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Sample records for trophic levels effects

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

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    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.

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

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    Wasserman, Ryan J; Noyon, Margaux; Avery, Trevor S; Froneman, P William

    2013-01-01

    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.

  3. 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.

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

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    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)

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

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    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

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

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    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...

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

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    Jardine, Timothy D; Kidd, Karen A; O' Driscoll, Nelson

    2013-05-15

    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 of primary consumers and predatory insects in lower pH waters led to lower BMFs, these feeding groups showed insignificant relationships between Hg and pH; thus, altered BMFs associated with dietary concentrations can dampen the effects of environmental conditions on Hg concentrations. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Trophic levels and trophic tangles: the prevalence of omnivory in real food webs.

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    Thompson, Ross M; Hemberg, Martin; Starzomski, Brian M; Shurin, Jonathan B

    2007-03-01

    The concept of trophic levels is one of the oldest in ecology and informs our understanding of energy flow and top-down control within food webs, but it has been criticized for ignoring omnivory. We tested whether trophic levels were apparent in 58 real food webs in four habitat types by examining patterns of trophic position. A large proportion of taxa (64.4%) occupied integer trophic positions, suggesting that discrete trophic levels do exist. Importantly however, the majority of those trophic positions were aggregated around integer values of 0 and 1, representing plants and herbivores. For the majority of the real food webs considered here, secondary consumers were no more likely to occupy an integer trophic position than in randomized food webs. This means that, above the herbivore trophic level, food webs are better characterized as a tangled web of omnivores. Omnivory was most common in marine systems, rarest in streams, and intermediate in lakes and terrestrial food webs. Trophic-level-based concepts such as trophic cascades may apply to systems with short food chains, but they become less valid as food chains lengthen.

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

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    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.

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

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    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

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

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    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.

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

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    Jacob M Peters

    Full Text Available 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 δ(15N values increased from plants to insects and we observed significant non-trophic (15N enrichment in the metamorphosis from larvae to adult.

  13. Habitat fragmentation differentially affects trophic levels and alters behavior in a multi-trophic marine system.

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    Rielly-Carroll, Elizabeth; Freestone, Amy L

    2017-03-01

    Seagrass, an important subtidal marine ecosystem, is being lost at a rate of 110 km 2  year -1 , leading to fragmented seagrass seascapes. Habitat fragmentation is predicted to affect trophic levels differently, with higher trophic levels being more sensitive, stressing the importance of a multi-trophic perspective. Utilizing the trophic relationship between the blue crab (Callinectes sapidus) and hard clam (Mercenaria mercenaria), where adult blue crabs prey on juvenile blue crabs, and juvenile blue crabs prey on small hard clams, we examined whether predation rates, abundance, and behavior of predators and prey differed between continuous and fragmented seagrass in a multi-trophic context at two sites in Barnegat Bay, NJ. We tested the hypothesis that fragmented habitats would differentially affect trophic levels within a tri-trophic system, and our results supported this hypothesis. Densities of adult blue crabs were higher in fragmented than continuous habitats. Densities of juvenile blue crabs, the primary predator of hard clams, were lower in fragmented habitats than continuous, potentially due to increased predation by adult blue crabs. Clams experienced lower predation and burrowed to a shallower depth in fragmented habitats than in continuous habitat, likely due in part to the low densities of juvenile blue crabs, their primary predator. Our results suggest that while trophic levels are differentially affected, the impact of habitat fragmentation may be stronger on intermediate rather than top trophic levels in some marine systems.

  14. Contrasting effects of heat pulses on different trophic levels, an experiment with a herbivore-parasitoid model system.

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    Schreven, Stijn J J; Frago, Enric; Stens, Annemiek; de Jong, Peter W; van Loon, Joop J A

    2017-01-01

    Under predicted global climate change, species will be gradually exposed to warmer temperatures, and to a more variable climate including more intense and more frequent heatwaves. Increased climatic variability is expected to have different effects on species and ecosystems than gradual warming. A key challenge to predict the impact of climate change is to understand how temperature changes will affect species interactions. Herbivorous insects and their natural enemies belong to some of the largest groups of terrestrial animals, and thus they have a great impact on the functioning of ecosystems and on the services these ecosystems provide. Here we studied the life history traits of the plant-feeding insect Plutella xylostella and its specialist endoparasitoid Diadegma semiclausum, when exposed to a daily heat pulse of 5 or 10°C temperature increase during their entire immature phase. Growth and developmental responses differed with the amplitude of the heat pulse and they were different between host and parasitoid, indicating different thermal sensitivity of the two trophic levels. With a +5°C heat pulse, the adult parasitoids were larger which may result in a higher fitness, whereas a +10°C heat pulse retarded parasitoid development. These results show that the parasitoid is more sensitive than its host to brief intervals of temperature change, and this results in either positive or negative effects on life history traits, depending on the amplitude of the heat pulse. These findings suggest that more extreme fluctuations may disrupt host-parasitoid synchrony, whereas moderate fluctuations may improve parasitoid fitness.

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

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    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.

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

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    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.

  17. Functional trait diversity across trophic levels determines herbivore impact on plant community biomass.

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    Deraison, Hélène; Badenhausser, Isabelle; Loeuille, Nicolas; Scherber, Christoph; Gross, Nicolas

    2015-12-01

    Understanding the consequences of trophic interactions for ecosystem functioning is challenging, as contrasting effects of species and functional diversity can be expected across trophic levels. We experimentally manipulated functional identity and diversity of grassland insect herbivores and tested their impact on plant community biomass. Herbivore resource acquisition traits, i.e. mandible strength and the diversity of mandibular traits, had more important effects on plant biomass than body size. Higher herbivore functional diversity increased overall impact on plant biomass due to feeding niche complementarity. Higher plant functional diversity limited biomass pre-emption by herbivores. The functional diversity within and across trophic levels therefore regulates the impact of functionally contrasting consumers on primary producers. By experimentally manipulating the functional diversity across trophic levels, our study illustrates how trait-based approaches constitute a promising way to tackle existing links between trophic interactions and ecosystem functioning. © 2015 John Wiley & Sons Ltd/CNRS.

  18. Biodiversity enhances ecosystem multifunctionality across trophic levels and habitats

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    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

  19. Shift in trophic level of Mediterranean mariculture species.

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    Tsikliras, Athanassios C; Stergiou, Konstantinos I; Adamopoulos, Nikolaos; Pauly, Daniel; Mente, Eleni

    2014-08-01

    The mean trophic level of the farmed fish species in the Mediterranean has been increasing. We examined the farming-up hypothesis (i.e., the increase in the production of high-trophic-level species) in the Mediterranean by determining the trophic level of the aquafeeds (i.e., what the fish are fed) of 5 species of farmed marine fishes: common dentex (Dentex dentex), common pandora (Pagellus erythrinus), European seabass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), and red porgy (Pagrus sp.). The mean trophic level of aquafeed used in mariculture from 1950 to 2011 was higher (3.93) than the prey farmed fish consume in the wild (3.72) and increased at a faster rate (0.48/decade) compared with that based on their diets in the wild (0.43/decade). Future expected replacement of the fishmeal and oil in aquafeeds by plant materials may reverse the farming-up trend, although there are a number of concerns regarding operational, nutritional, environmental, and economic issues. The farming-up reversal can be achieved in an ecologically friendly manner by facilitating the mariculture of low-trophic-level fishes and by promoting high efficiency in the use of living marine resources in aquafeeds. © 2014 Society for Conservation Biology.

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

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    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.

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

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    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.

  2. 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

  3. Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels.

    Science.gov (United States)

    Dickman, Elizabeth M; Newell, Jennifer M; González, María J; Vanni, Michael J

    2008-11-25

    The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not been tested experimentally in food chains with 3 or more trophic levels. In a field experiment manipulating light, nutrients, and food-chain length, we show that FCE is constrained by algal food quality and food-chain length. FCE across 3 trophic levels (phytoplankton to carnivorous fish) was highest under low light and high nutrients, where algal quality was best as indicated by taxonomic composition and nutrient stoichiometry. In 3-level systems, FCE was constrained by the efficiency at which both herbivores and carnivores converted food into production; a strong nutrient effect on carnivore efficiency suggests a carryover effect of algal quality across 3 trophic levels. Energy transfer efficiency from algae to herbivores was also higher in 2-level systems (without carnivores) than in 3-level systems. Our results support the hypothesis that FCE is strongly constrained by light, nutrients, and food-chain length and suggest that carryover effects across multiple trophic levels are important. Because many environmental perturbations affect light, nutrients, and food-chain length, and many ecological services are mediated by FCE, it will be important to apply these findings to various ecosystem types.

  4. Indirect effects of otter trawling on the condition and trophic level of Nephrops and flatfish in the Kattegat

    DEFF Research Database (Denmark)

    Hiddink, Jan Geert; Balestrin, Stephen; Moranta, Joan

    The fishing gear used in bottom trawl fisheries cause mortality of benthic invertebrates and this can decrease the long-term availability of prey to exploited fish species by reducing the abundance of benthic invertebrates. Alternatively, low trawling levels could increase food production for spe...

  5. Toxicity of CeO2 nanoparticles at different trophic levels--effects on diatoms, chironomids and amphibians.

    Science.gov (United States)

    Bour, Agathe; Mouchet, Florence; Verneuil, Laurent; Evariste, Lauris; Silvestre, Jérôme; Pinelli, Eric; Gauthier, Laury

    2015-02-01

    The aim of the present work is to provide wider information on the toxicity of cerium dioxide nanoparticles (CeO2 NPs) in aquatic environments, by studying the toxicity of two types of CeO2 NPs for four species (diatoms Nitzschia palea, the sediment-dwelling invertebrate Chironomus riparius, and the amphibian larvae Xenopus laevis and Pleurodeles waltl.). The two types of CeO2 NPs have different intrinsic properties: some of them are small citrate-coated spheres (2-5 nm), and the others are larger uncoated plates (20-60 nm). Acute toxicity (mortality at 48 or 96 h, depending on the test-organism) was assessed for the four species, from 0.1 to 100 mg L(-1) of NPs. Sub-lethal effects were assessed on chironomids exposed between 0.01 and 1 mg L(-1) of NPs. Mortality, growth inhibition and genotoxic effects were evaluated on amphibian larvae from 0.1 to 10 mg L(-1). Results reveal that no acute toxicity occurs on any species after short exposures, even at the highest concentrations. Mortality (35%) is observed on Xenopus larvae after 12d of exposure at the highest concentration of one type of NPs. No significant effects were observed on chironomids during chronic exposure. Xenopus larvae growth was inhibited from 1 mg L(-1) of both NPs while growth inhibition is observed on Pleurodeles only at the highest concentration of one type of NPs. No genotoxicity was observed on Xenopus but Pleurodeles exhibited dose-dependent genotoxic effects when exposed to one type of NPs. Observed differences in toxicity are discussed focusing on the studied compartment, routes of exposure, species and NPs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. 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...... Sensitivity Profile approach to 10,003 terrestrial and aquatic phenological data sets, spatially matched to temperature and precipitation data, to quantify variation in climate sensitivity. The direction, magnitude and timing of climate sensitivity varied markedly among organisms within taxonomic and trophic...... groups. Despite this variability, we detected systematic variation in the direction and magnitude of phenological climate sensitivity. Secondary consumers showed consistently lower climate sensitivity than other groups. We used mid-century climate change projections to estimate that the timing...

  7. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ13C and δ15N

    Directory of Open Access Journals (Sweden)

    Christopher D. Stallings

    2015-03-01

    Full Text Available 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 δ13C and δ15N 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 δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C 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

  8. 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...

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

    Science.gov (United States)

    García, Camilo B; Contreras, Cristian Camilo

    2011-09-01

    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 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.

  10. Importance of accurate trophic level determination by nitrogen isotope of amino acids for trophic magnification studies: A review.

    Science.gov (United States)

    Won, Eun-Ji; Choi, Bohyung; Hong, Seongjin; Khim, Jong Seong; Shin, Kyung-Hoon

    2018-04-02

    During the last several decades, persistent organic pollutants and metals cause great concern for their toxicity in organisms as well as for their bioaccumulation and/or trophic transfer through the food chains in ecosystems. A large number of studies therefore have focused on the trophic levels of organisms to illustrate food web structure, as a critical component in the study of pollutant dynamics and biomagnification. The trends in biomagnification of pollutants in food webs indeed provide fundamental information about the properties and fates of pollutants in ecosystems. The trophic magnification supports the establishment of a reliable trophic structure, which can further aid the understanding of the transport and exposure routes of contaminants in accumulation and risk assessments. Recently, efforts to interpret the food web structure using carbon and nitrogen stable isotope ratios have contributed to better understanding of the fate of pollutants in the ecosystem. However, it is known that this isotope analysis of bulk ones has many weaknesses, particularly for uncertainties on the estimate of trophic levels and therefore of magnification factors for studied organisms, enough to support a regulatory interpretation. In this review, we collate studies that investigated biomagnification characteristics of pollutants in aquatic ecosystems, along with calculated trophic magnification factors. Moreover, we introduce a novel approach, compound-specific stable isotope analysis of nitrogen in amino acids, to establish reliable food web structures and accurate trophic levels for biomagnification studies. This method promises to provide sound results for interpreting the influence of the pollutant in organisms, along with their bioaccumulation and magnification characteristics, as well as that in ecosystem. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. 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.

  12. Levels of chlorinated, brominated, and perfluorinated contaminants in birds of prey spanning multiple trophic levels.

    Science.gov (United States)

    Yordy, Jennifer E; Rossman, Sam; Ostrom, Peggy H; Reiner, Jessica L; Bargnesi, Keely; Hughes, Stacy; Elliot, James D

    2013-04-01

    Birds of prey occupy high trophic levels and can consequently bioaccumulate high levels of environmental contaminants. To evaluate exposure to past- and current-use pollutants, we measured legacy contaminants (i.e., polychlorinated biphenyls [PCBs]; organochlorine pesticides, e.g., DDT), contaminants of emerging concern (polybrominated diphenyl ethers [PBDEs]; perfluorinated compounds [PFCs]), and stable isotopes (δ(13)C, δ(15)N) in 26 birds of prey (10 species) from coastal South Carolina (USA) sampled in 2009 and 2010. Nitrogen isotope ratios (δ(15)N) ranged from 5.2% to 13.7%, indicating the birds of prey spanned two to three trophic levels. Legacy contaminant levels were highly variable but generally comparable to levels reported previously for birds of prey in the southeast US, suggesting exposure has not declined substantially over the past 40 yr. Despite their status as newly emerging environmental contaminants, PFC levels were within the same order of magnitude as legacy contaminants. Although PBDEs were less prevalent, levels were among the greatest observed in wildlife to date (∑PBDEs max. 200 μg/g lipid). Relative contaminant profiles also varied between birds of prey utilizing low and high trophic levels; specifically PFCs contributed to a larger proportion of the contaminant burden in birds utilizing high trophic levels, whereas the legacy pesticide mirex was a larger contributor in low-trophic-level birds, indicating that relative exposure is in part dependent on foraging ecology. This study demonstrates that birds of prey continue to face exposure to legacy contaminants as well as newly emerging contaminants at levels of concern.

  13. Host-plant species modifies the diet of an omnivore feeding on three trophic levels

    NARCIS (Netherlands)

    Magalhães, S.; Janssen, A.; Montserrat, M.; Sabelis, M.W.

    2005-01-01

    The diet choice of omnivores feeding on two adjacent trophic levels (either plants and herbivores or herbivores and predators) has been studied extensively. However, omnivores usually feed on more than two trophic levels, and this diet choice and its consequences for population dynamics have hardly

  14. 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.

  15. Foraging behaviour at the fourth trophic level: a comparative study of host location in aphid hyperparasitoids

    NARCIS (Netherlands)

    Buitenhuis, R.; Vet, L.E.M.; Boivin, G.; Brodeur, J.

    2005-01-01

    In studies of foraging behaviour in a multitrophic context, the fourth trophic level has generally been ignored. We used four aphid hyperparasitoid species: Dendrocerus carpenteri (Curtis) (Hymenoptera: Megaspilidae), Asaphes suspensus Walker (Hymenoptera: Pteromalidae), Alloxysta victrix (Westwood)

  16. Forest fragmentation reduces parasitism via species loss at multiple trophic levels.

    Science.gov (United States)

    Fenoglio, Maria Silvina; Srivastava, Diane; Valladares, Graciela; Cagnolo, Luciano; Salvo, Adriana

    2012-11-01

    Although there is accumulating evidence from artificially assembled communities that reductions of species diversity result in diminished ecosystem functioning, it is not yet clear how real-world changes in diversity affect the flow of energy between trophic levels in multi-trophic contexts. In central Argentina, forest fragmentation has led to species loss of plants, herbivore and parasitoid insects, decline in trophic processes (herbivory and parasitism), and food web contraction. Here we examine if and how loss of parasitoid species following fragmentation causes decreased parasitism rates, by analyzing food webs of leaf miners and parasitoids from 19 forest fragments of decreasing size. We asked three questions: Do reductions in parasitoid richness following fragmentation directly or indirectly affect parasitism rate? Are changes in community parasitism rate driven by changes in the parasitism rate of individual leaf miner species, or changes in leaf miner composition, or both? Which traits of species determine the effects of food web change on parasitism rates? We found that habitat loss initiated a bottom-up cascade of extinctions from plants to leaf miners to parasitoids, with reductions in parasitoid richness ultimately driving decreases in parasitism rates. This relationship between parasitoid richness and parasitism depended on changes in the relative abundance (but not occurrence) of leaf miners such that parasitoid-rich fragments were dominated by leaf miner species that supported high rates of parasitism. Surprisingly, we found that only a small subset of species in the food web could account for much of the increase in parasitism with parasitoid richness: lepidopteran miners that attained exceptionally high densities in some fragments and their largely specialist parasitoids. How specialized a parasitoid is, and the relative abundance of leaf miners, had important effects on the diversity-parasitism rate relationship, but not other leaf miner traits

  17. Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels

    OpenAIRE

    Dickman, Elizabeth M.; Newell, Jennifer M.; González, María J.; Vanni, Michael J.

    2008-01-01

    The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not ...

  18. Effects of the pyrethroid insecticide, cypermethrin, on a freshwater community studied under field conditions. I. Direct and indirect effects on abundance measures of organisms at different trophic levels

    Energy Technology Data Exchange (ETDEWEB)

    Friberg-Jensen, Ursula; Wendt-Rasch, Lina; Woin, Per; Christoffersen, Kirsten

    2003-05-29

    The effects of the pyrethroid insecticide cypermethrin on a natural freshwater community were studied in small in situ enclosures over an 11-day period. The experiment was conducted in a eutrophic lake using a regression design that included three untreated controls and a gradient of six unreplicated cypermethrin concentrations, ranging from 0.01 to 6.1 {mu}g/l. This paper is the first in a series of two, and describes the fate of cypermethrin and its effects on the abundance of crustaceans, rotifers, protozoans (cilliates and heterotrophic nanoflagellates (HNF)) and bacteria and the biomass of periphytic and planktonic algae. The concentration of cypermethrin decreased quickly during the experiment, with a half-life of 48 h for the total and 25 h for the dissolved fractions of cypermethrin, respectively. Cypermethrin proved to be acutely toxic to crustaceans in enclosures receiving nominal cypermethrin concentrations of {>=}0.13 {mu}g/l. No Effect Concentration (NEC) and median Effect Concentration (EC{sub 50}) for the total crustacean community and cladoceran and copepod subgroups ranged between 0.02-0.07 and 0.04-0.17 {mu}g/l, respectively, with copepods being less sensitive than cladocerans. The abundance of rotifers, protozoans and bacteria and the chlorophyll-a concentration of planktonic and periphytic algae was significantly related to the concentration of cypermethrin. All groups proliferated within 2-7 days after the cypermethrin application in those enclosures where the abundance of crustaceans was seriously affected by cypermethrin (i.e. {>=}0.13 {mu}g/l). We hypothesise that the proliferation of rotifers, protozoans, bacteria and algae was due to a reduced grazer control from crustaceans and thereby mediated indirectly by cypermethrin. The results of this experiment provide knowledge on how an entire microplankton community may respond to pyrethroids in nature, and the indirect effects observed on the community clearly demonstrates the necessity of

  19. Effects of the pyrethroid insecticide, cypermethrin, on a freshwater community studied under field conditions. I. Direct and indirect effects on abundance measures of organisms at different trophic levels

    International Nuclear Information System (INIS)

    Friberg-Jensen, Ursula; Wendt-Rasch, Lina; Woin, Per; Christoffersen, Kirsten

    2003-01-01

    The effects of the pyrethroid insecticide cypermethrin on a natural freshwater community were studied in small in situ enclosures over an 11-day period. The experiment was conducted in a eutrophic lake using a regression design that included three untreated controls and a gradient of six unreplicated cypermethrin concentrations, ranging from 0.01 to 6.1 μg/l. This paper is the first in a series of two, and describes the fate of cypermethrin and its effects on the abundance of crustaceans, rotifers, protozoans (cilliates and heterotrophic nanoflagellates (HNF)) and bacteria and the biomass of periphytic and planktonic algae. The concentration of cypermethrin decreased quickly during the experiment, with a half-life of 48 h for the total and 25 h for the dissolved fractions of cypermethrin, respectively. Cypermethrin proved to be acutely toxic to crustaceans in enclosures receiving nominal cypermethrin concentrations of ≥0.13 μg/l. No Effect Concentration (NEC) and median Effect Concentration (EC 50 ) for the total crustacean community and cladoceran and copepod subgroups ranged between 0.02-0.07 and 0.04-0.17 μg/l, respectively, with copepods being less sensitive than cladocerans. The abundance of rotifers, protozoans and bacteria and the chlorophyll-a concentration of planktonic and periphytic algae was significantly related to the concentration of cypermethrin. All groups proliferated within 2-7 days after the cypermethrin application in those enclosures where the abundance of crustaceans was seriously affected by cypermethrin (i.e. ≥0.13 μg/l). We hypothesise that the proliferation of rotifers, protozoans, bacteria and algae was due to a reduced grazer control from crustaceans and thereby mediated indirectly by cypermethrin. The results of this experiment provide knowledge on how an entire microplankton community may respond to pyrethroids in nature, and the indirect effects observed on the community clearly demonstrates the necessity of multispecies

  20. 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.

  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. Decreasing Stoichiometric Resource Quality Drives Compensatory Feeding across Trophic Levels in Tropical Litter Invertebrate Communities.

    Science.gov (United States)

    Jochum, Malte; Barnes, Andrew D; Ott, David; Lang, Birgit; Klarner, Bernhard; Farajallah, Achmad; Scheu, Stefan; Brose, Ulrich

    2017-07-01

    Living organisms are constrained by both resource quantity and quality. Ecological stoichiometry offers important insights into how the elemental composition of resources affects their consumers. If resource quality decreases, consumers can respond by shifting their body stoichiometry, avoiding low-quality resources, or up-regulating feeding rates to maintain the supply of required elements while excreting excess carbon (i.e., compensatory feeding). We analyzed multitrophic consumer body stoichiometry, biomass, and feeding rates along a resource-quality gradient in the litter of tropical forest and rubber and oil-palm plantations. Specifically, we calculated macroinvertebrate feeding rates based on consumer metabolic demand and assimilation efficiency. Using linear mixed effects models, we assessed resource-quality effects on macroinvertebrate detritivore and predator communities. We did not detect shifts in consumer body stoichiometry or decreases in consumer biomass in response to declining resource quality, as indicated by increasing carbon-to-nitrogen ratios. However, across trophic levels, we found a strong indication of decreasing resource quality leading to increased consumer feeding rates through altered assimilation efficiency and community body size structure. Our study reveals the influence of resource quality on multitrophic consumer feeding rates and suggests compensatory feeding to be more common across consumer trophic levels than was formerly known.

  3. Soil microcosm for testing the effects of chemical pollutants on soil fauna communities and trophic structure

    Energy Technology Data Exchange (ETDEWEB)

    Parmelee, R.W. (Ohio State Univ., Columbus, OH (United States). Dept. of Entomology); Wentsel, R.S.; Phillips, C.T.; Checkai, R.T. (Army CRDEC, Aberdeen Proving Ground, MD (United States)); Simini, M. (Geo-Centers, Inc., Aberdeen Proving Ground, MD (United States))

    1993-08-01

    A microcosm technique is presented that uses community and trophic-level analysis of soil nematodes and microarthropods to determine the effects of chemicals on soil systems. Forest soil was treated with either copper, p-nitrophenol, or trinitrotoluene. Nematodes were sorted into bacterivore, fungivore, herbivore, and omnivore-predator trophic groups, and a hatchling category. Microarthropods were sorted to the acarine suborders Prostigmata, Mesostigmata, and Oribatida; the insectan order Collembola; and a miscellaneous group. Omnivore-predator nematodes and meso-stigmatid and oribatid mites were the groups most sensitive to copper and were significantly reduced at levels as low as 100 [mu]g g[sup [minus]1] copper. Total nematode and microarthropod numbers declined above 200 [mu]g g[sup [minus]1] copper. Trophic structure analysis suggested that high sensitivity of nematode predators to intermediate levels of copper reduced predation on herbivore nematodes and resulted in greater numbers of nematodes compared to controls. p-Nitrophenol was very toxic to the nematode community, and all trophic groups were significantly reduced above 20 [mu]g g[sup [minus]1]. However, there was no effect of p-nitrophenol on microarthropods. Trinitrotoluene had no significant negative effect on total abundance of either groups of soil fauna, but oribatids were significantly reduced at 200 [mu]g g[sup [minus]1]. The results demonstrated that soil nematodes and microarthropods were sensitive indicators of environmental contaminants and that trophic-structure and community analysis has the potential to detect more subtle indirect effects of chemicals on soil food-web structure. The authors conclude that microcosms with field communities of soil microfauna offer high resolution of the ecotoxicological effects of chemicals in complex soil systems.

  4. Importance of species interactions to community heritability: a genetic basis to trophic-level interactions.

    Science.gov (United States)

    Bailey, Joseph K; Wooley, Stuart C; Lindroth, Richard L; Whitham, Thomas G

    2006-01-01

    Recent community genetics studies have shown that specific genotypes of a host plant support distinct arthropod communities. Building upon these findings, we examined the hypothesis that a trophic community consisting of cottonwood trees, a galling herbivore and avian predators could also be related to the genetics of the host tree. We found genetic correlations among phytochemistry of individual tree genotypes, the density of a galling herbivore, and the intensity of avian predation on these herbivores. We detected significant broad-sense heritability of these interactions that range from H(B)2 = 0.70 to 0.83. The genetic basis of these interactions tended to increase across trophic levels suggesting that small genetic changes in the cottonwood phenotype could have major consequences at higher trophic levels affecting species interactions and energy flow. These findings show a heritable basis to trophic-level interactions indicating that there is a significant genetic basis to community composition and energy flow that is predictable by plant genotype. Our data clearly link plant genetics to patterns of avian foraging and show that species interactions are important components of community heritability and ecosystem processes. Overall, these data support the hypothesis that evolution of plant traits can alter trophic-level interactions and community composition.

  5. 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.

  6. Feeding habits and trophic ecology of Dasyatis longa (Elasmobranchii: Myliobatiformes): sexual, temporal and ontogenetic effects.

    Science.gov (United States)

    López-García, J; Navia, A F; Mejía-Falla, P A; Rubio, E A

    2012-04-01

    Sexual, ontogenic and temporal effects in the diet of Dasyatis longa were evaluated to determine feeding habits and trophic ecology. Numeric indices and the index of relative importance were applied to establish the feeding strategy of the species. Independence of the diet with respect to sex, dry or rainy season and size was evaluated with contingency tables, correspondence analysis and multivariate analysis (MANOVA). The trophic relationships of D. longa (by sex and size intervals) were determined using Levin's niche breadth index and the Pianka's diet overlap index and their significance was determined by null models. The trophic level for each size interval and the species was also calculated. Dasyatis longa showed a narrow niche breadth feeding mainly on shrimps and fishes and its diet was dependent on size, but not on sex or season. Juvenile individuals (class I) fed on shrimps, sub-adults (class II) on fishes and adults (class III) on stomatopods. Significant overlaps between size classes I and II and classes II and III were found. The trophic level shows D. longa to be a secondary or tertiary consumer. Due to considerable fishing pressures on shrimps, the principal prey of D. longa, it will be important to determine their ability to adapt to changes in prey populations. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

  7. 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

  8. 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.

  9. The Influence of Mean Trophic Level on Biomass and Production in Marine Ecosystems

    Science.gov (United States)

    Woodson, C. B.; Schramski, J.

    2016-02-01

    The oceans have faced rapid removal of top predators causing a reduction in the mean trophic level of many marine ecosystems due to fishing down the food web. However, estimating the pre-exploitation biomass of the ocean has been difficult. Historical population sizes have been estimated using population dynamics models, archaeological or historical records, fisheries data, living memory, ecological monitoring data, genetics, and metabolic theory. In this talk, we expand on the use of metabolic theory by including complex trophic webs to estimate pre-exploitation levels of marine biomass. Our results suggest that historical marine biomass could be as much as 10 times higher than current estimates and that the total carrying capacity of the ocean is sensitive to mean trophic level and trophic web complexity. We further show that the production levels needed to support the added biomass are possible due to biomass accumulation and predator-prey overlap in regions such as fronts. These results have important implications for marine biogeochemical cycling, fisheries management, and conservation efforts.

  10. The movement of the radioactive cesium in the food chain by the trophic levels of arthropod

    International Nuclear Information System (INIS)

    Tanaka, Sota; Takahashi, Sentaro; Adati, Taro; Takahashi, Tomoyuki

    2016-01-01

    The Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant accident occurred on March 11, 2011 and released large amounts of radioactive materials into the environment. Those radioactive materials were deposited on the soil surface and circulated in the ecosystem after the accident. The movement of Cs is highly affected by the food chain circulation in the ecosystem from a long-term perspective. Therefore, in order to observe the Cs movement in the food chain, we investigated the Cs concentration in arthropods, including insects. In this research, we collected three dominant arthropods in Fukushima: the Japanese grasshopper (Oxya yezoensis), the Emma mole cricket (Teleogryllus emma) and the Joro spider (Nephila clavata). These arthropods can be classified into three trophic levels in the food chain: herbivorous for the grasshopper, omnivorous for the field cricket, and carnivorous for the web spider. Then we observed the temporal changes of Cs concentrations in the trophic levels of the arthropods from 2012 to 2014. The results suggest that the arthropods in higher trophic levels accumulate Cs in higher concentrations than that of the arthropods in lower trophic levels. (author)

  11. 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.

  12. Application of food waste based diets in polyculture of low trophic level fish: effects on fish growth, water quality and plankton density.

    Science.gov (United States)

    Mo, Wing Yin; Cheng, Zhang; Choi, Wai Ming; Man, Yu Bon; Liu, Yihui; Wong, Ming Hung

    2014-08-30

    Food waste was collected from local hotels and fish feed pellets were produced for a 6 months long field feeding trial. Three types of fish feed pellets (control diet: Jinfeng® 613 formulated feed, contains mainly fish meal, plant product and fish oil; Diet A: food waste based diet without meat and 53% cereal; Diet B: food waste based diet with 25% meat and 28% cereal) were used in polyculture fish ponds to investigate the growth of fish (grass carp, bighead and mud carp), changes in water quality and plankton density. No significant differences in the levels of nitrogen and phosphorous compounds of water body were observed between 3 fish ponds after the half-year feeding trial, while pond receiving Diet A had the highest density of plankton. The food waste combination of Diet B seems to be a better formulation in terms of the overall performance on fish growth. Copyright © 2014. Published by Elsevier Ltd.

  13. Mercury distribution in different tissues and trophic levels of fish from a tropical reservoir, Brazil

    Directory of Open Access Journals (Sweden)

    Daniele Kasper

    Full Text Available Concentrations of organic (OrgHg and inorganic mercury (InorgHg were assessed in different fish tissues (liver, muscle, kidney, gut and gonads and trophic levels collected in an impacted tropical reservoir in southeastern Brazil. Organic mercury concentrations in muscle were remarkably higher in the carnivorous species Hoplias malabaricus and Oligosarcus hepsetus. The ratios of OrgHg in relation to total mercury (%OrgHg in muscle also varied according to the species trophic level: 93% for carnivores, 84% for omnivores, 73% for algivores/planktivores and 58% for detritivores. The %OrgHg in the gut tissue of carnivores (78% was much higher than that found in omnivores (30%, possibly reflecting a process of trophic biomagnification in the reservoir. On the other hand, the InorgHg concentrations in muscle decreased with the trophic level increase, suggesting that this form of mercury did not biomagnify through the food web. Gonads contained the least total mercury, and approximately all of this mercury was represented by the organic form (83 to 98%. The kidney and the liver of all fish species contained less than 50% OrgHg. We suggest that the low %OrgHg in the liver is related to different capacities or strategies of OrgHg detoxification by the fish.

  14. Ecosystem structure and trophic level to the oceanographic conditions around the waters of Jeju Island.

    Science.gov (United States)

    Choi, Young Min; Yoo, Joon Taek; Choi, Jung Hwa; Choi, Kwang Ho; Kim, Jin Koo; Kim, Yeong Seup; Kim, Jong Bin

    2008-07-01

    The water around Jeju Island was characterized by the Tsushima warm current (TWC) being high temperature and salinity and the Yellow sea cold bottom water (YSCBW) being low temperature and salinity We investigated the diversity indices, community structures and trophic level of fish species collected by trawl net in the waters around Jeju Island during April 2004-August 2005. We also presented ecosystem structure estimated by combination of trophic level and the oceanographic condition. There were totally distributed 301 species in the survey area during April 2004-August 2005, regionally 151-229 species in TWC and 75-154 in YSCBW. Shannon's diversity indices (H') of TWC were 2.95-3.39, being higher than those of YSCBW (2.11-2.40), and species richness (R) of TWC were 10.93-18.33, being also higher than those of YSCBW (6.96-12.48), except the values of October 2004. A total of 7429 individuals of 98 species was seasonally examined for their dietary composition in the survey area during 2004-2005. Of which, 3,682 individuals were observed with prey organisms. Standardized diet composition and trophic level estimates were calculated for predators in the survey area being influenced by TWC and YSCBW Trophic level values were diverged with range from 3.23 of the small pelagic to 4.39 of the goose fish, depending on the taxonomic group. The analysis of trophic level values showed that ecosystem structure was different between TWC and YSCBW during April 2004-August 2005.

  15. Evaluation of Filtration and DNA Extraction Methods for Environmental DNA Biodiversity Assessments across Multiple Trophic Levels

    Directory of Open Access Journals (Sweden)

    Anni Djurhuus

    2017-10-01

    Full Text Available Metabarcoding of marine environmental DNA (eDNA, originating from tissue, cells, or extracellular DNA, offers the opportunity to survey the biological composition of communities across multiple trophic levels from a non-invasive seawater sample. Here we compare results of eDNA metabarcoding of multiple trophic levels from individual seawater samples collected from a kelp forest in Monterey Bay, California in order to establish methods for future cross-trophic level eDNA analysis. Triplicate 1 L water samples were filtered using five different 47 mm diameter membrane filters (PVDF, PES, GFF, PCTE, and NC and DNA was extracted from triplicates of each filter-type using three widely-used extraction methods (the DNeasy Blood and Tissue kit, the MoBio PowerWater DNA Isolation kit, and standard phenol/chloroform methods resulting in 45 individual eDNA samples prepared with 15 workflow combinations. Each DNA extract was amplified using PCR primers for the 16S rRNA gene (microorganisms; Bacteria and Archaea, 18S rRNA gene (phytoplankton, and the 12S rRNA gene (vertebrates, and PCR products were sequenced on an Illumina MiSeq platform. The richness and community composition of microbial, phytoplankton, and vertebrate OTUs were not significantly different between any of the 0.2 μm pore-size filter types extracted with the DNeasy or MoBio kits. However, phenol/chloroform extraction resulted in significantly different community structures. This study provides insight into multiple choices for extraction and filtration methods to use eDNA metabarcoding for biodiversity assessment of multiple trophic levels from a single sample. We recommend any combination of either DNeasy or MoBio with PES, PCTE, PVDF, or NC filters for a cross trophic level comparison.

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

    Science.gov (United States)

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

    2009-06-01

    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. summation operator PCBs and DDE concentrations generally increased with trophic level and marine input, with the exception of the freshwater sites, while summation operator PBDEs, hydroxylated-PBDEs and hydroxylated-PCBs increased with marine input, but were independent of trophic level. The relationships for summation operator PCBs 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 (delta(15)N) and -0.4+/-0.2 (delta(13)C). We conclude that trophic level and marine influence are significant factors influencing PCB and DDE concentrations in eagles. However

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

    Energy Technology Data Exchange (ETDEWEB)

    Hamish Elliott, Kyle, E-mail: haliaeetus@gmail.com [Department of Zoology, Z320 Duff Roblin Building, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Cesh, Lillian S. [Department of Biological Sciences, Centre for Wildlife Ecology, Simon Fraser University, Burnaby, British Columbia, R3T 2N2 (Canada); Dooley, Jessica A. [Department of Biology, California State University Northridge, Northridge, CA 91330 (United States); Letcher, Robert J. [Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, ON, K1A 0H3 (Canada); Elliott, John E. [Science and Technology Branch, Environment Canada, Pacific Wildlife Research Centre, 5421 Robertson Road, Delta, B.C., V4K 3N2 (Canada)

    2009-06-01

    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. {Sigma}PCBs and DDE concentrations generally increased with trophic level and marine input, with the exception of the freshwater sites, while {Sigma}PBDEs, hydroxylated-PBDEs and hydroxylated-PCBs increased with marine input, but were independent of trophic level. The relationships for {Sigma}PCBs 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 ({delta}{sup 15}N) and - 0.4 {+-}0.2 ({delta}{sup 13}C). We conclude that trophic level and marine influence are significant factors influencing PCB and DDE concentrations in eagles. However, trophic level in

  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. 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.

  20. 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

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

    OpenAIRE

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

    2007-01-01

    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 Triod...

  2. Higher Trophic Levels Overwhelm Climate Change Impacts on Terrestrial Ecosystem Functioning.

    Directory of Open Access Journals (Sweden)

    Shannon L Pelini

    Full Text Available Forest floor food webs play pivotal roles in carbon cycling, but they are rarely considered in models of carbon fluxes, including soil carbon dioxide emissions (respiration, under climatic warming. The indirect effects of invertebrates on heterotrophic (microbial and invertebrate respiration through interactions with microbial communities are significant and will be altered by warming. However, the interactive effects of invertebrates and warming on heterotrophic respiration in the field are poorly understood. In this study we combined field and common garden laboratory approaches to examine relationships between warming, forest floor food web structure, and heterotrophic respiration. We found that soil animals can overwhelm the effects of warming (to 5 degrees Celsius above ambient on heterotrophic respiration. In particular, the presence of higher trophic levels and burrowing detritivores strongly determined heterotrophic respiration rates in temperate forest soils. These effects were, however, context-dependent, with greater effects in a lower-latitude site. Without isolating and including the significant impact of invertebrates, climate models will be incomplete, hindering well-informed policy decisions.

  3. 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.

  4. 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.

  5. 2013 status of the Lake Ontario lower trophic levels

    Science.gov (United States)

    Holeck, Kristen T.; Rudstam, Lars G.; Hotaling, Christopher; McCullough, Russ D.; Lemon, Dave; Pearsall, Web; Lantry, Jana R.; Connerton, Michael J.; LaPan, Steve; Trometer, Betsy; Lantry, Brian F.; Walsh, Maureen; Weidel, Brian C.

    2014-01-01

    abundant in the summer, peaking at ~7 mg/m3in the offshore. Bythotrephes peaked in October (~0.7 mg/m3), but Bythotrephes biomass was at its lowest biomass in both offshore and nearshore stations since 2005.Summer nearshore zooplankton density and biomass have declined significantly since 1995 at rates of 9-10% per year. Nearshore epilimnetic zooplankton density and biomass have remained stable since 2005 at low levels relative to previous years.Summer offshore zooplankton density and biomass in the epilimnion of Lake Ontario have also declined since 1995 at rates of 10-14% per year, but those declines are marginally significant; density declined significantly in the long-term (since 1981) but has remained at a lower stable level since 2005.Bosminid and cyclopoid copepod biomass declined significantly in nearshore waters. The same pattern occurred in the offshore but declines were significant for bosminids and marginally significant for cyclopoid copepods. Daphnid biomass has also declined significantly in the nearshore.The decline in Daphnid biomass nearshore and Bythotrephes biomass offshore and nearshore is indicative of increased planktivory by alewife. Significant declines in Bosminid and cyclopoid copepod biomass is indicative of increased invertebrate predation by Cercopagis and Bythotrephes in recent years.

  6. 2014 status of the Lake Ontario lower trophic levels

    Science.gov (United States)

    Holeck, Kristen T.; Rudstam, Lars G.; Hotaling, Christopher; McCullough, Russ D.; Lemon, Dave; Pearsall, Web; Lantry, Jana; Connerton, Michael J.; LaPan, Steve; Biesinger, Zy; Lantry, Brian F.; Walsh, Maureen; Weidel, Brian C.

    2015-01-01

    Soluble reactive phosphorus (SRP) concentrations have been stable in nearshore and offshore habitats since 1998 (0.4 – 3.3 μg/L). SRP concentrations were low in 2014; Apr/May – Oct mean values were Water Quality Agreement of 1978 for offshore waters of Lake Ontario. TP concentrations were low at both nearshore and offshore locations; Apr/May – Oct mean values from individual sites ranged from 4.6 – 9.1 μg/L. Spring TP has declined significantly in the longer data series (since 1981), but not since 1995 indicating stable nutrient loading into Lake Ontario for nearly two decades. It averaged 7.8 μg/L in the nearshore and 5.6 μg/L in the offshore in 2014.Chlorophyll-a and secchi depth values are indicative of oligotrophic conditions in nearshore and offshore habitats. Offshore summer chlorophyll-a declined significantly in both the short- (2000-2014) and long-term (1981-2014) time series at a rate of 4-6% per year. Nearshore chlorophyll-a increased after 2003 but then declined again after 2009. Epilimnetic chlorophyll-a averaged between 0.6 and 1.6 μg/L across sites with no difference between nearshore and offshore habitats. Apr/May – Oct Secchi depth ranged from 4.0 m to 10.8 m at individual sites and was higher in the offshore (average 9.1 m) than nearshore (5.9 m).In 2014, Apr/May – Oct epilimnetic zooplankton density, size, and biomass were not different between the offshore and the nearshore, and there were no differences in epilimnetic biomass between offshore and nearshore areas for any of the zooplankton groups.Zooplankton density and biomass peaked in September, an atypical pattern. This coincided with peaks in calanoid copepod, daphnid, and Holopedium biomass. Holopedium biomass in the nearshore increased significantly since 1995.The predatory cladoceran Cercopagis continued to be abundant in the summer, peaking at ~10 mg/m3in the offshore. Bythotrephes biomass was at its lowest level since 2005 in both offshore and nearshore habitats

  7. 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

  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. 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

  10. 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

    -Arctic tri-trophic system of flowers, insects and waders (Charadriiformes), with latent factors representing phenology (timing of life history events) and performance (abundance or reproduction success) for each trophic level. The effects derived from the model demonstrated that the time of snowmelt directly...... from the tri-trophic community presented here emphasise that effects of climate on species in consumer-resource systems may propagate through trophic levels...

  11. 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

  12. Contrasting effects of aquatic subsidies on a terrestrial trophic cascade.

    Science.gov (United States)

    Graf, Nadin; Bucher, Roman; Schäfer, Ralf B; Entling, Martin H

    2017-05-01

    Subsidies from adjacent ecosystems can alter recipient food webs and ecosystem functions, such as herbivory. Emerging aquatic insects from streams can be an important prey in the riparian zone. Such aquatic subsidies can enhance predator abundances or cause predators to switch prey, depending on the herbivores. This can lead to an increase or decrease of in situ herbivores and herbivory. We examined the effects of aquatic subsidies on a simplified terrestrial food web consisting of two types of herbivores, plants and predators (spiders). In our six-week experiment, we focused on the prey choice of the spiders by excluding predator immigration and reproduction. In accordance with predator switching, survival of leafhoppers increased in the presence of aquatic subsidies. By contrast, the presence of aquatic subsidies indirectly reduced weevils and herbivory. Our study shows that effects of aquatic subsidies on terrestrial predators can propagate through the food web in contrasting ways. Thereby, the outcome of the trophic cascade is determined by the prey choice of predators. © 2017 The Author(s).

  13. 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.

  14. Demographic and phenotypic effects of human mediated trophic subsidy on a large Australian lizard (Varanus varius): meal ticket or last supper?

    Science.gov (United States)

    Jessop, Tim S; Smissen, Peter; Scheelings, Franciscus; Dempster, Tim

    2012-01-01

    Humans are increasingly subsidizing and altering natural food webs via changes to nutrient cycling and productivity. Where human trophic subsidies are concentrated and persistent within natural environments, their consumption could have complex consequences for wild animals through altering habitat preferences, phenotypes and fitness attributes that influence population dynamics. Human trophic subsidies conceptually create both costs and benefits for animals that receive increased calorific and altered nutritional inputs. Here, we evaluated the effects of a common terrestrial human trophic subsidies, human food refuse, on population and phenotypic (comprising morphological and physiological health indices) parameters of a large predatory lizard (∼2 m length), the lace monitor (Varanus varius), in southern Australia by comparison with individuals not receiving human trophic subsidies. At human trophic subsidies sites, lizards were significantly more abundant and their sex ratio highly male biased compared to control sites in natural forest. Human trophic subsidies recipient lizards were significantly longer, heavier and in much greater body condition. Blood parasites were significantly lower in human trophic subsidies lizards. Collectively, our results imply that human trophic subsidized sites were especially attractive to adult male lace monitors and had large phenotypic effects. However, we cannot rule out that the male-biased aggregations of large monitors at human trophic subsidized sites could lead to reductions in reproductive fitness, through mate competition and offspring survival, and through greater exposure of eggs and juveniles to predation. These possibilities could have negative population consequences. Aggregations of these large predators may also have flow on effects to surrounding food web dynamics through elevated predation levels. Given that flux of energy and nutrients into food webs is central to the regulation of populations and their

  15. The differential impact of a native and a non-native ragwort species (Senecioneae) on the first and second trophic level of the rhizosphere food web

    NARCIS (Netherlands)

    Harkes, Paula; Verhoeven, Ava; Sterken, Mark G.; Snoek, L. Basten; van den Elsen, Sven J.J.; Mooijman, Paul J.W.; Quist, Casper W.; Vervoort, Mariëtte T.W.; Helder, Johannes

    2017-01-01

    © 2017 Nordic Society Oikos. Whereas the impact of exotic plant species on above-ground biota is relatively well-documented, far less is known about the effects of non-indigenous plants on the first and second trophic level of the rhizosphere food web. Here, rhizosphere communities of the invasive

  16. The differential impact of a native and a non-native ragwort species (Senecioneae) on the first and second trophic level of the rhizosphere food web

    NARCIS (Netherlands)

    Harkes, Paula; Verhoeven, Ava; Sterken, Mark G; Snoek, L. Basten; van den Elsen, Sven J.J.; Mooijman, Paul J.W.; Quist, Casper W.; Vervoort, Mariëtte T.W.; Helder, Johannes

    2017-01-01

    Whereas the impact of exotic plant species on above-ground biota is relatively well-documented, far less is known about the effects of non-indigenous plants on the first and second trophic level of the rhizosphere food web. Here, rhizosphere communities of the invasive narrow-leaved ragwort Senecio

  17. Data from: The differential impact of a native and a non-native ragwort species (Senecioneae) on the first and second trophic level of the rhizosphere food web

    NARCIS (Netherlands)

    Harkes, P.; Verhoeven, Ava; Sterken, M.G.; Snoek, L.B.; Elsen, van den S.J.J.; Mooijman, P.J.W.; Quist, C.W.; Vervoort, M.T.W.; Helder, J.

    2017-01-01

    Whereas the impact of exotic plant species on above-ground biota is relatively well-documented, far less is known about the effects of non-indigenous plants on the first and second trophic level of the rhizosphere food web. Here, rhizosphere communities of the invasive narrow-leaved ragwort Senecio

  18. Experimental demonstration of a trophic cascade in the Galápagos rocky subtidal: Effects of consumer identity and behavior

    Science.gov (United States)

    Witman, Jon D.; Smith, Franz; Novak, Mark

    2017-01-01

    In diverse tropical webs, trophic cascades are presumed to be rare, as species interactions may dampen top-down control and reduce their prevalence. To test this hypothesis, we used an open experimental design in the Galápagos rocky subtidal that enabled a diverse guild of fish species, in the presence of each other and top predators (sea lions and sharks), to attack two species of sea urchins grazing on benthic algae. Time-lapse photography of experiments on natural and experimental substrates revealed strong species identity effects: only two predator species–blunthead triggerfish (Pseudobalistes naufragium) and finescale triggerfish (Balistes polylepis)–drove a diurnal trophic cascade extending to algae, and they preferred large pencil urchins (Eucidaris galapagensis) over green urchins (Lytechinus semituberculatus). Triggerfish predation effects were strong, causing a 24-fold reduction of pencil urchin densities during the initial 21 hours of a trophic cascade experiment. A trophic cascade was demonstrated for pencil urchins, but not for green urchins, by significantly higher percent cover of urchin-grazed algae in cages that excluded predatory fish than in predator access (fence) treatments. Pencil urchins were more abundant at night when triggerfish were absent, suggesting that this species persists by exploiting a nocturnal predation refuge. Time-series of pencil urchin survivorship further demonstrated per capita interference effects of hogfish and top predators. These interference effects respectively weakened and extended the trophic cascade to a fourth trophic level through behavioral modifications of the triggerfish-urchin interaction. We conclude that interference behaviors capable of modifying interaction strength warrant greater attention as mechanisms for altering top-down control, particularly in speciose food webs. PMID:28430794

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

    Science.gov (United States)

    Berdjeb, Lyria; Pollet, Thomas; Domaizon, Isabelle; Jacquet, Stéphan

    2011-04-29

    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. The presence of grazers (i.e. stimulation of viral production (compared to the treatment with no eukaryotic predators) was more variable between lakes than between seasons, with the highest value having been recorded in the mesotrophic lake (+30%). Viral lysis and grazing activities acted additively to sustain high bacterial production in all experiments. Nevertheless, the stimulation of bacterial production was more variable between seasons than between lakes, with the highest values obtained in summer (+33.5% and +37.5% in Lakes Bourget and Annecy, respectively). The presence of both predators (nanoflagellates and viruses) did not seem to have a clear influence upon bacterial community structure according to the four experiments. Our results highlight the importance of a synergistic effect, i.e. the

  20. The Effects of Spatial Scale on Trophic Interactions

    NARCIS (Netherlands)

    Koppel, J. van de; Bardgett, R.D.; Bengtsson, J.; Rodriguez-Barrueco, C.; Rietkerk, M.G.; Wassen, M.J.; Wolters, V.

    2005-01-01

    Food chain models have dominated empirical studies of trophic interactions in the past decades, and have lead to important insights into the factors that control ecological communities. Despite the importance of food chain models in instigating ecological investigations, many empirical studies

  1. The effects of spatial scale on trophic interactions

    NARCIS (Netherlands)

    Koppel, J. van de; Bardgett, R.D.; Bengtsson, J.; Rodriguez-Barrueco, C.; Rietkerk, M.G.; Wassen, M.J.; Wolters, V.

    2005-01-01

    Food chain models have dominated empirical studies of trophic interactions in the past decades, and have lead to important insights into the factors that control ecological communities. Despite the importance of food chain models in instigating ecological investigations, many empirical studies

  2. The effects of spatial scale on trophic interactions

    NARCIS (Netherlands)

    Van de Koppel, J.; Bardgett, R.D.; Bengtsson, J.; Rodriguez-Barrueco, C.; Rietkerk, M.; Wassen, M.J.; Wolters, V.

    2005-01-01

    Food chain models have dominated empirical studies of trophic interactions in the past decades, and have lead to important insights into the factors that control ecological communities. Despite the importance of food chain models in instigating ecological investigations, many empirical studies still

  3. The effects of fire on ant trophic assemblage and sex allocation.

    Science.gov (United States)

    Caut, Stephane; Jowers, Michael J; Arnan, Xavier; Pearce-Duvet, Jessica; Rodrigo, Anselm; Cerda, Xim; Boulay, Raphaël R

    2014-01-01

    Fire plays a key role in ecosystem dynamics worldwide, altering energy flows and species community structure and composition. However, the functional mechanisms underlying these effects are not well understood. Many ground-dwelling animal species can shelter themselves from exposure to heat and therefore rarely suffer direct mortality. However, fire-induced alterations to the environment may change a species' relative trophic level within a food web and its mode of foraging. We assessed how fire could affect ant resource utilization at different scales in a Mediterranean forest. First, we conducted isotopic analyses on entire ant species assemblages and their potential food resources, which included plants and other arthropods, in burned and unburned plots 1 year postfire. Second, we measured the production of males and females by nests of a fire-resilient species, Aphaenogaster gibbosa, and analyzed the differences in isotopic values among workers, males, and females to test whether fire constrained resource allocation. We found that, in spite of major modifications in biotic and abiotic conditions, fire had little impact on the relative trophic position of ant species. The studied assemblage was composed of species with a wide array of diets. They ranged from being mostly herbivorous to completely omnivorous, and a given species' trophic level was the same in burned and unburned plots. In A. gibbosa nests, sexuals had greater δ(15)N values than workers in both burned and unburned plots, which suggests that the former had a more protein-rich diet than the latter. Fire also appeared to have a major effect on A. gibbosa sex allocation: The proportion of nests that produced male brood was greater on burned zones, as was the mean number of males produced per nest with the same reproductive investment. Our results show that generalist ants with relatively broad diets maintained a constant trophic position, even following a major disturbance like fire. However, the

  4. 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.

  5. Ecosystem functions across trophic levels are linked to functional and phylogenetic diversity.

    Directory of Open Access Journals (Sweden)

    Patrick L Thompson

    Full Text Available 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.

  6. 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.

  7. 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.

  8. Mercury accumulation by lower trophic-level organisms in lentic systems within the Guadalupe River watershed, California

    Science.gov (United States)

    Kuwabara, James S.; Topping, Brent R.; Moon, Gerald E.; Husby, Peter; Lincoff, Andrew; Carter, James L.; Croteau, Marie-Noële

    2005-01-01

    The water columns of four reservoirs (Almaden, Calero, Guadalupe and Lexington Reservoirs) and an abandoned quarry pit filled by Alamitos Creek drainage for recreational purposes (Lake Almaden) were sampled on September 14 and 15, 2004 to provide the first measurements of mercury accumulation by phytoplankton and zooplankton in lentic systems (bodies of standing water, as in lakes and reservoirs) within the Guadalupe River watershed, California. Because of widespread interest in ecosystem effects associated with historic mercury mining within and downgradient of the Guadalupe Riverwatershed, transfer of mercury to lower trophic-level organisms was examined. The propensity of mercury to bioaccumulate, particularly in phytoplankton and zooplankton at the base of the food web, motivated this attempt to provide information in support of developing trophic-transfer and solute-transport models for the watershed, and hence in support of subsequent evaluation of load-allocation strategies. Both total mercury and methylmercury were examined in these organisms. During a single sampling event, replicate samples from the reservoir water column were collected and processed for dissolved-total mercury, dissolved-methylmercury, phytoplankton mercury speciation, phytoplankton taxonomy and biomass, zooplankton mercury speciation, and zooplankton taxonomy and biomass. The timing of this sampling event was coordinated with sampling and analysis of fish from these five water bodies, during a period of the year when vertical stratification in the reservoirs generates a primary source of methylmercury to the watershed. Ancillary data, including dissolved organic carbon and trace-metal concentrations as well as vertical profiles of temperature, dissolved oxygen, specific conductance and pH, were gathered to provide a water-quality framework from which to compare the results for mercury. This work, in support of the Guadalupe River Mercury Total Maximum Daily Load (TMDL) Study, provides

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

    Science.gov (United States)

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

    2010-01-01

    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. PMID:20566867

  10. Ecological drivers of community assembly across taxonomic groups and trophic levels

    DEFF Research Database (Denmark)

    Özkan, Korhan

    was evident, the phytoplankton biomass decreased 10-fold indicating a released predation pressure on zooplankton. Trophic interactions between phyto- and zooplankton favoured the diversity of both groups. The second event was the invasion of zebra mussels (Dreissena polymorpha) to Lake Faarup in 1993....... The invasion also resulted in a decrease in the phytoplankton biomass; however, the effect was more gradual and the shift occurred with a four-year delay, reflecting the time needed for zebra mussels to establish in the system. The invasion resulted in a decrease in the diversity of both phyto- and zooplankton......, probably reflecting selective plankton feeding by the zebra mussels. Overall, the analyses in this thesis reflect the complex nature of community assembly. The assembly of forest birds and plankton communities was strongly driven by environmental conditions. However, the local communities were also linked...

  11. A multifaceted trophic cascade in a detritus-based system: density-, trait-, or processing-chain-mediated effects?

    Science.gov (United States)

    Albeny-Simões, Daniel; Murrell, Ebony G; Vilela, Evaldo F; Juliano, Steven A

    2015-03-01

    We investigated three pathways by which predators on an intermediate trophic level may produce a trophic cascade in detritus-based systems. Predators may increase lower trophic levels (bacteria) by reducing density of bacteriovores, by altering behavior of bacteriovores, and by processing living bacteriovores into carcasses, feces, and dissolved nutrients that are substrates for bacteria. We tested these pathways in laboratory experiments with mosquitoes in water-filled containers. Larval Toxorhynchites rutilus prey on larval Aedes triseriatus , which feed on bacteria. Using containers stocked with oak leaf infusion as a bacterial substrate, we compared bacterial productivity at 7 and 14 days for: prey alone; prey with a predator; and prey with predation cues but no predator. Controls contained no larvae, either with predation cues or without cues. Predation cues in the control treatment increased bacterial abundance at 7 days, but this effect waned by 14 days. Aedes triseriatus larvae reduced bacterial abundance significantly at 14 days. Predator cues and real predation both eliminated the negative effect of A. triseriatus on bacterial abundance. Predation cues reduced survivorship of A. triseriatus larvae at 14 days, however this effect was smaller than the effect of real predation. We further tested effects of residues from predation as cues or as detritus in a second experiment in which A. triseriatus were killed at similar rates by: real predators ; mechanical damage without the predator and carcasses left as detritus; or mechanical damage and carcasses removed. No prey larvae were killed in controls. Bacterial productivity was greater with real predation than in all other treatments and greater when prey larvae were killed or killed and removed, than in controls. Thus we find evidence that all three pathways contribute to the trophic cascade from T. rutilus to bacteria in tree hole systems.

  12. Cascading predator control interacts with productivity to determine the trophic level of biomass accumulation in a benthic food web

    NARCIS (Netherlands)

    Eriksson, Britas Klemens; Rubach, Anja; Batsleer, Jurgen; Hillebrand, Helmut

    Large-scale exploitation of higher trophic levels by humans, together with global-scale nutrient enrichment, highlights the need to explore interactions between predator loss and resource availability. The hypothesis of exploitation ecosystems suggests that top-down and bottom-up control alternate

  13. 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)

  14. 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

  15. Bioaccumulation of trace elements in trophic levels of wetland plants and waterfowl birds.

    Science.gov (United States)

    Alhashemi, Azam Sadat Hosseini; Karbassi, Abdolreza R; Kiabi, Bahram Hassanzadeh; Monavari, Seyed Masoud; Nabavi, Seyed Mohammad Bagher; Sekhavatjou, Mohammad Sadegh

    2011-09-01

    Present study investigates relationships between total and bioaccessibility of trace elements (Cd, Co, Cr, Cu, Mn, NI, Pb, V, and Zn) concentrations in sediment and their bioaccumulation in species in Shadegan wetland in southwest of Iran. Bioavailability factor (BAF) and translocation factor (TF) were calculated in plants and trophic transfer factor (TTF) was determined in bird species. For this purpose, sampling of sediments, aquatic plants including Phragmites australis, Typha australis, Scripus maritimus and two bird species encircling Porphyrio porphyrio and globally threatened Marmaronetta angustirostris were carried out during winter 2009. Result of chemical analysis show that bioaccessibility concentrations of Mn (8.31 mg/kg), V (1.33 mg/kg), and Pb (1.03 mg/kg) are higher than other metals. The uptake trend of trace elements in plant decreases as root > stem > leaf. Accumulation levels of trace elements in different tissues of P. porphyrio and M. angustirostris are almost identical and considerable. Accumulation and toxicity of Cd in birds is more than plants. In addition, BAF of V, Pb, and Cr indicates high accumulation by plants and great pollution rate in the area of study. In S. maritimus TF for Mn, Cu, Pb, and V are high whereas in T. australis, Cu and Pb posses the highest TF. Also Cr, Co, Mn, Ni, and Zn have higher TF from stem to leaf than root to stem in P. australis. Finally, TTFs were compared in various bird species.

  16. Higher trophic level affects nutrient, silicon, metal(loid), and radionuclide mobilization from freshwater sediments

    Science.gov (United States)

    Schaller, Jörg; Planer-Friedrich, Britta

    2017-04-01

    Organic sediments in aquatic ecosystems are well known sinks for nutrients, silicon, and metal(loid)s. Organic matter-decomposing organisms like invertebrate shredders, grazers, bioturbators, and filter feeder are key-species for the carbon and energy turnover within the decomposer community. We could show that invertebrate shredders and grazer affect element fixation or remobilization by changing binding properties of organic sediments and the attached biofilm. Bioturbators affect element fixation or remobilization by changing redox conditions within the uppermost sediment layer. Last but not least filter feeders, like the zebra mussel Dreissena polymorpha, an invasive organism in North American and European freshwater ecosystems significantly contributed to element mobilization of silicon, iron, phosphorus, arsenic, and copper and to immobilization of uranium (phomeostasis. Except of the filter feeder D. polymorpha, the invertebrates are able to minimize the accumulation of non-nutrient elements due to specific strategies, which is an important strategy for species living in systems tending to element accumulation. However, D. polymorpha revealed a significant uptake and accumulation of arsenic, copper, iron, and especially uranium both into the soft body tissues and the seashell. This accumulation by D. polymorpha is in line with previous observations of metal(loid) accumulation from biomonitoring studies. In summary, higher trophic level strongly contributes to element fixation or remobilization in aquatic systems.

  17. Coupling of an individual-based model of anchovy with lower trophic level and hydrodynamic models

    Science.gov (United States)

    Wang, Yuheng; Wei, Hao; Kishi, Michio J.

    2013-03-01

    Anchovy ( Engraulis japonicus), a small pelagic fish and food of other economic fishes, is a key species in the Yellow Sea ecosystem. Understanding the mechanisms of its recruitment and biomass variation is important for the prediction and management of fishery resources. Coupled with a hydrodynamic model (POM) and a lower trophic level ecosystem model (NEMURO), an individual-based model of anchovy is developed to study the influence of physical environment on anchovy's biomass variation. Seasonal variations of circulation, water temperature and mix-layer depth from POM are used as external forcing for NEMURO and the anchovy model. Biomasses of large zooplankton and predatory zooplankton which anchovy feeds on are output from NEMURO and are controlled by the consumption of anchovy on them. Survival fitness theory related to temperature and food is used to determine the swimming action of anchovy in the model. The simulation results agree well with observations and elucidate the influence of temperature in over-wintering migration and food in feeding migration.

  18. Four-trophic level food webs reveal the cascading impacts of an invasive plant targeted for biocontrol.

    Science.gov (United States)

    López-Núñez, Francisco A; Heleno, Ruben H; Ribeiro, Sérgio; Marchante, Hélia; Marchante, Elizabete

    2017-03-01

    Biological invasions are a major threat to biodiversity and as such understanding their impacts is a research priority. Ecological networks provide a valuable tool to explore such impacts at the community level, and can be particularly insightful for planning and monitoring biocontrol programmes, including the potential for their seldom evaluated indirect non-target effects. Acacia longifolia is among the worst invasive species in Portugal, and has been recently targeted for biocontrol by a highly specific gall-wasp. Here we use an ambitious replicated network approach to: (1) identify the mechanisms by which direct and indirect impacts of A. longifolia can cascade from plants to higher trophic levels, including gallers, their parasitoids and inquilines; (2) reveal the structure of the interaction networks between plants, gallers, parasitoids and inquilines before the biocontrol; and (3) explore the potential for indirect interactions among gallers, including those established with the biocontrol agent, via apparent competition. Over a 15-month period, we collected 31,737 galls from native plants and identified all emerging insects, quantifying the interactions between 219 plant-, 49 galler-, 65 parasitoid- and 87 inquiline-species-one of the largest ecological networks to date. No galls were found on any of the 16 alien plant species. Invasion by A. longifolia caused an alarming simplification of plant communities, with cascading effects to higher trophic levels, namely: a decline of overall gall biomass, and on the richness, abundance and biomass of galler insects, their parasitoids, and inquilines. Correspondingly, we detected a significant decline in the richness of interactions between plants and galls. The invasion tended to increase overall interaction evenness by promoting the local extinction of the native plants that sustained more gall species. However, highly idiosyncratic responses hindered the detection of further consistent changes in network

  19. 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

  20. Modeling Microbial Dynamics in Aquifers Considering the Interaction Between the Higher Trophic Levels

    Science.gov (United States)

    Bajracharya, B. M.; Cirpka, O. A.; Lu, C.

    2014-12-01

    Models of microbial dynamics coupled to solute transport in aquifers typically require the introduction of a bacterial carrying capacity term to prevent excessive microbial growth close to substrate-injection boundaries. The factors controlling this carrying capacity, however, are not fully understood. Most explanations for the occurrence of a carrying capacity discussed are based on the assumption of a bottom-up control of groundwater ecosystems. An alternative explanation is based on top-down control. Our model considers substrate, bacteria and higher trophic levels, such as grazers or bacteriophages. The dissolved substrate is transported with water flow whereas the biomasses of bacteria and grazers are considered essentially immobile. The one-dimensional reactive transport model also accounts for substrate dispersion and a random walk of grazers influenced by the bacteria concentration. The grazers grow on the bacteria, leading to a negative feedback on the bacteria concentration which may limit the turnover of the substrate. A single retentostat model with Monod kinetics of bacterial growth and a second-order grazing shows that the system oscillates but approaches a stable steady state with non-zero concentrations of substrate, bacteria, and grazers. The steady-state concentration of the bacteria biomass is independent of the substrate concentration in the inflow. When coupling several retentostats in a series to mimic a groundwater column, the steady-state bacteria concentrations remain at a constant level over a significant travel distance. The results show that grazing is a possible explanation of the carrying capacity, provided that there is enough substrate to sustain bacteria and grazers.

  1. 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.

  2. 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

  3. Ecotoxicological evaluation of harbour sediments using marine organisms from different trophic levels

    Energy Technology Data Exchange (ETDEWEB)

    Pane, L.; Giacco, E.; Mariottini, G.L. [Genova Univ. (Italy). Dept. of Biology; Corra, C.; Greco, G.; Faimali, M. [CNR - ISMAR-Marine Technology Section, Genova (Italy); Varisco, F. [Multiproject S.r.l., Gorizia (Italy)

    2008-04-15

    Background, aim and scope. The toxicity of contaminated sediments should be evaluated considering the direct exposure of laboratory organisms to whole sediments and the indirect exposure to elutriates or extracts (Tay et al. 1992, Byrne and Halloran 1999, Nendza 2002). The alga Dunaliella tertiolecta is indicated for the use in toxicity bioassays because it is highly sensitive to several xenobiotics. Harpacticoid copepods have been already used for toxicity testing and Tigriopus fulvus is a promising Mediterranean target-species in ecotoxicology (Todaro et al. 2001, Faraponova et al. 2003, Pane et al. 2005a). In this study, the toxicity of sediments collected in harbour sites of the Northeastern Adriatic Sea was evaluated by growth inhibition test with free living and alginate-immobilized Dunaliella tertiolecta and acute toxicity test with nauplii and adult Tigriopus fulvus with the aim of pointing out the importance to utilize model organisms from different trophic levels in sediment ecotoxicology. Methodology. Elutriates and whole sediments were tested on free living and immobilized (Pane et al. 1998) algal cells, and on laboratory reared copepods. Free-living D. tertiolecta were exposed to diluted elutriates in a static, multi-well plate system. Na-alginate immobilized D. tertiolecta were placed in polystyrene inserts fitted with polyester mesh bottoms and exposed to a thin layer (2 mm) of whole sediments in multi-well plates (EPS 1992, Pane and Bertino 1999). Toxicity tests with copepods were carried out on Tigriopus fulvus nauplii (elutriates) and adults (whole sediments and elutriates). Same-aged nauplii useful for toxicity tests were obtained by egg sac detaching and consequent hatching stimulation (Pane et al. 2006). Newborn nauplii (I-II stage) were exposed to elutriates in multi-well plates provided with polystyrene inserts. Adult T. fulvus maintained in polystyrene inserts fitted with polyester mesh bottoms were placed in contact with a thin layer (2 mm

  4. 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

  5. Positive correlation of trophic level and proportion of sexual taxa of oribatid mites (Acari: Oribatida) in alpine soil systems.

    Science.gov (United States)

    Fischer, Barbara M; Meyer, Erwin; Maraun, Mark

    2014-08-01

    We investigated community structure, trophic ecology (using stable isotope ratios; (15)N/(14)N, (13)C/(12)C) and reproductive mode of oribatid mites (Acari, Oribatida) along an altitudinal gradient (2,050-2,900 m) in the Central Alps (Obergurgl, Austria). We hypothesized that (1) the community structure changes with altitude, (2) oribatid mites span over four trophic levels, (3) the proportion of sexual taxa increases with altitude, and (4) the proportion of sexual taxa increases with trophic level, i.e. is positively correlated with the δ(15)N signatures. Oribatid mite community structure changed with altitude indicating that oribatid mites occupy different niches at different altitudes. Oribatid mites spanned over 12 δ(15)N units, i.e. about four trophic levels, which is similar to lowland forest ecosystems. The proportion of sexually reproducing taxa increased from 2,050 to 2,900 m suggesting that limited resource availability at high altitudes favors sexual reproduction. Sexual taxa more frequently occurred higher in the food web indicating that the reproductive mode is related to nutrition of oribatid mites. Generally, oribatid mite community structure changed from being decomposer dominated at lower altitude to being dominated by fungal and lichen feeders, and predators at higher altitude. This supports the view that resources from dead organic material become less available with increasing altitude forcing species to feed on living resources such as fungi, lichens and nematodes. Our findings support the hypothesis that limited resource accessibility (at high altitudes) favors sexually reproducing species whereas ample resource supply (at lower altitudes) favors parthenogenetic species.

  6. The effect of cannibalism intensity on the net primary production and the dynamics of trophic links in the aquatic ecosystem

    Science.gov (United States)

    Sirobokova, I.; Pechurkin, N.

    The aim of the work was to construct a mathematical model of the effect of cannibalism intensity on the dynamic behavior and functional characteristics of simple aquatic ecosystems. A mathematical model of an aquatic ecosystem has been constructed, with the following principal trophic links: limiting nutrient concentration, producers (phytoplankton), predators of the first order, and predators of the second order. The model takes into account the age structure of the second-order predator and includes two age groups (the young and adults). The adult predators of the second order are cannibals feeding on both first-order predators and their own young, which consume phytoplankton. The model was used to investigate the effect of cannibalism intensity on the net primary production and the dynamics of trophic links in the aquatic ecosystem characterized by cannibalism at the upper trophic level or by the emergence of a third-order predator in the system. It has been found that when cannibalism increases above a certain level, the concentrations of both adults and the young of the 2nd-order predators decrease. At the same time, the concentrations of the 1st-order predators and of nutrients increase, while the biomass of producers decreases. When the cannibalism intensity is low, the net primary production of the system increases to a certain level with the increase in cannibalism intensity and drops sharply when the level of consumption of the young is high. The emergence of the 3rd-order predator in the system leads to a change in the dynamics of links in conformity with the "bottom-up" and "top-down" control. Thus, cannibalism of a certain magnitude can lead to an increase in integrated parameters of aquatic ecosystems: the amount of energy used by the ecosystem and the productivity in the photosynthesis link.

  7. 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.

  8. Trophic state in Voyageurs National Park lakes before and after implementation of a revised water-level management plan

    Science.gov (United States)

    Christensen, Victoria G.; Maki, Ryan P.

    2015-01-01

    We compiled Secchi depth, total phosphorus, and chlorophyll a (Chla) data from Voyageurs National Park lakes and compared datasets before and after a new water-level management plan was implemented in January 2000. Average Secchi depth transparency improved (from 1.9 to 2.1 m, p = 0.020) between 1977-1999 and 2000-2011 in Kabetogama Lake for August samples only and remained unchanged in Rainy, Namakan, and Sand Point Lakes, and Black Bay in Rainy Lake. Average open-water season Chla concentration decreased in Black Bay (from an average of 13 to 6.0 μg/l, p = 0.001) and Kabetogama Lake (from 9.9 to 6.2 μg/l, p = 0.006) between 1977-1999 and 2000-2011. Trophic state index decreased significantly in Black Bay from 59 to 51 (p = 0.006) and in Kabetogama Lake from 57 to 50 (p = 0.006) between 1977-1999 and 2000-2011. Trophic state indices based on Chla indicated that after 2000, Sand Point, Namakan, and Rainy Lakes remained oligotrophic, whereas eutrophication has decreased in Kabetogama Lake and Black Bay. Although nutrient inputs from inflows and internal sources are still sufficient to produce annual cyanobacterial blooms and may inhibit designated water uses, trophic state has decreased for Kabetogama Lake and Black Bay and there has been no decline in lake ecosystem health since the implementation of the revised water-level management plan.

  9. Changes in the trophic structure, abundance and species diversity of ...

    African Journals Online (AJOL)

    Decreases in mean trophic level, the biomass of high trophic level species and indices of species diversity between 1990 and 2009 were observed in commercial catches. These decreases were then related to changes in fishing pressure, fishing strategy and the combined effects of fishing and environmental factors (as ...

  10. 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.

  11. Contributions of C3and C4plants to higher trophic levels in an Amazonian savanna.

    Science.gov (United States)

    Magnusson, William E; Carmozina de Araújo, M; Cintra, Renato; Lima, Albertina P; Martinelli, Luiz A; Sanaiotti, Tânia M; Vasconcelos, Heraldo L; Victoria, Reynaldo L

    1999-04-01

    We studied the energy flow from C 3 and C 4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of different consumer groups. All C 4 plants encountered in our study area were grasses and all C 3 plants were bushes, shrubs or vines. Differences in δ 13 C ratios among bushes (x¯ = -30.8, SD = 1.2), vines (x¯ = -30.7, SD = 0.46) and trees (x¯ = -29.7, SD = 1.5) were small. However the mean δ 13 C ratio of dicotyledonous plants (x¯ = -30.4, SD = 1.3) was much more negative than that of the most common grasses (x¯ = -13.4, SD = 0.27). The insect primary consumers had δ 13 C ratios which ranged from a mean of -29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of -14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for δ 13 C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of δ 13 C (x¯ = -21.7, SD = 1.6; x¯ = -21.9, SD = 1.8, respectively) than the birds (x¯ = -24.8, SD = 1.8) and the only species of mammal resident in the savanna (x¯ = -25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C 4 grasses.

  12. Delineating the boundary and structure of higher trophic level assemblages in the western North Pacific Ocean

    Science.gov (United States)

    Okuda, Takehiro; Kiyota, Masashi; Yonezaki, Shiroh; Murakami, Chisato; Kato, Yoshiki; Sakai, Mitsuo; Wakabayashi, Toshie; Okazaki, Makoto

    2017-06-01

    Understanding the community structure of oceanic higher trophic level (HTL) organisms (e.g., sharks, tunas, salmons, and squids) is fundamental to management of marine resources in a way that ensures their sustainable use and maintains marine ecosystem functionality and biodiversity. We analyzed the spatial structure of HTL assemblages in the western North Pacific Ocean using driftnet survey data collected at latitudes of 35-46 °N along transect lines at 144 °E, 155 °E, and 175.5 °E longitude in July and August 2011. We proposed a new dissimilarity metric segmentation procedure (Dissimilarity Segmentation) based on the differences of mean Bray-Curtis dissimilarity indices between two individual driftnet hauls within the same subarea or among different subareas. Dissimilarity Segmentation allowed us to divide the western North Pacific Ocean into three subareas: a northern subarea (>41 °N including 41 °N on the 175.5 °E transect), a transition subarea (37-41 °N), and a southern subarea (<37 °N). The HTL biomass in the northern subarea was high, and the species diversity was low; dominant and common species accounted for most of the biomass. The HTL assemblage in the southern subarea was composed of many species that were uncommon or rare; the biomass was lower, and the species diversity was higher than in the northern subarea. In the transition subarea, neon flying squid accounted for most of the biomass, and although the biomass was intermediate, species diversity was highest among the three subareas. Canonical correspondence analysis with oceanic environmental variables, principally chlorophyll a, sea surface salinity, and sea surface height, as the explanatory variables accounted for 43.6% of the variance of the HTL pelagic species composition. This result suggests that the HTL pelagic community in the western North Pacific is influenced largely by productivity and oceanic physical structure. These results suggest that an analytical approach based on

  13. 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.

  14. 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.

  15. Bald eagles and sea otters in the Aleutian Archipelago: indirect effects of trophic cascades.

    Science.gov (United States)

    Anthony, Robert G; Estes, James A; Ricca, Mark A; Miles, A Keith; Forsman, Eric D

    2008-10-01

    Because sea otters (Enhydra lutris) exert a wide array of direct and indirect effects on coastal marine ecosystems throughout their geographic range, we investigated the potential influence of sea otters on the ecology of Bald Eagles (Haliaeetus leucocephalus) in the Aleutian Islands, Alaska, USA. We studied the diets, productivity, and density of breeding Bald Eagles on four islands during 1993-1994 and 2000-2002, when sea otters were abundant and scarce, respectively. Bald Eagles depend on nearshore marine communities for most of their prey in this ecosystem, so we predicted that the recent decline in otter populations would have an indirect negative effect on diets and demography of Bald Eagles. Contrary to our predictions, we found no effects on density of breeding pairs on four islands from 1993-1994 to 2000-2002. In contrast, diets and diet diversity of Bald Eagles changed considerably between the two time periods, likely reflecting a change in prey availability resulting from the increase and subsequent decline in sea otter populations. The frequency of sea otter pups, rock greenling (Hexagammus lagocephalus), and smooth lumpsuckers (Aptocyclus ventricosus) in the eagle's diet declined with corresponding increases in Rock Ptarmigan (Lagopus mutus), Glaucous-winged Gulls (Larus glaucescens), Atka mackerel (Pleurogrammus monopterygius), and various species of seabirds during the period of the recent otter population decline. Breeding success and productivity of Bald Eagles also increased during this time period, which may be due to the higher nutritional quality of avian prey consumed in later years. Our results provide further evidence of the wide-ranging indirect effects of sea otter predation on nearshore marine communities and another apex predator, the Bald Eagle. Although the indirect effects of sea otters are widely known, this example is unique because the food-web pathway transcended five species and several trophic levels in linking one apex predator

  16. Bald eagles and sea otters in the Aleutian Archipelago: indirect effects of trophic cascades.

    Science.gov (United States)

    Anthony, R.G.; Estes, J.A.; Ricca, M.A.; Miles, A.K.; Forsman, E.D.

    2008-01-01

    Because sea otters (Enhydra lutris) exert a wide array of direct and indirect effects on coastal marine ecosystems throughout their geographic range, we investigated the potential influence of sea otters on the ecology of Bald Eagles (Haliaeetus leucocephalus) in the Aleutian Islands, Alaska, USA. We studied the diets, productivity, and density of breeding Bald Eagles on four islands during 1993–1994 and 2000–2002, when sea otters were abundant and scarce, respectively. Bald Eagles depend on nearshore marine communities for most of their prey in this ecosystem, so we predicted that the recent decline in otter populations would have an indirect negative effect on diets and demography of Bald Eagles. Contrary to our predictions, we found no effects on density of breeding pairs on four islands from 1993–1994 to 2000–2002. In contrast, diets and diet diversity of Bald Eagles changed considerably between the two time periods, likely reflecting a change in prey availability resulting from the increase and subsequent decline in sea otter populations. The frequency of sea otter pups, rock greenling (Hexagammus lagocephalus), and smooth lumpsuckers (Aptocyclus ventricosus) in the eagle's diet declined with corresponding increases in Rock Ptarmigan (Lagopus mutus), Glaucous-winged Gulls (Larus glaucescens), Atka mackerel (Pleurogrammus monopterygius), and various species of seabirds during the period of the recent otter population decline. Breeding success and productivity of Bald Eagles also increased during this time period, which may be due to the higher nutritional quality of avian prey consumed in later years. Our results provide further evidence of the wide-ranging indirect effects of sea otter predation on nearshore marine communities and another apex predator, the Bald Eagle. Although the indirect effects of sea otters are widely known, this example is unique because the food-web pathway transcended five species and several trophic levels in linking one apex

  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, 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.

  18. 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.

  19. Silver bioaccumulation in chironomid larvae as a potential source for upper trophic levels: a study case from northern Patagonia.

    Science.gov (United States)

    Williams, Natalia; Rizzo, Andrea; Arribére, María A; Suárez, Diego Añón; Guevara, Sergio Ribeiro

    2018-01-01

    Silver (Ag) is a pollutant of high concern in aquatic ecosystems, considered among the most toxic metallic ions. In lacustrine environments, contaminated sediments are a source of Ag for the food web. Chironomidae (Insecta: Diptera) are the most abundant, diverse, and representative insect groups in aquatic ecosystems. Chironomid larvae are closely associated to benthic substrates and link primary producers and secondary consumers. Given their trophic position and their life habits, these larvae can be considered the entry point for the transference of Ag, from the benthic deposit to the higher trophic levels of the food web. Previous studies in lakes from Nahuel Huapi National Park (Northern Patagonia) showed Ag enrichment over background levels (0.04-0.1 μg g -1 dry weight) both in biota (bivalves and fish liver) and sediments from sites near human settlements. The aim of this study was to analyze the role of chironomids in the transference of Ag from the benthic reservoir of Lake Moreno Oeste to the food web. The concentration of Ag in chironomid larvae tissue ranged from 0.1 to 1.5 μg g -1 dry weight, reaching a bioaccumulation factor up to 17 over substrates and depending on the associated substrate type, feeding habitats, larval stage, and season. The main Ag transfer to higher trophic levels by chironomids occurs in the littoral zone, mostly from larvae inhabiting submerged vegetation (Myriophyllum quitense) and sediment from vegetated zones. This study presents novel evidence of the doorway role played by chironomid larvae in Ag pathways from the sediments into food webs of freshwater ecosystems.

  20. Evaluation of marine subareas of Europe using life history parameters and trophic levels of selected fish populations.

    Science.gov (United States)

    Jayasinghe, R P Prabath K; Amarasinghe, Upali S; Newton, Alice

    2015-12-01

    European marine waters include four regional seas that provide valuable ecosystem services to humans, including fish and other seafood. However, these marine environments are threatened by pressures from multiple anthropogenic activities and climate change. The European Marine Strategy Framework Directive (MSFD) was adopted in 2008 to achieve good environmental status (GEnS) in European Seas by year 2020, using an Ecosystem Approach. GEnS is to be assessed using 11 descriptors and up to 56 indicators. In the present analysis two descriptors namely "commercially exploited fish and shellfish populations" and "food webs" were used to evaluate the status of subareas of FAO 27 area. Data on life history parameters, trophic levels and fisheries related data of cod, haddock, saithe, herring, plaice, whiting, hake and sprat were obtained from the FishBase online database and advisory reports of International Council for the Exploration of the Sea (ICES). Subareas inhabited by r and K strategists were identified using interrelationships of life history parameters of commercially important fish stocks. Mean trophic level (MTL) of fish community each subarea was calculated and subareas with species of high and low trophic level were identified. The Fish in Balance (FiB) index was computed for each subarea and recent trends of FiB indices were analysed. The overall environmental status of each subarea was evaluated considering life history trends, MTL and FiB Index. The analysis showed that subareas I, II, V, VIII and IX were assessed as "good" whereas subareas III, IV, VI and VII were assessed as "poor". The subareas assessed as "good" were subject to lower environmental pressures, (less fishing pressure, less eutrophication and more water circulation), while the areas with "poor" environment experienced excessive fishing pressure, eutrophication and disturbed seabed. The evaluation was based on two qualitative descriptors ("commercially exploited fish and shellfish

  1. 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

  2. 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.

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

    Science.gov (United States)

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

    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 197,000n g/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. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

  4. The influence of trophic level and feeding location of the levels of organochlorine contaminants in seabird eggs as revealed by stable carbon and nitrogen isotope analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hobson, K. [Canadian Wildlife Service, Saskatoon, Saskatchewan (Canada); Jarman, W.M.; Bott, J.A.; Bacon, C.E. [Univ. of California, Santa Cruz (Canada). Inst. of Marine Sciences; Sydeman, W. [Point Reyes Bird Observatory, Stinson Beach, CA (United States)

    1994-12-31

    Seabird eggs have been used extensively to assay contaminants in marine food webs, but links to trophic level or feeding location have remained poorly understood due to limitations inherent in conventional dietary studies. Stable-isotope analysis of bird eggs may be used to infer trophic position and feeding location of adult seabirds and can be readily correlated with measurements of egg contaminant levels. The authors measured stable-carbon ({delta}{sup 13}C) and nitrogen ({delta}{sup 15}N) isotope abundance, and organochlorine contaminants (DDTs, PCBs, chlordanes, etc.) in eggs from Cassin`s Auklet (Ptychoramphus aleutica), Common Murre (Uria aalge), Pigeon Guillemot (Cepphus columba). Rhinoceros Auklet (Cerorhinca monocerata), Pelagic Cormorant (Phalacrocorax pelagicus), Brandt`s Cormorant (Phalacrocorax penicillatus), and Western Gull (Larus) from Southeast Farallon Island together with rockfish (Sebastes spp.), anchovy (Engraulis spp.), and euphausiid prey from the Gulf of the Farallones. Consistent with its planktivorous diet and pelagic feeding habits, Cassin`s Auklet showed the lowest mean {delta}{sup 15}N value and the least enriched {delta}{sup 13}C values. Measures of trophic level and foraging location were constructed for all other seabirds relative to these isotopic endpoints. Contaminant levels in the eggs and fish will be interpreted in light of the stable-isotope results.

  5. Detection of effects of a high trophic level predator, Sorex unguiculatus (Soricidae, Mammalia), on a soil microbial community in a cool temperate forest in Hokkaido, using the ARISA method.

    Science.gov (United States)

    Yamamoto, Kana; Ohdachi, Satoshi D; Kasahara, Yasuhiro

    2010-01-01

    Soil bacteria play important roles as litter decomposers in most terrestrial ecosystems and microbial activity is affected by activities of soil invertebrates. In soil ecosystems of forests in Hokkaido, the long-clawed shrew is an important predator whose preying on soil invertebrates may indirectly affect soil bacterial communities. To estimate indirect top-down effects of shrews on the soil bacterial community, field experiments were conducted using enclosures in which shrews were introduced and removed, and changes in bacterial community composition, species richness, diversity, and evenness were observed using automated ribosomal intergenic spacer analysis (ARISA). Abiotic environmental conditions (ambient temperature, soil temperature, soil moisture content and soil pH) were also considered. Bacterial community structure was significantly affected by soil moisture content and soil temperature. The significant causes of the change in bacterial species richness, diversity, and evenness varied among experimental treatments; however, soil moisture tended to have significantly negative effects on these indices in all cases. In the present study, effects of shrews on the bacterial community were not detected.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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

  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. 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

  16. Internal distribution of Cd in lettuce and resulting effects on Cd trophic transfer to the snail: Achatina fulica.

    Science.gov (United States)

    Li, Cheng-Cheng; Dang, Fei; Cang, Long; Zhou, Dong-Mei; Peijnenburg, Willie J G M

    2015-09-01

    The mechanisms underlying Cd trophic transfer along the soil-lettuce-snail food chain were investigated. The fate of Cd within cells, revealed by assessment of Cd chemical forms and of subcellular partitioning, differed between the two examined lettuce species that we examined (L. longifolia and L. crispa). The species-specific internal Cd fate not only influenced Cd burdens in lettuce, with higher Cd levels in L. crispa, but also affected Cd transfer efficiency to the consumer snail (Achatina fulica). Especially, the incorporation of Cd chemical forms (Cd in the inorganic, water-soluble and pectates and protein-integrated forms) in lettuce could best explain Cd trophic transfer, when compared to dietary Cd levels alone and/or subcellular Cd partitioning. Trophically available metal on the subcellular partitioning base failed to shed light on Cd transfer in this study. After 28-d of exposure, most Cd was trapped in the viscera of Achatina fulica, and cadmium bio-magnification was noted in the snails, as the transfer factor of lettuce-to-snail soft tissue was larger than one. This study provides a first step to apply a chemical speciation approach to dictate the trophic bioavailability of Cd through the soil-plant-snail system, which might be an important pre-requisite for mechanistic understanding of metal trophic transfer. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. 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

  18. 'Trophic' and 'source' amino acids in trophic estimation: a likely metabolic explanation.

    Science.gov (United States)

    O'Connell, T C

    2017-06-01

    Amino acid nitrogen isotopic analysis is a relatively new method for estimating trophic position. It uses the isotopic difference between an individual's 'trophic' and 'source' amino acids to determine its trophic position. So far, there is no accepted explanation for the mechanism by which the isotopic signals in 'trophic' and 'source' amino acids arise. Yet without a metabolic understanding, the utility of nitrogen isotopic analyses as a method for probing trophic relations, at either bulk tissue or amino acid level, is limited. I draw on isotopic tracer studies of protein metabolism, together with a consideration of amino acid metabolic pathways, to suggest that the 'trophic'/'source' groupings have a fundamental metabolic origin, to do with the cycling of amino-nitrogen between amino acids. 'Trophic' amino acids are those whose amino-nitrogens are interchangeable, part of a metabolic amino-nitrogen pool, and 'source' amino acids are those whose amino-nitrogens are not interchangeable with the metabolic pool. Nitrogen isotopic values of 'trophic' amino acids will reflect an averaged isotopic signal of all such dietary amino acids, offset by the integrated effect of isotopic fractionation from nitrogen cycling, and modulated by metabolic and physiological effects. Isotopic values of 'source' amino acids will be more closely linked to those of equivalent dietary amino acids, but also modulated by metabolism and physiology. The complexity of nitrogen cycling suggests that a single identifiable value for 'trophic discrimination factors' is unlikely to exist. Greater consideration of physiology and metabolism should help in better understanding observed patterns in nitrogen isotopic values.

  19. Mean trophic level of coastal fisheries landings in the Persian Gulf (Hormuzgan Province), 2002-2011

    Science.gov (United States)

    Razzaghi, Marzieh; Mashjoor, Sakineh; Kamrani, Ehsan

    2017-05-01

    Fishing activities can alter the structure of marine food webs by the selective removal of some species. The changes in the marine food webs of the Hormuzgan waters of the Persian Gulf, Iran were assessed, based on estimates of the mean trophic index (MTI) and Fishing in Balance index (FiB), and on landing profile of the exploited marine community (49 species) during the period, 2002-2011. The total landings ( Y t) ( R=0.88, Pindicates exploitation of marine resources. The FiB index also showed a downward trend and negative values from 2002 to 2009, which may be associated with unbalanced structure in the fisheries, but an upward trend from 2009 to 2011. The time variation of the landing profile showed two periods with significant diff erences in their species composition ( R=0.88; P =0.005), and based on analysis of similarity, species have been identified as discriminator species, namely Thunnus albacores and Benthosema pterotum. Results indicate that changes in MTI reflected changes in the Hormuzgan landing structure. The examination of the MTI, FBI, and landing profile (LP) temporal pattern suggests that the status of fishery resources in Hormuzgan inshore waters is overexploited, and provides evidence of the probability that a fishing down process is occurring in this area, and that this trend may continue in the long-term. Therefore, environmental fisheries management and conservation programs should be prioritized for these valuable resources.

  20. Lower trophic levels and detrital biomass control the Bay of Biscay continental shelf food web: Implications for ecosystem management

    Science.gov (United States)

    Lassalle, G.; Lobry, J.; Le Loc'h, F.; Bustamante, P.; Certain, G.; Delmas, D.; Dupuy, C.; Hily, C.; Labry, C.; Le Pape, O.; Marquis, E.; Petitgas, P.; Pusineri, C.; Ridoux, V.; Spitz, J.; Niquil, N.

    2011-12-01

    The Bay of Biscay (North-East Atlantic) has long been subjected to intense direct and indirect human activities that lead to the excessive degradation and sometimes overexploitation of natural resources. Fisheries management is gradually moving away from single-species assessments to more holistic, multi-species approaches that better respond to the reality of ecosystem processes. Quantitative modelling methods such as Ecopath with Ecosim can be useful tools for planning, implementing and evaluating ecosystem-based fisheries management strategies. The aim of this study was therefore to model the energy fluxes within the food web of this highly pressured ecosystem and to extract practical information required in the diagnosis of ecosystem state/health. A well-described model comprising 30 living and two non-living compartments was successfully constructed with data of local origin, for the Bay of Biscay continental shelf. The same level of aggregation was applied to primary producers, mid-trophic-levels and top-predators boxes. The model was even more general as it encompassed the entire continuum of marine habitats, from benthic to pelagic domains. Output values for most ecosystem attributes indicated a relatively mature and stable ecosystem, with a large proportion of its energy flow originating from detritus. Ecological network analysis also provided evidence that bottom-up processes play a significant role in the population dynamics of upper-trophic-levels and in the global structuring of this marine ecosystem. Finally, a novel metric based on ecosystem production depicted an ecosystem not far from being overexploited. This finding being not entirely consistent over indicators, further analyses based on dynamic simulations are required.

  1. 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.

  2. 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.

  3. 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

  4. 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. δ(13)C, δ(15)N). 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(13)C-δ(15)N 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.

  5. 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.

  6. 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

  7. Soil microarthropods and their relationship to higher trophic levels in the Pedregal de San Angel Ecological Reserve, Mexico.

    Science.gov (United States)

    Callejas-Chavero, Alicia; Castaño-Meneses, Gabriela; Razo-González, María; Pérez-Velázquez, Daniela; Palacios-Vargas, José G; Flores-Martínez, Arturo

    2015-01-01

    Soil fauna is essential for ecosystem dynamics as it is involved in biogeochemical processes, promotes nutrient availability, and affects the animal communities associated with plants. In this study, we examine the possible relationship between the soil microarthropod community on foliage production and quality of the shrub Pittocaulon praecox. We also examine the arthropods associated to its foliage, particularly the size of the main herbivores and of their natural enemies, at two sites with contrasting vegetation cover and productivity. The diversity of soil microarthropods was assessed from soil samples collected monthly under P. praecox individuals over 13 mo. Specimens collected were identified to species or morphospecies. Shrub foliage productivity was evaluated through the amount of litter produced. Resource quality was assessed by the mean content (percentage by weight) of N, C, S, and P of 30 leaves from each shrub. The mean size of herbivores and their natural enemies were determined by measuring 20 adult specimens of each of the most abundant species. We found a higher species richness of soil microarthropods and foliar arthropods in the open site, although the diversity of foliage arthropods was lower in the closed site. Shrubs growing in the closed site tend to produce more, larger, and nutritionally poorer (lower nitrogen content) leaves than open site. Herbivores and their natural enemies were also larger in the closed site. We found a significant positive relationship between the diversity and species richness of foliar arthropods and the nitrogen content of leaves. In general, species richness and diversity of both the foliar and soil fauna, as well as the size of organisms belonging to higher trophic levels, were affected by vegetation cover and primary productivity at each site. These findings highlight the need to simultaneously consider at least four trophic levels (soil organisms, plants, herbivores, and natural enemies) to better understand

  8. 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.

  9. Methanogenic pathways in Alaskan peatlands at different trophic levels with evidence from stable isotope ratios and metagenomics

    Science.gov (United States)

    Zhang, L.; Liu, X.; Langford, L.; Chanton, J.; Roth, S.; Schaefer, J.; Barkay, T.; Hines, M. E.

    2017-12-01

    To better constrain the large uncertainties in emission fluxes, it is necessary to improve the understanding of methanogenic pathways in northern peatlands with heterogeneous surface vegetation and pH. Surface vegetation is an excellent indicator of porewater pH, which heavily influences the microbial communities in peatlands. Stable C isotope ratios (d13C) have been used as a robust tool to distinguish methanogenic pathways, especially in conjunction with metagenomic analysis of the microbial communities. To link surface vegetation species compositions, pH, microbial communities, and methanogenic pathways, 15 peatland sites were studied in Fairbanks and Anchorage, Alaska in the summer of 2014. These sites were ordinated using multiple factor analysis into 3 clusters based on pH, temp, CH4 and volatile fatty acid production rates, d13C values, and surface vegetation composition. In the ombrotrophic group (pH 3.3), various Sphagna species dominanted, but included shrubs Ledum decumbens and Eriophorum vaginatum. Primary fermentation rates were slow with no CH4 detected. The fen cluster (pH 5.3) was dominated by various Carex species, and CH4 production rates were lower than those in the intermediate cluster but more enriched in 13C (-49‰). Methanosaeta and Methanosarcina were the dominant methanogens. In the intermediate trophic level (pH 4.7), Sphagnum squarrosum and Carex aquatilis were abundant. The same methanogens as in fen cluster also dominated this group, but with higher abundances, which, in part, lead to the higher CH4 production rates in this cluster. The syntrophs Syntrophobacter and Pelobacter were also more abundant than the fen sites, which may explain the d13CH4 values that were the lighetest among the three clusters (-54‰). The high methanogenic potential in the intermediate trophic sites warrant further study since they are not only present in large areas currently, but also represent the transient stage during the evolution from bog to fen in

  10. Invasive plants have different effects on trophic structure of green and brown food webs in terrestrial ecosystems: a meta-analysis.

    Science.gov (United States)

    McCary, Matthew A; Mores, Robin; Farfan, Monica A; Wise, David H

    2016-03-01

    Although invasive plants are a major source of terrestrial ecosystem degradation worldwide, it remains unclear which trophic levels above the base of the food web are most vulnerable to plant invasions. We performed a meta-analysis of 38 independent studies from 32 papers to examine how invasive plants alter major groupings of primary and secondary consumers in three globally distributed ecosystems: wetlands, woodlands and grasslands. Within each ecosystem we examined if green (grazing) food webs are more sensitive to plant invasions compared to brown (detrital) food webs. Invasive plants have strong negative effects on primary consumers (detritivores, bacterivores, fungivores, and/or herbivores) in woodlands and wetlands, which become less abundant in both green and brown food webs in woodlands and green webs in wetlands. Plant invasions increased abundances of secondary consumers (predators and/or parasitoids) only in woodland brown food webs and green webs in wetlands. Effects of invasive plants on grazing and detrital food webs clearly differed between ecosystems. Overall, invasive plants had the most pronounced effects on the trophic structure of wetlands and woodlands, but caused no detectable changes to grassland trophic structure. © 2016 John Wiley & Sons Ltd/CNRS.

  11. Ocean acidification effect on prokaryotic metabolism tested in two diverse trophic regimes in the Mediterranean Sea

    Science.gov (United States)

    Celussi, Mauro; Malfatti, Francesca; Annalisa, Franzo; Gazeau, Frédéric; Giannakourou, Antonia; Pitta, Paraskevi; Tsiola, Anastasia; Del Negro, Paola

    2017-02-01

    Notwithstanding the increasing amount of researches on the effect of ocean acidification (OA) on marine ecosystems, no consent has emerged on its consequences on many prokaryote-mediated processes. Two mesocosm experiments were performed in coastal Mediterranean areas with different trophic status: the summer oligotrophic Bay of Calvi (BC, Corsica, France) and the winter mesotrophic Bay of Villefranche (BV, France). During these experiments, nine enclosures (∼54 m3) were deployed: 3 unamended controls and 6 elevated CO2, following a gradient up to 1250 μatm. We present results involving free-living viral and prokaryotic standing stocks, bacterial carbon production, abundance of highly active cells (CTC+), and degradation processes (beta-glucosidase, chitinase, leucine-aminopeptidase, lipase and alkaline phosphatase activities). The experiments revealed clear differences in the response of the two prokaryotic communities to CO2 manipulation. Only abundances of heterotrophic prokaryotes, viruses and lipase activity were not affected by CO2 manipulation at both locations. On the contrary, the percent of CTC+ was positively correlated to CO2 only in BC, concomitantly to a bulk reduction of [3H]-leucine uptake. The other tested parameters showed a different response at the two sites suggesting that the trophic regime of the systems plays a fundamental role on the effect of OA on prokaryotes through indirect modifications of the available substrate. Modified degradation rates may affect considerably the export of organic matter to the seafloor and thus ecosystem functioning within the water column. Our results highlight the need to further analyse the consequences of OA in oligotrophic ecosystems with particular focus on dissolved organic matter.

  12. Effects of river otter activity on terrestrial plants in trophically altered Yellowstone Lake.

    Science.gov (United States)

    Crait, Jamie R; Ben-David, Merav

    2007-04-01

    Animals that deposit aquatically derived nutrients on terrestrial landscapes link food webs and affect a variety of in situ processes. This phenomenon, however, is poorly documented in freshwater habitats, especially where species introductions have drastically changed an ecosystem's trophic structure. In this study, we used stable isotopes to document water-to-land nutrient transport by river otters (Lontra canadensis) around Yellowstone Lake, an ecosystem recently altered by nonnative species invasions. We then investigated the effects of otter fertilization on plant growth and prevalence at latrine (scent-marking) sites and evaluated how the recent changes to the lake's food web could influence these plant responses. Values of delta15N were higher on latrines compared to non-latrine sites in five of seven sample plant taxa. Additionally, latrine grasses had higher percentage N than those from non-latrines. Foliar delta15N positively related to fecal deposition rate for some plants, indicating that increased otter scent-marking led to a rise in these N values. Logistic regression models indicated that otters selected for well-shaded latrines with access to foraging. Atypical latrines, misclassified as non-latrines by the regression models, had values of delta15N similar to correctly classified latrines, suggesting that site effects alone cannot explain elevated N values at otter latrine sites. No difference in plant diversity or percent cover of N-fixing taxa occurred between latrine and nonlatrine sites, though specific genera did differ between site types. Measurements of shoot lengths indicated increased growth of some latrine currants (Ribes sp.). In Yellowstone Lake, a twofold reduction in otter numbers could result in an even greater decline in nutrient deposition at latrines, as otters may become less social in a system with decreased prey availability. Our results highlight the role of animals in linking aquatic and terrestrial habitats in inland

  13. 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

  14. 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

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

    Science.gov (United States)

    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 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. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Impact of the 3 °C temperature rise on bacterial growth and carbon transfer towards higher trophic levels: Empirical models for the Adriatic Sea

    Science.gov (United States)

    Šolić, Mladen; Krstulović, Nada; Šantić, Danijela; Šestanović, Stefanija; Kušpilić, Grozdan; Bojanić, Natalia; Ordulj, Marin; Jozić, Slaven; Vrdoljak, Ana

    2017-09-01

    The Mediterranean Sea (including the Adriatic Sea) has been identified as a 'hotspot' for climate change, with the prediction of the increase in water temperature of 2-4 °C over the next few decades. Being mainly oligotrophic, and strongly phosphorus limited, the Adriatic Sea is characterized by the important role of the microbial food web in production and transfer of biomass and energy towards higher trophic levels. We hypothesized that predicted 3 °C temperature rise in the near future might cause an increase of bacterial production and bacterial losses to grazers, which could significantly enlarge the trophic base for metazoans. This empirical study is based on a combined 'space-for-time substitution' analysis (which is performed on 3583 data sets) and on an experimental approach (36 in situ grazing experiments performed at different temperatures). It showed that the predicted 3 °C temperature increase (which is a result of global warming) in the near future could cause a significant increase in bacterial growth at temperatures lower than 16 °C (during the colder winter-spring period, as well as in the deeper layers). The effect of temperature on bacterial growth could be additionally doubled in conditions without phosphorus limitation. Furthermore, a 3 °C increase in temperature could double the grazing on bacteria by heterotrophic nanoflagellate (HNF) and ciliate predators and it could increase the proportion of bacterial production transferred to the metazoan food web by 42%. Therefore, it is expected that global warming may further strengthen the role of the microbial food web in a carbon cycle in the Adriatic Sea.

  17. Sequestration and activation of plant toxins protect the western corn rootworm from enemies at multiple trophic levels.

    Science.gov (United States)

    Robert, Christelle Am; Zhang, Xi; Machado, Ricardo Ar; Schirmer, Stefanie; Lori, Martina; Mateo, Pierre; Erb, Matthias; Gershenzon, Jonathan

    2017-11-24

    Highly adapted herbivores can phenocopy two-component systems by stabilizing, sequestering and reactivating plant toxins. However, whether these traits protect herbivores against their enemies is poorly understood. We demonstrate that the western corn rootworm Diabrotica virgifera virgifera , the most damaging maize pest on the planet, specifically accumulates the root-derived benzoxazinoid glucosides HDMBOA-Glc and MBOA-Glc. MBOA-Glc is produced by D. virgifera through stabilization of the benzoxazinoid breakdown product MBOA by N-glycosylation. The larvae can hydrolyze HDMBOA-Glc, but not MBOA-Glc, to produce toxic MBOA upon predator attack. Accumulation of benzoxazinoids renders D. virgifera highly resistant to nematodes which inject and feed on entomopathogenic symbiotic bacteria. While HDMBOA-Glc and MBOA reduce the growth and infectivity of both the nematodes and the bacteria, MBOA-Glc repels infective juvenile nematodes. Our results illustrate how herbivores combine stabilized and reactivated plant toxins to defend themselves against a deadly symbiosis between the third and the fourth trophic level enemies.

  18. Importance of the aquatic detritus foodweb in the transfer of radionuclides from water to higher trophic levels

    Energy Technology Data Exchange (ETDEWEB)

    Bird, G.A., E-mail: gbird@ecometrix.ca [EcoMetrix Inc., Mississauga, Ontario (Canada)

    2012-07-01

    Uptake of radionuclides from water to decaying elm-leaf discs and their transfer to the amphipod Gammarus lacustris was investigated. Uptake by decomposing elm leaves is microbially mediated. Uptake coefficients, k, for G. lacustris fed contaminated leaf discs were 3.66▾ d{sup -1} for {sup 60}Co, 4.34▾ d{sup -1} for {sup 131}I and 9.74▾ d{sup -1} for {sup 134}Cs, whereas loss rates were -1.08▾ d{sup -1} for {sup 60}Co, -1.07▾ d{sup -1} for {sup 131}I and -1.04▾ d{sup -1} for {sup 134}Cs. Assimilation efficiencies were 11% for leaf material, 53% for {sup 60}Co, 55% for {sup 131}I and 75% for {sup 134}Cs. These results indicate that there is considerable potential for the transfer of radionuclides to higher trophic levels by the detritus-food web. (author)

  19. 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.

  20. Piscivores, Trophic Cascades, and Lake Management

    Directory of Open Access Journals (Sweden)

    Ray W. Drenner

    2002-01-01

    Full Text Available The concept of cascading trophic interactions predicts that an increase in piscivore biomass in lakes will result in decreased planktivorous fish biomass, increased herbivorous zooplankton biomass, and decreased phytoplankton biomass. Though often accepted as a paradigm in the ecological literature and adopted by lake managers as a basis for lake management strategies, the trophic cascading interactions hypothesis has not received the unequivocal support (in the form of rigorous experimental testing that might be expected of a paradigm. Here we review field experiments and surveys, testing the hypothesis that effects of increasing piscivore biomass will cascade down through the food web yielding a decline in phytoplankton biomass. We found 39 studies in the scientific literature examining piscivore effects on phytoplankton biomass. Of the studies, 22 were confounded by supplemental manipulations (e.g., simultaneous reduction of nutrients or removal of planktivores and could not be used to assess piscivore effects. Of the 17 nonconfounded studies, most did not find piscivore effects on phytoplankton biomass and therefore did not support the trophic cascading interactions hypothesis. However, the trophic cascading interactions hypothesis also predicts that lake systems containing piscivores will have lower phytoplankton biomass for any given phosphorus concentration. Based on regression analyses of chlorophyll�total phosphorus relationships in the 17 nonconfounded piscivore studies, this aspect of the trophic cascading interactions hypothesis was supported. The slope of the chlorophyll vs. total phosphorus regression was lower in lakes with planktivores and piscivores compared with lakes containing only planktivores but no piscivores. We hypothesize that this slope can be used as an indicator of “functional piscivory” and that communities with extremes of functional piscivory (zero and very high represent classical 3- and 4-trophic level

  1. Trophic and individual efficiencies of size-structured communities

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Beyer, Jan; Lundberg, P.

    2009-01-01

    Individual and trophic efficiencies of size-structured communities are derived from mechanistically based principles at the individual level. The derivations are relevant for communities with a size-based trophic structure, i.e. where trophic level is strongly correlated with individual size...... as in many aquatic systems. The derivations are used to link Lindeman's trophic theory and trophic theory based on average individuals with explicit individual-level size spectrum theory. The trophic efficiency based on the transfer of mass between trophic levels through predator-prey interactions...

  2. Ocean acidification increases the accumulation of toxic phenolic compounds across trophic levels

    KAUST Repository

    Jin, Peng

    2015-10-27

    Increasing atmospheric CO2 concentrations are causing ocean acidification (OA), altering carbonate chemistry with consequences for marine organisms. Here we show that OA increases by 46–212% the production of phenolic compounds in phytoplankton grown under the elevated CO2 concentrations projected for the end of this century, compared with the ambient CO2 level. At the same time, mitochondrial respiration rate is enhanced under elevated CO2 concentrations by 130–160% in a single species or mixed phytoplankton assemblage. When fed with phytoplankton cells grown under OA, zooplankton assemblages have significantly higher phenolic compound content, by about 28–48%. The functional consequences of the increased accumulation of toxic phenolic compounds in primary and secondary producers have the potential to have profound consequences for marine ecosystem and seafood quality, with the possibility that fishery industries could be influenced as a result of progressive ocean changes.

  3. Trophic interactions determine the effects of drought on an aquatic ecosystem.

    Science.gov (United States)

    Amundrud, Sarah L; Srivastava, Diane S

    2016-06-01

    Species interactions can be important mediators of community and ecosystem responses to environmental stressors. However, we still lack a mechanistic understanding of the indirect ecological effects of stress that arise via altered species interactions. To understand how species interactions will be altered by environmental stressors, we need to know if the species that are vulnerable to such stressors also have large impacts on the ecosystem. As predators often exhibit certain traits that are linked to a high vulnerability to stress (e.g., large body size, long generation time), as well as having large effects on communities (e.g., top-down trophic effects), predators may be particularly likely to mediate ecological effects of environmental stress. Other functional groups, like facilitators, are known to have large impacts on communities, but their vulnerability to perturbations remains undocumented. Here, we use aquatic insect communities in bromeliads to examine the indirect effects of an important stressor (drought) on community and ecosystem responses. In a microcosm experiment, we manipulated predatory and facilitative taxa under a range of experimental droughts, and quantified effects on community structure and ecosystem function. Drought, by adversely affecting the top predator, had indirect cascading effects on the entire food web, altering community composition and decomposition. We identified the likely pathway of how drought cascaded through the food web from the top-down as drought -->predator --> shredder --> decomposition. This stress-induced cascade depended on predators exhibiting both a strong vulnerability to drought and large impacts on prey (especially shredders), as well as shredders exhibiting high functional importance as decomposers.

  4. 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

  5. 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.

  6. 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.

  7. Mercury Biomagnification between Two Trophic Levels of a Grazing Food Chain (Plankton and Planktivorous Fish in a Fresh Water Ecosystem

    Directory of Open Access Journals (Sweden)

    Mehdi Khoshnamvand

    2017-02-01

    Full Text Available Background: The Present study was carried out to track and calculate Biomagnification Factor (BMF of total mercury (T-Hg between two different trophic levels (i.e., plankton and a planktivorous fish in a fresh water grazing food chain. Methods: Experimental organisms were planktonic biomass and silver carp (Hypophthalmichthys molitrix as a planktivorous fish. Silver carp samples were obtained from randomly selected points from different sampling stations. The concentrations of T-Hg in collected samples were determined by Advanced Mercury Analyzer. Results: Means of T-Hg in planktonic biomass and muscle tissue of silver carp were 78.21 ± 3.13 and 367.12 ± 26.43 ng g-1 dry weights, respectively. Mean T-Hg in plankton, sampled fish during the study months and amongst the sampling stations did not show significant differences. The BMFHg(plankton-fish was differ among months; moreover, calculated BMF was greater than 1 during study months, which means biomagnification was occurring in SGR. The concentration of T-Hg in the muscle tissue of all fish samples that weighed more than 850 gr was higher than the acceptable limits based on EPA (300 ng g-1 and WHO (500 ng g-1 standards. The highest BMFHg was observed in August Conclusion: It seems that mercury pollution of SGR has a natural source. The calculated BMFs were greater than 1 and the concentrations of T-Hg in muscle tissues of those samples weighing more than 850 gr were higher than FAO and WHO standards. Therefore, consumption of the SGR's silver carp must be accompanied by serious health considerations.

  8. 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.

  9. The sensitivity of breeding songbirds to changes in seasonal timing is linked to population change but cannot be directly attributed to the effects of trophic asynchrony on productivity.

    Science.gov (United States)

    Franks, Samantha E; Pearce-Higgins, James W; Atkinson, Sian; Bell, James R; Botham, Marc S; Brereton, Tom M; Harrington, Richard; Leech, David I

    2018-03-01

    A consequence of climate change has been an advance in the timing of seasonal events. Differences in the rate of advance between trophic levels may result in predators becoming mismatched with prey availability, reducing fitness and potentially driving population declines. Such "trophic asynchrony" is hypothesized to have contributed to recent population declines of long-distance migratory birds in particular. Using spatially extensive survey data from 1983 to 2010 to estimate variation in spring phenology from 280 plant and insect species and the egg-laying phenology of 21 British songbird species, we explored the effects of trophic asynchrony on avian population trends and potential underlying demographic mechanisms. Species which advanced their laying dates least over the last three decades, and were therefore at greatest risk of asynchrony, exhibited the most negative population trends. We expressed asynchrony as the annual variation in bird phenology relative to spring phenology, and related asynchrony to annual avian productivity. In warmer springs, birds were more asynchronous, but productivity was only marginally reduced; long-distance migrants, short-distance migrants and resident bird species all exhibited effects of similar magnitude. Long-term population, but not productivity, declines were greatest among those species whose annual productivity was most greatly reduced by asynchrony. This suggests that population change is not mechanistically driven by the negative effects of asynchrony on productivity. The apparent effects of asynchrony on population trends are therefore either more likely to be strongly expressed via other demographic pathways, or alternatively, are a surrogate for species' sensitivity to other environmental pressures which are the ultimate cause of decline. © 2017 John Wiley & Sons Ltd.

  10. Trophic transfer and effects of gold nanoparticles (AuNPs) in Gammarus fossarum from contaminated periphytic biofilm.

    Science.gov (United States)

    Baudrimont, Magalie; Andrei, Jennifer; Mornet, Stéphane; Gonzalez, Patrice; Mesmer-Dudons, Nathalie; Gourves, Pierre-Yves; Jaffal, Ali; Dedourge-Geffard, Odile; Geffard, Alain; Geffard, Olivier; Garric, Jeanne; Feurtet-Mazel, Agnès

    2017-01-13

    This work addressed the trophic transfer and effects of functionalized gold nanoparticles (AuNPs) from periphytic biofilms to the crustacean Gammarus fossarum. Biofilms were exposed for 48 h to 10 nm positively charged functionalized AuNPs at two concentrations, 4.6 and 46 mg/L, and crustaceans G. fossarum grazed on these for 7 days, with daily biofilm renewal. Gold bioaccumulation in biofilm and crustacean were measured to estimate the trophic transfer ratio of these AuNP, and, for the first time, a transcriptomic approach and transmission electron microscopy observations in the crustacean were made. These two approaches showed cellular damage caused by oxidative stress and, in particular, an impact of these AuNPs on mitochondrial respiration. Modulation of digestive enzyme activity was also observed, suggesting modifications of digestive functions. The damage due to these nanoparticles could then have vital consequences for the organisms during chronic exposure.

  11. 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.

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

    Science.gov (United States)

    Blanco-Fontao, Beatriz; Sandercock, Brett K; Obeso, José Ramón; McNew, Lance B; Quevedo, Mario

    2013-01-01

    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. 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.

  14. Lepidoptera Larvae as an Indicator of Multi-trophic Level Responses to Changing Seasonality in an Arctic Tundra Ecosystem

    Science.gov (United States)

    Daly, K. M.; Steltzer, H.; Boelman, N.; Weintraub, M. N.; Darrouzet-Nardi, A.; Wallenstein, M. D.; Sullivan, P.; Gough, L.; Rich, M.; Hendrix, C.; Kielland, K.; Philip, K.; Doak, P.; Ferris, C.; Sikes, D.

    2011-12-01

    Earlier snowmelt and warming temperatures in the Arctic will impact multiple trophic levels through the timing and availability of food resources. Lepidoptera are a vital link within the ecosystem; their roles include pollinator, parasitized host for other pollinating insects, and essential food source for migrating birds and their fledglings. Multiple environmental cues including temperature initiate plant growth, and in turn, trigger the emergence of Lepidoptera and the migrations of birds. If snowmelt is accelerated and temperature is increased, it is expected that the Lepidoptera larvae will respond to early plant growth by increasing their abundance within areas that have accelerated snowmelt and warmer conditions. In May of 2011 in a moist acidic tussock tundra system, we accelerated snowmelt by 15 days through the use of radiation-absorbing fabric and warmed air and soil temperatures using open-top chambers, individually and in combination. Every 1-2 days from May 27th to July 8th, 2 minute searches were performed for Lepidoptera larvae in all treatments; when an animal was found, their micro-habitat, surface temperature, behavior, food source, and time of day were noted. The length, body and head width were measured, and the animals were examined for braconid wasp and tachinid fly parasites. Lepidoptera larvae collected in pitfall traps from May 26th to July 7th were also examined and measured. Total density of parasitized larvae accounted for 54% of observed specimens and 50% of pitfall specimens, indicating that Lepidoptera larvae serve an integral role as a host for other pollinators. Total larvae density was highest within the accelerated snowmelt plots compared to the control plots; 66% of observed live specimens and 63% of pitfall specimens were found within the accelerated snowmelt plots. Ninety percent of the total observed animals were found within the open-top warming chambers. Peak density of animals occurred at Solar Noon between 14:00 -15

  15. 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.

  16. An abundant small sized fish as keystone species? The effect of Pomatoschistus microps on food webs and its trophic role in two intertidal benthic communities: A modeling approach

    Science.gov (United States)

    Pockberger, Moritz; Kellnreitner, Florian; Ahnelt, Harald; Asmus, Ragnhild; Asmus, Harald

    2014-02-01

    Ecological network analysis (ENA) was used to study the effects of Pomatoschistus microps on energy transport through the food web, its impact on other compartments and its possible role as a keystone species in the trophic webs of an Arenicola tidal flat ecosystem and a sparse Zostera noltii bed ecosystem. Three ENA models were constructed: (a) model 1 contains data of the original food web from prior research in the investigated area by Baird et al. (2007), (b) an updated model 2 which included biomass and diet data of P. microps from recent sampling, and (c) model 3 simulating a food web without P. microps. A comparison of energy transport between the different models revealed that more energy is transported from lower trophic levels up the food chain, in the presence of P. microps (models 1 and 2) than in its absence (model 3). Calculations of the keystone index (KSi) revealed the high overall impact (measured as εi) of this fish species on food webs. In model 1, P. microps was assigned a low KSi in the Arenicola flat and in the sparse Z. noltii bed. Calculations in model 2 ranked P. microps first for keystoneness and εi in both communities, the Arenicola flat and the sparse Z. noltii bed. Taken together, our results give insight into the role of P. microps when considering a whole food web and reveal direct and indirect trophic interactions of this small-sized fish species. These results might illustrate the impact and importance of abundant, widespread species in food webs and facilitate further investigations.

  17. 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....

  18. Stimulation of the N-methyl-D-aspartate receptor has a trophic effect on differentiating cerebellar granule cells

    DEFF Research Database (Denmark)

    Balázs, R; Hack, N; Jørgensen, Ole Steen

    1988-01-01

    -CAM contents indicated that NMDA rescued primarily nerve cells. The influence of NMDA in promoting cell survival was blocked by the receptor antagonist, 2-amino-5-phosphonovalerate. The effect depended both on the concentration of NMDA and on the degree of depolarization of cells, the affinity in the presence...... of 15 mM K+ being similar to that of NMDA receptor binding. The results attest a new role for excitatory amino acid transmitters by showing that they can exert a stage-dependent trophic action on developing nerve cells....

  19. Effects of enhanced UV-B radiation on secondary metabolites in forage plants and potential consequences for multiple trophic responses involving mammalian herbivores

    Science.gov (United States)

    Thines, Nicole J.; Bassman, John H.; Shipley, Lisa A.; Slusser, James R.

    2004-10-01

    Herbivores represent the interface between primary production and higher trophic levels. The effects of enhanced UV-B radiation on microbes, invertebrate herbivores, and detritivores has received limited study in both terrestrial and aquatic ecosystems. However, although direct effects (e.g. melanoma, cataracts) on mammals have been documented, indirect effects (e.g., resulting from changes in plant chemistry) of enhanced UV-B on mammalian herbivores have not been evaluated. Although the diet of mammalian herbivores has little effect on nutritional quality for their associated predators, to the extent changes in plant chemistry affect aspects of population dynamics (e.g., growth, fecundity, densities), higher trophic levels can be affected. In this study, different forage species of varying inherent levels of key secondary metabolites are being grown in the field under either ambient or ambient plus supplemental UV-B radiation simulating a 15% stratospheric ozone depletion for Pullman, Washington. At various time intervals, foliage is being sampled and analyzed for changes in secondary metabolites and other attributes. Using controlled feeding trials, changes in plant secondary metabolites are being related to preference and digestibility in specialist and generalist mammalian hindgut herbivores, digestion in ruminants and non-ruminants, and to selected aspects of population dynamics in mammalian herbivores. Results suggest how UV-B-induced changes in plant secondary chemistry affect animal nutrition, and thus animal productivity in a range of mammalian herbivores. Reductions in palatability and digestibility of plant material along with reductions in fecundity and other aspects of population dynamics could have significant economic ramifications for farmers, ranchers and wildlife biologists.

  20. 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.

  1. 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.

  2. Effects of sewage discharge on trophic state and water quality in a coastal ecosystem of the Gulf of California.

    Science.gov (United States)

    Vargas-González, Héctor Hugo; Arreola-Lizárraga, José Alfredo; Mendoza-Salgado, Renato Arturo; Méndez-Rodríguez, Lía Celina; Lechuga-Deveze, Carlos Hernando; Padilla-Arredondo, Gustavo; Cordoba-Matson, Miguel

    2014-01-01

    This paper provides evidence of the effects of urban wastewater discharges on the trophic state and environmental quality of a coastal water body in a semiarid subtropical region in the Gulf of California. The concentrations of dissolved inorganic nutrients and organic matter from urban wastewater primary treatment were estimated. La Salada Cove was the receiving water body and parameters measured during an annual cycle were temperature, salinity, dissolved oxygen, nitrite, nitrate, ammonia, orthophosphate, and chlorophyll a. The effects of sewage inputs were determined by using Trophic State Index (TRIX) and the Arid Zone Coastal Water Quality Index (AZCI). It was observed that urban wastewater of the city of Guaymas provided 1,237 ton N yr(-1) and 811 ton P yr(-1) and TRIX indicated that the receiving water body showed symptoms of eutrophication from an oligotrophic state to a mesotrophic state; AZCI also indicated that the environmental quality of the water body was poor. The effects of urban wastewater supply with insufficient treatment resulted in symptoms of eutrophication and loss of ecological functions and services of the coastal ecosystem in La Salada Cove.

  3. 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.

  4. Population-Level Metrics of Trophic Structure Based on Stable Isotopes and Their Application to Invasion Ecology

    Science.gov (United States)

    Jackson, Michelle C.; Donohue, Ian; Jackson, Andrew L.; Britton, J. Robert; Harper, David M.; Grey, Jonathan

    2012-01-01

    Biological invasions are a significant driver of human-induced global change and many ecosystems sustain sympatric invaders. Interactions occurring among these invaders have important implications for ecosystem structure and functioning, yet they are poorly understood. Here we apply newly developed metrics derived from stable isotope data to provide quantitative measures of trophic diversity within populations or species. We then use these to test the hypothesis that sympatric invaders belonging to the same functional feeding group occupy a smaller isotopic niche than their allopatric counterparts. Two introduced, globally important, benthic omnivores, Louisiana swamp crayfish (Procambarus clarkii) and carp (Cyprinus carpio), are sympatric in Lake Naivasha, Kenya. We applied our metrics to an 8-year data set encompassing the establishment of carp in the lake. We found a strong asymmetric interaction between the two invasive populations, as indicated by inverse correlations between carp abundance and measures of crayfish trophic diversity. Lack of isotopic niche overlap between carp and crayfish in the majority of years indicated a predominantly indirect interaction. We suggest that carp-induced habitat alteration reduced the diversity of crayfish prey, resulting in a reduction in the dietary niche of crayfish. Stable isotopes provide an integrated signal of diet over space and time, offering an appropriate scale for the study of population niches, but few isotope studies have retained the often insightful information revealed by variability among individuals in isotope values. Our population metrics incorporate such variation, are robust to the vagaries of sample size and are a useful additional tool to reveal subtle dietary interactions among species. Although we have demonstrated their applicability specifically using a detailed temporal dataset of species invasion in a lake, they have a wide array of potential ecological applications. PMID:22363724

  5. Eco-Evolutionary Trophic Dynamics: Loss of Top Predators Drives Trophic Evolution and Ecology of Prey

    Science.gov (United States)

    Palkovacs, Eric P.; Wasserman, Ben A.; Kinnison, Michael T.

    2011-01-01

    Ecosystems are being altered on a global scale by the extirpation of top predators. The ecological effects of predator removal have been investigated widely; however, predator removal can also change natural selection acting on prey, resulting in contemporary evolution. Here we tested the role of predator removal on the contemporary evolution of trophic traits in prey. We utilized a historical introduction experiment where Trinidadian guppies (Poecilia reticulata) were relocated from a site with predatory fishes to a site lacking predators. To assess the trophic consequences of predator release, we linked individual morphology (cranial, jaw, and body) to foraging performance. Our results show that predator release caused an increase in guppy density and a “sharpening” of guppy trophic traits, which enhanced food consumption rates. Predator release appears to have shifted natural selection away from predator escape ability and towards resource acquisition ability. Related diet and mesocosm studies suggest that this shift enhances the impact of guppies on lower trophic levels in a fashion nuanced by the omnivorous feeding ecology of the species. We conclude that extirpation of top predators may commonly select for enhanced feeding performance in prey, with important cascading consequences for communities and ecosystems. PMID:21526156

  6. Eco-evolutionary trophic dynamics: loss of top predators drives trophic evolution and ecology of prey.

    Directory of Open Access Journals (Sweden)

    Eric P Palkovacs

    Full Text Available Ecosystems are being altered on a global scale by the extirpation of top predators. The ecological effects of predator removal have been investigated widely; however, predator removal can also change natural selection acting on prey, resulting in contemporary evolution. Here we tested the role of predator removal on the contemporary evolution of trophic traits in prey. We utilized a historical introduction experiment where Trinidadian guppies (Poecilia reticulata were relocated from a site with predatory fishes to a site lacking predators. To assess the trophic consequences of predator release, we linked individual morphology (cranial, jaw, and body to foraging performance. Our results show that predator release caused an increase in guppy density and a "sharpening" of guppy trophic traits, which enhanced food consumption rates. Predator release appears to have shifted natural selection away from predator escape ability and towards resource acquisition ability. Related diet and mesocosm studies suggest that this shift enhances the impact of guppies on lower trophic levels in a fashion nuanced by the omnivorous feeding ecology of the species. We conclude that extirpation of top predators may commonly select for enhanced feeding performance in prey, with important cascading consequences for communities and ecosystems.

  7. 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.

  8. Trophic level, successional age and trait matching determine specialization of deadwood-based interaction networks of saproxylic beetles.

    Science.gov (United States)

    Wende, Beate; Gossner, Martin M; Grass, Ingo; Arnstadt, Tobias; Hofrichter, Martin; Floren, Andreas; Linsenmair, Karl Eduard; Weisser, Wolfgang W; Steffan-Dewenter, Ingolf

    2017-05-17

    The specialization of ecological networks provides important insights into possible consequences of biodiversity loss for ecosystem functioning. However, mostly mutualistic and antagonistic interactions of living organisms have been studied, whereas detritivore networks and their successional changes are largely unexplored. We studied the interactions of saproxylic (deadwood-dependent) beetles with their dead host trees. In a large-scale experiment, 764 logs of 13 tree species were exposed to analyse network structure of three trophic groups of saproxylic beetles over 3 successional years. We found remarkably high specialization of deadwood-feeding xylophages and lower specialization of fungivorous and predatory species. During deadwood succession, community composition, network specialization and network robustness changed differently for the functional groups. To reveal potential drivers of network specialization, we linked species' functional traits to their network roles, and tested for trait matching between plant (i.e. chemical compounds) and beetle (i.e. body size) traits. We found that both plant and animal traits are major drivers of species specialization, and that trait matching can be more important in explaining interactions than neutral processes reflecting species abundance distributions. High network specialization in the early successional stage and decreasing network robustness during succession indicate vulnerability of detritivore networks to reduced tree species diversity and beetle extinctions, with unknown consequences for wood decomposition and nutrient cycling. © 2017 The Author(s).

  9. 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.

  10. Salmon carcasses increase stream productivity more than inorganic fertilizer pellets: A test on multiple trophic levels in streamside experimental channels

    Science.gov (United States)

    Wipfli, Mark S.; Hudson, John P.; Caouette, John P.; Mitchell, N.L.; Lessard, Joanna L.; Heintz, Ron A.; Chaloner, D.T.

    2010-01-01

    Inorganic nutrient amendments to streams are viewed as possible restoration strategies for re-establishing nutrients and stream productivity throughout the western coast of North America, where salmon runs and associated marine-derived nutrient subsidies have declined. In a mesocosm experiment, we examined the short-term (6 weeks) comparative effects of artificial nutrient pellets and salmon carcasses, alone (low and high amounts) and in combination, on stream food webs. Response variables included dissolved nutrient concentrations, biofilm ash-free dry mass (AFDM) and chlorophyll-alevels, macroinvertebrate density, growth and body condition of juvenile coho salmon Oncorhynchus kisutch, and whole-body lipid content of invertebrates and juvenile coho salmon. Most of the response variables were significantly influenced by carcass treatment; the only response variable significantly influenced by fertilizer pellet treatment was soluble reactive phosphorus (SRP) concentration. Ammonium-nitrogen concentration was the only response variable affected by both (low and high) levels of carcass treatment; all others showed no significant response to the two carcass treatment levels. Significant treatment × time interactions were observed for all responses except nitrate; for most responses, significant treatment effects were detected at certain time periods and not others. For example, significantly higher SRP concentrations were recorded earlier in the experiment, whereas significant fish responses were observed later. These results provide evidence that inorganic nutrient additions do not have the same ecological effects in streams as do salmon carcasses, potentially because inorganic nutrient additions lack carbon-based biochemicals and macromolecules that are sequestered directly or indirectly by consumers. Salmon carcasses, preferably deposited naturally during spawning migrations, appear to be far superior to inorganic nutrient amendments for sustaining and restoring

  11. Temporal trends of mercury, cesium, potassium, selenium, and thallium in Arctic char (Salvelinus alpinus) from Lake Hazen, Nunavut, Canada: effects of trophic position, size, and age.

    Science.gov (United States)

    Gantner, Nikolaus; Power, Michael; Babaluk, John A; Reist, James D; Köck, Günter; Lockhart, Lyle W; Solomon, Keith R; Muir, Derek C G

    2009-02-01

    Arctic char (Salvelinus alpinus L.), the top predator in High Arctic lakes, often is used as a bioindicator of Hg contamination in Arctic aquatic ecosystems. The present study investigated effects of trophic position, size, and age of Arctic char in Lake Hazen, the largest lake in the Canadian High Arctic (81 degrees 50'N, 70 degrees 25'W), on Hg bioaccumulation. In addition, several essential (Se, K) and nonessential elements (Tl, Cs) in char muscle tissue were examined to compare their behavior to that of Hg. Trophic position of Arctic char was identified by stable isotope (delta15N) signature. Temporal trends of Hg from seven sampling campaigns over a 16-year period (1990-2006) were investigated for the overall data and for one trophic class. Concentrations of Hg were not correlated with age but were positively related to fork length and trophic position. Large char with greater delta15N signatures (> 12 per thousand) had larger Hg concentrations (0.09-1.63 microg/g wet wt) than small char with smaller delta15N signatures (fish size when monitoring temporal trends of Hg, particularly for species with different morphotypes.

  12. 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.

  13. Tissue specificity of 8-prenylnaringenin: protection from ovariectomy induced bone loss with minimal trophic effects on the uterus.

    Science.gov (United States)

    Hümpel, Michael; Isaksson, Päivi; Schaefer, Olaf; Kaufmann, Ulrike; Ciana, Paolo; Maggi, Adriana; Schleuning, Wolf-Dieter

    2005-11-01

    Plant secondary metabolites with estrogenic activity (phyto-estrogens) have been studied in the past as a potential alternative to classical hormone-replacement therapy (HRT) in menopausal women. No final verdict on the efficacy of soy or red clover based pharmaceutical preparations has been reached despite numerous clinical studies. We have studied the novel and most potent phyto-estrogen 8-prenylnaringenin (8-PN) in adult ovariectomized rats, an established animal model to mimic hormone dependent osteoporosis in menopausal women. Our results demonstrate that 8-PN can completely protect from ovariectomy induced bone-loss while exhibiting minimal, (dose independent) trophic effects on uterus and endometrium. It is estimated that at equivalent bone protective doses of 17beta-estradiol and 8-PN, the phyto-estrogen has a 10-fold lower stimulatory effect on uterus and endometrium. The bone tissue specific effect of 8-PN was confirmed in a transgenic reporter mouse model (ERE-Luc mice). Here we also found pronounced estrogenic activity in prostate. Present results add important aspects to the pharmacological profile of 8-PN and position this compound as an interesting alternative new candidate for treatment of peri- and postmenopausal symptoms.

  14. Crayfish as trophic agents: Effect of Austropotamobius torrentium on zoobenthos structure and function in small forest streams

    Directory of Open Access Journals (Sweden)

    Weinländer M.

    2011-07-01

    Full Text Available Crayfish are among the largest and most threatened invertebrates in freshwater habitats. Due to their size, behaviour and feeding activity they may affect structure and function of aquatic ecosystems and their organisms. Despite their importance in many freshwaters and available information on their ecology for several species little is known about the European crayfish Austropotamobius torrentium. In order to evaluate the potential effects of indigenous crayfish presence on the structural and functional composition of the zoobenthic community, we measured population size and densities of three A. torrentium populations and compared macroinvertebrate assemblages and physicochemical parameters in three streams with and three without crayfish. The experimental setup considered crayfish effects at a large scale in defined reaches of pristine headwaters in association with the whole benthic fauna under natural conditions. Presence of A. torrentium significantly affected zoobenthic abundance, diversity and the relative proportions of functional feeding groups. In crayfish streams, especially Trichoptera and collector gatherers were more abundant and diverse, while sites without crayfish had significantly higher abundances and diversities of shredders and wood feeders. Our study provided strong evidence that the presence of the indigenous crayfish A. torrentium had important effects on the trophic cascades of headwater stream communities.

  15. The importance of individual and species-level traits for trophic niches among herbivorous coral reef fishes.

    Science.gov (United States)

    Allgeier, Jacob E; Adam, Thomas C; Burkepile, Deron E

    2017-06-14

    Resolving how species compete and coexist within ecological communities represents a long-standing challenge in ecology. Research efforts have focused on two predominant mechanisms of species coexistence: complementarity and redundancy. But findings also support an alternative hypothesis that within-species variation may be critical for coexistence. Our study focuses on nine closely related and ecologically similar coral reef fish species to test the importance of individual- versus species-level traits in determining the size of dietary, foraging substrate, and behavioural interaction niches. Specifically, we asked: (i) what level of biological organization best describes individual-level niches? and (ii) how are herbivore community niches partitioned among species, and are niche widths driven by species- or individual-level traits? Dietary and foraging substrate niche widths were best described by species identity, but no level of taxonomy explained behavioural interactions. All three niches were dominated by only a few species, contrasting expectations of niche complementarity. Species- and individual-level traits strongly drove foraging substrate and behavioural niches, respectively, whereas the dietary niche was described by both. Our findings underscored the importance of species-level traits for community-level niches, but highlight that individual-level trait variation within a select few species may be a key driver of the overall size of niches. © 2017 The Author(s).

  16. Toxic Identification and Evaluation of Androgen Receptor Antagonistic Activities in Acid-Treated Liver Extracts of High-Trophic Level Wild Animals from Japan.

    Science.gov (United States)

    Misaki, Kentaro; Suzuki, Go; Tue, Nguyen Minh; Takahashi, Shin; Someya, Masayuki; Takigami, Hidetaka; Tajima, Yuko; Yamada, Tadasu K; Amano, Masao; Isobe, Tomohiko; Tanabe, Shinsuke

    2015-10-06

    Sulfuric acid-treated liver extracts of representative high-trophic level Japanese animals were analyzed by toxic identification and evaluation (TIE) with chemically activated luciferase expression (CALUX) and chemical analysis to elucidate androgen receptor (AR) antagonistic activities and potential contributions of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). The activities were detected in striped dolphins (n = 5), Stejneger's beaked whales (n = 6), golden eagle (n = 1), and Steller's sea eagle (n = 1) with CALUX-flutamide equivalents (FluEQs) as follow: 38 (20-52), 47 (21-96), 5.0, and 80 μg FluEQ/g-lipid, respectively. The AR antagonism was detected in limited number of specimens at lower levels for finless porpoise, raccoon dog, and common cormorant. Theoretical activities (Theo-FluEQs) were calculated using the concentration of OCPs and PCBs and their IC25-based relative potency (REP) values. These total contribution to CALUX-FluEQ was 126%, 84%, 53%, 55%, and 44% for striped dolphin, Steller's sea eagle, Stejneger's beaked whale, finless porpoise, and golden eagle, respectively, and the main contributor was p,p'-DDE. However, most of the activities for raccoon dog (7.6%) and common cormorant (17%) could not be explained by OCPs and PCBs. This suggests other unknown compounds could function as AR antagonists in these terrestrial species.

  17. Trophic complexity enhances ecosystem functioning in an aquatic detritus-based model system.

    Science.gov (United States)

    Jabiol, Jérémy; McKie, Brendan G; Bruder, Andreas; Bernadet, Caroline; Gessner, Mark O; Chauvet, Eric

    2013-09-01

    1. Understanding the functional significance of species interactions in ecosystems has become a major challenge as biodiversity declines rapidly worldwide. Ecosystem consequences arising from the loss of diversity either within trophic levels (horizontal diversity) or across trophic levels (vertical diversity) are well documented. However, simultaneous losses of species at different trophic levels may also result in interactive effects, with potentially complex outcomes for ecosystem functioning. 2. Because of logistical constraints, the outcomes of such interactions have been difficult to assess in experiments involving large metazoan species. Here, we take advantage of a detritus-based model system to experimentally assess the consequences of biodiversity change within both horizontal and vertical food-web components on leaf-litter decomposition, a fundamental process in a wide range of ecosystems. 3. Our concurrent manipulation of fungal decomposer diversity (0, 1 or 5 species), detritivore diversity (0, 1 or 3 species), and the presence of predatory fish scent showed that trophic complexity is key to eliciting diversity effects on ecosystem functioning. Specifically, although fungi and detritivores tended to promote decomposition individually, rates were highest in the most complete community where all trophic levels were represented at the highest possible species richness. In part, the effects were trait-mediated, reflected in the contrasting foraging responses of the detritivore species to predator scent. 4. Our results thus highlight the importance of interactive effects of simultaneous species loss within multiple trophic levels on ecosystem functioning. If a common phenomenon, this outcome suggests that functional ecosystem impairment resulting from widespread biodiversity loss could be more severe than inferred from previous experiments confined to varying diversity within single trophic levels. © 2013 The Authors. Journal of Animal Ecology © 2013

  18. 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.

  19. Condition factor variations over time and trophic position among four species of Characidae from Amazonian floodplain lakes: effects of an anomalous drought.

    Science.gov (United States)

    Tribuzy-Neto, I A; Conceição, K G; Siqueira-Souza, F K; Hurd, L E; Freitas, C E C

    2017-08-17

    The effects of extreme droughts on freshwater fish remain unknown worldwide. In this paper, we estimated the condition factor, a measure of relative fitness based on the relationship of body weight to length, in four fish species representing two trophic levels (omnivores and piscivores) from Amazonian floodplain lakes for three consecutive years: 2004, 2005 (an anomalous drought year), and 2006. The two omnivores, Colossoma macropomum and Mylossoma duriventre, exhibited trends consistent with their life cycles in 2004 and 2006: high values during the hydrologic seasons of high water, receding water, and low water, with a drop following reproduction following the onset of rising water. However during the drought year of 2005 the condition factor was much lower than normal during receding and low water seasons, probably as a result of an abnormal reduction in resource availability in a reduced habitat. The two piscivorous piranhas, Serrasalmus spilopleura and S. elongatus, maintained relatively stable values of condition factor over the hydrologic cycles of all three years, with no apparent effect of the drought, probably because the reduction in habitat is counterbalanced by the resulting increase in relative prey density. We suggest that if predictions of increasing drought in the Amazon are correct, predatory species may benefit, at least in the short run, while omnivores may be negatively affected.

  20. 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.

  1. The tri-trophic interactions hypothesis: interactive effects of host plant quality, diet breadth and natural enemies on herbivores.

    Directory of Open Access Journals (Sweden)

    Kailen A Mooney

    Full Text Available Several influential hypotheses in plant-herbivore and herbivore-predator interactions consider the interactive effects of plant quality, herbivore diet breadth, and predation on herbivore performance. Yet individually and collectively, these hypotheses fail to address the simultaneous influence of all three factors. Here we review existing hypotheses, and propose the tri-trophic interactions (TTI hypothesis to consolidate and integrate their predictions. The TTI hypothesis predicts that dietary specialist herbivores (as compared to generalists should escape predators and be competitively dominant due to faster growth rates, and that such differences should be greater on low quality (as compared to high quality host plants. To provide a preliminary test of these predictions, we conducted an empirical study comparing the effects of plant (Baccharis salicifolia quality and predators between a specialist (Uroleucon macolai and a generalist (Aphis gossypii aphid herbivore. Consistent with predictions, these three factors interactively determine herbivore performance in ways not addressed by existing hypotheses. Compared to the specialist, the generalist was less fecund, competitively inferior, and more sensitive to low plant quality. Correspondingly, predator effects were contingent upon plant quality only for the generalist. Contrary to predictions, predator effects were weaker for the generalist and on low-quality plants, likely due to density-dependent benefits provided to the generalist by mutualist ants. Because the TTI hypothesis predicts the superior performance of specialists, mutualist ants may be critical to A. gossypii persistence under competition from U. macolai. In summary, the integrative nature of the TTI hypothesis offers novel insight into the determinants of plant-herbivore and herbivore-predator interactions and the coexistence of specialist and generalist herbivores.

  2. Heated communities: : large inter- and intraspecific variation in heat tolerance across trophic levels of a soil arthropod community

    NARCIS (Netherlands)

    Franken, Oscar; Huizinga, Milou; Ellers, Jacintha; Berg, Matty P

    Temperature extremes are predicted to increase in frequency, intensity and duration under global warming and are believed to significantly affect community composition and functioning. However, the effect of extreme climatic events on communities remains difficult to predict, especially because

  3. Trophic tangles through time? Opposing direct and indirect effects of an invasive omnivore on stream ecosystem processes.

    Directory of Open Access Journals (Sweden)

    Jonathan W Moore

    Full Text Available Omnivores can impact ecosystems via opposing direct or indirect effects. For example, omnivores that feed on herbivores and plants could either increase plant biomass due to the removal of herbivores or decrease plant biomass due to direct consumption. Thus, empirical quantification of the relative importance of direct and indirect impacts of omnivores is needed, especially the impacts of invasive omnivores. Here we investigated how an invasive omnivore (signal crayfish, Pacifastacus leniusculus impacts stream ecosystems. First, we performed a large-scale experiment to examine the short-term (three month direct and indirect impacts of crayfish on a stream food web. Second, we performed a comparative study of un-invaded areas and areas invaded 90 years ago to examine whether patterns from the experiment scaled up to longer time frames. In the experiment, crayfish increased leaf litter breakdown rate, decreased the abundance and biomass of other benthic invertebrates, and increased algal production. Thus, crayfish controlled detritus via direct consumption and likely drove a trophic cascade through predation on grazers. Consistent with the experiment, the comparative study also found that benthic invertebrate biomass decreased with crayfish. However, contrary to the experiment, crayfish presence was not significantly associated with higher leaf litter breakdown in the comparative study. We posit that during invasion, generalist crayfish replace the more specialized native detritivores (caddisflies, thereby leading to little long-term change in net detrital breakdown. A feeding experiment revealed that these native detritivores and the crayfish were both effective consumers of detritus. Thus, the impacts of omnivores represent a temporally-shifting interplay between direct and indirect effects that can control basal resources.

  4. 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.

  5. 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...

  6. Effects of Environmental Factors on Nutrients Release at Sediment-Water Interface and Assessment of Trophic Status for a Typical Shallow Lake, Northwest China

    Directory of Open Access Journals (Sweden)

    Dekun Hou

    2013-01-01

    Full Text Available Surface sediment and water samples were collected from Daihai Lake to study the biogeochemical characteristics of nitrogen and phosphorus, to estimate the loads of these nutrients, and to assess their effects on water quality. The contents and spatial distributions of total phosphorus (TP, total nitrogen (TN, and different nitrogen forms in sediments were analyzed. The results showed that concentrations of TN and TP in surface sediments ranged from 0.27 to 1.78 g/kg and from 558.31 to 891.29 mg/kg, respectively. Ratios of C : N ranged between 8.2 and 12.1, which indicated that nitrogen accumulated came mainly from terrestrial source. Ratios of N : P in all sampling sites were below 10, which indicated that N was the limiting nutrient for algal growth in this lake. Effects of environment factors on the release of nitrogen and phosphorus in lake sediments were also determined; high pH values could encourage the release of nitrogen and phosphorus. Modified Carlson’s trophic state index (TSIM and comprehensive trophic state index (TSIC were applied to ascertain the trophic classification of the studied lake, and the values of TSIM and TSIC ranged from 53.72 to 70.61 and from 47.73 to 53.67, respectively, which indicated that the Daihai Lake was in the stage of hypereutropher.

  7. Effects of changes in reservoir operations on water quality and trophic state indicators in Voyageurs National Park, northern Minnesota, 2001-03

    Science.gov (United States)

    Christensen, Victoria G.; Payne, G.A.; Kallemeyn, Larry W.

    2004-01-01

    Implementation of an order by the International Joint Commission in January 2000 has changed operating procedures for dams that regulate two large reservoirs in Voyageurs National Park in northern Minnesota. These new procedures were expected to restore a more natural water regime and affect water levels, water quality, and trophic status. Results of laboratory analyses and field measurements of chemical and physical properties from May 2001 through September 2003 were compared to similar data collected prior to the change in operating procedures. Rank sum tests showed significant decreases in chlorophyll-a concentrations and trophic state indices for Kabetogama Lake (p=0.021) and Black Bay (p=0.007). There were no significant decreases in total phosphorus concentration, however, perhaps due to internal cycling of phosphorus. No sites had significant trends in seasonal total phosphorus concentrations, with the exception of May samples from Sand Point Lake, which had a significant decreasing trend (tau=-0.056, probability=0.03). May chlorophyll-a concentrations for Kabetogama Lake showed a significant decreasing trend (tau=-0.42, probability=0.05). Based on mean chlorophyll trophic-state indices (2001-03), Sand Point, Namakan, and Rainy Lakes would be classified oligotrophic to mesotrophic, and Kabetogama Lake and Rainy Lake at Black Bay would be classified as mesotrophic. The classification of Sand Point, Namakan, and Rainy Lakes remain the same for data collected prior to the change in operating procedures. In contrast, the trophic classification of Kabetogama Lake and Rainy Lake at Black Bay has changed from eutrophic to mesotrophic.

  8. Mercury concentrations in breast feathers of three upper trophic level marine predators from the western Aleutian Islands, Alaska

    Science.gov (United States)

    Kaler, Robb S.A.; Kenney, Leah A.; Bond, Alexander L.; Eagles-Smith, Collin A.

    2014-01-01

    Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz’s murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands.

  9. 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...

  10. Metal concentrations in Unio pictorum mancus (Mollusca, Lamellibranchia from of 12 Northern Italian lakes in relation to their trophic level

    Directory of Open Access Journals (Sweden)

    Paolo LODIGIANI

    2003-08-01

    the other hand mussels may be very useful for other purposes, such as identifying new pollutants or pollutants present in such low concentrations that they cannot be measured with the commonly used methods. The pollutant content of mussels may enable the variations in time of the pollutant level of an environment to be monitored. In addition, the transplantation of mussels from a clean site to a polluted one may be a useful tool for identify the pollutants of the receiving environment.

  11. Factors determining accumulation of bisphenol A and alkylphenols at a low trophic level as exemplified by mussels Mytilus trossulus.

    Science.gov (United States)

    Staniszewska, Marta; Graca, Bożena; Sokołowski, Adam; Nehring, Iga; Wasik, Andrzej; Jendzul, Anna

    2017-01-01

    The aim of the study was to investigate abiotic and biotic factors influencing the accumulation of endocrine disrupting compounds (EDCs) such as bisphenol A (BPA), 4-tert-octylphenol (OP) and 4-nonylphenol (NP) in mussels Mytilus trossulus from the Gulf of Gdansk (Southern Baltic). The key abiotic factor influencing BPA, OP and NP accumulation in mussels is their hydrophilicity/lipophilicity, which affects their main assimilation routes - by digestive tract for the more lipophilic OP and NP, and additionally by the gills for the less lipophilic BPA. As a result, high condition index (i.e. higher soft tissue weight) is more often correlated with high concentrations of OP and NP in mussels than with BPA. Furthermore, alkylphenols have 6-8 times greater accumulative potential than BPA. Concentration of the studied compounds was lower in females than in males following spawning, and the effect lasted longer for BPA than for alkylphenols. The influence of season and hydrological conditions on BPA, OP, NP in the mussel was more pronounced than the proximity of external sources of these compounds. An increase in water temperature in summer probably stimulated the solubility of BPA, the least lipophilic of the studied compounds, and led to increased assimilation of this compound from water (through gills). On the other hand, high OP and NP concentrations in mussels occurred in spring, which was caused by increased surface run-off and sediments resuspension. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Interleukin-1β has trophic effects in microglia and its release is mediated by P2X7R pore.

    Science.gov (United States)

    Monif, Mastura; Reid, Christopher A; Powell, Kim L; Drummond, Katherine J; O'Brien, Terrence J; Williams, David A

    2016-06-30

    Enhanced expression of the purinergic P2X7 receptor (P2X7R) occurs in several neuroinflammatory conditions where increased microglial activation is a co-existing feature. P2X7 receptors can function either as a cation channel or, upon continued stimulation, a large pore. P2X7R-over-expression alone is sufficient to drive microglial activation and proliferation in a process that is P2X7R pore dependent, although the biological signaling pathway through which this occurs remains unclear. Once activated, microglia are known to release a number of bioactive substances that include the proinflammatory cytokine interleukin-1β (IL-1β). Previous studies have linked P2X7R stimulation to the processing and release of IL-1β, but whether the channel or pore state of P2X7R is predominant in driving IL-1β release is unknown and is a major aim of this study. In addition, we will determine whether IL-1β has trophic effects on surrounding microglia. Electron microscopy and immunohistochemistry were used to delineate the sub-cellular localization of P2X7R and IL-1β in primary hippocampal rat cultures. FM1-43 fluorescent dye and confocal microscopy were used to quantify vesicular exocytosis from microglia expressing the pore-forming P2X7R versus a non-pore-forming point mutant, P2X7RG345Y. IL-1β in culture was quantified with an enzyme-linked immunosorbent assay (ELISA). IL-1β intracellular processing was blocked with inhibition of caspase 1 (with a synthetic peptide antagonist), and its extracellular form was neutralized with an IL-1β neutralizing antibody. Microglial activation and proliferation was quantified immunohistochemically with confocal microscopy. P2X7R and IL-1β were co-localized in lysosomes. Vesicular exocytosis was higher in microglia expressing the pore-forming P2X7R compared to those expressing the non-pore-forming mutant. There was increased IL-1β in cultures expressing the pore-forming P2X7R, and this proinflammatory cytokine was found to mediate the

  13. The effects of trophic interactions and spatial competition on algal community composition on Hawaiian coral reefs

    NARCIS (Netherlands)

    Vermeij, M.J.A.; Dailer, M.L.; Walsh, S.M.; Donovan, M.K.; Smith, C.M.

    2010-01-01

    Much of coral reef ecology has focused on how human impacts change coral reefs to macroalgal reefs. However, macroalgae may not always be a good indicator of reef decline, especially on reefs with significant sea urchin populations, as found in Kenya and Hawaii. This study tests the effects of

  14. 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.

  15. Trawling disturbance effects on the trophic ecology of two co-generic Astropectinid species

    Directory of Open Access Journals (Sweden)

    M. C. MANGANO

    2015-09-01

    Full Text Available Physical disturbance by trawling can have both negative and positive effects on populations of scavenging benthic organisms. In the present study the impact of fishing activity on feeding behaviour of the two Astropectinids, Astropecten bispinosus and A. irregularis, was assessed based on stomach contents analysis. The study was carried out along trawled seabed highlighting the positive response of the two facultative scavengers to carrion generated by trawl disturbance. Furthermore, there was greater food specialization in areas that were more heavily exploited by trawling. This specialisation could be linked to the availability of certain prey that results from the passage of fishing gears across the seabed. Interestingly, differences between the two species analysed have been highlighted in term of population dynamic, feeding rate, diet composition and diet diversity, testifying their capacity to coexist in the same fishing grounds.

  16. 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

    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...

  17. Amino Acid Isotopic Trophic Enrichment in Mesozooplankton: Is Alanine a Better Predictor of Protistan Grazer Steps?

    Science.gov (United States)

    Decima, M.; Landry, M. R.; Bradley, C. J.; Fogel, M. L.

    2016-02-01

    Food-web studies within marine environments are increasingly reliant upon results from compound-specific isotope analysis of amino acids (CSIA-AA). The approach is advantageous because it allows consumer trophic positions to be estimated without sampling the dynamic primary producers. The baseline signal in the source AA phenylalanine is preserved, and a constant enrichment in glutamic acid at each trophic step is assumed, regardless of consumer type or diet. However, a number of recent studies challenge the assumption of universal and invariant isotopic fractionation of glutamic acid for all trophic levels, as well as its specific applicability to the main grazers in the ocean: the protistan microzooplankton. We present results from both laboratory and field studies that further explore this issue. Experiments include six 2-stage chemostats, using two different microzooplankton-phytoplankton pairs and one copepod-phytoplankton pair, and one 3-stage experiment using a copepod-microzooplankton-phytoplankton chain. We confirm previous observations of negligible fractionation of glutamic acid in protistan consumers when nutrients are limiting. In contrast, a consistent trophic enrichment effect was observed for alanine, with increasing δ15N values by trophic level for both metazoan and protistan consumers. A re-analysis of published CSIA-AA data of zooplankton species show that an index using alanine and phenylalanine gives trophic level estimates closer to expected given current understanding of the linkages within microbial food webs. Our results examine the details of isotopic fractionation of alanine within defined food chains and generally support its potential use as a trophic level indicator that includes the protistan contribution to mesozooplankton diet.

  18. 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.

  19. 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

  20. 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.

  1. Dietary back-calculation using stable isotopes: can activities of enzymes involved in amino acid metabolism be used to improve estimates of trophic shifts in fish?

    Science.gov (United States)

    Gaye-Siessegger, Julia; Focken, Ulfert; Abel, Hansjörg; Becker, Klaus

    2007-06-01

    The aim of this study was (1) to assess the effects of dietary protein content and feeding level on trophic shifts of C and N isotopes (Delta delta(13)C(tissue-diet) and Delta delta(15)N(tissue-diet)) and (2) to test whether the measurement of the activities of two enzymes involved in the metabolism of amino acids could improve the accuracy of estimation of the trophic shifts of C and N isotopes. For this, 36 Nile tilapia (Oreochromis niloticus) were kept under controlled conditions for 8 weeks and fed at three different levels (2, 4 and 8 g kg(-0.8) d(-1)) with three diets differing in their protein content only (20, 29 and 39 %). For each fish, food to fish body trophic shifts of C and N isotopes were measured as well as the hepatic activities of aspartate aminotransferase (ASAT) and glutamate dehydrogenase (GDH). The feeding level affected the activities of ASAT and GDH as well as the trophic shifts of C and N isotopes significantly but the dietary protein content had no significant effect except on the specific activity of ASAT. Fish fed at the lowest level had significantly higher trophic shifts of C and N isotopes than fish fed at higher levels. The trophic shifts were significantly lower in fish with a high protein utilisation. Values of the 'goodness-of-fit' for linear regressions between enzyme activities and trophic shifts were low. Thus, activities of ASAT and GDH are not suitable for predicting estimates of trophic shifts in situations where the amount of food consumed or the dietary protein content is not known. In further studies, activities of enzymes involved in the metabolism of amino acids combined with measurements of the activities of other enzymes should be used to try and improve the accuracy of estimates of trophic shifts.

  2. Using stable isotopes to determine seabird trophic relationships

    Science.gov (United States)

    Hobson, Keith A.; Piatt, John F.; Pitocchelli, Jay

    1994-01-01

    1. The stable isotopes of nitrogen (δ15N) and carbon (δ13C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird trophic positions.2. Based on δ15N analyses, seabird trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower trophic-level organisms are more important to several seabirds than was recognized previously.3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference.4. In general, stable-isotope analysis to determine trophic level offers many advantages over conventional dietary approaches since trophic inferences are based on time-integrated estimates of assimilated and not just ingested foods, and isotopic abundance represents a continuous variable that is amenable to statistical analysis.

  3. 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.

  4. 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.

  5. 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...

  6. Effects of the flood regime on the body condition of fish of different trophic guilds in the Upper Paraná River floodplain, Brazil.

    Science.gov (United States)

    Abujanra, F; Agostinho, A A; Hahn, N S

    2009-06-01

    In this study, we evaluated the influence of various hydrological cycles on the feeding body condition of fish species of different trophic guilds in the Paraná River floodplain, as well as the impacts of upstream impoundments on fish conditions. Attributes of the river floods (duration, time of year, intensity, and variability in a given year) and the body condition, measured by the mean residuals of length-weight ratios, of the detritivorous, herbivorous, insectivorous, invertivores, omnivorous, piscivorous, and planktivorous species were evaluated. Fish were sampled during a period before (1986-1994) and after (2000-2004) the completion of filling of the Porto Primavera Reservoir, which is located upstream from the floodplain area under study. Three sub-basins in the floodplain were sampled: the Ivinheima River, which has no dams; the Paraná River, which has several dams; and the Baia River, which is influenced by the Paraná. A two-way ANOVA identified significant variations in mean body conditions for localities and for the hydrological cycles, and the interactions were also significant. The findings revealed that before the Porto Primavera Reservoir was filled, the body condition of the feeding guilds varied similarly in the three sub basins, but this pattern was not observed after filling was completed. However, in years with minor or no floods, the body condition was high, especially in the sub-basins influenced by Porto Primavera (Paraná and Baía). Pearson's and Spearman's correlations showed that most effects of the floods were unfavorable to the body condition of the guilds, except for the annual variation in water level, which aids herbivores in accessing allochthonous food resources. Detritivores were negatively affected by all flood attributes. A correlation between the relative stomach weight (mean residual of the ratio of total and stomach weights) and the body condition demonstrated the poor relationship between the amount of food intake and

  7. Trophic strategies of unicellular plankton

    DEFF Research Database (Denmark)

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

    2017-01-01

    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. To this......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...... 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...

  8. Demographic and Phenotypic Effects of Human Mediated Trophic Subsidy on a Large Australian Lizard (Varanus varius): Meal Ticket or Last Supper?

    OpenAIRE

    Jessop, Tim S.; Smissen, Peter; Scheelings, Franciscus; Dempster, Tim

    2012-01-01

    Humans are increasingly subsidizing and altering natural food webs via changes to nutrient cycling and productivity. Where human trophic subsidies are concentrated and persistent within natural environments, their consumption could have complex consequences for wild animals through altering habitat preferences, phenotypes and fitness attributes that influence population dynamics. Human trophic subsidies conceptually create both costs and benefits for animals that receive increased calorific a...

  9. Breaking out of the comfort zone: El Niño-Southern Oscillation as a driver of trophic flows in a benthic consumer of the Humboldt Current ecosystem.

    Science.gov (United States)

    Riascos, José M; Solís, Marco A; Pacheco, Aldo S; Ballesteros, Manuel

    2017-06-28

    The trophic flow of a species is considered a characteristic trait reflecting its trophic position and function in the ecosystem and its interaction with the environment. However, climate patterns are changing and we ignore how patterns of trophic flow are being affected. In the Humboldt Current ecosystem, arguably one of the most productive marine systems, El Niño-Southern Oscillation is the main source of interannual and longer-term variability. To assess the effect of this variability on trophic flow we built a 16-year series of mass-specific somatic production rate (P/B) of the Peruvian scallop ( Argopecten purpuratus ), a species belonging to a former tropical fauna that thrived in this cold ecosystem. A strong increase of the P/B ratio of this species was observed during nutrient-poor, warmer water conditions typical of El Niño, owing to the massive recruitment of fast-growing juvenile scallops. Trophic ecology theory predicts that when primary production is nutrient limited, the trophic flow of organisms occupying low trophic levels should be constrained (bottom-up control). For former tropical fauna thriving in cold, productive upwelling coastal zones, a short time of low food conditions but warm waters during El Niño could be sufficient to waken their ancestral biological features and display massive proliferations. © 2017 The Author(s).

  10. Effects of wind forcing on the trophic conditions, zooplankton biomass and krill biochemical composition in the Gulf of Tehuantepec

    Science.gov (United States)

    Färber-Lorda, Jaime; Lavín, M. F.; Guerrero-Ruiz, M. A.

    2004-03-01

    The trophic conditions, the zooplankton biomass and the krill biochemical composition in the Gulf of Tehuantepec were studied in relation to spatial and temporal changes in the physical environment, caused by Norte winds. These winds, which occur mostly from October to March, are intermittent, strong wind jets that blow offshore and normal to the coast at the head of the Gulf of Tehuantepec. Ekman pumping raises the thermocline in the east and lowers it in the west of the jet axis; in the central region of the gulf, vertical mixing brings cool, nutrient-rich waters to the surface, enhancing biological productivity. Data from a January 1989 survey show that mean zooplankton biomass was highest in the central region, but there was no significant difference between the three regions (east, central and west). Among euphausiids, Euphausia lamelligera was the dominant species, with 92%. Mean particulate protein, lipids and particulate organic matter (POM = protein + carbohydrates + lipids) did not show significant differences among the three regions; however, mean particulate carbohydrates were significantly different. For the entire area, low but significant linear regressions between (ArcSin) lipids in euphausiids and lipids in POM, and between POM and (ArcSin) lipids in euphausiids were obtained. Better regressions between zooplankton biomass and POM and other variables were obtained when stations were analyzed by hydrographic regions. When data were grouped into those taken before and after a strong Norte (Leg I and Leg II, respectively), a significant positive regression was obtained between (ArcSin) krill lipids and POM for Leg I; but for Leg II, the slope, although not statistically significant, was negative. POM is apparently utilized during Leg II, but the response in the lipid content of the animals is evident only after some time has passed (during Leg I), when the animals had assimilated the food surplus.

  11. 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.

  12. Impacts of intensive logging on the trophic organisation of ant communities in a biodiversity hotspot.

    Directory of Open Access Journals (Sweden)

    Paul Woodcock

    Full Text Available Trophic organisation defines the flow of energy through ecosystems and is a key component of community structure. Widespread and intensifying anthropogenic disturbance threatens to disrupt trophic organisation by altering species composition and relative abundances and by driving shifts in the trophic ecology of species that persist in disturbed ecosystems. We examined how intensive disturbance caused by selective logging affects trophic organisation in the biodiversity hotspot of Sabah, Borneo. Using stable nitrogen isotopes, we quantified the positions in the food web of 159 leaf-litter ant species in unlogged and logged rainforest and tested four predictions: (i there is a negative relationship between the trophic position of a species in unlogged forest and its change in abundance following logging, (ii the trophic positions of species are altered by logging, (iii disturbance alters the frequency distribution of trophic positions within the ant assemblage, and (iv disturbance reduces food chain length. We found that ant abundance was 30% lower in logged forest than in unlogged forest but changes in abundance of individual species were not related to trophic position, providing no support for prediction (i. However, trophic positions of individual species were significantly higher in logged forest, supporting prediction (ii. Consequently, the frequency distribution of trophic positions differed significantly between unlogged and logged forest, supporting prediction (iii, and food chains were 0.2 trophic levels longer in logged forest, the opposite of prediction (iv. Our results demonstrate that disturbance can alter trophic organisation even without trophically-biased changes in community composition. Nonetheless, the absence of any reduction in food chain length in logged forest suggests that species-rich arthropod food webs do not experience trophic downgrading or a related collapse in trophic organisation despite the disturbance caused by

  13. Behavioural and physiological effects of the trophically transmitted cestode parasite, Cyathocephalus truncatus, on its intermediate host, Gammarus pulex.

    Science.gov (United States)

    Franceschi, N; Rigaud, T; Moret, Y; Hervant, F; Bollache, L

    2007-11-01

    Some parasites with complex life-cycles are able to manipulate the behaviour of their intermediate hosts in a way that increases their transmission to the next host. Gammarids infected by the tapeworm Cyathocephalus truncatus (Cestoda: Spathebothriidea) are known to be more predated by fish than uninfected ones, but potential behavioural manipulation by the parasite has never been investigated. In this study, we tested the hypothesis that C. truncatus is able to manipulate the behaviour of one of its intermediate hosts, Gammarus pulex (Crustacea: Amphipoda). To assess if any behavioural change was linked to other phenotypic alterations, we also measured the immunity of infected and uninfected individuals and investigated the pathogenic effects of the parasite. Infected gammarids were significantly less photophobic than uninfected ones, but no effect of infection on the level of immune defence was found. The results on survival, swimming activity and oxygen consumption suggest that the parasite also has various pathogenic effects. However, the alteration in host phototaxis was not correlated to some of these pathogenic effects. Therefore, we propose that the modification in host reaction to light is a behavioural manipulation, explaining the previously observed increase of gammarid predation rate.

  14. 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.

  15. Trophic impact of Atlantic bluefin tuna migrations in the North Sea

    DEFF Research Database (Denmark)

    Mariani, Patrizio; Andersen, Ken Haste; Lindegren, Martin

    2017-01-01

    spectrum model to analyse the trophic impact of the returning tuna on the entire fish community, under scenarios with varying levels of tuna consumption and fishing mortality on the prey. We show that with high level of prey fishing mortality in the North Sea, the effect of a tuna re-colonization results...... and the stability of the fish community. The impact of a migrating top-predator is investigated here for Atlantic bluefin tuna in the North Sea. Bluefin tuna has been absent from the region for half-century, but recent years have seen recovery of migrations and a return of bluefin tuna in the area. We use a size...... in only limited trophic cascades. However, high tuna consumption or changes in fishing mortality may result in a sudden recruitment failure of small-pelagic fish due to cascading effects on the fish community. In present-day conditions, the level of tuna consumption that triggers recruitment failure...

  16. 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.

  17. 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

    2018-02-01

    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.

  18. Permissive or Trophic Enteral Nutrition and Full Enteral Nutrition Had Similar Effects on Clinical Outcomes in Intensive Care: A Systematic Review of Randomized Clinical Trials.

    Science.gov (United States)

    Silva, Camila F A; de Vasconcelos, Simone G; da Silva, Thales A; Silva, Flávia M

    2018-01-26

    The aim of this study was to systematically review the effect of permissive underfeeding/trophic feeding on the clinical outcomes of critically ill patients. A systematic review of randomized clinical trials to evaluate the mortality, length of stay, and mechanical ventilation duration in patients randomized to either hypocaloric or full-energy enteral nutrition was performed. Data sources included PubMed and Scopus and the reference lists of the articles retrieved. Two independent reviewers participated in all phases of this systematic review as proposed by the Cochrane Handbook, and the review was reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A total of 7 randomized clinical trials that included a total of 1,717 patients were reviewed. Intensive care unit length of stay and mechanical ventilation duration were not statistically different between the intervention and control groups in all randomized clinical trials, and mortality rate was also not different between the groups. In conclusion, hypocaloric enteral nutrition had no significantly different effects on morbidity and mortality in critically ill patients when compared with full-energy nutrition. It is still necessary to determine the safety of this intervention in this group of patients, the optimal amount of energy provided, and the duration of this therapy. © 2018 American Society for Parenteral and Enteral Nutrition.

  19. 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

  20. Trophic Effects and Regenerative Potential of Mobilized Mesenchymal Stem Cells From Bone Marrow and Adipose Tissue as Alternative Cell Sources for Pulp/Dentin Regeneration.

    Science.gov (United States)

    Murakami, Masashi; Hayashi, Yuki; Iohara, Koichiro; Osako, Yohei; Hirose, Yujiro; Nakashima, Misako

    2015-01-01

    Dental pulp stem cell (DPSC) subsets mobilized by granulocyte-colony-stimulating factor (G-CSF) are safe and efficacious for complete pulp regeneration. The supply of autologous pulp tissue, however, is very limited in the aged. Therefore, alternative sources of mesenchymal stem/progenitor cells (MSCs) are needed for the cell therapy. In this study, DPSCs, bone marrow (BM), and adipose tissue (AD)-derived stem cells of the same individual dog were isolated using G-CSF-induced mobilization (MDPSCs, MBMSCs, and MADSCs). The positive rates of CXCR4 and G-CSFR in MDPSCs were similar to MADSCs and were significantly higher than those in MBMSCs. Trophic effects of MDPSCs on angiogenesis, neurite extension, migration, and antiapoptosis were higher than those of MBMSCs and MADSCs. Pulp-like loose connective tissues were regenerated in all three MSC transplantations. Significantly higher volume of regenerated pulp and higher density of vascularization and innervation were observed in response to MDPSCs compared to MBMSC and MADSC transplantation. Collagenous matrix containing dentin sialophosphoprotein (DSPP)-positive odontoblast-like cells was the highest in MBMSCs and significantly higher in MADSCs compared to MDPSCs. MBMSCs and MADSCs, therefore, have potential for pulp regeneration, although the volume of regenerated pulp tissue, angiogenesis, and reinnervation, were less. Thus, in conclusion, an alternative cell source for dental pulp/dentin regeneration are stem cells from BM and AD tissue.

  1. 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.

  2. A Bio-economic Study of the Trophic Structure of the Omani Fish Catch.

    Science.gov (United States)

    Abd El-Rahman, Medhat Abd El-Barr

    2014-08-01

    The present study was conducted to obtain estimates of certain biological and economic indices of the trophic structure of the Omani landed fish catch, namely, the mean trophic level (MTL), the fishing-in-balance (FiB) index and the relative price index (RPI). The MTL generally decreased from 1995 to 2010, indicating a fishing-down of the marine trophic web. The FiB index increased, indicating an imbalance in the fisheries. An economic index, the RPI, decreased from 1994 to 2007, indicating that the values of lower trophic level (TL) species increased relative to those of higher TL species.

  3. 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.

  4. 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.

  5. 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.

  6. Mechanisms Responsible for the Trophic Effect of Beta-Adrenoceptors on the Ito Current Density in Type 1 Diabetic Rat Cardiomyocytes

    Directory of Open Access Journals (Sweden)

    Raúl Setién

    2013-01-01

    Full Text Available Background/Aims: In diabetic ventricular myocytes, transient outward potassium current (Ito amplitude is severely reduced because of the impaired catecholamine release that characterizes diabetic autonomic neuropathy. Sympathetic nervous system exhibits a trophic effect on Ito since incubation of myocytes with noradrenaline restores current amplitude via beta-adrenoceptor (βAR stimulation. Here, we investigate the intracellular signalling pathway though which incubation of diabetic cardiomyocytes with the βAR agonist isoproterenol recovers Ito amplitude to normal values. Methods: Experiments were performed in ventricular myocytes isolated from streptozotocin-diabetic rats. Ito current was recorded by using the patch-clamp technique. Kv4 channel expression was determined by immunofluorescence. Protein-protein interaction was determined by coimmunoprecipitation. Results: Stimulation of βAR activates first a Gαs protein, adenylyl cyclase and Protein Kinase A. PKA-phosphorylated receptor then switches to the Gαi protein. This leads to the activation of the βAR-Kinase-1 and further receptor phosphorylation and arrestin dependent internalization. The internalized receptor-arrestin complex recruits and activates cSrc and the MAPK cascade, where Ras, c-Raf1 and finally ERK1/2 mediate the increase in Kv4.2 and Kv4.3 protein abundance in the plasma membrane. Conclusion: β2AR stimulation activates a Gαs and Gαi protein dependent pathway where the ERK1/2 modulates the Ito current amplitude and the density of the Kv4.2 and Kv4.2 channels in the plasma membrane upon sympathetic stimulation in diabetic heart.

  7. Crayfish as trophic agents: Effect of Austropotamobius torrentium on zoobenthos structure and function in small forest streams

    OpenAIRE

    Weinländer M.; Füreder L.

    2011-01-01

    Crayfish are among the largest and most threatened invertebrates in freshwater habitats. Due to their size, behaviour and feeding activity they may affect structure and function of aquatic ecosystems and their organisms. Despite their importance in many freshwaters and available information on their ecology for several species little is known about the European crayfish Austropotamobius torrentium. In order to evaluate the potential effects of indigenous crayfish presence on the structural an...

  8. Os grupos tróficos em Coleoptera The trophic groups in Coleoptera

    Directory of Open Access Journals (Sweden)

    Renato C. Marinoni

    2001-03-01

    Full Text Available The beetles are a useful group for studies on trophic structure of communities, mainly in forested areas. These kind of studies are based on food habits of species groups. The different terms applied to nomminated these groups (trophic category, ecologic group, trophic group, guild, trophic guild are discussed. The term trophic group, a natural unity, is proposed to form a group of species with the same food habits, not considering the trophic level. The guild, an artificial unity, is recognized as an important tool to group organisms group that use the same resources as defined by the investigator (Hawkins & MacMaiion, 1989; Simberloff & Dayan 1991; Wilson 1999. The known alimentary habits of Coleoptera are classified in five trophic groups - herbivores, algivores, fungívores, detrivores and carnivores. Within each trophic group, subgroups are recognized. The subgroup are in a lower hierarchic level and are defined by morphological (herbivores, taxonomic (fungivores atributes of the food, by the food origin (detrivores and by the way that the food is obtained (carnivores. A food resource diagram showing connections among the trophic groups, based on consumer-consumed (predator-prey relations, is presented.

  9. Effect of pollution on diversity of marine gastropods and its role in trophic structure at Nasese Shore, Suva, Fiji Islands

    Directory of Open Access Journals (Sweden)

    Dissanayake Mudiyanselage Suratissa

    2017-06-01

    Full Text Available Ocean supplies a significant amount of food to human population. However, marine ecosystem is under a threat due to the increasing marine pollution. Fiji Islands, located in South Pacific sea, are experiencing such a threat. Therefore, this study aims to determine the effects of pollution on the diversity of marine gastropods in Nasese Shore, Suva, Fiji Islands. A detailed opportunistic survey was conducted; 85 species of marine gastropods molluscas were recorded belonging to 29 families in four different habitats (Habitat 1, Habitat 2, Habitat 3 and Habitat 4 at Nasese Shore during April–September 2014. Compared with Habitat 4, all three other habitats were polluted by frequently added sewages and domestic effluents via artificial and natural creeks to the coastal area. Therefore, diversity and abundance of the gastropods were significantly lower in those three habitats. Furthermore, a higher human consumption rate for some of the gastropods was observed.

  10. 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.

  11. Longer Food Chains in Pelagic Ecosystems: Trophic Energetics of Animal Body Size and Metabolic Efficiency.

    Science.gov (United States)

    McGarvey, Richard; Dowling, Natalie; Cohen, Joel E

    2016-07-01

    Factors constraining the structure of food webs can be investigated by comparing classes of ecosystems. We find that pelagic ecosystems, those based on one-celled primary producers, have longer food chains than terrestrial ecosystems. Yet pelagic ecosystems have lower primary productivity, contrary to the hypothesis that greater energy flows permit higher trophic levels. We hypothesize that longer food chain length in pelagic ecosystems, compared with terrestrial ecosystems, is associated with smaller pelagic animal body size permitting more rapid trophic energy transfer. Assuming negative allometric dependence of biomass production rate on body mass at each trophic level, the lowest three pelagic animal trophic levels are estimated to add biomass more rapidly than their terrestrial counterparts by factors of 12, 4.8, and 2.6. Pelagic animals consequently transport primary production to a fifth trophic level 50-190 times more rapidly than animals in terrestrial webs. This difference overcomes the approximately fivefold slower pelagic basal productivity, energetically explaining longer pelagic food chains. In addition, ectotherms, dominant at lower pelagic animal trophic levels, have high metabolic efficiency, also favoring higher rates of trophic energy transfer in pelagic ecosystems. These two animal trophic flow mechanisms imply longer pelagic food chains, reestablishing an important role for energetics in food web structure.

  12. Are trophic and diversity indices based on macrophyte communities pertinent tools to monitor water quality?

    Science.gov (United States)

    Thiebaut, Gabrielle; Guérold, François; Muller, Serge

    2002-08-01

    Diversity and trophic indices based on macrophyte communities were calculated to test their pertinence to monitoring water quality in the Northern Vosges (NE of France). Highly significant correlations were found between the four tested chemical variables (bicarbonate, calcium, phosphorus and ammonium nitrogen) and trophic indices and between them and abundance and richness. Trophic indices and McIntosh's index appeared to be more effective in predicting water quality than diversity indices. Diversity indices do not necessarily provide any direct information on the quality or degree of degradation of the environment from which the sample was taken, whereas trophic indices do.

  13. Deviation from strict homeostasis across multiple trophic levels in an invertebrate consumer assemblage exposed to high chronic phosphorus enrichment in a Neotropical stream.

    Science.gov (United States)

    Small, Gaston E; Pringle, Catherine M

    2010-03-01

    A central tenet of ecological stoichiometry is that consumer elemental composition is relatively independent of food resource nutrient content. Although the P content of some invertebrate consumer taxa can increase as a consequence of P-enriched food resources, little is known about how ecosystem nutrient loading can affect the elemental composition of entire consumer assemblages. Here we examine the potential for P enrichment across invertebrate consumer assemblages in response to chronic high P loading. We measured elemental ratios in invertebrate consumers and basal food resources in a series of streams in lowland Costa Rica that range widely in P levels (2-135 microg l(-1) soluble reactive P). Streams with high P levels receive natural long-term (over millennia) inputs of solute-rich groundwater while low-P streams do not receive these solute-rich groundwater inputs. P content of leaf litter and epilithon increased fourfold across the natural P gradient, exceeding basal resource P content values reported in the literature from other nutrient-rich streams. Invertebrate consumers from the high-P study stream were elevated twofold in P content across multiple taxonomic and functional feeding groups, including predators. Our results strongly support the hypothesis that elevated P content in consumers feeding on P-enriched food resources is a consequence of deviation from strict homeostasis. In contrast to prior studies, we found that between-stream variation in P content of a given taxon greatly exceeded within-stream variation among different taxa, suggesting that environment may be as important as phylogeny in controlling consumer stoichiometry. Relaxing the assumption of strict homeostasis presents challenges and opportunities for advancing our understanding of how nutrient limitation affects consumer growth. Moreover, our findings may provide a window into the future of how chronic anthropogenic nutrient loading can alter stoichiometric relationships in food

  14. 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.

  15. Comparing trophic flows in the southern Benguela to those in other ...

    African Journals Online (AJOL)

    A balanced trophic flow model of the southern Benguela ecosystem is presented, averaging the period 1980–1989 and emphasizing upper trophic levels. The model is based largely on studies conducted within the framework of the Benguela Ecology Programme and updates the results of an expert workshop held in Cape ...

  16. Use of Stable Carbon and Nitrogen Isotopes for Trophic Levels Evaluation and Food Webs Reconstruction: The Bay of Biscay Case Study

    International Nuclear Information System (INIS)

    Chouvelon, Tiphaine; Spitz, J.; Caurant, F.; Mendez Fernandez, P.; Bustamante, P.

    2011-01-01

    The Bay of Biscay is a very large bay opened on the North-East Atlantic Ocean. The continental shelf covers over 220 000 km 2 . The hydrological structure is influenced by 2 main rivers plumes (Loire and Gironde) and a continental slope indented by numerous canyons. The Bay of Biscay supports both numerous important fisheries and a rich fauna including many protected species (e.g., marine mammals). The management of this ecosystem subjected to numerous anthropogenic impacts notably depends on the good understanding of its food webs' structure. Within each major group of taxa, spatial groups displayed significantly different δ 13 C and δ 15 N values (KW tests, all p 13 C and δ 15 N values decreased from near-shore organisms to deep-sea or oceanic organisms. These results highlighted the existence of several food webs with distinct baseline signatures in the Bay of Biscay. Differences in δ 15 N values in particular are linked to processes occurring at the Dissolved Inorganic Nitrogen (DIN) level, and to nutrients and particulate organic matter available for primary production in general. Therefore, the contrasted hydrological landscapes from the Bay of Biscay probably impact signatures of the primary producers in the different areas of the Bay.

  17. 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.

  18. 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

  19. 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

  20. Ant-mediated ecosystem processes are driven by trophic community structure but mainly by the environment.

    Science.gov (United States)

    Salas-Lopez, Alex; Mickal, Houadria; Menzel, Florian; Orivel, Jérôme

    2017-01-01

    The diversity and functional identity of organisms are known to be relevant to the maintenance of ecosystem processes but can be variable in different environments. Particularly, it is uncertain whether ecosystem processes are driven by complementary effects or by dominant groups of species. We investigated how community structure (i.e., the diversity and relative abundance of biological entities) explains the community-level contribution of Neotropical ant communities to different ecosystem processes in different environments. Ants were attracted with food resources representing six ant-mediated ecosystem processes in four environments: ground and vegetation strata in cropland and forest habitats. The exploitation frequencies of the baits were used to calculate the taxonomic and trophic structures of ant communities and their contribution to ecosystem processes considered individually or in combination (i.e., multifunctionality). We then investigated whether community structure variables could predict ecosystem processes and whether such relationships were affected by the environment. We found that forests presented a greater biodiversity and trophic complementarity and lower dominance than croplands, but this did not affect ecosystem processes. In contrast, trophic complementarity was greater on the ground than on vegetation and was followed by greater resource exploitation levels. Although ant participation in ecosystem processes can be predicted by means of trophic-based indices, we found that variations in community structure and performance in ecosystem processes were best explained by environment. We conclude that determining the extent to which the dominance and complementarity of communities affect ecosystem processes in different environments requires a better understanding of resource availability to different species.

  1. Response of rotifer functional groups to changing trophic state and crustacean community

    Directory of Open Access Journals (Sweden)

    Marina MANCA

    2011-08-01

    Full Text Available Information based on taxon-based indices is species-specific while information gained from function-based research can give a comprehensive view of ecosystem processes. We applied the guild-ratio, an index based on the proportion of functional groups of rotifers (i.e. microphagous and raptorial species, on a long-term data set of Lago Maggiore. By applying seasonal trend decomposition based on smoothing techniques and non-metrical multidimensional scaling, we assessed the response of rotifer functional groups to changes in trophic state and climate. While the taxon-based indices showed smooth changes, the function-based index showed a dramatic shift from a raptorial to a microphagous dominance, with a back-shift to raptorial dominance starting in 2000. The seasonal peak of microphagous and raptorial dry weight was clearly separated in the pre-eutrophication period. When mesotrophic conditions prevailed both peaks overlapped, only to be separated again with re-oligotrophication. We attributed these alterations of rotifer functional groups to changes in competition with crustacean zooplankton and to decreased phytoplankton algal abundance and size while altered seasonality in functional groups could be related to inter-group competition for food. We hypothesise that the effects of trophic state (i.e. altered phytoplankton and climate (i.e. altered cladoceran community were transferred across trophic levels to rotifer functional groups. Our study highlights that functional groups are valid instruments for illustrating unifying principles in ecology through a better understanding of ecosystem processes and the interrelationship between trophic levels.

  2. 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

  3. 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

  4. Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research.

    Science.gov (United States)

    Svenning, Jens-Christian; Pedersen, Pil B M; Donlan, C Josh; Ejrnæs, Rasmus; Faurby, Søren; Galetti, Mauro; Hansen, Dennis M; Sandel, Brody; Sandom, Christopher J; Terborgh, John W; Vera, Frans W M

    2016-01-26

    Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human-wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology.

  5. Early herbivore alert matters: plant-mediated effects of egg deposition on higher trophic levels benefit plant fitness

    NARCIS (Netherlands)

    Pashalidou, F.G.; Frago, E.; Griese, E.; Poelman, E.H.; Loon, van J.J.A.; Dicke, M.; Fatouros, N.E.

    2015-01-01

    Induction of plant defences, specifically in response to herbivore attack, can save costs that would otherwise be needed to maintain defences even in the absence of herbivores. However, plants may suffer considerable damage during the time required to mount these defences against an attacker. This

  6. Effects of invasion at two trophic levels on diet, body condition, and population size structure of Hawaiian red shrimp

    Science.gov (United States)

    Bruce D. Dudley; Richard A. MacKenzie; Troy S. Sakihara; Michael H. Riney; Rebecca Ostertag

    2017-01-01

    We examined the degree to which invasion by non-native, nitrogen (N)-fixing riparian trees and poeciliid fish alters diet of a common grazer/detritivore in brackish ponds on the dry coast of Hawai‛i Island. Because this shrimp, Halocaridina rubra (ʻōpaeʻula), displays a preference for autotrophic components of epilithon, we hypothesized...

  7. Effect of Lake Trophic Status and Rooted Macrophytes on Community Composition and Abundance of Ammonia-oxidizing Prokaryotes in Freshwater Sediments

    DEFF Research Database (Denmark)

    Herrmann, Martina; Saunders, Aaron Marc; Schramm, Andreas

    2009-01-01

    /N ratios. AOA communities could be grouped according to lake trophic status and pH; plant species-specific communities were not detected, and no grouping was apparent for AOB communities. Relative abundance, determined by quantitative PCR targeting amoA, was always low for AOB (...) and slightly higher for AOA in unvegetated sediment and AOA in association with M. alterniflorum (0.01 to 2%), while AOA accounted for up to 5% in the rhizospheres of L. uniflora and J. bulbosus. These results indicate that (i) AOA are at least as numerous as AOB in freshwater sediments, (ii) aquatic...

  8. 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.

  9. 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.

  10. Trophic Interactions in Louisiana Salt Marshes: Combining Stomach Content, Stable Isotope, and Fatty Acid Approaches

    Science.gov (United States)

    Lopez-Duarte, P. C.; Able, K.; Fodrie, J.; McCann, M. J.; Melara, S.; Noji, C.; Olin, J.; Pincin, J.; Plank, K.; Polito, M. J.; Jensen, O.

    2016-02-01

    Multiple studies conducted over five years since the 2010 Macondo oil spill in the Gulf of Mexico indicate that oil impacts vary widely among taxonomic groups. For instance, fishes inhabiting the marsh surface show no clear differences in either community composition or population characteristics between oiled and unoiled sites, despite clear evidence of physiological impacts on individual fish. In contrast, marsh insects and spiders are sensitive to the effects of hydrocarbons. Both insects and spiders are components of the marsh food web and represent an important trophic link between marsh plants and higher trophic levels. Because differences in oil impacts throughout the marsh food web have the potential to significantly alter food webs and energy flow pathways and reduce food web resilience, our goal is to quantify differences in marsh food webs between oiled and unoiled sites to test the hypothesis that oiling has resulted in simpler and less resilient food webs. Diets and food web connections were quantified through a combination of stomach content, stable isotope, and fatty acid analysis. The combination of these three techniques provides a more robust approach to quantifying trophic relationships than any of these methods alone. Stomach content analysis provides a detailed snapshot of diets, while fatty acid and stable isotopes reflect diets averaged over weeks to months. Initial results focus on samples collected in May 2015 from a range of terrestrial and aquatic consumer species, including insects, mollusks, crustaceans, and piscivorous fishes.

  11. 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.

  12. 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.

  13. 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.

  14. Effects of clonal variation on growth, metabolism, and productivity in response to trophic factor stimulation: a study of Chinese hamster ovary cells producing a recombinant monoclonal antibody.

    Science.gov (United States)

    Dahodwala, Hussain; Nowey, Mark; Mitina, Tatyana; Sharfstein, Susan T

    2012-01-01

    The growth, metabolism, and productivity of five Chinese hamster ovary (CHO) clones were explored in response to stimulation with insulin (5 mg/L) and LONG(®)R(3)IGF-I (20 μg/L or 100 μg/L). All five clones were derived from the same parental CHO cell line (DG44) and produced the same recombinant monoclonal antibody, with varying specific productivities. There was no uniform response among the clones to stimulation with the different trophic factors. One of the high productivity clones (clone D) exhibited significantly better growth in response to LONG(®)R(3)IGF-I; whereas the other clones showed equivalent or slightly better growth in the presence of insulin. Three out of the five clones had higher specific productivities in the presence of insulin (although not statistically significant); one was invariant, and the final clone exhibited slightly higher specific productivity in the presence of LONG(®)R(3)IGF-I. Total product titers exhibited moderate variation between culture conditions, again with neither trophic factor being clearly superior. Overall product titers were affected by variations in both integrated viable cell density and specific productivity. Nutrient uptake and metabolite generation patterns varied strongly between clones and much less with culture conditions. These results point to the need for careful clonal analysis when selecting clones, particularly for platform processes where media and culture conditions are predetermined.

  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. 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.

  17. Evaluation of European diatom trophic indices.

    NARCIS (Netherlands)

    Lototskaya, A.A.; Verdonschot, P.F.M.; Coste, M.; Vijver, van de B.

    2011-01-01

    Freshwater diatoms are considered to be reliable indicators of the trophic status of rivers and lakes. In the past 30 years, a number of indicator indices have been developed and used for the assessment of trophic conditions all over Europe. It is however still not clear whether the ecologic

  18. Ocean Acidification Affects the Phyto-Zoo Plankton Trophic Transfer Efficiency.

    Directory of Open Access Journals (Sweden)

    Gemma Cripps

    Full Text Available The critical role played by copepods in ocean ecology and biogeochemistry warrants an understanding of how these animals may respond to ocean acidification (OA. Whilst an appreciation of the potential direct effects of OA, due to elevated pCO2, on copepods is improving, little is known about the indirect impacts acting via bottom-up (food quality effects. We assessed, for the first time, the chronic effects of direct and/or indirect exposures to elevated pCO2 on the behaviour, vital rates, chemical and biochemical stoichiometry of the calanoid copepod Acartia tonsa. Bottom-up effects of elevated pCO2 caused species-specific biochemical changes to the phytoplanktonic feed, which adversely affected copepod population structure and decreased recruitment by 30%. The direct impact of elevated pCO2 caused gender-specific respiratory responses in A.tonsa adults, stimulating an enhanced respiration rate in males (> 2-fold, and a suppressed respiratory response in females when coupled with indirect elevated pCO2 exposures. Under the combined indirect+direct exposure, carbon trophic transfer efficiency from phytoplankton-to-zooplankton declined to < 50% of control populations, with a commensurate decrease in recruitment. For the first time an explicit role was demonstrated for biochemical stoichiometry in shaping copepod trophic dynamics. The altered biochemical composition of the CO2-exposed prey affected the biochemical stoichiometry of the copepods, which could have ramifications for production of higher tropic levels, notably fisheries. Our work indicates that the control of phytoplankton and the support of higher trophic levels involving copepods have clear potential to be adversely affected under future OA scenarios.

  19. 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.

  20. A Bio-economic Study of the Trophic Structure of the Omani Fish Catch

    OpenAIRE

    Abd El-Rahman, Medhat Abd El-Barr

    2014-01-01

    The present study was conducted to obtain estimates of certain biological and economic indices of the trophic structure of the Omani landed fish catch, namely, the mean trophic level (MTL), the fishing-in-balance (FiB) index and the relative price index (RPI). The MTL generally decreased from 1995 to 2010, indicating a fishing-down of the marine trophic web. The FiB index increased, indicating an imbalance in the fisheries. An economic index, the RPI, decreased from 1994 to 2007, indicating t...

  1. 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. Adaptive...... fitness-seeking behaviour of the intra-guild prey has a stabilizing effect on the tri-trophic food-web dynamics provided that (i) a finite optimal foraging effort exists and (ii) the trophic transfer efficiency from resource to predator via the intra-guild prey is greater than that from the resource...

  2. Mammal-induced trophic cascades in invertebrate food webs are modulated by grazing intensity in subalpine grassland.

    Science.gov (United States)

    Vandegehuchte, Martijn L; Schütz, Martin; de Schaetzen, Frederic; Risch, Anita C

    2017-10-01

    Even though mammalian herbivores can exert strong indirect effects on other animals by altering the vegetation, the study of trophic cascades retains a focus on apex predators and their top-down forces. Bottom-up trophic interaction chains induced by mammalian herbivores, particularly in invertebrate food webs, remain largely unexplored. We tested whether effects of mammalian herbivores on the vegetation ricochet back up several trophic levels of the invertebrate food web. We further tested two alternative hypotheses: the strength of herbivore-induced indirect interactions either increases with plant productivity because of a concurrent higher grazing intensity, or it decreases because of a higher plant tolerance to grazing. We progressively excluded large, medium and small herbivorous mammals from replicated plots of 6 m 2 in productive, intensively grazed short-grass vegetation and less productive, less intensively grazed tall-grass vegetation of subalpine grasslands. We measured vegetation quantity, quality, structure and composition, and determined the abundance of invertebrate herbivores, detritivores, omnivores and predators. We used structural equation modelling to test vegetation-mediated cascading effects of the different mammalian herbivores across different trophic groups of invertebrates. In the short-grass vegetation, mammals caused changes in vegetation quantity and thickness. These changes directly affected detritivorous and predatory invertebrate abundance, yet indirectly affected predatory and omnivorous invertebrates through a bottom-up trophic cascade via changes in herbivorous invertebrate abundance. In the tall-grass vegetation, mammal-induced changes in vegetation quality and composition affected detritivorous invertebrates and in turn omnivorous invertebrates, but these cascading effects were weaker than those in the short-grass vegetation. Smaller mammals were at least as important as large mammals in structuring the invertebrate food web

  3. Ocean acidification increases the accumulation of toxic phenolic compounds across trophic levels, supplement to: Jin, Peng; Wang, Tifeng; Liu, Nana; Dupont, Sam; Beardall, John; Boyd, Philip W; Riebesell, Ulf; Gao, Kunshan (2015): Ocean acidification increases the accumulation of toxic phenolic compounds across trophic levels. Nature Communications, 6, 8714

    KAUST Repository

    Jin, Peng

    2016-01-01

    Increasing atmospheric CO2 concentrations are causing ocean acidification (OA), altering carbonate chemistry with consequences for marine organisms. Here we show that OA increases by 46-212% the production of phenolic compounds in phytoplankton grown under the elevated CO2 concentrations projected for the end of this century, compared with the ambient CO2 level. At the same time, mitochondrial respiration rate is enhanced under elevated CO2 concentrations by 130-160% in a single species or mixed phytoplankton assemblage. When fed with phytoplankton cells grown under OA, zooplankton assemblages have significantly higher phenolic compound content, by about 28-48%. The functional consequences of the increased accumulation of toxic phenolic compounds in primary and secondary producers have the potential to have profound consequences for marine ecosystem and seafood quality, with the possibility that fishery industries could be influenced as a result of progressive ocean changes.

  4. Trophic state index of a lake system using IRS (P6-LISS III) satellite imagery.

    Science.gov (United States)

    Sheela, A M; Letha, J; Joseph, Sabu; Ramachandran, K K; Sanalkumar, S P

    2011-06-01

    Water pollution has now become a major threat to the existence of living beings and water quality monitoring is an effective step towards the restoration of water quality. Lakes are versatile ecosystems and their eutrophication is a serious problem. Carlson Trophic State Index (CTSI) provides an insight into the trophic condition of a lake. CTSI has been modified for the study area and is used in this study. Satellite imagery analysis now plays a prominent role in the quick assessment of water quality in a vast area. This study is an attempt to assess the trophic state index based on secchi disk depth and chlorophyll a of a lake system (Akkulam-Veli lake, Kerala, India) using Indian Remote Sensing (IRS) P6 LISS III imagery. Field data were collected on the date of the overpass of the satellite. Multiple regression equation is found to yield superior results than the simple regression equations using spectral ratios and radiance from the individual bands, for the prediction of trophic state index from satellite imagery. The trophic state index based on secchi disk depth, derived from the satellite imagery, provides an accurate prediction of the trophic status of the lake. IRS P6-LISS III imagery can be effectively used for the assessment of the trophic condition of a lake system.

  5. Land-ocean gradient in haline stratification and its effects on plankton dynamics and trophic carbon fluxes in Chilean Patagonian fjords (47-50°S)

    Science.gov (United States)

    González, H. E.; Castro, L. R.; Daneri, G.; Iriarte, J. L.; Silva, N.; Tapia, F.; Teca, E.; Vargas, C. A.

    2013-12-01

    Patagonian fjord systems, and in particular the fjords and channels associated with the Baker/Pascua Rivers, are currently under conspicuous natural and anthropogenic perturbations. These systems display very high variability, where limnetic and oceanic features overlap generating strong vertical and horizontal physicochemical gradients. The CIMAR 14-Fiordos cruise was conducted in the Chilean fjords located between 47° and 50°S during the spring (October-November) of 2008. The main objectives were to study vertical and horizontal gradients in physical, chemical and biological characteristics of the water column, and to assess plankton dynamics and trophic carbon fluxes in the fjords and channels of central-south Patagonia. The water column was strongly stratified, with a pycnocline at ca. 20 m depth separating a surface layer of silicic acid-rich freshwater discharged by rivers, from the underlying nitrate- and orthophosphate-rich Subantarctic waters. The outflows from the Baker and Pascua Rivers, which range annually between 500 and 1500 m3 s-1, generate the strong land-ocean gradient in salinity (1-32 psu) and inorganic nutrient concentrations (2-8 and 2-24 μM in nitrate and silicic-acid, respectively) we observed along the Baker Fjord. The POC:chl-a ratio fluctuated from 1087 near the fjord’s head to 175 at its oceanic end in the Penas Gulf. This change was mainly due to an increase in diatom dominance and a concurrent decrease in allochthonous POC towards the ocean. Depth-integrated net primary production (NPP) and bacterial secondary production (BSP) fluctuated between 49 and 1215 and 36 and 150 mg C m-2 d-1, respectively, with higher rates in oceanic waters. At a time series station located close to the Baker River mouth, the average NPP was lower (average 360 mg C m-2 d-1) than at more oceanic stations (average 1063 mg C m-2 d-1), and numerically dominated (45%) by the picoplankton (food web is the main trophic pathway in these environments.

  6. 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.

  7. 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.

  8. Trophic magnification of organic chemicals: A global synthesis

    Science.gov (United States)

    Walter, W. David; Jardine, T.D.; Cade, Brian S.; Kidd, K.A.; Muir, D.C.G.; Leipzig-Scott, Peter C.

    2016-01-01

    Production of organic chemicals (OCs) is increasing exponentially, and some OCs biomagnify through food webs to potentially toxic levels. Biomagnification under field conditions is best described by trophic magnification factors (TMFs; per trophic level change in log-concentration of a chemical) which have been measured for more than two decades. Syntheses of TMF behavior relative to chemical traits and ecosystem properties are lacking. We analyzed >1500 TMFs to identify OCs predisposed to biomagnify and to assess ecosystem vulnerability. The highest TMFs were for OCs that are slowly metabolized by animals (metabolic rate kM compounds, regardless of KOW, and lowest for chemicals with rapid transformation rates (kM > 0.2 day–1). This probabilistic model provides a new global tool for screening existing and new OCs for their biomagnification potential.

  9. Cascade effects of crop species richness on the diversity of pest insects and their natural enemies.

    Science.gov (United States)

    Shi, PeiJian; Hui, Cang; Men, XingYuan; Zhao, ZiHua; Ouyang, Fang; Ge, Feng; Jin, XianShi; Cao, HaiFeng; Li, B Larry

    2014-07-01

    Understanding how plant species richness influences the diversity of herbivorous and predatory/parasitic arthropods is central to community ecology. We explore the effects of crop species richness on the diversity of pest insects and their natural enemies. Using data from a four-year experiment with five levels of crop species richness, we found that crop species richness significantly affected the pest species richness, but there were no significant effects on richness of the pests' natural enemies. In contrast, the species richness of pest insects significantly affected their natural enemies. These findings suggest a cascade effect where trophic interactions are strong between adjacent trophic levels, while the interactions between connected but nonadjacent trophic levels are weakened by the intermediate trophic level. High crop species richness resulted in a more stable arthropod community compared with communities in monoculture crops. Our results highlight the complicated cross-trophic interactions and the crucial role of crop diversity in the food webs of agro-ecosystems.

  10. Trophic relationships of small nonnative fishes in a natural creek and several agricultural drains flowing into the Salton Sea, and their potential, effects on the endangered desert pupfish

    Science.gov (United States)

    Martin, Barbara A.; Saiki, Michael K.

    2009-01-01

    This study was conducted to characterize trophic relationships of small nonnative fishes and to determine if predation by these fishes contributes to the decline of desert pupfish (Cyprinodon macularius), an endangered cyprinodont on the verge of extinction. We sampled 403 hybrid Mozambique tilapias (Oreochromis mossambica by O. urolepis), 107 redbelly tilapias (Tilapia zillii), 32 longjaw mudsuckers (Gillkhthys mirabilis), 182 western mosquitofish (Gambusia affinis), 222 sailfin mollies (Poecilia latipinna), 63 shortfin mollies (Poecilia mexicana), and 235 porthole livebearers (Poecilurpsis gracilis) from a natural creek and four agricultural drains during September 1999- December 2001. Evidence of piscivory was in gastrointestinal contents of 14 hybrid Mozambique tilapias, 3 redbelly tilapias, 10 longjaw mudsuckers, 8 western mosquitofish, 2 sailfin mollies, and 8 porthole livebearers. Although digestion often was too advanced for identification of fishes consumed by nonnative fishes, remains of desert pupfish were in gastrointestinal contents of a longjaw mudsucker. Our findings, along with Field evidence from other studies that inverse relationships exist between abundances of desert pupfish and nonnative species, are consistent with the hypothesis that predation by nonnative species is contributing to decline of desert pupfish. We suspect that competitive interactions with nonnative fishes might also adversely affect abundance of desert pupfish.

  11. 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

  12. 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.

  13. 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)

  14. 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)

  15. Water-quality effects on phytoplankton species and density and trophic state indices at Big Base and Little Base Lakes, Little Rock Air Force Base, Arkansas, June through August, 2015

    Science.gov (United States)

    Driver, Lucas; Justus, Billy

    2016-01-01

    Big Base and Little Base Lakes are located on Little Rock Air Force Base, Arkansas, and their close proximity to a dense residential population and an active military/aircraft installation make the lakes vulnerable to water-quality degradation. The U.S. Geological Survey (USGS) conducted a study from June through August 2015 to investigate the effects of water quality on phytoplankton species and density and trophic state in Big Base and Little Base Lakes, with particular regard to nutrient concentrations. Nutrient concentrations, trophic-state indices, and the large part of the phytoplankton biovolume composed of cyanobacteria, indicate eutrophic conditions were prevalent for Big Base and Little Base Lakes, particularly in August 2015. Cyanobacteria densities and biovolumes measured in this study likely pose a low to moderate risk of adverse algal toxicity, and the high proportion of filamentous cyanobacteria in the lakes, in relation to other algal groups, is important from a fisheries standpoint because these algae are a poor food source for many aquatic taxa. In both lakes, total nitrogen to total phosphorus (N:P) ratios declined over the sampling period as total phosphorus concentrations increased relative to nitrogen concentrations. The N:P ratios in the August samples (20:1 and 15:1 in Big Base and Little Base Lakes, respectively) and other indications of eutrophic conditions are of concern and suggest that exposure of the two lakes to additional nutrients could cause unfavorable dissolved-oxygen conditions and increase the risk of cyanobacteria blooms and associated cyanotoxin issues.

  16. 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

  17. 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

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. Trophic structure of polychaetes around an offshore gas platform.

    Science.gov (United States)

    Punzo, E; Strafella, P; Scarcella, G; Spagnolo, A; De Biasi, A M; Fabi, G

    2015-10-15

    The distribution of polychaetes associated with an offshore gas platform built on a muddy-sandy bottom in the northern Adriatic Sea was investigated with emphasis on their feeding structure. Polychaete species were collected at different distances from the rig using a Van Veen grab. Assessment of the polychaete community and trophic groups for impacts related to the presence of the platform demonstrated significantly different abundances at rising distances from the rig. The present findings highlight an effect of the rig on the spatial distribution of polychaete assemblages. Even though the effects of gas platforms on surrounding benthic communities have been investigated in the Adriatic Sea, no studies have addressed the distribution of polychaete trophic groups along a gradient based on distance from the rig. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Trophic flow within the microbial and mesozooplankton foodweb in the North Atlantic: processes indicated by analyses of stable isotopes and biovolume spectra.

    OpenAIRE

    Basedow, S.; da Silva, N.L.; Bode, A. (Antonio)

    2015-01-01

    The trophic flow from primary producers through the microbial and mesozooplankton food web makes sun energy available in particulate form for higher trophic levels. Pathways through the lower trophic levels are highly variable and determine productivity of the marine pelagic food webs. We analysed spatial variability in food web structure across the North Atlantic by means of stable isotope analyses (SIA) and biovolume spectrum theories (BST). At 7 stations in the Iceland Basin, ...

  4. 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

  5. Investigating microplastic trophic transfer in marine top predators.

    Science.gov (United States)

    Nelms, Sarah E; Galloway, Tamara S; Godley, Brendan J; Jarvis, Dan S; Lindeque, Penelope K

    2018-02-21

    Microplastics are highly bioavailable to marine organisms, either through direct ingestion, or indirectly by trophic transfer from contaminated prey. The latter has been observed for low-trophic level organisms in laboratory conditions, yet empirical evidence in high trophic-level taxa is lacking. In natura studies face difficulties when dealing with contamination and differentiating between directly and indirectly ingested microplastics. The ethical constraints of subjecting large organisms, such as marine mammals, to laboratory investigations hinder the resolution of these limitations. Here, these issues were resolved by analysing sub-samples of scat from captive grey seals (Halichoerus grypus) and whole digestive tracts of the wild-caught Atlantic mackerel (Scomber scombrus) they are fed upon. An enzymatic digestion protocol was employed to remove excess organic material and facilitate visual detection of synthetic particles without damaging them. Polymer type was confirmed using Fourier-Transform Infrared (FTIR) spectroscopy. Extensive contamination control measures were implemented throughout. Approximately half of scat subsamples (48%; n = 15) and a third of fish (32%; n = 10) contained 1-4 microplastics. Particles were mainly black, clear, red and blue in colour. Mean lengths were 1.5 mm and 2 mm in scats and fish respectively. Ethylene propylene was the most frequently detected polymer type in both. Our findings suggest trophic transfer represents an indirect, yet potentially major, pathway of microplastic ingestion for any species whose feeding ecology involves the consumption of whole prey, including humans. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  6. Trophic Interactions Between Insects and Stream-Associated Amphibians in Steep, Cobble-Bottom Streams of the Pacific Coast of North America

    Directory of Open Access Journals (Sweden)

    Trisha Atwood

    2012-04-01

    Full Text Available Two native, stream-associated amphibians are found in coastal streams of the west coast of North America, the tailed frog and the coastal giant salamander, and each interacts with stream insects in contrasting ways. For tailed frogs, their tadpoles are the primary life stage found in steep streams and they consume biofilm from rock surfaces, which can have trophic and non-trophic effects on stream insects. By virtue of their size the tadpoles are relatively insensitive to stream insect larvae, and tadpoles are capable of depleting biofilm levels directly (exploitative competition, and may also “bulldoze” insect larvae from the surfaces of stones (interference competition. Coastal giant salamander larvae, and sometimes adults, are found in small streams where they prey primarily on stream insects, as well as other small prey. This predator-prey interaction with stream insects does not appear to result in differences in the stream invertebrate community between streams with and without salamander larvae. These two examples illustrate the potential for trophic and non-trophic interactions between stream-associated amphibians and stream insects, and also highlights the need for further research in these systems.

  7. Trophic Interactions Between Insects and Stream-Associated Amphibians in Steep, Cobble-Bottom Streams of the Pacific Coast of North America.

    Science.gov (United States)

    Atwood, Trisha; Richardson, John S

    2012-04-10

    Two native, stream-associated amphibians are found in coastal streams of the west coast of North America, the tailed frog and the coastal giant salamander, and each interacts with stream insects in contrasting ways. For tailed frogs, their tadpoles are the primary life stage found in steep streams and they consume biofilm from rock surfaces, which can have trophic and non-trophic effects on stream insects. By virtue of their size the tadpoles are relatively insensitive to stream insect larvae, and tadpoles are capable of depleting biofilm levels directly (exploitative competition), and may also "bulldoze" insect larvae from the surfaces of stones (interference competition). Coastal giant salamander larvae, and sometimes adults, are found in small streams where they prey primarily on stream insects, as well as other small prey. This predator-prey interaction with stream insects does not appear to result in differences in the stream invertebrate community between streams with and without salamander larvae. These two examples illustrate the potential for trophic and non-trophic interactions between stream-associated amphibians and stream insects, and also highlights the need for further research in these systems.

  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. Ionizing radiation: levels and effects. Volume I. Levels

    International Nuclear Information System (INIS)

    1972-01-01

    This is the sixth substantive report of the United Nations Scientific Committee on the Effects of Atomic Radiation to the General Assembly. It reviews the levels of radiation received from all sources to which man is exposed and, among the effects of ionizing radiation, it considers the genetic effects, the effects on the immune response and the induction of malignancies in animals and man. These are not the only effects of ionizing radiation. The acute consequences of massive amounts of radiation that may be received accidentally or during nuclear warfare are not reviewed here (the short discussion of this subject in the 1962 report is still largely valid, at least as an introduction), nor are the effects on the nervous system and the induction of chromosome anomalies in somatic cells, which were both considered by the Committee in its 1969 report. Unlike previous reports of the Committee, the present report is submitted to the General Assembly without the technical annexes in which the evidence considered by the Committee is discussed in detail and in which the bases for the Committee's conclusions, which are stated in the report, are fully documented. However, the annexes are being made available at the same time as the report in a separate publication, issued in two volumes and the Committee wishes to draw the attention of the General Assembly to the fact that the separation of the report from the annexes is for convenience only and that major importance attaches to the scientific evidence given in the annexes.

  11. Human influences on trophic cascades along rocky shores

    Science.gov (United States)

    Lindberg, D.R.; Estes, J.A.; Warheit, K.I.

    1998-01-01

    A three-trophic-level interaction among American Black Oystercatchers (Haematopus bachmani), limpets (Lottia spp.), and erect fleshy algae in rocky intertidal communities of central and southern California was documented via manipulative and 'natural' experiments. Removal of the territorial limpet (Lottia gigantea) initially caused large increases in the percent cover of erect fleshy algae, followed by a more gradual increase in density of small limpets (Lottia spp.) and a decline in algal cover. Algal cover increased following the removal of small limpets at the sites from which L. gigantea had been removed earlier, thus demonstrating that the large and small limpets had similar inhibitory effects on plant populations. A comparison of sites with and without oyster-catchers showed that L. gigantea occupied substrate inclinations in proportion to their availability at sites where oystercatchers were rare, whereas the distribution of L. gigantea was skewed toward vertically inclined substrates where oystercatchers were common. Survival rates of limpets translocated to horizontal and vertical substrates were similar in sites lacking oystercatcher predation, but were much lower on horizontal substrates where oystercatchers were common. Our results are consistent with those from several prior studies in demonstrating that shorelines frequented by humans typically lack oystercatchers. Humans also exploit L. gigantea and reduce populations to low densities of small individuals. These findings may explain why the midlittoral zone of rocky intertidal communities in western North America are so often dominated by high population densities of small limpets.

  12. Trophic cascade induced by molluscivore predator alters pore-water biogeochemistry via competitive release of prey.

    Science.gov (United States)

    van Gils, Jan A; van der Geest, Matthijs; Jansen, Erik J; Govers, Laura L; de Fouw, Jimmy; Piersma, Theunis

    2012-05-01

    Effects of predation may cascade down the food web. By alleviating interspecific competition among prey, predators may promote biodiversity, but the precise mechanisms of how predators alter competition have remained elusive. Here we report on a predator-exclosure experiment carried out in a tropical intertidal ecosystem, providing evidence for a three-level trophic cascade induced by predation by molluscivore Red Knots (Calidris canutus) that affects pore water biogeochemistry. In the exclosures the knots' favorite prey (Dosinia isocardia) became dominant and reduced the individual growth rate in an alternative prey (Loripes lucinalis). Dosinia, a suspension feeder, consumes suspended particulate organic matter (POM), whereas Loripes is a facultative mixotroph, partly living on metabolites produced by sulfur-oxidizing chemoautotrophic bacteria, but also consuming suspended POM. Reduced sulfide concentrations in the exclosures suggest that, without predation on Dosinia, stronger competition for suspended POM forces Loripes to rely on energy produced by endosymbiotic bacteria, thus leading to an enhanced uptake of sulfide from the surrounding pore water. As sulfide is toxic to most organisms, this competition-induced diet shift by Loripes may detoxify the environment, which in turn may facilitate other species. The inference that predators affect the toxicity of their environment via a multi-level trophic cascade is novel, but we believe it may be a general phenomenon in detritus-based ecosystems.

  13. 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.

  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. Ecological opportunities and intraspecific competition alter trophic niche specialization in an opportunistic stream predator.

    Science.gov (United States)

    Evangelista, Charlotte; Boiche, Anatole; Lecerf, Antoine; Cucherousset, Julien

    2014-09-01

    Many generalist populations are composed of specialized individuals that use a narrow part of the population's niche. Ecological theories predict that individual specialization and population trophic niche are determined by biotic interactions and resource diversity emerging from environmental variations (i.e. ecological opportunities). However, due to the paucity of empirical and experimental demonstrations, the genuine importance of each of these drivers in determining trophic niche attributes is not fully appreciated. The present study aimed at determining the population level and individual responses of brown trout (Salmo trutta) to variations in ecological opportunities (terrestrial prey inputs) and autochthonous prey communities among 10 stream reaches along a riparian condition gradient using individual longitudinal monitoring and stable isotope analyses. Our results suggested that trophic niche diversity varied along the environmental gradient, while individual trophic specialization was indirectly driven by ecological opportunities through strengthened intraspecific competition. Individual diet was repeatable over the study period, and the growth rate of juvenile brown trout increased with their specialization for aquatic predatory invertebrates. Our findings highlight the dual influences of intraspecific competition and ecological opportunities on individual trophic specialization and population trophic niche. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

  16. Transferência trófica de mercúrio e selênio na costa norte do Rio de Janeiro Trophic transference of mercury and selenium in the northern coast of Rio de Janeiro

    Directory of Open Access Journals (Sweden)

    Helena A. Kehrig

    2009-01-01

    Full Text Available Trophic transfer of trace elements along marine food chains has been recognized as an important process influencing metal and metalloid bioaccumulation. The trophic transfer of mercury was observed between trophic levels from prey (considering fish with different feeding habits and squid to top predator (dolphin in a Northern coastal food chain of Rio de Janeiro. Selenium showed some evidence of trophic transfer between lower trophic levels. Dolphin presented the highest mercury concentrations whereas the benthic carnivorous fish showed the highest selenium concentrations. Mercury is biomagnified through the food chain while selenium does not present the same behavior.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Tri-trophic effects of seasonally variable induced plant defenses vary across the development of a shelter building moth larva and its parasitoid.

    Science.gov (United States)

    Rose, Noah H; Halitschke, Rayko; Morse, Douglass H

    2015-01-01

    Plant chemical defenses can negatively affect insect herbivore fitness, but they can also decrease herbivore palatability to predators or decrease parasitoid fitness, potentially changing selective pressures on both plant investment in production of chemical defenses and host feeding behavior. Larvae of the fern moth Herpetogramma theseusalis live in and feed upon leaf shelters of their own construction, and their most abundant parasitoid Alabagrus texanus oviposits in early instar larvae, where parasitoid larvae lay dormant for most of host development before rapidly developing and emerging just prior to host pupation. As such, both might be expected to live in a relatively constant chemical environment. Instead, we find that a correlated set of phenolic compounds shows strong seasonal variation both within shelters and in undamaged fern tissue, and the relative level of these compounds in these two different fern tissue types switches across the summer. Using experimental feeding treatments, in which we exposed fern moth larvae to different chemical trajectories across their development, we show that exposure to this set of phenolic compounds reduces the survival of larvae in early development. However, exposure to this set of compounds just before the beginning of explosive parasitoid growth increased parasitoid survival. Exposure during the period of rapid parasitoid growth and feeding decreased parasitoid survival. These results highlight the spatial and temporal complexity of leaf shelter chemistry, and demonstrate the developmental contingency of associated effects on both host and parasitoid, implying the existence of complex selective pressures on plant investment in chemical defenses, host feeding behavior, and parasitoid life history.

  2. 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.

  3. Ploidy of cell-sorted trophic and cystic forms of Pneumocystis carinii.

    Directory of Open Access Journals (Sweden)

    Anna Martinez

    Full Text Available Once regarded as an AIDS-defining illness, Pneumocystis pneumonia (PcP is nowadays prevailing in immunocompromised HIV-negative individuals such as patients receiving immunosuppressive therapies or affected by primary immunodeficiency. Moreover, Pneumocystis clinical spectrum is broadening to non-severely-immunocompromised subjects who could be colonized by the fungus while remaining asymptomatic for PcP, thus being able to transmit the infection by airborne route to susceptible hosts. Although the taxonomical position of the Pneumocystis genus has been clarified, several aspects of its life cycle remain elusive such as its mode of proliferation within the alveolus or its ploidy level. As no long-term culture model exists to grow Pneumocystis organisms in vitro, an option was to use a model of immunosuppressed rat infected with Pneumocystis carinii and sort life cycle stage fractions using a high-through-put cytometer. Subsequently, ploidy levels of the P. carinii trophic and cystic form fractions were measured by flow cytometry. In the cystic form, eight contents of DNA were measured thus strengthening the fact that each mature cyst contains eight haploid spores. Following release, each spore evolves into a trophic form. The majority of the trophic form fraction was haploid in our study. Some less abundant trophic forms displayed two contents of DNA indicating that they could undergo (i mating/fusion leading to a diploid status or (ii asexual mitotic division or (iii both. Even less abundant trophic forms with four contents of DNA were suggestive of mitotic divisions occurring following mating in diploid trophic forms. Of interest, was the presence of trophic forms with three contents of DNA, an unusual finding that could be related to asymmetrical mitotic divisions occurring in other fungal species to create genetic diversity at lower energetic expenses than mating. Overall, ploidy data of P. carinii life cycle stages shed new light on the

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

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Olivier [Laboratoire de Radioecologie et Ecotoxicologie, Institut de Radioprotection et de Surete Nucleaire, Cadarache, Bat., 186 BP3, 13115 Saint Paul-Lez-Durance Cedex (France)]. E-mail: olivier.simon@irsn.fr; Garnier-Laplace, Jacqueline [Laboratoire de Radioecologie et Ecotoxicologie, Institut de Radioprotection et de Surete Nucleaire, Cadarache, Bat., 186 BP3, 13115 Saint Paul-Lez-Durance Cedex (France)

    2005-09-30

    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 {mu}g/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.

  5. 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 ...

  6. Trophic diversity of Poznań Lakeland lakes

    OpenAIRE

    Dzieszko Piotr; Zwoliński Zbigniew

    2015-01-01

    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 investi...

  7. Intraspecific variation in feeding strategies of Galapagos sea lions: A case of trophic specialization

    Science.gov (United States)

    Villegas-Amtmann, Stella; Costa, Daniel

    2017-01-01

    The trophic behavior of marine predators varies according to the level of competition to which they are exposed. In general, populations that inhabit lower productivity systems face a strong intraspecific competition, which contributes to the development of different foraging strategies to maximize nutritional efficiency. Given the high trophic flexibility of Zalophus wollebaeki, this species is considered appropriate for the analysis of such behavior. Furthermore, this trophic flexibility has allowed them to persist in a seemingly marginal ecosystem. In this study, we used a comparative analysis of variables (diet and dive behavior) related to Z. wollebaeki trophic niche plasticity to better understand their foraging ecology, using techniques such scat analysis, satellite telemetry and complementarily an isotopic analysis. Scat analysis revealed intra-population variation in their diet, represented by prey from different environments (epipelagic and benthic). These results are supported by the animals’ locations at sea and diving profiles. Global Positioning System (GPS) and time-depth recorder (TDR) records showed the existence of two groups, with differing feeding areas and diving behavior. Also the δ15N values showed differences in the trophic level at which the species fed. These results constitute a relevant finding in the evolutionary behavior of the species, showing that Z. wollebaeki has developed a high degree of foraging flexibility, thus increasing its survival rate in an ecosystem that is highly demanding in terms of resource availability. PMID:29059188

  8. Intraspecific variation in feeding strategies of Galapagos sea lions: A case of trophic specialization.

    Directory of Open Access Journals (Sweden)

    Diego Páez-Rosas

    Full Text Available The trophic behavior of marine predators varies according to the level of competition to which they are exposed. In general, populations that inhabit lower productivity systems face a strong intraspecific competition, which contributes to the development of different foraging strategies to maximize nutritional efficiency. Given the high trophic flexibility of Zalophus wollebaeki, this species is considered appropriate for the analysis of such behavior. Furthermore, this trophic flexibility has allowed them to persist in a seemingly marginal ecosystem. In this study, we used a comparative analysis of variables (diet and dive behavior related to Z. wollebaeki trophic niche plasticity to better understand their foraging ecology, using techniques such scat analysis, satellite telemetry and complementarily an isotopic analysis. Scat analysis revealed intra-population variation in their diet, represented by prey from different environments (epipelagic and benthic. These results are supported by the animals' locations at sea and diving profiles. Global Positioning System (GPS and time-depth recorder (TDR records showed the existence of two groups, with differing feeding areas and diving behavior. Also the δ15N values showed differences in the trophic level at which the species fed. These results constitute a relevant finding in the evolutionary behavior of the species, showing that Z. wollebaeki has developed a high degree of foraging flexibility, thus increasing its survival rate in an ecosystem that is highly demanding in terms of resource availability.

  9. Intraspecific variation in feeding strategies of Galapagos sea lions: A case of trophic specialization.

    Science.gov (United States)

    Páez-Rosas, Diego; Villegas-Amtmann, Stella; Costa, Daniel

    2017-01-01

    The trophic behavior of marine predators varies according to the level of competition to which they are exposed. In general, populations that inhabit lower productivity systems face a strong intraspecific competition, which contributes to the development of different foraging strategies to maximize nutritional efficiency. Given the high trophic flexibility of Zalophus wollebaeki, this species is considered appropriate for the analysis of such behavior. Furthermore, this trophic flexibility has allowed them to persist in a seemingly marginal ecosystem. In this study, we used a comparative analysis of variables (diet and dive behavior) related to Z. wollebaeki trophic niche plasticity to better understand their foraging ecology, using techniques such scat analysis, satellite telemetry and complementarily an isotopic analysis. Scat analysis revealed intra-population variation in their diet, represented by prey from different environments (epipelagic and benthic). These results are supported by the animals' locations at sea and diving profiles. Global Positioning System (GPS) and time-depth recorder (TDR) records showed the existence of two groups, with differing feeding areas and diving behavior. Also the δ15N values showed differences in the trophic level at which the species fed. These results constitute a relevant finding in the evolutionary behavior of the species, showing that Z. wollebaeki has developed a high degree of foraging flexibility, thus increasing its survival rate in an ecosystem that is highly demanding in terms of resource availability.

  10. 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.

  11. 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.

  12. 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.

  13. EVALUATION OF THE WATER TROPHIC STATE OF WAPIENICA DAM RESERVOIR

    Directory of Open Access Journals (Sweden)

    Ewa Jachniak

    2015-01-01

    Full Text Available In this publication the trophy level of Wapienica dam reservoir, based on the composition species of planktonic algae and their biomass, and concentrations of chlorophyll a, was defined. The research was conducted during the vegetative season in 2013 year; the samples were taken from two research points (W1 – the part of river Wapienica inflow to reservoir and W2 – the part of the reservoir dam by using bathometer. The whole biomass of planktonic algae and concentration of chlorophyll a from two research areas were low and it allowed to classify water of this reservoir to oligo-/ mesotrophic. Only in the part of the reservoir dam, in summer season, an increased trophy level was observed (Heinonen 1980. A similar trophic character (oligo-/ mesotrophic of the water reservoir was also indicated by algae species: Achnanthes lanceolata (Bréb. Grun. in Cl. and Grun., Chrysoccoccus minutus (Fritsch Nygaard. For a temporary increase of the trophy level, the diatom Nitzschia acicularis (Kütz. W. Sm. could indicate, because it is a typical species in poorly eutrophic water. The green algae (Pediastrum and Coelastrum, which were observed in summer season could also indicate for a rise of the trophic state, because they are typical for eutrophic water.

  14. 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.

  15. Genetic analysis of interacting trophic levels in a stressed pinyon-juniper community: A model for examining community responses to a rapid and recent environmental changes. Final report, May 1, 1994--April 30, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Keim, P.; Whithmam, T.; Cobb, N.; Gehring, C.

    1998-05-01

    The goals of this project were to examine the genetic component of a pinyon-juniper woodland that had recently experienced a dramatic environmental change. The environmental change was increased temperature and decreased water associated with the volcanic cinder field at Sunset Crater National Monument. In all of these experiments we have used adjacent soil sites as controls for the effects of the stressed locations. We have examined mycorrhizal colonization and diversity in order to understand this important component in community {open_quotes}adaptation{close_quotes} to climate change. We have examined genetic diversity in the pinyon pine populations to determine what level of genetic differentiation has occurred between stressed and nonstressed locations. In addition, we have recently expanded our environmental parameters to include elevated CO{sub 2} on mycorrhizal performance and diversity.

  16. The trophic status of Suwałki Landscape Park lakes based on selected parameters (NE Poland).

    Science.gov (United States)

    Jekatierynczuk-Rudczyk, Elżbieta; Zieliński, Piotr; Grabowska, Magdalena; Ejsmont-Karabin, Jolanta; Karpowicz, Maciej; Więcko, Adam

    2014-08-01

    This study describes changes in the trophic status of 12 lakes within Suwałki Landscape Park (SLP). All of the trophic classifications of the lakes were based on the trophic continuum division. Trophic status was determined by means of multiparameter indices using several diverse criteria. In this study, the assessment of the trophic status of lakes included water quality; abundance and biomass of bacterioplankton, phytoplankton, and zooplankton; and primary production of phytoplankton. The Carlson trophic state index (TSI) describes the level of water fertility and indicated the dominance of moderately eutrophic waters. Lakes Perty, Jeglówek, and Hańcza have a trophic status that indicates mesotrophy (TSI trophic status of the studied lakes was determined based on the bacterial abundance and clearly showed a lack of oligotrophic lakes in SLP. Based on the number of bacteria, only Lake Szurpiły can be classified as β-mesotrophic, whereas Lake Linówek can be characterized as hypertrophic with some features typical for humic waters. The greatest value of gross primary production was observed in Lake Linówek (126.4 mg C/m(3)/h). The phytoplankton trophy index varied from 1.59 to 2.28, and its highest value, which indicated eutrophy, was determined for Lake Udziejek. In the case of Lakes Hańcza, Szurpiły, Perty, Jeglówek, and Kojle, the index ranged from 1.25 to 1.74, which indicated mesotrophy. The majority of the lakes were classified as mesoeutrophic (1.75-2.24). The highest trophic status was assessed for lakes with a marked dominance of cyanobacteria (Lake Przechodnie, Lake Krajwelek, Lake Udziejek, and Lake Pogorzałek), which is commonly recognized as an indicator of high trophic status. Considering all of the indices of trophic status, the analysis of rotifer community structure indicates that the studied group of lakes is mesoeutrophic or eutrophic. The values of crustacean zooplankton indices indicated that the trophic status of the studied lakes

  17. Trophic transfer of metal nanoparticles in freshwater ecosystems

    DEFF Research Database (Denmark)

    Tangaa, Stine Rosendal

    Metal-containing engineered nanoparticles (Me-ENPs) are used in a wide range of products, such as inks, plastics, consumer products, lubricants, electronics and bioactive coatings. Silver (Ag) ENPs are one of the most used Me-ENPs to date, primarily due to its antibacterial effects. When entering...... was examined. The biodynamic modelling approach was used to characterize Ag uptake from the two different uptake routes as well as to describe the elimination of Ag after waterborne exposures to the two Ag-forms. Thirdly, trophic transfer of silver Ag ENPs in a simple freshwater food web, including sediment...

  18. Molecular trophic markers in marine food webs and their potential use for coral ecology.

    Science.gov (United States)

    Leal, Miguel Costa; Ferrier-Pagès, Christine

    2016-10-01

    Notable advances in ecological genomics have been driven by high-throughput sequencing technology and taxonomically broad sequence repositories that allow us to accurately assess species interactions with great taxonomic resolution. The use of DNA as a marker for ingested food is particularly relevant to address predator-prey interactions and disentangle complex marine food webs. DNA-based methods benefit from reductionist molecular approaches to address ecosystem scale processes, such as community structure and energy flow across trophic levels, among others. Here we review how molecular trophic markers have been used to better understand trophic interactions in the marine environment and their advantages and limitations. We focus on animal groups where research has been focused, such as marine mammals, seabirds, fishes, pelagic invertebrates and benthic invertebrates, and use case studies to illustrate how DNA-based methods unraveled food-web interactions. The potential of molecular trophic markers for disentangling the complex trophic ecology of corals is also discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. HELLE: Health Effects of Low Level Exposures

    International Nuclear Information System (INIS)

    Schoten, Eert

    1998-01-01

    The Health Council is closely involved in establishing the scientific foundation of exposure limits for substances and radiation in order to protect public health. Through the years, the Council has contributed to the formulation of principles and procedures, both for carcinogenic and for noncarcinogenic agents. As a rule, the discussion with regard to the derivation of health-based recommended exposure limits centers around the appropriateness of extrapolation methods (What can be inferred from data on high exposure levels and on experimental animals?). Generally speaking, there is a lack of direct information on the health effects of low levels of exposure. Effects at these levels cannot usually be detected by means of traditional animal experiments or epidemiological research. The capacity of these analytical instruments to distinguish between ''signal'' and ''noise'' is inadequate in most cases. Annex B of this report contains a brief outline of the difficulties and the established methods for tackling this problem. In spite of this, the hope exists that the posited weak signals, if they are indeed present, can be detected by other means. The search will have to take place on a deeper level. In other words, effort must be made to discover what occurs at underlying levels of biological organization when organisms are exposed to low doses of radiation or substances. Molecular and cell biology provide various methods and techniques which give an insight into the processes within the cell. This results in an increase in the knowledge about the molecular and cellular effects of exposure to agents, or stated differently, the working mechanisms which form the basis of the health effects. Last year, the Health Council considered that the time was ripe to take stock of the state of knowledge in this field. To this end, an international working conference was held from 19 to 21 October 1997, entitled ''Health Effects of Low Level Exposures: Scientific Developments and

  4. 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.

  5. 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

  6. 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.

  7. Assessment of phytoplankton and environmental variables for water quality and trophic state classification in the Gemlik Gulf, Marmara Sea (Turkey).

    Science.gov (United States)

    Balci, Muharrem; Balkis, Neslihan

    2017-02-15

    Phytoplankton assemblages related to environmental factors and ecological status of the Gemlik Gulf were investigated between June 2010 and May 2011. A total 155 phytoplankton species were detected and 6 taxa (Amphisolenia laticincta, Archaeperidinium minutum, Cochlodinium sp., Gynogonadinium aequatoriale, Heterocapsa rotundata and Metaphalacroma sp.) were new records for the Turkish Seas. The lowest and highest total phytoplankton abundance among the sampling units (depths) was recorded in April 2011 (7.4×10 3 cellsL -1 ) and July 2010 (251.8×10 3 cellsL -1 ). Local small patches of visible red tide events were detected especially in the gulf, although a phytoplankton bloom was not observed. The water column was well stratified in the early autumn and well mixed in the early spring according to stratification index values. Surface nutrient concentrations increased especially at stations located inside of the gulf. The limiting effect of silicate was observed in early, mid-summer and early winter periods while the nitrogen was the limiting nutrient in the gulf during the whole sampling period. In the Gulf, low water quality-high mesotrophic and bad water quality-eutrophic status, high quality and low trophic level were generally detected according to Chl a, dissolved oxygen and trophic index. However, indices developed to determine the trophic level and water quality of the Mediterranean Sea can give unexpected results about the current environmental quality status when it is applied to the Marmara Sea which has limited photic zone by the halocline-pycnocline and thermocline. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Effects of water quality and trophic status on helminth infections in the cyprinid fish, Schizothorax niger Heckel, 1838 from three lakes in the Kashmir Himalayas.

    Science.gov (United States)

    Zargar, U R; Yousuf, A R; Chishti, M Z; Ahmed, F; Bashir, H; Ahmed, F

    2012-03-01

    Water quality greatly influences the population density of aquatic biota, including parasites. In order to evaluate the relationship between fish parasites and water quality in Kashmir Himalayas, we assessed helminth parasite densities in Schizothorax niger Heckel, 1838 (an endemic cyprinid fish of Kashmir) from three lakes, namely Anchar, Manasbal and Dal, which reflected the varied stages of eutrophication. The overall prevalence of helminth infections was higher in the hypertrophic Anchar Lake (prevalence = 18.6%) compared to Manasbal Lake, which was the least eutrophied (prevalence = 6.4%). Furthermore, mean prevalence of monoxenous and heteroxenous parasites was higher in lakes containing higher levels of water degradation (Anchar and Dal). The mean number of helminth species per fish host was the highest in the hypertrophic lake (1.3 ± 0.3) in comparison to the least eutrophic lake (0.2 ± 1.5). Variability of calculated infection indices (prevalence, mean intensity and mean abundance) revealed that helminth parasite composition in the fish was affected by the lakes' environmental stress (degraded water quality). Therefore, data on the density of helminth parasites in fish can provide supplementary information on the pollution status of a water body.

  9. 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.

  10. 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

    2012-01-01

    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. PMID:22719034

  11. Phosphorus fractions and the effect of pH on the phosphorus release of the sediments from different trophic areas in Taihu Lake, China

    International Nuclear Information System (INIS)

    Jin Xiangcan; Wang Shengrui; Pang Yan; Wu Fengchang

    2006-01-01

    The sediment characteristics, different phosphorus (P) fraction concentrations and the effect of pH on P release were investigated in a shallow eutrophic lake in China. The total phosphorus (TP) concentrations in the sediments ranged greatly from 420 to 3408 mg kg -1 and inorganic P (IP) was the main P fraction. For the heavily eutrophic sediment, IP mainly consisted of NaOH-P; while for the mesotrophic sediments, IP mainly consisted of HCl-P. The rate of P release decreased as pH increased from 2 to 6. But it increased as pH increased from 8 to 12. It is suggested that high pH promoted the release of NaOH-P, and low pH promoted the release of HCl-P, and there was no P release occurring in the neutral condition. - Factors affecting internal loading of phosphorus were investigated in a hypereutrophic lake in China

  12. Nuisance levels of noise effects radiologists' performance

    Science.gov (United States)

    McEntee, Mark F.; Coffey, Amina; Ryan, John; O'Beirne, Aaron; Toomey, Rachel; Evanoff, Micheal; Manning, David; Brennan, Patrick C.

    2010-02-01

    This study aimed to measure the sound levels in Irish x-ray departments. The study then established whether these levels of noise have an impact on radiologists performance Noise levels were recorded 10 times within each of 14 environments in 4 hospitals, 11 of which were locations where radiologic images are judged. Thirty chest images were then presented to 26 senior radiologists, who were asked to detect up to three nodular lesions within 30 posteroanterior chest x-ray images in the absence and presence of noise at amplitude demonstrated in the clinical environment. The results demonstrated that noise amplitudes rarely exceeded that encountered with normal conversation with the maximum mean value for an image-viewing environment being 56.1 dB. This level of noise had no impact on the ability of radiologists to identify chest lesions with figure of merits of 0.68, 0.69, and 0.68 with noise and 0.65, 0.68, and 0.67 without noise for chest radiologists, non-chest radiologists, and all radiologists, respectively. the difference in their performance using the DBM MRMC method was significantly better with noise than in the absence of noise at the 90% confidence interval (p=0.077). Further studies are required to establish whether other aspects of diagnosis are impaired such as recall and attention and the effects of more unexpected noise on performance.

  13. [Werner syndrome with torpid trophic ulcera cruris].

    Science.gov (United States)

    Hürlimann, A F; Schnyder, U W

    1991-11-01

    Werner's syndrome is a rare, autosomal recessive inherited disorder with a distinctive clinical picture. The characteristic physiognomy, shortness of stature with thin extremities, and large trophic ulcers are the key signs for the diagnosis. Premature greying of the hair and baldness, juvenile cataracts, a tendency to diabetes mellitus, hypogonadism, calcifications of the blood vessels, osteoporosis, metastatic calcifications of the soft tissue and an elevated incidence of neoplasms are further important features. We describe two patients with this disorder.

  14. Phytoplankton community and chlorophyll a as trophic state indices of Lake Skadar (Montenegro, Balkan).

    Science.gov (United States)

    Rakocevic-Nedovic, Jelena; Hollert, Henner

    2005-01-01

    Phytoplankton, as a first step in trophic cascades of lakes, can be a good indicator of trophic states, considering that every environmental change affects this community and many species of this community are sensitive to changes, and that they response very quickly. In this study, we tried to assess and predict the trophic state of Lake Skadar according to phytoplankton data. Water samples were collected using Ruttner sampling bottle. Temperature, dissolved oxygen, ph, conductivity and transparence were measured in situ using portable equipment. Nutrients and chlorophyll a were measured using standard spectrophotometric methods. A determination of phytoplankton species was performed using relevant keys and the counting of cells was performed using sedimentation methods. The species composition of Lake Skadar revealed 95 taxa, with Chlorophyceae and Bacillariophyceae being represented best. According to an average chlorophyll a concentration of 5.9 pg/l, Lake Skadar belongs to the mesotrophic level of the trophic scale. Developed prediction equation for chlorophyll a revealed a good prediction (R2 = 0.71) and the parameter Secchi depth was primarily correlated with chlorophyll a concentration. Trophic state indices derived from chlorophyll a and transparency, were close together, but both were below the phosphorous index. Values of trophic state indices rank the Lake Skadar as being mesotrophic. This study also showed that indices of diversity based on phytoplankton are weak indicators of trophic status and that they can well characterize only differences between assemblages and associations. According to calculated saprobic indices (ranging from 1.5 to 2.15), Lake Skadar is on betamesosaprobic level of saprobity, which means that it is moderately polluted with organic compounds. Total phosphorus is not the main limiting factor for the phytoplankton community in Lake Skadar. Disagreements between chlorophyll and the transparency index, on the one hand, and the

  15. 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).

  16. 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

  17. Influence of nutrient input on the trophic state of a tropical brackish ...

    Indian Academy of Sciences (India)

    Ecosystem level changes in water quality and biotic communities in coastal lagoons have been associated ... in lagoon water. Trophic state index calculated for different sectors of the lagoon confirmed the inter- sectoral and inter-seasonal shift from mesotrophic to eutrophic .... After 72 hr of incubation at room temperature,.

  18. Increasing trophic complexity influences aphid attendance by ants (Hymenoptera: Formicidae) and predation

    Science.gov (United States)

    Species that are involved in multitrophic interactions are affected by the trophic levels that are above and below them in both indirect and direct ways. In this experiment, interactions among ants (Formica montana Wheeler; Hymenoptera: Formicidae), aphids (Myzus persicae [Sulzer]; Hemiptera: Aphidi...

  19. Diversity and distribution of freshwater testate amoebae (protozoa) along latitudinal and trophic gradients in China.

    Science.gov (United States)

    Ju, Lihua; Yang, Jun; Liu, Lemian; Wilkinson, David M

    2014-11-01

    Freshwater microbial diversity is subject to multiple stressors in the Anthropocene epoch. However, the effects of climate changes and human activities on freshwater protozoa remain poorly understood. In this study, the diversity and distribution of testate amoebae from the surface sediments were investigated in 51 Chinese lakes and reservoirs along two gradients, latitude and trophic status. A total of 169 taxa belonging to 24 genera were identified, and the most diverse and dominant genera were Difflugia (78 taxa), Centropyxis (26 taxa) and Arcella (12 taxa). Our analysis revealed that biomass of testate amoebae decreased significantly along the latitudinal gradient, while Shannon-Wiener indices and species richness presented an opposite trend (P trophic status (P trophic status on diversity and distribution of testate amoebae in China. Therefore, our results provide valuable baseline data on testate amoebae and contribute to lake management and our understanding of the large-scale global patterns in microorganism diversity.

  20. Mercury sources and trophic ecology for Hawaiian bottomfish.

    Science.gov (United States)

    Sackett, Dana K; Drazen, Jeffrey C; Choy, C Anela; Popp, Brian; Pitz, Gerald L

    2015-06-02

    In Hawaii, some of the most important commercial and recreational fishes comprise an assemblage of lutjanids and carangids called bottomfish. Despite their importance, we know little about their trophic ecology or where the mercury (Hg) that ultimately resides in their tissue originates. Here we investigated these topics, by analyzing muscle samples for mercury content, nitrogen, carbon, and amino acid specific nitrogen isotope ratios in six species distributed across different depths from the Northwestern Hawaiian Islands (NWHI) and the Main Hawaiian Islands (MHI). Fishes had different sources of nitrogen and carbon, with isotopic values suggesting benthic food sources for shallow nearshore species. High trophic position lutjanids that foraged in deeper water, benthic environments generally had higher Hg levels. Model results also suggested that benthic Hg methylation was an important source of Hg for shallow benthic feeders, while deepwater sources of mercury may be important for those with a diet that derives, at least in part, from the pelagic environment. Further, despite the lack of freshwater sources of Hg in the NWHI, statistical models explaining the variation in tissue Hg in the MHI and NWHI were nearly identical, suggesting freshwater Hg inputs were not a major source of Hg in fish tissue.

  1. Questioning the role of phenology shifts and trophic mismatching in a planktonic food web

    Science.gov (United States)

    Atkinson, Angus; Harmer, Rachel A.; Widdicombe, Claire E.; McEvoy, Andrea J.; Smyth, Tim J.; Cummings, Denise G.; Somerfield, Paul J.; Maud, Jacqueline L.; McConville, Kristian

    2015-09-01

    In a warming climate, differential shifts in the seasonal timing of predators and prey have been suggested to lead to trophic "mismatches" that decouple primary, secondary and tertiary production. We tested this hypothesis using a 25-year time-series of weekly sampling at the Plymouth L4 site, comparing 57 plankton taxa spanning 4 trophic levels. During warm years, there was a weak tendency for earlier timings of spring taxa and later timings of autumn taxa. While this is in line with many previous findings, numerous exceptions existed and only a few taxa (e.g. Gyrodinium spp., Pseudocalanus elongatus, and Acartia clausi) showed consistent, strong evidence for temperature-related timing shifts, revealed by all 4 of the timing indices that we used. Also, the calculated offsets in timing (i.e. "mismatches") between predator and prey were no greater in extreme warm or cold years than during more average years. Further, the magnitude of these offsets had no effect on the "success" of the predator, in terms of their annual mean abundance or egg production rates. Instead numerous other factors override, including: inter-annual variability in food quantity, high food baseline levels, turnover rates and prolonged seasonal availability, allowing extended periods of production. Furthermore many taxa, notably meroplankton, increased well before the spring bloom. While theoretically a chronic mismatch, this likely reflects trade-offs for example in predation avoidance. Various gelatinous taxa (Phaeocystis, Noctiluca, ctenophores, appendicularians, medusae) may have reduced these predation constraints, with variable, explosive population outbursts likely responding to improved conditions. The match-mismatch hypothesis may apply for highly seasonal, pulsed systems or specialist feeders, but we suggest that the concept is being over-extended to other marine systems where multiple factors compensate.

  2. Mechanisms underlying plant sexual dimorphism in multi-trophic arthropod communities.

    Science.gov (United States)

    Petry, William K; Perry, Kayla I; Fremgen, Aleshia; Rudeen, Sarahi K; Lopez, Mitchell; Dryburgh, John; Mooney, Kailen A

    2013-09-01

    A growing body of research documents the importance of plant genetic effects on arthropod community structure. However, the mechanisms underlying these effects are often unclear. Additionally, plant genetic effects have largely been quantified in common gardens, thus inflating the estimates of their importance by minimizing levels of natural variation. Using Valeriana edulis, a dioecious plant with genetically based sex determination, we conducted surveys and experiments on wild-grown individuals to document field patterns of arthropod association between the sexes and the mechanisms underlying these plant genetic effects. Three years of surveys revealed strong and consistent sex-biased arthropod association in wild-grown plants: female plants supported 4-fold, 1.5-fold, and 4-fold higher densities of aphids, aphid predators, and aphid-tending ants, respectively, compared to males. There was mixed evidence that the female bias for aphids was due to higher plant quality, while we found no difference between plant sexes in aphid preference or the top-down effects of predators and tending ants. Female bias for ants was due to both the greater attractiveness of female plants (direct effect mediated by floral nectar) and an independent, weaker effect of higher aphid abundance on females (density-mediated indirect effect). Conversely, the female bias for predators was driven solely by the greater attractiveness of female plants. We did not find interaction modification, i.e., ant-aphid and predator-aphid interactions were equivalent between plant sexes. Plant sex explained 0.24%, 2.28%, and 4.42% of the variance in aphids, predators, and ants, respectively, values comparable to but slightly weaker than those previously reported from common-garden studies. In contrast to the prediction of diminished plant genetic effects with increasing trophic level, we show how weak indirect effects on predators and parasitoids (via herbivores) can be complemented by strong direct

  3. 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

  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. [Treatment of venous trophic ulcers, using echoscleroobliteration of perforant veins].

    Science.gov (United States)

    Rusyn, V I; Korsak, V V; Boldizhar, P O; Borsenko, M I; Mytrovka, B A

    2014-02-01

    In 36 patients, suffering trophic ulcers on a chronic venous insufficiency background in a decompensated stage (C6 in accordance to CEAP), echoscleroobliteration of perforant veins, using a "foam-form" method in accordance to Tessari, was performed. In 29 patients postrombophlebitic syndrome in incomplete recanalization stage was diagnosed, in 7 recurrence of varicose disease of the lower extremities. In all the patients during echoscleroobliteration there was possible to obliterate the insufficient perforant veins, in 3 patients two perforant veins were obliterated in each of them. In a one week a pathological blood flow along perforant veins, in accordance to data of ultrasound duplex scanning, was absent. This effect lasted during 6 mo in 29 (80.6%) patients. In 25 (69.4%) patients a trophic ulcers healing was achieved in 1 - 3 mo. In a one year in 30 (83.3%) patients a stable obliteration was noted, in 3 (8.3%) - partial recanalization, in 3 (8.3%) - complete recanalization of perforant veins.

  6. Effects of microelectronics on industrial level measuring

    International Nuclear Information System (INIS)

    Schaudel, D.E.

    1979-01-01

    Microelectronic elements and production technologies have begun to change industrial level measurement, and this trend will continue. Spectacular breakthroughs cannot be expected, due to the major demand of reliability and to administrative constraints. The demand for transducers has increased with the advance of low-cost computer hardware. Electronics makes well-known method of measurements more universally applicable; it helps to realize new methods, and to design multifunctional transducers which always give the necessary signal for process guidance. The effects on society and environment are wholly positive: More and better measuring technologies permit a better utilisation of raw materials and energies, help to prevent environmental damage, and to raise the standard of living. Negative results are not to be expected on this sector. (orig./RW) [de

  7. GLUCOCORTICOSTEROIDS' EFFECT UPON THE COMPLEMENT LEVEL

    Directory of Open Access Journals (Sweden)

    Voja Pavlovic

    2001-03-01

    Full Text Available The effect of high doses of cortisol upon the level of the overall complements'hemolytic activity and particular complements' components is studies. The experimentsinvolved guinea pigs of male sex of the body mass from 300 to 400 g, namelythose that have not been treated by anything so far. The doses of hydrocortisone(Hemofarm DD were also used for the experiment. The overall complements'activity was determined by testing the capabilities of a series of various solutions ofthe guinea pigs' serum to separate sheep erythrocytes that were made sensitive byrabbit anti-erythrocyte antibodies. The determination of the C1, C2, C3 and C4complements' components was done by the method of the quantitative diffusion ofthe radial type by using the Partigen blocks Behringwerke AG. The series comprised25 guinea pigs of male sex. The low cortisol level rapidly increase the overallhemolytic activity of the complements of the C1 est erase concentration. Along withthe cortisol dose increase the overall hemolytic complements' activity is dropping aswell as that of the C1, C2, C3 and C4 complements' components.

  8. Taking the trophic bypass: aquatic-terrestrial linkage reduces methylmercury in a terrestrial food web.

    Science.gov (United States)

    Bartrons, Mireia; Gratton, Claudio; Spiesman, Brian J; Vander Zanden, M Jake

    2015-01-01

    Ecosystems can be linked by the movement of matter and nutrients across habitat boundaries via aquatic insect emergence. Aquatic organisms tend to have higher concentrations of certain toxic contaminants such as methylmercury (MeHg) compared to their terrestrial counterparts. If aquatic organisms come to land, terrestrial organisms that consume them are expected to have elevated MeHg concentrations. But emergent aquatic insects could have other impacts as well, such as altering consumer trophic position or increasing ecosystem productivity as a result of nutrient inputs from insect carcasses. We measure MeHg in terrestrial arthropods at two lakes in northeastern Iceland and use carbon and nitrogen stable isotopes to quantify aquatic reliance and trophic position. Across all terrestrial focal arthropod taxa (Lycosidae, Linyphiidae, Acari, Opiliones), aquatic reliance had significant direct and indirect (via changes in trophic position) effects on terrestrial consumer MeHg. However, contrary to our expectations, terrestrial consumers that consumed aquatic prey had lower MeHg concentrations than consumers that ate mostly terrestrial prey. We hypothesize that this is due to the lower trophic position of consumers feeding directly on midges relative to those that fed mostly on terrestrial prey and that had, on average, higher trophic positions. Thus, direct consumption of aquatic inputs results in a trophic bypass that creates a shorter terrestrial food web and reduced biomagnification of MeHg across the food web. Our finding that MeHg was lower at terrestrial sites with aquatic inputs runs counter to the conventional wisdom that aquatic systems are a source of MeHg contamination to surrounding terrestrial ecosystems.

  9. [Trophic structure of river fish from Corral de San Luis, Magdalena river basin, Colombia Caribbean].

    Science.gov (United States)

    Morales, Jenny; García-Alzate, Carlos A

    2016-06-01

    Ecological studies of species, such as the stomach content analysis, allow us to recognize different trophic groups, the importance of trophic levels and the interrelationships among species and other members of the community. In this investigation, we studied food habits, feeding variation and trophic relationships of the fishes present in streams of the Corral de San Luis drainage, Tubará, Atlántico Department, a part of the lower Magdalena River Basin in Colombian Caribbean. Fish samples of Awaous banana, Agonostomus monticola, Andinoacara latifrons, Hyphessobrycon proteus, Poecilia gillii, Gobiomorus dormitor and Synbranchus marmoratus were obtained using a seine (2x5 m, mesh 0.5 cm), from November 2012 to October 2013. To analyze their stomach contents, we used numeric (% N), volumetric (% V) and frequency of occurrence (% FO) methods, an emptiness coefficient (C.V), index of food item importance (I.A). Besides, physical and chemical habitat parameters were recorded on site. Information obtained was processed using multivariate statistical analysis, ecological indices, and null models: canonical correspondence analysis (CCA), principal component analysis (PCA), trophic niche amplitude (Shannon-Weaver H´) and trophic overlap (Morisita-Horn). We observed significant differences on food resources consumption (K-W= 20.86; ptrophic axis, with respect to shared food items, and that the segregation was not influenced or generated by competition. The Morisita-Horn index showed false trophic overlap (similarity of about 80 %) between A. banana and P. gillii. The first component of the PCA analysis was explained mainly by phytoplankton, and component two was correlated with items of animal origin. The fishes associated with PC1 were P. gillii and A. banana, with high ingestion values of microalgae. PC2 was explained by A. monticola with high numbers of food items of animal origin. The group of fishes studied behaved as an assemblage; given that the trophic

  10. Climate change could drive marine food web collapse through altered trophic flows and cyanobacterial proliferation.

    Science.gov (United States)

    Ullah, Hadayet; Nagelkerken, Ivan; Goldenberg, Silvan U; Fordham, Damien A

    2018-01-01

    Global warming and ocean acidification are forecast to exert significant impacts on marine ecosystems worldwide. However, most of these projections are based on ecological proxies or experiments on single species or simplified food webs. How energy fluxes are likely to change in marine food webs in response to future climates remains unclear, hampering forecasts of ecosystem functioning. Using a sophisticated mesocosm experiment, we model energy flows through a species-rich multilevel food web, with live habitats, natural abiotic variability, and the potential for intra- and intergenerational adaptation. We show experimentally that the combined stress of acidification and warming reduced energy flows from the first trophic level (primary producers and detritus) to the second (herbivores), and from the second to the third trophic level (carnivores). Warming in isolation also reduced the energy flow from herbivores to carnivores, the efficiency of energy transfer from primary producers and detritus to herbivores and detritivores, and the living biomass of detritivores, herbivores, and carnivores. Whilst warming and acidification jointly boosted primary producer biomass through an expansion of cyanobacteria, this biomass was converted to detritus rather than to biomass at higher trophic levels-i.e., production was constrained to the base of the food web. In contrast, ocean acidification affected the food web positively by enhancing trophic flow from detritus and primary producers to herbivores, and by increasing the biomass of carnivores. Our results show how future climate change can potentially weaken marine food webs through reduced energy flow to higher trophic levels and a shift towards a more detritus-based system, leading to food web simplification and altered producer-consumer dynamics, both of which have important implications for the structuring of benthic communities.

  11. CO2-level Dependent Effects of Ocean Acidification on Squid, Doryteuthis pealeii, Early Life History

    KAUST Repository

    Zakroff, Casey J.

    2013-12-01

    Ocean acidification is predicted to lead to global oceanic decreases in pH of up to 0.3 units within the next 100 years. However, those levels are already being reached currently in coastal regions due to natural CO2 variability. Squid are a vital component of the pelagic ecosystem, holding a unique niche as a highly active predatory invertebrate and major prey stock for upper trophic levels. This study examined the effects of a range of ocean acidification regimes on the early life history of a coastal squid species, the Atlantic longfin squid, Doryteuthis pealeii. Eggs were raised in a flow-through ocean acidification system at CO2 levels ranging from ambient (400ppm) to 2200ppm. Time to hatching, hatching efficiency, and hatchling mantle lengths, yolk sac sizes, and statoliths were all examined to elucidate stress effects. Delays in hatching time of at least a day were seen at exposures above 1300ppm in all trials under controlled conditions. Mantle lengths were significantly reduced at exposures above 1300 ppm. Yolk sac sizes varied between CO2 treatments, but no distinct pattern emerged. Statoliths were increasingly porous and malformed as CO2 exposures increased, and were significantly reduced in surface area at exposures above 1300ppm. Doryteuthis pealeii appears to be able to withstand acidosis stress without major effects up to 1300ppm, but is strongly impacted past that threshold. Since yolk consumption did not vary among treatments, it appears that during its early life stages, D. pealeii reallocates its available energy budget away from somatic growth and system development in order to mitigate the stress of acidosis.

  12. Implementation of the ecotoxicological, effects module

    DEFF Research Database (Denmark)

    Larsen, Henrik Fred; Payet, Jerome; Molander, S

    for each trophic level (GM-trophic-levels). The GM-trophic-levels is calculated as the geometric mean of the geometric means at the genus level (GM-genuses) which again are calculated as the geometric means of the geometric means at species level (GM-species). GM-species is calculated as the geometric mean...... mean). As a starting point existing approaches used within LCIA has been described and evaluated. Reports on these two issues (estimation principle and evaluation of existing approaches) are enclosed with this report as possible sources for background information In this report further theoretical...... elaboration of effect based average approaches (arithmetic mean, geometric mean and median) and the non-effect based approach (PNEC, here only as lowest EC50 in the dataset) are done focusing on their statistical robustness and the possibility to relate the effect indicator (based on a measure of effect...

  13. 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≤TL<3 and 3≤TL<4 have a range of ecotropic efficiency from 0 to 0.9719 and 0 to 0.7520 respectively.The Mean transfer efficiency is 9.43% for phytoplankton and 3.39% for detritus. The Mixed trophic impact analysis indicates that phytoplankton havea positive impact on the majority of pelagic fish, 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.

  14. Interleukin-1 primes human mesenchymal stem cells towards an anti-inflammatory and pro-trophic phenotype in vitro.

    Science.gov (United States)

    Redondo-Castro, Elena; Cunningham, Catriona; Miller, Jonjo; Martuscelli, Licia; Aoulad-Ali, Sarah; Rothwell, Nancy J; Kielty, Cay M; Allan, Stuart M; Pinteaux, Emmanuel

    2017-04-17

    Inflammation is a key contributor to central nervous system (CNS) injury such as stroke, and is a major target for therapeutic intervention. Effective treatments for CNS injuries are limited and applicable to only a minority of patients. Stem cell-based therapies are increasingly considered for the treatment of CNS disease, because they can be used as in-situ regulators of inflammation, and improve tissue repair and recovery. One promising option is the use of bone marrow-derived mesenchymal stem cells (MSCs), which can secrete anti-inflammatory and trophic factors, can migrate towards inflamed and injured sites or can be implanted locally. Here we tested the hypothesis that pre-treatment with inflammatory cytokines can prime MSCs towards an anti-inflammatory and pro-trophic phenotype in vitro. Human MSCs from three different donors were cultured in vitro and treated with inflammatory mediators as follows: interleukin (IL)-1α, IL-1β, tumour necrosis factor alpha (TNF-α) or interferon-γ. After 24 h of treatment, cell supernatants were analysed by ELISA for expression of granulocyte-colony stimulating factor (G-CSF), IL-10, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), IL-1 receptor antagonist (IL-1Ra) and vascular endothelial growth factor (VEGF). To confirm the anti-inflammatory potential of MSCs, immortalised mouse microglial BV2 cells were treated with bacterial lipopolysaccharide (LPS) and exposed to conditioned media (CM) of naïve or IL-1-primed MSCs, and levels of secreted microglial-derived inflammatory mediators including TNF-α, IL-10, G-CSF and IL-6 were measured by ELISA. Unstimulated MSCs constitutively expressed anti-inflammatory cytokines and trophic factors (IL-10, VEGF, BDNF, G-CSF, NGF and IL-1Ra). MSCs primed with IL-1α or IL-1β showed increased secretion of G-CSF, which was blocked by IL-1Ra. Furthermore, LPS-treated BV2 cells secreted less inflammatory and apoptotic markers, and showed increased secretion of the

  15. Interacting trophic forcing and the population dynamics of herring

    DEFF Research Database (Denmark)

    Lindegren, Martin; Ostman, Orjan; Gardmark, Anna

    2011-01-01

    . Using a statistical, age-structured modeling approach, we demonstrate the relative importance and influence of bottom-up (e.g., climate, zooplankton availability) and top-down (i.e., fishing and predation) factors on the population dynamics of Bothnian Sea herring (Clupea harengus) throughout its life......Small pelagic fish occupy a central position in marine ecosystems worldwide, largely by determining the energy transfer from lower trophic levels to predators at the top of the food web, including humans. Population dynamics of small pelagic fish may therefore be regulated neither strictly bottom......-up nor top-down, but rather through multiple external and internal drivers. While in many studies single drivers have been identified, potential synergies of multiple factors, as well as their relative importance in regulating population dynamics of small pelagic fish, is a largely unresolved issue...

  16. Effects of grazing management on biodiversity across trophic levels – The importance of livestock species and stocking density in salt marshes

    NARCIS (Netherlands)

    Klink, van Roel; Nolte, Stefanie; Mandema, Freek S.; Lagendijk, D.D.G.; Wallis de Vries, Michiel; Bakker, Jan P.; Esselink, Peter; Smit, Christian

    2016-01-01

    European coastal salt marshes are important for the conservation of numerous species of specialist plants, invertebrates, breeding and migratory birds. When these marshes are managed for nature conservation purposes, livestock grazing is often used to counter the dominance of the tall grass

  17. Effects of grazing management on biodiversity across trophic levels-The importance of livestock species and stocking density in salt marshes

    NARCIS (Netherlands)

    van Klink, Roel; Nolte, Stefanie; Mandema, Freek; Lagendijk, D. D. Georgette; WallisDeVries, Michiel F.; Bakker, Jan P.; Esselink, Peter; Smit, Christian

    2016-01-01

    European coastal salt marshes are important for the conservation of numerous species of specialist plants, invertebrates, breeding and migratory birds. When these marshes are managed for nature conservation purposes, livestock grazing is often used to counter the dominance of the tall grass

  18. Effects of long-term crop management on nematode trophic levels other than plant feeders disappear after 1 year of disruptive soil management

    NARCIS (Netherlands)

    Berkelmans, R.A.; Ferris, H.; Tenuta, M.; Bruggen, van A.H.C.

    2003-01-01

    Nematode community analysis may provide a useful tool to quantify soil health. Nematode communities were monitored for 5 years during a 12-year period in the sustainable agriculture fanning systems (SAFS) project at UC Davis, where conventional (CONV), low-input (LOW) and organic (ORG) management

  19. Effect of trophic level on the radiocesium frequency distribution in aquatic and terrestrial ecosystems at Chornobyl and nuclear sites in the United States

    International Nuclear Information System (INIS)

    Smith, Michael H.; Tsyusko-Omeltchenko, Olga; Oleksyk, Taras K.

    2003-01-01

    There are significant linear relationship between the standard deviation and the mean of radiocesium concentration for samples of soils, sediments, plants, and animals from Chornobyl and nuclear sites in the United States. The universal occurrence of this relationship in all types of samples suggests that a non-normal frequency distribution should be expected. The slopes of these relationships are similar for fish and mammals from the two regions of the world but those for plants are not. The slopes for plants are similar for aquatic and terrestrial ecosystems within each region. We hypothesize that there are relationships between the four moments of the frequency distribution of radiocesium (mean, variance, skewness, and kurtosis), and that these relationships are caused by the functional properties of the organisms and other characteristics of the ecosystem. The way in which radiocesium was distributed across the landscape does not seem to be a factor in determining the form of the frequency distribution. (author)

  20. Caracterización trófica del placóforo intermareal Enoplochiton niger en el norte de Chile: variación ambiental y patrones dietarios a nivel local y region Trophic characterization of the intertidal placophoran Enoplochiton niger in northern Chile: environmental variation and dietary patterns at local and regional levels

    Directory of Open Access Journals (Sweden)

    ALVARO G SANHUEZA

    2008-12-01

    .The role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the placophoran mollusc Enoplochiton niger. This species is one of the largest (up to 20 cm and ecologically most important grazers on rocky shores of northern Chile, but also one of the lesser known species in trophic terms. This work presents an assessment of the dietary patterns of E. niger in four communities of northern Chile, distributed along 1,000 km of coastline and sampled seasonally from winter 2004 to autumn 2006. The analysis included the relationship of its diet with physical and biological factors, and particularly the potential effect of the 2004-2005 El Niño event that occurred during the study period. At a regional level, the dietary spectrum of E. niger comprised a total of 98 food resources (60 algal Ítems and 38 invertebrate Ítems, and the most important Ítems were sessile organisms of encrusting and layer-forming growth habits. E. niger exhibited a very high niche breadth at both local and regional levels (ranging from 20.7 to 28.0; Levins' index, and its dietary richness at the individual level was independent from its body size. Both the number of dietary ítems consumed per individual and the taxonomic composition of the diet did not show statistical differences among communities, but they were significantly different between the El Niño and non-El Niño periods. There was no clear relationship between the dietary patterns of E. niger and the contrasting levels of upwelling intensity among the communities studied. The results show that E. niger is a generalist polyphagous consumer, and a potential omnivore, which could have a high level of impact on space occupancy patterns in the intertidal community.

  1. Trophic dynamics influence climate at high latitudes

    Science.gov (United States)

    Oksanen, L.; Tuomi, M.; Hoset, K.; Oksanen, T.; Olofsson, J.; Dahlgren, J.; Nordic Center of Excellence-Tundra

    2011-12-01

    Abundance relationships between tall woody plants and low herbaceous plants influence ground albedo. Increasing abundance of erect woody plants on the tundra increase the amount of solar energy converted to heat, thus speeding up global warming. By transplanting vegetation blocks from an island with predatory mammals and gray-sided voles (Myodes rufocanus) to similar habitats on islands with gray-sided voles but no resident predators and to islands with neither voles nor predators, we show that changing trophic dynamics radically change the abundance relationships between woody and herbaceous plants. Impacts of food limited gray-sided voles result to devastation of all erect woody plants, regardless of their palatability, thus differing both quantitatively and qualitatively from the selective impacts of the same species in the presence of predators. The shift from vegetation dominated by erect woody plants to vegetation dominated by herbs or trailing dwarf shrubs also increases ground albedo. The relationship between climate and trophic dynamics is thus no one way street. Rather than responding passively to changes in climate, food webs can also influence climate via their impacts on ground albedo.

  2. Trophic State and Oxygen Conditions of Waters Aerated with Pulverising Aerator: The Results from Seven Lakes in Poland

    Directory of Open Access Journals (Sweden)

    Hanna Siwek

    2018-02-01

    Full Text Available Eutrophic lakes of all types are marked by oxygen shortage in the bottom waters during the summer season, which results in excessive release of phosphorus load. Therefore, numerous restoration activities (chemical precipitation, aeration are being taken based on bottom-up control, which consists of limiting the nutrient pool available to lower trophic levels. The present study provides an efficiency analysis of pulverising aeration of waters in two stratified and five unstratified lakes located in Poland. The assessment was based on monitoring data (dissolved oxygen concentration (DO, % oxygen saturation (DO%, visibility of the Secchi disc (ZSD, the concentrations of: chlorophyll a (CHL, total phosphorus (TP and total nitrogen (TN obtained before and after installation of the aerator on the lakes. The study was conducted during the spring and the summer seasons. Throughout the study period, the stratified lakes exhibited oxygen saturation <0.1%. Having completed the restoration activities, TN:TP ratio was found to gradually increase in all analysed lakes, which indicates that aeration may decrease phosphate content in the water column. In three lakes, the ratio was > 17, so phosphorus became the most growth-limiting nutrient. The restoration activities on four unstratified lakes had no significant effect on the changes of the Carlson trophic state indices (TSI. Either individual values of the TSI(TP, TSI(CHL and TSI(ZSD were comparable, or the value of TSI(TP was higher than one or both of the remaining indices for all of the lakes.

  3. Trophic structure in a seabird host-parasite food web: insights from stable isotope analyses.

    Directory of Open Access Journals (Sweden)

    Elena Gómez-Díaz

    2010-05-01

    Full Text Available Ecological studies on food webs rarely include parasites, partly due to the complexity and dimensionality of host-parasite interaction networks. Multiple co-occurring parasites can show different feeding strategies and thus lead to complex and cryptic trophic relationships, which are often difficult to disentangle by traditional methods. We analyzed stable isotope ratios of C ((13C/(12C, delta(13C and N ((15N/(14N, delta(15N of host and ectoparasite tissues to investigate trophic structure in 4 co-occurring ectoparasites: three lice and one flea species, on two closely related and spatially segregated seabird hosts (Calonectris shearwaters. delta(13C isotopic signatures confirmed feathers as the main food resource for the three lice species and blood for the flea species. All ectoparasite species showed a significant enrichment in delta(15N relatively to the host tissue consumed (discrimination factors ranged from 2 to 5 per thousand depending on the species. Isotopic differences were consistent across multiple host-ectoparasite locations, despite of some geographic variability in baseline isotopic levels. Our findings illustrate the influence of both ectoparasite and host trophic ecology in the isotopic structuring of the Calonectris ectoparasite community. This study highlights the potential of stable isotope analyses in disentangling the nature and complexity of trophic relationships in symbiotic systems.

  4. The Trophic Status of the Lubuk Lampam Floodplain in South Sumatera, Indonesia

    Directory of Open Access Journals (Sweden)

    Dade Jubaedah

    2016-06-01

    Full Text Available The Lubuk Lampam floodplain’s ecosystem is naturally affected by the fluctuation of the water surface. This ecosystem also receives anthropogenic substances such as nutrients and other chemicals, especially from the oil palm plantation and its industrial processing activities. The main objective of this research was to determine the trophic status of the floodplain using the trophic level index (TLI and Carlson’s trophic state index (TSI. The water quality and the fish samples were collected and analyzed from 7 stations representing various types of floodplain habitat. The results showed that the trophic status of Lubuk Lampam was hypereutrophic (very nutrient-rich. This was also supported by the high increase of the body weight (“b” value more than 3 and the high gonadosomatic index (GSI of the studied fishes, i.e. Osteochilus vittatus 2.53-6.81% (male and 3.00-15.86% (female; Helostoma temminckii 0.28-3.33% (male and 1.30-10.43% (female; and Channa striata 0.33-0.59% (male and 0.21-2.73% (female.

  5. Zooplankton-based assessment of the trophic state of a tropical forest river in Nigeria

    Directory of Open Access Journals (Sweden)

    Imoobe T.O.T.

    2009-01-01

    Full Text Available In this study, we explore the usefulness of zooplankton as a tool for assessing the trophic status of a Nigerian forest river. The river was sampled monthly and investigated for water physico-chemistry and zooplankton community structure using basic statistical measurement of diversity indices to characterize the zooplankton fauna. The trophic sta­tus of the river evaluated from its physico-chemical parameters indicates that the river is oligotrophic. The zooplankton composition was typical of a tropical freshwater river, with a total of 40 species, made up of 16 rotifers, 12 cladocerans, and 12 copepods and their developing stages in the following order of dominance: Rotifera > Cladocera > Cyclopoida > Calanoida. There were strong correlations between the lake's trophic status and its zooplankton communities. The zoo­plankton community was dominated by numerous species of rotifers and crustaceans, which are typical of oligotrophic to mesotrophic systems, such species including Conochilus dossuarius and Synchaeta longipes. However, the most dominant zooplankton species in West African freshwater ecosystems, viz., Keratella tropica, Keratella quadrata, Brachionus angularis, Trichocerca pusilla, Filinia longiseta, Pompholyx sulcata, and Proales sp., and others that are indicator species of high trophic levels, were not recorded in the river. The river is very clear and can be used for all manner of recreational activities.

  6. Trophic Niche in a Raptor Species: The Relationship between Diet Diversity, Habitat Diversity and Territory Quality.

    Directory of Open Access Journals (Sweden)

    Juan Navarro-López

    Full Text Available Recent research reports that many populations of species showing a wide trophic niche (generalists are made up of both generalist individuals and individuals with a narrow trophic niche (specialists, suggesting trophic specializations at an individual level. If true, foraging strategies should be associated with individual quality and fitness. Optimal foraging theory predicts that individuals will select the most favourable habitats for feeding. In addition, the "landscape heterogeneity hypothesis" predicts a higher number of species in more diverse landscapes. Thus, it can be predicted that individuals with a wider realized trophic niche should have foraging territories with greater habitat diversity, suggesting that foraging strategies, territory quality and habitat diversity are inter-correlated. This was tested for a population of common kestrels Falco tinnunculus. Diet diversity, territory occupancy (as a measure of territory quality and habitat diversity of territories were measured over an 8-year period. Our results show that: 1 territory quality was quadratically correlated with habitat diversity, with the best territories being the least and most diverse; 2 diet diversity was not correlated with territory quality; and 3 diet diversity was negatively correlated with landscape heterogeneity. Our study suggests that niche generalist foraging strategies are based on an active search for different prey species within or between habitats rather than on the selection of territories with high habitat diversity.

  7. Pressure-Induced Shifts in Trophic Linkages in a Simplified Aquatic Food Web

    Directory of Open Access Journals (Sweden)

    Maarten Schrama

    2017-12-01

    Full Text Available It is essential to understand effects of existing and emerging anthropogenic stressors on the structure of aquatic food webs in more natural settings, to obtain realistic predictions on how they can affect major ecosystem properties and functioning. We therefore examined whether (1 realistic concentrations of key agricultural pesticides and nutrients induce shifts in trophic linkages (2 observed changes in trophic linkages are qualitatively different between the green (algal-based and brown (detritus-based part of the food web. To this end, we exposed a simplified, yet realistic freshwater invertebrate community to environmentally relevant concentrations of three anthropogenic pressures (eutrophication; the herbicide terbuthylazine; and the insecticide imidacloprid in a full factorial mesocosm design. Trophic linkages and the changes therein were assessed measuring stable isotopes of natural carbon and nitrogen. Results show that the green and brown part of the food web react qualitatively different to interacting pressures. Whereas, herbivorous species react mainly to the nutrients and herbicides and the synergistic interaction between these, species in the detritivore part of the food web were affected by insecticide applications and interactions with nutrients. These results suggest that agricultural pressures can induce shifts in trophic linkages, but that they can have contrasting effects on the different parts of the food web. Such antagonistic and synergistic interactions can provide powerful explanations for observed responses of ecosystems to interacting stressors. These findings may have important implications for our understanding on interactions of agricultural stressors and their propagation in aquatic food webs.

  8. Trophic and environmental drivers of the Sechura Bay Ecosystem (Peru) over an ENSO cycle

    Science.gov (United States)

    Taylor, Marc H.; Wolff, Matthias; Vadas, Flora; Yamashiro, Carmen

    2008-03-01

    Interannual environmental variability in Peru is dominated by the El Niño Southern Oscillation (ENSO). The most dramatic changes are associated with the warm El Niño (EN) phase (opposite the cold La Niña phase), which disrupts the normal coastal upwelling and affects the dynamics of many coastal marine and terrestrial resources. This study presents a trophic model for Sechura Bay, located at the northern extension of the Peruvian upwelling system, where ENSO-induced environmental variability is most extreme. Using an initial steady-state model for the year 1996, we explore the dynamics of the ecosystem through the year 2003 (including the strong EN of 1997/98 and the weaker EN of 2002/03). Based on support from literature, we force biomass of several non-trophically-mediated ‘drivers’ (e.g. Scallops, Benthic detritivores, Octopus, and Littoral fish) to observe whether the fit between historical and simulated changes (by the trophic model) is improved. The results indicate that the Sechura Bay Ecosystem is a relatively inefficient system from a community energetics point of view, likely due to the periodic perturbations of ENSO. A combination of high system productivity and low trophic level target species of invertebrates (i.e. scallops) and fish (i.e. anchoveta) results in high catches and an efficient fishery. The importance of environmental drivers is suggested, given the relatively small improvements in the fit of the simulation with the addition of trophic drivers on remaining functional groups’ dynamics. An additional multivariate regression model is presented for the scallop Argopecten purpuratus, which demonstrates a significant correlation between both spawning stock size and riverine discharge-mediated mortality on catch levels. These results are discussed in the context of the appropriateness of trophodynamic modeling in relatively open systems, and how management strategies may be focused given the highly environmentally influenced marine

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

    Science.gov (United States)

    Galetti, Mauro; Rodarte, Raisa Reis; Neves, Carolina Lima; Moreira, Marcelo; Costa-Pereira, Raul

    2016-01-01

    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.

  10. 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.

  11. Trophic niche-space imaging, using resource and consumer traits

    NARCIS (Netherlands)

    Nagelkerke, L.A.J.; Rossberg, A.G.

    2014-01-01

    The strength of trophic (feeding) links between two species depends on the traits of both the consumer and the resource. But which traits of consumer and resource have to be measured to predict link strengths, and how many? A novel theoretical framework for systematically determining trophic traits

  12. 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...

  13. 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, ...

  14. 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

  15. 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

    .2) indicating carnivory, while T. inermis (TP = 2.4 ± 0.3) had a more omnivorous diet. In turn, T. longicaudata and T. raschii (TP = 2.2 ± 0.2) were herbivorous. Along the fjord, nutrient and plankton composition affected trophic position. Thysanoessa longicaudata was more omnivorous offshore than inshore where......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...... and Meganyctiphanes norvegica sampled in June 2010 in the Godthåbsfjord, SW Greenland revealed new insight into their trophic roles and positions. There was a general positive correlation between body length and trophic position. The largest species M. norvegica had the highest trophic position (TP = 2.8 ± 0...

  16. 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.

  17. 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.

  18. The ecological role of overwintering fish in the food web of the Culbin Sands lagoon ecosystem, NE Scotland: Identifying major trophic links and testing effects of the fish Pomatoschistus microps (Pallas on benthic invertebrates

    Directory of Open Access Journals (Sweden)

    Vanda Mariyam Mendonça

    2007-12-01

    Full Text Available The Culbin Sands lagoon ecosystem in NE Scotland was studied during a three-year period (1994-1996 to identify the major trophic links from benthic invertebrates to epibenthic predators, and to assess impacts of overwintering fish on their prey communities. Every 2-4 weeks, samples of mobile fauna were collected to study their diets. The major trophic links identified between benthic invertebrates and epibenthic predators were from benthic invertebrates to the shrimp Crangon crangon, and to the common goby Pomatoschistus microps and the plaice Pleuronectes platessa. The energy flow from benthic invertebrates to overwintering fish was estimated at 133 kJ m–2 yr–1. A flow of 10 kJ m–2 yr–1 was also observed from eggs and larval stages of the overwintering shrimp Crangon crangon to the overwintering fish. Nevertheless, manipulative field experiments showed no significant impacts of the most abundant overwintering fish Pomatoschistus microps on prey community densities, despite an overall individual ingestion rate of 89 J day–1.

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

    OpenAIRE

    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 kn...

  20. 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

  1. Bioaccumulation and trophic transfer of polybrominated diphenyl ethers (PBDEs) in a marine food web from Liaodong Bay, North China

    International Nuclear Information System (INIS)

    Ma, Xindong; Zhang, Haijun; Yao, Ziwei; Zhao, Xiaofeng; Wang, Longxing; Wang, Zhen; Chen, Jiping; Chen, Jingwen

    2013-01-01

    Highlights: • BDE-47 was the dominating congener in organisms of the Liaodong Bay. • The length of food chain played an important role on the TMFs. • PBDEs were steadily metabolized in the trophic transfer process along the food chain. -- Abstract: The concentrations of 21 polybrominated diphenyl ethers (PBDEs) congeners were analyzed in organisms within a marine food web collected from the Liaodong Bay, North China. The total concentrations of PBDEs in all samples ranged from 0.87 to 91.4 ng g −1 lipid weight (lw). BDE-47 was the predominant congener and had a concentration ranging from 0.30 to 36.1 ng g −1 lw. The trophic magnification factors (TMF) of the PBDEs were calculated using the trophic levels obtained from the stable nitrogen isotope ratios. The TMF value of ∑PBDEs was 3.50 for the entire food web and 2.21 for the food web excluding seabirds. Four concentration ratios, BDE-99/BDE-100, BDE-99/BDE-47, BDE-153/BDE-154 and BDE-183/BDE-154, decreased linearly with the increase of the trophic levels in the invertebrates and the fishes (p < 0.01). The results suggested that the PBDEs were steadily metabolized in the trophic transfer process along the food chain

  2. 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.

  3. Mercury bioaccumulation in fish of commercial importance from different trophic categories in an Amazon floodplain lake

    Directory of Open Access Journals (Sweden)

    Sandra Beltran-Pedreros

    Full Text Available Thirty-two species of commercially important fish from three trophic levels and nine trophic categories were sampled at a floodplain lake of the Solimões River (Lago Grande de Manacapuru. The fish were analyzed to determine their Hg level and the bioaccumulation, bioconcentration, and biomagnification of this element. The observed increase in mean concentration of mercury (49.6 ng.g-1 for omnivores, 418.3 ng.g-1 for piscivores, and 527.8 ng.g-1 for carnivores/necrophages furnished evidence of biomagnification. Primary, secondary, and tertiary consumers presented biomagnification factors of 0.27, 0.33, and 0.47, respectively. Significant differences in the bioconcentration and concentration of total Hg occurred between the categories of the third trophic level and the other categories. Plagioscion squamosissimus (carnivorous/piscivorous and Calophysus macropterus (carnivorous/ necrophagous showed levels of total Hg above those permitted by Brazilian law (500 ng.g-1. Six other species also posed risks to human health because their Hg levels exceeded 300 ng.g-1. Fifteen species showed bioaccumulation, but only eight presented significant correlations between the concentration of Hg and the length and/or the weight of the fish.

  4. 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;}

  5. Plant toxins and trophic cascades alter fire regime and succession on a boral forest landscape

    Science.gov (United States)

    Feng, Zhilan; Alfaro-Murillo, Jorge A.; DeAngelis, Donald L.; Schmidt, Jennifer; Barga, Matthew; Zheng, Yiqiang; Ahmad Tamrin, Muhammad Hanis B.; Olson, Mark; Glaser, Tim; Kielland, Knut; Chapin, F. Stuart; Bryant, John

    2012-01-01

    Two models were integrated in order to study the effect of plant toxicity and a trophic cascade on forest succession and fire patterns across a boreal landscape in central Alaska. One of the models, ALFRESCO, is a cellular automata model that stochastically simulates transitions from spruce dominated 1 km2 spatial cells to deciduous woody vegetation based on stochastic fires, and from deciduous woody vegetation to spruce based on age of the cell with some stochastic variation. The other model, the ‘toxin-dependent functional response’ model (TDFRM) simulates woody vegetation types with different levels of toxicity, an herbivore browser (moose) that can forage selectively on these types, and a carnivore (wolf) that preys on the herbivore. Here we replace the simple succession rules in each ALFRESCO cell by plant–herbivore–carnivore dynamics from TDFRM. The central hypothesis tested in the integrated model is that the herbivore, by feeding selectively on low-toxicity deciduous woody vegetation, speeds succession towards high-toxicity evergreens, like spruce. Wolves, by keeping moose populations down, can help slow the succession. Our results confirmed this hypothesis for the model calibrated to the Tanana floodplain of Alaska. We used the model to estimate the effects of different levels of wolf control. Simulations indicated that management reductions in wolf densities could reduce the mean time to transition from deciduous to spruce by more than 15 years, thereby increasing landscape flammability. The integrated model can be useful in estimating ecosystem impacts of wolf control and moose harvesting in central Alaska.

  6. 2015 status of the Lake Ontario lower trophic levels

    Science.gov (United States)

    Holeck, Kristen T.; Rudstam, Lars G.; Hotaling, Christopher; McCullough, Russ D.; Lemon, Dave; Pearsall, Web; Lantry, Jana; Connerton, Michael J.; LaPan, Steve; Biesinger, Zy; Lantry, Brian F.; Walsh, Maureen; Weidel, Brian C.

    2016-01-01

    Offshore spring total phosphorus (TP) in 2015 was 4.2 μ g/L, the same as in 2014; this is lower than 2001 - 2013, but there is no significant time trend 2001 - 2015. Offshore soluble reactive phosphorus (SRP) was very low in 2015; Apr/May - Oct mean values were water column samples taken show a stable zooplankton biomass but changing community composition since 2010. Cyclopoids increased 2013 - 2015 and daphnids declined 2014 - 2015.

  7. Effects of enerry level on growth and

    African Journals Online (AJOL)

    all low levels constituted similar ME intakes. The dietary ingredients and composition are shown in Table 1. Intake and live mass were recorded weekly and body composition, in terms of chemically determined constituents and consti- tuents of the consumable carcass, was determined at the slaughter masses of 245 (1), 350 ...

  8. 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.

  9. 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

  10. 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...

  11. 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

  12. 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

  13. 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.

  14. Health effects of low level radiation

    International Nuclear Information System (INIS)

    Chevillard, S.; Ugolin, N.; Lebeau, J.; Ory, K.

    2006-01-01

    Nuclear energy production is necessarily associated with the handling and storage of radioactive elements, which are liable to have deleterious effects on human health, and on environment. These deleterious effects are varied, but they greatly depend on the dose, which has been received, and the exposure type. Therefore, only intense and massive exposures are liable to be clinically detected. They can entail immediate consequences, even lead to the person's death. Thanks to safety measures, which have been implemented to an international scale, this occurs very rarely. Excluding extensive accidental cases, medical irradiation for therapeutic use and conflicts, workers and population in general are exposed to low doses and low dose-rates. Low dose exposures, resulting from either a contamination or an external irradiation are more frequent. In fact, we could say that the whole humanity is concerned by natural exposure, which varies depending on regions, as well as by medical exposure, which varies depending on the medicalisation status of the country. (author)

  15. Multivariate Term Structure Models with Level and Heteroskedasticity Effects

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    2005-01-01

    The paper introduces and estimates a multivariate level-GARCH model for the long rate and the term-structure spread where the conditional volatility is proportional to the ãth power of the variable itself (level effects) and the conditional covariance matrix evolves according to a multivariate GA...... and the level model. GARCH effects are more important than level effects. The results are robust to the maturity of the interest rates. Udgivelsesdato: MAY...

  16. Science for a wilder Anthropocene : Synthesis and future directions for trophic rewilding research

    NARCIS (Netherlands)

    Svenning, Jens Christian; Pedersen, Pil B M; Donlan, C. Josh; Ejrnæs, Rasmus; Faurby, Søren; Galetti, Mauro; Hansen, Dennis M.; Sandel, Brody; Sandom, Christopher J.; Terborgh, John W.; Vera, Frans W M

    2016-01-01

    Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and

  17. Spatial variations in the trophic structure of soil animal communities in boreal forests of Pechora-Ilych Nature Reserve

    Science.gov (United States)

    Goncharov, A. A.; Khramova, E. Yu.; Tiunov, A. V.

    2014-05-01

    Soil animal communities and detrital food webs are spatially compartmentalized. In old-growth boreal forests the dynamics of dominating plant species forms a considerable heterogeneity of edaphic conditions in the soil layer. We demonstrate a strong difference in total and relative abundance of main trophic groups of soil macrofauna in four microsites, i.e. under tree crowns, in gaps, in mounds and in pits created by fallen spruce trees. The variation in the functional structure of soil animal communities is likely related to different availability of key energy resources (leaf litter, roots and root deposits) in the microsites studied. However, results of the stable isotope analysis suggest that mobile litter-dwelling predators occupy very similar trophic positions in different microsites. The compartmentalization of soil invertebrate communities caused by the vegetation-induced mosaic of edaphic conditions seemingly does not lead to spatial isolation of local food webs that are integrated at the top trophic levels.

  18. Spatial variation in the stable isotopes of 13C and 15N and trophic position of Leporinus friderici (Characiformes, Anostomidae) in Corumbá Reservoir, Brazil.

    Science.gov (United States)

    Pereira, Alexandre L; Benedito, Evanilde; Sakuragui, Cássia M

    2007-03-01

    Stable isotopes of carbon (delta13C) and nitrogen (delta15N) were used to describe sources of energy and trophic position for adult Leporinus friderici in the area of the Corumbá Reservoir, Brazil. Samples were collected from April 1999 to March 2000. Spatial variations were not identified in the isotopic composition. The maximum and minimum contribution of C4 plants calculated integrating the variation of plants and fish were 47.7% and 2.4%, respectively. Among C3 plants, periphyton presented closer isotopic values to those observed for fishes, corresponding to an important carbon source. The proportion of ingested plant item is larger in rivers upstream from the reservoir (42.7%), which justifies the smaller trophic level among there. However, in the reservoir, the ingestion of fish was 81.4%, while ingested plants contributed with 18.6%. Downstream from the dam, participation of plant item was even smaller (14.4%). Although the trophic position calculated with diet data was proportional to the one calculated with delta15N values, the former elevated the trophic level of L. friderici in the food web, because estimated trophic positions were based on fish items belonging to the 2nd (a) and to the 3rd (b) trophic levels.

  19. Genetic effects of low-level irradiation

    International Nuclear Information System (INIS)

    Selby, P.B.

    1980-01-01

    Recent estimates of the genetic effects of radiation by two widely recognized committees (BEIR III and UNSCEAR 1977) are based to a large extent on data collected in mice using either the specific-locus method or the approach of empirically determining the nature and extent of radiation-induced genetic damage to the skeleton. Both committees made use of doubling-dose and direct methods of estimating genetic hazard. Their estimates can be applied to assessments of risk resulting from medical irradiation in terms both of risk to the population at large and to the individual

  20. Assessing the contribution of marine protected areas to the trophic functioning of ecosystems: a model for the Banc d'Arguin and the Mauritanian shelf.

    Directory of Open Access Journals (Sweden)

    Sylvie Guénette

    Full Text Available Most modelling studies addressed the effectiveness of marine protected areas (MPA for fisheries sustainability through single species approach. Only a few models analysed the potential benefits of MPAs at the ecosystem level, estimating the potential export of fish biomass from the reserve or analysing the trophic relationships between organisms inside and outside the MPA. Here, we propose to use food web models to assess the contribution of a MPA to the trophic functioning of a larger ecosystem. This approach is applied to the Banc d'Arguin National Park, a large MPA located on the Mauritanian shelf. The ecosystem was modeled using Ecopath with Ecosim, a model that accounts for fisheries, food web structure, and some aspects of the spatial distribution of species, for the period 1991-2006. Gaps in knowledge and uncertainty were taken into account by building three different models. Results showed that the Banc d'Arguin contributes about 9 to 13% to the total consumption, is supporting about 23% of the total production and 18% of the total catch of the Mauritanian shelf ecosystem, and up to 50% for coastal fish. Of the 29 exploited groups, 15 depend on the Banc for more than 30% of their direct or indirect consumptions. Between 1991 and 2006, the fishing pressure increased leading to a decrease in biomass and the catch of high trophic levels, confirming their overall overexploitation. Ecosim simulations showed that adding a new fleet in the Banc d'Arguin would have large impacts on the species with a high reliance on the Banc for food, resulting in a 23% decrease in the current outside MPA catches. We conclude on the usefulness of food web models to assess MPAs contribution to larger ecosystem functioning.

  1. Trophic cascades of bottom-up and top-down forcing on nutrients and plankton in the Kattegat, evaluated by modelling

    Science.gov (United States)

    Petersen, Marcell Elo; Maar, Marie; Larsen, Janus; Møller, Eva Friis; Hansen, Per Juel

    2017-05-01

    The aim of the study was to investigate the relative importance of bottom-up and top-down forcing on trophic cascades in the pelagic food-web and the implications for water quality indicators (summer phytoplankton biomass and winter nutrients) in relation to management. The 3D ecological model ERGOM was validated and applied in a local set-up of the Kattegat, Denmark, using the off-line Flexsem framework. The model scenarios were conducted by changing the forcing by ± 20% of nutrient inputs (bottom-up) and mesozooplankton mortality (top-down), and both types of forcing combined. The model results showed that cascading effects operated differently depending on the forcing type. In the single-forcing bottom-up scenarios, the cascade directions were in the same direction as the forcing. For scenarios involving top-down, there was a skipped-level-transmission in the trophic responses that was either attenuated or amplified at different trophic levels. On a seasonal scale, bottom-up forcing showed strongest response during winter-spring for DIN and Chl a concentrations, whereas top-down forcing had the highest cascade strength during summer for Chl a concentrations and microzooplankton biomass. On annual basis, the system was more bottom-up than top-down controlled. Microzooplankton was found to play an important role in the pelagic food web as mediator of nutrient and energy fluxes. This study demonstrated that the best scenario for improved water quality was a combined reduction in nutrient input and mesozooplankton mortality calling for the need of an integrated management of marine areas exploited by human activities.

  2. Morphological Phytoplankton Groups and Trophic State of Topolobampo-Santa Maria-Ohuira, Sinaloa, México

    Science.gov (United States)

    Ayala, G.; Martínez-López, A.; Escobedo-Urías, D. C.

    2007-05-01

    Topolobampo-Santa Maria-Ohuira Lagoon Complex in the Gulf of California presents intense anthropogenic activities, such as agricultural with the drainage of nutrient enriched waters into the system, which affects on its health and integrity have been not evaluated before. Monthly data of physical-chemical variables and phytoplankton from November 2004 to February 2006 were used to define the actual trophic state of the lagoons by means of a trophic index (TRIX), and its imprint on the Morphological Phytoplankton Groups. From the analysis of data distinctive responses were observed for each lagoon. Trophic state and phytoplankton dynamic apparently were determinate by differences in hydrodynamics in each lagoon. Santa Maria lagoon showed higher trophic index values followed by Ohuira and Topolobampo. The phytoplankton community dominated for nannophytoplankton was regulated by nitrogen along the year in the entire lagoon system. However, the relationship between phytoplankton and physical-chemical variables examined by multivariate analysis indicated that in Santa Maria, nutrients from the runoff of fertilizers at the beginning of the fall/winter agriculture cycle influenced the occurrence of diatoms Harmful Algae Blooms (HABs), while in Ohuira higher water residence times have major regulatory effects on a large number of HABs of cyanobacteria and dinoflagellates and a lower Trophic state. A minor grade of affectation in Topolobampo lagoon is suggested by a dominance of the seasonality, a lower water residence times, and non HABs incidence during the period of this study.

  3. Determination of trophic situation of Sarimsakli Dam Lake (Kayseri ...

    African Journals Online (AJOL)

    msakl. Dam Lake from May 2001 to June 2002 monthly to determine the trophic situation of lake. Additionally, physical parameters of water such as temperature, dissolved oxygen, electrical conductivity (EC), pH, light permeability were measured in ...

  4. Nationwide trophic cascades: changes in avian community structure driven by ungulates

    Science.gov (United States)

    Palmer, Georgina; Stephens, Philip A.; Ward, Alastair I.; Willis, Stephen G.

    2015-10-01

    In recent decades, many ungulate populations have changed dramatically in abundance, resulting in cascading effects across ecosystems. However, studies of such effects are often limited in their spatial and temporal scope. Here, we contrast multi-species composite population trends of deer-sensitive and deer-tolerant woodland birds at a national scale, across Britain. We highlight the divergent fates of these two groups between 1994 and 2011, and show a striking association between the calculated divergence and a composite population trend of woodland deer. Our results demonstrate the link between changes in deer populations and changes in bird communities. In a period when composite population trends for deer increased by 46%, the community population trend across deer-sensitive birds (those dependent on understory vegetation) declined much more than the community trend for deer-tolerant birds. Our findings suggest that ongoing changes in the populations of herbivorous ungulates in many countries worldwide may help explain patterns of community restructuring at other trophic levels. Ungulate impacts on other taxa may require more consideration by conservation practitioners than they currently receive.

  5. 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

  6. 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).

  7. Determination of Trophic State Changes with Diel Dissolved Oxygen: A Case Study in a Shallow Lake.

    Science.gov (United States)

    Xu, Zhen; Xu, Y Jun

    2015-11-01

    Current trophic state indices (TSI) have been reported to have limitations in assessing changes in eutrophication status of shallow waters. This study aimed to use intensive measurements on dissolved oxygen (DO) to improve the determination of tropic state changes. The authors deployed an environment monitoring buoy in a eutrophic shallow lake and recorded water temperature, DO, and chlorophyll-a concentrations at 15-minute intervals for two 1-year periods: from August 2008 to July 2009 and from August 2013 to July 2014. In addition, they recorded water levels over the same periods and collected water samples for nutrient analysis. The authors analyzed the high-time resolution DO records, compared the diel DO trends between the two 1-year periods, and proposed a new TSI using DO. They found that analyzing the change in diel DO ranges can improve commonly used methods for classifying trophic states and assessing the change of eutrophication status of waterbodies.

  8. 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.

  9. The Effect of Teacher Candidates' Critical Literacy Levels on Their Media Literacy Levels

    Science.gov (United States)

    Semerci, Nuriye; Semerci, Çetin

    2017-01-01

    The purpose of this study is to determine the effect of teacher candidates' critical literacy levels on their media literacy levels. In the study, general survey model was used. The working group consists of 565 students studying at various departments of Bartin University, Faculty of Education. "Media Literacy Level Determination Scale"…

  10. Complex trophic interactions in kelp forest ecosystems

    Science.gov (United States)

    Estes, J.A.; Danner, E.M.; Doak, D.F.; Konar, B.; Springer, A.M.; Steinberg, P.D.; Tinker, M. Tim; Williams, T.M.

    2004-01-01

    The distributions and abundances of species and populations change almost continuously. Understanding the processes responsible is perhaps ecology’s most fundamental challenge. Kelp-forest ecosystems in southwest Alaska have undergone several phase shifts between alga- and herbivore-dominated states in recent decades. Overhunting and recovery of sea otters caused the earlier shifts. Studies focusing on these changes demonstrate the importance of top-down forcing processes, a variety of indirect food-web interactions associated with the otter-urchin-kelp trophic cascade, and the role of food-chain length in the coevolution of defense and resistance in plants and their herbivores. This system unexpectedly shifted back to an herbivore-dominated state during the 1990s, because of a sea-otter population collapse that apparently was driven by increased predation by killer whales. Reasons for this change remain uncertain but seem to be linked to the whole-sale collapse of marine mammals in the North Pacific Ocean and southern Bering Sea. We hypothesize that killer whales sequentially "fished down" pinniped and sea-otter populations after their earlier prey, the great whales, were decimated by commercial whaling. The dynamics of kelp forests in southwest Alaska thus appears to have been influenced by an ecological chain reaction that encompassed numerous species and large scales of space and time.

  11. 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.

  12. Roles of N:P Ratios on Trophic Structures and Ecological Stream Health in Lotic Ecosystems

    Directory of Open Access Journals (Sweden)

    Young-Jin Yun

    2016-01-01

    Full Text Available Little is known about the functions of N:P ratios in determining trophic structures and ecological health in lotic ecosystems, even though N:P ratios have been frequently used as a stoichiometric determinant in ambient water for trophic allocation of low-level organisms such as phytoplankton or zooplankton. In this study, nutrients (N, P and sestonic chlorophyll (CHL from 40 different streams in the Geum-River watershed were measured from 2008 to 2011. Fish compositions and stream health were also assessed, based on the multi-metric modeling of an index of biological integrity. Land use patterns in these watersheds were a key factor regulating nutrient contents and N:P ratios in ambient water, and also influenced empirical relationships between N:P ratios (or nutrients and sestonic CHL. Land use patterns in forested, urban and wastewater treatment plant regions were associated with significant differences in stream N:P ratios, and the ratios were mainly determined by phosphorus. Sestonic CHL was significantly correlated with nutrient level (N, P; the ratios had a positive linear relationship with the proportion of omnivores, and a negative relationship with the proportion of insectivores. A similar trend in the N:P ratios was observed in indicator fishes such as N. koreanus and Z. platypus. Overall, the N:P ratio may be a good surrogate variable of ambient concentrations of N or P in assessing trophic linkage and diagnosing the ecological stream health in aquatic ecosystems.

  13. 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...

  14. 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

  15. Feeding on copepod fecal pellets: a new trophic role of dinoflagellates as detritivores

    DEFF Research Database (Denmark)

    Poulsen, Louise K.; Moldrup, M.; Berge, T.

    2011-01-01

    in this study were: dinoflagellate concentration, the dinoflagellate-to-pellet size ratio, the feeding mechanism, pellet food source, and pellet age. This study reveals a new trophic role for dinoflagellates as detritivores, and shows that large (>20 µm) heterotrophic dinoflagellates alone can account...... for reported pellet degradation rates in field studies. Thus, dinoflagellates can function as an effective ‘protozoan filter’ for fecal pellets in the water column...

  16. Diversity of larvae of littoral Chironomidae (Diptera: Insecta and their role as bioindicators in urban reservoirs of different trophic levels Diversidade de larvas de Chironomidae (Diptera: Insecta e seu papel como bioindicadores na região litorânea de reservatórios urbanos em diferentes níveis tróficos

    Directory of Open Access Journals (Sweden)

    SS. Morais

    2010-11-01

    Full Text Available The Chironomidae (Diptera: Insecta have a high species richness, with species adapted to live under widely different environmental conditions. The study of the taxonomic composition of chironomid larvae and the percentage of occurrence of deformities in mouthparts, mainly in the mentum, are used in biomonitoring programmes in order to obtain information on the levels of organic and chemical pollution of aquatic ecosystems. The objective of this study was to evaluate the abundance of chironomid larvae and to quantify the occurrence of mentum deformities in the specimens collected in three urban reservoirs with different trophic levels. The reservoirs are located in the hydrographic basin of the Paraopeba River, an affluent of the São Francisco River basin (Minas Gerais State, southeastern Brazil. The Serra Azul Reservoir is oligotrophic, the Vargem das Flores Reservoir is mesotrophic, and the Ibirité Reservoir is eutrophic. Along the littoral zone of each reservoir, 30 samples were collected during each sampling campaign. Sampling was carried out every three months for one year, with two sampling campaigns during the wet season and two during the dry season in 2008. Physical and chemical parameters measured in the water column included the water depth, Secchi depth, air and water temperature, electrical conductivity, total dissolved solids, redox potential, dissolved oxygen, pH, turbidity, Total-N, Total-P, P-ortho, and chlorophyll-a. The chironomid larvae were identified to the genus level. The structure of the chironomid assemblages was evaluated based on taxonomic richness (24 genera, density, equitability, and diversity. The potential indicator taxa for each reservoir were established through an Indicator Species Analysis. The values for taxonomic richness (20 taxa, equitability (0.737, and Shannon-Wiener diversity (2.215 were highest in the Serra Azul Reservoir. Fissimentum was the indicator taxon in Serra Azul, the oligotrophic reservoir

  17. Feedback of threshold via estimating sources and composition of sedimentary organic matter across trophic gradients in freshwater lakes.

    Science.gov (United States)

    Xu, Xiaoguang; Li, Wei; Fujibayashi, Megumu; Nomura, Munehiro; Sakamaki, Takashi; Nishimura, Osamu; Li, Xianning

    2014-12-01

    The quantity and quality of sedimentary organic matter (SOM) in relation to material and energy flows are crucial for understanding the current state and future development of lake systems, yet, characterization of organic matter sources and assessment of their relative contributions in different trophic-state lakes caused by anthropogenic impacts are scarcely known. In this study, for obtaining information concerning the source of SOM and its compositional diversity along different trophic gradients, a total of thirty-one sampling sites from four freshwater lakes located in China and Japan were performed by the molecular level analysis using source-specific fatty acid biomarkers. Results indicated that SOM in these lakes was composed of microalgae-, aquatic plant-, terrestrial plant- and bacteria-derived organic matters based on their fatty acid profiles. The scatter plot matrix exhibited correlations between these sources, however, only terrestrial plant-derived organic carbon was a well predictor for sediment TOC with strong, spatiotemporal dynamics. The source and composition of SOM were evidently influenced by lake trophic state with redundancy analysis. Moreover, increase of lake trophic state led to the relatively higher contribution of aquatic organic matter sources to SOM pool compared with terrigenous sources, as evidenced by significant correlations between the trophic state index [TSI (TP)] and the ratio of terrigenous to aquatic fatty acids (TARFA ratio). Yet, this changing trend became more gradual with higher trophic state and prevented the occurrence of regime shift from allochthonous to autochthonous dominant state by a threshold (0.683) of TARFA ratio. Together, a conceptual diagram was proposed, which highlighted the prevailing state of allochthonous source and implicated sedimentary organics in biogeochemistry cycle within freshwater lakes. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. 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 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

  19. 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

  20. Fracked ecology: Response of aquatic trophic structure and mercury biomagnification dynamics in the Marcellus Shale Formation.

    Science.gov (United States)

    Grant, Christopher James; Lutz, Allison K; Kulig, Aaron D; Stanton, Mitchell R

    2016-12-01

    Unconventional natural gas development and hydraulic fracturing practices (fracking) are increasing worldwide due to global energy demands. Research has only recently begun to assess fracking impacts to surrounding environments, and very little research is aimed at determining effects on aquatic biodiversity and contaminant biomagnification. Twenty-seven remotely-located streams in Pennsylvania's Marcellus Shale basin were sampled during June and July of 2012 and 2013. At each stream, stream physiochemical properties, trophic biodiversity, and structure and mercury levels were assessed. We used δ15N, δ13C, and methyl mercury to determine whether changes in methyl mercury biomagnification were related to the fracking occurring within the streams' watersheds. While we observed no difference in rates of biomagnificaion related to within-watershed fracking activities, we did observe elevated methyl mercury concentrations that were influenced by decreased stream pH, elevated dissolved stream water Hg values, decreased macroinvertebrate Index for Biotic Integrity scores, and lower Ephemeroptera, Plecoptera, and Trichoptera macroinvertebrate richness at stream sites where fracking had occurred within their watershed. We documented the loss of scrapers from streams with the highest well densities, and no fish or no fish diversity at streams with documented frackwater fluid spills. Our results suggest fracking has the potential to alter aquatic biodiversity and methyl mercury concentrations at the base of food webs.

  1. 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.

  2. 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.

  3. Trophic matches in Northern Alaska: Existing synchrony among climate, vegetation, arthropods and migratory songbirds

    Science.gov (United States)

    Boelman, N.; Gough, L.; Wingfield, J. C.; Team Bird

    2011-12-01

    Climate change in the Arctic is altering patterns of seasonality while also altering the composition and structure of vegetation. In contrast to plants, energy balance, and carbon and nitrogen cycling, the responses of animal populations to these changes have been drastically understudied in the Alaskan interior and much of the Arctic. Investigations are therefore needed to better understand trophic dynamics involving vertebrates under current conditions, and to predict how this group may be impacted by both the direct and indirect effects of changing seasonality and vegetation cover. This is particularly important for migratory animals that breed annually on the arctic tundra because they provide a direct connection between the rapidly changing arctic environment and their more southern staging and over-wintering habitats. In a five year observational study, we are exploring how both shifts towards earlier spring snow melt and the ongoing increase in regional deciduous shrub dominance may affect migratory songbird communities that depend on the tundra for food and shelter during their breeding season. Here we present early results from sites in northern Alaska that differ in shrub height and abundance that reveal: (1) strong existing synchrony among the timing of spring snow melt, spring air temperatures, vegetation phenology, arthropod phenology and the timing of breeding stages of migratory songbirds, and; (2) significant differences in the types and abundance of vegetative and arthropod food sources, as well as environmental and biophysical micro-habitat conditions, between non-shrub dominated tundra plots and deciduous shrub dominated tundra. The arrival time of migratory songbirds on the tundra, and thus the onset of their breeding cycle, is cued by day length, while snow melt, plant growth and arthropod emergence are temperature sensitive. We therefore hypothesize that warmer spring time temperatures could cause a mismatch between the arrival time and onset

  4. Gut contents as direct indicators for trophic relationships in the Cambrian marine ecosystem.

    Directory of Open Access Journals (Sweden)

    Jean Vannier

    Full Text Available Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5 Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways.

  5. Determination of Trophic Structure in Selected Freshwater Ecosystems by using Stable Isotope Analysis.

    Science.gov (United States)

    Zainordin, 'Amila Faqhira; Ab Hamid, Suhaila

    2017-07-01

    Stable isotope analysis has been used extensively to establish trophic relationships in many ecosystems. Present study utilised stable isotope signatures of carbon and nitrogen to identify trophic structure of aquatic food web in river and rice field ecosystems in Perak, northern peninsular Malaysia. The mean δ 13 C values of all producers ranged from -35.29 ± 0.21 to -26.00 ± 0.050‰. The greatest δ 15 N values noted was in zenarchopterid fish with 9.68 ± 0.020‰. The δ 15 N values of aquatic insects ranged between 2.59 ± 0.107 in Elmidae (Coleoptera) and 8.11 ± 0.022‰ in Nepidae (Hemiptera). Correspondingly, with all the δ 13 C and δ 15 N values recorded, it can be deduced that there are four trophic levels existed in the freshwater ecosystems which started with the producer (plants), followed by primary consumer (aquatic insects and non-predatory fish), secondary consumer (invertebrate predators) and lastly tertiary consumer (vertebrate predators).

  6. 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.

  7. Community, trophic structure and functioning in two contrasting Laminaria hyperborea forests

    Science.gov (United States)

    Leclerc, Jean-Charles; Riera, Pascal; Laurans, Martial; Leroux, Cédric; Lévêque, Laurent; Davoult, Dominique

    2015-01-01

    Worldwide kelp forests have been the focus of several studies concerning ecosystem dysfunction in the past decades. Multifactorial kelp threats have been described and include deforestation due to human impact, cascading effects and climate change. Here, we compared community and trophic structure in two contrasting kelp forests off the coasts of Brittany. One has been harvested five years before sampling and shelters abundant omnivorous predators, almost absent from the other, which has been treated as preserved from kelp harvest. δ15N analyses conducted on the overall communities were linked to the tropho-functional structure of different strata featuring these forests (stipe and holdfast of canopy kelp and rock). Our results yielded site-to-site differences of community and tropho-functional structures across kelp strata, particularly contrasting in terms of biomass on the understorey. Similarly, isotope analyses inferred the top trophic position of Marthasterias glacialis and Echinus esculentus which may be considered as strong interactors in the sub-canopy. We interrogate these patterns and propose a series of probable and testable alternative hypotheses to explain them. For instance, we propose that differences of trophic structure and functioning result from confounded effects of contrasting wave dissipation depending on kelp size-density structure and community cascading involving these omnivorous predators. Given the species diversity and complexity of food web highlighted in these habitats, we call for further comprehensive research about the overall strata and tropho-functional groups for conservation management in kelp forests.

  8. Trophic State of a Shallow Lake with Reduced Inflow of Surface Water

    Directory of Open Access Journals (Sweden)

    Ejankowski Wojciech

    2014-12-01

    Full Text Available According to the general classification of shallow eutrophic lakes, two alternative types are distinguished: phytoplankton-dominated and macrophyte-dominated lakes. The latter type is rare and currently endangered by human activity. In order to determine the effect of reduced inflow of surface water by an earth dyke on the lake trophic state, certain biological and physico-chemical parameters were evaluated. This work focuses on two lakes of similar morphometric characteristics situated