L. The water samples were collected in different months to highlight the possible effect of seasonality on the development of the ammonium oxidation process. In four-liter microcosms, concentrations were increased by 1 mg/L NH4+ and the process of ammonium oxidation was constantly monitored. The time elapsed for the decrease of 25% and 95% of the initial ion ammonium concentration and the rate for that ammonium oxidation were evaluated. Principal Component Analysis and General Linear Model, performed on 56 observations and several chemical and physical parameters, highlighted the important roles of total phosphorus and nitrogen concentrations on the commencement of the oxidation process. Meanwhile, the natural concentration of ammonium influenced the rate of nitrification (µg NH4+/L day. Seasonality did not seem to significantly affect the ammonium transformation. The results highlight the different vulnerabilities of lakes with different trophic statuses.

  11. Echinoderms display morphological and behavioural phenotypic plasticity in response to their trophic environment.

    Directory of Open Access Journals (Sweden)

    Adam D Hughes

    Full Text Available The trophic interactions of sea urchins are known to be the agents of phase shifts in benthic marine habitats such as tropical and temperate reefs. In temperate reefs, the grazing activity of sea urchins has been responsible for the destruction of kelp forests and the formation of 'urchin barrens', a rocky habitat dominated by crustose algae and encrusting invertebrates. Once formed, these urchin barrens can persist for decades. Trophic plasticity in the sea urchin may contribute to the stability and resilience of this alternate stable state by increasing diet breadth in sea urchins. This plasticity promotes ecological connectivity and weakens species interactions and so increases ecosystem stability. We test the hypothesis that sea urchins exhibit trophic plasticity using an approach that controls for other typically confounding environmental and genetic factors. To do this, we exposed a genetically homogenous population of sea urchins to two very different trophic environments over a period of two years. The sea urchins exhibited a wide degree of phenotypic trophic plasticity when exposed to contrasting trophic environments. The two populations developed differences in their gross morphology and the test microstructure. In addition, when challenged with unfamiliar prey, the response of each group was different. We show that sea urchins exhibit significant morphological and behavioural phenotypic plasticity independent of their environment or their nutritional status.

  12. Trophic ecomorphology of Siluriformes (Pisces, Osteichthyes) from a tropical stream.

    Science.gov (United States)

    Pagotto, J P A; Goulart, E; Oliveira, E F; Yamamura, C B

    2011-05-01

    The present study analysed the relationship between morphology and trophic structure of Siluriformes (Pisces, Osteichthyes) from the Caracu Stream (22º 45' S and 53º 15' W), a tributary of the Paraná River (Brazil). Sampling was carried out at three sites using electrofishing, and two species of Loricariidae and four of Heptapteridae were obtained. A cluster analysis revealed the presence of three trophic guilds (detritivores, insectivores and omnivores). Principal components analysis demonstrated the segregation of two ecomorphotypes: at one extreme there were the detritivores (Loricariidae) with morphological structures that are fundamental in allowing them to fix themselves to substrates characterised by rushing torrents, thus permitting them to graze on the detritus and organic materials encrusted on the substrate; at the other extreme of the gradient there were the insectivores and omnivores (Heptapteridae), with morphological characteristics that promote superior performance in the exploitation of structurally complex habitats with low current velocity, colonised by insects and plants. Canonical discriminant analysis revealed an ecomorphological divergence between insectivores, which have morphological structures that permit them to capture prey in small spaces among rocks, and omnivores, which have a more compressed body and tend to explore food items deposited in marginal backwater zones. Mantel tests showed that trophic structure was significantly related to the body shape of a species, independently of the phylogenetic history, indicating that, in this case, there was an ecomorphotype for each trophic guild. Therefore, the present study demonstrated that the Siluriformes of the Caracu Stream were ecomorphologically structured and that morphology can be applied as an additional tool in predicting the trophic structure of this group.

  13. Trophic ecomorphology of Siluriformes (Pisces, Osteichthyes from a tropical stream

    Directory of Open Access Journals (Sweden)

    JPA Pagotto

    Full Text Available The present study analysed the relationship between morphology and trophic structure of Siluriformes (Pisces, Osteichthyes from the Caracu Stream (22º 45' S and 53º 15' W, a tributary of the Paraná River (Brazil. Sampling was carried out at three sites using electrofishing, and two species of Loricariidae and four of Heptapteridae were obtained. A cluster analysis revealed the presence of three trophic guilds (detritivores, insectivores and omnivores. Principal components analysis demonstrated the segregation of two ecomorphotypes: at one extreme there were the detritivores (Loricariidae with morphological structures that are fundamental in allowing them to fix themselves to substrates characterised by rushing torrents, thus permitting them to graze on the detritus and organic materials encrusted on the substrate; at the other extreme of the gradient there were the insectivores and omnivores (Heptapteridae, with morphological characteristics that promote superior performance in the exploitation of structurally complex habitats with low current velocity, colonised by insects and plants. Canonical discriminant analysis revealed an ecomorphological divergence between insectivores, which have morphological structures that permit them to capture prey in small spaces among rocks, and omnivores, which have a more compressed body and tend to explore food items deposited in marginal backwater zones. Mantel tests showed that trophic structure was significantly related to the body shape of a species, independently of the phylogenetic history, indicating that, in this case, there was an ecomorphotype for each trophic guild. Therefore, the present study demonstrated that the Siluriformes of the Caracu Stream were ecomorphologically structured and that morphology can be applied as an additional tool in predicting the trophic structure of this group.

  14. Mercury bioaccumulation in cartilaginous fishes from Southern New England coastal waters: Contamination from a trophic ecology and human health perspective

    Science.gov (United States)

    Taylor, David L.; Kutil, Nicholas J.; Malek, Anna J.; Collie, Jeremy S.

    2014-01-01

    This study examined total mercury (Hg) concentrations in cartilaginous fishes from Southern New England coastal waters, including smooth dogfish (Mustelus canis), spiny dogfish (Squalus acanthias), little skate (Leucoraja erinacea), and winter skate (L. ocellata). Total Hg in dogfish and skates were positively related to their respective body size and age, indicating Hg bioaccumulation in muscle tissue. There were also significant inter-species differences in Hg levels (mean ± 1 SD, mg Hg/kg dry weight, ppm): smooth dogfish (3.3 ± 2.1 ppm; n = 54) > spiny dogfish (1.1 ± 0.7 ppm; n = 124) > little skate (0.4 ± 0.3 ppm; n = 173) ~ winter skate (0.3 ± 0.2 ppm; n = 148). The increased Hg content of smooth dogfish was attributed to its upper trophic level status, determined by stable nitrogen (δ15N) isotope analysis (mean δ15N = 13.2 ± 0.7‰), and the consumption of high Hg prey, most notably cancer crabs (0.10 ppm). Spiny dogfish had depleted δ15N signatures (11.6 ± 0.8‰), yet demonstrated a moderate level of contamination by foraging on pelagic prey with a range of Hg concentrations, e.g., in order of dietary importance, butterfish (Hg = 0.06 ppm), longfin squid (0.17 ppm), and scup (0.11 ppm). Skates were low trophic level consumers (δ15N = 11.9-12.0‰) and fed mainly on amphipods, small decapods, and polychaetes with low Hg concentrations (0.05-0.09 ppm). Intra-specific Hg concentrations were directly related to δ15N and carbon (δ13C) isotope signatures, suggesting that Hg biomagnifies across successive trophic levels and foraging in the benthic trophic pathway increases Hg exposure. From a human health perspective, 87% of smooth dogfish, 32% of spiny dogfish, and < 2% of skates had Hg concentrations exceeding the US Environmental Protection Agency threshold level (0.3 ppm wet weight). These results indicate that frequent consumption of smooth dogfish and spiny dogfish may adversely affect human health, whereas skates present minimal risk. PMID

  15. Trophic factors as modulators of motor neuron physiology and survival: implications for ALS therapy

    Directory of Open Access Journals (Sweden)

    Luis B Tovar-y-Romo

    2014-02-01

    Full Text Available Motor neuron physiology and development depend on a continuous and tightly regulated trophic support from a variety of cellular sources. Trophic factors guide the generation and positioning of motor neurons during every stage of the developmental process. As well, they are involved in axon guidance and synapse formation. Even in the adult spinal cord an uninterrupted trophic input is required to maintain neuronal functioning and protection from noxious stimuli. Among the trophic factors that have been demonstrated to participate in motor neuron physiology are vascular endothelial growth factor (VEGF, glial-derived neurotrophic factor (GDNF, ciliary neurotrophic factor (CNTF and insulin-like growth factor 1 (IGF-1. Upon binding to membrane receptors expressed in motor neurons or neighboring glia, these trophic factors activate intracellular signaling pathways that promote cell survival and have protective action on motor neurons, in both in vivo and in vitro models of neuronal degeneration. For these reasons these factors have been considered a promising therapeutic method for amyotrophic lateral sclerosis (ALS and other neurodegenerative diseases, although their efficacy in human clinical trials have not yet shown the expected protection. In this review we summarize experimental data on the role of these trophic factors in motor neuron function and survival, as well as their mechanisms of action. We also briefly discuss the potential therapeutic use of the trophic factors and why these therapies may have not been yet successful in the clinical use.

  16. Diet and trophic groups of an aquatic insect community in a tropical stream

    Directory of Open Access Journals (Sweden)

    R. L. Motta

    Full Text Available The diet and trophic groups of an assemblage of aquatic insects were studied in a tropical stream. Genera of the orders Ephemeroptera, Odonata, Plecoptera, Lepidoptera, and Hemiptera showed feeding specialization. Others, such as Trichoptera, Coleoptera, and Diptera, showed great diet variation with genera of different trophic groups. Seasonal variation of insect diet, evident only for some genera of the orders Trichoptera, Lepidoptera, Coleoptera, and Diptera, was due to the differences observed in community composition and to generalist habits of these genera. However, the seasonal comparison of trophic groups showed no significant statistical differences. The great importance of organic matter, a non-limited resource, in the diet of Ribeirão do Atalho aquatic insects may be the explanation for the trophic stability in this community organization.

  17. Marine snow, zooplankton and thin layers: indications of a trophic link from small-scale sampling with the Video Plankton Recorder

    DEFF Research Database (Denmark)

    Möller, Klas O.; St. John, Michael; Temming, Axel

    2012-01-01

    Marine aggregates of biogenic origin, known as marine snow, are considered to play a major role in the ocean’s particle flux and may represent a concentrated food source for zooplankton. However, observing the marine snow−zooplankton interaction in the field is difficult since conventional net sa...... to aggregates and demonstrating feeding behaviour, which also suggests a trophic interaction. Our observations highlight the potential significance of marine snow in marine ecosystems and its potential as a food resource for various trophic levels, from bacteria up to fish...

  18. Invasive plant architecture alters trophic interactions by changing predator abundance and behavior

    Science.gov (United States)

    Dean E. Pearson

    2009-01-01

    As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa...

  19. Stable isotopes document the trophic structure of a deep-sea cephalopod assemblage including giant octopod and giant squid.

    Science.gov (United States)

    Cherel, Y; Ridoux, V; Spitz, J; Richard, P

    2009-06-23

    Although deep-sea cephalopods are key marine organims, their feeding ecology remains essentially unknown. Here, we report for the first time the trophic structure of an assemblage of these animals (19 species) by measuring the isotopic signature of wings of their lower beaks, which accumulated in stomachs of stranded sperm whales. Overall, the species encompassed a narrow range in delta(13)C values (1.7 per thousand), indicating that they lived in closely related and overlapping habitats. delta(13)C values can be interpreted in terms of distribution with the more (13)C-depleted species (e.g. Stigmatoteuthis arcturi, Vampyroteuthis infernalis) having a more pelagic habitat than the more (13)C-enriched, bathyal species (e.g. Todarodes sagittatus and the giant squid Architeuthis dux). The cephalopods sampled had delta(15)N values ranging 4.6 per thousand, which is consistent with the species spanning approximately 1.5 trophic levels. Neither the giant octopod (Haliphron atlanticus) nor the giant squid reached the highest trophic position. Species delta(15)N was independent of body size, with large squids having both the highest (Taningia danae) and lowest (Lepidoteuthis grimaldii) delta(15)N values. Their trophic position indicates that some species share the top of the food web, together with other megacarnivores such as the sperm whale.

  20. Evolution of trophic state of Lake Endine from '70s onwards

    International Nuclear Information System (INIS)

    Garibaldi, L.; Mezzanotte, V.; Varallo, A.

    1995-01-01

    The present paper deals with the trend of the trophic level of Lake Endine in the last 20 years. A sharp decrease in the external loads has taken place due to the realization of an interceptor collecting sewage produced in the watershed and to the reduction of allowed phosphorus concentrations in the detergents. As a consequence, in lake phosphorus concentrations have decreased too, leading the lake to its theoretical natural conditions. However, less significant changes have been observed for chlorophyll and transparency, so that, according to the values of such parameters, the lake would still be eutrophic. Such situation could only be explained by an impairment between production and grazing due on the one hand to the modified composition of phytoplankton community and on the other one on the effect of the continuous and uncontrolled introduction of fish

  1. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks.

    Science.gov (United States)

    Fröbisch, Nadia B; Fröbisch, Jörg; Sander, P Martin; Schmitz, Lars; Rieppel, Olivier

    2013-01-22

    The biotic recovery from Earth's most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in today's marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian.

  2. The functional biology and trophic role of krill (Thysanoessa raschii) in a Greenlandic fjord

    DEFF Research Database (Denmark)

    Agersted, Mette Dalgaard; Nielsen, Torkel Gissel; Munk, Peter

    2011-01-01

    Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the GodthAyenbsfjord (64 degrees N, 51 degrees W) SW Greenland, through a combination of fieldwork...... and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily...... ration of 1% body C d(-1). Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 mu m, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory...

  3. Spatial and Temporal Variations of Water Quality and Trophic Status in Sembrong Reservoir, Johor

    Science.gov (United States)

    Intan Najla Syed Hashim, Syarifah; Hidayah Abu Talib, Siti; Salleh Abustan, Muhammad

    2018-03-01

    A study of spatial and temporal variations on water quality and trophic status was conducted to determine the temporal (average reading by month) and spatial variations of water quality in Sembrong reservoir and to evaluate the trophic status of the reservoir. Water samples were collected once a month from November 2016 to June 2017 in seventeen (17) sampling stations at Sembrong Reservoir. Results obtained on the concentration of dissolved oxygen (DO), water temperature, pH and secchi depth had no significant differences compared to Total Phosphorus (TP) and chlorophyll-a. The water level has significantly decreased the value of the water temperature, pH and TP. The water quality of Sembrong reservoir is classified in Class II which is suitable for recreational uses and required conventional treatment while TSI indicates that sembrong reservoir was in lower boundary of classical eutrophic (TSI > 50).

  4. Bifenthrin causes trophic cascades and alters insect emergence in mesocosms: implication for small streams

    Science.gov (United States)

    Rogers, Holly; Schmidt, Travis S.; Dabney, Brittanie L.; Hladik, Michelle; Mahler, Barbara J.; Van Metre, Peter C.

    2016-01-01

    Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC50s ranged 197.6 – 233.5 ng bifenthrin/ g organic carbon) previously thought safe for aquatic life. Indirect effects included a trophic cascade in which periphyton abundance increased after macroinvertebrate scrapers decreased. Adult emergence dynamics and corresponding terrestrial subsidies were altered at all bifenthrin concentrations tested. Extrapolating these results to the Midwestern stream assessment suggests pervasive ecological effects, with altered emergence dynamics likely in 40% of streams and a trophic cascade in 7% of streams. This study provides new evidence that a common pyrethroid might alter aquatic and terrestrial ecosystem function at the regional scale.

  5. Baseline identification in stable -isotope studies of temperate lotic systems and implications for calculated trophic positions

    DEFF Research Database (Denmark)

    Kristensen, Peter Brinkmann; Riis, Tenna; Dylmer, Hans Erik

    2016-01-01

    of two common fish species (three-spined stickleback, Gasterosteus aculeatus, and brown trout Salmo trutta) differed markedly depending on the baseline chosen. The estimated trophic position was lowest when based on Baetidae and highest when using Simuliidae. The trophic position of Gasterosteus...... aculeatus was independent of land use (proxy used=%nature) when based on Gammarus pulex and Simuliidae, and the trophic position of Salmo trutta was independent of land use when based on Simuliidae only. The trophic position estimates based on Baetidae and mean primary consumers correlated with %nature...

  6. [Applications of stable isotope analysis in the trophic ecology studies of cephalopods].

    Science.gov (United States)

    Li, Yun-Kai; Gong, Yi; Chen, Xin-Jun

    2014-05-01

    Cephalopods play an important role in marine food webs, however, knowledge about their complex life history, especially their feeding ecology, remains limited. With the rapidly increasing use of stable isotope analysis (SIA) in ecology, it becomes a powerful tool and complement of traditional methods for investigating the trophic ecology and migration patterns of invertebrates. Here, after summarizing the current methods for trophic ecology investigation of cephalopods, applications of SIA in studying the trophic ecology of cephalopods were reviewed, including the key issues such as standardization of available tissues for SIA analyzing, diet shift and migration patterns of cephalopods, with the aim of advancing its application in the biology of cephalopods in the future.

  7. Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat.

    Directory of Open Access Journals (Sweden)

    Francesca Pasotti

    Full Text Available The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands, a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii over time driving the benthic assemblages into a more compact trophic structure with

  8. Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat.

    Science.gov (United States)

    Pasotti, Francesca; Saravia, Leonardo Ariel; De Troch, Marleen; Tarantelli, Maria Soledad; Sahade, Ricardo; Vanreusel, Ann

    2015-01-01

    The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased

  9. Trophic categorization in the Rías Baixas (NW Spain: nutrients in water and in macroalgae

    Directory of Open Access Journals (Sweden)

    Rubén Villares

    2006-03-01

    Full Text Available Marine eutrophication caused by an excess supply of nutrients is a serious problem in many coastal areas throughout the world. In the present study we used the capacity of macroalgae (Ulva and Enteromorpha to integrate the nutrient regime of a water body in order to examine the trophic categorization in the embayments studied. We found that the trophic categorization established based on nutrient levels in macroalgae differed from that established based on concentrations in the water. The waters of the innermost areas of the inlets were the most nutrient enriched; the algae appeared to be more affected by specific local conditions and did not display the gradient of decreasing nutrient concentrations from inner to outer areas that was observed in the water samples. The lack of correspondence between nutrients in the water and in the algae in the present study may have been due to the heterogeneous nutrient conditions found in coastal areas, so that the intertidal algae did not adequately reflect the nutrient levels of the inner zones of the embayments under study.

  10. Trophic structure in the Gulf of Lions marine ecosystem (north-western Mediterranean Sea) and fishing impacts

    Science.gov (United States)

    Bănaru, D.; Mellon-Duval, C.; Roos, D.; Bigot, J.-L.; Souplet, A.; Jadaud, A.; Beaubrun, P.; Fromentin, J.-M.

    2013-02-01

    The Gulf of Lions ecosystem was described using the Ecopath mass-balance model to characterise its structure and functioning and to examine the effects of the multispecific fisheries operating in this area. The model is composed of 40 compartments, including 1 group of seabirds, 2 groups of cetaceans, 18 groups of fish, 12 groups of invertebrates, 5 groups of primary producers, detritus and discards. Input data were based on several recurrent scientific surveys, two alternative datasets for fishing data, stock assessment outputs, stomach content analyses and published information. Results showed that the functional groups were organised into five trophic levels with the highest one represented by dolphins, anglerfish, Atlantic bluefin tuna, European hake and European conger. European pilchard and European anchovy dominated in terms of fish biomass and catch. Other fish with high biomass such as Atlantic mackerel and blue whiting were highly important in the food web. Seabirds, dolphins and cuttlefish-squids represented keystone species. Important coupled pelagic-demersal-benthic interactions were described. The 7 different fisheries analysed were operating at mean trophic levels situated between 2.6 for small artisanal boats, and 4.1 for purse seines (> 24 m) targeting large pelagic fish, indicating an intensively exploited ecosystem. Large trawlers (24-40 m) had the highest impact on most of the groups considered; while purse seines (12-24 m) targeting small pelagic fish had the lowest impact. Preliminary results highlighted the importance of data sources for further ecosystem and fisheries analyses and management scenarios.

  11. Wolves trigger a trophic cascade to berries as alternative food for grizzly bears.

    Science.gov (United States)

    Ripple, William J; Beschta, Robert L; Fortin, Jennifer K; Robbins, Charles T

    2015-05-01

    This is a Forum article in response to: Barber-Meyer, S. (2015) Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods? Journal of Animal Ecology, 83, doi: 10.1111/1365-2656.12338. We used multiple data sets and study areas as well as several lines of evidence to investigate potential trophic linkages in Yellowstone National Park. Our results suggest that a trophic cascade from wolves to elk to berry production to berry consumption by grizzly bears may now be underway in the Park. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

  12. Regional, temporal, and species patterns of mercury in Alaskan seabird eggs: Mercury sources and cycling or food web effects?

    International Nuclear Information System (INIS)

    Day, Rusty D.; Roseneau, David G.; Vander Pol, Stacy S.; Hobson, Keith A.; Donard, Olivier F.X.; Pugh, Rebecca S.; Moors, Amanda J.; Becker, Paul R.

    2012-01-01

    Mercury concentration ([Hg]), δ 15 N, and δ 13 C values were measured in eggs from common murres (Uria aalge), thick-billed murres (U. lomvia), glaucous gulls (Larus hyperboreus), and glaucous-winged gulls (L. glaucescens) collected in Alaska from 1999 to 2005. [Hg] was normalized to a common trophic level using egg δ 15 N values and published Hg trophic magnification factors. Egg [Hg] was higher in murres from Gulf of Alaska, Cook Inlet, and Norton Sound regions compared to Bering Sea and Bering Strait regions, independent of trophic level. We believe the Yukon River outflow and terrestrial Hg sources on the southern Seward Peninsula are responsible for the elevated [Hg] in Norton Sound eggs. Normalizing for trophic level generally diminished or eliminated differences in [Hg] among taxa, but temporal variability was unrelated to trophic level. Normalizing murre egg [Hg] by trophic level improves the confidence in regional comparisons of Hg sources and biogeochemical cycling in Alaska. - Highlights: ► Seabird eggs used for monitoring Hg in Alaskan marine environment. ► Egg Hg concentrations normalized to common trophic level using δ 15 N. ► Geographic Hg patterns persist independent of trophic normalization. ► Trophic normalization reduces difference among taxa, but not temporal variability. ► Measuring δ 15 N and δ 13 C improve interpretation of seabird mercury monitoring data. - Normalizing mercury concentrations in seabird eggs to a common trophic level reveals that geographic patterns of mercury contamination exist in the Alaskan marine environment that are independent of food web effects.

  13. Spatial and Temporal Variations of Water Quality and Trophic Status in Sembrong Reservoir, Johor

    Directory of Open Access Journals (Sweden)

    Hashim Syarifah Intan Najla Syed

    2018-01-01

    Full Text Available A study of spatial and temporal variations on water quality and trophic status was conducted to determine the temporal (average reading by month and spatial variations of water quality in Sembrong reservoir and to evaluate the trophic status of the reservoir. Water samples were collected once a month from November 2016 to June 2017 in seventeen (17 sampling stations at Sembrong Reservoir. Results obtained on the concentration of dissolved oxygen (DO, water temperature, pH and secchi depth had no significant differences compared to Total Phosphorus (TP and chlorophyll-a. The water level has significantly decreased the value of the water temperature, pH and TP. The water quality of Sembrong reservoir is classified in Class II which is suitable for recreational uses and required conventional treatment while TSI indicates that sembrong reservoir was in lower boundary of classical eutrophic (TSI > 50.

  14. Trophic structure of a coastal fish community determined with diet and stable isotope analyses.

    Science.gov (United States)

    Malek, A J; Collie, J S; Taylor, D L

    2016-09-01

    A combination of dietary guild analysis and nitrogen (δ(15) N) and carbon (δ(13) C) stable-isotope analysis was used to assess the trophic structure of the fish community in Rhode Island and Block Island Sounds, an area off southern New England identified for offshore wind energy development. In the autumn of 2009, 2010 and 2011, stomach and tissue samples were taken from 20 fish and invertebrate species for analysis of diet composition and δ(15) N and δ(13) C signatures. The food chain in Rhode Island and Block Island Sounds comprises approximately four trophic levels within which the fish community is divided into distinct dietary guilds, including planktivores, benthivores, crustacivores and piscivores. Within these guilds, inter-species isotopic and dietary overlap is high, suggesting that resource partitioning or competitive interactions play a major role in structuring the fish community. Carbon isotopes indicate that most fishes are supported by pelagic phytoplankton, although there is evidence that benthic production also plays a role, particularly for obligate benthivores such as skates Leucoraja spp. This type of analysis is useful for developing an ecosystem-based approach to management, as it identifies species that act as direct links to basal resources as well as species groups that share trophic roles. © 2016 The Fisheries Society of the British Isles.

  15. Limited trophic partitioning among sympatric delphinids off a tropical oceanic atoll.

    Directory of Open Access Journals (Sweden)

    Hillary Young

    Full Text Available Understanding trophic relationships among marine predators in remote environments is challenging, but it is critical to understand community structure and dynamics. In this study, we used stable isotope analysis of skin biopsies to compare the isotopic, and thus, trophic niches of three sympatric delphinids in the waters surrounding Palmyra Atoll, in the Central Tropical Pacific: the melon-headed whale (Peponocephala electra, Gray's spinner dolphin (Stenella longirostris longirostris, and the common bottlenose dolphin (Tursiops truncatus. δ15N values suggested that T. truncatus occupied a significantly higher trophic position than the other two species. δ13C values did not significantly differ between the three delphinds, potentially indicating no spatial partitioning in depth or distance from shore in foraging among species. The dietary niche area-determined by isotopic variance among individuals-of T. truncatus was also over 30% smaller than those of the other species taken at the same place, indicating higher population specialization or lower interindividual variation. For P. electra only, there was some support for intraspecific variation in foraging ecology across years, highlighting the need for temporal information in studying dietary niche. Cumulatively, isotopic evidence revealed surprisingly little evidence for trophic niche partitioning in the delphinid community of Palmyra Atoll compared to other studies. However, resource partitioning may happen via other behavioral mechanisms, or prey abundance or availability may be adequate to allow these three species to coexist without any such partitioning. It is also possible that isotopic signatures are inadequate to detect trophic partitioning in this environment, possibly because isotopes of prey are highly variable or insufficiently resolved to allow for differentiation.

  16. The use of lipids and fatty acids to measure the trophic plasticity of the coral Stylophora subseriata.

    Science.gov (United States)

    Seemann, J; Sawall, Y; Auel, H; Richter, C

    2013-03-01

    Following up on previous investigations on the stress resistance of corals, this study assessed the trophic plasticity of the coral Stylophora subseriata in the Spermonde Archipelago (Indonesia) along an eutrophication gradient. Trophic plasticity was assessed in terms of lipid content and fatty acid composition in the holobiont relative to its plankton (50-300 μm) food as well as the zooxanthellae density, lipid, FA and chlorophyll a content. A cross-transplantation experiment was carried out for 1.5 months in order to assess the trophic potential of corals. Corals, which live in the eutrophied nearshore area showed higher zooxanthellae and chlorophyll a values and higher amounts of the dinoflagellate biomarker FA 18:4n-3. Their lipid contents were maintained at similar to levels from specimens further away from the anthropogenic impact source going up to 14.9 ± 0.9 %. A similarity percentage analysis of the groups holobiont, zooxanthellae and plankton >55 μm found that differences between the FA composition of the holobiont and zooxanthellae symbionts were more distinct in the site closer to the shore, thus heterotrophic feeding became more important. Transplanted corals attained very similar zooxanthellae, chlorophyll a and lipid values at all sites as the specimens originating from those sites, which indicates a high potential for trophic plasticity in the case of a change in food sources, which makes this species competitive and resistant to eutrophication.

  17. Trophic significance of the kelp Laminaria digitata (Lamour.) for the associated food web: a between-sites comparison

    Science.gov (United States)

    Schaal, Gauthier; Riera, Pascal; Leroux, Cédric

    2009-12-01

    This study aimed at establishing the trophic significance of the kelp Laminaria digitata for consumers inhabiting two rocky shores of Northern Brittany (France), displaying contrasted ecological conditions. The general trophic structure did not vary between these two sites, with a wide diversity of filter-feeders and predators, and only 14% of the species sampled belonging to the grazers' trophic group. The diversity of food sources fueling the food web appeared also similar. The food webs comprised four trophic levels and the prevalence of omnivory appeared relatively low compared to previous studies in the same area. Conversely, to the food web structure, which did not differ, the biochemical composition of L. digitata differed between the two sites, and was correlated to a larger diversity of grazers feeding on this kelp in sheltered conditions. This indicated that the spatial variability occurring in the nutritive value of L. digitata is likely to deeply affect the functioning of kelp-associated food webs. The contribution of L. digitata-derived organic matter to the diet of filter-feeders inhabiting these two environments was assessed using the mixing model Isosource, which showed the higher contribution of kelp matter in sheltered conditions. These results highlight the spatial variability that may occur in the functioning of kelp-associated food webs. Moreover, this suggests that hydrodynamics is likely to control the availability of kelp-derived organic matter to local filter-feeders, probably through an increase of detritus export in exposed areas.

  18. The effects of trophic transfer and environmental factors on microplastic uptake by plaice, Pleuronectes plastessa, and spider crab, Maja squinado.

    Science.gov (United States)

    Welden, Natalie Ann; Abylkhani, Bexultan; Howarth, Leigh Michael

    2018-04-16

    Microplastic pollution is apparent throughout the marine environment from deep ocean sediments to coastal habitats. Most of this is believed to originate on land, although marine activities, such as fishing and shipping, also contribute to the release and redistribution of microplastic. The relative importance of these maritime plastic sources, the manner by which they are distributed in the environment, and their effect on uptake by marine organisms are yet to be fully quantified. In this study, the relative impact of fishing activities on microplastic uptake by demersal fish and crustaceans was explored. Local fishing intensity, proximity to land and mean water velocity are compared to microplastic uptake in plaice, Pleuronectes platessa, and spider crab, Maja squinado, from the Celtic Sea. Observations were also made of microplastic contamination in ingested sand eels, Ammodytes tobianus, to establish a potential route of trophic transfer. This study is the first to identify microplastic contamination in spider crab and to document trophic transfer in the wild. Individuals were sampled from sites of varied fishing intensity in the Celtic Sea, and their stomach contents examined for the presence of microplastic. Contamination was observed in 50% of P. platessa, 42.4% of M. squinado, and 44.4% of A. tobianus. Locations of highest plastic abundance varied between P. platessa and M. squinado, indicating that different factors influence the uptake of microplastic in these two taxa. No significant link was observed between fishing effort and microplastic abundance; however, proximity to land was linked to increased abundance in M. squinado and Observations of whole prey demonstrate ongoing trophic transfer from A. tobianus to P. platessa. The lack of significant difference in microplastic abundance between predator and prey suggests that microplastic is not retained by P. platessa. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Trophic transfer of metal-based nanoparticles in aquatic environments

    DEFF Research Database (Denmark)

    Tangaa, Stine Rosendal; Selck, Henriette; Winther-Nielsen, Margrethe

    2016-01-01

    Metal-containing engineered nanoparticles (Me-ENPs) are used in a wide range of products including inks, plastics, personal care products, clothing and electronic devices. The release of Me-ENPs has been demonstrated from some products, and thus, particles are likely to enter the aquatic environm......Metal-containing engineered nanoparticles (Me-ENPs) are used in a wide range of products including inks, plastics, personal care products, clothing and electronic devices. The release of Me-ENPs has been demonstrated from some products, and thus, particles are likely to enter the aquatic...... environment where they have been shown to be taken up by a variety of species. Therefore, there is a possibility that Me-ENPs will enter and pass through aquatic food webs, but research on this topic is limited. In this tutorial review, we discuss the factors contributing to trophic transfer of Me......-ENPs, and where this information is scarce, we utilize the existing literature on aqueous metal trophic transfer as a potential starting point for greater mechanistic insight and for setting directions for future studies. We identify four key factors affecting trophic transfer of Me-ENPs: (1) environmental...

  20. Radioactive contamination of arthropods from different trophic levels in hilly and mountainous areas after the Fukushima Daiichi nuclear power plant accident.

    Science.gov (United States)

    Tanaka, Sota; Hatakeyama, Kaho; Takahashi, Sentaro; Adati, Tarô

    2016-11-01

    In order to understand the influence of the Fukushima Daiichi nuclear power plant accident on the ecosystem in hilly and mountainous areas of Fukushima Prefecture, chronological changes in the levels of radiocesium in arthropod species were investigated. From 2012 to 2014, arthropods from different trophic levels were sampled and the air radiation dose rates at the sampling sites were analyzed. The air radiation dose rates showed a significant and constant reduction over the 2 years at the sampling sites in Fukushima. The median radiocesium concentration ( 134 Cs +  137 Cs) detected in the rice grasshopper, Oxya yezoensis, and the Emma field cricket, Teleogryllus emma, dropped continuously to 0.080 and 0.078 Bq/g fresh weight, respectively, in 2014. In contrast, no significant reduction in radioactive contamination was observed in the Jorô spider, Nephila clavata, in which the level remained at 0.204 Bq/g in 2014. A significant positive correlation between radiocesium concentration and the air radiation dose rate was observed in the rice grasshopper, the Emma field cricket and the Jorô spider. The highest correlation coefficient (ρ = 0.946) was measured in the grasshopper. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  1. The trophic role of a forest salamander: impacts on invertebrates, leaf litter retention, and the humification process

    Science.gov (United States)

    M. L. Best; H. H. Welsh

    2014-01-01

    Woodland (Plethodontid) salamanders are the most abundant vertebrates in North American forests, functioning as predators on invertebrates and prey for higher trophic levels. We investigated the role of Ensatina (Ensatina eschscholtzii) in regulating invertebrate numbers and leaf litter retention in a northern California forest. Our objective was...

  2. Bioaccumulation and trophic transfer of dioxins in marine copepods and fish

    International Nuclear Information System (INIS)

    Zhang Qiong; Yang Liuyan; Wang Wenxiong

    2011-01-01

    Despite the great concerns about dioxins in the marine environments, the biokinetics and bioaccumulation of these compounds in marine organisms remains little known. Using radioactive tracers the aqueous uptake, dietary assimilation efficiency, and elimination of dioxins were measured in marine phytoplankton, copepods and seabream. The calculated uptake rate constant of dioxins decreased with increasing trophic levels, whereas the dietary assimilation efficiency (AE) was 28.5-57.6% in the copepods and 36.6-70.2% in the fish. The dietary AE was highly dependent on the food concentrations and food type. The elimination rate constant of dioxin in the copepods varied with different exposure pathways as well as food concentration and food type. Biokinetic calculation showed that dietary accumulation was the predominant pathway for dioxin accumulation in marine copepods and fish. Aqueous uptake can be an important pathway only when the bioconcentration of dioxins in the phytoplankton was low. - Highlights: → Radiotracer was used to quantify the biokinetics of dioxins in a marine food chain. → Aqueous uptake rate of dioxins decreased with increasing trophic levels. → Dietary assimilation efficiencies were comparable between the copepods and the fish. → Both food type and density significantly affected the dietary assimilation of dioxins. → Diet was the predominant pathway for dioxin accumulation in marine copepods and fish. - Biokinetic calculation showed that dietary accumulation was the predominant pathway for dioxin accumulation in marine copepods and fish.

  3. Potential trophic cascades triggered by the barred owl range expansion

    Science.gov (United States)

    Holm, Samantha R.; Noon, Barry R.; Wiens, David; Ripple, William J.

    2016-01-01

    Recently, the barred owl (Strix varia) has expanded its range into the Pacific Northwest of the United States resulting in pronounced effects on the demography and behavior of the northern spotted owl (S. occidentalis caurina). The range expansion has brought together historically allopatric species, creating the potential for significant changes in the avian predator community with possible cascading effects on food-web dynamics. The adverse effects of the barred owl on the behavior and demography of the northern spotted owl are well-documented, but little is known about the immediate and long-term effects changes in the predator community may have on native species composition and ecosystem processes. Based on northern spotted owl and barred owl selection for diet and habitat resources, there is a potential for trophic cascades within the region's predator and prey communities, differing responses by their shared and unique prey species, and possible direct and indirect effects on ecosystem processes. We explored the possible ecological consequences of the barred owl range expansion to wildlife communities of the Pacific Northwest based on the theoretical underpinnings of predator–prey relationships, interspecific competition, intraguild predation, and potential cascading trophic interactions. Negative effects on fitness of northern spotted owls because of interspecific competition with barred owls are strong selection forces that may contribute to the regional extinction of the northern spotted owl. In addition, we posit that shared prey species and those uniquely consumed by barred owls, along with other competing native predators, may experience changes in behavior, abundance, and distribution as a result of increased rates of predation by rapidly expanding populations of barred owls.

  4. Coastal habitats as surrogates for taxonomic, functional and trophic structures of benthic faunal communities.

    Science.gov (United States)

    Törnroos, Anna; Nordström, Marie C; Bonsdorff, Erik

    2013-01-01

    Due to human impact, there is extensive degradation and loss of marine habitats, which calls for measures that incorporate taxonomic as well as functional and trophic aspects of biodiversity. Since such data is less easily quantifiable in nature, the use of habitats as surrogates or proxies for biodiversity is on the rise in marine conservation and management. However, there is a critical gap in knowledge of whether pre-defined habitat units adequately represent the functional and trophic structure of communities. We also lack comparisons of different measures of community structure in terms of both between- (β) and within-habitat (α) variability when accounting for species densities. Thus, we evaluated a priori defined coastal habitats as surrogates for traditional taxonomic, functional and trophic zoobenthic community structure. We focused on four habitats (bare sand, canopy-forming algae, seagrass above- and belowground), all easily delineated in nature and defined through classification systems. We analyzed uni- and multivariate data on species and trait diversity as well as stable isotope ratios of benthic macrofauna. A good fit between habitat types and taxonomic and functional structure was found, although habitats were more similar functionally. This was attributed to within-habitat heterogeneity so when habitat divisions matched the taxonomic structure, only bare sand was functionally distinct. The pre-defined habitats did not meet the variability of trophic structure, which also proved to differentiate on a smaller spatial scale. The quantification of trophic structure using species density only identified an epi- and an infaunal unit. To summarize the results we present a conceptual model illustrating the match between pre-defined habitat types and the taxonomic, functional and trophic community structure. Our results show the importance of including functional and trophic aspects more comprehensively in marine management and spatial planning.

  5. Effects of Trophic Modes, Carbon Sources, and Salinity on the Cell Growth and Lipid Accumulation of Tropic Ocean Oilgae Strain Desmodesmus sp. WC08.

    Science.gov (United States)

    Zhao, Zhenyu; Ma, Shasha; Li, Ang; Liu, Pinghuai; Wang, Meng

    2016-10-01

    The effects of trophic modes, carbon sources, and salinity on the growth and lipid accumulation of a marine oilgae Desmodesmus sp. WC08 in different trophic cultures were assayed by single factor experiment based on the blue-green algae medium (BG-11). The results implied that biomass and lipid accumulation culture process were optimized depending on the tophic modes, sorts, and concentration of carbon sources and salinity in the cultivation. There was no significant difference in growth or lipid accumulation with Na 2 CO 3 amendment or NaHCO 3 amendment. However, Na 2 CO 3 amendment did enhance the biomass and lipid accumulation to some extent. The highest Desmodesmus sp. WC08 biomass and lipid accumulation was achieved in the growth medium with photoautotrophic cultivation, 0.08 g L -1 Na 2 CO 3 amendment and 15 g L -1 sea salt, respectively.

  6. MNEMIOPSIS LEIDYI IMPACT ON SOME TROPHICAL CHAINS OF THE CASPIAN SEA

    Directory of Open Access Journals (Sweden)

    A. M. KAMAKIN

    2010-01-01

    Full Text Available Results of monitoring investigations over the past 10 years are presented concerning the distribution of a new species-invader in the Caspian Sea, Mnemiopsis leidyi. The spatial distribution of its population is shown during the period of its maximal development in August-September. The influence of that gelatinous invader on different levels of the trophic pyramid is described to show the cause of qualitative and quantitative decline in the nutritive base both of plankton feeders (Caspian kilka, shads and mollusk-eating fish (roach, sea bream and common carp, to estimate the level and reveal the trend of ecosystem development in the Caspian Sea in the near future.

  7. The hormone prolactin is a novel, endogenous trophic factor able to regulate reactive glia and to limit retinal degeneration.

    Science.gov (United States)

    Arnold, Edith; Thebault, Stéphanie; Baeza-Cruz, German; Arredondo Zamarripa, David; Adán, Norma; Quintanar-Stéphano, Andrés; Condés-Lara, Miguel; Rojas-Piloni, Gerardo; Binart, Nadine; Martínez de la Escalera, Gonzalo; Clapp, Carmen

    2014-01-29

    Retinal degeneration is characterized by the progressive destruction of retinal cells, causing the deterioration and eventual loss of vision. We explored whether the hormone prolactin provides trophic support to retinal cells, thus protecting the retina from degenerative pressure. Inducing hyperprolactinemia limited photoreceptor apoptosis, gliosis, and changes in neurotrophin expression, and it preserved the photoresponse in the phototoxicity model of retinal degeneration, in which continuous exposure of rats to bright light leads to retinal cell death and retinal dysfunction. In this model, the expression levels of prolactin receptors in the retina were upregulated. Moreover, retinas from prolactin receptor-deficient mice exhibited photoresponsive dysfunction and gliosis that correlated with decreased levels of retinal bFGF, GDNF, and BDNF. Collectively, these data unveiled prolactin as a retinal trophic factor that may regulate glial-neuronal cell interactions and is a potential therapeutic molecule against retinal degeneration.

  8. The trophic position of the alien crab Rhithropanopeus harrisii (crustacea decapoda panopeidae) in the Taman Bay, Sea of Azov community

    Science.gov (United States)

    Zalota, A. K.; Kolyuchkina, G. A.; Tiunov, A. V.; Biriukova, S. V.; Spiridonov, V. A.

    2017-03-01

    This work concerns the trophic web positioning of the alien crab Rhithropanopeus harrisii and other common marine invertebrate species and fishes in the benthic ecosystem of the shallows of Taman Bay, Sea of Azov. The base of the trophic web in this system is composed of phytoplankton, macrophytes (algae and marine grasses), and reeds that use atmospheric carbon for photosynthesis. Analysis of the isotopic composition of nitrogen and carbon has shown that although marine grasses are dominating primary producers in the shallows of the bay, primary consumers (such as Cerastoderma glaucum, Porifera gen. sp., Gammarus aequicauda, Deshayesorchestia deshayesii and Idotea balthica) only partially use this organic source; instead, they use a combination of different sources of primary production. It has been shown that the food source of the alien crab is primarily of animal origin. In Taman Bay, R. harrisii is on the same trophic level as other carnivores/scavengers: benthic fishes Syngnathus nigrolineatus, Gobius spp. and native crab Pilumnus hirtellus and shrimp Palaemon adspersus.

  9. Energetic differences between bacterioplankton trophic groups and coral reef resistance.

    Science.gov (United States)

    McDole Somera, Tracey; Bailey, Barbara; Barott, Katie; Grasis, Juris; Hatay, Mark; Hilton, Brett J; Hisakawa, Nao; Nosrat, Bahador; Nulton, James; Silveira, Cynthia B; Sullivan, Chris; Brainard, Russell E; Rohwer, Forest

    2016-04-27

    Coral reefs are among the most productive and diverse marine ecosystems on the Earth. They are also particularly sensitive to changing energetic requirements by different trophic levels. Microbialization specifically refers to the increase in the energetic metabolic demands of microbes relative to macrobes and is significantly correlated with increasing human influence on coral reefs. In this study, metabolic theory of ecology is used to quantify the relative contributions of two broad bacterioplankton groups, autotrophs and heterotrophs, to energy flux on 27 Pacific coral reef ecosystems experiencing human impact to varying degrees. The effective activation energy required for photosynthesis is lower than the average energy of activation for the biochemical reactions of the Krebs cycle, and changes in the proportional abundance of these two groups can greatly affect rates of energy and materials cycling. We show that reef-water communities with a higher proportional abundance of microbial autotrophs expend more metabolic energy per gram of microbial biomass. Increased energy and materials flux through fast energy channels (i.e. water-column associated microbial autotrophs) may dampen the detrimental effects of increased heterotrophic loads (e.g. coral disease) on coral reef systems experiencing anthropogenic disturbance. © 2016 The Author(s).

  10. Trophic structure of the fouling community in Odessa Bay (Black Sea

    Directory of Open Access Journals (Sweden)

    A. Y. Varigin

    2016-06-01

    Full Text Available The trophic structure of the coastal fouling community of Odessa Bay (Black Sea, which was composed of 10 species of macrophytes, 57 invertebrate species and 4 species of fish, was determined. The basic trophic relationship between organisms composing the community is shown. A minimization of interspecific trophic competition within the community is noted. The main sources of food material entering the fouling community were determined. We show that a significant proportion of food in the form of detritus, dissolved organic matter and small planktonic organisms enters the community from the water column. Filtration and pumping activity of sestonophage-organisms, particularly mussels, helps to attract food material to the community. Primary producers of the community are macrophytes and microphytes, which develop on account of their photosynthetic activity and ensure the provision of food to herbivores. The trophic group of detritophages consumes different fractions of the detritus which accumulates in the byssus threads of bivalve molluscs. In this context, mussel druses act as sediment traps, collecting detritus. Numerous polyphages, which are essentially omnivores and do not usually lack food material, were noted in the community. A small group of carnivorous invertebrates, whose representatives actively attack small animals, was identified. The abundance of these species in the community was about 1%, and their biomass less than 0.6%. Fish living in macrophyte weeds are the consumers in the community. We determined that the highest relative abundance (over 36% in the fouling community was reached by sestonophages and polyphages. We found that the undisputed leader in the relative biomass (over 97% in the fouling community ofOdessaBaywas the sestonophages (mainly composed of mussels. We determined that the trophic structure index of the community was 0.94, which confirms the significant dominance in biomass of bivalves over other species in

  11. Feeding behavior and trophic interaction of three shark species in the Galapagos Marine Reserve

    Directory of Open Access Journals (Sweden)

    Diego Páez-Rosas

    2018-05-01

    Full Text Available There is great concern about the future of sharks in Ecuador because of the lack of biological knowledge of most species that inhabit the region. This paper analyzes the feeding behavior of the pelagic thresher shark (Alopias pelagicus, the blue shark (Prionace glauca and the silky shark (Carcharhinus falciformis through the use of stable isotopes of carbon and nitrogen (δ13C and δ15N, with the aim of determining the degree of interaction between these species in the Galapagos Marine Reserve. No interspecific differences were found in use of oceanic vs. inshore feeding areas (δ13C: Kruskal–Wallis test, p = 0.09. The position in the hierarchy of the food web where A. pelagicus feeds differed from that of the other species (δ15N: Kruskal–Wallis test, p = 0.01. There were no significant differences in δ13C and δ15N values between males and females of the three species (Student’s t-test, p > 0.05, which suggests that both sexes have a similar feeding behavior. A specialist strategy was observed in P. glauca (trophic niche breadth TNB = 0.69, while the other species were found to be generalist (A. pelagicus TNB = 1.50 and C. falciformis TNB = 1.09. The estimated trophic level (TL varied between the three species. C. falciformis occupied the highest trophic level (TL = 4.4, making it a quaternary predator in the region. The results of this study coincide with the identified behavior in these predators in other areas of the tropical Pacific (Colombia and Mexico, and suggest a pelagic foraging strategy with differential consumption of prey between the three species. These ecological aspects can provide timely information when implementing in conservation measures for these shark species in the Tropical Pacific and Galapagos Marine Reserve.

  12. Feeding behavior and trophic interaction of three shark species in the Galapagos Marine Reserve.

    Science.gov (United States)

    Páez-Rosas, Diego; Insuasti-Zarate, Paul; Riofrío-Lazo, Marjorie; Galván-Magaña, Felipe

    2018-01-01

    There is great concern about the future of sharks in Ecuador because of the lack of biological knowledge of most species that inhabit the region. This paper analyzes the feeding behavior of the pelagic thresher shark ( Alopias pelagicus ), the blue shark ( Prionace glauca ) and the silky shark ( Carcharhinus falciformis ) through the use of stable isotopes of carbon and nitrogen ( δ 13 C and δ 15 N), with the aim of determining the degree of interaction between these species in the Galapagos Marine Reserve. No interspecific differences were found in use of oceanic vs. inshore feeding areas ( δ 13 C: Kruskal-Wallis test, p = 0.09). The position in the hierarchy of the food web where A. pelagicus feeds differed from that of the other species ( δ 15 N: Kruskal-Wallis test, p = 0.01). There were no significant differences in δ 13 C and δ 15 N values between males and females of the three species (Student's t -test, p  > 0.05), which suggests that both sexes have a similar feeding behavior. A specialist strategy was observed in P. glauca (trophic niche breadth TNB = 0.69), while the other species were found to be generalist ( A. pelagicus TNB = 1.50 and C. falciformis TNB = 1.09). The estimated trophic level (TL) varied between the three species. C. falciformis occupied the highest trophic level (TL = 4.4), making it a quaternary predator in the region. The results of this study coincide with the identified behavior in these predators in other areas of the tropical Pacific (Colombia and Mexico), and suggest a pelagic foraging strategy with differential consumption of prey between the three species. These ecological aspects can provide timely information when implementing in conservation measures for these shark species in the Tropical Pacific and Galapagos Marine Reserve.

  13. Pre- and post-hatch trophic egg production in the subsocial burrower bug, Canthophorus niveimarginatus (Heteroptera: Cydnidae)

    Science.gov (United States)

    Filippi, Lisa; Baba, Narumi; Inadomi, Koichi; Yanagi, Takao; Hironaka, Mantaro; Nomakuchi, Shintaro

    2009-02-01

    In recent years, three terrestrial bugs, Adomerus triguttulus and Sehirus cinctus (Cydnidae) and the closely related Parastrachia japonensis (Parastrachiidae), have been the focus of several fascinating studies because of the remarkable, extensive parental care they were found to display. This care includes egg and nymph guarding, production of trophic eggs, unfertilized, low cost eggs that are used as food by newly hatched nymphs, and progressive provisioning of the host seed. In this study, we have investigated yet a third related Asian cydnid, Canthophorus niveimarginatus, with regard to the possible occurrence of some or all of these complex traits in order to assess how widespread these maternal investment patterns are in this group of insects and to better understand the implications of their manifestations from an evolutionary context. Manipulative experiments were carried out in the lab to determine whether females provision nests. Observational and egg removal studies were carried out to determine whether trophic eggs are produced, and, if they are, their possible impact on nymphal success. The findings revealed that C. niveimarginatus does, in fact, progressively provision young, and this species also displays all of the other behaviors associated with extended parental care in subsocial insects. Moreover, unlike the other two related species, which place trophic eggs on the surface of the original egg mass, C. niveimarginatus produces both pre- and post-hatch trophic eggs. Nymphs deprived of access to post-hatch trophic eggs had significantly lower body weight and survival rate than those that fed on them. To our knowledge, this is the first time the production of both pre- and post-hatch trophic eggs has been demonstrated in insects outside the Hymenoptera. In this paper, we qualitatively and quantitatively demonstrate the provisioning behavior and patterns of trophic egg production in C. niveimarginatus. When and how trophic eggs are produced and

  14. Enhanced understanding of ectoparasite: host trophic linkages on coral reefs through stable isotope analysis

    Science.gov (United States)

    Demopoulos, Amanda W. J.; Sikkel, Paul C.

    2015-01-01

    Parasitism, although the most common type of ecological interaction, is usually ignored in food web models and studies of trophic connectivity. Stable isotope analysis is widely used in assessing the flow of energy in ecological communities and thus is a potentially valuable tool in understanding the cryptic trophic relationships mediated by parasites. In an effort to assess the utility of stable isotope analysis in understanding the role of parasites in complex coral-reef trophic systems, we performed stable isotope analysis on three common Caribbean reef fish hosts and two kinds of ectoparasitic isopods: temporarily parasitic gnathiids (Gnathia marleyi) and permanently parasitic cymothoids (Anilocra). To further track the transfer of fish-derived carbon (energy) from parasites to parasite consumers, gnathiids from host fish were also fed to captive Pederson shrimp (Ancylomenes pedersoni) for at least 1 month. Parasitic isopods had δ13C and δ15N values similar to their host, comparable with results from the small number of other host–parasite studies that have employed stable isotopes. Adult gnathiids were enriched in 15N and depleted in13C relative to juvenile gnathiids, providing insights into the potential isotopic fractionation associated with blood-meal assimilation and subsequent metamorphosis. Gnathiid-fed Pedersen shrimp also had δ13C values consistent with their food source and enriched in 15N as predicted due to trophic fractionation. These results further indicate that stable isotopes can be an effective tool in deciphering cryptic feeding relationships involving parasites and their consumers, and the role of parasites and cleaners in carbon transfer in coral-reef ecosystems specifically.

  15. Enhanced understanding of ectoparasite–host trophic linkages on coral reefs through stable isotope analysis

    Directory of Open Access Journals (Sweden)

    Amanda W.J. Demopoulos

    2015-04-01

    Full Text Available Parasitism, although the most common type of ecological interaction, is usually ignored in food web models and studies of trophic connectivity. Stable isotope analysis is widely used in assessing the flow of energy in ecological communities and thus is a potentially valuable tool in understanding the cryptic trophic relationships mediated by parasites. In an effort to assess the utility of stable isotope analysis in understanding the role of parasites in complex coral-reef trophic systems, we performed stable isotope analysis on three common Caribbean reef fish hosts and two kinds of ectoparasitic isopods: temporarily parasitic gnathiids (Gnathia marleyi and permanently parasitic cymothoids (Anilocra. To further track the transfer of fish-derived carbon (energy from parasites to parasite consumers, gnathiids from host fish were also fed to captive Pederson shrimp (Ancylomenes pedersoni for at least 1 month. Parasitic isopods had δ13C and δ15N values similar to their host, comparable with results from the small number of other host–parasite studies that have employed stable isotopes. Adult gnathiids were enriched in 15N and depleted in 13C relative to juvenile gnathiids, providing insights into the potential isotopic fractionation associated with blood-meal assimilation and subsequent metamorphosis. Gnathiid-fed Pedersen shrimp also had δ13C values consistent with their food source and enriched in 15N as predicted due to trophic fractionation. These results further indicate that stable isotopes can be an effective tool in deciphering cryptic feeding relationships involving parasites and their consumers, and the role of parasites and cleaners in carbon transfer in coral-reef ecosystems specifically.

  16. Trophic interactions in the St. Lawrence Estuary (Canada): Must the blue whale compete for krill?

    Science.gov (United States)

    Savenkoff, C.; Comtois, S.; Chabot, D.

    2013-09-01

    Inverse methodology was used to construct a mass-balance model of the Lower St. Lawrence Estuary (LSLE) for the 2008-2010 time period. Our first objective was to make an overall description of community structure, trophic interactions, and the effects of fishing and predation on the vertebrate and invertebrate communities of the ecosystem. A second objective was to identify other important predators of krill, and to assess if these compete with blue whales, listed as endangered under the Canadian Species at Risk Act in 2005 (northwest Atlantic population). The Estuary and the Gulf of St. Lawrence are summer feeding grounds for blue whales and other marine mammals. Blue whales eat only euphausiids (krill) and require dense concentrations of prey to meet their energy requirements, which makes them particularly vulnerable to changes in prey availability. In the LSLE, many species from secondary producers (hyperiid amphipods, other macrozooplankton) to top predators (fish, birds, and marine mammals) consumed euphausiids. Consequently, krill predators were found at all consumer trophic levels. However, our results showed that only about 35% of the estimated euphausiid production was consumed by all predator species combined. Euphausiid did not seem to be a restricted resource in the LSLE ecosystem, at least during the study period. The blue whale did not appear to have to compete for krill in the LSLE.

  17. Total mercury levels in commercial fish species from Italian fishery and aquaculture.

    Science.gov (United States)

    Di Lena, Gabriella; Casini, Irene; Caproni, Roberto; Fusari, Andrea; Orban, Elena

    2017-06-01

    Total mercury levels were measured in 42 commercial fish species caught off the Central Adriatic and Tyrrhenian coasts of Italy and in 6 aquaculture species. The study on wild fish covered species differing in living habitat and trophic level. The study on farmed fish covered marine and freshwater species from intensive and extensive aquaculture and their feed. Mercury levels were analysed by thermal decomposition-amalgamation-atomic absorption spectrophotometry. Total mercury concentrations in the muscle of wild fish showed a high variability among species (0.025-2.20 mg kg -1 wet weight). The lowest levels were detected in low trophic-level demersal and pelagic-neritic fish and in young individuals of high trophic-level species. Levels exceeding the European Commission limits were found in large-size specimens of high trophic-level pelagic and demersal species. Fish from intensive farming showed low levels of total mercury (0.008-0.251 mg kg -1 ). Fish from extensive rearing showed variable contamination levels, depending on the area of provenience. An estimation of the human intake of mercury associated to the consumption of the studied fish and its comparison with the tolerable weekly intake is provided.

  18. Diet Composition and Trophic Ecology of Northeast Pacific Ocean Sharks.

    Science.gov (United States)

    Bizzarro, Joseph J; Carlisle, Aaron B; Smith, Wade D; Cortés, Enric

    Although there is a general perception of sharks as large pelagic, apex predators, most sharks are smaller, meso- and upper-trophic level predators that are associated with the seafloor. Among 73 shark species documented in the eastern North Pacific (ENP), less than half reach maximum lengths >200cm, and 78% occur in demersal or benthic regions of the continental shelf or slope. Most small (≤200cm) species (e.g., houndsharks) and demersal, nearshore juveniles of larger species (e.g., requiem sharks) consume small teleosts and decapod crustaceans, whereas large species in pelagic coastal and oceanic environments feed on large teleosts and squids. Several large, pelagic apex predator species occur in the ENP, but the largest species (i.e., Basking Shark, Whale Shark) consume zooplankton or small nekton. Size-based dietary variability is substantial for many species, and segregation of juvenile and adult foraging habitats also is common (e.g., Horn Shark, Shortfin Mako). Temporal dietary differences are most pronounced for temperate, nearshore species with wide size ranges, and least pronounced for smaller species in extreme latitudes and deep-water regions. Sympatric sharks often occupy various trophic positions, with resource overlap differing by space and time and some sharks serving as prey to other species. Most coastal species remain in the same general region over time and feed opportunistically on variable prey inputs (e.g., season migrations, spawning, or recruitment events), whereas pelagic, oceanic species actively seek hot spots of prey abundance that are spatiotemporally variable. The influence of sharks on ecosystem structure and regulation has been downplayed compared to that of large teleosts species with higher per capita consumption rates (e.g., tunas, billfishes). However, sharks also exert indirect influences on prey populations by causing behavioural changes that may result in restricted ranges and reduced fitness. Except for food web modelling

  19. Effects of trophic ecology and habitat use on maternal transfer of contaminants in four species of young of the year lamniform sharks.

    Science.gov (United States)

    Lyons, Kady; Carlisle, Aaron; Preti, Antonella; Mull, Christopher; Blasius, Mary; O'Sullivan, John; Winkler, Chuck; Lowe, Christopher G

    2013-09-01

    Organic contaminant and total mercury concentrations were compared in four species of lamniform sharks over several age classes to examine bioaccumulation patterns and gain insights into trophic ecology. Contaminants found in young of the year (YOY) sharks were assumed to be derived from maternal sources and used as a proxy to investigate factors that influence maternal offloading processes. YOY white (Carcharodon carcharias) and mako (Isurus oxyrinchus) sharks had comparable and significantly higher concentrations of PCBs, DDTs, pesticides, and mercury than YOY thresher (Alopias vulpinus) or salmon (Lamna ditropis) sharks. A significant positive relationship was found between YOY contaminant loads and maternal trophic position, suggesting that trophic ecology is one factor that plays an important role in maternal offloading. Differences in organic contaminant signatures and contaminant concentration magnitudes among species corroborated what is known about species habitat use and may be used to provide insights into the feeding ecology of these animals. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Trophic transfer of differently functionalized zinc oxide nanoparticles from crustaceans (Daphnia magna) to zebrafish (Danio rerio)

    DEFF Research Database (Denmark)

    Skjolding, Lars Michael; Winther-Nielsen, M.; Baun, Anders

    2014-01-01

    ) higher than toxic levels reported for zinc in D. magna. Consequently, the zinc recovered in the animals was not solely due to soluble zinc, but agglomerates/aggregates of ZnO NP or ZnO-octyl NP contributed to the body burdens. The trophic transfer study showed uptake of both ZnO NP and ZnO-octyl NP...

  1. Identification of trophic interactions within an estuarine food web (northern New Zealand) using fatty acid biomarkers and stable isotopes

    Science.gov (United States)

    Alfaro, Andrea C.; Thomas, François; Sergent, Luce; Duxbury, Mark

    2006-10-01

    Fatty acid biomarkers and stable isotope signatures were used to identify the trophic dynamics of a mangrove/seagrass estuarine food web at Matapouri, northern New Zealand. Specific fatty acids were used to identify the preferred food sources (i.e., mangroves, seagrass, phytoplankton, macroalgae, bacteria, and zooplankton) of dominant fauna (i.e., filter feeders, grazing snails, scavenger/predatory snails, shrimp, crabs, and fish), and their presence in water and sediment samples throughout the estuary. The diets of filter feeders were found to be dominated by dinoflagellates, whereas grazers showed a higher diatom contribution. Bacteria associated with organic debris on surface sediments and brown algal ( Hormosira banksii) material in the form of suspended organic matter also accounted for a high proportion of most animal diets. Animals within higher trophic levels had diverse fatty acid profiles, revealing their varied feeding strategies and carbon sources. The stable isotope (δ 13C and δ 15N) analyses of major primary producers and consumers/predators revealed a trend of 15N enrichment with increasing trophic level, while δ 13C values provided a generally good description of carbon flow through the food web. Overall results from both fatty acid profiles and stable isotopes indicate that a variety of carbon sources with a range of trophic pathways typify this food web. Moreover, none of the animals studied was dependent on a single food source. This study is the first to use a comprehensive fatty acid biomarker and stable isotope approach to investigate the food web dynamics within a New Zealand temperate mangrove/seagrass estuary. This quantitative research may contribute to the currently developing management strategies for estuaries in northern New Zealand, especially for those perceived to have expanding mangrove fringes.

  2. Fish community reassembly after a coral mass mortality: higher trophic groups are subject to increased rates of extinction.

    Science.gov (United States)

    Alonso, David; Pinyol-Gallemí, Aleix; Alcoverro, Teresa; Arthur, Rohan

    2015-05-01

    Since Gleason and Clements, our understanding of community dynamics has been influenced by theories emphasising either dispersal or niche assembly as central to community structuring. Determining the relative importance of these processes in structuring real-world communities remains a challenge. We tracked reef fish community reassembly after a catastrophic coral mortality in a relatively unfished archipelago. We revisited the stochastic model underlying MacArthur and Wilson's Island Biogeography Theory, with a simple extension to account for trophic identity. Colonisation and extinction rates calculated from decadal presence-absence data based on (1) species neutrality, (2) trophic identity and (3) site-specificity were used to model post-disturbance reassembly, and compared with empirical observations. Results indicate that species neutrality holds within trophic guilds, and trophic identity significantly increases overall model performance. Strikingly, extinction rates increased clearly with trophic position, indicating that fish communities may be inherently susceptible to trophic downgrading even without targeted fishing of top predators. © 2015 John Wiley & Sons Ltd/CNRS.

  3. Application of Trophic Magnification Factors (TMFs) Under the ...

    Science.gov (United States)

    Directive 2013/39/EU amending and updating the Water Framework Directive (2000/60/EC) and its Daughter Directive (the so-called EQS Directive: 2008/105/EC) sets Environmental Quality Standards for biota (EQSbiota) for a number of bioaccumulative chemicals which can pose a threat to both aquatic wildlife (piscivorous birds and mammals) and human health via the consumption of contaminated prey or the intake of contaminated food originating from the aquatic environment. Member States (MS) of the European Union will need to establish programs to monitor the concentration of 11 priority substances in biota and assess compliance against these new standards for surface water classification. The biota standards essentially refer to fish and should be applied to the trophic level (TL) at which contaminant concentrations peak, so that the predator of the species at that TL is exposed to the highest contaminant levels in its food. For chemicals that are subject to biomagnification, the peak concentrations are theoretically attained at TL 3 to 4 in freshwater food webs and TL 5 in marine food webs, where the risk of secondary poisoning of top predators should also be considered. An EU-wide guidance effectively addresses the implementation of EQSbiota (EC 2014). Flexibility is allowed in the choice of target species used for monitoring because of the diversity of both habitats and aquatic community composition across Europe. According to that guidance, the consistency and co

  4. Genetic variation in foundation species governs the dynamics of trophic interactions

    Science.gov (United States)

    Valencia-Cuevas, Leticia; Mussali-Galante, Patricia; Cano-Santana, Zenón; Pujade-Villar, Juli; Equihua-Martínez, Armando

    2018-01-01

    Abstract Various studies have demonstrated that the foundation species genetic diversity can have direct effects that extend beyond the individual or population level, affecting the dependent communities. Additionally, these effects may be indirectly extended to higher trophic levels throughout the entire community. Quercus castanea is an oak species with characteristics of foundation species beyond presenting a wide geographical distribution and being a dominant element of Mexican temperate forests. In this study, we analyzed the influence of population (He) and individual (HL) genetic diversity of Q. castanea on its canopy endophagous insect community and associated parasitoids. Specifically, we studied the composition, richness (S) and density of leaf-mining moths (Lepidoptera: Tischeridae, Citheraniidae), gall-forming wasps (Hymenoptera: Cynipidae), and canopy parasitoids of Q. castanea. We sampled 120 trees belonging to six populations (20/site) through the previously recognized gradient of genetic diversity. In total, 22 endophagous insect species belonging to three orders (Hymenoptera, Lepidoptera, and Diptera) and 20 parasitoid species belonging to 13 families were identified. In general, we observed that the individual genetic diversity of the host plant (HL) has a significant positive effect on the S and density of the canopy endophagous insect communities. In contrast, He has a significant negative effect on the S of endophagous insects. Additionally, indirect effects of HL were observed, affecting the S and density of parasitoid insects. Our results suggest that genetic variation in foundation species can be one of the most important factors governing the dynamics of tritrophic interactions that involve oaks, herbivores, and parasitoids. PMID:29492034

  5. The Aquatic Trophic Ecology of Suisun Marsh, San Francisco Estuary, California, During Autumn in a Wet Year

    Directory of Open Access Journals (Sweden)

    Robert E. Schroeter

    2015-09-01

    Full Text Available doi: http://dx.doi.org/10.15447/sfews.v13iss3art6Using stable isotopes of carbon (δ13C and nitrogen (δ15N and mixing models, we investigated the trophic levels and carbon sources of invertebrates and fishes of a large tidal marsh in the San Francisco Estuary. Our goal was to better understand an estuarine food web comprised of native and alien species. We found the following: (1 the food web was based largely on carbon from phytoplankton and emergent-aquatic and terrestrial vegetation, but carbon from submerged aquatic vegetation and phytobenthos was also used; (2 alien species increased the complexity of the food web by altering carbon-flow pathways and by occupying trophic positions different from native species; and (3 most consumers were dietary generalists.

  6. A comparison of community and trophic structure in five marine ecosystems based on energy budgets and system metrics

    Science.gov (United States)

    Gaichas, Sarah; Skaret, Georg; Falk-Petersen, Jannike; Link, Jason S.; Overholtz, William; Megrey, Bernard A.; Gjøsæter, Harald; Stockhausen, William T.; Dommasnes, Are; Friedland, Kevin D.; Aydin, Kerim

    2009-04-01

    Energy budget models for five marine ecosystems were compared to identify differences and similarities in trophic and community structure. We examined the Gulf of Maine and Georges Bank in the northwest Atlantic Ocean, the combined Norwegian/Barents Seas in the northeast Atlantic Ocean, and the eastern Bering Sea and the Gulf of Alaska in the northeast Pacific Ocean. Comparable energy budgets were constructed for each ecosystem by aggregating information for similar species groups into consistent functional groups. Several ecosystem indices (e.g., functional group production, consumption and biomass ratios, cumulative biomass, food web macrodescriptors, and network metrics) were compared for each ecosystem. The comparative approach clearly identified data gaps for each ecosystem, an important outcome of this work. Commonalities across the ecosystems included overall high primary production and energy flow at low trophic levels, high production and consumption by carnivorous zooplankton, and similar proportions of apex predator to lower trophic level biomass. Major differences included distinct biomass ratios of pelagic to demersal fish, ranging from highest in the combined Norwegian/Barents ecosystem to lowest in the Alaskan systems, and notable differences in primary production per unit area, highest in the Alaskan and Georges Bank/Gulf of Maine ecosystems, and lowest in the Norwegian ecosystems. While comparing a disparate group of organisms across a wide range of marine ecosystems is challenging, this work demonstrates that standardized metrics both elucidate properties common to marine ecosystems and identify key distinctions useful for fisheries management.

  7. Trophic position of soil nematodes in boreal forests as indicated by stable isotope analysis

    Science.gov (United States)

    Kudrin, Alexey; Tsurikov, Sergey

    2016-04-01

    Despite the well-developed trophic classification of soil nematodes, their position in soil food webs is still little understood. Observed deviations from the typical feeding strategy indicate that a simplified trophic classification probably does not fully reflect actual trophic interactions. Furthermore, the extent and functional significance of nematodes as prey for other soil animals remains unknown. Stable isotope analysis (SIA) is powerful tool for investigating the structure of soil food webs, but its application to the study of soil nematodes has been limited to only a few studies. We used stable isotope analysis to gain a better understanding of trophic links of several groups of soil nematodes in two boreal forests on albeluvisol. We investigated four taxonomic groups of nematodes: Mononchida, Dorylaimida, Plectidae and Tylenchidae (mostly from the genus Filenchus), that according to the conventional trophic classification represent predators, omnivores, bacterivores and root-fungal feeders, respectively. To assess the trophic position of nematodes, we used a comparison against a set of reference species including herbivorous, saprophagous and predatory macro-invertebrates, oribatid and mesostigmatid mites, and collembolans. Our results suggest that trophic position of the investigated groups of soil nematodes generally corresponds to the conventional classification. All nematodes were enriched in 13C relative to Picea abies roots and litter, and mycorrhizal fungal mycelium. Root-fungal feeders Tylenchidae had δ15N values similar to those of earthworms, enchytraeids and Entomobrya collembolans, but slightly lower δ13C values. Bacterivorous Plectidae were either equal or enriched in 15N compared with saprophagous macroinvertebrates and most mesofauna species. Omnivorous Dorylaimida and predatory Mononchida were further enriched in 15N and their isotopic signature was similar to that of predatory arthropods. These data confirm a clear separation of

  8. Diversity has stronger top-down than bottom-up effects on decomposition.

    Science.gov (United States)

    Srivastava, Diane S; Cardinale, Bradley J; Downing, Amy L; Duffy, J Emmett; Jouseau, Claire; Sankaran, Mahesh; Wright, Justin P

    2009-04-01

    The flow of energy and nutrients between trophic levels is affected by both the trophic structure of food webs and the diversity of species within trophic levels. However, the combined effects of trophic structure and diversity on trophic transfer remain largely unknown. Here we ask whether changes in consumer diversity have the same effect as changes in resource diversity on rates of resource consumption. We address this question by focusing on consumer-resource dynamics for the ecologically important process of decomposition. This study compares the top-down effect of consumer (detritivore) diversity on the consumption of dead organic matter (decomposition) with the bottom-up effect of resource (detrital) diversity, based on a compilation of 90 observations reported in 28 studies. We did not detect effects of either detrital or consumer diversity on measures of detrital standing stock, and effects on consumer standing stock were equivocal. However, our meta-analysis indicates that reductions in detritivore diversity result in significant reductions in the rate of decomposition. Detrital diversity has both positive and negative effects on decomposition, with no overall trend. This difference between top-down and bottom-up effects of diversity is robust to different effect size metrics and could not be explained by differences in experimental systems or designs between detritivore and detrital manipulations. Our finding that resource diversity has no net effect on consumption in "brown" (detritus-consumer) food webs contrasts with previous findings from "green" (plant-herbivore) food webs and suggests that effects of plant diversity on consumption may fundamentally change after plant death.

  9. Ecotoxicological evaluation of four UV filters using marine organisms from different trophic levels Isochrysis galbana, Mytilus galloprovincialis, Paracentrotus lividus, and Siriella armata.

    Science.gov (United States)

    Paredes, E; Perez, S; Rodil, R; Quintana, J B; Beiras, R

    2014-06-01

    Due to the concern about the negative effects of exposure to sunlight, combinations of UV filters like 4-Methylbenzylidene-camphor (4-MBC), Benzophenone-3 (BP-3), Benzophenone-4 (BP-4) and 2-Ethylhexyl-4-methoxycinnamate (EHMC) are being introduced in all kind of cosmetic formulas. These chemicals are acquiring a concerning status due to their increasingly common use and the potential risk for the environment. The aim of this study is to assess the behaviour of these compounds in seawater, the toxicity to marine organisms from three trophic levels including autotrophs (Isochrysis galbana), herbivores (Mytilus galloprovincialis and Paracentrotus lividus) and carnivores (Siriella armata), and set a preliminary assessment of potential ecological risk of UV filters in coastal ecosystems. In general, EC50 results show that both EHMC and 4-MBC are the most toxic for our test species, followed by BP-3 and finally BP-4. The most affected species by the presence of these UV filters are the microalgae I. galbana, which showed toxicity thresholds in the range of μg L(-1) units, followed by S. armata>P. Lividus>M. galloprovincialis. The UV filter concentrations measured in the sampled beach water were in the range of tens or even hundreds of ng L(-1). The resulting risk quotients showed appreciable environmental risk in coastal environments for BP-3 and 4-MBC. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Reorganization of a marine trophic network along an inshore-offshore gradient due to stronger pelagic-benthic coupling in coastal areas

    Science.gov (United States)

    Kopp, Dorothée; Lefebvre, Sébastien; Cachera, Marie; Villanueva, Maria Ching; Ernande, Bruno

    2015-01-01

    Recent theoretical considerations have highlighted the importance of the pelagic-benthic coupling in marine food webs. In continental shelf seas, it was hypothesized that the trophic network structure may change along an inshore-offshore gradient due to weakening of the pelagic-benthic coupling from coastal to offshore areas. We tested this assumption empirically using the eastern English Channel (EEC) as a case study. We sampled organisms from particulate organic matter to predatory fishes and used baseline-corrected carbon and nitrogen stable isotope ratios (δ13C and δ15N) to determine their trophic position. First, hierarchical clustering on δ13C and δ15N coupled to bootstrapping and estimates of the relative contribution of pelagic and benthic carbon sources to consumers' diet showed that, at mesoscale, the EEC food web forms a continuum of four trophic levels with trophic groups spread across a pelagic and a benthic trophic pathway. Second, based on the same methods, a discrete approach examined changes in the local food web structure across three depth strata in order to investigate the inshore-offshore gradient. It showed stronger pelagic-benthic coupling in shallow coastal areas mostly due to a reorganization of the upper consumers relative to the two trophic pathways, benthic carbon sources being available to pelagic consumers and, reciprocally, pelagic sources becoming accessible to benthic species. Third a continuous approach examined changes in the mean and variance of upper consumers' δ13C and δ15N with depth. It detected a significant decrease in δ13C variance and a significant increase in δ15N variance as depth increases. A theoretical two-source mixing model showed that an inshore-offshore decrease in the pelagic-benthic coupling was a sufficient condition to produce the δ13C variance pattern, thus supporting the conclusions of the discrete approach. These results suggest that environmental gradients such as the inshore-offshore one should

  11. Trophic and neurotrophic factors in human pituitary adenomas (Review).

    Science.gov (United States)

    Spoletini, Marialuisa; Taurone, Samanta; Tombolini, Mario; Minni, Antonio; Altissimi, Giancarlo; Wierzbicki, Venceslao; Giangaspero, Felice; Parnigotto, Pier Paolo; Artico, Marco; Bardella, Lia; Agostinelli, Enzo; Pastore, Francesco Saverio

    2017-10-01

    The pituitary gland is an organ that functionally connects the hypothalamus with the peripheral organs. The pituitary gland is an important regulator of body homeostasis during development, stress, and other processes. Pituitary adenomas are a group of tumors arising from the pituitary gland: they may be subdivided in functional or non-functional, depending on their hormonal activity. Some trophic and neurotrophic factors seem to play a key role in the development and maintenance of the pituitary function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. Several lines of evidence suggest that trophic and neurotrophic factors may be involved in pituitary function, thus suggesting a possible role of the trophic and neurotrophic factors in the normal development of pituitary gland and in the progression of pituitary adenomas. Additional studies might be necessary to better explain the biological role of these molecules in the development and progression of this type of tumor. In this review, in light of the available literature, data on the following neurotrophic factors are discussed: ciliary neurotrophic factor (CNTF), transforming growth factors β (TGF‑β), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), vascular endothelial growth inhibitor (VEGI), fibroblast growth factors (FGFs) and epidermal growth factor (EGF) which influence the proliferation and growth of pituitary adenomas.

  12. Trophic Effects of Mesenchymal Stem Cells in Chondrocyte Co-Cultures are Independent of Culture Conditions and Cell Sources

    NARCIS (Netherlands)

    Wu, Ling; Prins, H.J.; Helder, M.; van Blitterswijk, Clemens; Karperien, Hermanus Bernardus Johannes

    2012-01-01

    Earlier, we have shown that the increased cartilage production in pellet co-cultures of chondrocytes and bone marrow-derived mesenchymal stem cells (BM-MSCs) is due to a trophic role of the MSC in stimulating chondrocyte proliferation and matrix production rather than MSCs actively undergoing

  13. Trophic effects of mesenchymal stem cells in chondrocyte co-cultures are independent of culture conditions and cell sources

    NARCIS (Netherlands)

    Wu, L.; Prins, H.J.; Helder, M.N.; van Blitterswijk, C.A.; Karperien, M.

    2012-01-01

    Earlier, we have shown that the increased cartilage production in pellet co-cultures of chondrocytes and bone marrow-derived mesenchymal stem cells (BM-MSCs) is due to a trophic role of the MSC in stimulating chondrocyte proliferation and matrix production rather than MSCs actively undergoing

  14. Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach.

    Science.gov (United States)

    Boxhammer, Tim; Taucher, Jan; Bach, Lennart T; Achterberg, Eric P; Algueró-Muñiz, María; Bellworthy, Jessica; Czerny, Jan; Esposito, Mario; Haunost, Mathias; Hellemann, Dana; Ludwig, Andrea; Yong, Jaw C; Zark, Maren; Riebesell, Ulf; Anderson, Leif G

    2018-01-01

    Ongoing acidification of the ocean through uptake of anthropogenic CO2 is known to affect marine biota and ecosystems with largely unknown consequences for marine food webs. Changes in food web structure have the potential to alter trophic transfer, partitioning, and biogeochemical cycling of elements in the ocean. Here we investigated the impact of realistic end-of-the-century CO2 concentrations on the development and partitioning of the carbon, nitrogen, phosphorus, and silica pools in a coastal pelagic ecosystem (Gullmar Fjord, Sweden). We covered the entire winter-to-summer plankton succession (100 days) in two sets of five pelagic mesocosms, with one set being CO2 enriched (~760 μatm pCO2) and the other one left at ambient CO2 concentrations. Elemental mass balances were calculated and we highlight important challenges and uncertainties we have faced in the closed mesocosm system. Our key observations under high CO2 were: (1) A significantly amplified transfer of carbon, nitrogen, and phosphorus from primary producers to higher trophic levels, during times of regenerated primary production. (2) A prolonged retention of all three elements in the pelagic food web that significantly reduced nitrogen and phosphorus sedimentation by about 11 and 9%, respectively. (3) A positive trend in carbon fixation (relative to nitrogen) that appeared in the particulate matter pool as well as the downward particle flux. This excess carbon counteracted a potential reduction in carbon sedimentation that could have been expected from patterns of nitrogen and phosphorus fluxes. Our findings highlight the potential for ocean acidification to alter partitioning and cycling of carbon and nutrients in the surface ocean but also show that impacts are temporarily variable and likely depending upon the structure of the plankton food web.

  15. Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach.

    Directory of Open Access Journals (Sweden)

    Tim Boxhammer

    Full Text Available Ongoing acidification of the ocean through uptake of anthropogenic CO2 is known to affect marine biota and ecosystems with largely unknown consequences for marine food webs. Changes in food web structure have the potential to alter trophic transfer, partitioning, and biogeochemical cycling of elements in the ocean. Here we investigated the impact of realistic end-of-the-century CO2 concentrations on the development and partitioning of the carbon, nitrogen, phosphorus, and silica pools in a coastal pelagic ecosystem (Gullmar Fjord, Sweden. We covered the entire winter-to-summer plankton succession (100 days in two sets of five pelagic mesocosms, with one set being CO2 enriched (~760 μatm pCO2 and the other one left at ambient CO2 concentrations. Elemental mass balances were calculated and we highlight important challenges and uncertainties we have faced in the closed mesocosm system. Our key observations under high CO2 were: (1 A significantly amplified transfer of carbon, nitrogen, and phosphorus from primary producers to higher trophic levels, during times of regenerated primary production. (2 A prolonged retention of all three elements in the pelagic food web that significantly reduced nitrogen and phosphorus sedimentation by about 11 and 9%, respectively. (3 A positive trend in carbon fixation (relative to nitrogen that appeared in the particulate matter pool as well as the downward particle flux. This excess carbon counteracted a potential reduction in carbon sedimentation that could have been expected from patterns of nitrogen and phosphorus fluxes. Our findings highlight the potential for ocean acidification to alter partitioning and cycling of carbon and nutrients in the surface ocean but also show that impacts are temporarily variable and likely depending upon the structure of the plankton food web.

  16. Assessment of The trophic state and Chlorophyll-a concentrations using Landsat OLI in Karaoun reservoir, Lebanon

    Directory of Open Access Journals (Sweden)

    Ali Fadel

    2016-12-01

    Full Text Available Fadel, A., Faour G. and Slim K. 2016. Assessment of the trophic state and chlorophyll-a concentrations using Landsat OLI in Karaoun reservoir, Lebanon. Lebanese Science Journal, 17(2: 130-145. Harmful algal blooms have become a worldwide environmental problem. A regular and cost-effective monitoring of these blooms is highly needed by lakes managers. Satellite remote sensing imagery like Landsat Operational Land Imager (OLI can be used to assess and monitor chlorophyll-a in water bodies over large areas in a cost-effective way. In this study, the accuracy of Landsat OLI to estimate chlorophyll-a was examined. Four field campaigns and cloud free images of Landsat OLI with 30 m resolution (01 May 2013, 21 August 2013, 10 July 2015, and 11 August 2015 were used in this study to determine the accuracy of Landsat OLI in estimating chlorophyll-a in a 12 km2 freshwater body, Karaoun reservoir. After atmospheric correction of these images, reflectance of single and multiple band combinations were compared to field chlorophyll-a data. Results of field campaigns showed that the trophic state of Karaoun reservoir is still eutrophic to hypereutrophic with high nutrient concentration and low phytoplankton biodiversity, dominated by cyanobacteria species, Microcystis aeruginosa and Aphanizomenon ovalisporum. On single band level, the in situ chlorophyll-a measurement correlated best with band 5 (0.85 - 0.88 µm, with R=0.75 and R2=0.57. Highest correlation (R=0.84 and R2=0.72 was obtained using band combination, B2:B4 band ratio multiplied by B5. Results indicated that Landsat OLI can be used effectively to determine chlorophyll-a concentration in lakes and reservoirs. We recommend the application of Landsat OLI as a satisfactory and cost effective method for monitoring chlorophyll-a in other lakes through-out the world

  17. Trophic ecology of deep-sea Asteroidea (Echinodermata) from eastern Canada

    Science.gov (United States)

    Gale, Katie S. P.; Hamel, Jean-François; Mercier, Annie

    2013-10-01

    Asteroids (sea stars) can be important predators in benthic communities and are often present in ecologically important and vulnerable deep-sea coral and sponge habitats. However, explicit studies on the trophic ecology of deep-sea asteroids are rare. We investigated the diets of seven species of deep-sea asteroid from the bathyal zone of Newfoundland and Labrador, eastern Canada. A multifaceted approach including live animal observations, stomach content analysis, and stable isotope analysis revealed the asteroids to be either top predators of megafauna or secondary consumers (mud ingesters, infaunal predators, and suspension feeders). The stable isotope signatures of Ceramaster granularis, Hippasteria phrygiana, and Mediaster bairdi are characteristic of high-level predators, having δ15N values 4.4‰ (more than one trophic level) above Ctenodiscus crispatus, Leptychaster arcticus, Novodinia americana, and Zoroaster fulgens. We present strong evidence that corals and sponges are common food items for two of the predatory species, C. granularis and H. phrygiana. During laboratory feeding trials, live H. phrygiana fed on several species of soft coral and C. granularis fed on sponges. Stomach content analysis of wild-caught individuals revealed sclerites from sea pens (e.g. Pennatula sp.) in the stomachs of both asteroid species; H. phrygiana also contained sclerites from at least two other species of octocoral and siliceous sponge spicules were present in the stomachs of C. granularis. The stomach contents of the secondary consumers contained a range of invertebrate material. Leptychaster arcticus and Ctenodiscus crispatus feed infaunally on bulk sediment and molluscs, Zoroaster fulgens is a generalist infaunal predator, and the brisingid Novodinia americana is a specialist suspension feeder on benthopelagic crustaceans. This study provides a foundation for understanding the ecological roles of bathyal asteroids, and suggests that some species may have the

  18. Temporal changes in periphytic meiofauna in lakes of different trophic states

    Directory of Open Access Journals (Sweden)

    Kurt Pettersson

    2012-01-01

    Full Text Available Meiofaunal organisms in the periphyton of stony hard-substrates (epilithon were studied in three Swedish lakes with different trophic states (oligo-, meso- and eutrophic with respect to seasonal successions in abundance, biomass, and production. Over a period of 2 years, the meiofaunal population of all three lakes fluctuated greatly, with densities varying up to nine-fold within a season. In the oligotrophic lake, a significant decrease in meiofauna in winter was striking, whereas in the other two lakes, richer in nutrients, there was a pronounced peak in early summer. Although the lakes, on average, did not differ in epilithic organic and inorganic material, the differences in meiofaunal abundance, biomass, and production were significant. Correlation analysis revealed that altogether the meiofaunal biomass was positively related to the lakes’ trophic state (total phosphorus, while the meiofaunal abundance and production along the trophic spectrum displayed a humped-shape distribution, with maximum values measured in the mesotrophic Lake Erken (1324 ind cm-2 and 2249 mg DW cm-2 y-1. Nematodes were the dominant meiofaunal group in the epilithon of all three lakes, accounting for up to 58% in abundance, 33% in biomass and 55% in production of the whole meiofaunal community. However, their relative importance tended to decrease with increasing trophic state. Beside nematodes, rotifers, oligochaetes, copepods and tardigrades were also found in large numbers in the epilithon. Overall, the results demonstrated that, due to their high abundance, biomass, and production, meiofaunal organisms play an important role in epilithic communities.

  19. Modelling exposure of oceanic higher trophic-level consumers to polychlorinated biphenyls: pollution 'hotspots' in relation to mass mortality events of marine mammals.

    Science.gov (United States)

    Handoh, Itsuki C; Kawai, Toru

    2014-08-30

    Marine mammals in the past mass mortality events may have been susceptible to infection because their immune systems were suppressed through the bioaccumulation of environmental pollutants such as polychlorinated biphenyls (PCBs). We compiled mortality event data sets of 33 marine mammal species, and employed a Finely-Advanced Transboundary Environmental model (FATE) to model the exposure of the global fish community to PCB congeners, in order to define critical exposure levels (CELs) of PCBs above which mass mortality events are likely to occur. Our modelling approach enabled us to describe the mass mortality events in the context of exposure of higher-trophic consumers to PCBs and to identify marine pollution 'hotspots' such as the Mediterranean Sea and north-western European coasts. We demonstrated that the CELs can be applied to quantify a chemical pollution Planetary Boundary, under which a safe operating space for marine mammals and humanity can exist. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Vacuum therapy of trophic ulcer of lower extremities, presented in patients with DFS

    Directory of Open Access Journals (Sweden)

    Yurkova R.A.

    2017-01-01

    Full Text Available the article has analyzed the results of treatment of 67 patients with diabetic foot syndrome (DFS, complicated by feet trophic ulcers, using the vacuum bandages. Patients were divided into 2 groups: the control group had a traditional treatment and the studied one had vacuum bandages applied to the trophic ulcers. The results confirmed an assured decrease in the duration of patients’ treatment and hospitalization in the hospital.

  1. Trophic transfer potential of two different crystalline phases of TiO2 NPs from Chlorella sp. to Ceriodaphnia dubia.

    Science.gov (United States)

    Iswarya, V; Bhuvaneshwari, M; Chandrasekaran, N; Mukherjee, Amitava

    2018-04-01

    Owing to the increase in the usage of titanium dioxide nanoparticles (TiO 2 NPs), their release into the aquatic environment is inevitable. In the aquatic ecosystem, TiO 2 NPs can bio-magnify at various trophic levels in the food chain through dietary exposure. In the current study, the trophic transfer potential of two crystalline phases of TiO 2, anatase and rutile nanoparticles (individual as well as a binary mixture) has been evaluated in the lake water matrix using algae-daphnia system. Chlorella sp. and Ceriodaphnia dubia were used as test organisms to represent the algae-daphnia food chain of the freshwater ecosystem. Other than crystallinity, the effect of irradiation (visible and UV-A) was also investigated at the test concentrations, 75, 300, and 1200 μM. TiO 2 NPs treated algal diet produced significant mortality only at the test concentrations, 300 and 1200 μM. The type of irradiation and crystallinity doesn't have any impact on the mortality of daphnids through the dietary exposure of TiO 2 NPs. Comparing the mixture with individual NPs, binary mixture induced less mortality on C. dubia which signifies the antagonistic effect of NPs when they coexist. Statistical modeling confirmed the antagonistic effect of the binary mixture on C. dubia. As individual NPs, anatase and rutile forms showed a maximum Ti accumulation under UV-A and visible irradiation, respectively. BMF of TiO 2 NPs has been in validation with the bioaccumulation noted in C. dubia. Individual NPs (75 μM) showed higher BMF value of ∼23 under both UV-A (anatase) and visible (rutile) irradiation. Individual NPs showing higher BMF confirmed their trophic transfer potential in the aquatic food chain, primarily through the diet. In contrast, the binary mixture obtained a higher BMF of 1.9 and 0.79 at 75 and 300 μM under visible and UV-A irradiation, respectively. The plausible reason behind this decrement was the antagonistic effect of the mixture which significantly reduced

  2. Ecotoxicity assessment at three tropical levels

    International Nuclear Information System (INIS)

    Chen, S.S.; Siti Aishah Asmah Yusob; Wan Mazlina Wan Hussein; Izham Bakar; Zulkarnain Abdullah

    2001-01-01

    Several ecotoxicity test methods have been standardised to ensure international acceptance of data for predicting environmental risk of chemical substances. Test organism, concentration exposure duration, and end point effects are fundamental consideration in these methods. While concentration-exposure and end-point effect such as 96 LC 50 are easily decided, the choice of test organism species is more complex. The aquatic ecosystem for example is teemed with multitude of species that may show differing response to the same toxicant or pollutant. The basic tests recommended by OECD includes three functionally important types of organisms namely alga, daphnia, and fish that represent three trophical levels. Alga presenting the phytoplankton level is food to daphnia, a zooplankton that is in turn food to fishes. Daphnia species hardly thrives in the tropical environment and is replaced instead by Moina sp. of the same Cladoceran order. The sensitivity of the three types of organisms differs. The LC 50 /EC 50 values of cadmium chloride for tilapia, moina macrocopa and chlorella vulgaris (alga) range from 30 mg/1 to 0.2 mg/1 with moina macrocopa being the most sensitive. The least resistant species is not necessarily at the lowest trophical level. Tests on industrial effluents gave similar trends. Wastewater from an industrial drain that received discharge from chemical-based industries generated the lowest EC 50 for moina macrocopa at 0.1%, algae at 0.3% and tilapia at 2.4%. Effluent from a paper processing factory however did not yield any EC 50 value for moina while fish and alga had LC 50 and EC 50 values of 44% and 0.005%, respectively. The trends of acute toxicity tests on fish, moina and alga illustrate the necessity of conducting ecotoxicological testings on at least these three trophical levels. Assessment can be made based on the most sensitive species to ensure protection of the ecosystem through conservation of the food chain cycle. (Author)

  3. Trophic enrichment factors for blood serum in the European badger (Meles meles.

    Directory of Open Access Journals (Sweden)

    David J Kelly

    Full Text Available Ecologists undertaking stable isotopic analyses of animal diets require trophic enrichment factors (TEFs for the specific animal tissues that they are studying. Such basic data are available for a small number of species, so values from trophically or phylogenetically similar species are often substituted for missing values. By feeding a controlled diet to captive European badgers (Meles meles we determined TEFs for carbon and nitrogen in blood serum. TEFs for nitrogen and carbon in blood serum were +3.0 ± 0.4‰ and +0.4 ± 0.1‰ respectively. The TEFs for serum in badgers are notably different from those published for the red fox (Vulpes vulpes. There is currently no data for TEFs in the serum of other mustelid species. Our data show that species sharing similar niches (red fox do not provide adequate proxy values for TEFs of badgers. Our findings emphasise the importance of having species-specific data when undertaking trophic studies using stable isotope analysis.

  4. Temporal variability of biodiversity patterns and trophic structure of estuarine macrobenthic assemblages along a gradient of metal contamination

    KAUST Repository

    Piló, D.

    2015-06-01

    The present study aimed to investigate the response of macrobenthic assemblages along a gradient of metal contamination using a combination of uni- and multivariate methods focusing on their composition, structure and function. A total of six sites were established based on a preliminary survey, which identified three areas with different levels of contamination. These areas were defined as slightly contaminated (SC), moderately contaminated (MC) and highly contaminated (HC). Each area comprised two sites, sampled in four sampling surveys (September 2012, February, May and October of 2013). To investigate the response of the macrobenthic assemblages the number of individuals (N), number of taxa (S), Shannon-Weaver diversity (H\\'), Pielou\\'s equitability (J\\') and different distance-based multivariate measures of β-diversity (complementarity) were analysed. β-diversity as turnover was also analysed together with spatial and temporal changes in the trophic structure. A clear gradient of increasing contamination was consistently detected, but comparisons with available sediment quality guidelines indicated that adverse biological effects may be expected in all areas. This result suggests measuring concentrations of contaminants in the sediment per se may be insufficient to establish a clear link between ecological patterns and the contamination of the system. Also it highlights the difficulty of identifying reference areas in highly urbanized and industrialized estuaries. Only multivariate analysis (dbRDA; both using the taxonomic and trophic composition) and β-diversity as turnover showed a consistent response to metal contamination. Higher heterogeneity, mainly due to contribution of rare species (i.e. species present in a single sampling period), was observed in the least contaminated area (SC), decreasing towards the HC. In terms of the trophic function, a shift from a dominance of carnivores in the SC to the dominance of deposit-feeding organisms (and

  5. Temporal variability of biodiversity patterns and trophic structure of estuarine macrobenthic assemblages along a gradient of metal contamination

    KAUST Repository

    Piló , D.; Pereira, F.; Carriç o, A.; Curdia, Joao; Pereira, P.; Gaspar, M. B.; Gaspar, M. B.; Carvalho, Susana

    2015-01-01

    The present study aimed to investigate the response of macrobenthic assemblages along a gradient of metal contamination using a combination of uni- and multivariate methods focusing on their composition, structure and function. A total of six sites were established based on a preliminary survey, which identified three areas with different levels of contamination. These areas were defined as slightly contaminated (SC), moderately contaminated (MC) and highly contaminated (HC). Each area comprised two sites, sampled in four sampling surveys (September 2012, February, May and October of 2013). To investigate the response of the macrobenthic assemblages the number of individuals (N), number of taxa (S), Shannon-Weaver diversity (H'), Pielou's equitability (J') and different distance-based multivariate measures of β-diversity (complementarity) were analysed. β-diversity as turnover was also analysed together with spatial and temporal changes in the trophic structure. A clear gradient of increasing contamination was consistently detected, but comparisons with available sediment quality guidelines indicated that adverse biological effects may be expected in all areas. This result suggests measuring concentrations of contaminants in the sediment per se may be insufficient to establish a clear link between ecological patterns and the contamination of the system. Also it highlights the difficulty of identifying reference areas in highly urbanized and industrialized estuaries. Only multivariate analysis (dbRDA; both using the taxonomic and trophic composition) and β-diversity as turnover showed a consistent response to metal contamination. Higher heterogeneity, mainly due to contribution of rare species (i.e. species present in a single sampling period), was observed in the least contaminated area (SC), decreasing towards the HC. In terms of the trophic function, a shift from a dominance of carnivores in the SC to the dominance of deposit-feeding organisms (and

  6. Trophic structure and biomass distribution of macrobenthos on ...

    African Journals Online (AJOL)

    The trophic structure and biomass of macrobenthos on both wave-sheltered, rocky intertidal shores and semi-exposed ones at seven localities in the Tsitsikamma Marine Protected Area were compared. In the Cochlear zone and entire intertidal (Cochlear- and Balanoid zones combined) biomass values of invertebrates and ...

  7. Trophic linkage of a temperate intertidal macrobenthic food web under opportunistic macroalgal blooms: A stable isotope approach

    International Nuclear Information System (INIS)

    Park, Hyun Je; Han, Eunah; Lee, Young-Jae; Kang, Chang-Keun

    2016-01-01

    The effects of blooms of opportunistic green macroalgae, Ulva prolifera, on the trophic structure of the macrobenthic food web in a temperate intertidal zone on the western coast of Korea were evaluated using carbon and nitrogen stable isotopes. Biomasses of Ulva and microphytobenthos (MPB) increased significantly at the macroalgae-bloom and the non-bloom sites, respectively, from March to September 2011. The δ 13 C values of most the consumers were arrayed between those of MPB and Ulva at both sites, and differed according to feeding strategies at the macroalgae-bloom site. Seasonally increasing magnitudes in δ 13 C and δ 15 N values of consumers were much steeper at the macroalgae-bloom site than at the non-bloom site. Our findings provide evidence that blooming green macroalgae play a significant role as a basal resource supporting the intertidal macrobenthic food web and their significance varies with feeding strategies of consumers as well as the resource availability. - Highlights: • Trophic effects of Ulva blooms on intertidal macrobenthic food web were evaluated. • Biomasses of Ulva increased at the macroalgae-bloom from March to September. • δ 13 C and δ 15 N values of consumers differed with feeding strategy and season. • Trophic significance of blooming macroalgae varies with feeding strategies of consumers. • Ulva blooms play a significant role as a basal resource supporting the intertidal food web.

  8. Evaluation on Biofilter in Recirculating Integrated Multi-Trophic Aquaculture

    Directory of Open Access Journals (Sweden)

    S. Sumoharjo

    2013-06-01

    Full Text Available Integrated multi-trophic aquaculture pays more attention as a bio-integrated food production system that serves as a model of sustainable aquaculture, minimizes waste discharge, increases diversity and yields multiple products. The objectives of this research were to analyze the efficiency of total ammonia nitrogen biofiltration and its effect on carrying capacity of fish rearing units. Pilot-scale bioreactor was designed with eight run-raceways (two meters of each that assembled in series. Race 1-3 were used to stock silky worm (Tubifex sp as detrivorous converter, then race 4-8 were used to plant three species of leaf-vegetable as photoautotrophic converters, i.e; spinach (Ipomoea reptana, green mustard (Brassica juncea and basil (Ocimum basilicum. The three plants were placed in randomized block design based on water flow direction. Mass balance of nutrient analysis, was applied to figure out the efficiency of bio-filtration and its effect on carrying capacity of rearing units. The result of the experiment showed that 86.5 % of total ammonia nitrogen removal was achieved in 32 days of culturing period. This efficiency able to support the carrying capacity of the fish tank up to 25.95 kg/lpm with maximum density was 62.69 kg/m3 of fish biomass productionDoi: http://dx.doi.org/10.12777/ijse.4.2.2013.80-85 [How to cite this article: Sumoharjo, S.  and Maidie, A. (2013. Evaluation on Biofilter in Recirculating Integrated Multi-Trophic Aquaculture.  International Journal of  Science and Engineering, 4(2,80-85. Doi: http://dx.doi.org/10.12777/ijse.4.2.2013.80-85

  9. Steroids in house sparrows (Passer domesticus): Effects of POPs and male quality signalling.

    Science.gov (United States)

    Nossen, Ida; Ciesielski, Tomasz M; Dimmen, Malene V; Jensen, Henrik; Ringsby, Thor Harald; Polder, Anuschka; Rønning, Bernt; Jenssen, Bjørn M; Styrishave, Bjarne

    2016-03-15

    At high trophic levels, environmental contaminants have been found to affect endocrinological processes. Less attention has been paid to species at lower trophic levels. The house sparrow (Passer domesticus) may be a useful model for investigating effects of POPs in mid-range trophic level species. In male house sparrows, ornamental traits involved in male quality signalling are important for female selection. These traits are governed by endocrinological systems, and POPs may therefore interfere with male quality signalling. The aim of the present study was to use the house sparrow as a mid-range trophic level model species to study the effects of environmental contaminants on endocrinology and male quality signalling. We analysed the levels of selected PCBs, PBDEs and OCPs and investigated the possible effects of these contaminants on circulating levels of steroid hormones (4 progestagens, 4 androgens and 3 estrogens) in male and female adult house sparrows from a population on the island Leka, Norway. Plasma samples were analysed for steroid hormones by GC-MS and liver samples were analysed for environmental contaminants by GC-ECD and GC-MS. In males, we also quantified ornament traits. It was hypothesised that POPs may have endocrine disrupting effects on the local house sparrow population and can thus interfere with the steroid hormone homeostasis. Among female house sparrows, bivariate correlations revealed negative relationships between POPs and estrogens. Among male sparrows, positive relationships between dihydrotestosterone levels and PCBs were observed. In males, positive relationships were also found between steroids and beak length, and between steroids and ornamental traits such as total badge size. This was confirmed by a significant OPLS model between beak length and steroids. Although sparrows are in the mid-range trophic levels, the present study indicates that POPs may affect steroid homeostasis in house sparrows, in particular for females. For

  10. Subcellular controls of mercury trophic transfer to a marine fish

    Energy Technology Data Exchange (ETDEWEB)

    Dang Fei [Department of Biology, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong); Wang Wenxiong, E-mail: wwang@ust.hk [Department of Biology, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong)

    2010-09-15

    Different behaviors of inorganic mercury [Hg(II)] and methylmercury (MeHg) during trophic transfer along the marine food chain have been widely reported, but the mechanisms are not fully understood. The bioavailability of ingested mercury, quantified by assimilation efficiency (AE), was investigated in a marine fish, the grunt Terapon jarbua, based on mercury subcellular partitioning in prey and purified subcellular fractions of prey tissues. The subcellular distribution of Hg(II) differed substantially among prey types, with cellular debris being a major (49-57% in bivalves) or secondary (14-19% in other prey) binding pool. However, MeHg distribution varied little among prey types, with most MeHg (43-79%) in heat-stable protein (HSP) fraction. The greater AEs measured for MeHg (90-94%) than for Hg(II) (23-43%) confirmed the findings of previous studies. Bioavailability of each purified subcellular fraction rather than the proposed trophically available metal (TAM) fraction could better elucidate mercury assimilation difference. Hg(II) associated with insoluble fraction (e.g. cellular debris) was less bioavailable than that in soluble fraction (e.g. HSP). However, subcellular distribution was shown to be less important for MeHg, with each fraction having comparable MeHg bioavailability. Subcellular distribution in prey should be an important consideration in mercury trophic transfer studies.

  11. Subcellular controls of mercury trophic transfer to a marine fish

    International Nuclear Information System (INIS)

    Dang Fei; Wang Wenxiong

    2010-01-01

    Different behaviors of inorganic mercury [Hg(II)] and methylmercury (MeHg) during trophic transfer along the marine food chain have been widely reported, but the mechanisms are not fully understood. The bioavailability of ingested mercury, quantified by assimilation efficiency (AE), was investigated in a marine fish, the grunt Terapon jarbua, based on mercury subcellular partitioning in prey and purified subcellular fractions of prey tissues. The subcellular distribution of Hg(II) differed substantially among prey types, with cellular debris being a major (49-57% in bivalves) or secondary (14-19% in other prey) binding pool. However, MeHg distribution varied little among prey types, with most MeHg (43-79%) in heat-stable protein (HSP) fraction. The greater AEs measured for MeHg (90-94%) than for Hg(II) (23-43%) confirmed the findings of previous studies. Bioavailability of each purified subcellular fraction rather than the proposed trophically available metal (TAM) fraction could better elucidate mercury assimilation difference. Hg(II) associated with insoluble fraction (e.g. cellular debris) was less bioavailable than that in soluble fraction (e.g. HSP). However, subcellular distribution was shown to be less important for MeHg, with each fraction having comparable MeHg bioavailability. Subcellular distribution in prey should be an important consideration in mercury trophic transfer studies.

  12. Description of the East Brazil Large Marine Ecosystem using a trophic model

    Directory of Open Access Journals (Sweden)

    Kátia M.F. Freire

    2008-09-01

    Full Text Available The objective of this study was to describe the marine ecosystem off northeastern Brazil. A trophic model was constructed for the 1970s using Ecopath with Ecosim. The impact of most of the forty-one functional groups was modest, probably due to the highly reticulated diet matrix. However, seagrass and macroalgae exerted a strong positive impact on manatee and herbivorous reef fishes, respectively. A high negative impact of omnivorous reef fishes on spiny lobsters and of sharks on swordfish was observed. Spiny lobsters and swordfish had the largest biomass changes for the simulation period (1978-2000; tunas, other large pelagics and sharks showed intermediate rates of biomass decline; and a slight increase in biomass was observed for toothed cetaceans, large carnivorous reef fishes, and dolphinfish. Recycling was an important feature of this ecosystem with low phytoplankton-originated primary production. The mean transfer efficiency between trophic levels was 11.4%. The gross efficiency of the fisheries was very low (0.00002, probably due to the low exploitation rate of most of the resources in the 1970s. Basic local information was missing for many groups. When information gaps are filled, this model may serve more credibly for the exploration of fishing policies for this area within an ecosystem approach.

  13. A trophic indicators toolbox for implementing an ecosystem approach in data-poor fisheries: the Algerian and Bou-Ismail Bay examples

    Directory of Open Access Journals (Sweden)

    Karim Babouri

    2014-03-01

    Full Text Available Over the past decade, the Algerian government has undertaken several incentives financed by state subsidies, via a range of development plans for fishing activities. Although these have led to the growth and modernization of the fishing fleet and the creation of various jobs, this increased fishing pressure has not maximized production as anticipated. In fact, catch is decreasing, and there are clear signs of stock overexploitation for several species, particularly sardines, for which catches have fallen dramatically. This study analyses the impact of fishing from an ecosystem perspective, with a view to the implementation of ecosystem approach to fishery management (EAFM at the level of Algerian fisheries. To this end, a series of trophic indicators are used. The analysis shows that ecosystems at both national level and in the Bou-Ismail Bay are excessively exploited, and are altered by overexploitation and probably eutrophication. This situation is demonstrated in particular by the decrease in the average trophic level of catch, which is synonymous with “Fishing Down Marine Food Webs” (FDMW.

  14. Trait-mediated trophic interactions: is foraging theory keeping up?

    Science.gov (United States)

    Railsback, Steven F; Harvey, Bret C

    2013-02-01

    Many ecologists believe that there is a lack of foraging theory that works in community contexts, for populations of unique individuals each making trade-offs between food and risk that are subject to feedbacks from behavior of others. Such theory is necessary to reproduce the trait-mediated trophic interactions now recognized as widespread and strong. Game theory can address feedbacks but does not provide foraging theory for unique individuals in variable environments. 'State- and prediction-based theory' (SPT) is a new approach that combines existing trade-off methods with routine updating: individuals regularly predict future food availability and risk from current conditions to optimize a fitness measure. SPT can reproduce a variety of realistic foraging behaviors and trait-mediated trophic interactions with feedbacks, even when the environment is unpredictable. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Trophic modeling of Eastern Boundary Current Systems: a review and prospectus for solving the “Peruvian Puzzle”

    Directory of Open Access Journals (Sweden)

    Marc H. Taylor

    2013-04-01

    Full Text Available Eastern Boundary Current systems (EBCSs are among the most productive fishing areas in the world. High primary and secondary productivity supports a large biomass of small planktivorous pelagic fish, “small pelagics”, which are important drivers of production to the entire system whereby they can influence both higher and lower trophic levels. Environmental variability causes changes in plankton (food quality and quantity, which can affect population sizes, distribution and domi-nance among small pelagics. This variability combined with impacts from the fishery complicate the development of management strategies. Consequently, much recent work has been in the development of multispecies trophic models to better understand interdependencies and system dynamics. Despite similarities in extent, structure and primary productivity between EBCSs, the Peruvian system greatly differs from the others in the magnitude of fish catches, due mainly to the incredible production of the anchovy Engraulis ringens. This paper reviews literature concerning EBCSs dynamics and the state-of-the-art in the trophic modeling of EBCSs. The objective is to critically analyze the potential of this approach for system understanding and management and to adapt existing steady-state models of the Peruvian system for use in (future dynamic simulations. A guideline for the construction of trophodynamic models is presented taking into account the important trophic and environmental interactions. In consideration of the importance of small pelagics for the system dynamics, emphasis is placed on developing appropriate model compartmentalization and spatial delineation that facilitates dynamic simulations. Methods of model validation to historical changes are presented to support hypotheses concerning EBCS dynamics and as a critical step to the development of predictive models. Finally, the identification of direct model links to easily obtainable abiotic parameters is

  16. Convergent, Parallel and Correlated Evolution of Trophic Morphologies in the Subfamily Schizothoracinae from the Qinghai-Tibetan Plateau

    Science.gov (United States)

    Qi, Delin; Chao, Yan; Guo, Songchang; Zhao, Lanying; Li, Taiping; Wei, Fulei; Zhao, Xinquan

    2012-01-01

    Schizothoracine fishes distributed in the water system of the Qinghai-Tibetan plateau (QTP) and adjacent areas are characterized by being highly adaptive to the cold and hypoxic environment of the plateau, as well as by a high degree of diversity in trophic morphology due to resource polymorphisms. Although convergent and parallel evolution are prevalent in the organisms of the QTP, it remains unknown whether similar evolutionary patterns have occurred in the schizothoracine fishes. Here, we constructed for the first time a tentative molecular phylogeny of the schizothoracine fishes based on the complete sequences of the cytochrome b gene. We employed this molecular phylogenetic framework to examine the evolution of trophic morphologies. We used Pagel's maximum likelihood method to estimate the evolutionary associations of trophic morphologies and food resource use. Our results showed that the molecular and published morphological phylogenies of Schizothoracinae are partially incongruent with respect to some intergeneric relationships. The phylogenetic results revealed that four character states of five trophic morphologies and of food resource use evolved at least twice during the diversification of the subfamily. State transitions are the result of evolutionary patterns including either convergence or parallelism or both. Furthermore, our analyses indicate that some characters of trophic morphologies in the Schizothoracinae have undergone correlated evolution, which are somewhat correlated with different food resource uses. Collectively, our results reveal new examples of convergent and parallel evolution in the organisms of the QTP. The adaptation to different trophic niches through the modification of trophic morphologies and feeding behaviour as found in the schizothoracine fishes may account for the formation and maintenance of the high degree of diversity and radiations in fish communities endemic to QTP. PMID:22470515

  17. Influence of rainfall on the trophic status of a brazilian semiarid reservoir - doi: 10.4025/actascibiolsci.v35i4.18261

    Directory of Open Access Journals (Sweden)

    Francisco Ítalo Barbosa Chaves

    2013-07-01

    Full Text Available This study evaluated the trophic conditions of the reservoir located in the urban perimeter of the town General Sampaio, semiarid region of the Ceará State, Brazil and its relationship with seasonal variation in rainfall between 2010 and 2011. It was obtained data for Secchi disk transparency, total phosphorus, and chlorophyll a to calculate the Trophic State Index (TSI, as well as rainfall data. The Trophic State Index (TSI proposed by Carlson (1977 and modified by Toledo Junior (1990 was used to test the influence of the seasonal variation in rainfall on hydrological variables and on trophic conditions of the reservoir in 2010 and 2011. There was seasonal variability in variables analyzed between climatic periods (rainy and dry and trophic conditions determined through the trophic index indicated conditions ranging from oligotrophic to eutrophic during the two years analyzed in this reservoir. Under these circumstances, one may conclude that the trophic status is related to seasonal fluctuations in the hydrology of the system controlled by rainfall, which is a common feature of semiarid regions.

  18. Trophic relationships of hake ( Merluccius capensis and M ...

    African Journals Online (AJOL)

    The trophic relationships of two hake species (Merluccius capensis and M. paradoxus) and three shark species (Centrophorus squamosus, Deania calcea and D. profundorum) were investigated using nitrogen and carbon stable isotope signatures (δ15N and δ13C) of their muscle tissues. The sharks were more enriched in ...

  19. Use of satellite imagery to assess the trophic state of Miyun Reservoir, Beijing, China

    International Nuclear Information System (INIS)

    Wang Zhengjun; Hong Jianming; Du Guisen

    2008-01-01

    The objective of this research is to explore an appropriate way of monitoring and assessing water quality by satellite remote sensing techniques in the Miyun reservoir of Beijing, China. Two scene Thematic Mapper images in May and October of 2003 were acquired and simultaneous in situ measurements, sampling and analysis were conducted. Statistical analysis indicates that satellite-based normalized ratio vegetation index (NRVI) and in situ measured water chlorophyll a (Chl-a) concentration have very high correlation. Two linear regression models with high determination coefficients were constructed for NRVI and Chl-a of sample points. According to the modified trophic state index map, water quality in the western section of Miyun reservoir was consistently higher than in the eastern section during the two months tested. The trophic grade of the eastern reservoir remained mesotrophic with a tendency for eutrophication. - Remote sensing techniques can effectively monitor the change of water quality with time and space

  20. Trophic structure of fish fauna along the longitudinal gradient of a first-order rural stream

    Directory of Open Access Journals (Sweden)

    Jardel Nimet

    2015-12-01

    Full Text Available Abstract Aim: This study evaluated the trophic structure of the fish assemblage along the longitudinal gradient of a first-order rural stream. Methods Fish were sampled by electrofishing technique in December 2007, September 2008 and March 2009, at three stretch of the Itiz stream (headwater, middle and mouth. We sampled 1,255 individuals relating to 18 species. The categorization of trophic guilds was based on stomach content data of 1,096 individuals, analyzed according to the volumetric method, except for four species, which were classified according to the literature. To test the hypothesis of differences in the richness, abundance and biomass of trophic guilds along the headwater-mouth gradient, it was performed non-parametric statistical analysis of the dietary data. Was also calculated, the amplitude of trophic niche (Levins's index for each guild. To summarize the composition and abundance of the trophic guilds along the longitudinal gradient, we applied a non-metric multidimensional scaling (NMDS. Results We registered seven guilds: herbivorous, detritivorous, aquatic insectivorous, terrestrial insectivorous, invertivorous, omnivorous and piscivorous, the latter was exclusive to headwater and middle stretches. The omnivorous guild was not recorded in the headwater. Through PERMANOVA analysis it was found that the species richness of more specialized guilds (detritivorous and insectivorous terrestrial and of generalist invertivorous increased, while less specialized guilds like aquatic insectivorous and herbivorous, decrease significantly in headwater-mouth direction. Except by the non-expected increase of insectivorous terrestrial and decrease of herbivorous downstream, the non-metric multidimensional scaling (NMDS identified longitudinal variations in abundance and biomass of the guilds that agree with general patterns of fish guilds distribution along environmental gradients. Conclusion These results suggest that the influence of

  1. Isotopic determination of the trophic ecology of a ubiquitous key species - The crab Liocarcinus depurator (Brachyura: Portunidae)

    Science.gov (United States)

    Careddu, Giulio; Calizza, Edoardo; Costantini, Maria Letizia; Rossi, Loreto

    2017-05-01

    Knowledge of the trophic ecology of predators is key to understanding how they affect food web structure and ecosystem functioning. The harbour crab Liocarcinus depurator (L.) (Brachyura: Portunidae) is one of the most abundant decapod species in soft-bottom areas of the Mediterranean Sea and northeast Atlantic Ocean. It is both a common prey and predator of commercial and non-commercial marine species and its predation pressure appears to have little effect on the subtidal community assemblage. However, there are few studies of its diet and little is known about its role in mediating energy flows in marine ecosystems. In this study, carbon (δ13C) and nitrogen (δ15N) stable isotope analysis (SIA) and Bayesian analytical tools were used to characterise the trophic niche of L. depurator and to quantify the most important prey supporting this species under various environmental conditions. Specimens of L. depurator, their potential prey and basal resources were collected from two different subtidal areas of the Gulf of Gaeta, one affected by human activities (north side) and the other seasonally influenced by freshwater inputs originating from the River Garigliano (south side). While there were differences between the two sampling areas in terms of the abundance and δ15N and δ13C values of the macrobenthic prey community, no differences in the δ15N values and trophic position of L. depurator were observed. Specifically, Bayesian mixing models showed Polychaeta Errantia as the main source of crab diets in both areas. The observed differences in the δ13C values and the analysis of trophic pathways also indicate that the terrestrial organic matter originating from the discharge of the River Garigliano was integrated along the food web up to L. depurator. Although this species is usually considered an opportunistic feeder, it appears to be highly selective and its trophic habits did not influence food web topology, which in contrast was found to be strongly

  2. Ecosystem differences in the trophic enrichment of 13C in aquatic food webs

    International Nuclear Information System (INIS)

    France, R.L.; Peters, R.H.

    1997-01-01

    Data from 35 published studies were collated to examine patterns in the trophic enrichment of 13 C of consumers. Because both δ 13 C and δ 14 N vary systematically across ecosystems, it was necessary to standardize for such differences before combining data from numerous sources. Relationships of these measures of ecosystem-standardized δ 13 C to ecosystem-standardized trophic position (Δδ 15 N) for freshwater, estuarine, coastal, and open-ocean and for all aquatic ecosystems yielded regression equations of low predictive capability (average of 20% explained variance in δ 13 C). However, differences were observed in the slopes between δ 13 C and standardized trophic position when data were examined study-specifically: the average trophic fractionation of 13 C was found to increase from +0.2micron for freshwater to +0.5micron for estuarine to +0.8micron for coastal, and to +1.1micron for open-ocean food webs. This ecosystem-specific gradient in 13 C enrichment for consumers supports previous findings of a similar continuum existing for zooplankton - particulate organic matter differences in δ 13 C. Possible mechanisms to explain these ecosystem-specific patterns in 13 C enrichment may be related to the relative importance of detritus, heterotrophic respiration, partial reliance on alternative food sources, and lipid influences in the different ecosystems. (author)

  3. Trophic relationships between macroinvertebrates and fish in a pampean lowland stream (Argentina

    Directory of Open Access Journals (Sweden)

    María V. López van Oosterom

    2013-03-01

    Full Text Available The diet and trophic relationships between the macroinvertebrates Phyllogomphoides joaquini Rodrigues Capítulo, 1992 and Coenagrionidae (Odonata, Chironomidae (Diptera, Diplodon delodontus (Lamarck, 1919 (Bivalvia: Hyriidae, and Pomacea canaliculata (Lamarck, 1822 (Gastropoda: Ampulariidae and the fishes Pimelodella laticeps Eigenmann, 1917 (Heptapteridae and Bryconamericus iheringii (Boulenger, 1887 (Characidae in a temperate lowland lotic system in Argentina were assessed on the basis of gut contents and stable-isotope analyses. The feeding strategies were analyzed by the AMUNDSEN method. Relative food items contribution for the taxa studied indicated a generalist-type trophic strategy. In macroinvertebrates, in general, the values of stable isotope confirmed the result of the analysis of gut contents. With the fish, stable-isotope analysis demonstrated that both species are predators, although B. iheringii exhibited a more omnivorous behaviour. These feeding studies allowed us to determine the trophic relationships among taxa studied. Detritus and diatoms were a principal source of food for all the macroinvertebrates studied. In La Choza stream the particulate organic matter is a major no limited food resource, has a significant influence upon the community.

  4. Ecosystem approach to fisheries: Exploring environmental and trophic effects on Maximum Sustainable Yield (MSY reference point estimates.

    Directory of Open Access Journals (Sweden)

    Rajeev Kumar

    Full Text Available We present a comprehensive analysis of estimation of fisheries Maximum Sustainable Yield (MSY reference points using an ecosystem model built for Mille Lacs Lake, the second largest lake within Minnesota, USA. Data from single-species modelling output, extensive annual sampling for species abundances, annual catch-survey, stomach-content analysis for predatory-prey interactions, and expert opinions were brought together within the framework of an Ecopath with Ecosim (EwE ecosystem model. An increase in the lake water temperature was observed in the last few decades; therefore, we also incorporated a temperature forcing function in the EwE model to capture the influences of changing temperature on the species composition and food web. The EwE model was fitted to abundance and catch time-series for the period 1985 to 2006. Using the ecosystem model, we estimated reference points for most of the fished species in the lake at single-species as well as ecosystem levels with and without considering the influence of temperature change; therefore, our analysis investigated the trophic and temperature effects on the reference points. The paper concludes that reference points such as MSY are not stationary, but change when (1 environmental conditions alter species productivity and (2 fishing on predators alters the compensatory response of their prey. Thus, it is necessary for the management to re-estimate or re-evaluate the reference points when changes in environmental conditions and/or major shifts in species abundance or community structure are observed.

  5. Assessing Trophic Position and Mercury Accumulation in Sanpping Turtles

    Science.gov (United States)

    This study determined the trophic position and the total mercury concentrations of snapping turtles (Chelydra serpentina) captured from 26 freshwater sites in Rhode Island. Turtles were captured in baited wire cages, and a non-lethal sampling technique was used in which tips of ...

  6. Trophic ecology and food consumption of fishes in a hypersaline tropical lagoon.

    Science.gov (United States)

    Almeida-Silva, P H; Tubino, R A; Zambrano, L C; Hunder, D A; Garritano, S R; Monteiro-Neto, C

    2015-06-01

    This study evaluated the trophic ecology (diet composition, trophic strategy, similarities and overlap between species, feeding period and food consumption) of six benthivorous fish species in Araruama Lagoon, the largest hypersaline tropical lagoon on the east coast of South America, with an area of 210 km(2) and an average salinity of 52. The burrfish Chilomycterus spinosus fed on Anomalocardia flexuosa shell deposits, ingesting associated fauna. The caitipa mojarra Diapterus rhombeus differed from all other species, having not only the highest proportions of algae and Nematoda, but also feeding on polychaete tentacles. The two mojarras Eucinostomus spp. showed similar trophic strategies, feeding mostly on Polychaeta. The corocoro grunt Orthopristis ruber also fed mainly on Polychaeta, but differed from Eucinostomus spp. in secondary items. The whitemouth croacker Micropogonias furnieri fed mainly on small Crustacea at night, showing a high number of secondary prey items with low frequencies and high prey-specific abundance. The daily food consumption (g food g(-1) fish mass) for Eucinostomus argenteus was 0·012 and was 0·031 and 0·027 for M. furnieri in two different sampling events. The diet similarities between Araruama Lagoon and other brackish and marine environments indicate that hypersalinity is not a predominant factor shaping the trophic ecology of fishes in this lagoon. The stability of hypersaline conditions, without a pronounced gradient, may explain the presence of several euryhaline fishes and invertebrates well adapted to this condition, resulting in a complex food web. © 2015 The Fisheries Society of the British Isles.

  7. Diet and trophic niche of Lithobates catesbeianus (Amphibia: Anura

    Directory of Open Access Journals (Sweden)

    Peterson T. Leivas

    2012-10-01

    Full Text Available Lithobates catesbeianus (Shaw, 1802 is an invasive anuran introduced in Brazil that is associated with the displacement and the decline of populations of native species worldwide. There is evidence that biological invasions are facilitated by certain attributes of the invading species, for instance niche breath, and that invasive species have a broader ecological niche with respect to native ones. We designed a study to ascertain the temporal, ontogenetic, and sex differences in the niche dynamics of the American bullfrog. We sampled monthly from June 2008 to May 2009 in the state of Paraná, southern Brazil. For each individual, we gathered biometric and stomach content data. We then estimated the niche breath of the juveniles and adults, and compared it between the sexes. A total of 104 females and 77 males were sampled. Lithobates catesbeianus has a generalist diet, preying upon invertebrates and vertebrates. Even though the diet of the studied population varied seasonally, it did not differ between the sexes nor did it respond to biometric variables. Niche breadth was more restricted in the winter than in the autumn. The trophic niche of juveniles and adults did not overlap much when compared with the trophic niche overlap between males and females. Adult males and females had a considerable niche overlap, but females had a broader trophic niche than males in the winter and in the spring. These niche characteristics point to an opportunistic predation strategy that may have facilitated the process of invasion and establishment of this species in the study area.

  8. Short Communication: Growth of seaweed Eucheuma cottonii in multi trophic sea farming systems at Gerupuk Bay, Central Lombok, Indonesia

    Directory of Open Access Journals (Sweden)

    SUKIMAN

    2014-05-01

    Full Text Available Sukiman, Faturrahman, Rohyani IS, Ahyadi H. 2014. Growth of seaweed Eucheuma cottonii in multi trophic sea farming systems at Gerupuk Bay, Central Lombok, Indonesia. Nusantara Bioscience 6: 82-85. Eucheuma cottonii is a seaweed commodity that has a high economic value because it contains compounds used as raw materials for industries. Various methods of seaweed farming have been developed, one of which is a system of cultivation Multi Trophic Sea Farming. This study aimed to analyze the growth of E. cottonii by observing the production of biomass in four trophic combinations in the system Multi Trophic Sea Farming. The study was conducted in the area of the marine aquaculture Gerupuk bay, Central Lombok, Indonesia. Experiments were performed on four plots cages with trophic combination treatment as follows: K1 (E. cottonii-lobster-abalone, K2 (E. cottonii-abalone-red carp, K3 (E. cottonii-abalone-grouper, and K4 (E. cottonii-abalone-pomfret fish. Seedling of E. cottonii weighing 50 g was tied to a rope and placed at a depth of 5 cm, 50 cm, 100 cm and 150 cm. Measurement of biomass production was done every ten days until the thirtieth day. The highest biomass production of E. cottonii was obtained in K3 trophic combination (E. cottonii-abalone-grouper fish with a depth of seedlings of 5 cm. The combination of K3 trophic is recommended for cultivation of seaweed in the MTSF system.

  9. Fatty acid biomarkers: validation of food web and trophic markers using C-13-labelled fatty acids in juvenile sandeel ( Ammodytes tobianus )

    DEFF Research Database (Denmark)

    Dalsgaard, Anne Johanne Tang; St. John, Michael

    2004-01-01

    A key issue in marine science is parameterizing trophic interactions in marine food webs, thereby developing an understanding of the importance of top-down and bottom-up controls on populations of key trophic players. This study validates the utility of fatty acid food web and trophic markers usi......), respectively. Lack of temporal trends in nonlabelled fatty acids confirmed the conservative incorporation of labelled fatty acids by the fish.......A key issue in marine science is parameterizing trophic interactions in marine food webs, thereby developing an understanding of the importance of top-down and bottom-up controls on populations of key trophic players. This study validates the utility of fatty acid food web and trophic markers using...... C-13-labelled fatty acids to verify the conservative incorporation of fatty acid tracers by juvenile sandeel (Ammodytes tobianus) and assess their uptake, clearance, and metabolic turnover rates. Juvenile sandeel were fed for 16 days in the laboratory on a formulated diet enriched in (13)C16...

  10. Predatory fishes affect trophic cascades and apparent competition in temperate reefs.

    Science.gov (United States)

    Frid, Alejandro; Marliave, Jeff

    2010-08-23

    We provide evidence for a trophic cascade involving apex predators and mesopredators of marine temperate reefs, lingcod and rockfish, respectively. We measured spatio-temporal variation in the relative abundance of lingcod, subadult rockfish and two shrimp groups eaten by rockfish (Pandalus sp. and three smaller-bodied genera aggregated). Lingcod had an indirect positive effect on shrimps, as mediated by the direct negative effects of lingcod on rockfish and of rockfish on shrimps. These top-down effects on shrimps, however, were stronger for Pandalus than for small-bodied shrimps. Further, abundances of Pandalus and small-bodied shrimps were negatively correlated and the latter had a stronger positive effect on rockfish, suggesting that rockfish mediated asymmetrical apparent competition between shrimps. Our results indicate mechanisms by which predatory fishes may influence the structure of marine communities.

  11. The trophic ecology of key megafaunal species at the Pakistan Margin: Evidence from stable isotopes and lipid biomarkers

    Science.gov (United States)

    Jeffreys, Rachel M.; Wolff, George A.; Murty, Sarah J.

    2009-10-01

    The Arabian Sea is subject to intense seasonality resulting from biannual monsoons, which lead to associated large particulate fluxes and an abundance of organic carbon, a potential food source at the seafloor for benthic detritivores. We used the stable isotopes of carbon and nitrogen alongside lipid analyses to examine potential food sources (particulate and sedimentary organic matter, POM and SOM respectively) in order to determine trophic linkages for the twelve most abundant megafaunal species ( Pontocaris sp., Solenocera sp., Munidopsis aff. scobina, Actinoscyphia sp., Actinauge sp., Echinoptilum sp., Pennatula aff. grandis, Astropecten sp. Amphiura sp. Ophiura euryplax, Phormosoma placenta and Hyalinoecia sp.) at the Pakistan Margin between 140 and 1400 m water depth. This transect spans a steep gradient in oxygen concentrations and POM flux. Ranges of δ 13C and δ 15N values were narrow in POM and SOM (˜4‰ and ˜2‰ for δ 13C and δ 15N, respectively) with little evidence of temporal variability. Labile lipid compounds in SOM originating from phytoplankton did exhibit seasonal change in their concentrations at the shallowest sites, 140 and 300 m. Benthic megafauna had broad ranges in δ 13C and δ 15N (>10‰ and >8‰ for δ 13C and δ 15N, respectively) suggesting they occupy several trophic levels and utilize a variety of food sources. There is evidence for feeding niche separation between and within trophic groups. Lipid biomarkers in animal tissues indicate a mixture of food sources originating from both phytoplankton (C 20:5(n-3) and C 22:6(n-3)) and invertebrate prey (C 20:1 and C 22:1). Biomarkers originating from phytodetritus are conserved through trophic transfer to the predator/scavengers. Six species ( Pontocaris sp., Solenocera sp., Actinoscyphia sp., Echinoptilum sp., Amphiura sp. and Hyalinoecia sp.) showed a significant biochemical response to the seasonal supply of food and probably adapt their trophic strategy to low food

  12. A guideline to study the feasibility domain of multi-trophic and changing ecological communities.

    Science.gov (United States)

    Song, Chuliang; Rohr, Rudolf P; Saavedra, Serguei

    2018-04-24

    The feasibility domain of an ecological community can be described by the set of environmental abiotic and biotic conditions under which all co-occurring and interacting species in a given site and time can have positive abundances. Mathematically, the feasibility domain corresponds to the parameter space compatible with positive (feasible) solutions at equilibrium for all the state variables in a system under a given model of population dynamics. Under specific dynamics, the existence of a feasible equilibrium is a necessary condition for species persistence regardless of whether the feasible equilibrium is dynamically stable or not. Thus, the size of the feasibility domain can also be used as an indicator of the tolerance of a community to random environmental variations. This has motivated a rich research agenda to estimate the feasibility domain of ecological communities. However, these methodologies typically assume that species interactions are static, or that input and output energy flows on each trophic level are unconstrained. Yet, this is different to how communities behave in nature. Here, we present a step-by-step quantitative guideline providing illustrative examples, computational code, and mathematical proofs to study systematically the feasibility domain of ecological communities under changes of interspecific interactions and subject to different constraints on the trophic energy flows. This guideline covers multi-trophic communities that can be formed by any type of interspecific interactions. Importantly, we show that the relative size of the feasibility domain can significantly change as a function of the biological information taken into consideration. We believe that the availability of these methods can allow us to increase our understanding about the limits at which ecological communities may no longer tolerate further environmental perturbations, and can facilitate a stronger integration of theoretical and empirical research. Copyright

  13. Context-Specific Trophic and Functional Ecology of Fishes of Small Stream Ecosystems in the Ouachita National Forest

    Science.gov (United States)

    William J. Matthews; A. Maria Miller-Lemke; Melvin L. Warren; Donna Cobb; Jeffery G. Stewart; Betty Crump; Frances P. Gelwick

    2004-01-01

    Abstract - Fish play diverse and important roles in stream ecosystems, but details about ecosystem effects are poorly known for many freshwater fish species. A requisite first step to understanding functional roles of individual species is information on their trophic ecology in the context of particular environmental settings. Stomach contents were...

  14. Chemical elements in pearl oysters (Paxyodon ponderosus), phytoplankton and estuarine sediments from eastern Amazon (Northern Brazil): Bioaccumulation factors and trophic transfer factors

    Science.gov (United States)

    Vilhena, Maria P. S. P.; Costa, Marcondes L.; Berrêdo, José F.; Paiva, Rosildo S.; Souza, Crisvaldo C. S.

    2016-04-01

    The current study was conducted near Barcarena County, which is a mid-sized urban center where aluminum ore processing industries (bauxite) and Vila do Conde cargo terminal are located. It aims to discuss the bioaccumulation factors as well as factors related to the trophic transfer of chemical elements in water, oyster, phytoplankton and bottom sediments from an estuary in the Brazilian Northern coast. The bioaccumulation factor (BAF), trophic transfer factor (TTF) and biota-sediment-water were used to correlate the contents of chemical elements found in organisms. The sediment, surface water, phytoplankton and pearl oysters chemical composition was analyzed by ICP-OES and ICP-MS. Pearl oysters showed K, Ca, Mg, P, Mn, Fe, Zn, Al, Ba and Pb accumulation, which concentration increase is associated with their diet (phytoplankton). Al concentrations are 14 times higher in pearl oysters (Paxyodon ponderosus), assuming that they are associated with wastewater emissions and with industrialization processes in the area. BAF and BSAF values are 1000 times higher than the metal concentrations in water and bioavailable fraction concentrations. The oyster-phytoplankton trophic transfer factor indicates that P, Ba, Ca, Na, Cd and Zn showed the largest transfers (from 5 to 19). These trophic transfers may be sufficient to cause significant ecotoxicological effects on the region biota.

  15. Trophic Cascades Induced by Lobster Fishing Are Not Ubiquitous in Southern California Kelp Forests

    Science.gov (United States)

    Guenther, Carla M.; Lenihan, Hunter S.; Grant, Laura E.; Lopez-Carr, David; Reed, Daniel C.

    2012-01-01

    Fishing can trigger trophic cascades that alter community structure and dynamics and thus modify ecosystem attributes. We combined ecological data of sea urchin and macroalgal abundance with fishery data of spiny lobster (Panulirus interruptus) landings to evaluate whether: (1) patterns in the abundance and biomass among lobster (predator), sea urchins (grazer), and macroalgae (primary producer) in giant kelp forest communities indicated the presence of top-down control on urchins and macroalgae, and (2) lobster fishing triggers a trophic cascade leading to increased sea urchin densities and decreased macroalgal biomass. Eight years of data from eight rocky subtidal reefs known to support giant kelp forests near Santa Barbara, CA, USA, were analyzed in three-tiered least-squares regression models to evaluate the relationships between: (1) lobster abundance and sea urchin density, and (2) sea urchin density and macroalgal biomass. The models included reef physical structure and water depth. Results revealed a trend towards decreasing urchin density with increasing lobster abundance but little evidence that urchins control the biomass of macroalgae. Urchin density was highly correlated with habitat structure, although not water depth. To evaluate whether fishing triggered a trophic cascade we pooled data across all treatments to examine the extent to which sea urchin density and macroalgal biomass were related to the intensity of lobster fishing (as indicated by the density of traps pulled). We found that, with one exception, sea urchins remained more abundant at heavily fished sites, supporting the idea that fishing for lobsters releases top-down control on urchin grazers. Macroalgal biomass, however, was positively correlated with lobster fishing intensity, which contradicts the trophic cascade model. Collectively, our results suggest that factors other than urchin grazing play a major role in controlling macroalgal biomass in southern California kelp forests, and

  16. Global change in the trophic functioning of marine food webs

    DEFF Research Database (Denmark)

    Maureaud, Aurore; Gascuel, Didier; Colléter, Mathieu

    2017-01-01

    and life history traits of marine species, we tested the hypothesis that anthropogenic ecological impacts may have led to changes in the global parameters defining the transfers of biomass within the food web. First, we developed two indicators to assess such changes: the Time Cumulated Indicator (TCI......The development of fisheries in the oceans, and other human drivers such as climate warming, have led to changes in species abundance, assemblages, trophic interactions, and ultimately in the functioning of marine food webs. Here, using a trophodynamic approach and global databases of catches......) measuring the residence time of biomass within the food web, and the Efficiency Cumulated Indicator (ECI) quantifying the fraction of secondary production reaching the top of the trophic chain. Then, we assessed, at the large marine ecosystem scale, the worldwide change of these two indicators over the 1950...

  17. Predicting species distribution and abundance responses to climate change: why it is essential to include biotic interactions across trophic levels.

    Science.gov (United States)

    Van der Putten, Wim H; Macel, Mirka; Visser, Marcel E

    2010-07-12

    Current predictions on species responses to climate change strongly rely on projecting altered environmental conditions on species distributions. However, it is increasingly acknowledged that climate change also influences species interactions. We review and synthesize literature information on biotic interactions and use it to argue that the abundance of species and the direction of selection during climate change vary depending on how their trophic interactions become disrupted. Plant abundance can be controlled by aboveground and belowground multitrophic level interactions with herbivores, pathogens, symbionts and their enemies. We discuss how these interactions may alter during climate change and the resulting species range shifts. We suggest conceptual analogies between species responses to climate warming and exotic species introduced in new ranges. There are also important differences: the herbivores, pathogens and mutualistic symbionts of range-expanding species and their enemies may co-migrate, and the continuous gene flow under climate warming can make adaptation in the expansion zone of range expanders different from that of cross-continental exotic species. We conclude that under climate change, results of altered species interactions may vary, ranging from species becoming rare to disproportionately abundant. Taking these possibilities into account will provide a new perspective on predicting species distribution under climate change.

  18. Trophic-functional patterns of biofilm-dwelling ciliates at different water depths in coastal waters of the Yellow Sea, northern China.

    Science.gov (United States)

    Abdullah Al, Mamun; Gao, Yangyang; Xu, Guangjian; Wang, Zheng; Warren, Alan; Xu, Henglong

    2018-04-01

    Vertical variations in trophic-functional patterns of biofilm-dwelling ciliates were studied in coastal waters of the Yellow Sea, northern China. A total of 50 species were identified and assigned to four trophic-functional groups (TFgrs): algivores (A), bacterivorous (B), non-selective (N) and raptors (R). The trophic-functional structures of the ciliate communities showed significant variability among different water depths: (1) with increasing water depth, relative species numbers and relative abundances of groups A and R decreased sharply whereas those of groups B and N increased gradually; (2) in terms of the frequency of occurrences, group A dominated at depths of 1-3.5 m whereas group B dominated at 5 m, while in terms of the probability density function of the trophic-functional spectrum, group A was the highest contributor at 1 m and group B was highest at the other three depths; (3) distance-based redundancy analyses revealed significant differences in trophic-functional patterns among the four depths, except between 2 and 3.5 m (P > 0.05); and (4) the trophic-functional trait diversity increased from 1 to 3.5 m and decreased sharply at 5 m. Our results suggest that the biofilm-dwelling ciliates maintain a stable trophic-functional pattern and high biodiversity at depths of 1-3.5 m. Copyright © 2018 Elsevier GmbH. All rights reserved.

  19. Integrated Multi-Trophic Recirculating Aquaculture System for Nile Tilapia (Oreochlomis niloticus

    Directory of Open Access Journals (Sweden)

    Puchong Sri-uam

    2016-06-01

    Full Text Available Three densities of the sex-reversed male Nile tilapia, Oreochromis niloticus (20, 25, 50 fish/m3 were cultivated in an integrated multi-trophic recirculating aquaculture system (IMRAS that involves the ecological relationship between several living organisms, i.e., phytoplankton, zooplankton, and aquatic plants. The results indicated that, by providing proper interdependency between various species of living organisms, the concentrations of ammonia, nitrite, nitrate, and phosphate in the system were maintained below dangerous levels for Nile tilapia throughout the cultivation period. The highest wet weight productivity of Nile tilapia of 11 ± 1 kg was achieved at a fish density of 50 fish/m3. The aquatic plants in the treatment tank could effectively uptake the unwanted nitrogen (N and phosphorus (P compounds with the highest removal efficiencies of 9.52% and 11.4%, respectively. The uptake rates of nitrogen and phosphorus by aquatic plants could be ranked from high to low as: Egeria densa > Ceratophyllum demersum > Vallisneria spiralis and Vallisneria americana > Hygrophila difformis. The remaining N was further degraded through nitrification process, whereas the remaining P could well precipitate in the soil sediment in the treatment tank.

  20. Trophic specialization drives morphological evolution in sea snakes.

    Science.gov (United States)

    Sherratt, Emma; Rasmussen, Arne R; Sanders, Kate L

    2018-03-01

    Viviparous sea snakes are the most rapidly speciating reptiles known, yet the ecological factors underlying this radiation are poorly understood. Here, we reconstructed dated trees for 75% of sea snake species and quantified body shape (forebody relative to hindbody girth), maximum body length and trophic diversity to examine how dietary specialization has influenced morphological diversification in this rapid radiation. We show that sea snake body shape and size are strongly correlated with the proportion of burrowing prey in the diet. Specialist predators of burrowing eels have convergently evolved a 'microcephalic' morphotype with dramatically reduced forebody relative to hindbody girth and intermediate body length. By comparison, snakes that predominantly feed on burrowing gobies are generally short-bodied and small-headed, but there is no evidence of convergent evolution. The eel specialists also exhibit faster rates of size and shape evolution compared to all other sea snakes, including those that feed on gobies. Our results suggest that trophic specialization to particular burrowing prey (eels) has invoked strong selective pressures that manifest as predictable and rapid morphological changes. Further studies are needed to examine the genetic and developmental mechanisms underlying these dramatic morphological changes and assess their role in sea snake speciation.

  1. Fish mitigate trophic depletion in marine cave ecosystems.

    Science.gov (United States)

    Bussotti, Simona; Di Franco, Antonio; Bianchi, Carlo Nike; Chevaldonné, Pierre; Egea, Lea; Fanelli, Emanuela; Lejeusne, Christophe; Musco, Luigi; Navarro-Barranco, Carlos; Pey, Alexis; Planes, Serge; Vieux-Ingrassia, Jean Vincent; Guidetti, Paolo

    2018-06-15

    Dark marine habitats are often characterized by a food-limited condition. Peculiar dark habitats include marine caves, characterized by the absence of light and limited water flow, which lead to reduced fluxes of organic matter for cave-dwelling organisms. We investigated whether the most abundant and common cave-dwelling fish Apogon imberbis has the potential to play the role of trophic vector in Mediterranean marine caves. We first analysed stomach contents to check whether repletion changes according to a nycthemeral cycle. We then identified the prey items, to see whether they belong to species associated with cave habitats or not. Finally, we assessed whether A. imberbis moves outside marine caves at night to feed, by collecting visual census data on A. imberbis density both inside and outside caves, by day and by night. The stomach repletion of individuals sampled early in the morning was significantly higher than later in the day. Most prey were typical of habitats other than caves. A. imberbis was on average more abundant within caves during the day and outside during the night. Our study supports the hypothesis regarding the crucial trophic role of A. imberbis in connecting Mediterranean marine caves with external habitats.

  2. Effect of stock size, climate, predation, and trophic status on recruitment of alewives in Lake Ontario, 1978-2000

    Science.gov (United States)

    O'Gorman, Robert; Lantry, Brian F.; Schneider, Clifford P.

    2004-01-01

    The population of alewives Alosa pseudoharengus in Lake Ontario is of great concern to fishery managers because alewives are the principal prey of introduced salmonines and because alewives negatively influence many endemic fishes. We used spring bottom trawl catches of alewives to investigate the roles of stock size, climate, predation, and lake trophic status on recruitment of alewives to age 2 in Lake Ontario during 1978–2000. Climate was indexed from the temperature of water entering a south-shore municipal treatment plant, lake trophic status was indexed by the mean concentration of total phosphorus (TP) in surface water in spring, and predation was indexed by the product of the number of salmonines stocked and relative, first-year survival of Chinook salmonOncorhynchus tshawytscha. A Ricker-type parent–progeny model suggested that peak production of age-1 alewives could occur over a broad range of spawning stock sizes, and the fit of the model was improved most by the addition of terms for spring water temperature and winter duration. With the addition of the two climate terms, the Ricker model indicated that when water was relatively warm in spring and the winter was relatively short, peak potential production of young was nine times higher than when water temperature and winters were average, and 73 times higher than when water was cold in spring and winters were long. Relative survival from age 1 to recruitment at age 2 was best described by a multiple linear regression with terms for adult abundance, TP, and predation. Mean recruitment of age-2 fish in the 1978–1998 year-classes predicted by using the two models in sequence was only about 20% greater than the observed mean recruitment. Model estimates fit the measured data exceptionally well for all but the largest four year-classes, which suggests that the models will facilitate improvement in estimates of trophic transfer due to alewives.

  3. Trophic niche shifts driven by phytoplankton in sandy beach ecosystems

    Science.gov (United States)

    Bergamino, Leandro; Martínez, Ana; Han, Eunah; Lercari, Diego; Defeo, Omar

    2016-10-01

    Stable isotopes (δ13C and δ15N) together with chlorophyll a and densities of surf diatoms were used to analyze changes in trophic niches of species in two sandy beaches of Uruguay with contrasting morphodynamics (i.e. dissipative vs. reflective). Consumers and food sources were collected over four seasons, including sediment organic matter (SOM), suspended particulate organic matter (POM) and the surf zone diatom Asterionellopsis guyunusae. Circular statistics and a Bayesian isotope mixing model were used to quantify food web differences between beaches. Consumers changed their trophic niche between beaches in the same direction of the food web space towards higher reliance on surf diatoms in the dissipative beach. Mixing models indicated that A. guyunusae was the primary nutrition source for suspension feeders in the dissipative beach, explaining their change in dietary niche compared to the reflective beach where the proportional contribution of surf diatoms was low. The high C/N ratios in A. guyunusae indicated its high nutritional value and N content, and may help to explain the high assimilation by suspension feeders at the dissipative beach. Furthermore, density of A. guyunusae was higher in the dissipative than in the reflective beach, and cell density was positively correlated with chlorophyll a only in the dissipative beach. Therefore, surf diatoms are important drivers in the dynamics of sandy beach food webs, determining the trophic niche space and productivity. Our study provides valuable insights on shifting foraging behavior by beach fauna in response to changes in resource availability.

  4. Trophic effects of adipose-tissue-derived and bone-marrow-derived mesenchymal stem cells enhance cartilage generation by chondrocytes in co-culture.

    Science.gov (United States)

    Pleumeekers, M M; Nimeskern, L; Koevoet, J L M; Karperien, M; Stok, K S; van Osch, G J V M

    2018-01-01

    Combining mesenchymal stem cells (MSCs) and chondrocytes has great potential for cell-based cartilage repair. However, there is much debate regarding the mechanisms behind this concept. We aimed to clarify the mechanisms that lead to chondrogenesis (chondrocyte driven MSC-differentiation versus MSC driven chondroinduction) and whether their effect was dependent on MSC-origin. Therefore, chondrogenesis of human adipose-tissue-derived MSCs (hAMSCs) and bone-marrow-derived MSCs (hBMSCs) combined with bovine articular chondrocytes (bACs) was compared. hAMSCs or hBMSCs were combined with bACs in alginate and cultured in vitro or implanted subcutaneously in mice. Cartilage formation was evaluated with biochemical, histological and biomechanical analyses. To further investigate the interactions between bACs and hMSCs, (1) co-culture, (2) pellet, (3) Transwell® and (4) conditioned media studies were conducted. The presence of hMSCs-either hAMSCs or hBMSCs-increased chondrogenesis in culture; deposition of GAG was most evidently enhanced in hBMSC/bACs. This effect was similar when hMSCs and bAC were combined in pellet culture, in alginate culture or when conditioned media of hMSCs were used on bAC. Species-specific gene-expression analyses demonstrated that aggrecan was expressed by bACs only, indicating a predominantly trophic role for hMSCs. Collagen-10-gene expression of bACs was not affected by hBMSCs, but slightly enhanced by hAMSCs. After in-vivo implantation, hAMSC/bACs and hBMSC/bACs had similar cartilage matrix production, both appeared stable and did not calcify. This study demonstrates that replacing 80% of bACs by either hAMSCs or hBMSCs does not influence cartilage matrix production or stability. The remaining chondrocytes produce more matrix due to trophic factors produced by hMSCs.

  5. Microbial Ecophysiology of Whey Biomethanation: Characterization of Bacterial Trophic Populations and Prevalent Species in Continuous Culture

    OpenAIRE

    Chartrain, M.; Zeikus, J. G.

    1986-01-01

    The organization and species composition of bacterial trophic groups associated with lactose biomethanation were investigated in a whey-processing chemostat by enumeration, isolation, and general characterization studies. The bacteria were spatially organized as free-living forms and as self-immobilized forms appearing in flocs. Three dominant bacterial trophic group populations were present (in most probable number per milliliter) whose species numbers varied with the substrate consumed: hyd...

  6. Model ecosystem approach to estimate community level effects of radiation

    Energy Technology Data Exchange (ETDEWEB)

    Masahiro, Doi; Nobuyuki, Tanaka; Shoichi, Fuma; Nobuyoshi, Ishii; Hiroshi, Takeda; Zenichiro, Kawabata [National Institute of Radiological Sciences, Environmental and Toxicological Sciences Research Group, Chiba (Japan)

    2004-07-01

    Mathematical computer model is developed to simulate the population dynamics and dynamic mass budgets of the microbial community realized as a self sustainable aquatic ecological system in the tube. Autotrophic algae, heterotrophic protozoa and sapro-trophic bacteria live symbiotically with inter-species' interactions as predator-prey relationship, competition for the common resource, autolysis of detritus and detritus-grazing food chain, etc. The simulation model is the individual-based parallel model, built in the demographic stochasticity, environmental stochasticity by dividing the aquatic environment into patches. Validity of the model is checked by the multifaceted data of the microcosm experiments. In the analysis, intrinsic parameters of umbrella endpoints (lethality, morbidity, reproductive growth, mutation) are manipulated at the individual level, and tried to find the population level, community level and ecosystem level disorders of ecologically crucial parameters (e.g. intrinsic growth rate, carrying capacity, variation, etc.) that related to the probability of population extinction. (author)

  7. Model ecosystem approach to estimate community level effects of radiation

    International Nuclear Information System (INIS)

    Masahiro, Doi; Nobuyuki, Tanaka; Shoichi, Fuma; Nobuyoshi, Ishii; Hiroshi, Takeda; Zenichiro, Kawabata

    2004-01-01

    Mathematical computer model is developed to simulate the population dynamics and dynamic mass budgets of the microbial community realized as a self sustainable aquatic ecological system in the tube. Autotrophic algae, heterotrophic protozoa and sapro-trophic bacteria live symbiotically with inter-species' interactions as predator-prey relationship, competition for the common resource, autolysis of detritus and detritus-grazing food chain, etc. The simulation model is the individual-based parallel model, built in the demographic stochasticity, environmental stochasticity by dividing the aquatic environment into patches. Validity of the model is checked by the multifaceted data of the microcosm experiments. In the analysis, intrinsic parameters of umbrella endpoints (lethality, morbidity, reproductive growth, mutation) are manipulated at the individual level, and tried to find the population level, community level and ecosystem level disorders of ecologically crucial parameters (e.g. intrinsic growth rate, carrying capacity, variation, etc.) that related to the probability of population extinction. (author)

  8. Trophic ecology of Atlantic Bluefin Tuna (Thunnus thynnus [corrected] larvae from the Gulf of Mexico and NW Mediterranean spawning grounds: A Comparative Stable Isotope Study.

    Directory of Open Access Journals (Sweden)

    Raúl Laiz-Carrión

    Full Text Available The present study uses stable isotopes of nitrogen and carbon (δ15Nandδ13C as trophic indicators for Atlantic bluefin tuna larvae (BFT (6-10 mm standard length in the highly contrasting environmental conditions of the Gulf of Mexico (GOM and the Balearic Sea (MED. These regions are differentiated by their temperature regime and relative productivity, with the GOM being significantly warmer and more productive. MED BFT larvae showed the highest δ15N signatures, implying an elevated trophic position above the underlying microzooplankton baseline. Ontogenetic dietary shifts were observed in the BFT larvae from the GOM and MED which indicates early life trophodynamics differences between these spawning habitats. Significant trophic differences between the GOM and MED larvae were observed in relation to δ15N signatures in favour of the MED larvae, which may have important implications in their growth during their early life stages.These low δ15N levels in the zooplankton from the GOM may be an indication of a shifting isotopic baseline in pelagic food webs due to diatrophic inputs by cyanobacteria. Lack of enrichment for δ15N in BFT larvae compared to zooplankton implies an alternative grazing pathway from the traditional food chain of phytoplankton-zooplankton-larval fish. Results provide insight for a comparative characterization of the trophic pathways variability of the two main spawning grounds for BFT larvae.

  9. Relationship between ecomorphology and trophic segregation in four closely related sympatric fish species (Teleostei, Sciaenidae).

    Science.gov (United States)

    Blasina, Gabriela; Molina, Juan; Lopez Cazorla, Andrea; Díaz de Astarloa, Juan

    This study explores the relationship between ecomorphology and trophic segregation in four closely related sympatric fish species (Teleostei, Sciaenidae) that are known to differ in their trophic habits. Only adult specimens were analyzed: 103 Cynoscion guatucupa, 77 Pogonias cromis, 61 Micropogonias furnieri, and 48 Menticirrhus americanus. The four species presented divergent ecomorphological traits related to swimming agility, prey spotting and capture, and the potential size of prey they were able to swallow. Results suggest that these sciaenid species can partition the food resources, even though they completely overlap in space. Differences in their ecomorphological traits appear to correlate closely with the diet and consequently could explain the trophic differentiation observed. Arguably, these ecomorphological differences play a significant role in the coexistence of the adults of these sympatric fish species. Copyright © 2016 Académie des sciences. Published by Elsevier SAS. All rights reserved.

  10. Trophic polymorphism, habitat and diet segregation in Percichthys trucha (Pisces : Percichthyidae) in the Andes

    DEFF Research Database (Denmark)

    Ruzzante, D.E.; Walde, S.J.; Cussac, V.E.

    1998-01-01

    Divergent natural selection affecting specific trait combinations that lead to greater efficiency in resource exploitation is believed to be a major mechanism leading to trophic polymorphism and adaptive radiation. We present evidence of trophic polymorphism involving two benthic morphs within...... Percichthys trucha, a fish endemic to temperate South America. In a series of lakes located in the southern Andes, we found two morphs of P. trucha that could be distinguished on the basis of gill raker length and five other morphological measures, most of which are likely associated with the use of food...

  11. Waste feed from coastal fish farms: A trophic subsidy with compositional side-effects for wild gadoids

    Science.gov (United States)

    Fernandez-Jover, Damian; Martinez-Rubio, Laura; Sanchez-Jerez, Pablo; Bayle-Sempere, Just T.; Lopez Jimenez, Jose Angel; Martínez Lopez, Francisco Javier; Bjørn, Pål-Arne; Uglem, Ingebrigt; Dempster, Tim

    2011-03-01

    Aquaculture of carnivorous fish species in sea-cages typically uses artificial feeds, with a proportion of these feeds lost to the surrounding environment. This lost resource may provide a trophic subsidy to wild fish in the vicinity of fish farms, yet the physiological consequences of the consumption of waste feed by wild fish remain unclear. In two regions in Norway with intensive aquaculture, we tested whether wild saithe ( Pollachius virens) and Atlantic cod ( Gadus morhua) associated with fish farms (F assoc), where waste feed is readily available, had modified diets, condition and fatty acid (FA) compositions in their muscle and liver tissues compared to fish unassociated (UA) with farms. Stomach content analyses revealed that both cod and saithe consumed waste feed in the vicinity of farms (6-96% of their diet was composed of food pellets). This translated into elevated body and liver condition compared to fish caught distant from farms for cod at both locations and elevated body condition for saithe at one of the locations. As a consequence of a modified diet, we detected significantly increased concentrations of terrestrial-derived fatty acids (FAs) such as linoleic (18:2ω6) and oleic (18:1ω9) acids and decreased concentrations of DHA (22:6ω3) in the muscle and/or liver of F assoc cod and saithe when compared with UA fish. In addition, the ω3:ω6 ratio clearly differed between F assoc and UA fish. Linear discriminant analysis (LDA) correctly classified 97% of fish into F assoc or UA origin for both cod and saithe based on the FA composition of liver tissues, and 89% of cod and 86% of saithe into F assoc or UA origin based on the FA composition of muscle. Thus, LDA appears a useful tool for detecting the influence of fish farms on the FA composition of wild fish. Ready availability of waste feed with high protein and fat content provides a clear trophic subsidy to wild fish in coastal waters, yet whether the accompanying side-effect of altered fatty

  12. Trait-mediated trophic interactions: is foraging theory keeping up?

    Science.gov (United States)

    Steven F. Railsback; Bret C. Harvey

    2013-01-01

    Many ecologists believe that there is a lack of foraging theory that works in community contexts, for populations of unique individuals each making trade-offs between food and risk that are subject to feedbacks from behavior of others. Such theory is necessary to reproduce the trait-mediated trophic interactions now recognized as widespread and strong. Game theory can...

  13. Phenotypic integration in a series of trophic traits: tracing the evolution of myrmecophagy in spiders (Araneae).

    Science.gov (United States)

    Pekár, Stano; Michalko, Radek; Korenko, Stanislav; Sedo, Ondřej; Líznarová, Eva; Sentenská, Lenka; Zdráhal, Zbyněk

    2013-02-01

    Several hypotheses have been put forward to explain the evolution of prey specificity (stenophagy). Yet little light has so far been shed on the process of evolution of stenophagy in carnivorous predators. We performed a detailed analysis of a variety of trophic adaptations in one species. Our aim was to determine whether a specific form of stenophagy, myrmecophagy, has evolved from euryphagy via parallel changes in several traits from pre-existing characters. For that purpose, we studied the trophic niche and morphological, behavioural, venomic and physiological adaptations in a euryphagous spider, Selamia reticulata. It is a species that is branching off earlier in phylogeny than stenophagous ant-eating spiders of the genus Zodarion (both Zodariidae). The natural diet was wide and included ants. Laboratory feeding trials revealed versatile prey capture strategies that are effective on ants and other prey types. The performance of spiders on two different diets - ants only and mixed insects - failed to reveal differences in most fitness components (survival and developmental rate). However, the weight increase was significantly higher in spiders on the mixed diet. As a result, females on a mixed diet had higher fecundity and oviposited earlier. No differences were found in incubation period, hatching success or spiderling size. S. reticulata possesses a more diverse venom composition than Zodarion. Its venom is more effective for the immobilisation of beetle larvae than of ants. Comparative analysis of morphological traits related to myrmecophagy in the family Zodariidae revealed that their apomorphic states appeared gradually along the phylogeny to derived prey-specialised genera. Our results suggest that myrmecophagy has evolved gradually from the ancestral euryphagous strategy by integrating a series of trophic traits. Copyright © 2012 Elsevier GmbH. All rights reserved.

  14. Trophic development in a volcanic lake with closed hydric balance. Lake Martignano

    International Nuclear Information System (INIS)

    Falleni, F.; Bruno, M.; Marchiori, E.; Congestri, R.; Gasperi, E.; Brambullo, M.; Amadeio, R.

    2000-01-01

    Martignano lake is a particular charming volcanic lake in the countryside of Rome. Recently it was included in a project of Regional Wildlife Park. The lack of immissaries and emissaries, the quite long renewal time and the very short homeothermic period of two-months in a year, make the lake susceptible of trophic evolution. The comparison between the present data and those from previous studies seems to confirm such a slow development towards this way, with a nutrient level (nitrate 0.97 mg/L; total phosphorus 11.14 μg/L) and chlorophyll a concentrations (10.68 μg/L), typical of mesotrophic waters. The analysis of nutrient data expressed as annual mean value in percentage from the coastal stations, suggests an under lied farming influence, and points out the need to adopt fast reduction measures, to lower the phosphorus load in acceptable levels for the lake ecosystem [it

  15. Assessment of trophic ecomorphology in non-alligatoroid crocodylians and its adaptive and taxonomic implications.

    Science.gov (United States)

    Iijima, Masaya

    2017-08-01

    Although the establishment of trophic ecomorphology in living crocodylians can contribute to estimating feeding habits of extinct large aquatic reptiles, assessment of ecomorphological traits other than the snout shape has scarcely been conducted in crocodylians. Here, I tested the validity of the proposed trophic ecomorphological traits in crocodylians by examining the correlation between those traits and the snout shape (an established trophic ecomorphology), using 10 non-alligatoroid crocodylian species with a wide range of snout shape. I then compared the ontogenetic scaling of trophic ecomorphology to discuss its adaptive and taxonomic significance. The results demonstrated that degree of heterodonty, tooth spacing, size of supratemporal fenestra (STF), ventral extension of pterygoid flange and length of lower jaw symphysis are significantly correlated with snout shape by both non-phylogenetic and phylogenetic regression analyses. Gavialis gangeticus falls outside of 95% prediction intervals for the relationships of some traits and the snout shape, suggesting that piscivorous specialization involves the deviation from the typical transformation axis of skull characters. The comparative snout shape ontogeny revealed a universal trend of snout widening through growth in the sampled crocodylians, implying the existence of a shared size-dependent biomechanical constraint in non-alligatoroid crocodylians. Growth patterns of other traits indicated that G. gangeticus shows atypical trends for degree of heterodonty, size of STF, and symphysis length, whereas the same trends are shared for tooth spacing and ventral extension of pterygoid flange among non-alligatoroid crocodylians. These suggest that some characters are ontogenetically labile in response to prey preference shifts through growth, but other characters are in keeping with the conserved biomechanics among non-alligatoroid crocodylians. Some important taxonomic characters such as the occlusal pattern are

  16. Trophic position of coexisting krill species: a stable isotope approach

    DEFF Research Database (Denmark)

    Agersted, Mette Dalgaard; Bode, Antonio; Nielsen, Torkel Gissel

    2014-01-01

    Four krill species with overlapping functional biology coexist in Greenland waters. Here, we used stable isotopes to investigate and discuss their trophic role and mode of coexistence. Bulk carbon (δ13C) and nitrogen (δ15N) stable isotope analyses of Thysanoessa longicaudata, T. inermis, T. raschii...

  17. Trophic interactions of the pelagic ecosystem over the Reykjanes Ridge as evaluated by fatty acid and stable isotope analyses

    Science.gov (United States)

    Petursdottir, H.; Gislason, A.; Falk-Petersen, S.; Hop, H.; Svavarsson, J.

    2008-01-01

    Trophic relationships of the important oceanic crustacean species Calanus finmarchicus, Meganyctiphanes norvegica and Sergestes arcticus, as well as the mesopelagic fishes Maurolicus muelleri, Benthosema glaciale and Sebastes mentella, were investigated over the Reykjanes Ridge in June 2003 and in June 2004. Measurements were performed of length, wet weight, dry weight, total lipid, lipid class, fatty acid and fatty alcohol profiles and stable isotopes (δ 13C and δ 15N). High amounts of the Calanus lipid markers, 20:1(n-9) and 22:1(n-11) in these species confirm the importance of Calanus spp. in this ecosystem. Comparisons of fatty acid/alcohol profiles by multivariate analysis revealed two main trophic pathways over the Reykjanes Ridge. In one pathway, Calanus spp. was an important part of the diet for the small mesopelagic fish species M. muelleri and B. glaciale and the shrimp S. arcticus, whereas in the other pathway, the euphausiid M. norvegica was the dominant food for the redfish S. mentella, and Calanus spp. were of less importance. M. muelleri and the smaller B. glaciale feed on C. finmarchicus, whereas the larger B. glaciale and S. arcticus select the larger, deeper-living C. hyperboreus. All investigated species are true pelagic species except for the shrimp S. arcticus, which seems to have a benthic feeding habit as well. The δ 15N levels show that of the species investigated, C. finmarchicus occupies the lowest trophic level (2.0) and the redfish, S. mentella, the highest (4.2). All the species were lipid rich, typical for subarctic pelagic ecosystem. Calanus finmarchicus, S. arcticus and B. glaciale store wax esters as their lipid stores, while M. norvegica, M. muelleri and S. mentella store triacylglycerols.

  18. Visualizing the Food-Web Effects of Fishing for Tunas in the Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Jefferson T. Hinke

    2004-06-01

    Full Text Available We use food-web models to develop visualizations to compare and evaluate the interactions of tuna fisheries with their supporting food webs in the eastern tropical Pacific (ETP and the central north Pacific (CNP Oceans. In the ETP and CNP models, individual fisheries use slightly different food webs that are defined by the assemblage of targeted tuna species. Distinct energy pathways are required to support different tuna species and, consequently, the specific fisheries that target different tuna assemblages. These simulations suggest that catches of tunas, sharks, and billfishes have lowered the biomass of the upper trophic levels in both systems, whereas increases in intermediate and lower trophic level animals have accompanied the decline of top predators. Trade-offs between fishing and predation mortality rates that occur when multiple fisheries interact with their respective food webs may lead to smaller changes in biomass than if only the effect of a single fishery is considered. Historical simulations and hypothetical management scenarios further demonstrate that the effects of longline and purse seine fisheries have been strongest in upper trophic levels, but that lower trophic levels may respond more strongly to purse-seine fisheries. The apex predator guild has responded most strongly to longlining. Simulations of alternative management strategies that attempt to rebuild shark and billfish populations in each ecosystem reveal that (1 changes in longlining more effectively recover top predator populations than do changes in purse seining and (2 restrictions on both shallow-set longline gear and shark finning may do more to recover top predators than do simple reductions in fishing effort.

  19. Analyzing the trophic link between the mesopelagic microbial loop and zooplankton from observed depth profiles of bacteria and protozoa

    Directory of Open Access Journals (Sweden)

    T. Tanaka

    2005-01-01

    Full Text Available It is widely recognized that organic carbon exported to the ocean aphotic layer is significantly consumed by heterotrophic organisms such as bacteria and zooplankton in the mesopelagic layer. However, very little is known for the trophic link between bacteria and zooplankton or the function of the microbial loop in this layer. In the northwestern Mediterranean, recent studies have shown that viruses, bacteria, heterotrophic nanoflagellates, and ciliates distribute down to 2000 m with group-specific depth-dependent decreases, and that bacterial production decreases with depth down to 1000 m. Here we show that such data can be analyzed using a simple steady-state food chain model to quantify the carbon flow from bacteria to zooplankton over the mesopelagic layer. The model indicates that bacterial mortality by viruses is similar to or 1.5 times greater than that by heterotrophic nanoflagellates, and that heterotrophic nanoflagellates transfer little of bacterial production to higher trophic levels.

  20. Trophic Diversity of Plankton in the Epipelagic and Mesopelagic Layers of the Tropical and Equatorial Atlantic Determined with Stable Isotopes

    Directory of Open Access Journals (Sweden)

    Antonio Bode

    2018-06-01

    Full Text Available Plankton living in the deep ocean either migrate to the surface to feed or feed in situ on other organisms and detritus. Planktonic communities in the upper 800 m of the tropical and equatorial Atlantic were studied using the natural abundance of stable carbon and nitrogen isotopes to identify their food sources and trophic diversity. Seston and zooplankton (>200 µm samples were collected with Niskin bottles and MOCNESS nets, respectively, in the epipelagic (0–200 m, upper mesopelagic (200–500 m, and lower mesopelagic layers (500–800 m at 11 stations. Food sources for plankton in the productive zone influenced by the NW African upwelling and the Canary Current were different from those in the oligotrophic tropical and equatorial zones. In the latter, zooplankton collected during the night in the mesopelagic layers was enriched in heavy nitrogen isotopes relative to day samples, supporting the active migration of organisms from deep layers. Isotopic niches showed also zonal differences in size (largest in the north, mean trophic diversity (largest in the tropical zone, food sources, and the number of trophic levels (largest in the equatorial zone. The observed changes in niche size and overlap (up to 71% between the mesopelagic layers but <50% between the epipelagic and upper mesopelagic layers support the prevalence of in situ feeding at deep layers in tropical and equatorial zooplankton.

  1. Mercury in the ecosystem of Admiralty Bay, King George Island, Antarctica: Occurrence and trophic distribution.

    Science.gov (United States)

    Cipro, Caio V Z; Montone, Rosalinda C; Bustamante, Paco

    2017-01-15

    Mercury (Hg) can reach the environment through natural and human-related sources, threatening ecosystems all over the planet due to its well known deleterious effects. Therefore, Antarctic trophic webs, despite being relatively isolated, are not exempt of its influence. To evaluate Hg concentrations in an Antarctic ecosystem, different tissues from 2 species of invertebrates, 2 of fish, 8 of birds, 4 of pinnipeds and at least 5 of vegetation were investigated (n=176). For animals, values ranged from 0.018 to 48.7μgg -1 dw (whole Antarctic krill and Antarctic Fur Seal liver). They were generally correlated to trophic position (assessed by δ 15 N and δ 13 C) but also to cephalopods and myctophids consumption. For vegetation, values ranged from 0.014 to 0.227μgg -1 dw (Colobanthus quitensis and an unidentified lichen), with lichens presenting significantly higher values than mosses, likely due to year-round exposure and absorption of animal derived organic matter, as hypothesized by literature. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Trophic magnification of PCBs and Its relationship to the octanol-water partition coefficient.

    Science.gov (United States)

    Walters, David M; Mills, Marc A; Cade, Brian S; Burkard, Lawrence P

    2011-05-01

    We investigated polychlorinated biphenyl (PCB) bioaccumulation relative to octanol-water partition coefficient (K(OW)) and organism trophic position (TP) at the Lake Hartwell Superfund site (South Carolina). We measured PCBs (127 congeners) and stable isotopes (δ¹⁵N) in sediment, organic matter, phytoplankton, zooplankton, macroinvertebrates, and fish. TP, as calculated from δ¹⁵N, was significantly, positively related to PCB concentrations, and food web trophic magnification factors (TMFs) ranged from 1.5-6.6 among congeners. TMFs of individual congeners increased strongly with log K(OW), as did the predictive power (r²) of individual TP-PCB regression models used to calculate TMFs. We developed log K(OW)-TMF models for eight food webs with vastly different environments (freshwater, marine, arctic, temperate) and species composition (cold- vs warmblooded consumers). The effect of K(OW) on congener TMFs varied strongly across food webs (model slopes 0.0-15.0) because the range of TMFs among studies was also highly variable. We standardized TMFs within studies to mean = 0, standard deviation (SD) = 1 to normalize for scale differences and found a remarkably consistent K(OW) effect on TMFs (no difference in model slopes among food webs). Our findings underscore the importance of hydrophobicity (as characterized by K(OW)) in regulating bioaccumulation of recalcitrant compounds in aquatic systems, and demonstrate that relationships between chemical K(OW) and bioaccumulation from field studies are more generalized than previously recognized.

  3. cGMP may have trophic effects on beta cell function comparable to those of cAMP, implying a role for high-dose biotin in prevention/treatment of diabetes.

    Science.gov (United States)

    McCarty, Mark F

    2006-01-01

    Incretin hormones have trophic effects on beta cell function that can aid prevention and treatment of diabetes. cAMP is the primary mediator of these effects, and has been shown to potentiate glucose-stimulated insulin secretion, promote proper beta cells differentiation by increasing expression of the crucial transcription factor PDX-1, and prevent beta cell apoptosis. cGMP's role in beta cell function has received far less scrutiny, but there is emerging evidence that it may have a trophic impact on beta cell function analogous to that of cAMP. An increase in plasma glucose boosts beta cell production of cGMP, which acts as a feed-forward mediator to enhance glucose-stimulated insulin secretion. cGMP also has an anti-apoptotic effect in beta cells, and there is now indirect evidence that it promotes expression of PDX-1. Supraphysiological concentrations of biotin can directly activate guanylate cyclase, and there is limited evidence that high intakes of this vitamin can be therapeutically beneficial in diabetics and in rodent models of diabetes. Beneficial effects of cGMP on muscle insulin sensitivity and on control of hepatic glucose output may contribute to biotin's utility in diabetes. The fact that nitric oxide/cGMP exert a range of favorable effects on vascular health should further encourage exploration of biotin's preventive and therapeutic potential. If an appropriate high-dose biotin regimen could achieve a modest systemic increase in guanylate cyclase activity, without entailing unacceptable side effects or risks, such a regimen might have considerable potential for promoting vascular health and preventing or managing diabetes.

  4. Microbes are trophic analogues of arthropods, mammals, and fish: Isotopic fingerprinting unites ‘green’ and ‘brown’ food webs

    Science.gov (United States)

    This work addresses a cross-cutting issue within the field of food-web ecology—the integration of the microbiome into trophic hierarchies. The nature and degree to which microbes may reconfigure the trophic identities of carnivore and omnivore groups have remained surprisingly unresolved. This means...

  5. Limnological characteristics and trophic state of a newly created site: the Pareja Limno-reservoir

    Science.gov (United States)

    Molina-Navarro, E.; Martínez-Pérez, S.; Sastre-Merlín, A.

    2012-04-01

    The creation of dams in the riverine zone of large reservoirs is an innovative action whose primary goal is to generate water bodies that ensure a stable level of water there. We have termed these bodies of water "limno-reservoirs" because their water level becomes constant and independent of the fluctuations occurring in the main reservoir. In addition, limno-reservoirs represent environmental initiatives with corrective and/or compensatory effects. Pareja Limno-reservoir, located near the left side of Entrepeñas Reservoir (Guadalajara province, central Spain), is one of the first initiatives of this type in Spain. We are investigating the hydrology, limnology, microbiology, siltation risk and other aspects of this site. This research has a special interest since the building of limno-reservoirs is rising in Spain. To acquire knowledge about their behavior may be helpful for further constructions. In fact, every new reservoir building project usually includes a limno-reservoir. Moreover, there are many initiatives related with the construction of this kind of hydraulic infrastructures in the reservoirs under exploitation. This work focuses on the limnological study of the Pareja Limno-reservoir. To conduct this research, twelve seasonal sample collections at two sampling points (the dam and inflow zones) have been made in Pareja Limno-reservoir, from spring 2008 to winter 2011. The primary goal of this study is to describe the limnological characteristics of the limno-reservoir. Special interest is placed in the study of the trophic state through different indicators (nutrients, transparency, phytoplankton and zooplankton populations), as the European Water Framework Directive objective is to achieve a "good ecological status" in every aquatic ecosystem by 2015. The results of the study show that the Pareja Limno-reservoir follows a warm monomictic water stratification pattern. Water was slightly alkaline and conductivity values were mostly over 1000 μS cm-1 due

  6. From the epipelagic zone to the abyss: Trophic structure at two seamounts in the subtropical and tropical Eastern Atlantic - Part II Benthopelagic fishes

    Science.gov (United States)

    Denda, Anneke; Stefanowitsch, Benjamin; Christiansen, Bernd

    2017-12-01

    Specific mechanisms, driving trophic interactions between seamount associated fishes and the pelagic community may be highly variable in different seamount systems. This study investigated the trophic structure and the main prey of benthopelagic fishes from the summit and slope regions of Ampère and Senghor, two shallow seamounts in the subtropical and tropical NE Atlantic, and the adjacent deep-sea plains. For the identification of food sources and nutritional links to the pelagic realm a combination of stomach content and stable isotope ratio (δ13C and δ15N) analyses was used. δ13C ranged from -22.2‰ to -15.4‰ and δ15N covered a total range of 8.0-15.9‰. Feeding types of fish species comprised mainly zooplanktivores and mixed feeders, but also benthivores, piscivores, and predator-scavengers. Based on epipelagic particulate organic matter, they occupied trophic positions between the 2nd and 4th trophic level. Differences in stomach contents and stable isotope signatures indicate a resource partitioning among the benthopelagic fish fauna through distinct habitat choice, vertical feeding positions and prey selection. Topographic trapping of vertically migrating zooplankton on the summit seemed to be of minor importance for food supply of the resident near-bottom fishes, rather horizontal current-driven advection of the planktonic prey was assumed as major factor. Vertically migrating micronekton and mesopelagic fishes show up as key players within the food webs at Ampère and Senghor Seamounts and the adjacent deep-sea plains.

  7. Trophic transfer of gold nanoparticles from Euglena gracilis or Chlamydomonas reinhardtii to Daphnia magna

    International Nuclear Information System (INIS)

    Lee, Woo-Mi; Yoon, Sung-Ji; Shin, Yu-Jin; An, Youn-Joo

    2015-01-01

    Understanding the trophic transfer of nanoparticles (NPs) is important because NPs are small enough to easily penetrate into organisms. In this study, we evaluated the trophic transfer of gold NPs (AuNPs) within the aquatic food chain. We observed AuNPs transfer from 2 species of primary producers (Chlamydomonas reinhardtii or Euglena gracilis) to the primary consumer (Daphnia magna). Also, bioaccumulation of AuNPs in E. gracilis was higher than that in C. reinhardtii. The reasons for the difference in Au accumulation may be the physical structure of these organisms, and the surface area that is available for interaction with NPs. C. reinhardtii has a cell wall that may act as a barrier to the penetration of NPs. The size of E. gracilis is larger than that of C. reinhardtii. This study demonstrates the trophic transfer of AuNPs from a general producer to a consumer in an aquatic environment. - Highlights: • This study evaluated the trophic transfer of AuNPs in an aquatic food chain. • Chlamydomonas reinhardtii and Euglena gracilis were selected as the primary producers. • Daphnia magna was used as the primary consumer. • The bioaccumulation of AuNPs in E. gracilis was higher than that in C. reinhardtii. • AuNPs were transferred from C. reinhardtii and E. gracilis to D. magna. - Gold nanoparticles can transfer from primary producers (Chlamydomonas reinhardtii or Euglena gracilis) to the primary consumer (Daphnia magna) in an aquatic environment

  8. Trophic structure and mercury biomagnification in tropical fish assemblages, Iténez River, Bolivia.

    Directory of Open Access Journals (Sweden)

    Marc Pouilly

    Full Text Available We examined mercury concentrations in three fish assemblages to estimate biomagnification rates in the Iténez main river, affected by anthropogenic activities, and two unperturbed rivers from the Iténez basin, Bolivian Amazon. Rivers presented low to moderate water mercury concentrations (from 1.25 ng L(-1 to 2.96 ng L(-1 and natural differences in terms of sediment load. Mercury biomagnification rates were confronted to trophic structure depicted by carbon and nitrogen stable isotopes composition (δ(15N; δ(13C of primary trophic sources, invertebrates and fishes. Results showed a slight fish contamination in the Iténez River compared to the unperturbed rivers, with higher mercury concentrations in piscivore species (0.15 µg g(-1 vs. 0.11 µg g(-1 in the unperturbed rivers and a higher biomagnification rate. Trophic structure analysis showed that the higher biomagnification rate in the Iténez River could not be attributed to a longer food chain. Nevertheless, it revealed for the Iténez River a higher contribution of periphyton to the diet of the primary consumers fish species; and more negative δ(13C values for primary trophic sources, invertebrates and fishes that could indicate a higher contribution of methanotrophic bacteria. These two factors may enhance methylation and methyl mercury transfer in the food web and thus, alternatively or complementarily to the impact of the anthropogenic activities, may explain mercury differences observed in fishes from the Iténez River in comparison to the two other rivers.

  9. Influence of a chlor-alkali superfund site on mercury bioaccumulation in periphyton and low-trophic level fauna

    Science.gov (United States)

    Buckman, Kate L.; Marvin-DiPasquale, Mark C.; Taylor, Vivien F.; Chalmers, Ann T.; Broadley, Hannah J.; Agee, Jennifer L.; Jackson, Brian P.; Chen, Celia Y.

    2015-01-01

    In Berlin, New Hampshire, USA, the Androscoggin River flows adjacent to a former chlor-alkali facility that is a US Environmental Protection Agency Superfund site and source of mercury (Hg) to the river. The present study was conducted to determine the fate and bioaccumulation of methylmercury (MeHg) to lower trophic-level taxa in the river. Surface sediment directly adjacent to the source showed significantly elevated MeHg (10–40× increase, mean ± standard deviation [SD]: 20.1 ± 24.8 ng g–1 dry wt) and total mercury (THg; 10–30× increase, mean ± SD: 2045 ± 2669 ng g–1 dry wt) compared with all other reaches, with sediment THg and MeHg from downstream reaches elevated (3–7× on average) relative to the reference (THg mean ± SD: 33.5 ± 9.33 ng g–1 dry wt; MeHg mean ± SD: 0.52 ± 0.21 ng g–1 dry wt). Water column THg concentrations adjacent to the point source for both particulate (0.23 ng L–1) and dissolved (0.76 ng L–1) fractions were 5-fold higher than at the reference sites, and 2-fold to 5-fold higher than downstream. Methylmercury production potential of periphyton material was highest (2–9 ng g–1 d–1 dry wt) adjacent to the Superfund site; other reaches were close to or below reporting limits (0. 1 ng g–1 d–1 dry wt). Total Hg and MeHg bioaccumulation in fauna was variable across sites and taxa, with no clear spatial patterns downstream of the contamination source. Crayfish, mayflies, and shiners showed a weak positive relationship with porewater MeHg concentration.

  10. Form and function of damselfish skulls: rapid and repeated evolution into a limited number of trophic niches

    OpenAIRE

    Cooper, W James; Westneat, Mark W

    2009-01-01

    Abstract Background Damselfishes (Perciformes, Pomacentridae) are a major component of coral reef communities, and the functional diversity of their trophic anatomy is an important constituent of the ecological morphology of these systems. Using shape analyses, biomechanical modelling, and phylogenetically based comparative methods, we examined the anatomy of damselfish feeding among all genera and trophic groups. Coordinate based shape analyses of anatomical landmarks were used to describe p...

  11. Form and function of damselfish skulls: rapid and repeated evolution into a limited number of trophic niches

    Directory of Open Access Journals (Sweden)

    Cooper W James

    2009-01-01

    Full Text Available Abstract Background Damselfishes (Perciformes, Pomacentridae are a major component of coral reef communities, and the functional diversity of their trophic anatomy is an important constituent of the ecological morphology of these systems. Using shape analyses, biomechanical modelling, and phylogenetically based comparative methods, we examined the anatomy of damselfish feeding among all genera and trophic groups. Coordinate based shape analyses of anatomical landmarks were used to describe patterns of morphological diversity and determine positions of functional groups in a skull morphospace. These landmarks define the lever and linkage structures of the damselfish feeding system, and biomechanical analyses of this data were performed using the software program JawsModel4 in order to calculate the simple mechanical advantage (MA employed by different skull elements during feeding, and to compute kinematic transmission coefficients (KT that describe the efficiency with which angular motion is transferred through the complex linkages of damselfish skulls. Results Our results indicate that pomacentrid planktivores are significantly different from other damselfishes, that biting MA values and protrusion KT ratios are correlated with pomacentrid trophic groups more tightly than KT scores associated with maxillary rotation and gape angle, and that the MAs employed by their three biting muscles have evolved independently. Most of the biomechanical parameters examined have experienced low levels of phylogenetic constraint, which suggests that they have evolved quickly. Conclusion Joint morphological and biomechanical analyses of the same anatomical data provided two reciprocally illuminating arrays of information. Both analyses showed that the evolution of planktivory has involved important changes in pomacentrid functional morphology, and that the mechanics of upper jaw kinesis have been of great importance to the evolution of damselfish feeding. Our

  12. Form and function of damselfish skulls: rapid and repeated evolution into a limited number of trophic niches.

    Science.gov (United States)

    Cooper, W James; Westneat, Mark W

    2009-01-30

    Damselfishes (Perciformes, Pomacentridae) are a major component of coral reef communities, and the functional diversity of their trophic anatomy is an important constituent of the ecological morphology of these systems. Using shape analyses, biomechanical modelling, and phylogenetically based comparative methods, we examined the anatomy of damselfish feeding among all genera and trophic groups. Coordinate based shape analyses of anatomical landmarks were used to describe patterns of morphological diversity and determine positions of functional groups in a skull morphospace. These landmarks define the lever and linkage structures of the damselfish feeding system, and biomechanical analyses of this data were performed using the software program JawsModel4 in order to calculate the simple mechanical advantage (MA) employed by different skull elements during feeding, and to compute kinematic transmission coefficients (KT) that describe the efficiency with which angular motion is transferred through the complex linkages of damselfish skulls. Our results indicate that pomacentrid planktivores are significantly different from other damselfishes, that biting MA values and protrusion KT ratios are correlated with pomacentrid trophic groups more tightly than KT scores associated with maxillary rotation and gape angle, and that the MAs employed by their three biting muscles have evolved independently. Most of the biomechanical parameters examined have experienced low levels of phylogenetic constraint, which suggests that they have evolved quickly. Joint morphological and biomechanical analyses of the same anatomical data provided two reciprocally illuminating arrays of information. Both analyses showed that the evolution of planktivory has involved important changes in pomacentrid functional morphology, and that the mechanics of upper jaw kinesis have been of great importance to the evolution of damselfish feeding. Our data support a tight and biomechanically defined link

  13. The tempo-spatial variations of phytoplankton diversities and their correlation with trophic state levels in a large eutrophic Chinese lake

    DEFF Research Database (Denmark)

    Yang, Bin; Jiang, Yu-Jiao; He, Wei

    2016-01-01

    status of the lake. The present study indicated that the Margalef index of all samples was as low as 0.799 ± 0.543 in summer (August 2011) and as high as 1.467 ± 0.653 in winter (February 2012). The Margalef index of the river samples had a high mean value and substantial variation compared with the lake...... occurred in the eastern lake, especially in the middle of the lake, in autumn and winter. The total trophic state index (TSI) in all samples exhibited a significant negative correlation with the Margalef (r = −0.726) and Peilou (r = −0.530) indices but a significant positive correlation with the Shannon...

  14. Categorization of the trophic status of a hydroelectric power plant reservoir in the Brazilian Amazon by statistical analyses and fuzzy approaches.

    Science.gov (United States)

    da Costa Lobato, Tarcísio; Hauser-Davis, Rachel Ann; de Oliveira, Terezinha Ferreira; Maciel, Marinalva Cardoso; Tavares, Maria Regina Madruga; da Silveira, Antônio Morais; Saraiva, Augusto Cesar Fonseca

    2015-02-15

    The Amazon area has been increasingly suffering from anthropogenic impacts, especially due to the construction of hydroelectric power plant reservoirs. The analysis and categorization of the trophic status of these reservoirs are of interest to indicate man-made changes in the environment. In this context, the present study aimed to categorize the trophic status of a hydroelectric power plant reservoir located in the Brazilian Amazon by constructing a novel Water Quality Index (WQI) and Trophic State Index (TSI) for the reservoir using major ion concentrations and physico-chemical water parameters determined in the area and taking into account the sampling locations and the local hydrological regimes. After applying statistical analyses (factor analysis and cluster analysis) and establishing a rule base of a fuzzy system to these indicators, the results obtained by the proposed method were then compared to the generally applied Carlson and a modified Lamparelli trophic state index (TSI), specific for trophic regions. The categorization of the trophic status by the proposed fuzzy method was shown to be more reliable, since it takes into account the specificities of the study area, while the Carlson and Lamparelli TSI do not, and, thus, tend to over or underestimate the trophic status of these ecosystems. The statistical techniques proposed and applied in the present study, are, therefore, relevant in cases of environmental management and policy decision-making processes, aiding in the identification of the ecological status of water bodies. With this, it is possible to identify which factors should be further investigated and/or adjusted in order to attempt the recovery of degraded water bodies. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Review of Lepidoptera with trophic relationships to Picea abies (L. in the conditions of Czechia

    Directory of Open Access Journals (Sweden)

    Modlinger Roman

    2016-12-01

    Full Text Available Trophic relationships of Lepidoptera (Insecta occurring in the territory of Czechia to the Norway spruce (Picea abies L. was evaluated on the basis of the excerption and critical evaluation of literature. Each species was classified into the following categories – spruce as the host plant, regular development on spruce, narrow trophic relationship, indirect relationship and episodical occurrence. The particular taxa were also characterized according to their distribution and the form of larval life was specified. The development on spruce was documented in 96 species of Lepidoptera, which represented less than 3% of taxa belonging to this group and being reported from Czechia. Of that, spruce was a common host plant for 67 species, 23 species were polyphagous and might develop on spruce, and 6 species belonged to soil species damaging spruce roots, mainly in forest nurseries. Among the species of Lepidoptera, which regularly develop on spruce in the Czech conditions, 55 species were classified. As narrow specialists with special trophic relationship to spruce, 33 taxa could be considered. There were 15 spruce species with forestry importance, which were able to outbreak their populations regularly or irregularly. Among spruce species it was possible to classify 16 taxa as rare. The provided information on Lepidoptera with trophic relationship to spruce is applicable also for other Central European areas. Besides the species with importance for forest pest management, also rare taxa, which can become endangered by climate change or by forest management, were indicated.

  16. Plasticity of trophic interactions among sharks from the oceanic south-western Indian Ocean revealed by stable isotope and mercury analyses

    Science.gov (United States)

    Kiszka, Jeremy J.; Aubail, Aurore; Hussey, Nigel E.; Heithaus, Michael R.; Caurant, Florence; Bustamante, Paco

    2015-02-01

    Sharks are a major component of the top predator guild in oceanic ecosystems, but the trophic relationships of many populations remain poorly understood. We examined chemical tracers of diet and habitat (δ15N and δ13C, respectively) and total mercury (Hg) concentrations in muscle tissue of seven pelagic sharks: blue shark (Prionace glauca), short-fin mako shark (Isurus oxyrinchus), oceanic whitetip shark (Carcharhinus longimanus), scalloped hammerhead shark (Sphyrna lewini), pelagic thresher shark (Alopias pelagicus), crocodile shark (Pseudocarcharias kamoharai) and silky shark (Carcharhinus falciformis), from the data poor south-western tropical Indian Ocean. Minimal interspecific variation in mean δ15N values and a large degree of isotopic niche overlap - driven by high intraspecific variation in δ15N values - was observed among pelagic sharks. Similarly, δ13C values of sharks overlapped considerably for all species with the exception of P. glauca, which had more 13C-depleted values indicating possibly longer residence times in purely pelagic waters. Geographic variation in δ13C, δ15N and Hg were observed for P. glauca and I. oxyrinchus. Mean Hg levels were similar among species with the exception of P. kamoharai which had significantly higher Hg concentrations likely related to mesopelagic feeding. Hg concentrations increased with body size in I. oxyrinchus, P. glauca and C. longimanus. Values of δ15N and δ13C varied with size only in P. glauca, suggesting ontogenetic shifts in diets or habitats. Together, isotopic data indicate that - with few exceptions - variance within species in trophic interactions or foraging habitats is greater than differentiation among pelagic sharks in the south-western Indian Ocean. Therefore, it is possible that this group exhibits some level of trophic redundancy, but further studies of diets and fine-scale habitat use are needed to fully test this hypothesis.

  17. Flow regime in a restored wetland determines trophic links and species composition in the aquatic macroinvertebrate community

    International Nuclear Information System (INIS)

    González-Ortegón, E.; Walton, M.E.M.; Moghaddam, B.; Vilas, C.; Prieto, A.; Kennedy, H.A.; Pedro Cañavate, J.; Le Vay, L.

    2015-01-01

    In a restored wetland (South of Spain), where different flow regimes control water exchange with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic counterpart species Palaemon macrodactylus. This controlled m/acrocosm offers an excellent opportunity to investigate how the effects of water management, through different flow regimes, and the presence of a non-native species affect the aquatic community and the trophic niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. We found that increased water exchange rate (5% day −1 in mixed ponds vs. 0.1% day −1 in extensive ponds) modified the aquatic community of this wetland; while extensive ponds are dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine origin of nutrients and primary production might explain seasonal and spatial differences found among ponds of this wetland. A combined analysis of gut contents and isotopic composition of the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap occurred when both species coexist at mixed ponds where a higher water exchange and high abundance of mysids and copepods diversifies the native species' diet. Thus differences in the trophic ecology of both species are clearly explained by water management. This experimental study is a valuable tool for integrated management between river basin and wetlands since it allows quantification of wetland community changes in response to the flow regime. - Highlights: • Flow regimen is a major determinant of physicochemical habitat of a wetland. • Water exchanges wetland-estuary modify its aquatic community and trophic links. • Omnivory and physiological tolerance key in the resistance of a wetland

  18. Concentrations and trophic magnification of polychlorinated naphthalenes (PCNs) in marine fish from the Bohai coastal area, China.

    Science.gov (United States)

    Cui, Lili; Wang, Shasha; Gao, Lirong; Huang, Huiting; Xia, Dan; Qiao, Lin; Liu, Wenbin

    2018-03-01

    Polychlorinated naphthalenes (PCNs) have been found widely in the aquatic environment and can be transferred through food chains, which can magnify or dilute their toxic effects on humans. In this study, PCNs were analyzed in samples of 17 species of fish with different dietary habits collected in the Bohai coastal area in China. Dichloronaphthalenes, which have rarely been quantified in previous studies, were determined. The total PCN concentrations were from 7.3 to 214 pg/g wet weight, and the highest concentration was found in ditrema. The trichloronaphthalenes were the most abundant PCNs, followed by the dichloronaphthalenes and pentachloronaphthalenes. The relatively high contributions of the less-chlorinated homologs to the total PCN concentrations indicated that the main PCN sources around the Bohai were industrial thermal process emissions rather than technical PCN formulations. The trophic magnification factors of the PCN homologs were from 3.1 to 9.9, indicating that PCNs were biomagnified by fish. The trophic magnification factor of dichloronaphthalene and trichloronaphthalenes was 5.8 and 6.4, respectively, indicating for the first time that dichloronaphthalene and trichloronaphthalenes can undergo trophic magnification by fish. The two highest trophic magnification factors were for the pentachloronaphthalenes and hexachloronaphthalenes, probably because these PCNs having fewer vicinal carbon atoms without chlorine atoms attached are less easily biotransformed than the other homologs. The dioxin-like toxicities of the PCNs in the samples, expressed as potential toxic equivalences (TEQs), were assessed. The highest total TEQ was 0.0090 pg/g ww, in Pacific herring, and the hexachloronaphthalenes were the dominant contributors to the total TEQs in the fish samples. The PCN TEQs were much lower than the polychlorinated dibenzo-p-dioxin and dibenzofuran and dioxin-like polychlorinated biphenyl TEQs found in fish from the Bohai in previous studies, and

  19. Holistic assessment of Chwaka Bay's multi-gear fishery - Using a trophic modeling approach

    Science.gov (United States)

    Rehren, Jennifer; Wolff, Matthias; Jiddawi, Narriman

    2018-04-01

    East African coastal communities highly depend on marine resources for not just income but also protein supply. The multi-species, multi-gear nature of East African fisheries makes this type of fishery particularly difficult to manage, as there is a trade-off between maximizing total catch from all gears and species and minimizing overfishing of target species and the disintegration of the ecosystem. The use and spatio-temporal overlap of multiple gears in Chwaka Bay (Zanzibar) has led to severe conflicts between fishermen. There is a general concern of overfishing in the bay because of the widespread use of small mesh sizes and destructive gears such as dragnets and spear guns. We constructed an Ecopath food web model to describe the current trophic flow structure and fishing pattern of the bay. Based on this model, we explored the impact of different gears on the ecosystem and the fishing community in order to give advice for gear based management in the bay. Results indicate that Chwaka bay is a productive, shallow water system, with biomass concentrations around the first and second trophic level. The system is greatly bottom-up driven and dominated by primary producers and invertebrates. The trophic and network indicators as well as the community energetics characterize Chwaka Bay as relatively mature. Traps and dragnets have the strongest impact on the ecosystem and on the catches obtained by other gears. Both gears potentially destabilize the ecosystem by reducing the biomass of top-down controlling key species (including important herbivores of macroalgae). The dragnet fishery is the least profitable, but provides most jobs for the fishing community. Thus, a complete ban of dragnets in the bay would require the provision of alternative livelihoods. Due to the low resource biomass of fish in the bay and the indication of a loss of structural control of certain fish groups, Chwaka Bay does not seem to provide scope for further expansion of the fishery

  20. Advancing the match-mismatch framework for large herbivores in the Arctic: Evaluating the evidence for a trophic mismatch in caribou.

    Directory of Open Access Journals (Sweden)

    David Gustine

    Full Text Available Climate-induced shifts in plant phenology may adversely affect animals that cannot or do not shift the timing of their reproductive cycle. The realized effect of potential trophic "mismatches" between a consumer and its food varies with the degree to which species rely on dietary income and stored capital. Large Arctic herbivores rely heavily on maternal capital to reproduce and give birth near the onset of the growing season but are they vulnerable to trophic mismatch? We evaluated the long-term changes in the temperatures and characteristics of the growing seasons (1970-2013, and compared growing conditions and dynamics of forage quality for caribou at peak parturition, peak lactation, and peak forage biomass, and plant senescence between two distinct time periods over 36 years (1977 and 2011-13. Despite advanced thaw dates (7-12 days earlier, increased growing season lengths (15-21 days longer, and consistent parturition dates, we found no decline in forage quality and therefore no evidence within this dataset for a trophic mismatch at peak parturition or peak lactation from 1977 to 2011-13. In Arctic ungulates that use stored capital for reproduction, reproductive demands are largely met by body stores deposited in the previous summer and autumn, which reduces potential adverse effects of any mismatch between food availability and timing of parturition. Climate-induced effects on forages growing in the summer and autumn ranges, however, do correspond with the demands of female caribou and their offspring to gain mass for the next reproductive cycle and winter. Therefore, we suggest the window of time to examine the match-mismatch framework in Arctic ungulates is not at parturition but in late summer-autumn, where the multiplier effects of small changes in forage quality are amplified by forage abundance, peak forage intake, and resultant mass gains in mother-offspring pairs.

  1. Trigeminal Trophic Syndrome – Case Report

    Directory of Open Access Journals (Sweden)

    Boštjan Matos

    2015-05-01

    Full Text Available 1024x768 Trigeminal trophic syndrome is a rare condition resulting from compulsive self-manipulation of the skin after a peripheral or central injury to the trigeminal system. The classic triad consists of trigeminal anesthesia, facial paresthesias, and crescentric lateral nasal alar erosion and ulceration. Although the symptoms are visibly clear, the diagnosis is not easy to establish. The appearance of the ulcers mimics many other disease entities such as neoplasm, infection, granulomatous disease, vasculitis and factitial dermatitis. Trigeminal trophic syndrome should be considered with a positive neurologic history and when laboratory and biopsy workup is inconclusive. Once diagnosis is confirmed, treatment is complicated and often multidisciplinary. We report a case of a woman who developed a strictly unilateral crescent ulcer of the ala nasi after resection of an statoacoustic neurinoma. A clinician who is faced with a patient with nasal ulceration should consider this diagnosis.     Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

  2. Trophic transfer and in vivo immunotoxicological effects of tributyltin (TBT) in polar seastar Leptasterias polaris

    International Nuclear Information System (INIS)

    Bekri, Khalida; Pelletier, Emilien

    2004-01-01

    This study investigated the potential in vivo immunotoxic effects of tributyltin (TBT) on amoebocytes of 6-armed seastar Leptasterias polaris. Tested animals were contaminated by trophic transfer via alive contaminated prey consisting of blue mussels (3 μg TBT g -1 wet weight (WW) tissue) exposed to seawater containing dissolved TBT. Four biomarkers of immunotoxicological effects were monitored over 45 days at different sampling times (9, 24, 48 and 72 h, 11, 18, 25, 32 and 45 days): amoebocytes count (AC), cell viability using Trypan blue exclusion test, phagocytic activity (PA) using a suspension of dead bacteria labelled with fluorescein isothiocyanate (FITC) and injected directly in the coelomic fluid of the animals, and lysosomal integrity (LI) using the neutral red (NR) retention test. Data showed that TBT and its metabolites (DBT and MBT) bioaccumulated preferentially in pyloric caeca, whereas gonads contained only small quantities. Despite the differences in exposure periods to the contaminated diet and in burdens of butyltins (BTs) ingested by the various contaminated groups, there were no significant differences in body burdens of BTs. Only 6.2±2.0% of total ingested BTs were retained in soft tissues of seastars. Even if butyltins were not detected in the coelomic fluid (CF), their detrimental effects have been detected in the phagocytic activity of amoebocytes and their lysosomal retention of neutral red, but no effects were observed on amoebocytes count and their viability. These results show that seastar L. polaris possesses adequate mechanisms to depurate ingested TBT without supporting major disturbances of its immune defence system. By their ability to digest whole contaminated prey and eliminate only dissolved metabolites, L. polaris and other seastars with the same preying mode could play a role of 'recycling organisms' in coastal environments where toxicants, such as butyltins and other metallic species are accumulated by bivalves and

  3. Environmental drivers of heterogeneity in the trophic-functional structure of protozoan communities during an annual cycle in a coastal ecosystem.

    Science.gov (United States)

    Xu, Guangjian; Yang, Eun Jin; Xu, Henglong

    2017-08-15

    Trophic-functional groupings are an important biological trait to summarize community structure in functional space. The heterogeneity of the tropic-functional pattern of protozoan communities and its environmental drivers were studied in coastal waters of the Yellow Sea during a 1-year cycle. Samples were collected using the glass slide method at four stations within a water pollution gradient. A second-stage matrix-based analysis was used to summarize spatial variation in the annual pattern of the functional structure. A clustering analysis revealed significant variability in the trophic-functional pattern among the four stations during the 1-year cycle. The heterogeneity in the trophic-functional pattern of the communities was significantly related to changes in environmental variables, particularly ammonium-nitrogen and nitrates, alone or in combination with dissolved oxygen. These results suggest that the heterogeneity in annual patterns of protozoan trophic-functional structure may reflect water quality status in coastal ecosystems. Copyright © 2017. Published by Elsevier Ltd.

  4. Trophic interference by Salmo trutta on Aplochiton zebra and Aplochiton taeniatus in southern Patagonian lakes.

    Science.gov (United States)

    Elgueta, A; González, J; Ruzzante, D E; Walde, S J; Habit, E

    2013-02-01

    The length and mass ratio, diet and isotopic composition of Aplochiton zebra and Aplochiton taeniatus inhabiting a Salmo trutta-invaded and a S. trutta-free lake in southern Patagonia were compared. Results indicate that S. trutta exercises important trophic interference over A. zebra and A. taeniatus, causing changes in their dietary composition by reducing the consumption of winged Diptera through changes in feeding behaviours that involve jumping out of the water. This effect is significantly higher in A. zebra than in A. taeniatus a species that has a highly specialized diet. The dietary changes of A. zebra and A. taeniatus in sympatry with S. trutta lead to an impoverishment of their isotopic nitrogen signals (δ(15)N), suggesting a reduction of their trophic position. In the case of A. zebra, this translates into a significant decrease in its body condition factor. Such interference could lead to a population decline of this species and would explain the current distribution range decline and allopatry with S. trutta in fluvial systems. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

  5. Reciprocal Trophic Interactions and Transmission of Blood Parasites between Mosquitoes and Frogs

    Directory of Open Access Journals (Sweden)

    Todd G. Smith

    2012-04-01

    Full Text Available The relationship between mosquitoes and their amphibian hosts is a unique, reciprocal trophic interaction. Instead of a one-way, predator-prey relationship, there is a cyclical dance of avoidance and attraction. This has prompted spatial and temporal synchrony between organisms, reflected in emergence time of mosquitoes in the spring and choice of habitat for oviposition. Frog-feeding mosquitoes also possess different sensory apparatuses than do their mammal-feeding counterparts. The reciprocal nature of this relationship is exploited by various blood parasites that use mechanical, salivary or trophic transmission to pass from mosquitoes to frogs. It is important to investigate the involvement of mosquitoes, frogs and parasites in this interaction in order to understand the consequences of anthropogenic actions, such as implementing biocontrol efforts against mosquitoes, and to determine potential causes of the global decline of amphibian species.

  6. Prey utilisation and trophic overlap between the non native mosquitofish and a native fish in two Mediterranean rivers

    Directory of Open Access Journals (Sweden)

    E. KALOGIANNI

    2014-04-01

    Full Text Available Non native freshwater fish species have been long implicated in the decline of native Mediterranean ichthyofauna, through hybridization, disease transmission, competition for food and habitat, predation and/or ecosystem alteration; our knowledge, however, on the underlying mechanisms of these ecological impacts remains very limited. To explore the potential for trophic competition between the widespread Eastern mosquitofish Gambusia holbrooki and its co-occurring native toothcarp Valencia letourneuxi we compared resource use, feeding strategies, trophic selectivities and diet niche overlap. For this purpose, we studied two populations of the two species from a freshwater and a brackish habitat respectively, characterized by different food resource availabilities. In both habitats, the mosquitofish consumed a greater diversity of invertebrates and preyed on terrestrial invertebrates more frequently than the native toothcarp. Furthermore, in the less diverse and less rich brackish habitat, the non native relied heavily on plant material to balance a decrease in animal prey consumption and modified its individual feeding strategy, whereas these adaptive changes were not apparent in the native species. Their diet overlapped, indicating trophic competition, but this overlap was affected by resource availability variation; in the freshwater habitat, there was limited overlap in their diet, whereas in the brackish habitat, their diets and prey selectivities converged and there was high overlap in resource use, indicative of intense interspecific trophic competition. Overall, it appears that the underlying mechanism of the putative negative impacts of the mosquitofish on the declining Corfu toothcarp is mainly trophic competition, regulated by resource variability, though there is also evidence of larvae predation by the mosquitofish.

  7. Species co-occurrence affects the trophic interactions of two juvenile reef shark species in tropical lagoon nurseries in Moorea (French Polynesia).

    Science.gov (United States)

    Matich, Philip; Kiszka, Jeremy J; Mourier, Johann; Planes, Serge; Heithaus, Michael R

    2017-06-01

    Food web structure is shaped by interactions within and across trophic levels. As such, understanding how the presence and absence of predators, prey, and competitors affect species foraging patterns is important for predicting the consequences of changes in species abundances, distributions, and behaviors. Here, we used plasma δ 13 C and δ 15 N values from juvenile blacktip reef sharks (Carcharhinus melanopterus) and juvenile sicklefin lemon sharks (Negaprion acutidens) to investigate how species co-occurrence affects their trophic interactions in littoral waters of Moorea, French Polynesia. Co-occurrence led to isotopic niche partitioning among sharks within nurseries, with significant increases in δ 15 N values among sicklefin lemon sharks, and significant decreases in δ 15 N among blacktip reef sharks. Niche segregation likely promotes coexistence of these two predators during early years of growth and development, but data do not suggest coexistence affects life history traits, such as body size, body condition, and ontogenetic niche shifts. Plasticity in trophic niches among juvenile blacktip reef sharks and sicklefin lemon sharks also suggests these predators are able to account for changes in community structure, resource availability, and intra-guild competition, and may fill similar functional roles in the absence of the other species, which is important as environmental change and human impacts persist in coral reef ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Proposal for a remote sensing trophic state index based upon Thematic Mapper/Landsat images

    Directory of Open Access Journals (Sweden)

    Evlyn Márcia Leão de Moraes Novo

    2013-12-01

    Full Text Available This work proposes a trophic state index based on the remote sensing retrieval of chlorophyll-α concentration. For that, in situ Bidirectional Reflectance Factor (BRF data acquired in the Ibitinga reservoir were resampled to match Landsat/TM spectral simulated bands (TM_sim bands and used to run linear correlation with concurrent measurements of chlorophyll-α concentration. Monte Carlo simulation was then applied to select the most suitable model relating chlorophyll-α concentration and simulated TM/Landsat reflectance. TM4_sim/TM3_sim ratio provided the best model with a R2 value of 0.78. The model was then inverted to create a look-up-table (LUT relating TM4_sim/TM3_sim ratio intervals to chlorophyll-α concentration trophic state classes covering the entire range measured in the reservoir. Atmospheric corrected Landsat TM images converted to surface reflectance were then used to generate a TM4/TM3 ratio image. The ratio image frequency distribution encompassed the range of TM4_sim/TM3_sim ratio indicating agreement between in situ and satellite data and supporting the use of satellite data to map chlorophyll- concentration trophic state distribution in the reservoir. Based on that, the LUT was applied to a Landsat/TM ratio image to map the spatial distribution of chlorophyll- trophic state classes in Ibitinga reservoir. Despite the stochastic selection of TM4_sim/TM3_sim ratio as the best input variable for modeling the chlorophyll-α concentration, it has a physical basis: high concentration of phytoplankton increases the reflectance in the near-infrared (TM4 and decreases the reflectance in the red (TM3. The band ratio, therefore, enhances the relationship between chlorophyll- concentration and remotely sensed reflectance.

  9. Trophic ecology of Mustelus schmitti (Springer, 1939) in a nursery area of northern Patagonia

    Science.gov (United States)

    Molina, Juan Manuel; Cazorla, Andrea López

    2011-05-01

    Mustelus schmitti is an endangered endemic shark of the southwest Atlantic, and an important economical resource in Argentina, Brazil and Uruguay. The objective of this study was to describe the trophic ecology of M. schmitti in Anegada Bay, its feeding strategy and diet composition, along with the possible dietary shifts, due to season, sex, ontogeny and the different geographical features of the bay. Our results show that M. schmitti is a carnivorous opportunistic predator, feeding on a variety of benthic invertebrates. The diet presented seasonal and ontogenetic variations, while no differences in diet composition were observed between sexes or the different sampling sites. This species behave as a generalize feeder, with a wide trophic spectrum and a diverse diet.

  10. [Use of magnetic therapy combined with galvanization and tissue electrophoresis in the treatment of trophic ulcers].

    Science.gov (United States)

    Alekseenko, A V; Gusak, V V; Stoliar, V F; Iftodiĭ, A G; Tarabanchuk, V V; Shcherban, N G; Naumets, A A

    1993-01-01

    The results of treatment of 86 patients with the use of magnetotherapy in combination with galvanization and intratissue electrophoresis are presented. To create an electric field, the "Potok-1" apparatus with a density of current equal to 0.05-0.1 mA/cm2 was employed. Simultaneously, the "MAG-30" apparatus for low-frequency magnetotherapy with induction of 30 mT and area of exposure of 20 cm2 was applied to a trophic ulcer site. The use of magnetogalvanotherapy in the complex of treatment of trophic ulcers of the lower extremities is recommended.

  11. Arctic-nesting birds find physiological relief in the face of trophic constraints.

    Science.gov (United States)

    McKinnon, Laura; Nol, Erica; Juillet, Cédric

    2013-01-01

    A climate-induced phenological mismatch between the timing of reproduction and the timing of food resource peaks is one of the key hypothesized effects of climate change on wildlife. Though supported as a mechanism of population decline in birds, few studies have investigated whether the same temperature increases that drive this mismatch have the potential to decrease energetic costs of growth and compensate for the potential negative effects of reduced food availability. We generated independent indices of climate and resource availability and quantified their effects on growth of Dunlin (Calidris alpina) chicks, in the sub-arctic tundra of Churchill, Manitoba during the summers of 2010-2011 and found that when resource availability was below average, above average growth could be maintained in the presence of increasing temperatures. These results provide evidence that chicks may find physiological relief from the trophic constraints hypothesized by climate change studies.

  12. Trophic factors from adipose tissue-derived multi-lineage progenitor cells promote cytodifferentiation of periodontal ligament cells

    International Nuclear Information System (INIS)

    Sawada, Keigo; Takedachi, Masahide; Yamamoto, Satomi; Morimoto, Chiaki; Ozasa, Masao; Iwayama, Tomoaki; Lee, Chun Man; Okura, Hanayuki; Matsuyama, Akifumi; Kitamura, Masahiro; Murakami, Shinya

    2015-01-01

    Stem and progenitor cells are currently being investigated for their applicability in cell-based therapy for periodontal tissue regeneration. We recently demonstrated that the transplantation of adipose tissue-derived multi-lineage progenitor cells (ADMPCs) enhances periodontal tissue regeneration in beagle dogs. However, the molecular mechanisms by which transplanted ADMPCs induce periodontal tissue regeneration remain to be elucidated. In this study, trophic factors released by ADMPCs were examined for their paracrine effects on human periodontal ligament cell (HPDL) function. ADMPC conditioned medium (ADMPC-CM) up-regulated osteoblastic gene expression, alkaline phosphatase activity and calcified nodule formation in HPDLs, but did not significantly affect their proliferative response. ADMPCs secreted a number of growth factors, including insulin-like growth factor binding protein 6 (IGFBP6), hepatocyte growth factor and vascular endothelial growth factor. Among these, IGFBP6 was most highly expressed. Interestingly, the positive effects of ADMPC-CM on HPDL differentiation were significantly suppressed by transfecting ADMPCs with IGFBP6 siRNA. Our results suggest that ADMPCs transplanted into a defect in periodontal tissue release trophic factors that can stimulate the differentiation of HPDLs to mineralized tissue-forming cells, such as osteoblasts and cementoblasts. IGFBP6 may play crucial roles in ADMPC-induced periodontal regeneration. - Highlights: • ADMPC-derived humoral factors stimulate cytodifferentiation of HPDLs. • ADMPCs secret growth factors including IGFBP6, VEGF and HGF. • IGFBP6 is involved in the promotion effect of ADMPC-CM on HPDL cytodifferentiation

  13. Trophic factors from adipose tissue-derived multi-lineage progenitor cells promote cytodifferentiation of periodontal ligament cells

    Energy Technology Data Exchange (ETDEWEB)

    Sawada, Keigo [Department of Periodontology, Osaka University Graduate School of Dentistry, Osaka (Japan); Takedachi, Masahide, E-mail: takedati@dent.osaka-u.ac.jp [Department of Periodontology, Osaka University Graduate School of Dentistry, Osaka (Japan); Yamamoto, Satomi; Morimoto, Chiaki; Ozasa, Masao; Iwayama, Tomoaki [Department of Periodontology, Osaka University Graduate School of Dentistry, Osaka (Japan); Lee, Chun Man [Medical Center for Translational Research, Osaka University Hospital, Osaka (Japan); Okura, Hanayuki; Matsuyama, Akifumi [Research on Disease Bioresources, Platform of Therapeutics for Rare Disease, National Institute of Biomedical Innovation, Osaka (Japan); Kitamura, Masahiro; Murakami, Shinya [Department of Periodontology, Osaka University Graduate School of Dentistry, Osaka (Japan)

    2015-08-14

    Stem and progenitor cells are currently being investigated for their applicability in cell-based therapy for periodontal tissue regeneration. We recently demonstrated that the transplantation of adipose tissue-derived multi-lineage progenitor cells (ADMPCs) enhances periodontal tissue regeneration in beagle dogs. However, the molecular mechanisms by which transplanted ADMPCs induce periodontal tissue regeneration remain to be elucidated. In this study, trophic factors released by ADMPCs were examined for their paracrine effects on human periodontal ligament cell (HPDL) function. ADMPC conditioned medium (ADMPC-CM) up-regulated osteoblastic gene expression, alkaline phosphatase activity and calcified nodule formation in HPDLs, but did not significantly affect their proliferative response. ADMPCs secreted a number of growth factors, including insulin-like growth factor binding protein 6 (IGFBP6), hepatocyte growth factor and vascular endothelial growth factor. Among these, IGFBP6 was most highly expressed. Interestingly, the positive effects of ADMPC-CM on HPDL differentiation were significantly suppressed by transfecting ADMPCs with IGFBP6 siRNA. Our results suggest that ADMPCs transplanted into a defect in periodontal tissue release trophic factors that can stimulate the differentiation of HPDLs to mineralized tissue-forming cells, such as osteoblasts and cementoblasts. IGFBP6 may play crucial roles in ADMPC-induced periodontal regeneration. - Highlights: • ADMPC-derived humoral factors stimulate cytodifferentiation of HPDLs. • ADMPCs secret growth factors including IGFBP6, VEGF and HGF. • IGFBP6 is involved in the promotion effect of ADMPC-CM on HPDL cytodifferentiation.

  14. Bioaccumulation of 14C-Labeled Graphene in an Aquatic Food Chain through Direct Uptake or Trophic Transfer.

    Science.gov (United States)

    Dong, Shipeng; Xia, Tian; Yang, Yu; Lin, Sijie; Mao, Liang

    2018-01-16

    The growing applications of graphene materials warrant a careful evaluation of their environmental fate in aquatic food webs. Escherichia coli (Bacteria), Tetrahymena thermophila (protozoa), Daphnia magna (zooplankton), and Danio rerio (vertebrate) were used to build aquatic food chains to investigate the waterborne uptake and trophic transfer of 14 C-labeled graphene. Body burden factor (BBF) and trophic transfer factor (TTF) were analyzed for each organism and food chain to assess the bioaccumulation and biomagnification of graphene. The test organisms have high potential of accumulating graphene via direct uptake from culture medium with log-transformed BBF (log BBF) values of 3.66, 5.1, 3.9, and 1.62 for each organism, respectively. In the food chain from E. coli to T. thermophila, the calculated TTFs of 0.2 to 8.6 indicate the high trophic transfer potential in this aquatic food chain. However, the TTFs calculated for the food chain from T. thermophila to D. magna and from D. magna to D. rerio are much lower than 1, indicating that biomagnification was unlikely to occur in these food chains. Body burden measured for dietary uptake by T. thermophila, D. magna, and D. rerio are higher than that via waterborne exposure in a similar nominal concentration, respectively, indicating that trophic transfer is a nonnegligible route for the bioaccumulation of graphene in organisms.

  15. Combined Influence of Landscape Composition and Nutrient Inputs on Lake Trophic Structure

    Science.gov (United States)

    The concentration of chlorophyll a is a measure of the biological productivity of a lake and is largely (but not exclusively) determined by available nutrients. As nutrient inputs increase, productivity increases and lakes transition from low trophic state (e.g. oligotrophic) to...

  16. Understanding trophic interactions of Orius spp. (Hemiptera: Anthocoridae) in lettuce crops by molecular methods.

    Science.gov (United States)

    Gomez-Polo, Priscila; Alomar, Oscar; Castañé, Cristina; Aznar-Fernández, Thaïs; Lundgren, Jonathan G; Piñol, Josep; Agustí, Nuria

    2016-02-01

    The aphid Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae) and the thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) are common pests in Mediterranean lettuce crops, where Orius spp. are common generalist predators. Predation by Orius spp. was studied in a lettuce plot by conventional polymerase chain reaction (PCR) and real-time PCR analyses using specific primers of both main pests. Also, high-throughput sequencing was used to have a wider approach of the diet of these predators in natural field conditions. Molecular analyses indicated a higher predation on N. ribisnigri in spring and on F. occidentalis in summer. Predation on alternative prey, like Collembola, was also found in both seasons. Real-time PCR was more sensitive than conventional PCR in showing the target trophic links, whereas high-throughput sequencing revealed predation on other natural enemies - intraguild predation (IGP), showing other trophic interactions of Orius majusculus within the studied ecosystem. This study gives important information about the trophic relationships present in Mediterranean lettuce crops in different periods of the year. The detected predation by Orius spp. on alternative prey, as well as on other natural enemies, should be further investigated to clarify whether it adds or detracts to the biological control of N. ribisnigri and F. occidentalis. © 2015 Society of Chemical Industry.

  17. Trophic analysis of the fish community in the Ciénega Churince, Cuatro Ciénegas, Coahuila

    Directory of Open Access Journals (Sweden)

    Ariana Hernández

    2017-09-01

    Full Text Available Fish diets were analyzed to evaluate the dynamic trophs of the fish community in the Churince wetland system of the Cuatro Ciénegas, where the fauna consists of nine species: endemic, native and introduced. In nine sampling events (between February 2011 and May 2014 556 specimens of all nine species were collected. Stomach contents were analyzed and the Relative Importance Index (IRI was calculated. The feed coefficient (Q of the diets and the accumulated trophic diversity (Hk, as well as the amplitude of the trophic niche were evaluated. Feeding strategies in the fish community were found to be eurifagic. The main foods in general were insects, crustaceans, gastropods, plants and teleosts. According to the average linkage method, four functional trophic groups were defined, with no higher consumption species; nevertheless all were regulators, mainly invertebrates. Therefore, the chain reaction in food control was higher from top to bottom, meaning a downwards dietary control.

  18. Trophic Magnification of PCBs and Its Relationship to the Octanol−Water Partition Coefficient

    Science.gov (United States)

    We investigated polychlorinated biphenyl (PCB) bioaccumulation relative to octanol-water partition coefficient (KOW) and organism trophic position (TP) at the Lake Hartwell Superfund (South Carolina, USA). We measured PCBs (127 congeners) and stable isotopes (δ15...

  19. Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods?

    Science.gov (United States)

    Barber-Meyer, Shannon M

    2015-05-01

    This is a Forum article commenting on: Ripple, W. J., Beschta, R. L., Fortin, J. K., & Robbins, C. T. (2014) Trophic cascades from wolves to grizzly bears in Yellowstone. Journal of Animal Ecology, 83, 223-233. Comparisons Ripple et al. (2014) used to demonstrate increased fruit availability and consumption by grizzly bears post-wolf reintroduction are flawed and tenuous at best. Importantly, a more parsimonious (than trophic cascades) hypothesis, not sufficiently considered by Ripple et al., exists and is better supported by available data I review. Published 2015. This article is a U. S. Government work and is in the public domain in the USA.

  20. Flow regime in a restored wetland determines trophic links and species composition in the aquatic macroinvertebrate community

    Energy Technology Data Exchange (ETDEWEB)

    González-Ortegón, E., E-mail: quique.gonzalezortegon@andaluciajunta.es [School of Ocean Sciences, Bangor University, Menai Bridge LL59 5AB (United Kingdom); IFAPA Centro El Toruño, Camino Tiro de Pichón s/n, 11500 El Puerto de Santa María (Spain); Walton, M.E.M.; Moghaddam, B. [School of Ocean Sciences, Bangor University, Menai Bridge LL59 5AB (United Kingdom); Vilas, C.; Prieto, A. [IFAPA Centro El Toruño, Camino Tiro de Pichón s/n, 11500 El Puerto de Santa María (Spain); Kennedy, H.A. [School of Ocean Sciences, Bangor University, Menai Bridge LL59 5AB (United Kingdom); Pedro Cañavate, J. [IFAPA Centro El Toruño, Camino Tiro de Pichón s/n, 11500 El Puerto de Santa María (Spain); Le Vay, L. [School of Ocean Sciences, Bangor University, Menai Bridge LL59 5AB (United Kingdom)

    2015-01-15

    In a restored wetland (South of Spain), where different flow regimes control water exchange with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic counterpart species Palaemon macrodactylus. This controlled m/acrocosm offers an excellent opportunity to investigate how the effects of water management, through different flow regimes, and the presence of a non-native species affect the aquatic community and the trophic niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. We found that increased water exchange rate (5% day{sup −1} in mixed ponds vs. 0.1% day{sup −1} in extensive ponds) modified the aquatic community of this wetland; while extensive ponds are dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine origin of nutrients and primary production might explain seasonal and spatial differences found among ponds of this wetland. A combined analysis of gut contents and isotopic composition of the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap occurred when both species coexist at mixed ponds where a higher water exchange and high abundance of mysids and copepods diversifies the native species' diet. Thus differences in the trophic ecology of both species are clearly explained by water management. This experimental study is a valuable tool for integrated management between river basin and wetlands since it allows quantification of wetland community changes in response to the flow regime. - Highlights: • Flow regimen is a major determinant of physicochemical habitat of a wetland. • Water exchanges wetland-estuary modify its aquatic community and trophic links. • Omnivory and physiological tolerance key in the resistance of a

  1. Eutrophication potential of lakes: an integrated analysis of trophic state, morphometry, land occupation, and land use

    Directory of Open Access Journals (Sweden)

    RF Silvino

    Full Text Available AbstractDespite being inside a protected area, Lake Sumidouro has been impacted by the anthropogenic occupation of the surrounding area since the 1970’s, compromising the ecological integrity of the lake and the sustainable use of natural resources. This study examined the current trophic classification of the lake and developed methods for improving it through an integrated analysis of morphometric and limnological parameters, land use and land occupation in the watershed, and eutrophication potential. Data for the limnological parameters, land use and land occupation, and morphometric characteristics of Lake Sumidouro were collected in the rainy and dry seasons of 2009 and 2010. Depending on the trophic classification system used, Lake Sumidouro is classified as oligotrophic to hypereutrophic. In our study, the highest concentration of nutrients occurred in the rainy season, indicating that high nutrient inputs played an important role during this period. Areas of anthropogenic occupation comprised approximately 62.9% of the total area of the watershed, with pasture and urban settlement as the main types of land use. The influent total phosphorus load was estimated to be 15,824.3 kg/year. To maintain mesotrophic conditions, this load must be reduced by 29.4%. By comparing the isolated use of trophic state indices, this study demonstrated that comparing the trophic state classification with morphometric analyses, land use and land occupation types in the watershed, and potential phosphorus load provided better information to guide management actions for restoration and conservation. Furthermore, this approach also allowed for evaluating the vulnerability of the environment to the eutrophication process.

  2. Interspecific comparison of radiocesium trophic transfer in two tropical fish species.

    Science.gov (United States)

    Pouil, Simon; Teyssié, Jean-Louis; Fowler, Scott W; Metian, Marc; Warnau, Michel

    2018-09-01

    The trophic transfer of radiocesium ( 134 Cs) was investigated in two tropical fish, the silver moony Monodactylus argenteus and the spotted scat Scatophagus argus. Juveniles of both species were exposed to dietary 134 Cs using the pulse-chase feeding methodology. The food was brine shrimp (Artemia salina) previously exposed to the dissolved radiotracer. Depuration kinetics of 134 Cs were followed for 45 d. Results showed that Cs was similarly efficiently assimilated by both species (AE > 50%). The estimated trophic transfer factors in the two species ranked from 1 to 2, suggesting that 134 Cs could be biomagnified in both omnivorous species. In complement, dissections of 7 body compartments were carried out at three different times in order to highlight 134 Cs organotropism. 134 Cs organotropism was similar in both species: more than 50% of 134 Cs was quickly distributed in the muscles and skeleton (after 3 days of depuration), which is likely related to the analogous behavior between Cs and K, an essential element for muscle contractions and bone formation. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Trophic relationships between the jumbo squid (Dosidicus gigas and the lightfish (Vinciguerria lucetia in the Humboldt Current System off Peru

    Directory of Open Access Journals (Sweden)

    Rigoberto Rosas-Luis

    2011-04-01

    Full Text Available Acoustic surveys for assessing the biomass and distribution of the jumbo squid (Dosidicus gigas and the lightfish (Vinciguerria lucetia were carried out in the Humboldt Current System of Peru in 2007 and 2008. At the same time, 937 jumbo squid were caught and their stomach contents analyzed. The diet of the jumbo squid was dominated by mesopelagic fish. The first component of their fish diet was V. lucetia and the second component was the myctophid fish Diogenichthys laternatus. Acoustic biomass estimates of these species show that V. lucetia is an important component in aggregative structures in the Humboldt Current System of Peru and its distribution and movements are closely related to the migratory movements of the jumbo squid. The trophic relationship observed between D. gigas and V. lucetia promotes an increase in jumbo squid biomass and, has a positive trophic effect on the ocean ecosystem.

  4. Trophic relationships in an Arctic food web and implications for trace metal transfer

    Energy Technology Data Exchange (ETDEWEB)

    Dehn, Larissa-A. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States)]. E-mail: ftld@uaf.edu; Follmann, Erich H. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States); Thomas, Dana L. [Department of Mathematical Sciences, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-6660 (United States); Sheffield, Gay G. [Alaska Department of Fish and Game, Fairbanks, Division of Wildlife Conservation, Fairbanks, Alaska, 99701-1599 (United States); Rosa, Cheryl [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States); Duffy, Lawrence K. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States); O' Hara, Todd M. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States)

    2006-06-01

    Tissues of subsistence-harvested Arctic mammals were analyzed for silver (Ag), cadmium (Cd), and total mercury (THg). Muscle (or total body homogenates of potential fish and invertebrate prey) was analyzed for stable carbon ({delta} {sup 13}C) and nitrogen ({delta} {sup 15}N) isotopes to establish trophic interactions within the Arctic food chain. Food web magnification factors (FWMFs) and biomagnification factors for selected predator-prey scenarios (BMFs) were calculated to describe pathways of heavy metals in the Alaskan Arctic. FWMFs in this study indicate that magnification of selected heavy metals in the Arctic food web is not significant. Biomagnification of Cd occurs mainly in kidneys; calculated BMFs are higher for hepatic THg than renal THg for all predator-prey scenarios with the exception of polar bears (Ursus maritimus). In bears, the accumulation of renal THg is approximately 6 times higher than in liver. Magnification of hepatic Ag is minimal for all selected predator-prey scenarios. Though polar bears occupy a higher trophic level than belugas (Delphinapterus leucas), based on {delta} {sup 15}N, the metal concentrations are either not statistically different between the two species or lower for bears. Similarly, concentrations of renal and hepatic Cd are significantly lower or not statistically different in polar bears compared to ringed (Phoca hispida) and bearded seals (Erignathus barbatus), their primary prey. THg, on the other hand, increased significantly from seal to polar bear tissues. Mean {delta} {sup 15}N was lowest in muscle of Arctic fox (Alopex lagopus) and foxes also show the lowest levels of Hg, Cd and Ag in liver and kidney compared to the other species analyzed. These values are in good agreement with a diet dominated by terrestrial prey. Metal deposition in animal tissues is strongly dependent on biological factors such as diet, age, sex, body condition and health, and caution should be taken when interpreting magnification of

  5. Trophic relationships in an Arctic food web and implications for trace metal transfer

    International Nuclear Information System (INIS)

    Dehn, Larissa-A.; Follmann, Erich H.; Thomas, Dana L.; Sheffield, Gay G.; Rosa, Cheryl; Duffy, Lawrence K.; O'Hara, Todd M.

    2006-01-01

    Tissues of subsistence-harvested Arctic mammals were analyzed for silver (Ag), cadmium (Cd), and total mercury (THg). Muscle (or total body homogenates of potential fish and invertebrate prey) was analyzed for stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopes to establish trophic interactions within the Arctic food chain. Food web magnification factors (FWMFs) and biomagnification factors for selected predator-prey scenarios (BMFs) were calculated to describe pathways of heavy metals in the Alaskan Arctic. FWMFs in this study indicate that magnification of selected heavy metals in the Arctic food web is not significant. Biomagnification of Cd occurs mainly in kidneys; calculated BMFs are higher for hepatic THg than renal THg for all predator-prey scenarios with the exception of polar bears (Ursus maritimus). In bears, the accumulation of renal THg is approximately 6 times higher than in liver. Magnification of hepatic Ag is minimal for all selected predator-prey scenarios. Though polar bears occupy a higher trophic level than belugas (Delphinapterus leucas), based on δ 15 N, the metal concentrations are either not statistically different between the two species or lower for bears. Similarly, concentrations of renal and hepatic Cd are significantly lower or not statistically different in polar bears compared to ringed (Phoca hispida) and bearded seals (Erignathus barbatus), their primary prey. THg, on the other hand, increased significantly from seal to polar bear tissues. Mean δ 15 N was lowest in muscle of Arctic fox (Alopex lagopus) and foxes also show the lowest levels of Hg, Cd and Ag in liver and kidney compared to the other species analyzed. These values are in good agreement with a diet dominated by terrestrial prey. Metal deposition in animal tissues is strongly dependent on biological factors such as diet, age, sex, body condition and health, and caution should be taken when interpreting magnification of dynamic and actively regulated trace metals

  6. Trophic condition of the volcanic Lake Nemi (Central Italy: environmental factors and planktonic communities in a changing environment

    Directory of Open Access Journals (Sweden)

    Fiorenza G. MARGARITORA

    2005-08-01

    Full Text Available Lake Nemi is an interesting case of anthropogenic overexploitation which has caused its progressive environmental deterioration in the past decades. On this lake historical data about the trophic situation are available from 1975 to 1984. The research performed in 2002-03, about ten years after the diversion of urban waste waters, concerned a biological investigation on the phyto- and zooplanktonic communities, integrated with a physico-chemical analysis. The aims of our study are to evaluate the current water quality of the lake and compare it with the water quality observed in 1982-1983, when all biotic and abiotic components indicated a heavily compromised hypereutrophic condition. The water quality data and the comparison with a previous study point out that the biological aspects have partially changed (increased number of Cyanobacteria and phytoplanktonic taxa, particularly Clorophyta and Dinophyta; zooplankton composition changed at a species level, with the appearance of taxa associated to light trophic conditions, and the physico-chemical conditions significantly improved. The mean transparency, dissolved oxygen, nutrients and chlorophyll-a concentrations have all improved. Mean annual temperature at different depths increased, probably due to differences in climatic period and the lowering of the lake surface level (from 32.5 to 27.5 m in 1982 and 2002, respectively. Our results indicate a general improving trend in water quality is taking place since the diversion of waste water discharges. The present abiotic characteristics of the lake allow the phytoplankton to distribute itself in the whole epilimnion, and the zooplankton in the whole water column. A possible further improvement is hypothesized, and the constraints represented by excessive water level lowering and water temperature increasing are also discussed.

  7. Interannual and long-term changes in the trophic state of a multibasin lake: Effects of morphology, climate, winter aeration, and beaver activity

    Science.gov (United States)

    Robertson, Dale M.; Rose, William; Reneau, Paul C.

    2016-01-01

    Little St. Germain Lake (LSG), a relatively pristine multibasin lake in Wisconsin, USA, was examined to determine how morphologic (internal), climatic (external), anthropogenic (winter aeration), and natural (beaver activity) factors affect the trophic state (phosphorus, P; chlorophyll, CHL; and Secchi depth, SD) of each of its basins. Basins intercepting the main flow and external P sources had highest P and CHL and shallowest SD. Internal loading in shallow, polymictic basins caused P and CHL to increase and SD to decrease as summer progressed. Winter aeration used to eliminate winterkill increased summer internal P loading and decreased water quality, while reductions in upstream beaver impoundments had little effect on water quality. Variations in air temperature and precipitation affected each basin differently. Warmer air temperatures increased productivity throughout the lake and decreased clarity in less eutrophic basins. Increased precipitation increased P in the basins intercepting the main flow but had little effect on the isolated deep West Bay. These relations are used to project effects of future climatic changes on LSG and other temperate lakes.

  8. Trophic habits of mesostigmatid mites associated with bark beetles in Mexico

    Science.gov (United States)

    M. Patricia Chaires-Grijalva; Edith G. Estrada-Venegas; Armando Equihua-Martinez; John C. Moser; Stacy R. Blomquist

    2016-01-01

    Samples of bark and logs damaged by bark beetles were collected from 16 states of Mexico from 2007 to 2012. Fifteen bark beetle species were found within the bark and log samples and were examined for phoretic mites and arthropod associates. Thirty-three species of mesostigmatid mites were discovered within the samples. They were identified in several trophic guilds...

  9. First approach to the trophic ecology and diet of the rainbow runner, Elagatis bipinnulata (Quoy and Gaimard, 1825) (Pisces: Carangidae), in the central Colombian Caribbean

    International Nuclear Information System (INIS)

    Garcia Ramirez, Camilo Bernardo; Posada, Camila

    2014-01-01

    The rainbow runner (Elagatis bipinnulata) scores high in trophic level (4.24) but it is not a voracious fish (Q/B = 10.8). its diet is dominated by the dwarf herring (Jenkinsia lamprotaenia), eats more in the dry season, than in the rainy season and significantly more in the afternoon that in the morning suggesting preference for daylight feeding.

  10. Effects of near-future ocean acidification, fishing, and marine protection on a temperate coastal ecosystem.

    Science.gov (United States)

    Cornwall, Christopher E; Eddy, Tyler D

    2015-02-01

    Understanding ecosystem responses to global and local anthropogenic impacts is paramount to predicting future ecosystem states. We used an ecosystem modeling approach to investigate the independent and cumulative effects of fishing, marine protection, and ocean acidification on a coastal ecosystem. To quantify the effects of ocean acidification at the ecosystem level, we used information from the peer-reviewed literature on the effects of ocean acidification. Using an Ecopath with Ecosim ecosystem model for the Wellington south coast, including the Taputeranga Marine Reserve (MR), New Zealand, we predicted ecosystem responses under 4 scenarios: ocean acidification + fishing; ocean acidification + MR (no fishing); no ocean acidification + fishing; no ocean acidification + MR for the year 2050. Fishing had a larger effect on trophic group biomasses and trophic structure than ocean acidification, whereas the effects of ocean acidification were only large in the absence of fishing. Mortality by fishing had large, negative effects on trophic group biomasses. These effects were similar regardless of the presence of ocean acidification. Ocean acidification was predicted to indirectly benefit certain species in the MR scenario. This was because lobster (Jasus edwardsii) only recovered to 58% of the MR biomass in the ocean acidification + MR scenario, a situation that benefited the trophic groups lobsters prey on. Most trophic groups responded antagonistically to the interactive effects of ocean acidification and marine protection (46%; reduced response); however, many groups responded synergistically (33%; amplified response). Conservation and fisheries management strategies need to account for the reduced recovery potential of some exploited species under ocean acidification, nonadditive interactions of multiple factors, and indirect responses of species to ocean acidification caused by declines in calcareous predators. © 2014 Society for Conservation Biology.

  11. Cyanobacteria Community Dynamics and Trophic Status of Intensive Shrimp (Litopenaeus vannamei Farming Pond in Situbondo East Java Indonesia

    Directory of Open Access Journals (Sweden)

    Dian Aliviyanti

    2017-09-01

    Full Text Available The objective of this study was to analyze the dynamics community structure of Cyanobacteria and trophic status in ponds of intensive shrimp culture (Litopenaeus vannamei in Situbondo based on Trophic Diatom Index (TDI.  The ex post facto research was conducted in situ in the hamlet of Pond Mutiara Mas III Klatakan Situbondo East Java Indonesia.  Observation of Cyanobacteria and Diatoms community structure were done every week during four cycles of shrimp farming ponds.  Cycle of shrimp farming ponds is the times for enlargement process of the shrimps from seed to mature which ranges from 90-120 days.  The dependent variables were the density of Cyanobacteria and Diatoms community, as well as chemical parameters nitrite and orthophosphate.  Trophic status was determined from TDI be counted from data of diatom density.  All of the data were then classified using cluster and biplot analysis program PAST Ver. 3.11 to discribe the profile of ecosystem quality.  The research results showed that there were four taxa of Cyanobacteria during farming cycle which the highest density was found from the genus of Oscillatoria.  Based on the value of TDI, we found that the trophic status of water in shrimps pond during the production process was eutrophic until hyper-eutrophic.  The water quality was decreases along with the length of incubation time.

  12. Trophic ecology of Lepidoptera larvae associated with woody vegetation in a savanna ecosystem

    CSIR Research Space (South Africa)

    Scholtz, CH

    1982-06-01

    Full Text Available This study represents a quantitative survey of a Lepidoptera community and deals with the trophic ecology of the 27 species of foliage-feeding Lepidoptera on the eight dominant woody plants in the Burkea africana-Eragrostis pallens savanna...

  13. Bioenergetics, Trophic Ecology, and Niche Separation of Tunas.

    Science.gov (United States)

    Olson, R J; Young, J W; Ménard, F; Potier, M; Allain, V; Goñi, N; Logan, J M; Galván-Magaña, F

    Tunas are highly specialized predators that have evolved numerous adaptations for a lifestyle that requires large amounts of energy consumption. Here we review our understanding of the bioenergetics and feeding dynamics of tunas on a global scale, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas. Food consumption balances bioenergetics expenditures for respiration, growth (including gonad production), specific dynamic action, egestion, and excretion. Tunas feed across the micronekton and some large zooplankton. Some tunas appear to time their life history to take advantage of ephemeral aggregations of crustacean, fish, and molluscan prey. Ontogenetic and spatial diet differences are substantial, and significant interdecadal changes in prey composition have been observed. Diet shifts from larger to smaller prey taxa highlight ecosystem-wide changes in prey availability and diversity and provide implications for changing bioenergetics requirements into the future. Where tunas overlap, we show evidence of niche separation between them; resources are divided largely by differences in diet percentages and size ranges of prey taxa. The lack of long-term data limits the ability to predict impacts of climate change on tuna feeding behaviour. We note the need for systematic collection of feeding data as part of routine monitoring of these species, and we highlight the advantages of using biochemical techniques for broad-scale analyses of trophic relations. We support the continued development of ecosystem models, which all too often lack the regional-specific trophic data needed to adequately investigate climate and fishing impacts. © 2016 Elsevier Ltd. All rights reserved.

  14. Effects on the function of three trophic levels in marine plankton communities under stress from the antifouling compound zinc pyrithione

    International Nuclear Information System (INIS)

    Hjorth, M.; Dahlloef, I.; Forbes, V.E.

    2006-01-01

    This study aimed to investigate functional responses of natural marine planktonic communities to stress from the antifouling compound zinc pyrithione (ZPT). Isotope labelling techniques ( 14 C) were applied to study bacterial incorporation of leucine, photosynthetic activity of phytoplankton and grazing of labelled prey by zooplankton communities for 6 days after exposures to nominal concentrations of 0, 5, 25, 50 nM ZPT in a mesocosm experiment in Isefjord, Denmark. Significant direct effects were visible on chlorophyll a concentrations, which decreased in all exposed communities, to between 48 and 36% of control concentrations on Day 3, 1 day after the last exposure. Phytoplankton activities were also significantly affected on Day 3 with activities between 9 and 26% of control levels, as was zooplankton activities in the 25 and 50 nM exposures. In the 50 nM exposure the total community zooplankton activity was reduced to 25 ± 4%, and per individual to 46 ± 11% of control levels. Bacterial communities showed positive indirect effects with high activities (up to 183 ± 40%) due to higher amounts of available substrate from algal death. Pollution induced community tolerance analyses performed on phytoplankton and bacterial communities at the end of the experiment indicated a development of increased tolerance for phytoplankton in the 50 nM exposed communities, whereas there were no changes in tolerance in the bacterial communities. Multivariate analysis of the integrated functional response by the plankton communities revealed a significant difference (p < 0.05) between exposed communities compared to controls in the first 3 days after last exposure and in the end of the experiment. The study provides evidence of diverse effects on the functions of marine plankton communities under stress from a pollutant. Direct effects lead to cascading indirect effects throughout the community, eventually causing different developments. Continuous exposure to ZPT could lead to

  15. Trophic interactions among grouper (Epinephelus marginatus), octopus (Octopus vulgaris) and red lobster (Palinurus elephas) in the Western Mediterranean

    OpenAIRE

    Quetglas, A. (Antoni); Reñones, O. (Olga); Goñi, R. (Raquel)

    2001-01-01

    In the present paper a first evaluation of the trophic interactions between grouper, octopus and spiny red lobster in the western Mediterranean is presented. The efficiency of octopus preying on lobsters is also estimated from trap catches. Grouper and octopus base their diet on the same major taxonomic groups and this is reflected in the values of diet overlap. Trophic diversity of grouper and octopus is also very similar. The estimation of the octopus efficiency preying on lobsters shows th...

  16. Effects of spatial subsidies and habitat structure on the foraging ecology and size of geckos.

    Directory of Open Access Journals (Sweden)

    Amy A Briggs

    Full Text Available While it is well established that ecosystem subsidies--the addition of energy, nutrients, or materials across ecosystem boundaries--can affect consumer abundance, there is less information available on how subsidy levels may affect consumer diet, body condition, trophic position, and resource partitioning among consumer species. There is also little information on whether changes in vegetation structure commonly associated with spatial variation in subsidies may play an important role in driving consumer responses to subsidies. To address these knowledge gaps, we studied changes in abundance, diet, trophic position, size, and body condition of two congeneric gecko species (Lepidodactylus spp. that coexist in palm dominated and native (hereafter dicot dominated forests across the Central Pacific. These forests differ strongly both in the amount of marine subsidies that they receive from seabird guano and carcasses, and in the physical structure of the habitat. Contrary to other studies, we found that subsidy level had no impact on the abundance of either gecko species; it also did not have any apparent effects on resource partitioning between species. However, it did affect body size, dietary composition, and trophic position of both species. Geckos in subsidized, dicot forests were larger, had higher body condition and more diverse diets, and occupied a much higher trophic position than geckos found in palm dominated, low subsidy level forests. Both direct variation in subsidy levels and associated changes in habitat structure appear to play a role in driving these responses. These results suggest that variation in subsidy levels may drive important behavioral responses in predators, even when their numerical response is limited. Strong changes in trophic position of consumers also suggest that subsidies may drive increasingly complex food webs, with longer overall food chain length.

  17. Effects of spatial subsidies and habitat structure on the foraging ecology and size of geckos

    Science.gov (United States)

    Briggs, Amy A.; Young, Hillary S.; McCauley, Douglas J.; Hathaway, Stacie A.; Dirzo, Rodolfo; Fisher, Robert N.

    2012-01-01

    While it is well established that ecosystem subsidies—the addition of energy, nutrients, or materials across ecosystem boundaries—can affect consumer abundance, there is less information available on how subsidy levels may affect consumer diet, body condition, trophic position, and resource partitioning among consumer species. There is also little information on whether changes in vegetation structure commonly associated with spatial variation in subsidies may play an important role in driving consumer responses to subsidies. To address these knowledge gaps, we studied changes in abundance, diet, trophic position, size, and body condition of two congeneric gecko species (Lepidodactylus spp.) that coexist in palm dominated and native (hereafter dicot dominated) forests across the Central Pacific. These forests differ trongly both in the amount of marine subsidies that they receive from seabird guano and carcasses, and in the physical structure of the habitat. Contrary to other studies, we found that subsidy level had no impact on the abundance of either gecko species; it also did not have any apparent effects on resource partitioning between species. However, it did affect body size, dietary composition, and trophic position of both species. Geckos in subsidized, dicot forests were larger, had higher body condition and more diverse diets, and occupied a much higher trophic position than geckos found in palm dominated, low subsidy level forests. Both direct variation in subsidy levels and associated changes in habitat structure appear to play a role in driving these responses. These results suggest that variation in subsidy levels may drive important behavioral responses in predators, even when their numerical response is limited. Strong changes in trophic position of consumers also suggest that subsidies may drive increasingly complex food webs, with longer overall food chain length.

  18. Predator diversity effects in an exotic freshwater food web.

    Science.gov (United States)

    Naddafi, Rahmat; Rudstam, Lars G

    2013-01-01

    Cascading trophic interactions are often defined as the indirect effects of a predator on primary producers through the effect of the predator on herbivores. These effects can be both direct through removal of herbivores [density-mediated indirect interactions (DMIIs)] or indirect through changes in the behavior of the herbivores [trait-mediated indirect interactions (TMIIs)]. How the relative importance of these two indirect interactions varies with predator diversity remains poorly understood. We tested the effect of predator diversity on both TMIIs and DMIIs on phytoplankton using two competitive invasive dreissenid mussel species (zebra mussel and quagga mussel) as the herbivores and combinations of one, two or all three species of the predators pumpkinseed sunfish, round goby, and rusty crayfish. Predators had either direct access to mussels and induced both TMII and DMII, or no direct access and induced only TMII through the presence of risk cues. In both sets of treatments, the predators induced a trophic cascade which resulted in more phytoplankton remaining with predators present than with only mussels present. The trophic cascade was weaker in three-predator and two-predator treatments than in one-predator treatments when predators had direct access to dreissenids (DMIIs and TMIIs). Crayfish had higher cascading effects on phytoplankton than both pumpkinseed and round goby. Increased predator diversity decreased the strength of DMIIs but had no effect on the strength of TMIIs. The strength of TMIIs was higher with zebra than quagga mussels. Our study suggests that inter-specific interference among predators in multi-species treatments weakens the consumptive cascading effects of predation on lower trophic levels whereas the importance of predator diversity on trait mediated effects depends on predator identity.

  19. Predator diversity effects in an exotic freshwater food web.

    Directory of Open Access Journals (Sweden)

    Rahmat Naddafi

    Full Text Available Cascading trophic interactions are often defined as the indirect effects of a predator on primary producers through the effect of the predator on herbivores. These effects can be both direct through removal of herbivores [density-mediated indirect interactions (DMIIs] or indirect through changes in the behavior of the herbivores [trait-mediated indirect interactions (TMIIs]. How the relative importance of these two indirect interactions varies with predator diversity remains poorly understood. We tested the effect of predator diversity on both TMIIs and DMIIs on phytoplankton using two competitive invasive dreissenid mussel species (zebra mussel and quagga mussel as the herbivores and combinations of one, two or all three species of the predators pumpkinseed sunfish, round goby, and rusty crayfish. Predators had either direct access to mussels and induced both TMII and DMII, or no direct access and induced only TMII through the presence of risk cues. In both sets of treatments, the predators induced a trophic cascade which resulted in more phytoplankton remaining with predators present than with only mussels present. The trophic cascade was weaker in three-predator and two-predator treatments than in one-predator treatments when predators had direct access to dreissenids (DMIIs and TMIIs. Crayfish had higher cascading effects on phytoplankton than both pumpkinseed and round goby. Increased predator diversity decreased the strength of DMIIs but had no effect on the strength of TMIIs. The strength of TMIIs was higher with zebra than quagga mussels. Our study suggests that inter-specific interference among predators in multi-species treatments weakens the consumptive cascading effects of predation on lower trophic levels whereas the importance of predator diversity on trait mediated effects depends on predator identity.

  20. Image processing developments and applications for water quality monitoring and trophic state determination

    International Nuclear Information System (INIS)

    Blackwell, R.J.

    1982-03-01

    Remote sensing data analysis of water quality monitoring is evaluated. Data anaysis and image processing techniques are applied to LANDSAT remote sensing data to produce an effective operational tool for lake water quality surveying and monitoring. Digital image processing and analysis techniques were designed, developed, tested, and applied to LANDSAT multispectral scanner (MSS) data and conventional surface acquired data. Utilization of these techniques facilitates the surveying and monitoring of large numbers of lakes in an operational manner. Supervised multispectral classification, when used in conjunction with surface acquired water quality indicators, is used to characterize water body trophic status. Unsupervised multispectral classification, when interpreted by lake scientists familiar with a specific water body, yields classifications of equal validity with supervised methods and in a more cost effective manner. Image data base technology is used to great advantage in characterizing other contributing effects to water quality. These effects include drainage basin configuration, terrain slope, soil, precipitation and land cover characteristics