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Sample records for trophic levels surrounding

  1. 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

  2. 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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2016-03-16

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

  6. Shift in trophic level of Mediterranean mariculture species.

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Valentina Lauria

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

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

    Science.gov (United States)

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

    2012-01-01

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

  9. 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...

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

    Science.gov (United States)

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

    2018-01-01

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

  11. 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...

  12. 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.

  13. 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.

  14. Biodiversity enhances ecosystem multifunctionality across trophic levels and habitats

    Science.gov (United States)

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

    2015-01-01

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

  15. 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.

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Directory of Open Access Journals (Sweden)

    German A Soler

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

  18. 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.

  19. 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

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

    Science.gov (United States)

    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.

  1. 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.

  2. 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)

  3. 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 ...

  4. 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.

  5. 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.

  6. 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.

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

    Science.gov (United States)

    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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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)

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    J. J. de LOPE ARIAS

    2016-04-01

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

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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

  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. 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.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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

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

    Directory of Open Access Journals (Sweden)

    Katrin Tirok

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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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)

  18. 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

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    OpenAIRE

    Maes, Hanna

    2011-01-01

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

  7. 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

  8. 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.

  9. 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.

  10. 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.

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

    Science.gov (United States)

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

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    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. 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.

  14. 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

  15. 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.

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

    Science.gov (United States)

    Scharler, U.M.; Ulanowicz, 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

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

    Science.gov (United States)

    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.

  2. 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...

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. Understanding the social and economic contexts surrounding women engaged in street-level prostitution.

    Science.gov (United States)

    Murphy, Lyn Stankiewicz

    2010-12-01

    Prostitution involves the exchange of sexual services for economic compensation. Due to the sexual promiscuity surrounding prostitution, women involved in prostitution constitute a high-risk group for contracting and transmitting STDs, including HIV. Prostitution is not only a public health concern, but also an economic one. Cities throughout the United States spent an average of $7.5 to $16 million per year enforcing prostitution laws and addressing negative outcomes associated with prostitution. Thus, women involved in prostitution are a cause for concern from both public health and economic perspectives. However, little is known about why women remain in this type of behavior given the risks prostitution presents, and even less is known about how to intervene and interrupt the complex cycle of prostitution. Thus, the purpose of this study was to understand what factors contribute to a woman's decision to remain in prostitution. A series of interviews were conducted with 12 women engaged in street-level prostitution. Results of the study revealed that drug use not only spurs entry into prostitution, but also contributes to the tenure of prostitution. Further, social support and economic stability are plausible reasons for women remaining in prostitution. These findings lead us to recommendations for policy and program development. Women involved in prostitution are a highly marginalized population, rarely recognized as individuals with life histories. Understanding why women remain in prostitution is important, because until these determinants are known, intervention programs designed to interrupt the cycle, and ultimately prevent prostitution, cannot be formulated.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-03-15

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

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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)

  8. 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.

  9. Soil mercury levels in the area surrounding the Cerro Prieto geothermal complex, MEXICO.

    Science.gov (United States)

    Pastrana-Corral, M A; Wakida, F T; García-Flores, E; Rodriguez-Mendivil, D D; Quiñonez-Plaza, A; Piñon-Colin, T D J

    2016-08-01

    Even though geothermal energy is a renewable energy source that is seen as cost-effective and environmentally friendly, emissions from geothermal plants can impact air, soil, and water in the vicinity of geothermal power plants. The Cerro Prieto geothermal complex is located 30 km southeast of the city of Mexicali in the Mexican state of Baja California. Its installed electricity generation capacity is 720 MW, being the largest geothermal complex in Mexico. The objective of this study was to evaluate whether the emissions generated by the geothermal complex have increased the soil mercury concentration in the surrounding areas. Fifty-four surface soil samples were collected from the perimeter up to an approximate distance of 7660 m from the complex. Additionally, four soil depth profiles were performed in the vicinity of the complex. Mercury concentration in 69 % of the samples was higher than the mercury concentration found at the baseline sites. The mercury concentration ranged from 0.01 to 0.26 mg/kg. Our results show that the activities of the geothermal complex have led to an accumulation of mercury in the soil of the surrounding area. More studies are needed to determine the risk to human health and the ecosystems in the study area.

  10. 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...

  11. 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.

  12. 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.

  13. 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.

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

    Science.gov (United States)

    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. 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.

  16. 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

  17. 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

  18. 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.

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

    Science.gov (United States)

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

    2014-12-01

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

  20. 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. 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.

  2. 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

  3. 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...

  4. 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).

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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).

  10. 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.

  11. Levels and distribution of polybrominated diphenyl ethers (PBDEs) in the freshwater environment surrounding a PBDE manufacturing plant in China

    International Nuclear Information System (INIS)

    Xu Jie; Gao Zishen; Xian Qiming; Yu Hongxia; Feng Jianfang

    2009-01-01

    Polybrominated diphenyl ethers (PBDEs) were determined in muscle, liver and eggs of freshwater fishes and surface sediments from the Nongkang River in Jinhu, Jiangsu Province, China. The present study is the first to report PBDE concentrations in the freshwater environment surrounding a PBDE manufacturing plant in China. The concentrations of 13 PBDE congeners in muscle, liver and eggs of freshwater fishes ranged from < LOD to 130, < LOD to 252 and < LOD to 33.3 ng/g lipid wt, respectively, while the concentrations of 13 PBDE congeners in surface sediments from sewage outfall, upstream and downstream of the river were 52, 9.2, 7.1 ng/g organic carbon wt, respectively. Contamination by PBDEs in this area was not serious when compared with other regions of the world. A relatively high proportion of BDE-183 was found, consistent with the octa-BDE technical mixtures from the manufacturing plant by the side of the river. - The first study to report concentrations of PBDEs in the freshwater environment surrounding a PBDE manufacturing plant in China.

  12. 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

  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. 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...

  15. 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...

  16. 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

  17. 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.

  18. 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...

  19. 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.

  20. 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

  1. 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...

  2. Iron, Copper, and Zinc Concentration in Aβ Plaques in the APP/PS1 Mouse Model of Alzheimer's Disease Correlates with Metal Levels in the Surrounding Neuropil.

    Science.gov (United States)

    James, Simon A; Churches, Quentin I; de Jonge, Martin D; Birchall, Ian E; Streltsov, Victor; McColl, Gawain; Adlard, Paul A; Hare, Dominic J

    2017-03-15

    The metal ions of iron, copper, and zinc have long been associated with the aggregation of β-amyloid (Aβ) plaques in Alzheimer's disease; an interaction that has been suggested to promote increased oxidative stress and neuronal dysfunction. We examined plaque metal load in the hippocampus of APP/PS1 mice using X-ray fluorescence microscopy to assess how the anatomical location of Aβ plaques was influenced by the metal content of surrounding tissue. Immunohistochemical staining of Aβ plaques colocalized with areas of increased X-ray scattering power in unstained tissue sections, allowing direct X-ray based-assessment of plaque metal levels in sections subjected to minimal chemical fixation. We identified and mapped 48 individual plaques in four subregions of the hippocampus from four biological replicates. Iron, Cu, and Zn areal concentrations (ng cm -2 ) were increased in plaques compared to the surrounding neuropil. However, this elevation in metal load reflected the local metal makeup of the surrounding neuropil, where different brain regions are enriched for different metal ions. After correcting for tissue density, only Zn levels remained elevated in plaques. This study suggests that the in vivo binding of Zn to plaques is not simply due to increased protein deposition.

  3. 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 ...

  4. Study of indoor radon, thoron and their progeny concentration levels in the surrounding areas of Mangaldoi, Assam

    International Nuclear Information System (INIS)

    Deka, P.C.; Sarkar, S.; Goswami, T.D.; Sarma, B.K.

    2006-01-01

    Natural sources contribute a significant percentage of radiation towards the total radiation exposure that humans receive. The majority of this natural radiation is harmless to humans in the ambient environment. However, radon, a major component of the natural radiation that humans are exposed to (greater than sixty percent), can pose a threat to the public health when radon gas accumulates in poorly ventilated residential and occupational settings. Measurements of concentration of radon, thoron and their decay products in various indoor environment covering four seasons of a year were carried out using the passive time-integrated method by employing LR-15 type II detectors in plastic twin-chamber dosimeter cups. The estimated indoor radon levels for well ventilated houses varied from a minimum value of 25.2 Bq.m -3 to a maximum of 80J Bq.m -3 with an annual geometric mean of 46.9 Bq.m -3 and that for poorly ventilated houses varied from a minimum value of 46.8 Bq.m -3 to a maximum of 146.8 Bq.m -3 with the annual geometric mean of 82 .2 Bq.m -3 . The thoron levels in well ventilated houses were also varied from a minimum value of 4.9 Bq.m -3 to a maximum of 21.5 Bq.m -3 with an annual geometric mean of 10.5 Bq.m -3 and that for poorly ventilated houses varied from a minimum of 6.3 Bq.m -3 to a maximum value of 29.2 Bq.m -3 with the annual geometric mean of 14.1 Bq.m -3 . Thus it is seen that both radon and thoron levels are higher in poorly ventilated houses than in well-ventilated houses. The ranges of radon and thoron progeny levels for well ventilated houses were 0.10 mWL to 0.58 mWL with an annual geometric mean of 0.21 mWL and 0.01 mWL to 0.06 mWL with an annual geometric mean of 0.03 mWL respectively. Similar variation was also observed in poorly ventilated houses. In poorly ventilated houses, the radon and thoron progeny levels varied between 0.16 mWL and 1.61 mWL with an annual geometric mean of 0.41 mWL and 0.02 to 029 mWL with the annual geometric mean

  5. 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

  6. '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.

  7. Water pollution and cyanobacteria's variation of rivers surrounding southern Taihu Lake, China.

    Science.gov (United States)

    Sun, Mingyang; Huang, Linglin; Tan, Lisha; Yang, Zhe; Baig, Shams Ali; Sheng, Tiantian; Zhu, Hong; Xu, Xinhua

    2013-05-01

    The water quality and cyanobacterial variation of rivers surrounding southern Taihu Lake, China were purposively monitored from 2008 to 2010. Trophic level index (TLI) was used to evaluate the trophic levels of southern Taihu Lake. Results showed a considerable decline in the monitored data compared with 2007, and the data showed downward trends year after year. The TLI decreased from 55.6 to 51.3, which implied that southern Taihu Lake was mildly eutrophic. The water quality and cyanobacterial variation indicated a positive response to the adopted control measures in the southern Taihu Lake basin, but the intra- and inter-annual variability was still quite varied. High concentrations of nitrogen and phosphorus typically lead to algae outbreaks, however, the cyanobacteria growth may result in a decline of the concentration of nitrogen and phosphorus. Temperature and other weather conditions are also important factors for algae outbreaks; the risk of blue-green algal blooms still persists.

  8. [Lead levels in high-risk populations and the surrounding environment in San Ignacio, Fresnillo, Zacatecas, México].

    Science.gov (United States)

    Manzanares-Acuña, Eduardo; Vega-Carrillo, Héctor René; Salas-Luévano, Miguel Angel; Hernández-Dávila, Victor Martin; Letechipía-de León, Consuelo; Bañuelos-Valenzuela, Rómulo

    2006-01-01

    To determine the lead concentration in the blood of children and nursing or pregnant women from San Ignacio, Fresnillo, in Zacatecas, Mexico as well as in soil, plants, ash and lead-glazed pottery, in order to determine exposure due to a metal-recycling facility. The study was carried out from December 2004 to April 2005. Lead in blood was measured with anodic stripping voltammetry, while dispersive energy X-ray fluorescence was used in the other matrices. Based upon the criteria outlined in the Official Mexican Standards, 90% of the children was identified as category 1, 5% as category II and another 5% as category III. The soil in the land near the facility contained from 73 to 84,238 microg/g, with an average of 4940 microg/g. Larger lead concentrations were found on sites located closer to the facility. San Ignacio's soil contained, on average, 109 microg/g. High lead levels were found in glazed pottery and the concentration in agricultural crops was greater than 300 microg/g. Although the majority of children in San Ignacio have blood lead concentrations considered to be acceptable according to the Official Mexican Standards, several studies indicate that deleterious effects on children's health exist even at low concentrations. The land around the metal recycling facility is contaminated with lead, and to that extent, the crops that are produced there, once ingested, are a source of contamination, which is compounded by the use of glazed pottery.

  9. 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.

  10. 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

  11. 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...

  12. The impact of mining activities in alteration of As levels in the surrounding ecosystems: an encompassing risk assessment and evaluation of remediation strategies.

    Science.gov (United States)

    Susaya, Janice; Kim, Ki-Hyun; Jung, Myung Chae

    2010-10-15

    A comprehensive field survey was conducted to explore the status of arsenic (As) contamination in soil and water systems surrounding numerous abandoned mine sites in Korea, which were previously applied with soil-topping (15 cm deep) and lime treatment for remediation purposes. This survey also aimed to assess the environmental stability of those reservoirs in relation to their established guidelines for As. To this end, a total of 5837 target soils (TS) were analyzed along with 305 control soils (CS) and 74 tailing (TA) samples. In addition, analyses were also extended to cover 1066 water and 329 sediment samples. Substantial evidence (e.g., differences in the mean As levels between TS (12.7 mg kg(-1)) and CS (0.69 mg kg(-1)) and the strong correlation between TS and TA) suggests a strong effect of previous mining activities. Soil-topping method was successful in confining As at the subsurface soil and restraining its dispersal. Although soil pH level also dropped with increasing As, it was restored to near neutrality by liming treatment. The mean values of As in water samples are comparable between dry (22.2) and wet seasons (21.2 mg L(-1)), while its values frequently exceeded various guideline limits. The pollution status of the current land and water systems needs to be assessed properly along with a removal plan for mine wastes/tailings to limit the dispersion of As in the study area. 2010 Elsevier B.V. All rights reserved.

  13. 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

  14. Emission of SO2 and SO42- from copper smelter and its influence on the level of total s in soil and moss in Bor and the surroundings

    Directory of Open Access Journals (Sweden)

    Šerbula Snežana M.

    2015-01-01

    Full Text Available Bor and the surroundings (Eastern Serbia have been known for exploitation and processing of sulphide copper ores for more than 100 years. Emissions of waste gases and particulate matter rich in heavy metals are characteristic for pyrometallurgical production of copper. Long-term measurement results (2005-2008 indicate an increased sulphur dioxide level in the urban-industrial zone of Bor since it is closest to the copper smelter which is a dominant source of air pollution in the studied area. Average annual sulphur dioxide concentrations at four measuring sites in the urban-industrial zone exceeded the maximum allowable value of 50 μg/m3. However the maximum allowable value of the total atmospheric depositions (200 mg/m2/day on an annual basis exceeded only at two of 15 measuring sites in the urban-industrial and rural zone. The highest annual deposition rate of sulphates from deposition was detected in the urban-industrial zone. Since the maximum permitted value for sulphates is not defined by the Serbian Regulations, the extent of the pollution cannot be discussed. Since the environment can continuously be polluted through the wet and dry deposition, biomonitoring by moss was conducted, which revealed significantly higher concentrations of total sulphur in moss in the urban-industrial zone, compared to the background zone. The obtained results confirm the reliability of moss as a bioindicator of ambient pollution. Higher total S concentration in soil samples was noted at the rural site (Ostrelj located in the close vicinity of two tailing ponds. [Projekat Ministarstva nauke Republike Srbije, br. 46010, br. 33038 i br. 172037

  15. 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.

  16. Potential effects of existing and proposed groundwater withdrawals on water levels and natural groundwater discharge in Snake Valley and surrounding areas, Utah and Nevada

    Science.gov (United States)

    Masbruch, Melissa D.; Brooks, Lynette E.

    2017-04-14

    Several U.S. Department of Interior (DOI) agencies are concerned about the cumulative effects of groundwater development on groundwater resources managed by, and other groundwater resources of interest to, these agencies in Snake Valley and surrounding areas. The new water uses that potentially concern the DOI agencies include 12 water-right applications filed in 2005, totaling approximately 8,864 acre-feet per year. To date, only one of these applications has been approved and partially developed. In addition, the DOI agencies are interested in the potential effects of three new water-right applications (UT 18-756, UT 18-758, and UT 18-759) and one water-right change application (UT a40687), which were the subject of a water-right hearing on April 19, 2016.This report presents a hydrogeologic analysis of areas in and around Snake Valley to assess potential effects of existing and future groundwater development on groundwater resources, specifically groundwater discharge sites, of interest to the DOI agencies. A previously developed steady-state numerical groundwater-flow model was modified to transient conditions with respect to well withdrawals and used to quantify drawdown and capture (withdrawals that result in depletion) of natural discharge from existing and proposed groundwater withdrawals. The original steady-state model simulates and was calibrated to 2009 conditions. To investigate the potential effects of existing and proposed groundwater withdrawals on the groundwater resources of interest to the DOI agencies, 10 withdrawal scenarios were simulated. All scenarios were simulated for periods of 5, 10, 15, 30, 55, and 105 years from the start of 2010; additionally, all scenarios were simulated to a new steady state to determine the ultimate long-term effects of the withdrawals. Capture maps were also constructed as part of this analysis. The simulations used to develop the capture maps test the response of the system, specifically the reduction of natural

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. The potential vulnerability of the Namib and Nama Aquifers due to low recharge levels in the area surrounding the Naukluft Mountains, SW Namibia

    Science.gov (United States)

    Kambinda, Winnie N.; Mapani, Benjamin

    2017-12-01

    The Naukluft Mountains in the Namib Desert are a high rainfall-high discharge area. It sees increased stream-, spring-flow as well as waterfalls during the rainy season. The mountains are a major resource for additional recharge to the Namib and Nama aquifers that are adjacent to the mountains. This paper aimed to highlight the potential vulnerability of the aquifers that surround the Naukluft Mountain area; if the strategic importance of the Naukluft Karst Aquifer (NKA) for bulk water supply becomes necessary. Chloride Mass Balance Method (CMBM) was applied to estimate rainfall available for recharge as well as actual recharge thereof. This was applied using chloride concentration in precipitation, borehole and spring samples collected from the study area. Groundwater flow patterns were mapped from hydraulic head values. A 2D digital elevation model was developed using Arc-GIS. Results highlighted the influence of the NKA on regional groundwater flow. This paper found that groundwater flow was controlled by structural dip and elevation. Groundwater was observed to flow predominantly from the NKA to the south west towards the Namib Aquifer in two distinct flow patterns that separate at the center of the NKA. A distinct groundwater divide was defined between the two flow patterns. A minor flow pattern from the northern parts of the NKA to the north east towards the Nama Aquifer was validated. Due to the substantial water losses, the NKA is not a typical karst aquifer. While the project area receives an average rainfall of 170.36 mm/a, it was estimated that 1-14.24% (maximum 24.43 mm/a) rainfall was available for recharge to the NKA. Actual recharge to the NKA was estimated to be less than 1-18.21% (maximum 4.45 mm/a) reflecting the vast losses incurred by the NKA via discharge. This paper concluded that groundwater resources of the NKA were potentially finite. The possibility of developing the aquifer for bulk water supply would therefore drastically lower recharge

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Depth to water in the eastern Snake River Plain and surrounding tributary valleys, southwestern Idaho and eastern Oregon, calculated using water levels from 1980 to 1988

    Science.gov (United States)

    Maupin, Molly A.

    1992-01-01

    The vulnerability of ground water to contamination in Idaho is being assessed by the IDHW/DEQ (Idaho Department of Health and Welfare, Division of Environmental Quality), using a modified version of the Environmental Orotection Agency DRASTIC methods (Allers and others, 1985). The project was designed as a technique to: (1) Assign priorities for development of ground-water management and monitoring programs; (2) build support for, and public awareness of, vulnerability or ground water to contamination; (3) assist in the development of regulatory programs; and (4) provide access to technical data through the use of a GIS (geographic information system) (C. Grantha,, Idaho Department of Health and Welfare, written commun., 1989). A digital representation of first-encountered water below land surface is an important element in evaluating vulnerability of ground water to contamination. Depth-to-water values were developed using existing data and computer software to construct a GIS data set to be combined with a sols data set developed by the SCS (Soil Conservation Service) and IDHW/WQB (Idaho Department of Health and Welfare/Water Quality Bureau), and a recharge data set developed by the IDWR/RSF (Idaho Department of Water Resources/Remote Sensing Facility). The USGS (U.S. Geological Survey) developed digital depth-to-water values for eleven 1:100,000-scale quadrangles on the eastern Snake River Plain and surrounding tributary valleys.

  8. Depth to water in the western Snake River Plain and surrounding tributary valleys, southwestern Idaho and eastern Oregon, calculated using water levels from 1980 to 1988

    Science.gov (United States)

    Maupin, Molly A.

    1991-01-01

    The vulnerability of ground water to contamination in Idaho is being assessed by the ISHW/DEQ (Idaho Department of Health and Welfare, Division of Environmental Quality), using a modified version of the Environmental Protection Agency DRASTIC methods (Allers and others, 1985). The project was designed as a technique to: (1) Assign priorities for development of ground-water management and monitoring programs; (2) build support for, and public awareness of, vulnerability of ground water to contamination; (3) assist in the development of regulatory programs; and (4) provide access to technical data through the use of a GIS (geographic information system) (C. Grantham, Idaho Department of Health and Welfare, written commun., 1989). Digital representation of first-encountered water below land surface is an important element in evaluating vulnerability of ground water to contamination. Depth-to-water values were developed using existing data and computer software to construct a GIS data set to be combined with a soils data set developed by the SCS (Soul Conservation Service) and the IDHW/WQB (Idaho Department of Health and Welfare/Water Quality Bureau), and a recharge data set developed by the IDWR/RSF (idaho Department of Water Resources/Remote Sensing Facility). The USGS (U.S. Geological Survey) has developed digital depth-to-water values for eleven 1:100,00-scale quadrangles on the eastern Snake River Plain and surrounding tributary valleys.

  9. 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.

  10. 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

  11. 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 ...

  12. 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.

  13. 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.

  14. A World without Surroundings

    Directory of Open Access Journals (Sweden)

    Daniel Innerarity

    2008-09-01

    Full Text Available This article is based on the metaphor of “a world without surroundings “which, on one hand, can help us to understand the nature of the world that is currently being configured with the processes of globalisation, and on the other, to assess the most intelligent strategies for shaping it, in accord with the criteria of balance and justice. Our task should be, therefore, to cosmopolitise globalisation; that is, to politicise the processes with new political concepts that no longer allow the use of the old strategies of delimitation or differentiation between “Us” and “Them”, and which are demanding integrative actions.

  15. The rise of the mine water level in the area of the former Kohinoor II mine and the influence on the surrounding aquifer systems of abandoned mines in the central part of the North Bohemian Brown Coal Basin

    Directory of Open Access Journals (Sweden)

    Milan Mikoláš

    2011-01-01

    Full Text Available The aim of this article is to evaluate the process of terminating the mine water pumping after the liquidation of the Kohinoor II coal mine, situated in the central part of the North Bohemian Brown Coal Basin (NBB and the subsequent resumption of pumping from the surface after the mine water rise in the area of the former mine to the desired level. We analyzed previously known data, particularly the amount of mine water pumped from the mine area and the surrounding abandoned mines in the past. Further the evaluation of known surrounding abandoned mines aquifer systems, accumulated in the coal seam (underground accumulation of water and the evaluation of the effect of increasing the water level in the Kohinoor II mine, focusing on the enlargement of the central mine aquifers and the evaluation of the effects of changes in the way of pumping on the surrounding coal seam and its mining with continued safe brown coal mining at the nearby Bílina mine, that can be ensured for at least another 25 years.

  16. Impact of human activities on nutrient and trophic status of some ...

    African Journals Online (AJOL)

    Impact of human activities on nutrient and trophic status of some selected Lagoons in Ghana. ... The high phosphorus (231.9 kg/day) and nitrogen (927.9 kg/day) recorded at Nyanya lagoon are as a result of domestic activities mainly from the wastes generated from humans at the lagoon and its surroundings. The use of ...

  17. Transparency, consultation and conflict: Assessing the micro-level risks surrounding the drive to develop Peru's Amazonian oil and gas resources

    DEFF Research Database (Denmark)

    Haselip, James Arthur

    2011-01-01

    Since the 1990s, successive Governments in Peru have sought to expand the exploration and production of the country's oil and gas resources. This economic agenda poses significant opportunities and risks which are usually considered at the macro-level and framed by debates regarding the so....... In the case of Peru, this is especially relevant to the vast areas of ecologically sensitive and previously under-developed Amazonia that are now under concession to oil and gas companies. Low levels of industry transparency combined with a lack of uniform free, prior and informed consent are exacerbating...

  18. 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

  19. A follow up of the decrease of non exchangeable organically bound tritium levels in the surroundings of a nuclear research center.

    Science.gov (United States)

    Baglan, N; Alanic, G; Le Meignen, R; Pointurier, F

    2011-07-01

    In the past decades limited amounts of tritium were handled on the CEA site of Bruyères le Châtel with authorised atmospheric releases. A small fraction of the tritium released entered into environmental samples under three forms: (i) as part of free water (TFWT - Tissue Free Water Tritium), or associated with organic matter in two ways; either (ii) bound to the oxygen and nitrogen atoms of the material as exchangeable organically bound tritium (E-OBT), or (iii) bound to carbon atoms as non exchangeable organically bound tritium (NE-OBT). The first two components provide only a picture of atmospheric tritium concentrations at the sampling time as they are in equilibrium with atmospheric moisture and soil humidity. Unlike these exchangeable forms, however, NE-OBT is tightly bound to the organic matter and provides an integrated record of atmospheric tritium during the growing phase of the vegetation. We mapped NE-OBT in tree leaf samples in an area of about 25×30km(2) around the centre of the CEA site and compared the results with those obtained during a previous sampling exercise in 1989. At this time, the activity levels were almost ten times higher than those observed presently in a similar area almost 20 years later which is consistent with the decrease of atmospheric releases issued from the centre. As the activity levels are now close to environmental background specific attention was also paid to the analytical procedure to ensure reliable low level NE-OBT detection. 2011 Elsevier Ltd. All rights reserved.

  20. 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.

  1. 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.

  2. 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

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Blood lead levels, δ-ALAD inhibition, and hemoglobin content in blood of giant toad (Rhinella marina) to assess lead exposure in three areas surrounding an industrial complex in Coatzacoalcos, Veracruz, Mexico.

    Science.gov (United States)

    Ilizaliturri-Hernández, César Arturo; González-Mille, Donaji Josefina; Mejía-Saavedra, Jesús; Espinosa-Reyes, Guillermo; Torres-Dosal, Arturo; Pérez-Maldonado, Iván

    2013-02-01

    The Coatzacoalcos Region in Veracruz, Mexico houses one of the most important industrial complexes in Mexico and Latin America. Lead is an ubiquitous environmental pollutant which represents a great risk to human health and ecosystems. Amphibian populations have been recognized as biomonitors of changes in environmental conditions. The purpose of this research is to measure exposure to lead and evaluate hematological and biochemical effects in specimens of giant toads (Rhinella marina) taken from three areas surrounding an industrial complex in the Coatzacoalcos River downstream. Lead levels in toads' blood are between 10.8 and 70.6 μg/dL and are significantly higher in industrial sites. We have found a significant decrease in the delta-aminolevulinic acid dehydratase (δ-ALAD) activity in blood from 35.3 to 78 % for the urban-industrial and industrial sites, respectively. In addition, we have identified a strong inverse relationship between the δ-ALAD activity and the blood lead levels (r = -0.84, p < 0.001). Hemoglobin and mean corpuscular hemoglobin levels, as well as the condition factor, are found to be lower at industrial sites compared with the reference sites. Our results suggest that the R. marina can be considered a good biomonitor of the δ-ALAD activity inhibition and hematological alterations at low lead concentrations.

  10. 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.

  11. 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.

  12. 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, ...

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Circumstances surrounding aneurysmal subarachnoid hemorrhage

    NARCIS (Netherlands)

    Schievink, W. I.; Karemaker, J. M.; Hageman, L. M.; van der Werf, D. J.

    1989-01-01

    The circumstances surrounding aneurysmal subarachnoid hemorrhage were investigated in a group of 500 consecutive patients admitted to a neurosurgical center. Subarachnoid hemorrhage occurred during stressful events in 42.8% of the patients, during nonstrenuous activities in 34.4%, and during rest or

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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 ...

  12. 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...

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Limited trophic partitioning among sympatric delphinids off a tropical oceanic atoll.

    Directory of Open Access Journals (Sweden)

    Hillary Young

    Full Text Available Understanding trophic relationships among marine predators in remote environments is challenging, but it is critical to understand community structure and dynamics. In this study, we used stable isotope analysis of skin biopsies to compare the isotopic, and thus, trophic niches of three sympatric delphinids in the waters surrounding Palmyra Atoll, in the Central Tropical Pacific: the melon-headed whale (Peponocephala electra, Gray's spinner dolphin (Stenella longirostris longirostris, and the common bottlenose dolphin (Tursiops truncatus. δ15N values suggested that T. truncatus occupied a significantly higher trophic position than the other two species. δ13C values did not significantly differ between the three delphinds, potentially indicating no spatial partitioning in depth or distance from shore in foraging among species. The dietary niche area-determined by isotopic variance among individuals-of T. truncatus was also over 30% smaller than those of the other species taken at the same place, indicating higher population specialization or lower interindividual variation. For P. electra only, there was some support for intraspecific variation in foraging ecology across years, highlighting the need for temporal information in studying dietary niche. Cumulatively, isotopic evidence revealed surprisingly little evidence for trophic niche partitioning in the delphinid community of Palmyra Atoll compared to other studies. However, resource partitioning may happen via other behavioral mechanisms, or prey abundance or availability may be adequate to allow these three species to coexist without any such partitioning. It is also possible that isotopic signatures are inadequate to detect trophic partitioning in this environment, possibly because isotopes of prey are highly variable or insufficiently resolved to allow for differentiation.

  1. 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.

  2. 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.

  3. Fluoroquinolones and Tetracycline Antibiotics in a Portuguese Aquaculture System and Aquatic Surroundings: Occurrence and Environmental Impact.

    Science.gov (United States)

    Pereira, André M P T; Silva, Liliana J G; Meisel, Leonor M; Pena, Angelina

    2015-01-01

    The growth of aquaculture over the past few years is widely recognized as one of the main sources of antibiotics, mainly fluoroquinolones (FQ) and tetracyclines (TC), in the aquatic environment, consequently, increasing the risk of the emergence of antibiotic bacterial resistance and promoting the spread of resistant genes. This study aimed to (1) develop and validate a multiresidue method for determination and quantification of ciprofloxacin (CIP), difloxacin (DIFL), enrofloxacin (ENR), norfloxacin (NOR), sarafloxacin (SARA), and oxytetracycline (OXY) in aquaculture waters and surrounding water bodies and (2) provide the first Portuguese data to utilize in assessment of risk of adverse effects. In addition, the potential environmental impact posed by these antibiotics to aquatic organisms, belonging to different trophic levels, when exposed to the studied aquaculture waters was also assessed. The analytical strategy comprised of solid-phase extraction (SPE) through Oasis HLB cartridges, and detection and quantification by liquid chromatography with tandem mass spectrometry (LC/MS(n)). Method detection limits (MDL) and method quantification limits (MQL) were in the range of 0.7-3 ng/L and 2.4-10 ng/L, respectively. Recoveries varied between 57.4 and 122.8%. The method was applied to 31 water samples collected from an aquaculture and surrounding water bodies located in north of Portugal. Residues of all antibiotics, except SARA and DIFL, were detected at concentrations ranging from 3 to 75.1 ng/L. Norfloxacin was the antibiotic present at highest frequency and concentration. Regarding the environmental impact assessment (EIA), a risk quotient higher than 1 was observed for NOR.

  4. 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.

  5. 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

  6. Opportunity's Surroundings on Sol 1818

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical projection with geometric seam correction.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. [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.

  18. Opportunity's Surroundings on Sol 1798

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical projection with geometric seam correction.

  19. 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

  20. 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).

  1. 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

  2. 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,.

  3. 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...

  4. 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...

  5. 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.

  6. Bioaccumulation and biomagnification of emerging and classical flame retardants in bird eggs of 14 species from Doñana Natural Space and surrounding areas (South-western Spain).

    Science.gov (United States)

    Barón, E; Máñez, M; Andreu, A C; Sergio, F; Hiraldo, F; Eljarrat, E; Barceló, D

    2014-07-01

    The occurrence of classical (polybrominated diphenyl ethers, PBDEs) and emerging FRs (dechloranes, hexabromobenzene (HBB), pentabromoethyl benzene (PBEB) and decabromodiphenyl ethane (DBDPE)) in unborn eggs of 14 different species from Doñana Natural Space and surrounding areas was studied. PBDEs, Dec-602, Dec-603 and DP were detected in all the species, whereas HBB, PBEB, DBDPE and Dec-604 were not detected in any sample. ΣPBDE and ΣDechlorane levels ranged from 1.40 to 90.7, and from 0.77 to 260 ng/g lw, respectively. BDE-209 was the most abundant BDE congener in almost all the species, whereas Dec-602 was the predominant among dechloranes. In general, levels of PBDEs and dechloranes were similar and even higher for dechloranes, probably indicating the increasing use of dechloranes as a result of legal restrictions on PBDEs. In both cases, the most contaminated specie was the white stork. Using stable isotope characterization, differences among species and possible biomagnification processes were also evaluated. PBDE levels increased as the trophic position increased, showing biomagnification capacity. The same behavior was observed for Dec-602 and Dec-603; however, DP levels were not linearly correlated with trophic level. These results show that more attention should be given to emerging FRs such as dechloranes since they show similar environmental behavior as PBDEs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. 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.

  8. Heavy metal transfers between trophic compartments in different ecosystems in Galicia (Northwest Spain): Essential elements

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, X.I.; Aboal, J.R.; Fernandez, J.A.; Carballeira, A. [University of Santiago Compostela, Santiago De Compostela (Spain). Faculty of Biology

    2008-11-15

    In the present study, we determined the concentrations of Cu, Fe, Mn, and Zn in soil and several trophic compartments at a total of 16 sampling stations. The trophic compartments studied were primary producers, represented by two species of terrestrial mosses (Pseudoescleropodium purum and Hypnum cupressiforme) and oak trees (Quercus robur or Q. pyrenaica); primary consumers, represented by the wood mouse (Apodemus sylvaticus) and the yellow necked mouse (A. flavicollis); secondary consumers, represented by the shrew (Sorex granarius); and finally, detritivores, represented by slugs (Arion ater). Thirteen of the sampling stations were located in mature oak woodlands (Quercus sp.); two of the sampling stations were located in the area surrounding a restored lignite mine dump, and the other in an ultrabasic area. The analytical determinations revealed a lack of significant correlations among trophic compartments, possibly caused by effective regulation of metals by organisms and/or spatial variation in availability of metals from soil or food. Furthermore, the only element that showed a clear pattern of biomagnification was Cu; as for the other elements, there was always some divergence from such a pattern. Finally, the patterns of bioaccumulation in contaminated and woodland sampling stations were very similar, although there was enrichment of the concentrations of Cu, Mn, and Zn in the mice viscera, which, except for Mn, were related to higher edaphic concentrations.

  9. 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 in the agricultural landscape. The effect of the earth dyke on the trophic state was positively verified. The lake situated in the catchment basin, in which the inflow of surface water was reduced, was defined as meso-eutrophic, with a small amount of phytoplankton and high water transparency. The reference lake was highly eutrophic, with low water transparency and a large amount of phytoplankton. The water body surrounded by the earth dyke was macrophytes dominated (65% of the lake area, whereas the reference lake was a phytoplankton-macrophyte type (42% of the lake area. The trophic evaluation of a lake can be underestimated because of a significant amount of biogenic compounds accumulated in plant tissues. Thus, the values of Carlson’s indices in macrophyte-dominated lakes may not account for the total amount of nutrients in the water body.

  10. Reduced surround inhibition in musicians.

    Science.gov (United States)

    Shin, Hae-Won; Kang, Suk Y; Hallett, Mark; Sohn, Young H

    2012-06-01

    To investigate whether surround inhibition (SI) in the motor system is altered in professional musicians, we performed a transcranial magnetic stimulation (TMS) study in 10 professional musicians and 15 age-matched healthy non-musicians. TMS was set to be triggered by self-initiated flexion of the index finger at different intervals ranging from 3 to 1,000 ms. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of the control TMS at rest and expressed as a percentage. Normalized MEP amplitudes of the abductor digiti minimi (ADM) muscles were compared between the musicians and non-musicians with the primary analysis being the intervals between 3 and 80 ms (during the movement). A mixed-design ANOVA revealed a significant difference in normalized ADM MEPs during the index finger flexion between groups, with less SI in the musicians. This study demonstrated that the functional operation of SI is less strong in musicians than non-musicians, perhaps due to practice of movement synergies involving both muscles. Reduced SI, however, could lead susceptible musicians to be prone to develop task-specific dystonia.

  11. [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

  12. 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.

  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. 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.

  15. Eutrophication potential of lakes: an integrated analysis of trophic state, morphometry, land occupation, and land use.

    Science.gov (United States)

    Silvino, R F; Barbosa, F A R

    2015-08-01

    Despite being inside a protected area, Lake Sumidouro has been impacted by the anthropogenic occupation of the surrounding area since the 1970's, compromising the ecological integrity of the lake and the sustainable use of natural resources. This study examined the current trophic classification of the lake and developed methods for improving it through an integrated analysis of morphometric and limnological parameters, land use and land occupation in the watershed, and eutrophication potential. Data for the limnological parameters, land use and land occupation, and morphometric characteristics of Lake Sumidouro were collected in the rainy and dry seasons of 2009 and 2010. Depending on the trophic classification system used, Lake Sumidouro is classified as oligotrophic to hypereutrophic. In our study, the highest concentration of nutrients occurred in the rainy season, indicating that high nutrient inputs played an important role during this period. Areas of anthropogenic occupation comprised approximately 62.9% of the total area of the watershed, with pasture and urban settlement as the main types of land use. The influent total phosphorus load was estimated to be 15,824.3 kg/year. To maintain mesotrophic conditions, this load must be reduced by 29.4%. By comparing the isolated use of trophic state indices, this study demonstrated that comparing the trophic state classification with morphometric analyses, land use and land occupation types in the watershed, and potential phosphorus load provided better information to guide management actions for restoration and conservation. Furthermore, this approach also allowed for evaluating the vulnerability of the environment to the eutrophication process.

  16. Eutrophication potential of lakes: an integrated analysis of trophic state, morphometry, land occupation, and land use

    Directory of Open Access Journals (Sweden)

    RF Silvino

    Full Text Available AbstractDespite being inside a protected area, Lake Sumidouro has been impacted by the anthropogenic occupation of the surrounding area since the 1970’s, compromising the ecological integrity of the lake and the sustainable use of natural resources. This study examined the current trophic classification of the lake and developed methods for improving it through an integrated analysis of morphometric and limnological parameters, land use and land occupation in the watershed, and eutrophication potential. Data for the limnological parameters, land use and land occupation, and morphometric characteristics of Lake Sumidouro were collected in the rainy and dry seasons of 2009 and 2010. Depending on the trophic classification system used, Lake Sumidouro is classified as oligotrophic to hypereutrophic. In our study, the highest concentration of nutrients occurred in the rainy season, indicating that high nutrient inputs played an important role during this period. Areas of anthropogenic occupation comprised approximately 62.9% of the total area of the watershed, with pasture and urban settlement as the main types of land use. The influent total phosphorus load was estimated to be 15,824.3 kg/year. To maintain mesotrophic conditions, this load must be reduced by 29.4%. By comparing the isolated use of trophic state indices, this study demonstrated that comparing the trophic state classification with morphometric analyses, land use and land occupation types in the watershed, and potential phosphorus load provided better information to guide management actions for restoration and conservation. Furthermore, this approach also allowed for evaluating the vulnerability of the environment to the eutrophication process.

  17. 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.

  18. 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.

  19. 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...

  20. Linking environmental forcing and trophic supply to benthic communities in the Vercelli Seamount area (Tyrrhenian Sea.

    Directory of Open Access Journals (Sweden)

    Anabella Covazzi Harriague

    Full Text Available Seamounts and their influence on the surrounding environment are currently being extensively debated but, surprisingly, scant information is available for the Mediterranean area. Furthermore, although the deep Tyrrhenian Sea is characterised by a complex bottom morphology and peculiar hydrodynamic features, which would suggest a variable influence on the benthic domain, few studies have been carried out there, especially for soft-bottom macrofaunal assemblages. In order to fill this gap, the structure of the meio-and macrofaunal assemblages of the Vercelli Seamount and the surrounding deep area (northern Tyrrhenian Sea - western Mediterranean were studied in relation to environmental features. Sediment was collected with a box-corer from the seamount summit and flanks and at two far-field sites in spring 2009, in order to analyse the metazoan communities, the sediment texture and the sedimentary organic matter. At the summit station, the heterogeneity of the habitat, the shallowness of the site and the higher trophic supply (water column phytopigments and macroalgal detritus, for instance supported a very rich macrofaunal community, with high abundance, biomass and diversity. In fact, its trophic features resembled those observed in coastal environments next to seagrass meadows. At the flank and far-field stations, sediment heterogeneity and depth especially influenced the meiofaunal distribution. From a trophic point of view, the low content of the valuable sedimentary proteins that was found confirmed the general oligotrophy of the Tyrrhenian Sea, and exerted a limiting influence on the abundance and biomass of the assemblages. In this scenario, the rather refractory sedimentary carbohydrates became a food source for metazoans, which increased their abundance and biomass at the stations where the hydrolytic-enzyme-mediated turnover of carbohydrates was faster, highlighting high lability.

  1. Study of silver-110M transfer mechanisms in freshwater. Conceiving and utilization of an experimental model of ecosystem and of a mathematical model to simulate the radionuclide through a trophic chain

    International Nuclear Information System (INIS)

    Garnier-Laplace, J.

    1990-10-01

    Uptake and retention of 110m Ag are quantified from laboratory studies carried out on an experimental freshwater ecosystem composed by two abiotic units, water and sediment, and by four trophic levels: primary producer (Scenedesmus obliquus), first order consumers (Daphnia magna, Gammarus pulex, Chrionomus sp.), second order consumer (Cyprinus carpio) and third order one (Salmo trutta). The chosen analytical process consists in expressing each transfer by a mathematical equation which formulation is based on a theoric analysis. Experiments allow to calibrate parameters of these equations for each unit of the food chain. All experimental data concerning 110m Ag uptake emphasize the radioprotection implications of this radioelement, because of the high values of the estimated radioecological parameters. On the basis of the results obtained, a determinist mathematical model has been conceived to simulate the radionuclide distribution in the food chain as a function of a chronic or acute contamination mode. Its application gives the development with time of the mean 110m Ag concentration values for each trophic level. The first approaches based on the analysis of the results of field studies, carried out on ecosystems affected by chronic pollution (Rhone river) or acute one (as a consequence of the Chernobyl accident), give to the model an important explicative and global predictive quality. The age of the fish, their dietary habits which vary according to the annual cycle of the prey species and with theirposition in the food chain, appear such as essential parameters. The trophic pathway is clearly predominant whatever the contamination mode and, explains, for acute exposure, why accumulation of 110m Ag can be prolonged for a long time after the surrounding environment contamination [fr

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  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. 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...

  18. 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

  19. 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.

  20. 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...

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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;}

  7. 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).

  8. Species-area relationships are modulated by trophic rank, habitat affinity, and dispersal ability.

    Science.gov (United States)

    van Noordwijk, C G E; Verberk, Wilco C E P; Turin, Hans; Heijerman, Theodoor; Alders, Kees; Dekoninck, Wouter; Hannig, Karsten; Regan, Eugenie; McCormack, Stephen; Brown, Mark J F; Remke, Eva; Siepel, Henk; Berg, Matty P; Bonte, Dries

    2015-02-01

    In the face of ongoing habitat fragmentation, species-area relationships (SARs) have gained renewed interest and are increasingly used to set conservation priorities. An important question is how large habitat areas need to be to optimize biodiversity conservation. The relationship between area and species richness is explained by colonization-extinction dynamics, whereby smaller sites harbor smaller populations, which are more prone to extinction than the larger populations sustained by larger sites. These colonization-extinction dynamics are predicted to vary with trophic rank, habitat affinity, and dispersal ability of the species. However, empirical evidence for the effect of these species characteristics on SARs remains inconclusive. In this study we used carabid beetle data from 58 calcareous grassland sites to investigate how calcareous grassland area affects species richness and activity density for species differing in trophic rank, habitat affinity, and dispersal ability. In addition, we investigated how SARs are affected by the availability of additional calcareous grassland in the surrounding landscape. Beetle species richness and activity density increased with calcareous grassland area for zoophagous species that are specialists for dry grasslands and, to a lesser extent, for zoophagous habitat generalists. Phytophagous species and zoophagous forest and wet-grassland specialists were not affected by calcareous grassland area. The dependence of species on large single sites increased with decreasing dispersal ability for species already vulnerable to calcareous grassland area. Additional calcareous grassland in the landscape had a positive effect on local species richness of both dry-grassland specialists and generalists, but this effect was restricted to a few hundred meters. Our results demonstrate that SARs are affected by trophic rank, habitat affinity, and dispersal ability. These species characteristics do not operate independently, but should be

  9. 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.

  10. Contour detection by surround suppression of texture

    NARCIS (Netherlands)

    Petkov, Nicolai; Tavares, JMRS; Jorge, RMN

    2007-01-01

    Based on a keynote lecture at Complmage 2006, Coimbra, Oct. 20-21, 2006, an overview is given of our activities in modelling and using surround inhibition for contour detection. The effect of suppression of a line or edge stimulus by similar surrounding stimuli is known from visual perception

  11. 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.

  12. 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

  13. 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...

  14. Effects of sediment organic matter quality on bioaccumulation, degradation, and distribution of pyrene in two macrofaunal species and their surrounding sediment

    DEFF Research Database (Denmark)

    Granberg, Maria E.; Selck, Henriette

    2007-01-01

    Sediment dwelling macrofauna (infauna) are important vectors for the transfer of sediment-associated contaminants to higher trophic levels. Sedimenting organic matter constitutes an important food source for all benthic organisms and changes seasonally in terms of quantity and quality. Sediment...... imply that bioaccumulation and trophic transfer of sediment-associated PAH should increase following fresh organic matter input, e.g. after sedimentation of phytoplankton blooms. We stress the importance of considering behavioural characteristics of infauna and the trophic situation of the system when...

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. Trophic relationships on a fucoid shore in south-western Iceland as revealed by stable isotope analyses, laboratory experiments, field observations and gut analyses

    Science.gov (United States)

    Steinarsdóttir, M. B.; Ingólfsson, A.; Ólafsson, E.

    2009-04-01

    Rocky shores in the North Atlantic are known for their zonation patterns of both algae and animals, which can be expected to greatly affect food availability to consumers at different height levels on the shore. We tested the hypothesis that consumers would feed on the most abundant suitable food source in their surroundings. In total 36 species/taxa of common primary producers and consumers were sampled for stable isotope analyses from a sheltered fucoid shore at Hvassahraun in south-western Iceland. A selection of these species was also collected seasonally and from different height levels. Feeding experiments, field observations and gut analyses were also conducted. Our results were in good overall agreement with pre-existing knowledge of trophic relationships in the rocky intertidal. Consumers often appeared to be assimilating carbon and nitrogen from the most common diet in their immediate surroundings. The predator Nucella lapillus was thus feeding on different prey at different height levels in accordance with different densities of prey species. When tested in the laboratory, individuals taken from low on the shore would ignore the gastropod Littorina obtusata, uncommon at that height level, even when starved, while individuals from mid-shore readily ate the gastropod. This indicated that some kind of learned behaviour was involved. There were, however, important exceptions, most noteworthy the relatively small contribution to herbivores, both slow moving (the gastropod L. obtusata) and fast moving (the isopod Idotea granulosa and the amphipod Gammarus obtusatus) of the dominant alga at this site, Ascophyllum nodosum. The recent colonizer Fucus serratus seemed to be favoured. Selective feeding was indicated both by isotope signatures as well as by results of feeding experiments. Seasonal migrations of both slow and fast moving species could partly explain patterns observed.

  2. 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.

  3. Explaining preferences for home surroundings and locations

    DEFF Research Database (Denmark)

    Andersen, Hans Skifter

    2011-01-01

    This article is based on a survey carried out in Denmark that asked a random sample of the population about their preferences for home surroundings and locations. It shows that the characteristics of social surroundings are very important and can be divided into three independent dimensions...... with given characteristics and thus do not have priorities regarding home surroundings and locations. For others, mostly young people and singles, home is just a place to sleep and relax, whereas life is lived elsewhere. For this group, there are only preferences for location and there are few specific...

  4. Adhesion rings surround invadopodia and promote maturation

    Directory of Open Access Journals (Sweden)

    Kevin M. Branch

    2012-06-01

    Invasion and metastasis are aggressive cancer phenotypes that are highly related to the ability of cancer cells to degrade extracellular matrix (ECM. At the cellular level, specialized actin-rich structures called invadopodia mediate focal matrix degradation by serving as exocytic sites for ECM-degrading proteinases. Adhesion signaling is likely to be a critical regulatory input to invadopodia, but the mechanism and location of such adhesion signaling events are poorly understood. Here, we report that adhesion rings surround invadopodia shortly after formation and correlate strongly with invadopodium activity on a cell-by-cell basis. By contrast, there was little correlation of focal adhesion number or size with cellular invadopodium activity. Prevention of adhesion ring formation by inhibition of RGD-binding integrins or knockdown (KD of integrin-linked kinase (ILK reduced the number of ECM-degrading invadopodia and reduced recruitment of IQGAP to invadopodium actin puncta. Furthermore, live cell imaging revealed that the rate of extracellular MT1-MMP accumulation at invadopodia was greatly reduced in both integrin-inhibited and ILK-KD cells. Conversely, KD of MT1-MMP reduced invadopodium activity and dynamics but not the number of adhesion-ringed invadopodia. These results suggest a model in which adhesion rings are recruited to invadopodia shortly after formation and promote invadopodium maturation by enhancing proteinase secretion. Since adhesion rings are a defining characteristic of podosomes, similar structures formed by normal cells, our data also suggest further similarities between invadopodia and podosomes.

  5. Experiences during the decontamination process of areas surrounding to Fukushima

    International Nuclear Information System (INIS)

    Molina, G.

    2014-10-01

    In this work the experience gained during the decontamination of areas surrounding to Fukushima NPP, rugged during the earthquake and tsunami in 2011 and caused the contamination with fission products in these areas is described. Actions taken by the Japanese government are reported and some of the techniques used, the intervention levels and the progress made and disposal techniques considered are presented. (Author)

  6. 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 ...

  7. 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

  8. 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).

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  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. 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.

  19. 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...

  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

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    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. Surround Suppression Maps in the Cat Primary Visual Cortex

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    Matthieu P Vanni

    2013-04-01

    Full Text Available In the primary visual cortex and higher-order areas, it is well known that the stimulation of areas surrounding the classical receptive field of a neuron can inhibit its responses. In the primate area MT, this surround suppression was shown to be spatially organized into high and low suppression modules. However, such an organization hasn’t been demonstrated yet in the primary visual cortex. Here, we used optical imaging of intrinsic signals to spatially evaluate surround suppression in the cat visual cortex. The magnitude of the response was measured in areas 17 and 18 for stimuli with different diameters, presented at different eccentricities. Delimited regions of the cortex were revealed by circumscribed stimulations of the visual field (cortical response field. Increasing the stimulus diameter increased the spread of cortical activation. In the cortical response field, the optimal stimulation diameter and the level of suppression were evaluated. Most pixels (3/4 exhibited surround suppression profiles. The optimal diameter, corresponding to a population of receptive fields, was smaller in area 17 (22 deg. than in area 18 (36 deg. in accordance with electrophysiological data. No difference in the suppression strength was observed between both areas (A17: 25%, A18: 21%. Further analysis of our data revealed the presence of surround modulation maps, organized in low and high suppression domains. We also developed a statistical method to confirm the existence of this cortical map and its neuronal origin. The organization for center/surround suppression observed here at the level of the primary visual cortex is similar to those found in higher order areas in primates (e.g. area MT and could represent a strategy to optimize figure ground discrimination.

  3. Trophic Interactions between Generalist Predators and the Two Spotted Spide Mite, Tetranychus urticae in, Strawberry

    DEFF Research Database (Denmark)

    Jacobsen, Stine Kramer

    have been challenged by the polyphagous nature of T. urticae and its ability to reproduce exceedingly fast under optimal conditions. T. urticae have shown to be able to develop resistance towards chemical pesticides. Pest control by chemical means also have the unfortunate side-effect of reducing...... occurrence and diversity of predatory insects and predatory mites in Danish strawberry fields and surrounding vegetation is lacking, as is the knowledge of the potential of generalist insect predators to control T. urticae. The overall objective of this PhD thesis was to investigate the trophic interactions...

  4. 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

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    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

  5. 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.

  6. 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

  7. 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

  8. 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

  9. Trophic state and recreational value of Lake Mikołajskie

    Directory of Open Access Journals (Sweden)

    Sieńska Justyna

    2016-03-01

    Full Text Available Lakes along with their surroundings are an attractive landscape component that play an important role in recreation and relaxation. In Poland, the Great Masurian Lakeland, visited by a million tourists every year, is considered to be the most attractive lake area. However, tourist pressure has several negative effects which cause degradation of the water environment. The aim of this study was to determine the trophic state of Lake Mikołajskie which is a hub for sailing and motorboating traffic. Values of the trophic status index were calculated from the content of total phosphorus, chlorophyll a and Secchi disc visibility, according to the data from the Voivodeship Inspectorate for Environmental Protection. In summer, the concentration of total phosphorus was 0.019–0.042 mg dm−3 in 2013 and 0.022–0.055 mg dm−3 in 2014. The concentration of chlorophyll a was in the range of 8.3–45.0 μg dm−3 in 2013 and 8.9–22.0 μg dm−3 in 2014. The maximum visibility of Secchi disc reached 2.0 m (2013 and 1.8 m (2014. Based on the calculated, Lake Mikołajskie can be classified as a eutrophic lake. In order to protect lakes from degradation tourists should be educated about the rational use of surface waters and the surrounding catchment. However, it is not only the massive influx of tourists, but also the activity of residents (dictated by economic reasons that contribute to the pollution of lakes. Therefore, the development of tourism and the economy of the whole region should be harmonious and balanced so that the natural resources can serve us and future generations for as long as possible.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

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

    Science.gov (United States)

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

    2015-04-01

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

  15. 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).

  16. 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.

  17. 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).

  18. 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.

  19. 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

  20. Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat.

    Directory of Open Access Journals (Sweden)

    Francesca Pasotti

    Full Text Available The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands, a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii over time driving the benthic assemblages into a more compact trophic structure with

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

    Directory of Open Access Journals (Sweden)

    S.V. Bolgarska

    2016-08-01

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

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

    Directory of Open Access Journals (Sweden)

    Lujan Nathan K

    2012-07-01

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

  3. Issues Surrounding Children with Developmental Coordination Disorder

    Science.gov (United States)

    Sugden, David; Kirby, Amanda; Dunford, Carolyn

    2008-01-01

    Like other developmental disorders such as Attention Deficit Hyperactivity Disorder, specific language impairment and dyslexia, there is no shortage of debate surrounding the condition of Developmental Coordination Disorder. The present article takes a global view of many of these debatable issues, starting with definition and terminology, moving…

  4. Religion's relationship with social boundaries surrounding gender ...

    African Journals Online (AJOL)

    This paper examines the religious persuasion on the social boundaries surrounding gender. Gender has been a contentious issue that is associated with segregation, marginalization and differentiation between men and women. In the light of this, scholars' views on the subject matter were considered. Thus, this indicates ...

  5. Homophobic Discourse Surrounding the Female Athlete.

    Science.gov (United States)

    Veri, Maria J.

    1999-01-01

    Considers constructs and operation of homophobic discourse surrounding female athletes, employing Foucauldian notions of discipline and discourse and feminist critiques of the gendered body to depict female athletes as nonconformist to the discipline of femininity. The paper argues that homophobic discourse exists in response to this nonconformity…

  6. Smart Chips for Smart Surroundings -- 4S

    NARCIS (Netherlands)

    Schuler, Eberhard; König, Ralf; Becker, Jürgen; Rauwerda, G.K.; van de Burgwal, M.D.; Smit, Gerardus Johannes Maria; Cardoso, João M.P.; Hübner, Michael

    2011-01-01

    The overall mission of the 4S project (Smart Chips for Smart Surroundings) was to define and develop efficient flexible, reconfigurable core building blocks, including the supporting tools, for future Ambient System Devices. Reconfigurability offers the needed flexibility and adaptability, it

  7. Agroforestry practice in villages surrounding Nyamure former ...

    African Journals Online (AJOL)

    An assessment of fuel wood situation and the contribution of agroforestry and woodlot resources to the supply of household fuel wood requirements were carried out in ten villages surrounding Nyamure former refugee camp, Nyanza District in the Southern Province. A total of 158 households were surveyed in February ...

  8. Identification of β-SiC surrounded by relatable surrounding diamond ...

    Indian Academy of Sciences (India)

    It is difficult to detect -SiC using micro-Raman scattering, if it is surrounded by carbon medium. Here, -SiC is identified in the presence of a relatable surrounding diamond medium using subtle, but discernible Raman surface phonons. In this study, diamond/-SiC nanocomposite thin film system is considered in which ...

  9. Identification of β-SiC surrounded by relatable surrounding diamond ...

    Indian Academy of Sciences (India)

    Abstract. It is difficult to detect β-SiC using micro-Raman scattering, if it is surrounded by carbon medium. Here, β-SiC is identified in the presence of a relatable surrounding diamond medium using subtle, but discernible Raman surface phonons. In this study, diamond/β-SiC nanocomposite thin film system is considered in ...

  10. Methods of Assessing Noise Nuisance of Real Estate Surroundings

    Directory of Open Access Journals (Sweden)

    Szopińska Kinga

    2016-03-01

    Full Text Available Testing what factors create the market value of real estate is key information when preparing property valuations as well as other opinions and professional evaluations on the basis of which court verdicts or administrative decisions are made. One of the factors influencing the value of some real estate is the level of noise present in the surroundings, which can lead to the occurrence of noise nuisance negatively affecting social relations.

  11. Estimate of the trophic status of subarctic Imandra Lake

    Directory of Open Access Journals (Sweden)

    Terent'eva I. A.

    2017-03-01

    Full Text Available The object of study is Imandra Lake – the largest reservoir of the Murmansk region. The lake is being influenced by the long-term and multi-factorial activities of mining and ore processing industries, air pollution and energetics. Moreover, the drain of municipal sewage from the large settlements situated on the lake's watershed makes a serious contribution to water pollution. As a result the lake has accumulated a significant amount of pollutants and nutrients that resulted currently in an increase of the toxic load on the lake system. One of the main ecological problems also is the intensification of the anthropogenic eutrophication processes. The aim of this study is to evaluate the current trophic status of Imandra Lake using the trophic index (TSI with the average annual values of the parameters: chlorophyll, total nitrogen, total phosphorus, and total organic carbon and to find the dynamics of these parameters' changes during more than 20-year period. The study of the trophic status of Imandra Lake has been performed for the period 1991–2013 yrs. using the trophic state index developed by Carlson, Kratzer and Bresonik, Dunalska. According to the calculated values of the indexes Bolshaja Imandra Lake corresponds to eutrophic-mesotrophic trophic status, Yokostrovskaya Imandra Lake could be described as mesotrophic. Babinskaja Imandra Lake that subjected to essential nutrient loading is close to the oligotrophic trophic status. However, some parts of Babinskaja Imandra Lake refer to the mesotrophic state due to influence of industrial, household and heated water of the Kola atomic power station. Thus, this part of Imadra Lake could be considered as a meso-oligotrophic status. It has been established that currently nitrogen is a limiting factor for development of algae in Imandra Lake. Based on the mathematical Vollenweider model the critical phosphorus loading values to control such an important nutrient element as phosphorus have been

  12. 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.

  13. Trophic significance of the kelp Laminaria digitata (Lamour.) for the associated food web: a between-sites comparison

    Science.gov (United States)

    Schaal, Gauthier; Riera, Pascal; Leroux, Cédric

    2009-12-01

    This study aimed at establishing the trophic significance of the kelp Laminaria digitata for consumers inhabiting two rocky shores of Northern Brittany (France), displaying contrasted ecological conditions. The general trophic structure did not vary between these two sites, with a wide diversity of filter-feeders and predators, and only 14% of the species sampled belonging to the grazers' trophic group. The diversity of food sources fueling the food web appeared also similar. The food webs comprised four trophic levels and the prevalence of omnivory appeared relatively low compared to previous studies in the same area. Conversely, to the food web structure, which did not differ, the biochemical composition of L. digitata differed between the two sites, and was correlated to a larger diversity of grazers feeding on this kelp in sheltered conditions. This indicated that the spatial variability occurring in the nutritive value of L. digitata is likely to deeply affect the functioning of kelp-associated food webs. The contribution of L. digitata-derived organic matter to the diet of filter-feeders inhabiting these two environments was assessed using the mixing model Isosource, which showed the higher contribution of kelp matter in sheltered conditions. These results highlight the spatial variability that may occur in the functioning of kelp-associated food webs. Moreover, this suggests that hydrodynamics is likely to control the availability of kelp-derived organic matter to local filter-feeders, probably through an increase of detritus export in exposed areas.

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

    Science.gov (United States)

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

    2013-09-01

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

  15. Using a food-web model to assess the trophic structure and energy flows in Daya Bay, China

    Science.gov (United States)

    Chen, Zuozhi; Xu, Shannan; Qiu, Yongsong

    2015-12-01

    Daya Bay, is one of the largest and most important semi-closed bays along the southern coast of China. Due to the favorable geomorphological and climatic conditions, this bay has become an important conservation zone of aquatic germplasm resources in South China Sea. To characterize the trophic structure, ecosystem properties and keystone species, a food-web model for Daya Bay has been developed by the means of a mass-balance approach using the Ecopath with Ecosim software. The mean trophic transfer efficiency for the entire ecosystem as a whole is 10.9% while the trophic level II is 5.1%. The primary- and secondary-producers, including phytoplankton, zooplankton and micro-zoobenthos demonstrated the important overall impacts on the rest of the groups based on mixed trophic impact (MIT) analysis and are classified as the keystone groups. The analysis of ecosystem attributes indicated that ecosystem of Daya Bay can be categorized as an immature one and/or is in the degraded stage. A comparison of this model with other coastal ecosystems, including Kuosheng Bay, Tongoy Bay, Beibu Gulf and Cadiz Gulf, underpinned that the ecosystem of Daye Bay is an obviously stressed system and is more vulnerable to the external disturbance. In general, our study indicates that a holistic approach is needed to minimize the impacts of anthropogenic activities to ensure the sustainability of the ecosystem in the future.

  16. 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

  17. Modeling grating contrast discrimination dippers: The role of surround suppression.

    Science.gov (United States)

    To, Michelle P S; Chirimuuta, Mazviita; Tolhurst, David J

    2017-10-01

    We consider the role of nonlinear inhibition in physiologically realistic multineuronal models of V1 to predict the dipper functions from contrast discrimination experiments with sinusoidal gratings of different geometries. The dip in dipper functions has been attributed to an expansive transducer function, which itself is attributed to two nonlinear inhibitory mechanisms: contrast normalization and surround suppression. We ran five contrast discrimination experiments, with targets and masks of different sizes and configurations: small Gabor target/small mask, small target/large mask, large target/large mask, small target/in-phase annular mask, and small target/out-of-phase annular mask. Our V1 modeling shows that the results for small Gabor target/small mask, small target/large mask, large target/large mask configurations are easily explained only if the model includes surround suppression. This is compatible with the finding that an in-phase annular mask generates only little threshold elevation while the out-of-phase mask was more effective. Surrounding mask gratings cannot be equated with surround suppression at the receptive-field level. We examine whether normalization and surround suppression occur simultaneously (parallel model) or sequentially (a better reflection of neurophysiology). The Akaike Criterion Difference showed that the sequential model was better than the parallel, but the difference was small. The large target/large mask dipper experiment was not well fit by our models, and we suggest that this may reflect selective attention for its uniquely larger test stimulus. The best-fit model replicates some behaviors of single V1 neurons, such as the decrease in receptive-field size with increasing contrast.

  18. 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.

  19. 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.

  20. The functional biology and trophic role of krill (Thysanoessa raschii) in a Greenlandic fjord

    DEFF Research Database (Denmark)

    Agersted, Mette Dalgaard; Nielsen, Torkel Gissel; Munk, Peter

    2011-01-01

    ration of 1% body C d(-1). Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 mu m, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory...... and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily...

  1. A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems

    NARCIS (Netherlands)

    Donadi, S.; Austin, A. N.; Bergstrom, U.; Eriksson, B. K.; Hansen, J. P.; Jacobson, P.; Sundblad, G.; van Regteren, M.; Eklof, J. S.

    2017-01-01

    Trophic cascades occur in many ecosystems, but the factors regulating them are still elusive. We suggest that an overlooked factor is that trophic interactions (TIs) are often scale-dependent and possibly interact across spatial scales. To explore the role of spatial scale for trophic cascades, and

  2. Study and Application on Stability Classification of Tunnel Surrounding Rock Based on Uncertainty Measure Theory

    Directory of Open Access Journals (Sweden)

    Hujun He

    2014-01-01

    Full Text Available Based on uncertainty measure theory, a stability classification and order-arranging model of surrounding rock was established. Considering the practical engineering geologic condition, 5 factors that influence surrounding rock stability were taken into account and uncertainty measure function was obtained based on the in situ data. In this model, uncertainty influence factors were analyzed quantitatively and qualitatively based on the real situation; the weight of index was given based on information entropy theory; surrounding rock stability level was judged based on credible degree recognition criterion; and surrounding rock was ordered based on order-arranging criterion. Furthermore, this model was employed to evaluate 5 sections surrounding rock in Dongshan tunnel of Huainan. The results show that uncertainty measure method is reasonable and can have significance for surrounding rock stability evaluation in the future.

  3. Trait-mediated trophic interactions: is foraging theory keeping up?

    Science.gov (United States)

    Steven F. Railsback; Bret C. Harvey

    2013-01-01

    Many ecologists believe that there is a lack of foraging theory that works in community contexts, for populations of unique individuals each making trade-offs between food and risk that are subject to feedbacks from behavior of others. Such theory is necessary to reproduce the trait-mediated trophic interactions now recognized as widespread and strong. Game theory can...

  4. Trophic relationships of hake ( Merluccius capensis and M ...

    African Journals Online (AJOL)

    The trophic relationships of two hake species (Merluccius capensis and M. paradoxus) and three shark species (Centrophorus squamosus, Deania calcea and D. profundorum) were investigated using nitrogen and carbon stable isotope signatures (δ15N and δ13C) of their muscle tissues. The sharks were more enriched in ...

  5. Trophic structure and biomass distribution of macrobenthos on ...

    African Journals Online (AJOL)

    The trophic structure and biomass of macrobenthos on both wave-sheltered, rocky intertidal shores and semi-exposed ones at seven localities in the Tsitsikamma Marine Protected Area were compared. In the Cochlear zone and entire intertidal (Cochlear- and Balanoid zones combined) biomass values of invertebrates and ...

  6. Trophic transfer of radioisotopes in Mediterranean sponges through bacteria consumption.

    Science.gov (United States)

    Lacoue-Labarthe, Thomas; Warnau, Michel; Beaugeard, Laureen; Pascal, Pierre-Yves

    2016-02-01

    Numerous field studies highlighted the capacities of marine sponges to bioaccumulate trace elements and assessed their potential as biomonitors of the marine environment. Experimental works demonstrated that dissolved metals and radionuclides can be taken up directly by sponge tissues but, to the best of our knowledge, little is known on the contribution of the dietary pathway through the consumption of contaminated bacteria considered as one of the trophic source in sponge diet. Objectives of this work are to study trophic transfer of radiotracers (110m)Ag, (241)Am, (109)Cd, (57)Co, (134)Cs, (54)Mn and (65)Zn from the marine bacteria Pseudomonas stutzeri to the Mediterranean sponges Aplysina cavernicola and Ircinia oros. P. stutzeri efficiently bioaccumulated trace elements in our culture experimental conditions with CF comprised between 10(5) and 10(7) after 48 h of growth in radiolabeled medium. When fed with these radiolabelled bacteria, A. cavernicola took up around 60% of radiotracers accumulated in trophic source except (134)Cs for which only 8% has been transferred from bacteria to sponge. Contrasting to this, I. oros retained only 7% of (110m)Ag, (109)Cd and (65)Zn counted in bacteria, but retained 2-fold longer accumulated metals in its tissues. The sponge inter-specific differences of accumulation and depuration following a trophic exposure are discussed with respect to the structure and the clearance capacities of each species. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Trophic structure and biomass distribution on two East Cape rocky ...

    African Journals Online (AJOL)

    1980-01-12

    Jan 12, 1980 ... Trophic structure and biomass distribution on two. East Cape rocky shores. A Mclachlan, H.W. Lombard and S. Louwrens. Zoology Department, University of Port Elizabeth, Port Elizabeth. The distribution and biomass of macrofauna and macroalgae is described for two intertidal rocky shores near Port Eliza ...

  8. Trophic interactions amongst the plankton in the temporarily open ...

    African Journals Online (AJOL)

    The trophic interactions between bacteria, phytoplankton, nanoflagellates (2–20 µm), microzooplankton (20–200 µm) and mesozooplankton (200–2 000 µm) were investigated in winter and summer in the temporarily open/closed East Kleinemonde Estuary, Eastern Cape. During winter the phytoplankton community was ...

  9. The trophic position of planktonic ciliate populations in the food ...

    African Journals Online (AJOL)

    The trophic role of planktonic ciliates was investigated in the food webs of 17 East African lakes of different salinity and trophy. Experiments with 1µm latex beads showed that Cyclidium, Halteria, Dysteria, Aspidisca and Vorticella are bacterivores. Examination of food vacuole contents showed that the ciliate communities ...

  10. 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

  11. 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

  12. 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

  13. Trophic Ecology of Some Common Juvenile Fish Species in Mtwapa ...

    African Journals Online (AJOL)

    The trophic status of common fish species in Mtwapa creek on the Kenyan coast was studied. Both the qualitative and quantitative spectra of the diets of these fish species were investigated. It was found that the eight most abundant fish species, Sardinella gibbosa, Pellona ditchella, Spratelloides delicatilus, Atherinomorous ...

  14. Trophic state categorisation and assessment of water quality in ...

    African Journals Online (AJOL)

    ... water transparency, ammonia, nitrogen, nitrates, total and reactive phosphorus. Despite slight fluctuations/variations, water quality in the Manjirenji Dam was generally fair, with a CCME value averaging 78.1, and the Carlson Trophic State Index reflecting oligotrophy. Non-significant differences in water quality parameters ...

  15. Trophic transfer of metal-based nanoparticles in aquatic environments

    DEFF Research Database (Denmark)

    Tangaa, Stine Rosendal; Selck, Henriette; Winther-Nielsen, Margrethe

    2016-01-01

    transformations of Me-ENPs, (2) uptake and accumulation in prey organisms, (3) internal fate and localization in the prey, and (4) digestive physiology of the predator. Whilst much research has been conducted on the first two of these factors, key knowledge gaps exist in our understanding of how Me-ENP trophic...

  16. Squid as trophic bridges for parasite flow within marine ecosystems ...

    African Journals Online (AJOL)

    Squid as trophic bridges for parasite flow within marine ecosystems: The case of anisakis simplex (nematoda: Anisakidae), or when the wrong way can be right. E Abollo, C Gestal, A López, AF González, A Guerra, S Pascual ...

  17. Assessing Trophic Position and Mercury Accumulation in Sanpping Turtles

    Science.gov (United States)

    This study determined the trophic position and the total mercury concentrations of snapping turtles (Chelydra serpentina) captured from 26 freshwater sites in Rhode Island. Turtles were captured in baited wire cages, and a non-lethal sampling technique was used in which tips of ...

  18. Changes in the trophic structure of the southern Benguela before ...

    African Journals Online (AJOL)

    Ecopath with Ecosim was used to construct and compare mass-balanced foodweb models of the southern Benguela ecosystem, representing the following eras of ... trophic control mechanism becoming the dominant driver of ecosystem dynamics, increasing the impact of environmental events including climate change.

  19. Assessing trophic adaptability is critical for understanding the ...

    African Journals Online (AJOL)

    Assessing trophic adaptability is critical for understanding the response of predatory fishes to climate change: a case study of Pomatomus saltatrix in a global hotspot. ... fishes biomass in a global hotspot (the coastal region of southern Angola, southern Africa) to gain an understanding of the tropic adaptability of the species.

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

    Science.gov (United States)

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

    2017-08-15

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

  1. 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.

  2. 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.

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

    Directory of Open Access Journals (Sweden)

    JPA Pagotto

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

  4. Opportunity's Surroundings on Sol 1818 (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. This view is presented as a polar projection with geometric seam correction. North is at the top. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  5. Opportunity's Surroundings on Sol 1818 (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. This view is presented as a vertical projection with geometric seam correction. North is at the top. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  6. Spirit's Surroundings on 'West Spur,' Sol 305

    Science.gov (United States)

    2005-01-01

    This 360-degree panorama shows the terrain surrounding NASA's Mars Exploration Rover Spirit as of the rover's 305th martian day, or sol, (Nov. 11, 2004). At that point, Spirit was climbing the 'West Spur' of the 'Columbia Hills.' The rover had just finished inspecting a rock called 'Lutefisk' and was heading uphill toward an area called 'Machu Picchu.' Spirit used its navigational camera to take the images combined into this mosaic. The rover's location when the images were taken is catalogued as the mission's site 89, position 205. The view is presented here as a cylindrical projection with geometric seam correction.

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

    Science.gov (United States)

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

    2014-12-15

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

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

    Directory of Open Access Journals (Sweden)

    Matthew J Perkins

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

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  11. 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.

  12. Crust Structure Data of Seas Surrounding Turkey

    International Nuclear Information System (INIS)

    Maden, N.; Gelisli, K.

    2007-01-01

    Black Sea, Aegean, Mediterranean and Marmara Sea, which surround the Turkey, have not been examined with respect to the Geological, Geophysical and other natural sciences sufficiently. In fact, it is not attach importance the Turkish seas adequately and abandoned with respect to the scientific researches. The most important reason of this situation is the lack of the education of the Marine Sciences in the Turkish Universities. In this study, it is tried to construct a crustal structure data base of the surrounding seas of the Turkey by collecting crustal structure data sets done by different authors in different times so far. The data acquired in the base are collected from different data base sources by dragging. The Moho depth in the eastern and western basin of the Black sea is 22 km and 19 km, respectively. In the Marmara Sea the Moho depth is 24 km. The moho value in the southern Aegean is 20 km, in the northern Aegean the moho depth is 30 km. on the other hand, the moho depth value in the eastern and western basin of the Mediterranean Sea are 15-20 km and 25-30 km, respectively

  13. 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

  14. 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

  15. Natural occurring radioactivity in Palmyra and its surrounding

    International Nuclear Information System (INIS)

    Al-Masri, M. S.; Shwekani, R.; Raja, G.; Hushari, M.; Al-Hent, R.; Issa, M.

    2006-06-01

    In this work, the natural radiation background has been carried out for Palmyra city and its surroundings area. The study has covered gamma radiation measurements, indoor radon gas concentration and radionuclides levels in environmental samples (soil, water, plat). The results showed that indoor radon gas concentrations and radiation exposure rates are within the background levels. Also, the results showed that there is no artificial radiation in the area and there is no correlation between the natural radiation levels and the reported cancer cases. Therefore, the reported cancer cases in this area may be due to non-radiation cases, which must be investigated, or they are within the natural levels in Syria unless accurate statistics proves the opposite. (author)

  16. 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.

  17. A guideline to study the feasibility domain of multi-trophic and changing ecological communities.

    Science.gov (United States)

    Song, Chuliang; Rohr, Rudolf P; Saavedra, Serguei

    2018-04-24

    The feasibility domain of an ecological community can be described by the set of environmental abiotic and biotic conditions under which all co-occurring and interacting species in a given site and time can have positive abundances. Mathematically, the feasibility domain corresponds to the parameter space compatible with positive (feasible) solutions at equilibrium for all the state variables in a system under a given model of population dynamics. Under specific dynamics, the existence of a feasible equilibrium is a necessary condition for species persistence regardless of whether the feasible equilibrium is dynamically stable or not. Thus, the size of the feasibility domain can also be used as an indicator of the tolerance of a community to random environmental variations. This has motivated a rich research agenda to estimate the feasibility domain of ecological communities. However, these methodologies typically assume that species interactions are static, or that input and output energy flows on each trophic level are unconstrained. Yet, this is different to how communities behave in nature. Here, we present a step-by-step quantitative guideline providing illustrative examples, computational code, and mathematical proofs to study systematically the feasibility domain of ecological communities under changes of interspecific interactions and subject to different constraints on the trophic energy flows. This guideline covers multi-trophic communities that can be formed by any type of interspecific interactions. Importantly, we show that the relative size of the feasibility domain can significantly change as a function of the biological information taken into consideration. We believe that the availability of these methods can allow us to increase our understanding about the limits at which ecological communities may no longer tolerate further environmental perturbations, and can facilitate a stronger integration of theoretical and empirical research. Copyright

  18. 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

  19. 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.

  20. Bioaccumulation and trophic transfer of dioxins in marine copepods and fish

    International Nuclear Information System (INIS)

    Zhang Qiong; Yang Liuyan; Wang Wenxiong

    2011-01-01

    Despite the great concerns about dioxins in the marine environments, the biokinetics and bioaccumulation of these compounds in marine organisms remains little known. Using radioactive tracers the aqueous uptake, dietary assimilation efficiency, and elimination of dioxins were measured in marine phytoplankton, copepods and seabream. The calculated uptake rate constant of dioxins decreased with increasing trophic levels, whereas the dietary assimilation efficiency (AE) was 28.5-57.6% in the copepods and 36.6-70.2% in the fish. The dietary AE was highly dependent on the food concentrations and food type. The elimination rate constant of dioxin in the copepods varied with different exposure pathways as well as food concentration and food type. Biokinetic calculation showed that dietary accumulation was the predominant pathway for dioxin accumulation in marine copepods and fish. Aqueous uptake can be an important pathway only when the bioconcentration of dioxins in the phytoplankton was low. - Highlights: → Radiotracer was used to quantify the biokinetics of dioxins in a marine food chain. → Aqueous uptake rate of dioxins decreased with increasing trophic levels. → Dietary assimilation efficiencies were comparable between the copepods and the fish. → Both food type and density significantly affected the dietary assimilation of dioxins. → Diet was the predominant pathway for dioxin accumulation in marine copepods and fish. - Biokinetic calculation showed that dietary accumulation was the predominant pathway for dioxin accumulation in marine copepods and fish.

  1. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks.

    Science.gov (United States)

    Fröbisch, Nadia B; Fröbisch, Jörg; Sander, P Martin; Schmitz, Lars; Rieppel, Olivier

    2013-01-22

    The biotic recovery from Earth's most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in today's marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian.

  2. Opportunity's Surroundings After Sol 1820 Drive (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). This view is presented as a polar projection with geometric seam correction. North is at the top. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock.

  3. Opportunity's Surroundings After Sol 1820 Drive

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). South is at the center; north at both ends. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock. This view is presented as a cylindrical projection with geometric seam correction.

  4. Opportunity's Surroundings on Sol 1798 (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. This view is presented as a vertical projection with geometric seam correction. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  5. Opportunity's Surroundings on Sol 1798 (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. This view is presented as a polar projection with geometric seam correction. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  6. Opportunity's Surroundings After Sol 1820 Drive (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). This view is presented as a vertical projection with geometric seam correction. North is at the top. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock.

  7. Lovelock black holes surrounded by quintessence

    Science.gov (United States)

    Ghosh, Sushant G.; Maharaj, Sunil D.; Baboolal, Dharmanand; Lee, Tae-Hun

    2018-02-01

    Lovelock gravity consisting of the dimensionally continued Euler densities is a natural generalization of general relativity to higher dimensions such that equations of motion are still second order, and the theory is free of ghosts. A scalar field with a positive potential that yields an accelerating universe has been termed quintessence. We present exact black hole solutions in D-dimensional Lovelock gravity surrounded by quintessence matter and also perform a detailed thermodynamical study. Further, we find that the mass, entropy and temperature of the black hole are corrected due to the quintessence background. In particular, we find that a phase transition occurs with a divergence of the heat capacity at the critical horizon radius, and that specific heat becomes positive for r_hblack hole to become thermodynamically stable.

  8. Towards Semantic Understanding of Surrounding Vehicular Maneuvers

    DEFF Research Database (Denmark)

    Kristoffersen, Miklas Strøm; Dueholm, Jacob Velling; Satzoda, Ravi K.

    2016-01-01

    This paper proposes the use of multiple low-cost visual sensors to obtain a surround view of the ego-vehicle for semantic understanding. A multi-perspective view will assist the analysis of naturalistic driving studies (NDS), by automating the task of data reduction of the observed sequences...... is tested on ten sequences of real-world data collected on U. S. highways. The results show the potential use of multiple low-cost visual sensors for semantic understanding around the ego-vehicle....... into events. A user-centric vision-based framework is presented using a vehicle detector and tracker in each separate perspective. Multi-perspective trajectories are estimated and analyzed to extract 14 different events, including potential dangerous behaviors such as overtakes and cut-ins. The system...

  9. Global change in the trophic functioning of marine food webs

    DEFF Research Database (Denmark)

    Maureaud, Aurore; Gascuel, Didier; Colléter, Mathieu

    2017-01-01

    and life history traits of marine species, we tested the hypothesis that anthropogenic ecological impacts may have led to changes in the global parameters defining the transfers of biomass within the food web. First, we developed two indicators to assess such changes: the Time Cumulated Indicator (TCI......The development of fisheries in the oceans, and other human drivers such as climate warming, have led to changes in species abundance, assemblages, trophic interactions, and ultimately in the functioning of marine food webs. Here, using a trophodynamic approach and global databases of catches......) measuring the residence time of biomass within the food web, and the Efficiency Cumulated Indicator (ECI) quantifying the fraction of secondary production reaching the top of the trophic chain. Then, we assessed, at the large marine ecosystem scale, the worldwide change of these two indicators over the 1950...

  10. Trait-mediated trophic interactions: is foraging theory keeping up?

    Science.gov (United States)

    Railsback, Steven F; Harvey, Bret C

    2013-02-01

    Many ecologists believe that there is a lack of foraging theory that works in community contexts, for populations of unique individuals each making trade-offs between food and risk that are subject to feedbacks from behavior of others. Such theory is necessary to reproduce the trait-mediated trophic interactions now recognized as widespread and strong. Game theory can address feedbacks but does not provide foraging theory for unique individuals in variable environments. 'State- and prediction-based theory' (SPT) is a new approach that combines existing trade-off methods with routine updating: individuals regularly predict future food availability and risk from current conditions to optimize a fitness measure. SPT can reproduce a variety of realistic foraging behaviors and trait-mediated trophic interactions with feedbacks, even when the environment is unpredictable. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Diversity and stability of an estuarine trophic network

    OpenAIRE

    Lobry, Jeremy; David, V; Pasquaud, S; Lepage, M; Sautour, B; Rochard, E

    2008-01-01

    Estuarine areas provide highly valuable ecosystem benefits for human populations, despite being under intense demographic, economic and ecological pressures. Hence, an understanding of the structure and function of estuarine ecosystems is essential for understanding the persistence and stability of these ecosystems and their response to perturbations. This study synthesises available data and knowledge about the Gironde estuary (SW France) in a mass-balanced trophic model to illustrate potent...

  12. Analyzing the trophic link between the mesopelagic microbial loop and zooplankton from observed depth profiles of bacteria and protozoa

    Directory of Open Access Journals (Sweden)

    T. Tanaka

    2005-01-01

    Full Text Available It is widely recognized that organic carbon exported to the ocean aphotic layer is significantly consumed by heterotrophic organisms such as bacteria and zooplankton in the mesopelagic layer. However, very little is known for the trophic link between bacteria and zooplankton or the function of the microbial loop in this layer. In the northwestern Mediterranean, recent studies have shown that viruses, bacteria, heterotrophic nanoflagellates, and ciliates distribute down to 2000 m with group-specific depth-dependent decreases, and that bacterial production decreases with depth down to 1000 m. Here we show that such data can be analyzed using a simple steady-state food chain model to quantify the carbon flow from bacteria to zooplankton over the mesopelagic layer. The model indicates that bacterial mortality by viruses is similar to or 1.5 times greater than that by heterotrophic nanoflagellates, and that heterotrophic nanoflagellates transfer little of bacterial production to higher trophic levels.

  13. The Aquatic Trophic Ecology of Suisun Marsh, San Francisco Estuary, California, During Autumn in a Wet Year

    Directory of Open Access Journals (Sweden)

    Robert E. Schroeter

    2015-09-01

    Full Text Available doi: http://dx.doi.org/10.15447/sfews.v13iss3art6Using stable isotopes of carbon (δ13C and nitrogen (δ15N and mixing models, we investigated the trophic levels and carbon sources of invertebrates and fishes of a large tidal marsh in the San Francisco Estuary. Our goal was to better understand an estuarine food web comprised of native and alien species. We found the following: (1 the food web was based largely on carbon from phytoplankton and emergent-aquatic and terrestrial vegetation, but carbon from submerged aquatic vegetation and phytobenthos was also used; (2 alien species increased the complexity of the food web by altering carbon-flow pathways and by occupying trophic positions different from native species; and (3 most consumers were dietary generalists.

  14. Subcellular controls of mercury trophic transfer to a marine fish

    International Nuclear Information System (INIS)

    Dang Fei; Wang Wenxiong

    2010-01-01

    Different behaviors of inorganic mercury [Hg(II)] and methylmercury (MeHg) during trophic transfer along the marine food chain have been widely reported, but the mechanisms are not fully understood. The bioavailability of ingested mercury, quantified by assimilation efficiency (AE), was investigated in a marine fish, the grunt Terapon jarbua, based on mercury subcellular partitioning in prey and purified subcellular fractions of prey tissues. The subcellular distribution of Hg(II) differed substantially among prey types, with cellular debris being a major (49-57% in bivalves) or secondary (14-19% in other prey) binding pool. However, MeHg distribution varied little among prey types, with most MeHg (43-79%) in heat-stable protein (HSP) fraction. The greater AEs measured for MeHg (90-94%) than for Hg(II) (23-43%) confirmed the findings of previous studies. Bioavailability of each purified subcellular fraction rather than the proposed trophically available metal (TAM) fraction could better elucidate mercury assimilation difference. Hg(II) associated with insoluble fraction (e.g. cellular debris) was less bioavailable than that in soluble fraction (e.g. HSP). However, subcellular distribution was shown to be less important for MeHg, with each fraction having comparable MeHg bioavailability. Subcellular distribution in prey should be an important consideration in mercury trophic transfer studies.

  15. Trophic and neurotrophic factors in human pituitary adenomas (Review).

    Science.gov (United States)

    Spoletini, Marialuisa; Taurone, Samanta; Tombolini, Mario; Minni, Antonio; Altissimi, Giancarlo; Wierzbicki, Venceslao; Giangaspero, Felice; Parnigotto, Pier Paolo; Artico, Marco; Bardella, Lia; Agostinelli, Enzo; Pastore, Francesco Saverio

    2017-10-01

    The pituitary gland is an organ that functionally connects the hypothalamus with the peripheral organs. The pituitary gland is an important regulator of body homeostasis during development, stress, and other processes. Pituitary adenomas are a group of tumors arising from the pituitary gland: they may be subdivided in functional or non-functional, depending on their hormonal activity. Some trophic and neurotrophic factors seem to play a key role in the development and maintenance of the pituitary function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. Several lines of evidence suggest that trophic and neurotrophic factors may be involved in pituitary function, thus suggesting a possible role of the trophic and neurotrophic factors in the normal development of pituitary gland and in the progression of pituitary adenomas. Additional studies might be necessary to better explain the biological role of these molecules in the development and progression of this type of tumor. In this review, in light of the available literature, data on the following neurotrophic factors are discussed: ciliary neurotrophic factor (CNTF), transforming growth factors β (TGF‑β), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), vascular endothelial growth inhibitor (VEGI), fibroblast growth factors (FGFs) and epidermal growth factor (EGF) which influence the proliferation and growth of pituitary adenomas.

  16. Factors regulating trophic status in a large subtropical reservoir, China.

    Science.gov (United States)

    Xu, Yaoyang; Cai, Qinghua; Han, Xinqin; Shao, Meiling; Liu, Ruiqiu

    2010-10-01

    We evaluated a 4-year data set (July 2003 to June 2007) to assess the trophic state and its limiting factors of Three-Gorges Reservoir (TGR), China, a large subtropical reservoir. Based on Carlson-type trophic state index (TSI)(CHL), the trophic state of the system was oligotrophic (TSI(S) TSI(TP) and TSI(TN) were higher than the critical value of eutrophic state (TSI(S) > 50). Using Carlson's (1991) two-dimensional approach, deviations of the TSI(S) indicated that factors other than phosphorus and nitrogen limited algal growth and that nonalgal particles affected light attenuation. These findings were further supported by the significant correlation among the values of TSI(CHL) - TSI(SD) and nonvolatile suspended solids and water residence time. The logarithmic model showed that an equivalent TSI(CHL) and TSI(SD) could be found at tau = 54 days in the TGR (Fig. 7). Accordingly, nonalgal particulates dominated light attenuation and limited algal biomass of the reservoir when tau < 54 days.

  17. Trophic niche shifts driven by phytoplankton in sandy beach ecosystems

    Science.gov (United States)

    Bergamino, Leandro; Martínez, Ana; Han, Eunah; Lercari, Diego; Defeo, Omar

    2016-10-01

    Stable isotopes (δ13C and δ15N) together with chlorophyll a and densities of surf diatoms were used to analyze changes in trophic niches of species in two sandy beaches of Uruguay with contrasting morphodynamics (i.e. dissipative vs. reflective). Consumers and food sources were collected over four seasons, including sediment organic matter (SOM), suspended particulate organic matter (POM) and the surf zone diatom Asterionellopsis guyunusae. Circular statistics and a Bayesian isotope mixing model were used to quantify food web differences between beaches. Consumers changed their trophic niche between beaches in the same direction of the food web space towards higher reliance on surf diatoms in the dissipative beach. Mixing models indicated that A. guyunusae was the primary nutrition source for suspension feeders in the dissipative beach, explaining their change in dietary niche compared to the reflective beach where the proportional contribution of surf diatoms was low. The high C/N ratios in A. guyunusae indicated its high nutritional value and N content, and may help to explain the high assimilation by suspension feeders at the dissipative beach. Furthermore, density of A. guyunusae was higher in the dissipative than in the reflective beach, and cell density was positively correlated with chlorophyll a only in the dissipative beach. Therefore, surf diatoms are important drivers in the dynamics of sandy beach food webs, determining the trophic niche space and productivity. Our study provides valuable insights on shifting foraging behavior by beach fauna in response to changes in resource availability.

  18. 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.

  19. The relative importance of herbivory and carnivory on the distribution of energy in a stochastic tri-trophic food web.

    Science.gov (United States)

    Ballantyne, Ford

    2004-02-07

    A three-state, discrete-time Markov chain is used to model the dynamics of energy flow in a tri-trophic food web. The distribution of energy in the three trophic levels is related to the rates of flow between the trophic levels and calculated for the entire range of possible flow values. These distributions are then analysed for stability and used to test the idea that plants are resource-limited and herbivores are predation-limited. Low rates of death and decomposition, when coupled with low rates of herbivory and carnivory, tend to destabilize this food web. Food webs with higher rates of death and decomposition are relatively more stable regardless of rates of herbivory and carnivory. Plants are more prone to resource-limitation and herbivores are, in general, limited by their predators, which supports Hairston et al. (Am. Nat. 94 (1960) 421). The rate of decomposition often mediates the roles of top-down and bottom-up control of energy flow in the food web.

  20. 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

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

    OpenAIRE

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

    2014-01-01

    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 C...

  2. 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.

  3. Identification of trophic interactions within an estuarine food web (northern New Zealand) using fatty acid biomarkers and stable isotopes

    Science.gov (United States)

    Alfaro, Andrea C.; Thomas, François; Sergent, Luce; Duxbury, Mark

    2006-10-01

    Fatty acid biomarkers and stable isotope signatures were used to identify the trophic dynamics of a mangrove/seagrass estuarine food web at Matapouri, northern New Zealand. Specific fatty acids were used to identify the preferred food sources (i.e., mangroves, seagrass, phytoplankton, macroalgae, bacteria, and zooplankton) of dominant fauna (i.e., filter feeders, grazing snails, scavenger/predatory snails, shrimp, crabs, and fish), and their presence in water and sediment samples throughout the estuary. The diets of filter feeders were found to be dominated by dinoflagellates, whereas grazers showed a higher diatom contribution. Bacteria associated with organic debris on surface sediments and brown algal ( Hormosira banksii) material in the form of suspended organic matter also accounted for a high proportion of most animal diets. Animals within higher trophic levels had diverse fatty acid profiles, revealing their varied feeding strategies and carbon sources. The stable isotope (δ 13C and δ 15N) analyses of major primary producers and consumers/predators revealed a trend of 15N enrichment with increasing trophic level, while δ 13C values provided a generally good description of carbon flow through the food web. Overall results from both fatty acid profiles and stable isotopes indicate that a variety of carbon sources with a range of trophic pathways typify this food web. Moreover, none of the animals studied was dependent on a single food source. This study is the first to use a comprehensive fatty acid biomarker and stable isotope approach to investigate the food web dynamics within a New Zealand temperate mangrove/seagrass estuary. This quantitative research may contribute to the currently developing management strategies for estuaries in northern New Zealand, especially for those perceived to have expanding mangrove fringes.

  4. Xenobiotic metabolism markers in marine fish with different trophic strategies and their relationship to ecological variables.

    Science.gov (United States)

    Solé, M; Rodríguez, S; Papiol, V; Maynou, F; Cartes, J E

    2009-01-01

    Nine fish species of commercial interest from six teleost families and two species of elasmobranchs were selected for characterisation of hepatic biomarkers used in early-warning assessment of pollutant exposure. The sampling was carried out in front of the Barcelona coast (NW Mediterranean) during December 2006 at shelf (53 m) and slope (660 m) depths. The enzymes considered included the antioxidant defence catalase (CAT) and glutathione reductase (GR), phase I ethoxyresorufin O-deethylase (EROD) and phase II glutathione S-transferase (GST). Protein yield (PY) was used as a general marker of hepatic protein synthesis. Significant interspecies differences were evidenced, although each marker varied independently. Enzymatic activities in teleosts were higher than in elasmobranchs; they were very low in Scyliorhinus canicula (mainly a benthic feeder), but not so low in Galeus melastomus (pelagic feeder). In relation to depth, shallow water, shelf-living species had higher metabolic activities. Trophic variables were significantly related to PY and EROD activity, and were especially high in benthic/suprabenthic feeders. Trophic level (deduced from stable isotopy) and stomach fullness were associated with all hepatic markers, except GR. Swimming capacity was related to all hepatic enzymes. Our findings can be applied, not only from the perspective of conservation ecology regarding pollution, but also in fisheries, due to the economic interest of the species involved.

  5. 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.

  6. Description of the East Brazil Large Marine Ecosystem using a trophic model

    Directory of Open Access Journals (Sweden)

    Kátia M.F. Freire

    2008-09-01

    Full Text Available The objective of this study was to describe the marine ecosystem off northeastern Brazil. A trophic model was constructed for the 1970s using Ecopath with Ecosim. The impact of most of the forty-one functional groups was modest, probably due to the highly reticulated diet matrix. However, seagrass and macroalgae exerted a strong positive impact on manatee and herbivorous reef fishes, respectively. A high negative impact of omnivorous reef fishes on spiny lobsters and of sharks on swordfish was observed. Spiny lobsters and swordfish had the largest biomass changes for the simulation period (1978-2000; tunas, other large pelagics and sharks showed intermediate rates of biomass decline; and a slight increase in biomass was observed for toothed cetaceans, large carnivorous reef fishes, and dolphinfish. Recycling was an important feature of this ecosystem with low phytoplankton-originated primary production. The mean transfer efficiency between trophic levels was 11.4%. The gross efficiency of the fisheries was very low (0.00002, probably due to the low exploitation rate of most of the resources in the 1970s. Basic local information was missing for many groups. When information gaps are filled, this model may serve more credibly for the exploration of fishing policies for this area within an ecosystem approach.

  7. Determination of toxicity assays, trophic state index, and physicochemical parameters on Piracicaba River and Itapeva Stream

    Directory of Open Access Journals (Sweden)

    Larissa de Assunção Rodrigues

    2015-04-01

    Full Text Available Anthropogenic activity has a great impact on aquatic environments, causing changes in biodiversity and the environment. In an attempt to determine pollution levels, we established physicochemical parameters, a trophic state index and toxicity assays. The Piracicaba River is an important water body that receives xenobiotic waste from industry, domestic activities and agriculture. These pollutants are released directly into the river or by streams like Itapeva Stream, which discharges into the river. The goals of this work were to analyze the toxicity factor for Daphnia magna (TFD, trophic state index (TSI, pH, conductivity, temperature and dissolved oxygen in the Piracicaba River and in the Itapeva Stream from one monthly collection in the months of May, June and August 2011. In the Piracicaba River was not found toxicity, while in May, June and August the TFD was 1, 8 and 1, respectively. The TSI varied from mesotrophic to eutrophic in the river and in the stream from ultraoligotrophic to mesotrophic. The medium of conductivity for the Itapeva Stream was 479.5 µS.cm-1 and for the Piracicaba River was 219.8 µS.cm-1. The dissolved oxygen in the Piracicaba River varied from 6.89 to11.36 mg.L-1 and in the Itapeva Stream from 0.92 to 6.31 mg.L-1. Based upon the results, both hydric bodies were eutrophic, and the Itapeva Stream was classified as unsuitable for maintaining aquatic life.

  8. Competition among penguins and cetaceans reveals trophic cascades in the western Ross Sea, Antarctica.

    Science.gov (United States)

    Ainley, David G; Ballard, Grant; Dugger, Katie M

    2006-08-01

    An apparent trophic cascade that appears during summer in the western Ross Sea, Antarctica, explains why the Antarctic silverfish (Pleuragramma antarcticum) there becomes cannibalistic; its principal prey, crystal krill (Euphausia crystallorophias) becomes scarce; and the diatom community is minimally grazed compared to adjacent areas. The krill is the major grazer of diatoms. On the basis of fieldwork at Ross Island, we suggest that the cascade results from foraging by unusually numerous Adélie Penguins (Pygoscelis adeliae), minke whales (Balaenoptera bonaerensis), and fish-eating killer whales (Orcinus orca). These species and other top predators apparently deplete the krill and silverfish. In drawing our conclusions, we were aided by two "natural experiments." In one "experiment," large, grounded icebergs altered the seasonal pattern of change in regional sea-ice cover, but not the seasonal change in penguin diet and foraging behavior that was also detected during the pre-iceberg era. In the other "experiment," a short-term polynya (opening in the ice) brought penguins and whales together in a confined area, this time altering both penguin diet and foraging behavior. We conclude that the foraging of penguins and whales, and not a formerly hypothesized seasonal decrease in sea-ice cover, explains (1) the annual switch in the penguins' prey from krill to silverfish, (2) the subsequent lengthening of penguin foraging trips, and (3) a marked decline of cetaceans in the area later in the season. Reduction in the middle-trophic-level prey is expressed in the relaxed grazing pressure on phytoplankton.

  9. Catchment vegetation and temperature mediating trophic interactions and production in plankton communities.

    Science.gov (United States)

    Finstad, Anders G; Nilsen, Erlend B; Hendrichsen, Ditte K; Schmidt, Niels Martin

    2017-01-01

    Climatic factors influence the interactions among trophic levels in an ecosystem in multiple ways. However, whereas most studies focus on single factors in isolation, mainly due to interrelation and correlation among drivers complicating interpretation and analyses, there are still only few studies on how multiple ecosystems respond to climate related factors at the same time. Here, we use a hierarchical Bayesian model with a bioenergetic predator-prey framework to study how different climatic factors affect trophic interactions and production in small Arctic lakes. Natural variation in temperature and catchment land-cover was used as a natural experiment to exemplify how interactions between and production of primary producers (phytoplankton) and grazers (zooplankton) are driven by direct (temperature) and indirect (catchment vegetation) factors, as well as the presence or absence of apex predators (fish). The results show that increased vegetation cover increased phytoplankton growth rate by mediating lake nutrient concentration. At the same time, increased temperature also increased grazing rates by zooplankton. Presence of fish increased zooplankton mortality rates, thus reducing grazing. The Arctic is currently experiencing an increase in both temperature and shrub vegetation cover due to climate change, a trend, which is likely to continue. Our results point towards a possible future general weakening of zooplankton grazing on phytoplankton and greening of arctic lakes with increasing temperatures. At the same time, the impact of the presence of an apex predator indicate considerable local variation in the response. This makes direction and strength of global change impacts difficult to forecast.

  10. Evaluation of the potential for trophic transfer of roxithromycin along an experimental food chain.

    Science.gov (United States)

    Ding, Jiannan; Lu, Guanghua; Liu, Jianchao; Zhang, Zhenghua

    2015-07-01

    Pharmaceuticals have been recognized as a new class of environmental pollutants in recent years. But data about their potential for transfer and biomagnification in aquatic food chains are still lacking. In this study, bioaccumulation of the macrolide antibiotic roxithromycin (ROX) was determined in an experimental aquatic food chain involving the green algae Scenedesmus obliquus, the water flea Daphnia magna and the crucian carp Carassius auratus. After 48 h of exposure, S. obliquus accumulated ROX from media, with bioconcentration factors (BCFs) of 74.6, 46.3, and 24.5 l kg(-1) at nominal exposure concentrations of 4, 20, and 100 μg l(-1), respectively. After 48 h of feeding ROX-contaminated algae, D. magna was able to accumulate ROX in all three concentration treatments, but biomagnification did not occur at this trophic level, as biomagnification factors (BMFs) varied from 0.21 to 0.29 in different concentration treatments were well below one. In tissues (muscle, gill, liver, and bile) of C. auratus fed with contaminated daphnia for 8 days, no biomagnification was observed. However, this species did accumulate a certain degree of ROX through food chain transfer, and the tissue burden was greatest in the liver > muscle > gill and lowest in the bile. This work suggests that the trophic transfer should be a matter of concern for ecological risk assessments of pharmaceutical substances in aquatic food webs.

  11. The lithosphere-asthenosphere Italy and surroundings

    CERN Document Server

    Panza, G F; Chimera, G; Pontevivo, A; Raykova, R

    2003-01-01

    The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineat...

  12. The lithosphere-asthenosphere: Italy and surroundings

    International Nuclear Information System (INIS)

    Panza, G.F.; Aoudia, A.; Pontevivo, A.; Chimera, G.; Raykova, R.

    2003-02-01

    The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea, likely attesting the fragmentation of Adria. (author)

  13. Opportunity's Surroundings on Sol 1798 (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11850 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11850 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this stereo 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. This view combines images from the left-eye and right-eye sides of the navigation camera. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical-perspective projection with geometric seam correction.

  14. Opportunity's Surroundings After Sol 1820 Drive (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11841 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11841 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). This view combines images from the left-eye and right-eye sides of the navigation camera. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock. This view is presented as a cylindrical-perspective projection with geometric seam correction.

  15. Opportunity's Surroundings on Sol 1818 (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11846 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11846 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. This view combines images from the left-eye and right-eye sides of the navigation camera. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical-perspective projection with geometric seam correction.

  16. 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

  17. Sound Environments Surrounding Preterm Infants Within an Occupied Closed Incubator.

    Science.gov (United States)

    Shimizu, Aya; Matsuo, Hiroya

    2016-01-01

    Preterm infants often exhibit functional disorders due to the stressful environment in the neonatal intensive care unit (NICU). The sound pressure level (SPL) in the NICU is often much higher than the levels recommended by the American Academy of Pediatrics. Our study aims to describe the SPL and sound frequency levels surrounding preterm infants within closed incubators that utilize high frequency oscillation (HFO) or nasal directional positive airway pressure (nasal-DPAP) respiratory settings. This is a descriptive research study of eight preterm infants (corrected ageincubator. The actual noise levels were observed and the results were compared to the recommendations made by neonatal experts. Increased noise levels, which have reported to affect neonates' ability to self-regulate, could increase the risk of developing attention deficit disorder, and may result in tachycardia, bradycardia, increased intracranial pressure, and hypoxia. The care provider should closely assess for adverse effects of higher sound levels generated by different modes of respiratory support and take measures to ensure that preterm infants are protected from exposure to noise exceeding the optimal safe levels. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Trophic cascades: linking ungulates to shrub-dependent birds and butterflies.

    Science.gov (United States)

    J Teichman, Kristine; Nielsen, Scott E; Roland, Jens

    2013-11-01

    1. Studies demonstrating trophic cascades through the loss of top-down regulatory processes in productive and biologically diverse terrestrial ecosystems are limited. 2. Elk Island National Park, Alberta and surrounding protected areas have a wide range of ungulate density due to the functional loss of top predators, management for high ungulate numbers and variable hunting pressure. This provides an ideal setting for studying the effects of hyper-abundant ungulates on vegetation and shrub-dependent bird and butterfly species. 3. To examine the cascading effects of high ungulate density, we quantified vegetation characteristics and abundances of yellow warbler Dendroica petechia and Canadian tiger swallowtail Papilio canadensis under different ungulate density in and around Elk Island National Park. 4. Using Structural Equation Models we found that ungulate density was inversely related to shrub cover, whereas shrub cover was positively related to yellow warbler abundance. In addition, chokecherry Prunus virginiana abundance was inversely related to browse impact but positively related to P. canadensis abundance. 5. These results demonstrate a cascade resulting from hyper-abundant ungulates on yellow warblers and Canadian tiger swallowtails through reductions in shrub cover and larval host plant density. The combined effect of the functional loss of top predators and management strategies that maintain high ungulate numbers can decouple top-down regulation of productive temperate ecosystems. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

  19. Ecotopes, natural infection and trophic resources of Triatoma brasiliensis (Hemiptera, Reduviidae, Triatominae).

    Science.gov (United States)

    Costa, J; de Almeida, J R; Britto, C; Duarte, R; Marchon-Silva, V; Pacheco, R da S

    1998-01-01

    Triatoma brasiliensis is considered as one of the most important Chagas disease vectors in the northeastern Brazil. This species presents chromatic variations which led to descriptions of subspecies, synonymized by Lent and Wygodzinsky (1979). In order to broaden bionomic knowledge of these distinct colour patterns of T. brasiliensis, captures were performed at different sites, where the chromatic patterns were described: Caicó, Rio Grande do Norte (T. brasiliensis brasiliensis Neiva, 1911), it will be called the "brasiliensis population"; Espinosa, Minas Gerais (T. brasiliensis melanica Neiva & Lent 1941), the "melanica population" and Petrolina, Pernambuco (T. brasiliensis macromelasoma, Galvão 1956), the "macromelasoma population". A fourth chromatic pattern was collected in Juazeiro, Bahia the darker one in overall cuticle coloration, the "Juazeiro population". At the sites of Caicó, Petrolina and Juazeiro, specimens were captured in peridomiciliar ecotopes and in wilderness. In Espinosa the specimens were collected only in wilderness, even though several exhaustive captures have been performed in peridomicile at different sites of this municipality. A total of 298 specimens were captured. The average registered infection rate was 15% for "brasiliensis population" and of 6.6% for "melanica population". Specimens of "macromelasoma" and of "Juazeiro populations" did not present natural infection. Concerning trophic resources, evaluated by the precipitin test, feeding eclecticism for the different colour patterns studied was observed, with dominance of goat blood in household surroundings as well as in wilderness.

  20. Ecotopes, Natural Infection and Trophic Resources of Triatoma brasiliensis (Hemiptera, Reduviidae, Triatominae

    Directory of Open Access Journals (Sweden)

    Jane Costa

    1998-01-01

    Full Text Available Triatoma brasiliensis is considered as one of the most important Chagas disease vectors in the northeastern Brazil. This species presents chromatic variations which led to descriptions of subspecies, synonymized by Lent and Wygodzinsky (1979. In order to broaden bionomic knowledge of these distinct colour patterns of T. brasiliensis, captures were performed at different sites, where the chromatic patterns were described: Caicó, Rio Grande do Norte (T. brasiliensis brasiliensis Neiva, 1911, it will be called the "brasiliensis population"; Espinosa, Minas Gerais (T. brasiliensis melanica Neiva & Lent 1941, the "melanica population" and Petrolina, Pernambuco (T. brasiliensis macromelasoma, Galvão 1956, the "macromelasoma population". A fourth chromatic pattern was collected in Juazeiro, Bahia the darker one in overall cuticle coloration, the "Juazeiro population". At the sites of Caicó, Petrolina and Juazeiro, specimens were captured in peridomiciliar ecotopes and in wilderness. In Espinosa the specimens were collected only in wilderness, even though several exhaustive captures have been performed in peridomicile at different sites of this municipality. A total of 298 specimens were captured. The average registered infection rate was 15% for "brasiliensis population" and of 6.6% for "melanica population". Specimens of "macromelasoma" and of "Juazeiro populations" did not present natural infection. Concerning trophic resources, evaluated by the precipitin test, feeding eclecticism for the different colour patterns studied was observed, with dominance of goat blood in household surroundings as well as in wilderness

  1. Seasonality in contaminant accumulation in Arctic marine pelagic food webs using trophic magnification factor as a measure of bioaccumulation.

    Science.gov (United States)

    Hallanger, Ingeborg G; Warner, Nicholas A; Ruus, Anders; Evenset, Anita; Christensen, Guttorm; Herzke, Dorte; Gabrielsen, Geir W; Borgå, Katrine

    2011-05-01

    Seasonality in biomagnification of persistent organic pollutants (POPs; polychlorinated biphenyls, chlorinated pesticides, and brominated flame retardants) in Arctic marine pelagic food webs was investigated in Kongsfjorden, Svalbard, Norway. Trophic magnification factors (TMFs; average factor change in concentration between two trophic levels) were used to measure food web biomagnification in biota in May, July, and October 2007. Pelagic zooplankton (seven species), fish (five species), and seabirds (two species) were included in the study. For most POP compounds, highest TMFs were found in July and lowest were in May. Seasonally changing TMFs were a result of seasonally changing POP concentrations and the δ¹⁵N-derived trophic positions of the species included in the food web. These seasonal differences in TMFs were independent of inclusion/exclusion of organisms based on physiology (i.e., warm- versus cold-blooded organisms) in the food web. The higher TMFs in July, when the food web consisted of a higher degree of boreal species, suggest that future warming of the Arctic and increased invasion by boreal species can result in increased food web magnification. Knowledge of the seasonal variation in POP biomagnification is a prerequisite for understanding changes in POP biomagnification caused by climate change. Copyright © 2011 SETAC.

  2. The trophic position of the alien crab Rhithropanopeus harrisii (crustacea decapoda panopeidae) in the Taman Bay, Sea of Azov community

    Science.gov (United States)

    Zalota, A. K.; Kolyuchkina, G. A.; Tiunov, A. V.; Biriukova, S. V.; Spiridonov, V. A.

    2017-03-01

    This work concerns the trophic web positioning of the alien crab Rhithropanopeus harrisii and other common marine invertebrate species and fishes in the benthic ecosystem of the shallows of Taman Bay, Sea of Azov. The base of the trophic web in this system is composed of phytoplankton, macrophytes (algae and marine grasses), and reeds that use atmospheric carbon for photosynthesis. Analysis of the isotopic composition of nitrogen and carbon has shown that although marine grasses are dominating primary producers in the shallows of the bay, primary consumers (such as Cerastoderma glaucum, Porifera gen. sp., Gammarus aequicauda, Deshayesorchestia deshayesii and Idotea balthica) only partially use this organic source; instead, they use a combination of different sources of primary production. It has been shown that the food source of the alien crab is primarily of animal origin. In Taman Bay, R. harrisii is on the same trophic level as other carnivores/scavengers: benthic fishes Syngnathus nigrolineatus, Gobius spp. and native crab Pilumnus hirtellus and shrimp Palaemon adspersus.

  3. Aquatic bioaccumulation and trophic transfer of tetrabromobisphenol-A flame retardant introduced from a typical e-waste recycling site.

    Science.gov (United States)

    Tao, Lin; Wu, Jiang-Ping; Zhi, Hui; Zhang, Ying; Ren, Zi-He; Luo, Xiao-Jun; Mai, Bi-Xian

    2016-07-01

    While the flame retardant chemical, tetrabromobisphenol-A (TBBP-A), has been frequently detected in the environment, knowledge regarding its species-specific bioaccumulation and trophic transfer is limited, especially in the highly contaminated sites. In this study, the components of an aquatic food web, including two invertebrates, two prey fish, and one predator fish, collected from a natural pond at an electronic waste (e-waste) recycling site in South China were analyzed for TBBP-A, using liquid chromatography-tandem mass spectrometry. The aquatic species had TBBP-A concentrations ranging from 350 to 1970 pg/g wet weight, with higher concentrations in the invertebrates relative to the fish species. Field-determined bioaccumulation factors of TBBP-A in the two aquatic invertebrates were nearly or greater than 5000, suggesting that TBBP-A is highly bioaccumulative in the two species. The lipid-normalized concentrations of TBBP-A in the aquatic species were negatively correlated with the trophic levels determined from stable nitrogen isotope (δ(15)N) (r = -0.82, p = 0.09), indicating that this compound experienced trophic dilution in the current food web.

  4. Investigating the Trophic Ecology of the Fish Genus Cyclothone in the North Pacific Subtropical Gyre Using Stable Isotope Techniques

    Science.gov (United States)

    Gloeckler, K.; Ko, W.; Choy, C. A.; Hannides, C. C.; Close, H. G.; Popp, B. N.; Drazen, J.

    2016-02-01

    The meso- and bathypelagic fish genus Cyclothone, commonly known as bristlemouths, are the most abundant vertebrates on the planet. Despite their abundance, little is known about their trophic ecology. A few studies have used traditional stomach content analysis and found that the majority of individuals had empty stomachs and a few contained copepod and ostracod remains. We used bulk tissue carbon and nitrogen isotopes, and compound-specific nitrogen isotope analysis of amino acids (AA-CSIA) to investigate the trophic ecology of this genus from individuals collected at Station ALOHA, in the North Pacific Subtropical Gyre. Two cosmopolitan species were abundant, the shallower living Cyclothone alba (425-625 m) and the deeper living Cyclothone pallida (600 - 1300 m), and appear to have different feeding ecologies. While the bulk 13C and 15N contents of C. alba were similar to those of other zooplanktivorous micronekton, the bulk 13C and 15N contents of C. pallida were much higher than those of zooplanktivorous micronekton and suggest either (1) that they feed at a similar trophic level to large predatory fishes such as Thunnus albacares and Coryphaena hipurrus or (2) that the baseline isotopic values of their food web are substantially different. AA-CSIA showed that the trophic position (TP) of C. pallida was 2.3 - 3.2 (±0.28), that is, much lower than the TP of large predatory fishes. Additionally, the δ15N values of the `source' amino acid phenylalanine (d15NPHE) were very high, indicating baseline isotopic values within the range of bacterially-altered suspended particles. Suspended particles have often been overlooked as a significant source of carbon in the deep sea despite discrepancies between the supply of carbon via sinking particles and estimated demand of carbon by deep sea organisms. These results suggest that a suspended particle based food web is important to at least some deep-sea fauna.

  5. Trophic modeling of Eastern Boundary Current Systems: a review and prospectus for solving the “Peruvian Puzzle”

    Directory of Open Access Journals (Sweden)

    Marc H. Taylor

    2013-04-01

    Full Text Available Eastern Boundary Current systems (EBCSs are among the most productive fishing areas in the world. High primary and secondary productivity supports a large biomass of small planktivorous pelagic fish, “small pelagics”, which are important drivers of production to the entire system whereby they can influence both higher and lower trophic levels. Environmental variability causes changes in plankton (food quality and quantity, which can affect population sizes, distribution and domi-nance among small pelagics. This variability combined with impacts from the fishery complicate the development of management strategies. Consequently, much recent work has been in the development of multispecies trophic models to better understand interdependencies and system dynamics. Despite similarities in extent, structure and primary productivity between EBCSs, the Peruvian system greatly differs from the others in the magnitude of fish catches, due mainly to the incredible production of the anchovy Engraulis ringens. This paper reviews literature concerning EBCSs dynamics and the state-of-the-art in the trophic modeling of EBCSs. The objective is to critically analyze the potential of this approach for system understanding and management and to adapt existing steady-state models of the Peruvian system for use in (future dynamic simulations. A guideline for the construction of trophodynamic models is presented taking into account the important trophic and environmental interactions. In consideration of the importance of small pelagics for the system dynamics, emphasis is placed on developing appropriate model compartmentalization and spatial delineation that facilitates dynamic simulations. Methods of model validation to historical changes are presented to support hypotheses concerning EBCS dynamics and as a critical step to the development of predictive models. Finally, the identification of direct model links to easily obtainable abiotic parameters is

  6. Rotifer trophic state indices as ecosystem indicators in brackish coastal waters

    OpenAIRE

    Agnieszka Gutkowska; Ewa Paturej; Ewa Kowalska

    2013-01-01

    Thanks to their short life cycles, rotifers react rapidly to changes in environmental conditions and so may be useful for biological monitoring. The objective of this paper was to investigate the applicability of rotifer trophic state indices as indicators of the trophic state of brackish waters, as exemplified by the Vistula Lagoon. Carried out in summer from 2007 to 2011, this study showed no significant correlation between the Lagoon's trophic state and the rotifer structure. This confirms...

  7. ASSESSMENT OF TROPHIC STATE OF RESERVOIRS IN SOUTHERN POLAND UNDER DIVERSIFIED HUMAN IMPACT

    OpenAIRE

    Henryk Kasza

    2017-01-01

    The aim of this study was to assess a trophic state of reservoirs in southern Poland under diversified human impact with different morphological, hydrological and river basin features. Three reservoirs were studied: Wapienica, Goczałkowice and Łąka. To estimate a trophic state of reservoir waters criteria based on measured total nitrogen, total phosphorous and chlorophyll a concentrations and limiting values of trophies differentiation as well as the Carlson trophic index (TSI) were used. Rel...

  8. Cholinergic enhancement reduces orientation-specific surround suppression but not visual crowding

    Directory of Open Access Journals (Sweden)

    Anna A. Kosovicheva

    2012-09-01

    Full Text Available Acetylcholine (ACh reduces the spatial spread of excitatory fMRI responses in early visual cortex and the receptive field sizes of V1 neurons. We investigated the perceptual consequences of these physiological effects of ACh with surround suppression and crowding, two tasks that involve spatial interactions between visual field locations. Surround suppression refers to the reduction in perceived stimulus contrast by a high-contrast surround stimulus. For grating stimuli, surround suppression is selective for the relative orientations of the center and surround, suggesting that it results from inhibitory interactions in early visual cortex. Crowding refers to impaired identification of a peripheral stimulus in the presence of flankers and is thought to result from excessive integration of visual features. We increased synaptic ACh levels by administering the cholinesterase inhibitor donepezil to healthy human subjects in a placebo-controlled, double-blind design. In Exp. 1, we measured surround suppression of a central grating using a contrast discrimination task with three conditions: 1 surround grating with the same orientation as the center (parallel, 2 surround orthogonal to the center, or 3 no surround. Contrast discrimination thresholds were higher in the parallel than in the orthogonal condition, demonstrating orientation-specific surround suppression (OSSS. Cholinergic enhancement reduced thresholds only in the parallel condition, thereby reducing OSSS. In Exp. 2, subjects performed a crowding task in which they reported the identity of a peripheral letter flanked by letters on either side. We measured the critical spacing between the target and flanking letters that allowed reliable identification. Cholinergic enhancement had no effect on critical spacing. Our findings suggest that ACh reduces spatial interactions in tasks involving segmentation of visual field locations but that these effects may be limited to early visual cortical

  9. Trophic analysis of three species of Marilia (Trichoptera: Odontoceridae) from the neotropics.

    Science.gov (United States)

    Reynaga, María Celina; Rueda Martín, Paola Alejandra

    2014-06-01

    The trophic ecology of the aquatic insect fauna has been widely studied for the Northern temperate zone. However, the taxa originally classified within a given particular trophic group in temperate ecosystems, do not necessarily exhibit the same dietary profile beyond its geographic limits. Since, the trophic ecology of caddisfly larvae is largely incomplete in the Neotropical Region, the present work aims to describe feeding habits inferred from quantitative analysis of data taxonomically resolved at the species level. For this, the feeding habits of three Trichoptera species Marilia cinerea, M. elongata and M. flexuosa were recorded in the Yungas forests of Argentina and Bolivia. A total of 15 larvae of each species were sampled from 13 different streams were selected for gut content analysis. The ingested material was extracted from the foregut and midgut by using ventral dissection of thorax. For each species, mandibles were dissected, mounted in glycerin and illustrated in order to highlight morphological differences between these mouth pieces purportedly associated to the dietary behavior of individuals, and their habitats. The niche overlap was estimated through Schoener's method. The diet analysis revealed that M. cinerea, M. elongata and M. flexuosa feed on the same food items, but through different patterns of preferences. Larvae of M. cinerea were collected on both emerging surfaces of rocks on which a thin layer of running water flows and streams sliding areas with stony bottoms attached to the rock surfaces. They displayed a gut content consisting predominantly of invertebrate vestiges and have strong mouthparts provided of large molar areas; this allowed us to allocate the species within the functional group of predators. M. elongata feeds mainly on fine particulate material, its mouthparts are scoop-shaped and occurs in areas of low flow; this set of features is linked to a collector-gatherer strategy. Finally, larvae of M. flexuosa have been

  10. Rotifer trophic state indices as ecosystem indicators in brackish coastal waters

    Directory of Open Access Journals (Sweden)

    Agnieszka Gutkowska

    2013-11-01

    Full Text Available Thanks to their short life cycles, rotifers react rapidly to changes in environmental conditions and so may be useful for biological monitoring. The objective of this paper was to investigate the applicability of rotifer trophic state indices as indicators of the trophic state of brackish waters, as exemplified by the Vistula Lagoon. Carried out in summer from 2007 to 2011, this study showed no significant correlation between the Lagoon's trophic state and the rotifer structure. This confirms the limited applicability of rotifer trophic state indices for evaluating water quality in brackish water bodies.

  11. 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.

  12. Comparison of Socioeconomic Factors between Surrounding and Non-Surrounding Areas of the Qinghai–Tibet Railway before and after Its Construction

    Directory of Open Access Journals (Sweden)

    Shicheng Li

    2016-08-01

    Full Text Available As the world’s highest railway, and the longest highland railway, the Qinghai–Tibet Railway (QTR has been paid considerable attention by researchers. However, most attention has been paid to the ecological and environmental issues affecting it, and sustainable ecological, social, and economic development-related studies of the QTR are rare. In this study, by analyzing the passenger traffic, freight traffic, passenger-kilometers, and freight-kilometers of the QTR for the period 1982–2013 and the transport structure of the Tibetan Plateau (TP for 1990–2013, the evolutionary process of the transport system in the TP following the construction of the QTR has been revealed. Subsequently, by comparing Gross Domestic Product (GDP, population, industrial structure, and urbanization level at the county and 1 km scales between surrounding and non-surrounding areas of the QTR, the differences in socioeconomic performance before and after its construction were detected. The results show that (1 in the TP, the highway-dominated transport system will break up and an integrated and sustainable transport system will form; (2 at the county scale, the annual growth rates of GDP of counties surrounding the QTR were greater than those of non-surrounding counties for the period 2000–2010. At the 1 km scale, following the opening of the completed line, the GDP of surrounding areas had a greater growth rate than before; (3 analysis at the county and 1 km scales indicated that population was not aggregated into the surrounding areas of the QTR in the period 2000–2010; (4 in terms of industrial structure, the proportion of primary industry decreased continuously, while the proportion of secondary and tertiary industries increased overall in the period 1984–2012. The QTR had no obvious impact on changes in the urbanization level of its surrounding areas.

  13. Variability of Lekanesphaera monodi metabolic rates with habitat trophic status

    Science.gov (United States)

    Vignes, Fabio; Fedele, Marialaura; Pinna, Maurizio; Mancinelli, Giorgio; Basset, Alberto

    2012-05-01

    Regulation of metabolism is a common strategy used by individuals to respond to a changing environment. The mechanisms underlying the variability of metabolic rates in macroinvertebrates are of primary importance in studying benthic-pelagic energy transfer in transitional water ecosystems. Lekanesphaera monodi is an isopod endemic to transitional water ecosystems that can modify its metabolic rate in response to environmental changes. Therefore it is a useful model in studying the influence of environmental factors on metabolism. This study focused on the interpopulation variability of standard metabolic rates (SMR) in L. monodi populations sampled in three transitional water ecosystems differing in their trophic status. The standard metabolic rates of L. monodi individuals across the same range of body size spectra were inferred from oxygen consumption measurements in a flow-through respirometer in the three populations and a body condition index was assessed for each population. Habitat trophic status was evaluated by monthly measurement of the basic physical-chemical parameters of the water column in the ecosystems for one year. Standard metabolic rates showed high variability, ranging from 0.27 to 10.14 J d-1. Body size accounted for more than 38% of total variability. In terms of trophic status, individuals from the eutrophic ecosystem had significantly higher standard metabolic rates than individuals from the other ecosystems (SMR = 2.3 J d-1 in Spunderati Sud vs. 1.36 J d-1 in Alimini and 0.69 J d-1 in Acquatina). The body conditions index was also higher in the population from the eutrophic ecosystem. Results show that standard metabolic rates and growth rates are directly related to habitat productivity in accordance with the expectations of the food habits hypothesis. A possible extension of this hypothesis to benthic invertebrates is proposed.

  14. Diet and trophic niche of Lithobates catesbeianus (Amphibia: Anura

    Directory of Open Access Journals (Sweden)

    Peterson T. Leivas

    2012-10-01

    Full Text Available Lithobates catesbeianus (Shaw, 1802 is an invasive anuran introduced in Brazil that is associated with the displacement and the decline of populations of native species worldwide. There is evidence that biological invasions are facilitated by certain attributes of the invading species, for instance niche breath, and that invasive species have a broader ecological niche with respect to native ones. We designed a study to ascertain the temporal, ontogenetic, and sex differences in the niche dynamics of the American bullfrog. We sampled monthly from June 2008 to May 2009 in the state of Paraná, southern Brazil. For each individual, we gathered biometric and stomach content data. We then estimated the niche breath of the juveniles and adults, and compared it between the sexes. A total of 104 females and 77 males were sampled. Lithobates catesbeianus has a generalist diet, preying upon invertebrates and vertebrates. Even though the diet of the studied population varied seasonally, it did not differ between the sexes nor did it respond to biometric variables. Niche breadth was more restricted in the winter than in the autumn. The trophic niche of juveniles and adults did not overlap much when compared with the trophic niche overlap between males and females. Adult males and females had a considerable niche overlap, but females had a broader trophic niche than males in the winter and in the spring. These niche characteristics point to an opportunistic predation strategy that may have facilitated the process of invasion and establishment of this species in the study area.

  15. 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...

  16. Language barriers surrounding medication use among older Latinos.

    Science.gov (United States)

    Mutchler, Jan E; Bacigalupe, Gonzalo; Coppin, Antonia; Gottlieb, Alison

    2007-03-01

    Limited English language proficiency forms a significant challenge for many Latinos in clinical settings. Although medications are commonly used by older individuals as a means of maintaining good health and managing health problems, the extent to which English proficiency is related to medication use among older Latinos is not known. Focus groups were conducted with Latino, community-residing individuals aged 50 and over in eastern Massachusetts. Qualitative evaluation of the group interviews suggests that language is a barrier in dealing with medication for these individuals. Limited English proficiency appears to be related to feelings of being discriminated against in clinical and pharmacy settings. As well, communicating directly with health professionals in a common language is associated with level of trust and confidence in medical settings. Use of formal and informal interpreters, as well as seeking Spanish-speaking physicians and pharmacies with Spanish-speaking staff, are identified as strategies for overcoming health-related obstacles surrounding language.

  17. Anticipation and Controversy Surround "Superman" Release

    Science.gov (United States)

    Aarons, Dakarai I.

    2010-01-01

    Well in advance of its official release, the education film "Waiting For Superman" has attracted a level of attention that could make it one of the year's most-watched documentaries--and one of the most controversial among educators, some of whom question its depictions of the American school system and how to improve it. Made by…

  18. 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.

  19. Assessment, modelization and analysis of 106 Ru experimental transfers through a freshwater trophic system

    International Nuclear Information System (INIS)

    Vray, F.

    1994-01-01

    Experiments are carried out in order to study 106 RU transfers through a freshwater ecosystem including 2 abiotic compartments (water and sediment) and 3 trophic levels (10 species). Experimental results are expressed mathematically so as they can be included into a global model which is then tested in two different situations. The comparison of the available data concerning the in situ measured concentrations to the corresponding calculated ones validates the whole procedure. Analysis of the so validated results lightens ruthenium distribution process in the environment. The rare detection of this radionuclide in organisms living in areas contaminated by known meaningful releases can be explained by a relativity high detection limit and by a slight role of the sediment as a secondary contamination source. (author). 78 figs., 18 tabs

  20. Bioaccumulation and trophic transfer of dioxins in marine copepods and fish.

    Science.gov (United States)

    Zhang, Qiong; Yang, Liuyan; Wang, Wen-Xiong

    2011-12-01

    Despite the great concerns about dioxins in the marine environments, the biokinetics and bioaccumulation of these compounds in marine organisms remains little known. Using radioactive tracers the aqueous uptake, dietary assimilation efficiency, and elimination of dioxins were measured in marine phytoplankton, copepods and seabream. The calculated uptake rate constant of dioxins decreased with increasing trophic levels, whereas the dietary assimilation efficiency (AE) was 28.5-57.6% in the copepods and 36.6-70.2% in the fish. The dietary AE was highly dependent on the food concentrations and food type. The elimination rate constant of dioxin in the copepods varied with different exposure pathways as well as food concentration and food type. Biokinetic calculation showed that dietary accumulation was the predominant pathway for dioxin accumulation in marine copepods and fish. Aqueous uptake can be an important pathway only when the bioconcentration of dioxins in the phytoplankton was low. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Trophic Interactions in the Baltic Sea: Predation on cod eggs by clupeids

    DEFF Research Database (Denmark)

    Neumann, Viola

    sprat and herring in terms of major taxonomic groups was generally similar in the 1990s and 2000s. Although higher proportions of cod eggs occurred in the diet in the 2000s, the overall quantities of cod eggs in the diet were generally lower in the 2000s compared to the 1990s (Paper I). This suggests......Cod (Gadus morhua), sprat (Sprattus sprattus) and herring (Clupea harengus) are key species of the upper trophic levels in the Baltic Sea ecosystem and are strongly interlinked: The piscivore cod is the main predator on the planktivores sprat and herring, which feed, amongst others, on cod eggs....... Egg predation by sprat and herring has earlier been suggested as one of the factors limiting cod recruitment success in the Baltic Sea in the 1990s. Since then, changes have taken place in cod recruitment as well as in the ecological factors potentially influencing egg predation. The overall aim...

  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. Centre-Surround Interactions in the Aging System: Effects of Centre-Surround Contrast and Stimulus Duration

    Directory of Open Access Journals (Sweden)

    Allison McKendrick

    2012-10-01

    Full Text Available The perceived contrast of a sinusoidal grating patch depends on its surrounding contrast. Normal aging alters these types of contrast related contextual effects, with older adults showing increased surround suppression relative to younger adults (Karas and McKendrick, 2009 Journal of Vision 9.5.11. This study aimed to determine whether age related increases in surround suppression manifest for particular contrast conditions, or specific contrast ratios between centre and surround. We also varied stimulus duration to determine whether group differences could arise due to between-group differences in surround adaptation. Fifteen younger (20–30 years and 15 older adults (65–79 years participated. Center-surround contrast discrimination (the Chubb contrast illusion was measured for a 0.67 deg diameter circular patch of 4 c/deg grating, surrounded by a 4 deg diameter annulus of grating of the same orientation, phase, and spatial frequency. Nine contrast conditions were tested (all combinations of centre/surround for stimuli of 20, 40, and 80% contrast with a stimulus duration of 500 ms. The 40% centre, 80% contrast surround was also tested with a stimulus duration of 100 ms. Surround suppression was increased in the older group [F(1,28 = 6.88, p = .01], particularly for low centre contrasts (interaction between group and centre contrast, p = .01. Increased surround suppression was present for both 500 ms and 100 ms presentations [main effect of group F(1,26 = 10.78, p= .01].

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

    Science.gov (United States)

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

    2018-03-01

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

  5. Global change in the trophic functioning of marine food webs.

    Directory of Open Access Journals (Sweden)

    Aurore Maureaud

    Full Text Available The development of fisheries in the oceans, and other human drivers such as climate warming, have led to changes in species abundance, assemblages, trophic interactions, and ultimately in the functioning of marine food webs. Here, using a trophodynamic approach and global databases of catches and life history traits of marine species, we tested the hypothesis that anthropogenic ecological impacts may have led to changes in the global parameters defining the transfers of biomass within the food web. First, we developed two indicators to assess such changes: the Time Cumulated Indicator (TCI measuring the residence time of biomass within the food web, and the Efficiency Cumulated Indicator (ECI quantifying the fraction of secondary production reaching the top of the trophic chain. Then, we assessed, at the large marine ecosystem scale, the worldwide change of these two indicators over the 1950-2010 time-periods. Global trends were identified and cluster analyses were used to characterize the variability of trends between ecosystems. Results showed that the most common pattern over the study period is a global decrease in TCI, while the ECI indicator tends to increase. Thus, changes in species assemblages would induce faster and apparently more efficient biomass transfers in marine food webs. Results also suggested that the main driver of change over that period had been the large increase in fishing pressure. The largest changes occurred in ecosystems where 'fishing down the marine food web' are most intensive.

  6. [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.

  7. Trophic specialization drives morphological evolution in sea snakes.

    Science.gov (United States)

    Sherratt, Emma; Rasmussen, Arne R; Sanders, Kate L

    2018-03-01

    Viviparous sea snakes are the most rapidly speciating reptiles known, yet the ecological factors underlying this radiation are poorly understood. Here, we reconstructed dated trees for 75% of sea snake species and quantified body shape (forebody relative to hindbody girth), maximum body length and trophic diversity to examine how dietary specialization has influenced morphological diversification in this rapid radiation. We show that sea snake body shape and size are strongly correlated with the proportion of burrowing prey in the diet. Specialist predators of burrowing eels have convergently evolved a 'microcephalic' morphotype with dramatically reduced forebody relative to hindbody girth and intermediate body length. By comparison, snakes that predominantly feed on burrowing gobies are generally short-bodied and small-headed, but there is no evidence of convergent evolution. The eel specialists also exhibit faster rates of size and shape evolution compared to all other sea snakes, including those that feed on gobies. Our results suggest that trophic specialization to particular burrowing prey (eels) has invoked strong selective pressures that manifest as predictable and rapid morphological changes. Further studies are needed to examine the genetic and developmental mechanisms underlying these dramatic morphological changes and assess their role in sea snake speciation.

  8. Bioenergetics, Trophic Ecology, and Niche Separation of Tunas.

    Science.gov (United States)

    Olson, R J; Young, J W; Ménard, F; Potier, M; Allain, V; Goñi, N; Logan, J M; Galván-Magaña, F

    Tunas are highly specialized predators that have evolved numerous adaptations for a lifestyle that requires large amounts of energy consumption. Here we review our understanding of the bioenergetics and feeding dynamics of tunas on a global scale, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas. Food consumption balances bioenergetics expenditures for respiration, growth (including gonad production), specific dynamic action, egestion, and excretion. Tunas feed across the micronekton and some large zooplankton. Some tunas appear to time their life history to take advantage of ephemeral aggregations of crustacean, fish, and molluscan prey. Ontogenetic and spatial diet differences are substantial, and significant interdecadal changes in prey composition have been observed. Diet shifts from larger to smaller prey taxa highlight ecosystem-wide changes in prey availability and diversity and provide implications for changing bioenergetics requirements into the future. Where tunas overlap, we show evidence of niche separation between them; resources are divided largely by differences in diet percentages and size ranges of prey taxa. The lack of long-term data limits the ability to predict impacts of climate change on tuna feeding behaviour. We note the need for systematic collection of feeding data as part of routine monitoring of these species, and we highlight the advantages of using biochemical techniques for broad-scale analyses of trophic relations. We support the continued development of ecosystem models, which all too often lack the regional-specific trophic data needed to adequately investigate climate and fishing impacts. © 2016 Elsevier Ltd. All rights reserved.

  9. Trophic relationships in an Arctic food web and implications for trace metal transfer

    International Nuclear Information System (INIS)

    Dehn, Larissa-A.; Follmann, Erich H.; Thomas, Dana L.; Sheffield, Gay G.; Rosa, Cheryl; Duffy, Lawrence K.; O'Hara, Todd M.

    2006-01-01

    Tissues of subsistence-harvested Arctic mammals were analyzed for silver (Ag), cadmium (Cd), and total mercury (THg). Muscle (or total body homogenates of potential fish and invertebrate prey) was analyzed for stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopes to establish trophic interactions within the Arctic food chain. Food web magnification factors (FWMFs) and biomagnification factors for selected predator-prey scenarios (BMFs) were calculated to describe pathways of heavy metals in the Alaskan Arctic. FWMFs in this study indicate that magnification of selected heavy metals in the Arctic food web is not significant. Biomagnification of Cd occurs mainly in kidneys; calculated BMFs are higher for hepatic THg than renal THg for all predator-prey scenarios with the exception of polar bears (Ursus maritimus). In bears, the accumulation of renal THg is approximately 6 times higher than in liver. Magnification of hepatic Ag is minimal for all selected predator-prey scenarios. Though polar bears occupy a higher trophic level than belugas (Delphinapterus leucas), based on δ 15 N, the metal concentrations are either not statistically different between the two species or lower for bears. Similarly, concentrations of renal and hepatic Cd are significantly lower or not statistically different in polar bears compared to ringed (Phoca hispida) and bearded seals (Erignathus barbatus), their primary prey. THg, on the other hand, increased significantly from seal to polar bear tissues. Mean δ 15 N was lowest in muscle of Arctic fox (Alopex lagopus) and foxes also show the lowest levels of Hg, Cd and Ag in liver and kidney compared to the other species analyzed. These values are in good agreement with a diet dominated by terrestrial prey. Metal deposition in animal tissues is strongly dependent on biological factors such as diet, age, sex, body condition and health, and caution should be taken when interpreting magnification of dynamic and actively regulated trace metals

  10. Trophic relationships in an Arctic food web and implications for trace metal transfer

    Energy Technology Data Exchange (ETDEWEB)

    Dehn, Larissa-A. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States)]. E-mail: ftld@uaf.edu; Follmann, Erich H. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States); Thomas, Dana L. [Department of Mathematical Sciences, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-6660 (United States); Sheffield, Gay G. [Alaska Department of Fish and Game, Fairbanks, Division of Wildlife Conservation, Fairbanks, Alaska, 99701-1599 (United States); Rosa, Cheryl [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States); Duffy, Lawrence K. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States); O' Hara, Todd M. [Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7000 (United States)

    2006-06-01

    Tissues of subsistence-harvested Arctic mammals were analyzed for silver (Ag), cadmium (Cd), and total mercury (THg). Muscle (or total body homogenates of potential fish and invertebrate prey) was analyzed for stable carbon ({delta} {sup 13}C) and nitrogen ({delta} {sup 15}N) isotopes to establish trophic interactions within the Arctic food chain. Food web magnification factors (FWMFs) and biomagnification factors for selected predator-prey scenarios (BMFs) were calculated to describe pathways of heavy metals in the Alaskan Arctic. FWMFs in this study indicate that magnification of selected heavy metals in the Arctic food web is not significant. Biomagnification of Cd occurs mainly in kidneys; calculated BMFs are higher for hepatic THg than renal THg for all predator-prey scenarios with the exception of polar bears (Ursus maritimus). In bears, the accumulation of renal THg is approximately 6 times higher than in liver. Magnification of hepatic Ag is minimal for all selected predator-prey scenarios. Though polar bears occupy a higher trophic level than belugas (Delphinapterus leucas), based on {delta} {sup 15}N, the metal concentrations are either not statistically different between the two species or lower for bears. Similarly, concentrations of renal and hepatic Cd are significantly lower or not statistically different in polar bears compared to ringed (Phoca hispida) and bearded seals (Erignathus barbatus), their primary prey. THg, on the other hand, increased significantly from seal to polar bear tissues. Mean {delta} {sup 15}N was lowest in muscle of Arctic fox (Alopex lagopus) and foxes also show the lowest levels of Hg, Cd and Ag in liver and kidney compared to the other species analyzed. These values are in good agreement with a diet dominated by terrestrial prey. Metal deposition in animal tissues is strongly dependent on biological factors such as diet, age, sex, body condition and health, and caution should be taken when interpreting magnification of

  11. 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