WorldWideScience

Sample records for interacting trophic levels

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

    NARCIS (Netherlands)

    Poelman, E.H.; Kos, M.

    2016-01-01

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

  2. 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

  3. 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.

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

    NARCIS (Netherlands)

    Kissling, W.D.; Schleuning, M.

    2015-01-01

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

  5. 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.

  6. Interactions between trophic levels in upwelling and non-upwelling regions during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Malik, A; Fernandes, C.E.G.; Gonsalves, M.J.B.D.; Subina, N.S.; Mamatha, S.S.; Krishna, K.S.; Varik, S.; RituKumari; Gauns, M.; Cejoice, R.P.; Pandey, S.S.; Jineesh, V.K.; Kamaleson, A; Vijayan, V.; Mukherjee, I.; Subramanyan, S.; Nair, S.; Ingole, B.S.; LokaBharathi, P.A

    Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May–September). We hypothesize that there could be a shift in environmental parameters along with changes in the network of interactions...

  7. 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.

  8. 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.

  9. 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

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

    Science.gov (United States)

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

    2017-10-01

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

  11. 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.

  12. 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

  13. 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...

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

    OpenAIRE

    Agurto, Cristian

    2007-01-01

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

  15. 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.

  16. 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

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

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  18. 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.

  19. 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.

  20. 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...

  1. 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.

  2. Trophic level responses differ as climate warms in Ireland

    Science.gov (United States)

    Donnelly, Alison; Yu, Rong; Liu, Lingling

    2015-08-01

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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

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

    Science.gov (United States)

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

    2010-05-01

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

  9. 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.

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

    Science.gov (United States)

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

    2011-05-01

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

  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. Comparison of contaminants from different trophic levels and ecosystems

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-01-17

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

  13. Thiacloprid affects trophic interaction between gammarids and mayflies

    International Nuclear Information System (INIS)

    Englert, D.; Bundschuh, M.; Schulz, R.

    2012-01-01

    Neonicotinoid insecticides like thiacloprid enter agricultural surface waters, where they may affect predator–prey-interactions, which are of central importance for ecosystems as well as the functions these systems provide. The effects of field relevant thiacloprid concentrations on the leaf consumption of Gammarus fossarum (Amphipoda) were assessed over 96 h (n = 13–17) in conjunction with its predation on Baetis rhodani (Ephemeroptera) nymphs. The predation by Gammarus increased significantly at 0.50–1.00 μg/L. Simultaneously, its leaf consumption decreased with increasing thiacloprid concentration. As a consequence of the increased predation at 1.00 μg/L, gammarids' dry weight rose significantly by 15% compared to the control. At 4.00 μg/L, the reduced leaf consumption was not compensated by an increase in predation causing a significantly reduced dry weight of Gammarus (∼20%). These results may finally suggest that thiacloprid adversely affects trophic interactions, potentially translating into alterations in ecosystem functions, like leaf litter breakdown and aquatic-terrestrial subsidies. - Highlights: ► Field relevant thiacloprid concentrations affected gammarid and mayfly interaction. ► Gammarus leaf consumption and predation success is adversely affected. ► Gammarus growth increased due to higher predation at 1.0 μg thiacloprid/L. ► The study's results are discussed in the context of ecosystem functions. - Field relevant thiacloprid concentrations affect species interactions, which may translate to alterations in ecosystem functions.

  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. 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

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

    Science.gov (United States)

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

    2015-01-01

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

  19. 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.

  20. Invasive plant architecture alters trophic interactions by changing predator abundance and behavior

    Science.gov (United States)

    Dean E. Pearson

    2009-01-01

    As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa...

  1. 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

  2. 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.

  3. 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

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

    Science.gov (United States)

    Pasotti, Francesca; Saravia, Leonardo Ariel; De Troch, Marleen; Tarantelli, Maria Soledad; Sahade, Ricardo; Vanreusel, Ann

    2015-01-01

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

  5. 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.

  6. 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.

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

    Science.gov (United States)

    Smith, Annabel L

    2018-01-01

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

  8. Feeding behavior and trophic interaction of three shark species in the Galapagos Marine Reserve

    Directory of Open Access Journals (Sweden)

    Diego Páez-Rosas

    2018-05-01

    Full Text Available There is great concern about the future of sharks in Ecuador because of the lack of biological knowledge of most species that inhabit the region. This paper analyzes the feeding behavior of the pelagic thresher shark (Alopias pelagicus, the blue shark (Prionace glauca and the silky shark (Carcharhinus falciformis through the use of stable isotopes of carbon and nitrogen (δ13C and δ15N, with the aim of determining the degree of interaction between these species in the Galapagos Marine Reserve. No interspecific differences were found in use of oceanic vs. inshore feeding areas (δ13C: Kruskal–Wallis test, p = 0.09. The position in the hierarchy of the food web where A. pelagicus feeds differed from that of the other species (δ15N: Kruskal–Wallis test, p = 0.01. There were no significant differences in δ13C and δ15N values between males and females of the three species (Student’s t-test, p > 0.05, which suggests that both sexes have a similar feeding behavior. A specialist strategy was observed in P. glauca (trophic niche breadth TNB = 0.69, while the other species were found to be generalist (A. pelagicus TNB = 1.50 and C. falciformis TNB = 1.09. The estimated trophic level (TL varied between the three species. C. falciformis occupied the highest trophic level (TL = 4.4, making it a quaternary predator in the region. The results of this study coincide with the identified behavior in these predators in other areas of the tropical Pacific (Colombia and Mexico, and suggest a pelagic foraging strategy with differential consumption of prey between the three species. These ecological aspects can provide timely information when implementing in conservation measures for these shark species in the Tropical Pacific and Galapagos Marine Reserve.

  9. Feeding behavior and trophic interaction of three shark species in the Galapagos Marine Reserve.

    Science.gov (United States)

    Páez-Rosas, Diego; Insuasti-Zarate, Paul; Riofrío-Lazo, Marjorie; Galván-Magaña, Felipe

    2018-01-01

    There is great concern about the future of sharks in Ecuador because of the lack of biological knowledge of most species that inhabit the region. This paper analyzes the feeding behavior of the pelagic thresher shark ( Alopias pelagicus ), the blue shark ( Prionace glauca ) and the silky shark ( Carcharhinus falciformis ) through the use of stable isotopes of carbon and nitrogen ( δ 13 C and δ 15 N), with the aim of determining the degree of interaction between these species in the Galapagos Marine Reserve. No interspecific differences were found in use of oceanic vs. inshore feeding areas ( δ 13 C: Kruskal-Wallis test, p = 0.09). The position in the hierarchy of the food web where A. pelagicus feeds differed from that of the other species ( δ 15 N: Kruskal-Wallis test, p = 0.01). There were no significant differences in δ 13 C and δ 15 N values between males and females of the three species (Student's t -test, p  > 0.05), which suggests that both sexes have a similar feeding behavior. A specialist strategy was observed in P. glauca (trophic niche breadth TNB = 0.69), while the other species were found to be generalist ( A. pelagicus TNB = 1.50 and C. falciformis TNB = 1.09). The estimated trophic level (TL) varied between the three species. C. falciformis occupied the highest trophic level (TL = 4.4), making it a quaternary predator in the region. The results of this study coincide with the identified behavior in these predators in other areas of the tropical Pacific (Colombia and Mexico), and suggest a pelagic foraging strategy with differential consumption of prey between the three species. These ecological aspects can provide timely information when implementing in conservation measures for these shark species in the Tropical Pacific and Galapagos Marine Reserve.

  10. 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.

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

    Science.gov (United States)

    Tucker, Marlee A.; Rogers, Tracey L.

    2014-01-01

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

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

    Science.gov (United States)

    Tucker, Marlee A; Rogers, Tracey L

    2014-12-22

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

  13. Predicting Trophic Interactions and Habitat Utilization in the California Current Ecosystem

    Science.gov (United States)

    2015-09-30

    Foraging patterns: model-data comparison . Simulated (colored circles) and observed (black circles) foraging locations for male sea lion individuals off...focusing on trophic interactions affecting habitat utilization and foraging patterns of California sea lions (CSL) in the California Current Large Marine...by considering patterns of covariability between environmental variables (e.g., temperature, primary production) and foraging patterns and success of

  14. 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.

  15. 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

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

    NARCIS (Netherlands)

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

    2007-01-01

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

  17. 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...

  18. 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.

  19. 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.

  20. NanoSIMS study of trophic interactions in the coral-dinoflagellate endosymbiosis

    Science.gov (United States)

    Kopp, Christophe; Mathieu, Pernice; Domart-Coulon, Isabelle; Djediat, Chakib; Spangenberg, Jorge; Alexander, Duncan; Hignette, Michel; Meziane, Tarik; Meibom, Anders

    2013-04-01

    Tropical and subtropical reef-building corals generally form a stable endosymbiotic association with autotrophic single-celled dinoflagellate algae, commonly known as "zooxanthellae", which is crucial for the development of coral reef ecosystems. In the present work, the spatial and temporal dynamics of trophic interactions between corals and their dinoflagellates was investigated in situ and at a subcellular level in the reef-building coral Pocillopora damicornis. Transmission electron microscopy (TEM) and quantitative NanoSIMS isotopic imaging of tissue ultra-thin sections (70 nm) were combined to precisely track the assimilation and the fate of 15N-labeled compounds (ammonium, nitrate and aspartic acid) within each symbiotic partner of the coral-dinoflagellate association. Among our main results, we found that (i) both dinoflagellate algae and coral tissue rapidly assimilate ammonium and aspartic acid from the environment, (ii) however only the dinoflagellates assimilate nitrate, (ii) nitrogen is rapidly and temporary stored within the dinoflagellate cells into uric acid crystals, and (iii) the dinoflagellate endosymbionts translocate nitrogenous compounds to their coral host. This study paves the way for exploring in details the wide range of metabolic interactions between partners of any symbiosis in the biosphere.

  1. 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.

  2. Reciprocal Trophic Interactions and Transmission of Blood Parasites between Mosquitoes and Frogs

    Directory of Open Access Journals (Sweden)

    Todd G. Smith

    2012-04-01

    Full Text Available The relationship between mosquitoes and their amphibian hosts is a unique, reciprocal trophic interaction. Instead of a one-way, predator-prey relationship, there is a cyclical dance of avoidance and attraction. This has prompted spatial and temporal synchrony between organisms, reflected in emergence time of mosquitoes in the spring and choice of habitat for oviposition. Frog-feeding mosquitoes also possess different sensory apparatuses than do their mammal-feeding counterparts. The reciprocal nature of this relationship is exploited by various blood parasites that use mechanical, salivary or trophic transmission to pass from mosquitoes to frogs. It is important to investigate the involvement of mosquitoes, frogs and parasites in this interaction in order to understand the consequences of anthropogenic actions, such as implementing biocontrol efforts against mosquitoes, and to determine potential causes of the global decline of amphibian species.

  3. Genetic variation in foundation species governs the dynamics of trophic interactions

    Science.gov (United States)

    Valencia-Cuevas, Leticia; Mussali-Galante, Patricia; Cano-Santana, Zenón; Pujade-Villar, Juli; Equihua-Martínez, Armando

    2018-01-01

    Abstract Various studies have demonstrated that the foundation species genetic diversity can have direct effects that extend beyond the individual or population level, affecting the dependent communities. Additionally, these effects may be indirectly extended to higher trophic levels throughout the entire community. Quercus castanea is an oak species with characteristics of foundation species beyond presenting a wide geographical distribution and being a dominant element of Mexican temperate forests. In this study, we analyzed the influence of population (He) and individual (HL) genetic diversity of Q. castanea on its canopy endophagous insect community and associated parasitoids. Specifically, we studied the composition, richness (S) and density of leaf-mining moths (Lepidoptera: Tischeridae, Citheraniidae), gall-forming wasps (Hymenoptera: Cynipidae), and canopy parasitoids of Q. castanea. We sampled 120 trees belonging to six populations (20/site) through the previously recognized gradient of genetic diversity. In total, 22 endophagous insect species belonging to three orders (Hymenoptera, Lepidoptera, and Diptera) and 20 parasitoid species belonging to 13 families were identified. In general, we observed that the individual genetic diversity of the host plant (HL) has a significant positive effect on the S and density of the canopy endophagous insect communities. In contrast, He has a significant negative effect on the S of endophagous insects. Additionally, indirect effects of HL were observed, affecting the S and density of parasitoid insects. Our results suggest that genetic variation in foundation species can be one of the most important factors governing the dynamics of tritrophic interactions that involve oaks, herbivores, and parasitoids. PMID:29492034

  4. The Ecology of Shallow Lakes - Trophic Interactions in the Pelagial

    DEFF Research Database (Denmark)

    Jeppesen, E.

    publications. The thesis was in June 1998 approved by The Faculty of Natural Sciences at the University of Copenhagen for defence for the doctor´s degree in Natural Sciences (D.sc). This thesis describes how biological interactions in the pelagial of lakes change across both nutrients and depth gradients......The defence took place on December 11, 1998 at The Freshwater Centre, Silkeborg, Denmark. Officiel opponents was Prof. Jürgen Benndorf, University of Technology, Dresden,Germany and Prof. Dag Hessen, University of Oslo, Norway . The defence was led by Lektor Leif Lau Jeppesen, Zoological Institute...

  5. 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

  6. Artificial light at night alters trophic interactions of intertidal invertebrates.

    Science.gov (United States)

    Underwood, Charlotte N; Davies, Thomas W; Queirós, Ana M

    2017-07-01

    balance of interspecific interactions involved in community structuring may be affected. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

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

    Science.gov (United States)

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

    2017-07-01

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

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

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  9. 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.

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

    Science.gov (United States)

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

    2009-01-01

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

  11. 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.

  12. 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

  13. Understanding trophic interactions of Orius spp. (Hemiptera: Anthocoridae) in lettuce crops by molecular methods.

    Science.gov (United States)

    Gomez-Polo, Priscila; Alomar, Oscar; Castañé, Cristina; Aznar-Fernández, Thaïs; Lundgren, Jonathan G; Piñol, Josep; Agustí, Nuria

    2016-02-01

    The aphid Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae) and the thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) are common pests in Mediterranean lettuce crops, where Orius spp. are common generalist predators. Predation by Orius spp. was studied in a lettuce plot by conventional polymerase chain reaction (PCR) and real-time PCR analyses using specific primers of both main pests. Also, high-throughput sequencing was used to have a wider approach of the diet of these predators in natural field conditions. Molecular analyses indicated a higher predation on N. ribisnigri in spring and on F. occidentalis in summer. Predation on alternative prey, like Collembola, was also found in both seasons. Real-time PCR was more sensitive than conventional PCR in showing the target trophic links, whereas high-throughput sequencing revealed predation on other natural enemies - intraguild predation (IGP), showing other trophic interactions of Orius majusculus within the studied ecosystem. This study gives important information about the trophic relationships present in Mediterranean lettuce crops in different periods of the year. The detected predation by Orius spp. on alternative prey, as well as on other natural enemies, should be further investigated to clarify whether it adds or detracts to the biological control of N. ribisnigri and F. occidentalis. © 2015 Society of Chemical Industry.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-10-01

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

  15. 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

  16. Trophic interactions among grouper (Epinephelus marginatus), octopus (Octopus vulgaris) and red lobster (Palinurus elephas) in the Western Mediterranean

    OpenAIRE

    Quetglas, A. (Antoni); Reñones, O. (Olga); Goñi, R. (Raquel)

    2001-01-01

    In the present paper a first evaluation of the trophic interactions between grouper, octopus and spiny red lobster in the western Mediterranean is presented. The efficiency of octopus preying on lobsters is also estimated from trap catches. Grouper and octopus base their diet on the same major taxonomic groups and this is reflected in the values of diet overlap. Trophic diversity of grouper and octopus is also very similar. The estimation of the octopus efficiency preying on lobsters shows th...

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

    Directory of Open Access Journals (Sweden)

    John Y Takekawa

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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

  20. 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.

  1. Cascading trophic interactions in the littoral zone: an enclosure experiment in shallow Lake Stigsholm, Denmark

    DEFF Research Database (Denmark)

    Jeppesen, E.; Søndergaard, M.; Søndergaard, M.

    2002-01-01

    The importance of grazer versus resource control has been extensively studied in the pelagic zone of lakes. In contrast, comparatively little is known about trophic interactions within the littoral zone. We conducted an experiment in the littoral zone of a eutrophic shallow lake using six 20 m2......, zooplankton grazing was equivalent to production in M+, but amounted to littoral zones do not alone feed on particles produced in the water, but also exploit alternative sources such as periphyton...... hypothesize that the strong cascading effects of zooplankton on chlorophyll-a and microorganisms in the littoral zone at natural fish densities are restricted to eutrophic lakes with high plant densities....

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

    International Nuclear Information System (INIS)

    Farrell, Paul; Nelson, Kathryn

    2013-01-01

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

  3. 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

  4. Microbial trophic interactions and mcrA gene expression in monitoring of anaerobic digesters

    Directory of Open Access Journals (Sweden)

    Alejandra eAlvarado

    2014-11-01

    Full Text Available Anaerobic digestion (AD is a biological process where different trophic groups of microorganisms break down biodegradable organic materials in the absence of oxygen. A wide range of anaerobic digestion technologies is being used to convert livestock manure, municipal and industrial wastewaters, and solid organic wastes into biogas. AD gains importance not only because of its relevance in waste treatment but also because of the recovery of carbon in the form of methane, which is a renewable energy and is used to generate electricity and heat. Despite the advances on the engineering and design of new bioreactors for anaerobic digestion, the microbiology component always poses challenges. Microbiology of AD processes is complicated as the efficiency of the process depends on the interactions of various trophic groups involved. Due to the complex interdependence of microbial activities for the functionality of the anaerobic bioreactors, the genetic expression of mcrA, which encodes a key enzyme in methane formation, is proposed as a parameter to monitor the process performance in real time. This review evaluates the current knowledge on microbial groups, their interactions and their relationship to the performance of anaerobic biodigesters with a focus on using mcrA gene expression as a tool to monitor the process.

  5. Microbial trophic interactions and mcrA gene expression in monitoring of anaerobic digesters

    Science.gov (United States)

    Alvarado, Alejandra; Montañez-Hernández, Lilia E.; Palacio-Molina, Sandra L.; Oropeza-Navarro, Ricardo; Luévanos-Escareño, Miriam P.; Balagurusamy, Nagamani

    2014-01-01

    Anaerobic digestion (AD) is a biological process where different trophic groups of microorganisms break down biodegradable organic materials in the absence of oxygen. A wide range of AD technologies is being used to convert livestock manure, municipal and industrial wastewaters, and solid organic wastes into biogas. AD gains importance not only because of its relevance in waste treatment but also because of the recovery of carbon in the form of methane, which is a renewable energy and is used to generate electricity and heat. Despite the advances on the engineering and design of new bioreactors for AD, the microbiology component always poses challenges. Microbiology of AD processes is complicated as the efficiency of the process depends on the interactions of various trophic groups involved. Due to the complex interdependence of microbial activities for the functionality of the anaerobic bioreactors, the genetic expression of mcrA, which encodes a key enzyme in methane formation, is proposed as a parameter to monitor the process performance in real time. This review evaluates the current knowledge on microbial groups, their interactions, and their relationship to the performance of anaerobic biodigesters with a focus on using mcrA gene expression as a tool to monitor the process. PMID:25429286

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

    DEFF Research Database (Denmark)

    Jacobsen, Stine Kramer

    The two spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a major cause of pest damage worldwide. Its host range includes among many the strawberry crop, a high value crop in Denmark as well as in many other temperate and subtropical regions. Chemical control of T. urticae...... 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...... between natural enemies, in particular generalist predators and the two spotted spider mite, T. urticae, in strawberry. This was done by investigating interactions of T. urticae and its natural enemies as influenced by cropping practice and the surrounding vegetation (Manuscript I) as well as more...

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2011-05-01

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

  9. Trophic Interactions of Infant Bifidobacteria and Eubacterium hallii during L-Fucose and Fucosyllactose Degradation.

    Science.gov (United States)

    Schwab, Clarissa; Ruscheweyh, Hans-Joachim; Bunesova, Vera; Pham, Van Thanh; Beerenwinkel, Niko; Lacroix, Christophe

    2017-01-01

    subsp. suis were able to utilize L-fucose. This study identified a trophic interaction of infant bifidobacteria and E. hallii during L-fucose degradation, and pointed at E. hallii as a metabolically versatile species that occurs in infants and utilizes intermediates of bifidobacterial HMO fermentation.

  10. Hydration status and diurnal trophic interactions shape microbial community function in desert biocrusts

    Science.gov (United States)

    Kim, Minsu; Or, Dani

    2017-12-01

    Biological soil crusts (biocrusts) are self-organised thin assemblies of microbes, lichens, and mosses that are ubiquitous in arid regions and serve as important ecological and biogeochemical hotspots. Biocrust ecological function is intricately shaped by strong gradients of water, light, oxygen, and dynamics in the abundance and spatial organisation of the microbial community within a few millimetres of the soil surface. We report a mechanistic model that links the biophysical and chemical processes that shape the functioning of biocrust representative microbial communities that interact trophically and respond dynamically to cycles of hydration, light, and temperature. The model captures key features of carbon and nitrogen cycling within biocrusts, such as microbial activity and distribution (during early stages of biocrust establishment) under diurnal cycles and the associated dynamics of biogeochemical fluxes at different hydration conditions. The study offers new insights into the highly dynamic and localised processes performed by microbial communities within thin desert biocrusts.

  11. Hydration status and diurnal trophic interactions shape microbial community function in desert biocrusts

    Directory of Open Access Journals (Sweden)

    M. Kim

    2017-12-01

    Full Text Available Biological soil crusts (biocrusts are self-organised thin assemblies of microbes, lichens, and mosses that are ubiquitous in arid regions and serve as important ecological and biogeochemical hotspots. Biocrust ecological function is intricately shaped by strong gradients of water, light, oxygen, and dynamics in the abundance and spatial organisation of the microbial community within a few millimetres of the soil surface. We report a mechanistic model that links the biophysical and chemical processes that shape the functioning of biocrust representative microbial communities that interact trophically and respond dynamically to cycles of hydration, light, and temperature. The model captures key features of carbon and nitrogen cycling within biocrusts, such as microbial activity and distribution (during early stages of biocrust establishment under diurnal cycles and the associated dynamics of biogeochemical fluxes at different hydration conditions. The study offers new insights into the highly dynamic and localised processes performed by microbial communities within thin desert biocrusts.

  12. Rain forest promotes trophic interactions and diversity of trap-nesting Hymenoptera in adjacent agroforestry.

    Science.gov (United States)

    Klein, Alexandra-Maria; Steffan-Dewenter, Ingolf; Tscharntke, Teja

    2006-03-01

    1. Human alteration of natural ecosystems to agroecosystems continues to accelerate in tropical countries. The resulting world-wide decline of rain forest causes a mosaic landscape, comprising simple and complex agroecosystems and patchily distributed rain forest fragments of different quality. Landscape context and agricultural management can be expected to affect both species diversity and ecosystem services by trophic interactions. 2. In Central Sulawesi, Indonesia, 24 agroforestry systems, differing in the distance to the nearest natural forest (0-1415 m), light intensity (37.5-899.6 W/m(-2)) and number of vascular plant species (7-40 species) were studied. Ten standardized trap nests for bees and wasps, made from reed and knotweed internodes, were exposed in each study site. Occupied nests were collected every month, over a period totalling 15 months. 3. A total of 13,617 brood cells were reared to produce adults of 14 trap-nesting species and 25 natural enemy species, which were mostly parasitoids. The total number of species was affected negatively by increasing distance from forest and increased with light intensity of agroforestry systems. The parasitoids in particular appeared to benefit from nearby forests. Over a 500-m distance, the number of parasitoid species decreased from eight to five, and parasitism rates from 12% to 4%. 4. The results show that diversity and parasitism, as a higher trophic interaction and ecosystem service, are enhanced by (i) improved connectivity of agroecosystems with natural habitats such as agroforestry adjacent to rain forest and (ii) management practices to increase light availability in agroforestry, which also enhances richness of flowering plants in the understorey.

  13. 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.

  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. Study of a tri-trophic prey-dependent food chain model of interacting populations.

    Science.gov (United States)

    Haque, Mainul; Ali, Nijamuddin; Chakravarty, Santabrata

    2013-11-01

    The current paper accounts for the influence of intra-specific competition among predators in a prey dependent tri-trophic food chain model of interacting populations. We offer a detailed mathematical analysis of the proposed food chain model to illustrate some of the significant results that has arisen from the interplay of deterministic ecological phenomena and processes. Biologically feasible equilibria of the system are observed and the behaviours of the system around each of them are described. In particular, persistence, stability (local and global) and bifurcation (saddle-node, transcritical, Hopf-Andronov) analysis of this model are obtained. Relevant results from previous well known food chain models are compared with the current findings. Global stability analysis is also carried out by constructing appropriate Lyapunov functions. Numerical simulations show that the present system is capable enough to produce chaotic dynamics when the rate of self-interaction is very low. On the other hand such chaotic behaviour disappears for a certain value of the rate of self interaction. In addition, numerical simulations with experimented parameters values confirm the analytical results and shows that intra-specific competitions bears a potential role in controlling the chaotic dynamics of the system; and thus the role of self interactions in food chain model is illustrated first time. Finally, a discussion of the ecological applications of the analytical and numerical findings concludes the paper. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Invasive plant architecture alters trophic interactions by changing predator abundance and behavior.

    Science.gov (United States)

    Pearson, Dean E

    2009-03-01

    As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa), has fundamentally altered the architecture of native grassland vegetation. Here, I use long-term monitoring, observational studies, and field experiments to document how changes in vegetation architecture have affected native web spider populations and predation rates. Native spiders that use vegetation as web substrates were collectively 38 times more abundant in C. maculosa-invaded grasslands than in uninvaded grasslands. This increase in spider abundance was accompanied by a large shift in web spider community structure, driven primarily by the strong response of Dictyna spiders to C. maculosa invasion. Dictyna densities were 46-74 times higher in C. maculosa-invaded than native grasslands, a pattern that persisted over 6 years of monitoring. C. maculosa also altered Dictyna web building behavior and foraging success. Dictyna webs on C. maculosa were 2.9-4.0 times larger and generated 2.0-2.3 times higher total prey captures than webs on Achillea millefolium, their primary native substrate. Dictyna webs on C. maculosa also captured 4.2 times more large prey items, which are crucial for reproduction. As a result, Dictyna were nearly twice as likely to reproduce on C. maculosa substrates compared to native substrates. The overall outcome of C. maculosa invasion and its transformative effects on vegetation architecture on Dictyna density and web building behavior were to increase Dictyna predation on invertebrate prey >/=89 fold. These results indicate that invasive plants that change the architecture of native vegetation can substantially impact native food webs via nontraditional plant --> predator --> consumer

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

    International Nuclear Information System (INIS)

    Castellanos, Víctor; Chan-López, Ramón E.

    2017-01-01

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

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

    OpenAIRE

    Vahabnezhad, Arezoo

    2015-01-01

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

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

    Science.gov (United States)

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

    2011-09-01

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

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

    Science.gov (United States)

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

    2010-07-06

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

  1. Species co-occurrence affects the trophic interactions of two juvenile reef shark species in tropical lagoon nurseries in Moorea (French Polynesia).

    Science.gov (United States)

    Matich, Philip; Kiszka, Jeremy J; Mourier, Johann; Planes, Serge; Heithaus, Michael R

    2017-06-01

    Food web structure is shaped by interactions within and across trophic levels. As such, understanding how the presence and absence of predators, prey, and competitors affect species foraging patterns is important for predicting the consequences of changes in species abundances, distributions, and behaviors. Here, we used plasma δ 13 C and δ 15 N values from juvenile blacktip reef sharks (Carcharhinus melanopterus) and juvenile sicklefin lemon sharks (Negaprion acutidens) to investigate how species co-occurrence affects their trophic interactions in littoral waters of Moorea, French Polynesia. Co-occurrence led to isotopic niche partitioning among sharks within nurseries, with significant increases in δ 15 N values among sicklefin lemon sharks, and significant decreases in δ 15 N among blacktip reef sharks. Niche segregation likely promotes coexistence of these two predators during early years of growth and development, but data do not suggest coexistence affects life history traits, such as body size, body condition, and ontogenetic niche shifts. Plasticity in trophic niches among juvenile blacktip reef sharks and sicklefin lemon sharks also suggests these predators are able to account for changes in community structure, resource availability, and intra-guild competition, and may fill similar functional roles in the absence of the other species, which is important as environmental change and human impacts persist in coral reef ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2010-09-01

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

  3. Shark-Cetacean trophic interaction, Duinefontein, Koeberg, (5 Ma, South Africa

    Directory of Open Access Journals (Sweden)

    Romala Govender

    2015-11-01

    Full Text Available This study forms part of a larger project to reconstruct the Mio-Pliocene marine palaeoenvironment along South Africa’s west coast. It documents the shark–cetacean trophic interaction during the Zanclean (5 Ma at Duinefontein (Koeberg. The damage described on the fragmentary cetacean bones was compared with similar damage observed on fossils from Langebaanweg, a Mio-Pliocene site on the west coast of South Africa, and data present in the literature. This comparison showed that the damage was the result of shark bites. The state of preservation makes it difficult to determine if the shark bite marks were the cause of death or as a result of scavenging. The presence of the bite marks on the bone would, however, indicate some degree of skeletonisation. Bite marks on some cranial fragments would suggest that the cetacean’s body was in an inverted position typical of a floating carcass. The preservation of the material suggests that the bones were exposed to wave action resulting in their fragmentation as well as abrasion, polishing and rolling. It also suggests that the cetacean skeletons were exposed for a long time prior to burial. The morphology of the bites suggests that the damage was inflicted by sharks with serrated and unserrated teeth. Shark teeth collected from the deposit include megalodon (Carcharodon megalodon, white (Carcharodon carcharias as well as mako (Isurus sp. and Cosmopolitodus hastalis sharks, making these sharks the most likely predators/scavengers.

  4. Local ecological knowledge of artisanal fishermen in southern Bahia, Brazil, about trophic interactions of sharks

    Directory of Open Access Journals (Sweden)

    Márcio Luiz Vargas Barbosa Filho

    2016-09-01

    Full Text Available Despite the serious threats that affect shark species living along the central coast of Brazil, knowledge about the life history of these animals is still scarce. The present study describes the knowledge and perceptions of fishermen from southern Bahia, Brazil, on the trophic interactions of sharks. The objective of this work was to generate information that contributes to a better understanding of the life history of sharks from this poorly known region. In 2012, semi-structured interviews were conducted with 65 fishermen, with over 15 years of experience, about fisheries and aspects of shark feeding behavior. The study found that the participants have comprehensive ethno-ecological knowledge about shark feeding habits, describing 39 types of items as components of the diets of these animals. They are also able to recognize the favored items in the diet of each ethnospecies of shark. Similar studies about shark feeding habits along the Brazilian coast should be developed. This will generate more detailed knowledge and/or new scientific hypotheses about the interspecific relationships of these predators and their prey.

  5. 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)

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

    Science.gov (United States)

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

    2016-06-01

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

  7. Coupling auto trophic in vitro plant cultivation system to scanning electron microscope to study plant-fungal interactions

    Energy Technology Data Exchange (ETDEWEB)

    Jaeger, N. de; Decock, C.; Declereck, S.; Providencia, I. E. de la

    2010-07-01

    The interactions of plants with pathogens and beneficial micro-organisms have been seldom compared on the same host and under strict controlled auto trophic in vitro culture conditions. Here, the life cycle of two plant beneficial (Glomus sp. MUCL 41833 and Trichoderma harzianum) and one plant pathogen (Rhizoctonia solani) fungi were described on potato (Solanum tuberosum) plantlets under auto trophic in vitro culture conditions using video camera imaging and the scanning electron microscope (SEM). (i) The colony developmental pattern of the extraradical mycelium within the substrate, (ii) the reproduction structures and (iii) the three-dimensional spatial arrangements of the fungal hyphae within the potato root cells were successfully visualized, monitored and described. The combination of the autotrophic in vitro culture system and SEM represent a powerful tool for improving our knowledge on the dynamics of plant-fungal interactions. (Author) 41 refs.

  8. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-15

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

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  11. 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)

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

    Science.gov (United States)

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

    2012-12-01

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

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

    Science.gov (United States)

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

    2015-11-01

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

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

    Directory of Open Access Journals (Sweden)

    Kailen A Mooney

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

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

    Science.gov (United States)

    Clausen, Rebecca; York, Richard

    2008-04-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-15

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

  17. Microbial plankton communities in the coastal southeastern Black Sea: biomass, composition and trophic interactions

    Directory of Open Access Journals (Sweden)

    Ulgen Aytan

    2018-04-01

    Full Text Available Summary: We investigated biomass and composition of the pico-, nano- and microplankton communities in a coastal station of the southeastern Black Sea during 2011. We also examined trophic interactions within these communities from size-fractionated dilution experiments in February, June and December. Autotrophic and heterotrophic biomasses showed similar seasonal trends, with a peak in June, but heterotrophs dominated throughout the year. Autotrophic biomass was mainly comprised by nanoflagellates and diatoms in the first half of the year, and by dinoflagellates and Synechococcus spp. in the second half. Heterotrophic biomass was mostly dominated by heterotrophic bacteria, followed by nanoflagellates and microzooplankton. Dilution experiments suggest that nano- and microzooplankton were significant consumers of autotrophs and heterotrophic bacteria. More than 100% of bacterial production was consumed by grazers in all experiments, while 46%, 21% and 30% of daily primary production were consumed in February, June and December, respectively. In February, autotrophs were the main carbon source, but in December, it was heterotrophic bacteria. An intermediate situation was observed in June, with similar carbon flows from autotrophs and heterotrophic bacteria. Size-fraction dilution experiments suggested that heterotrophic nanoflagellates are an important link between the high heterotrophic bacterial biomass and microzooplankton. In summary, these results indicate that nano- and microzooplankton were responsible for comprising a significant fraction of total microbial plankton biomass, standing stocks, growth and grazing processes. This suggests that in 2011, the microbial food web was an important compartment of the planktonic food web in the coastal southeastern Black Sea. Keywords: Phytoplankton, Microzooplankton, Carbon biomass, Microbial food web, Grazing, Black Sea

  18. 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.

  19. The role of life histories and trophic interactions in population recovery.

    Science.gov (United States)

    Audzijonyte, Asta; Kuparinen, Anna

    2016-08-01

    Factors affecting population recovery from depletion are at the focus of wildlife management. Particularly, it has been debated how life-history characteristics might affect population recovery ability and productivity. Many exploited fish stocks have shown temporal changes towards earlier maturation and reduced adult body size, potentially owing to evolutionary responses to fishing. Whereas such life-history changes have been widely documented, their potential role on stock's ability to recover from exploitation often remains ignored by traditional fisheries management. We used a marine ecosystem model parameterized for Southeastern Australian ecosystem to explore how changes towards "faster" life histories might affect population per capita growth rate r. We show that for most species changes towards earlier maturation during fishing have a negative effect (3-40% decrease) on r during the recovery phase. Faster juvenile growth and earlier maturation were beneficial early in life, but smaller adult body sizes reduced the lifetime reproductive output and increased adult natural mortality. However, both at intra- and inter-specific level natural mortality and trophic position of the species were as important in determining r as species longevity and age of maturation, suggesting that r cannot be predicted from life-history traits alone. Our study highlights that factors affecting population recovery ability and productivity should be explored in a multi-species context, where both age-specific fecundity and survival schedules are addressed simultaneously. It also suggests that contemporary life-history changes in harvested species are unlikely to increase their resilience and recovery ability. © 2016 Society for Conservation Biology.

  20. 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...

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

    Science.gov (United States)

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

    2006-10-01

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

  2. 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.

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

    Science.gov (United States)

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

    2005-07-01

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

  4. Plasticity of trophic interactions among sharks from the oceanic south-western Indian Ocean revealed by stable isotope and mercury analyses

    Science.gov (United States)

    Kiszka, Jeremy J.; Aubail, Aurore; Hussey, Nigel E.; Heithaus, Michael R.; Caurant, Florence; Bustamante, Paco

    2015-02-01

    Sharks are a major component of the top predator guild in oceanic ecosystems, but the trophic relationships of many populations remain poorly understood. We examined chemical tracers of diet and habitat (δ15N and δ13C, respectively) and total mercury (Hg) concentrations in muscle tissue of seven pelagic sharks: blue shark (Prionace glauca), short-fin mako shark (Isurus oxyrinchus), oceanic whitetip shark (Carcharhinus longimanus), scalloped hammerhead shark (Sphyrna lewini), pelagic thresher shark (Alopias pelagicus), crocodile shark (Pseudocarcharias kamoharai) and silky shark (Carcharhinus falciformis), from the data poor south-western tropical Indian Ocean. Minimal interspecific variation in mean δ15N values and a large degree of isotopic niche overlap - driven by high intraspecific variation in δ15N values - was observed among pelagic sharks. Similarly, δ13C values of sharks overlapped considerably for all species with the exception of P. glauca, which had more 13C-depleted values indicating possibly longer residence times in purely pelagic waters. Geographic variation in δ13C, δ15N and Hg were observed for P. glauca and I. oxyrinchus. Mean Hg levels were similar among species with the exception of P. kamoharai which had significantly higher Hg concentrations likely related to mesopelagic feeding. Hg concentrations increased with body size in I. oxyrinchus, P. glauca and C. longimanus. Values of δ15N and δ13C varied with size only in P. glauca, suggesting ontogenetic shifts in diets or habitats. Together, isotopic data indicate that - with few exceptions - variance within species in trophic interactions or foraging habitats is greater than differentiation among pelagic sharks in the south-western Indian Ocean. Therefore, it is possible that this group exhibits some level of trophic redundancy, but further studies of diets and fine-scale habitat use are needed to fully test this hypothesis.

  5. 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.

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

    Science.gov (United States)

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

    2002-10-01

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

  7. Trophic interactions within the microbial food web in a tropical floodplain lake (Laguna Bufeos,Bolivia

    Directory of Open Access Journals (Sweden)

    Danny Rejas

    2005-06-01

    Full Text Available Whether the primary role of bacterioplankton is to act as "remineralizers" of nutrients or as direct nutritional source for higher trophic levels will depend on factors controlling their production and abundance. In tropical lakes, low nutrient concentration is probably the main factor limiting bacterial growth, while grazing by microzooplankton is generally assumed to be the main loss factor for bacteria. Bottom-up and top-down regulation of microbial abundance was studied in six nutrient limitation and dilution gradient-size fractionation in situ experiments. Bacteria, heterotrophic nanoflagellates (HNF, ciliates and rotifers showed relatively low densities. Predation losses of HNF and ciliates accounted for a major part of their daily production, suggesting a top-down regulation of protistan populations by rotifers. Phosphorus was found to be strongly limiting for bacterial growth, whereas no response to enrichment with Nitrogen or DOC was detected. HNF were the major grazers on bacteria (g=0.43 d-1 , the grazing coefficient increased when ciliates were added (g=0.80 d-1 but decreased when rotifers were added (g=0.23 d-1 probably due to nutrient recycling or top-down control of HNF and ciliates by rotifers. Rev. Biol. Trop. 53 (1-2:85-96. Epub 2005 Jun 24Que el bacterioplancton juegue básicamente un papel de reciclaje de nutrientes, o sea una fuente directa de nutrientes, depende de varios factores que afectan su producción y abundancia. En los lagos tropicales, la baja concentración de nutrientes es posiblemente el principal factor limitante del crecimiento bacteriano, y suele suponerse que la mayor pérdida poblacional de bacterias se debe a depredación por parte del microzooplancton. Estudiamos la regulación ascendente ("de abajo hacia arriba" y descendente ("de arriba hacia abajo" de abundancia bacteriana mediante seis experimentos in situ de limitación de nutrientes y de fraccionamiento de la dilución tamaño- gradiente. Bacterias

  8. Trophic interactions of the pelagic ecosystem over the Reykjanes Ridge as evaluated by fatty acid and stable isotope analyses

    Science.gov (United States)

    Petursdottir, H.; Gislason, A.; Falk-Petersen, S.; Hop, H.; Svavarsson, J.

    2008-01-01

    Trophic relationships of the important oceanic crustacean species Calanus finmarchicus, Meganyctiphanes norvegica and Sergestes arcticus, as well as the mesopelagic fishes Maurolicus muelleri, Benthosema glaciale and Sebastes mentella, were investigated over the Reykjanes Ridge in June 2003 and in June 2004. Measurements were performed of length, wet weight, dry weight, total lipid, lipid class, fatty acid and fatty alcohol profiles and stable isotopes (δ 13C and δ 15N). High amounts of the Calanus lipid markers, 20:1(n-9) and 22:1(n-11) in these species confirm the importance of Calanus spp. in this ecosystem. Comparisons of fatty acid/alcohol profiles by multivariate analysis revealed two main trophic pathways over the Reykjanes Ridge. In one pathway, Calanus spp. was an important part of the diet for the small mesopelagic fish species M. muelleri and B. glaciale and the shrimp S. arcticus, whereas in the other pathway, the euphausiid M. norvegica was the dominant food for the redfish S. mentella, and Calanus spp. were of less importance. M. muelleri and the smaller B. glaciale feed on C. finmarchicus, whereas the larger B. glaciale and S. arcticus select the larger, deeper-living C. hyperboreus. All investigated species are true pelagic species except for the shrimp S. arcticus, which seems to have a benthic feeding habit as well. The δ 15N levels show that of the species investigated, C. finmarchicus occupies the lowest trophic level (2.0) and the redfish, S. mentella, the highest (4.2). All the species were lipid rich, typical for subarctic pelagic ecosystem. Calanus finmarchicus, S. arcticus and B. glaciale store wax esters as their lipid stores, while M. norvegica, M. muelleri and S. mentella store triacylglycerols.

  9. 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.

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

    Science.gov (United States)

    Rojas, M Guadalupe; Morales-Ramos, Juan Alfredo

    2010-12-01

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

  11. 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.

  12. Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments

    Directory of Open Access Journals (Sweden)

    Yang Zamin K

    2010-05-01

    Full Text Available Abstract Background Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes. For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. The three species microbial community was comprised of Clostridium cellulolyticum, Desulfovibrio vulgaris Hildenborough, and Geobacter sulfurreducens and was grown under continuous culture conditions. Cellobiose served as the carbon and energy source for C. cellulolyticum, whereas D. vulgaris and G. sulfurreducens derived carbon and energy from the metabolic products of cellobiose fermentation and were provided with sulfate and fumarate respectively as electron acceptors. Results qPCR monitoring of the culture revealed C. cellulolyticum to be dominant as expected and confirmed the presence of D. vulgaris and G. sulfurreducens. Proposed metabolic modeling of carbon and electron flow of the three-species community indicated that the growth of C. cellulolyticum and D. vulgaris were electron donor limited whereas G. sulfurreducens was electron acceptor limited. Conclusions The results demonstrate that C. cellulolyticum, D. vulgaris, and G. sulfurreducens can be grown in coculture in a continuous culture system in which D. vulgaris and G. sulfurreducens are dependent upon the metabolic byproducts of C. cellulolyticum for nutrients. This represents a step towards developing a tractable model ecosystem comprised of members representing the functional groups of a trophic network.

  13. 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.

  14. 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

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

    Science.gov (United States)

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

    2018-01-01

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

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

    Science.gov (United States)

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

    2017-02-01

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

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

    Directory of Open Access Journals (Sweden)

    José A. Rodríguez-Preciado

    2014-01-01

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

  18. 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.

  19. 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.

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

    Directory of Open Access Journals (Sweden)

    Miguel Delibes

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

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

    Science.gov (United States)

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

    2015-01-01

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

  2. 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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  4. Trophic interactions and distribution of some Squaliforme sharks, including new diet descriptions for Deania calcea and Squalus acanthias.

    Directory of Open Access Journals (Sweden)

    Matthew R Dunn

    Full Text Available Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200-1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer; mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri; demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi; and a generalist diet of fishes and invertebrates (S. acanthias. The trophic levels of the species in each of the four groups were estimated as 4.18-4.24, 4.20-4.23, 4.24-4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.

  5. Trophic interactions and distribution of some Squaliforme sharks, including new diet descriptions for Deania calcea and Squalus acanthias.

    Science.gov (United States)

    Dunn, Matthew R; Stevens, Darren W; Forman, Jeffrey S; Connell, Amelia

    2013-01-01

    Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200-1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18-4.24, 4.20-4.23, 4.24-4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  7. Interactions among species in a tri-trophic system: the influence of ...

    African Journals Online (AJOL)

    BioMAP

    persistence/abundance are affected by more than two interacting species (Begon ... importance of methodology in revealing why an endangered population is ..... closely related butterfly which also oviposits on thyme buds) failed because the ...

  8. Consequences of variation in plant defense for biodiversity at higher trophic levels

    NARCIS (Netherlands)

    Poelman, E.H.; Loon, van J.J.A.; Dicke, M.

    2008-01-01

    Antagonistic interactions between insect herbivores and plants impose selection on plants to defend themselves against these attackers. Although selection on plant defense traits has typically been studied for pairwise plant¿attacker interactions, other community members of plant-based food webs are

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

    Science.gov (United States)

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

  10. Sweet Tetra-Trophic Interactions: Multiple Evolution of Nectar Secretion, a Defensive Extended Phenotype in Cynipid Gall Wasps.

    Science.gov (United States)

    Nicholls, James A; Melika, George; Stone, Graham N

    2017-01-01

    Many herbivores employ reward-based mutualisms with ants to gain protection from natural enemies. We examine the evolutionary dynamics of a tetra-trophic interaction in which gall wasp herbivores induce their host oaks to produce nectar-secreting galls, which attract ants that provide protection from parasitoids. We show that, consistent with other gall defensive traits, nectar secretion has evolved repeatedly across the oak gall wasp tribe and also within a single genus (Disholcaspis) that includes many nectar-inducing species. Once evolved, nectar secretion is never lost in Disholcaspis, consistent with high defensive value of this trait. We also show that evolution of nectar secretion is correlated with a transition from solitary to aggregated oviposition, resulting in clustered nectar-secreting galls, which produce a resource that ants can more easily monopolize. Such clustering is commonly seen in ant guard mutualisms. We suggest that correlated evolution between maternal oviposition and larval nectar induction traits has enhanced the effectiveness of this gall defense strategy.

  11. 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

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

    Science.gov (United States)

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

    2014-07-01

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

  13. 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

  14. Competitive Interactions between Invasive Nile Tilapia and Native Fish: The Potential for Altered Trophic Exchange and Modification of Food Webs

    Science.gov (United States)

    Martin, Charles W.; Valentine, Marla M.; Valentine, John F.

    2010-01-01

    Recent studies have highlighted both the positive and negative impacts of species invasions. Most of these studies have been conducted on either immobile invasive plants or sessile fauna found at the base of food webs. Fewer studies have examined the impacts of vagile invasive consumers on native competitors. This is an issue of some importance given the controlling influence that consumers have on lower order plants and animals. Here, we present results of laboratory experiments designed to assess the impacts of unintended aquaculture releases of the Nile tilapia (Oreochromis niloticus), in estuaries of the Gulf of Mexico, on the functionally similar redspotted sunfish (Lepomis miniatus). Laboratory choice tests showed that tilapia prefer the same structured habitat that native sunfish prefer. In subsequent interspecific competition experiments, agonistic tilapia displaced sunfish from their preferred structured habitats. When a piscivore (largemouth bass) was present in the tank with both species, the survival of sunfish decreased. Based on these findings, if left unchecked, we predict that the proliferation of tilapia (and perhaps other aggressive aquaculture fishes) will have important detrimental effects on the structure of native food webs in shallow, structured coastal habitats. While it is likely that the impacts of higher trophic level invasive competitors will vary among species, these results show that consequences of unintended releases of invasive higher order consumers can be important. PMID:21200433

  15. Competitive interactions between invasive Nile tilapia and native fish: the potential for altered trophic exchange and modification of food webs.

    Directory of Open Access Journals (Sweden)

    Charles W Martin

    2010-12-01

    Full Text Available Recent studies have highlighted both the positive and negative impacts of species invasions. Most of these studies have been conducted on either immobile invasive plants or sessile fauna found at the base of food webs. Fewer studies have examined the impacts of vagile invasive consumers on native competitors. This is an issue of some importance given the controlling influence that consumers have on lower order plants and animals. Here, we present results of laboratory experiments designed to assess the impacts of unintended aquaculture releases of the Nile tilapia (Oreochromis niloticus, in estuaries of the Gulf of Mexico, on the functionally similar redspotted sunfish (Lepomis miniatus. Laboratory choice tests showed that tilapia prefer the same structured habitat that native sunfish prefer. In subsequent interspecific competition experiments, agonistic tilapia displaced sunfish from their preferred structured habitats. When a piscivore (largemouth bass was present in the tank with both species, the survival of sunfish decreased. Based on these findings, if left unchecked, we predict that the proliferation of tilapia (and perhaps other aggressive aquaculture fishes will have important detrimental effects on the structure of native food webs in shallow, structured coastal habitats. While it is likely that the impacts of higher trophic level invasive competitors will vary among species, these results show that consequences of unintended releases of invasive higher order consumers can be important.

  16. Macrophage migration inhibitory factor (MIF) modulates trophic signaling through interaction with serine protease HTRA1

    DEFF Research Database (Denmark)

    Fex Svenningsen, Åsa; Loering, Svenja; Sørensen, Anna Lahn

    2017-01-01

    Macrophage migration inhibitory factor (MIF), a small conserved protein, is abundant in the immune- and central nervous system (CNS). MIF has several receptors and binding partners that can modulate its action on a cel-lular level. It is upregulated in neurodegenerative diseases and cancer although...

  17. Using Stable Isotopes of Carbon and Nitrogen to Evaluate Trophic Interactions in Aquatic Environments

    Science.gov (United States)

    Christensen, David R.; LaRoche, Andrew

    2012-01-01

    This paper describes a series of laboratory exercises for upper level biology courses, independent research and/or honors programs. Students sampled fish from a local water body with the assistance of a local fish and wildlife agency. Tissue samples from collected fish were utilized to obtain estimates of the stable isotopes delta[superscript 13]C…

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

    Science.gov (United States)

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

    2018-04-26

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

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

    DEFF Research Database (Denmark)

    Özkan, Korhan

    assembly is a complex phenomenon driven by the interplay between environmental species sorting, ecological interactions between species and dispersal, linking local communities with the surrounding communities as well as with their regional populations. Although the research on community assembly....... Local bird abundance was strongly linked with occupancy across the metacommunity (the bird communities in the Istranca landscape) as well as the species’ regional population and range size across the western Palearctic. Null model analyses showed that bird occupancy was non-randomly related to species...... environmental niche. Furthermore, species abundance and occupancy across both the metacommunity and the whole western Palearctic were significantly related to an independent species specialization index calculated for the French birds. Together these results indicated that forest bird community assembly...

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

    KAUST Repository

    Jin, Peng; Wang, Tifeng; Liu, Nana; Dupont, Sam; Beardall, John; Boyd, Philip W.; Riebesell, Ulf; Gao, Kunshan

    2015-01-01

    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.

  1. 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.

  2. Climate change affects low trophic level marine consumers: warming decreases copepod size and abundance.

    Science.gov (United States)

    Garzke, Jessica; Ismar, Stefanie M H; Sommer, Ulrich

    2015-03-01

    Concern about climate change has re-ignited interest in universal ecological responses to temperature variations: (1) biogeographical shifts, (2) phenology changes, and (3) size shifts. In this study we used copepods as model organisms to study size responses to temperature because of their central role in the pelagic food web and because of the ontogenetic length constancy between molts, which facilitates the definition of size of distinct developmental stages. In order to test the expected temperature-induced shifts towards smaller body size and lower abundances under warming conditions, a mesocosm experiment using plankton from the Baltic Sea at three temperature levels (ambient, ambient +4 °C, ambient -4 °C) was performed in summer 2010. Overall copepod and copepodit abundances, copepod size at all life stages, and adult copepod size in particular, showed significant temperature effects. As expected, zooplankton peak abundance was lower in warm than in ambient treatments. Copepod size-at-immature stage significantly increased in cold treatments, while adult size significantly decreased in warm treatments.

  3. 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.

  4. 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.

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

    NARCIS (Netherlands)

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

    2013-01-01

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

  6. 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

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

    Science.gov (United States)

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

    2018-04-01

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

  8. 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.

  9. Levels of Polybrominated Diphenyl Ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food web

    NARCIS (Netherlands)

    Boon, J.P.; Lewis, W.E.; Tjoen-A-Choy, M.R.; Allchin, C.R.; Law, R.J.; Boer, de J.

    2002-01-01

    The levels of individual PBDE congeners were investigated in the invertebrate species whelk (Buccinum undatum), seastar (Asterias rubens), and hermit crab (Pagurus bernhardus), the gadoid fish species whiting (Merlangius merlangus) and cod (Gadus morhua), and the marine mammal species harbor seal

  10. 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 ...

  11. 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.

  12. 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.

  13. 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.

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

    African Journals Online (AJOL)

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

  15. 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.

  16. Multi-tissue stable isotope analysis and acoustic telemetry reveal seasonal variability in the trophic interactions of juvenile bull sharks in a coastal estuary.

    Science.gov (United States)

    Matich, Philip; Heithaus, Michael R

    2014-01-01

    Understanding how natural and anthropogenic drivers affect extant food webs is critical to predicting the impacts of climate change and habitat alterations on ecosystem dynamics. In the Florida Everglades, seasonal reductions in freshwater flow and precipitation lead to annual migrations of aquatic taxa from marsh habitats to deep-water refugia in estuaries. The timing and intensity of freshwater reductions, however, will be modified by ongoing ecosystem restoration and predicted climate change. Understanding the importance of seasonally pulsed resources to predators is critical to predicting the impacts of management and climate change on their populations. As with many large predators, however, it is difficult to determine to what extent predators like bull sharks (Carcharhinus leucas) in the coastal Everglades make use of prey pulses currently. We used passive acoustic telemetry to determine whether shark movements responded to the pulse of marsh prey. To investigate the possibility that sharks fed on marsh prey, we modelled the predicted dynamics of stable isotope values in bull shark blood and plasma under different assumptions of temporal variability in shark diets and physiological dynamics of tissue turnover and isotopic discrimination. Bull sharks increased their use of upstream channels during the late dry season, and although our previous work shows long-term specialization in the diets of sharks, stable isotope values suggested that some individuals adjusted their diets to take advantage of prey entering the system from the marsh, and as such this may be an important resource for the nursery. Restoration efforts are predicted to increase hydroperiods and marsh water levels, likely shifting the timing, duration and intensity of prey pulses, which could have negative consequences for the bull shark population and/or induce shifts in behaviour. Understanding the factors influencing the propensity to specialize or adopt more flexible trophic interactions

  17. Trophic interaction between topmouth gudgeon (Pseudorasbora parva and the co-occurring species during summer in the Dniprodzerzhynsk reservoir

    Directory of Open Access Journals (Sweden)

    Didenko A.V.

    2015-01-01

    Full Text Available Topmouth gudgeon, Pseudorasbora parva is the most common invasive fish in Europe, which can compete with the juveniles of valuable commercial fishes. The goal of this work is to study the diet of topmouth gudgeon and trophic relationships with some native fishes inhabiting the littoral zone of the Dniprodzerzhynsk reservoir. The obtained relatively low values of diet overlaps between topmouth gudgeon and other co-occurring cyprinids such as juvenile roach, Rutilus rutilus; silver bream, Blicca bjoerkna; rudd, Scardinius erythrophthalmus; Prussian carp, Carassius gibelio and bleak, Abramis brama, indicate that it is not a serious food competitor for them, especially commercially valuable ones. On the contrary, high diet overlaps were observed among some native cyprinids such as juvenile roach, silver bream, rudd, and bleak. The major prey items of topmouth gudgeon were Chydorus sphaericus and chironomids, whereas other cyprinids selected Bosmina spp. This peculiarity may be due to different vertical distributions of these fish in the littoral zone of the reservoir, where topmouth gudgeon inhabit near-bottom water layers, where they preyed on near-bottom and benthic zooplankters and chironomids, while juvenile roach, silver bream, rudd, and juvenile and adult bleak live in higher water layers, where they preyed on pelagic zooplankton.

  18. Importance of interactions between food quality, quantity, and gut transit time on consumer feeding, growth, and trophic dynamics.

    Science.gov (United States)

    Mitra, Aditee; Flynn, Kevin J

    2007-05-01

    Ingestion kinetics of animals are controlled by both external food availability and feedback from the quantity of material already within the gut. The latter varies with gut transit time (GTT) and digestion of the food. Ingestion, assimilation efficiency, and thus, growth dynamics are not related in a simple fashion. For the first time, the important linkage between these processes and GTT is demonstrated; this is achieved using a biomass-based, mechanistic multinutrient model fitted to experimental data for zooplankton growth dynamics when presented with food items of varying quality (stoichiometric composition) or quantity. The results show that trophic transfer dynamics will vary greatly between the extremes of feeding on low-quantity/high-quality versus high-quantity/low-quality food; these conditions are likely to occur in nature. Descriptions of consumer behavior that assume a constant relationship between the kinetics of grazing and growth irrespective of food quality and/or quantity, with little or no recognition of the combined importance of these factors on consumer behavior, may seriously misrepresent consumer activity in dynamic situations.

  19. Trophic interactions of the endangered Southern river otter ( Lontra provocax) in a Chilean Ramsar wetland inferred from prey sampling, fecal analysis, and stable isotopes

    Science.gov (United States)

    Franco, Marcela; Guevara, Giovany; Correa, Loreto; Soto-Gamboa, Mauricio

    2013-04-01

    Non-invasive methodological approaches are highly recommended and commonly used to study the feeding ecology of elusive and threatened mammals. In this study, we use multiple lines of evidence to assess the feeding strategies of the endangered Southern river otter, by determining seasonal prey availability (electrofishing), analysis of undigested prey remains (spraints), and the use of stable isotopes (δ15N and δ13C) in otter spraints ( n = 262) and prey in a wetland ecosystem of southern Chile (39°49'S, 73°15'W). Fecal and isotopic analyses suggest that the otter diet is restricted to a few prey items, particularly the less-mobile, bottom-living, and larger prey such as crayfish ( Samastacus spinifrons, 86.11 %) and crabs ( Aegla spp., 32.45 %), supplemented opportunistically by cyprinids ( Cyprinus carpio, 9.55 %) and catfish ( Diplomystes camposensis, 5.66 %). The results suggest that the river otter is highly specialized in bottom foraging. Isotopic signatures of food sources and feces revealed a mid-upper trophic position for the Southern river otter, with either higher or lower δ15N values than their potential prey items. δ13C values for river otters were less enriched than their potential food resources. We suggest that due to their narrow trophic niche and possible dependence on only a few food items, this species may be highly vulnerable to the reduction in its prey populations. Finally, maintaining the ecological interactions between Southern river otters and their prey is considered a central priority for the survival of this endangered carnivore mammal.

  20. Mesoscale eddies are oases for higher trophic marine life

    KAUST Repository

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

    2012-01-01

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

  1. 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.

  2. 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.

  3. Reasons for Low Levels of Interactivity

    DEFF Research Database (Denmark)

    Etter, Michael

    2013-01-01

    The interactivity levels of online CSR communication are typically low. This study explores the reasons for the low levels of interactivity in the popular social media tool Twitter. An analysis of 41,864 Twitter messages (tweets) from the thirty most central corporate accounts in a CSR Twitter...... network is conducted. Comparisons (t-test) between CSR tweets and general tweets and between specialized CSR Twitter accounts and general accounts reveal that the low levels of interactivity are due to a reactive interaction approach and a lack of specialization....

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

    Directory of Open Access Journals (Sweden)

    Pei-Jen L Shaner

    2011-03-01

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

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

    Science.gov (United States)

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

    2015-07-23

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

  7. Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach.

    Science.gov (United States)

    Boxhammer, Tim; Taucher, Jan; Bach, Lennart T; Achterberg, Eric P; Algueró-Muñiz, María; Bellworthy, Jessica; Czerny, Jan; Esposito, Mario; Haunost, Mathias; Hellemann, Dana; Ludwig, Andrea; Yong, Jaw C; Zark, Maren; Riebesell, Ulf; Anderson, Leif G

    2018-01-01

    Ongoing acidification of the ocean through uptake of anthropogenic CO2 is known to affect marine biota and ecosystems with largely unknown consequences for marine food webs. Changes in food web structure have the potential to alter trophic transfer, partitioning, and biogeochemical cycling of elements in the ocean. Here we investigated the impact of realistic end-of-the-century CO2 concentrations on the development and partitioning of the carbon, nitrogen, phosphorus, and silica pools in a coastal pelagic ecosystem (Gullmar Fjord, Sweden). We covered the entire winter-to-summer plankton succession (100 days) in two sets of five pelagic mesocosms, with one set being CO2 enriched (~760 μatm pCO2) and the other one left at ambient CO2 concentrations. Elemental mass balances were calculated and we highlight important challenges and uncertainties we have faced in the closed mesocosm system. Our key observations under high CO2 were: (1) A significantly amplified transfer of carbon, nitrogen, and phosphorus from primary producers to higher trophic levels, during times of regenerated primary production. (2) A prolonged retention of all three elements in the pelagic food web that significantly reduced nitrogen and phosphorus sedimentation by about 11 and 9%, respectively. (3) A positive trend in carbon fixation (relative to nitrogen) that appeared in the particulate matter pool as well as the downward particle flux. This excess carbon counteracted a potential reduction in carbon sedimentation that could have been expected from patterns of nitrogen and phosphorus fluxes. Our findings highlight the potential for ocean acidification to alter partitioning and cycling of carbon and nutrients in the surface ocean but also show that impacts are temporarily variable and likely depending upon the structure of the plankton food web.

  8. Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach.

    Directory of Open Access Journals (Sweden)

    Tim Boxhammer

    Full Text Available Ongoing acidification of the ocean through uptake of anthropogenic CO2 is known to affect marine biota and ecosystems with largely unknown consequences for marine food webs. Changes in food web structure have the potential to alter trophic transfer, partitioning, and biogeochemical cycling of elements in the ocean. Here we investigated the impact of realistic end-of-the-century CO2 concentrations on the development and partitioning of the carbon, nitrogen, phosphorus, and silica pools in a coastal pelagic ecosystem (Gullmar Fjord, Sweden. We covered the entire winter-to-summer plankton succession (100 days in two sets of five pelagic mesocosms, with one set being CO2 enriched (~760 μatm pCO2 and the other one left at ambient CO2 concentrations. Elemental mass balances were calculated and we highlight important challenges and uncertainties we have faced in the closed mesocosm system. Our key observations under high CO2 were: (1 A significantly amplified transfer of carbon, nitrogen, and phosphorus from primary producers to higher trophic levels, during times of regenerated primary production. (2 A prolonged retention of all three elements in the pelagic food web that significantly reduced nitrogen and phosphorus sedimentation by about 11 and 9%, respectively. (3 A positive trend in carbon fixation (relative to nitrogen that appeared in the particulate matter pool as well as the downward particle flux. This excess carbon counteracted a potential reduction in carbon sedimentation that could have been expected from patterns of nitrogen and phosphorus fluxes. Our findings highlight the potential for ocean acidification to alter partitioning and cycling of carbon and nutrients in the surface ocean but also show that impacts are temporarily variable and likely depending upon the structure of the plankton food web.

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

    International Nuclear Information System (INIS)

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

    2009-01-01

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

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

    Science.gov (United States)

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

    2017-03-01

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

  11. 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

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

    KAUST Repository

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

    2014-01-01

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

  13. 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

  14. 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.

  15. 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.

  16. A novel framework for linking functional diversity of plants with other trophic levels for the quantification of ecosystem services.

    Czech Academy of Sciences Publication Activity Database

    Lavorel, S.; Storkey, J.; Bardgett, R.D.; de Bello, Francesco; Berg, M. P.; Le Roux, X.; Moretti, M.; Mulder, Ch.; Pakeman, R. J.; Diaz, S.; Harrington, R.

    2013-01-01

    Roč. 24, č. 5 (2013), 942-948 ISSN 1100-9233 R&D Projects: GA ČR GAP505/12/1296 Institutional support: RVO:67985939 Keywords : Functional trait * Ecosystem functioning * Biotic interactions Subject RIV: EF - Botanics Impact factor: 3.372, year: 2013

  17. Intraguild interactions between the predatory mites Neoseiulus californicus and Phytoseiulus persimilis

    NARCIS (Netherlands)

    Cakmak, I.; Janssen, A.; Sabelis, M.W.

    2006-01-01

    Abstract. Species at the same trophic level may interact through competition for food, but can also interact through intraguild predation. Intraguild predation is widespread at the second and third trophic level and the effects may cascade down to the plant level. The effects of intraguild predation

  18. 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...

  19. Trophic interactions between larger crocodylians and giant tortoises on Aldabra Atoll, Western Indian Ocean, during the Late Pleistocene.

    Science.gov (United States)

    Scheyer, Torsten M; Delfino, Massimo; Klein, Nicole; Bunbury, Nancy; Fleischer-Dogley, Frauke; Hansen, Dennis M

    2018-01-01

    Today, the UNESCO World Heritage Site of Aldabra Atoll is home to about 100 000 giant tortoises, Aldabrachelys gigantea , whose fossil record goes back to the Late Pleistocene. New Late Pleistocene fossils (age ca . 90-125 000 years) from the atoll revealed some appendicular bones and numerous shell fragments of giant tortoises and cranial and postcranial elements of crocodylians. Several tortoise bones show circular holes, pits and scratch marks that are interpreted as bite marks of crocodylians. The presence of a Late Pleistocene crocodylian species, Aldabrachampsus dilophus , has been known for some time, but the recently found crocodylian remains presented herein are distinctly larger than those previously described. This indicates the presence of at least some larger crocodylians, either of the same or of a different species, on the atoll. These larger crocodylians, likely the apex predators in the Aldabra ecosystem at the time, were well capable of inflicting damage on even very large giant tortoises. We thus propose an extinct predator-prey interaction between crocodylians and giant tortoises during the Late Pleistocene, when both groups were living sympatrically on Aldabra, and we discuss scenarios for the crocodylians directly attacking the tortoises or scavenging on recently deceased animals.

  20. Radioactive tracers as a tool for the study of in situ meiofaunal-microbial trophic interactions in marine sediments

    International Nuclear Information System (INIS)

    Carman, K.R.

    1989-01-01

    Three methods of delivering labeled substrates to natural cores of sediments were compared. Slurried sediments disrupted the sedimentary structure and significantly altered uptake of labeled substrates by copepod species. Thus, disruption of sedimentary structure can significantly alter microbial-meiofaunal interactions and influence the results of grazing studies. The [ 3 H]-thymidine technique for measuring bacterial production was evaluated. The metabolic fate of labeled thymidine in a coastal marine sediment was not consistent with assumptions necessary for measuring bacterial production or its consumption by meiofauna. Microautoradiography was used to demonstrate the sedimentary microalgae and heterotrophic bacteria can be selectively labeled with [ 14 C]bicarbonate and labeled organic substrates, respectively. A study was performed to determine if radioactivity measured in copepods from grazing experiments was the result of ingestion of labeled microorganisms or the result of uptake by non-feeding processes. Uptake of label by copepods from [ 14 C]-bicarbonate was due almost exclusively to grazing on microalgae. Uptake of label by copepods from [ 14 C]-acetate, however, resulted from activity by epicuticular bacteria and was not due to ingestion of labeled bacteria

  1. 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.

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

    International Nuclear Information System (INIS)

    Vizzini, Salvatrice; Mazzola, Antonio

    2006-01-01

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

  3. 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. 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...

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

    Science.gov (United States)

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

    2018-04-01

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

  6. Impacts of phosphate mining on trophic level- and spatial variation of selenium and radium-226 on Florida waterbirds

    International Nuclear Information System (INIS)

    Myers, O.B.; O'Meara, T.E.

    1993-01-01

    More than 74,000 ha of the Florida landscape have been disturbed by phosphate mining operations. These operations redistribute radionuclides in the uranium-238 decay series and other potentially toxic trace elements contained in the ore matrix, making them more available for uptake by wetland birds. The authors inventoried levels of radium-226 and selenium in the tissue of wood ducks, mottled ducks, common moorhens, and double-crested cormorants collected from reference areas and from phosphate-mine wetlands. Bones of waterfowl contained from 3--4 times more radium-226 than in individuals collected at reference areas. Radium-226 in moorhen and cormorant bones were less strongly affected by mining. Waterfowl muscle tissue contained 1-2 orders of magnitude less radium-226 than in bone. Selenium concentrations were significantly higher in avian liver and kidney tissues collected from phosphate-mine wetlands compared to reference wetlands. Cormorants accumulated up to 80 ppm selenium in liver. As many as 20% of cormorants from phosphate-mine wetlands contained liver selenium concentrations at levels which have caused reproduction problems in other avian species. Waterfowl and moorhens tissues contained less selenium than cormorants, but phosphate-mine birds contained significantly more selenium than reference area birds

  7. Effects on the function of three trophic levels in marine plankton communities under stress from the antifouling compound zinc pyrithione

    International Nuclear Information System (INIS)

    Hjorth, M.; Dahlloef, I.; Forbes, V.E.

    2006-01-01

    This study aimed to investigate functional responses of natural marine planktonic communities to stress from the antifouling compound zinc pyrithione (ZPT). Isotope labelling techniques ( 14 C) were applied to study bacterial incorporation of leucine, photosynthetic activity of phytoplankton and grazing of labelled prey by zooplankton communities for 6 days after exposures to nominal concentrations of 0, 5, 25, 50 nM ZPT in a mesocosm experiment in Isefjord, Denmark. Significant direct effects were visible on chlorophyll a concentrations, which decreased in all exposed communities, to between 48 and 36% of control concentrations on Day 3, 1 day after the last exposure. Phytoplankton activities were also significantly affected on Day 3 with activities between 9 and 26% of control levels, as was zooplankton activities in the 25 and 50 nM exposures. In the 50 nM exposure the total community zooplankton activity was reduced to 25 ± 4%, and per individual to 46 ± 11% of control levels. Bacterial communities showed positive indirect effects with high activities (up to 183 ± 40%) due to higher amounts of available substrate from algal death. Pollution induced community tolerance analyses performed on phytoplankton and bacterial communities at the end of the experiment indicated a development of increased tolerance for phytoplankton in the 50 nM exposed communities, whereas there were no changes in tolerance in the bacterial communities. Multivariate analysis of the integrated functional response by the plankton communities revealed a significant difference (p < 0.05) between exposed communities compared to controls in the first 3 days after last exposure and in the end of the experiment. The study provides evidence of diverse effects on the functions of marine plankton communities under stress from a pollutant. Direct effects lead to cascading indirect effects throughout the community, eventually causing different developments. Continuous exposure to ZPT could lead to

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

    Science.gov (United States)

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

    2014-05-15

    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. Published by Elsevier Ltd.

  9. 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.

  10. 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

  11. 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.

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

    Science.gov (United States)

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

    2015-01-01

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

  13. Dilution of 210Pb by organic sedimentation in lakes of different trophic states, and application to studies of sediment-water interactions

    International Nuclear Information System (INIS)

    Binford, M.W.; Brenner, M.

    1986-01-01

    Lake sediments reflect conditions in the water column and can be used for rapid, integrative measurements of limnological variables. Examination of 210 Pb-dated cores from 12 Florida lakes of widely differing trophic state (expressed as Carlson's trophic state index: TSI) shows that net accumulation rate of organic matter is related to primary productivity in the water column. In 26 other lakes the activity of unsupported 210 Pb g -1 organic matter in surficial sediments is inversely related to trophic state and, therefore, to organic accumulation rate. From this observation, the authors develop a new method that uses fallout 210 Pb as a dilution tracer to calculate net sedimentary accumulation rates of any material in surface mud. They demonstrate strong relationships between net loss rate of biologically important materials (C, N, P, and pigments) and their respective water concentrations (expressed as TSI). Multiple regression models incorporating net sediment accumulation rates of all four variables explain up to 70% of the lake-to-lake variation of TSI. The 210 Pb-dilution method has application for studies for material cycling, paleolimnology, and sediment accumulation processes

  14. 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.

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

    Science.gov (United States)

    Bacalso, Regina Therese M.; Wolff, Matthias

    2014-11-01

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

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

    Science.gov (United States)

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

    2009-05-01

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

  17. Trigeminal trophic syndrome

    Directory of Open Access Journals (Sweden)

    Parimalam Kumar

    2014-01-01

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

  18. 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.

  19. The tempo-spatial variations of phytoplankton diversities and their correlation with trophic state levels in a large eutrophic Chinese lake

    DEFF Research Database (Denmark)

    Yang, Bin; Jiang, Yu-Jiao; He, Wei

    2016-01-01

    status of the lake. The present study indicated that the Margalef index of all samples was as low as 0.799 ± 0.543 in summer (August 2011) and as high as 1.467 ± 0.653 in winter (February 2012). The Margalef index of the river samples had a high mean value and substantial variation compared with the lake...... occurred in the eastern lake, especially in the middle of the lake, in autumn and winter. The total trophic state index (TSI) in all samples exhibited a significant negative correlation with the Margalef (r = −0.726) and Peilou (r = −0.530) indices but a significant positive correlation with the Shannon...

  20. Trophic strategies of unicellular plankton

    DEFF Research Database (Denmark)

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

    2017-01-01

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

  1. 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.

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

    Science.gov (United States)

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

    2018-06-19

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

  3. Marine snow, zooplankton and thin layers: indications of a trophic link from small-scale sampling with the Video Plankton Recorder

    DEFF Research Database (Denmark)

    Möller, Klas O.; St. John, Michael; Temming, Axel

    2012-01-01

    Marine aggregates of biogenic origin, known as marine snow, are considered to play a major role in the ocean’s particle flux and may represent a concentrated food source for zooplankton. However, observing the marine snow−zooplankton interaction in the field is difficult since conventional net sa...... to aggregates and demonstrating feeding behaviour, which also suggests a trophic interaction. Our observations highlight the potential significance of marine snow in marine ecosystems and its potential as a food resource for various trophic levels, from bacteria up to fish...

  4. State level operations and interaction with facility level systems

    International Nuclear Information System (INIS)

    Bellinger, J.

    1989-01-01

    The role of the State System of Accounting for and Control of Nuclear Materials at the State level, particularly the role of the National Authority, in ensuring that both national and international safeguards objectives are met is discussed. The legislative basis for the National Authority is examined. The activities of Australia's National Authority - the Australian Safeguards Office - are described

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

    Science.gov (United States)

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

    2012-01-01

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

  6. Tri-trophic interactions between Bt cotton, the herbivore Aphis gossypii Glover (Homoptera: Aphididae), and the predator Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae).

    Science.gov (United States)

    Guo, Jian-Ying; Wan, Fang-Hao; Dong, Liang; Lövei, Gábor L; Han, Zhao-Jun

    2008-02-01

    Tri-trophic impacts of transgenic Bacillus thuringiensis (Bt) cotton GK12 and NuCOTN 99B were studied using a predator, the great lacewing Chrysopa pallens (Rambur), and its prey, the cotton aphid Aphis gossypii Glover, in laboratory feeding experiments. The parental nontransgenic cotton cultivar of GK12 was used as control. The predator was fed with uniform (aphids from a single cultivar) or mixed prey (aphids from the three cotton cultivars provided on alternate days). Mortality and development of the immature stages, pupal body mass, adult sex ratio, fecundity, and egg viability of C. pallens were measured. When fed GK12-originated aphid prey, pupal body mass of C. pallens was significantly higher than that of the control, more females emerged, and these females laid significantly more eggs. Other parameters were not impacted. Females emerging from larvae maintained on NuCOTN 99B-originated prey laid fewer eggs than those maintained on GK12. Other measurements did not differ significantly between the two Bt cotton cultivars. Compared with the control, mixed feeding significantly prolonged pupal development time and increased pupal body mass and percentage of females but did not affect other parameters. These results indicate that C. pallens is sensitive to aphid prey from different cotton cultivars. Transgenic Bt cotton GK12-originated aphid prey has no adverse impact on survival, development, and fecundity of C. pallens. Between the two Bt cotton cultivars, NuCOTN 99B-originated aphid prey provided to C. pallens in the larval stage may lower female fecundity. Mixed feeding of C. pallens with the two Bt cotton-originated prey and non-Bt prey may have some adverse impacts on pupal development.

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

    Science.gov (United States)

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

    2008-03-01

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

  8. 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.

  9. Electric Vehicle Interaction at the Electrical Circuit Level

    Science.gov (United States)

    2018-01-01

    The objective of the Electric Vehicle Interaction at the Electrical Circuit Level project was to investigate electric vehicle (EV) charging as a means of mitigating transient over-voltages (TOVs) on the circuit level electric utility distribution gri...

  10. Radiation levels in the SSC interaction regions

    Energy Technology Data Exchange (ETDEWEB)

    Groom, D.E. [ed.

    1988-06-10

    The radiation environment in a typical SSC detector has been evaluated using the best available particle production models coupled with Monte Carlo simulations of hadronic and electromagnetic cascades. The problems studied include direct charged particle dose, dose inside a calorimeter from the cascades produced by incident photons and hadrons, the flux of neutrons and photons backscattered from the calorimeter into a central cavity, and neutron flux in the calorimeter. The luminosity lifetime at the SSC is dominated by collision losses in the interaction regions, where the luminosity is equivalent to losing an entire full-energy proton beam into the apparatus every six days. The result of an average p-p collision can be described quite simply. The mean charged multiplicity is about 110, and the particles are distributed nearly uniformly in pseudorapidity ({eta}) over all the angles of interest. The transverse momentum distribution is independent of angle, and for our purposes may be written as p{perpendicular}exp(-p{perpendicular}/{beta}). The mean value of p{perpendicular} may be as high as 0.6 GeV/c. Most of the radiation is produced by the very abundant low-p{perpendicular} particles. The dose or neutron fluence produced by individual particles in this energy region are simulated over a wide variety of conditions, and several measurements serve to confirm the simulation results. In general, the response (a dose, fluence, the number of backscattered neutrons, etc.) for an incident particle of momentum p can be parameterized in the form Np{sup {alpha}}, where 0.5 < {alpha}< 1.0. The authors believe most of their results to be accurate to within a factor of two or three, sufficiently precise to serve as the basis for detailed designs.

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

    Science.gov (United States)

    Sato, Takuya; Watanabe, Katsutoshi

    2014-07-01

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

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

    Science.gov (United States)

    Elbroch, L Mark; Wittmer, Heiko U

    2012-10-23

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

  13. Trophic signatures of seabirds suggest shifts in oceanic ecosystems

    Science.gov (United States)

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

    2018-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Gkenas C.

    2016-01-01

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

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

    Science.gov (United States)

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

    2017-04-01

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

  16. 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.

  17. 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

    . Improved understanding of the complex interactions governing these food web properties is essential to further refine estimates of climate-driven productivity changes across trophic levels.

  18. 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.

  19. Levels of Interaction Provided by Online Distance Education Models

    Science.gov (United States)

    Alhih, Mohammed; Ossiannilsson, Ebba; Berigel, Muhammet

    2017-01-01

    Interaction plays a significant role to foster usability and quality in online education. It is one of the quality standard to reveal the evidence of practice in online distance education models. This research study aims to evaluate levels of interaction in the practices of distance education centres. It is aimed to provide online distance…

  20. Ferromagnetic interaction model of activity level in workplace communication

    Science.gov (United States)

    Akitomi, Tomoaki; Ara, Koji; Watanabe, Jun-ichiro; Yano, Kazuo

    2013-03-01

    The nature of human-human interaction, specifically, how people synchronize with each other in multiple-participant conversations, is described by a ferromagnetic interaction model of people’s activity levels. We found two microscopic human interaction characteristics from a real-environment face-to-face conversation. The first characteristic is that people quite regularly synchronize their activity level with that of the other participants in a conversation. The second characteristic is that the degree of synchronization increases as the number of participants increases. Based on these microscopic ferromagnetic characteristics, a “conversation activity level” was modeled according to the Ising model. The results of a simulation of activity level based on this model well reproduce macroscopic experimental measurements of activity level. This model will give a new insight into how people interact with each other in a conversation.

  1. Trophic structure of a coastal fish community determined with diet and stable isotope analyses.

    Science.gov (United States)

    Malek, A J; Collie, J S; Taylor, D L

    2016-09-01

    A combination of dietary guild analysis and nitrogen (δ(15) N) and carbon (δ(13) C) stable-isotope analysis was used to assess the trophic structure of the fish community in Rhode Island and Block Island Sounds, an area off southern New England identified for offshore wind energy development. In the autumn of 2009, 2010 and 2011, stomach and tissue samples were taken from 20 fish and invertebrate species for analysis of diet composition and δ(15) N and δ(13) C signatures. The food chain in Rhode Island and Block Island Sounds comprises approximately four trophic levels within which the fish community is divided into distinct dietary guilds, including planktivores, benthivores, crustacivores and piscivores. Within these guilds, inter-species isotopic and dietary overlap is high, suggesting that resource partitioning or competitive interactions play a major role in structuring the fish community. Carbon isotopes indicate that most fishes are supported by pelagic phytoplankton, although there is evidence that benthic production also plays a role, particularly for obligate benthivores such as skates Leucoraja spp. This type of analysis is useful for developing an ecosystem-based approach to management, as it identifies species that act as direct links to basal resources as well as species groups that share trophic roles. © 2016 The Fisheries Society of the British Isles.

  2. Interactions between temperature and nutrients across levels of ecological organization.

    Science.gov (United States)

    Cross, Wyatt F; Hood, James M; Benstead, Jonathan P; Huryn, Alexander D; Nelson, Daniel

    2015-03-01

    Temperature and nutrient availability play key roles in controlling the pathways and rates at which energy and materials move through ecosystems. These factors have also changed dramatically on Earth over the past century as human activities have intensified. Although significant effort has been devoted to understanding the role of temperature and nutrients in isolation, less is known about how these two factors interact to influence ecological processes. Recent advances in ecological stoichiometry and metabolic ecology provide a useful framework for making progress in this area, but conceptual synthesis and review are needed to help catalyze additional research. Here, we examine known and potential interactions between temperature and nutrients from a variety of physiological, community, and ecosystem perspectives. We first review patterns at the level of the individual, focusing on four traits--growth, respiration, body size, and elemental content--that should theoretically govern how temperature and nutrients interact to influence higher levels of biological organization. We next explore the interactive effects of temperature and nutrients on populations, communities, and food webs by synthesizing information related to community size spectra, biomass distributions, and elemental composition. We use metabolic theory to make predictions about how population-level secondary production should respond to interactions between temperature and resource supply, setting up qualitative predictions about the flows of energy and materials through metazoan food webs. Last, we examine how temperature-nutrient interactions influence processes at the whole-ecosystem level, focusing on apparent vs. intrinsic activation energies of ecosystem processes, how to represent temperature-nutrient interactions in ecosystem models, and patterns with respect to nutrient uptake and organic matter decomposition. We conclude that a better understanding of interactions between temperature and

  3. STUDY OF CHANGES IN LEVELS OF SOME CY- TOKINES AND SIgA IN CHRONIC HYPER- TROPHIC PHARYNGITIS WITH THE USE OF IM- MUNOCORRECTION

    Directory of Open Access Journals (Sweden)

    Egoshina V. O.

    2013-12-01

    Full Text Available Found that in this pathology is a significant increase in pro-and anti-inflammatory cytokines in patients due to the predominance of pro-inflammatory cytokines during exacerbation of chronic inflammation of the lymphoid tissues of the pharynx. Found that after the standard treatment for patients with hypertrophic pharyngitis content IFN-γ levels and sIgA in the oropharyngeal secretions reaches levels of the control group , provided intermittent effect in terms ofreducing cytokine levels in the serum of 45 and 90 days after initiation of treatment and partial restoration of local immunity oropharynx. In a joint application Derinat and IRS-19 was observed acceleration of restoring the balance of cellular and humoral immunity, no recurrence of the disease for the entire period of observation, that the efficiency of treatment of chronic hypertrophic pharyngitis.

  4. Age-Related Changes in Binaural Interaction at Brainstem Level.

    Science.gov (United States)

    Van Yper, Lindsey N; Vermeire, Katrien; De Vel, Eddy F J; Beynon, Andy J; Dhooge, Ingeborg J M

    2016-01-01

    Age-related hearing loss hampers the ability to understand speech in adverse listening conditions. This is attributed to a complex interaction of changes in the peripheral and central auditory system. One aspect that may deteriorate across the lifespan is binaural interaction. The present study investigates binaural interaction at the level of the auditory brainstem. It is hypothesized that brainstem binaural interaction deteriorates with advancing age. Forty-two subjects of various age participated in the study. Auditory brainstem responses (ABRs) were recorded using clicks and 500 Hz tone-bursts. ABRs were elicited by monaural right, monaural left, and binaural stimulation. Binaural interaction was investigated in two ways. First, grand averages of the binaural interaction component were computed for each age group. Second, wave V characteristics of the binaural ABR were compared with those of the summed left and right ABRs. Binaural interaction in the click ABR was demonstrated by shorter latencies and smaller amplitudes in the binaural compared with the summed monaural responses. For 500 Hz tone-burst ABR, no latency differences were found. However, amplitudes were significantly smaller in the binaural than summed monaural condition. An age-effect was found for 500 Hz tone-burst, but not for click ABR. Brainstem binaural interaction seems to decline with age. Interestingly, these changes seem to be stimulus-dependent.

  5. The hormone prolactin is a novel, endogenous trophic factor able to regulate reactive glia and to limit retinal degeneration.

    Science.gov (United States)

    Arnold, Edith; Thebault, Stéphanie; Baeza-Cruz, German; Arredondo Zamarripa, David; Adán, Norma; Quintanar-Stéphano, Andrés; Condés-Lara, Miguel; Rojas-Piloni, Gerardo; Binart, Nadine; Martínez de la Escalera, Gonzalo; Clapp, Carmen

    2014-01-29

    Retinal degeneration is characterized by the progressive destruction of retinal cells, causing the deterioration and eventual loss of vision. We explored whether the hormone prolactin provides trophic support to retinal cells, thus protecting the retina from degenerative pressure. Inducing hyperprolactinemia limited photoreceptor apoptosis, gliosis, and changes in neurotrophin expression, and it preserved the photoresponse in the phototoxicity model of retinal degeneration, in which continuous exposure of rats to bright light leads to retinal cell death and retinal dysfunction. In this model, the expression levels of prolactin receptors in the retina were upregulated. Moreover, retinas from prolactin receptor-deficient mice exhibited photoresponsive dysfunction and gliosis that correlated with decreased levels of retinal bFGF, GDNF, and BDNF. Collectively, these data unveiled prolactin as a retinal trophic factor that may regulate glial-neuronal cell interactions and is a potential therapeutic molecule against retinal degeneration.

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

    NARCIS (Netherlands)

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

    2001-01-01

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

  7. Biomagnification and bioaccumulation of mercury in two fish species from different trophic levels in the Bahia de Cartagena and the Cienaga Grande de Santa Marta, Colombian Caribbean

    International Nuclear Information System (INIS)

    Alonso, D.; Campos, N.

    1999-01-01

    During the decade of the 70's a chlor-alkali plant dumped between 11 and 15 tons of mercury indiscriminately into the Bahia de Cartagena (BC), elevating the levels of this metal in the biotic and abiotic components of the ecosystem. Although two decades have passed since the plant was closed, the sediments of the bay seem to be an important source of mercury to the marine environment. The present work measured the contents of mercury in the sediment and determined the processes of bioaccumulation and biomagnification in two species of fishes of commercial importance: the parassi mullet (Mugil incilis) and the striped mojarra (Eugerres plumieri), a detritivore and an omnivore, respectively

  8. 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.

  9. 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

  10. Three-body interactions and the Landau levels using Nikiforov

    Indian Academy of Sciences (India)

    In this article, the eigenvalues for the three-body interactions on the line and the Landau levels in the presence of topological defects have been regenerated by the Nikiforov–Uvarov (NU) method. Two exhaustive lists of such exactly solvable potentials are given.

  11. Three-body interactions and the Landau levels using Nikiforov ...

    Indian Academy of Sciences (India)

    In this article, the eigenvalues for the three-body interactions on the line and the Landau levels in the presence of topological defects have been regenerated by the Nikiforov–Uvarov (NU) method. Two exhaustive lists of such exactly solvable potentials are given. Keywords. Nikiforov–Uvarov (NU) method; three-body ...

  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. Trophic transfer of metal nanoparticles in freshwater ecosystems

    DEFF Research Database (Denmark)

    Tangaa, Stine Rosendal

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

  14. Food Web and Trophic Interaction and Development

    Czech Academy of Sciences Publication Activity Database

    Hrbáček, Jaroslav

    2010-01-01

    Roč. 3, - (2010), s. 45-70. ISBN 978-90-481-9264-9. ISSN 1875-1261 Institutional research plan: CEZ:AV0Z60170517 Keywords : biological indication * energy transfer * chlorophyll concentration * top-down effect * zooplankton size Subject RIV: DA - Hydrology ; Limnology

  15. Interactive evolution of levels for a competitive multiplayer FPS

    DEFF Research Database (Denmark)

    Olsted, P.T.; Ma, B.; Risi, S.

    2015-01-01

    Traditionally a dedicated level designer has to create every aspect of a level by hand, distribute and gather people to test it. Especially for multiplayer maps, the cyclic process of developing and testing can be quite cumbersome and time consuming. This paper presents a novel approach to provide...... live generation of levels for such multiplayer maps through procedural content generation and interactive evolution. The approach is demonstrated in the FPSEvolver video game that aims at replicating the look and feel of popular games like Counter-Strike. Without leaving the game a group of players can......”. The presented approach can generate enjoyable maps that adapt to the preferences of players across a range of skill levels. Several distinct types of levels were created during testing, which range from open to closed, and complex to simple, each fitting closely with what the different players consider a good...

  16. ΔS=O weak interactions at the quark level

    International Nuclear Information System (INIS)

    McKellar, B.H.J.

    1987-01-01

    The calculation of short distance gluon exchange corrections to the ΔS=O weak interaction at the quark level is described. Results are given for the coefficients of the 36 independent 4 quark operators involving ud, d, and s quarks explicitly, and for the 16 independent operators which remain when s quarks are eliminated and only u and d quarks explicitly occur in the operators. There is considerable uncertainty in the interpretation of parity violating phenomena in nuclei at the moment, as will be clear from the proceedings of this workshop. There is of course a possibility that our nuclear structure calculations are incomplete, but what I want to emphasize here is the fact that the existing calculations of the weak coupling constants at the hadronic level have been based on an inadequate quark level description. Little of what I have to say is new. I refer you to various papers by Rober Miller and myself on ΔS=1 interactions and ΔS=O interactions at the quark level, and to our review. However the only attempt to calculate observable effects using a quark level Hamiltonian with all of the necessary structure is that of Goldman and Preston and their work was a high energy rather than a low energy application. This paper is a pedagogical discussion of the basic physics of this ΔS=O weak Hamiltonian at the quark level, and is designed to encourage its use in future calculations of the weak hadronic coupling constants. Some previously unpublished results on a simplified approximate form of the ΔS=O Hamiltonian are given here to facilitate use of this quark level Hamiltonian in future calculations. (author)

  17. Intermediate-Level Knowledge in Child-Computer Interaction

    DEFF Research Database (Denmark)

    Barendregt, Wolmet; Torgersson, Olof; Eriksson, Eva

    2017-01-01

    Based on an analysis of all papers at IDC from 2003 to 2016 this paper urges the Child-Computer Interaction (CCI) field to start formulating intermediate-level knowledge, in the form of e.g. strong concepts. Our analysis showed that 40% of all papers at the Interaction Design and Children...... conference presents the design of an artefact accompanied by an evaluation (to which we will refer as 'artefact-centered' papers). While exploring the design space in the form of artefacts is important and valuable, it can be argued that those artefact-centered papers generally make a smaller contribution...... to the field as a whole, which is also visible in the number of citations to such papers in comparison to the number of citations to other kinds of papers. As a first step towards more intermediate-level knowledge, we have thus attempted to formulate and ground three suggestions for strong concepts in CCI...

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

    Directory of Open Access Journals (Sweden)

    Edoardo Calizza

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

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

    Science.gov (United States)

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

    2018-01-01

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

  20. Immobilized enzymes: understanding enzyme - surface interactions at the molecular level.

    Science.gov (United States)

    Hoarau, Marie; Badieyan, Somayesadat; Marsh, E Neil G

    2017-11-22

    Enzymes immobilized on solid supports have important and industrial and medical applications. However, their uses are limited by the significant reductions in activity and stability that often accompany the immobilization process. Here we review recent advances in our understanding of the molecular level interactions between proteins and supporting surfaces that contribute to changes in stability and activity. This understanding has been facilitated by the application of various surface-sensitive spectroscopic techniques that allow the structure and orientation of enzymes at the solid/liquid interface to be probed, often with monolayer sensitivity. An appreciation of the molecular interactions between enzyme and surface support has allowed the surface chemistry and method of enzyme attachement to be fine-tuned such that activity and stability can be greatly enhanced. These advances suggest that a much wider variety of enzymes may eventually be amenable to immobilization as green catalysts.

  1. Vitamin D and muscle trophicity.

    Science.gov (United States)

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

    2017-05-01

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

  2. Trophic structure of macroinvertebrates in tropical pasture streams

    Directory of Open Access Journals (Sweden)

    Bruna Neves da Silveira-Manzotti

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

  3. 210Po and 210Pb in a pelagic trophic chain

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  4. Fluid/structure interaction in BERDYNE (Level 4)

    International Nuclear Information System (INIS)

    Fox, M.J.H.

    1988-02-01

    A fluid-structure interaction capability has been developed for Level 4 of the finite element dynamics code BERDYNE, as part of the BERSAFE structural analysis system. This permits analysis of small amplitude free or forced vibration of systems comprising elastic structural components and inviscid volumes of possibly compressible fluid. Free fluid surfaces under the influence of gravity may be present. The formulation chosen uses the rigid walled fluid modes, calculated in a preliminary stage, as a basis for description of the coupled system, providing symmetric system matrices for which efficient solution procedures are available. The inclusion of the fluid modal variables within the system matrices is carried out through the use of the BERDYNE 'substructuring' feature, which allows the inclusion of very general 'super-elements' among the normal structural elements. The program also has a seismic analysis capability, used for the analysis of fluid-structure systems subjected to a specified support acceleration time history. In this case analysis is carried out in terms of relative structural motions, but absolute fluid pressures. Application of the BERDYNE fluid/structure interaction capability to some simple test cases produced results in good agreement with results obtained by analytic or independent numerical techniques. Full instructions on the use of the facility will be included in the BERDYNE Level 4 documentation. Interim documentation for the pre-release version is available from the author. (author)

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

    Directory of Open Access Journals (Sweden)

    Ahmad Zahid

    2015-09-01

    monthly for one year at three zones. Fish samples were placed in separate labelled plastic bags according to the time scale and location sampling, then gut contents were analyzed. The data of vacuity index, number of prey, prey dominant, diet breadth, and trophic level were analyzed. For each of 106 fish species, between 1 and 380 stomachs, were examined. The vacuity index was also different among species. Five of 106 species had a vacuity index of “0” and total number of food items consumed varied between fish species, ranging from three items to 27 items. The overall diet breadth (Bi was relatively low among species, ranging from 0.20 to 0.78, with most of them between 0.20 and 0.48. Calanoid copepods comprised the most common food item consumed by all the fishes examined. Fishes occurring can be broadly categorized into seven different trophic guilds. The trophic level of fish communities ranged from 2.05 to 4.73. Spatio-temporal variation of food web was influenced of ontogenetic shift, food availability, habitat characteristic, and migration of some species in Segara Menyan coastal lagoon. Keywords: trophic interaction, lagoon, fishes, spatio-temporal variation, trophic guild

  6. Modeling Adsorption-Desorption Processes at the Intermolecular Interactions Level

    Science.gov (United States)

    Varfolomeeva, Vera V.; Terentev, Alexey V.

    2018-01-01

    Modeling of the surface adsorption and desorption processes, as well as the diffusion, are of considerable interest for the physical phenomenon under study in ground tests conditions. When imitating physical processes and phenomena, it is important to choose the correct parameters to describe the adsorption of gases and the formation of films on the structural materials surface. In the present research the adsorption-desorption processes on the gas-solid interface are modeled with allowance for diffusion. Approaches are proposed to describe the adsorbate distribution on the solid body surface at the intermolecular interactions level. The potentials of the intermolecular interaction of water-water, water-methane and methane-methane were used to adequately modeling the real physical and chemical processes. The energies calculated by the B3LYP/aug-cc-pVDZ method. Computational algorithms for determining the average molecule area in a dense monolayer, are considered here. Differences in modeling approaches are also given: that of the proposed in this work and the previously approved probabilistic cellular automaton (PCA) method. It has been shown that the main difference is due to certain limitations of the PCA method. The importance of accounting the intermolecular interactions via hydrogen bonding has been indicated. Further development of the adsorption-desorption processes modeling will allow to find the conditions for of surface processes regulation by means of quantity adsorbed molecules control. The proposed approach to representing the molecular system significantly shortens the calculation time in comparison with the use of atom-atom potentials. In the future, this will allow to modeling the multilayer adsorption at a reasonable computational cost.

  7. Ice sheet-ocean interactions and sea level change

    Science.gov (United States)

    Heimbach, Patrick

    2014-03-01

    Mass loss from the Greenland and Antarctic ice sheets has increased rapidly since the mid-1990s. Their combined loss now accounts for about one-third of global sea level rise. In Greenland, a growing body of evidence points to the marine margins of these glaciers as the region from which this dynamic response originated. Similarly, ice streams in West Antarctica that feed vast floating ice shelves have exhibited large decadal changes. We review observational evidence and present physical mechanisms that might explain the observed changes, in particular in the context of ice sheet-ocean interactions. Processes involve cover 7 orders of magnitudes of scales, ranging from mm boundary-layer processes to basin-scale coupled atmosphere-ocean variability. We discuss observational needs to fill the gap in our mechanistic understanding.

  8. 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...

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

    Directory of Open Access Journals (Sweden)

    Adam D Hughes

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

  10. 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

  11. 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.

  12. 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

  13. 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; Wang, Tifeng; Liu, Nana; Dupont, Sam; Beardall, John; Boyd, Philip W; Riebesell, Ulf; Gao, Kunshan

    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.

  14. Interaction between High-Level and Low-Level Image Analysis for Semantic Video Object Extraction

    Directory of Open Access Journals (Sweden)

    Andrea Cavallaro

    2004-06-01

    Full Text Available The task of extracting a semantic video object is split into two subproblems, namely, object segmentation and region segmentation. Object segmentation relies on a priori assumptions, whereas region segmentation is data-driven and can be solved in an automatic manner. These two subproblems are not mutually independent, and they can benefit from interactions with each other. In this paper, a framework for such interaction is formulated. This representation scheme based on region segmentation and semantic segmentation is compatible with the view that image analysis and scene understanding problems can be decomposed into low-level and high-level tasks. Low-level tasks pertain to region-oriented processing, whereas the high-level tasks are closely related to object-level processing. This approach emulates the human visual system: what one “sees” in a scene depends on the scene itself (region segmentation as well as on the cognitive task (semantic segmentation at hand. The higher-level segmentation results in a partition corresponding to semantic video objects. Semantic video objects do not usually have invariant physical properties and the definition depends on the application. Hence, the definition incorporates complex domain-specific knowledge and is not easy to generalize. For the specific implementation used in this paper, motion is used as a clue to semantic information. In this framework, an automatic algorithm is presented for computing the semantic partition based on color change detection. The change detection strategy is designed to be immune to the sensor noise and local illumination variations. The lower-level segmentation identifies the partition corresponding to perceptually uniform regions. These regions are derived by clustering in an N-dimensional feature space, composed of static as well as dynamic image attributes. We propose an interaction mechanism between the semantic and the region partitions which allows to

  15. Modelling the Interaction Levels in HCI Using an Intelligent Hybrid System with Interactive Agents: A Case Study of an Interactive Museum Exhibition Module in Mexico

    Directory of Open Access Journals (Sweden)

    Ricardo Rosales

    2018-03-01

    Full Text Available Technology has become a necessity in our everyday lives and essential for completing activities we typically take for granted; technologies can assist us by completing set tasks or achieving desired goals with optimal affect and in the most efficient way, thereby improving our interactive experiences. This paper presents research that explores the representation of user interaction levels using an intelligent hybrid system approach with agents. We evaluate interaction levels of Human-Computer Interaction (HCI with the aim of enhancing user experiences. We consider the description of interaction levels using an intelligent hybrid system to provide a decision-making system to an agent that evaluates interaction levels when using interactive modules of a museum exhibition. The agents represent a high-level abstraction of the system, where communication takes place between the user, the exhibition and the environment. In this paper, we provide a means to measure the interaction levels and natural behaviour of users, based on museum user-exhibition interaction. We consider that, by analysing user interaction in a museum, we can help to design better ways to interact with exhibition modules according to the properties and behaviour of the users. An interaction-evaluator agent is proposed to achieve the most suitable representation of the interaction levels with the aim of improving user interactions to offer the most appropriate directions, services, content and information, thereby improving the quality of interaction experienced between the user-agent and exhibition-agent.

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

    Energy Technology Data Exchange (ETDEWEB)

    McBrayer, J F; Reichle, D E

    1971-01-01

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

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

    Science.gov (United States)

    Denda, Anneke; Stefanowitsch, Benjamin; Christiansen, Bernd

    2017-12-01

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

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

    Science.gov (United States)

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

    2017-05-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  20. Two interacting spins in external fields. Four-level systems

    Energy Technology Data Exchange (ETDEWEB)

    Bagrov, V.G.; Baldiotti, M.C.; Gitman, D.M. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil); Levin, A.D. [Dexter Research Center (United States)

    2007-04-15

    In the present article, we consider the so-called two-spin equation that describes four-level quantum systems. Recently, these systems attract attention due to their relation to the problem of quantum computation. We study general properties of the two-spin equation and show that the problem for certain external backgrounds can be identified with the problem of one spin in an appropriate background. This allows one to generate a number of exact solutions for two-spin equations on the basis of already known exact solutions of the one-spin equation. Besides, we present some exact solutions for the two-spin equation with an external background different for each spin but having the same direction. We study the eigenvalue problem for a time-independent spin interaction and a time-independent external background. A possible analogue of the Rabi problem for the two-spin equation is defined. We present its exact solution and demonstrate the existence of magnetic resonances in two specific frequencies, one of them coinciding with the Rabi frequency, and the other depending on the rotating field magnitude. The resonance that corresponds to the second frequency is suppressed with respect to the first one. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  1. Trophic ulcers in the carpal tunnel syndrome

    Directory of Open Access Journals (Sweden)

    Abelardo Q.-C. Araújo

    1993-09-01

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

  2. Interactions between the Isolated-Interactive Elements Effect and Levels of Learner Expertise: Experimental Evidence from an Accountancy Class

    Science.gov (United States)

    Blayney, Paul; Kalyuga, Slava; Sweller, John

    2010-01-01

    This study investigated interactions between the isolated-interactive elements effect and levels of learner expertise with first year undergraduate university accounting students. The isolated-interactive elements effect occurs when learning is facilitated by initially presenting elements of information sequentially in an isolated form rather than…

  3. Explaining Interaction Effects within and across Levels of Analysis

    DEFF Research Database (Denmark)

    Andersson, Ulf; Cuervo-Cazurra, Alvaro; Nielsen, Bo Bernhard

    2014-01-01

    Many manuscripts submitted to the Journal of International Business Studies propose an interaction effect in their models in an effort to explain the complexity and contingency of relationships across borders. In this article, we provide guidance on how best to explain the interaction effects...

  4. Age-Related Changes in Binaural Interaction at Brainstem Level

    NARCIS (Netherlands)

    Yper, L.N. Van; Vermeire, K.; Vel, E.F. De; Beynon, A.J.; Dhooge, I.J.

    2016-01-01

    OBJECTIVES: Age-related hearing loss hampers the ability to understand speech in adverse listening conditions. This is attributed to a complex interaction of changes in the peripheral and central auditory system. One aspect that may deteriorate across the lifespan is binaural interaction. The

  5. Complex interactions among host pines and fungi vectored by an invasive bark beetle

    Science.gov (United States)

    Min Lu; Michael J. Wingfield; Nancy E. Gillette; Sylvia R. Mori; Jian-Hua Sun

    2010-01-01

    Recent studies have investigated the relationships between pairs or groups of exotic species to illustrate invasive mechanisms, but most have focused on interactions at a single trophic level.Here, we conducted pathogenicity tests, analyses of host volatiles and fungal growth tests to elucidate an intricate network of interactions between the host...

  6. Interactions between Levels of Attention Ability and Levels of Bilingualism in Children’s Executive Functioning

    Science.gov (United States)

    Sorge, Geoff B.; Toplak, Maggie E.; Bialystok, Ellen

    2016-01-01

    Attention difficulty is associated with poor performance on executive functioning (EF) tasks, yet EF is enhanced in bilingual children. However, no research to date has investigated the possible interaction between bilingualism and attention ability in children to determine the consequences for EF when both are present. We assessed a sample of typically-developing children who were 8- to 11-years old for their ability in attention control and level of bilingualism on the basis of questionnaires completed by parents and teachers. Children performed three tasks requiring aspects of EF: stop signal task (inhibition), flanker task (interference control), and frogs matrices task (spatial working memory). Results from hierarchical regressions confirmed that both attention ability and bilingualism contributed to performance on the EF tasks. Where interaction effects were significant, they showed that attention ability was a stronger predictor for an inhibition task, namely stop signal, and bilingualism a stronger predictor for an interference task, namely flanker. Furthermore, these results allow us to discuss the relation between EF and attention ability. PMID:26875024

  7. 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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2018-01-01

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

  10. 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.

  11. Plant interactions with multiple insect herbivores: from community to genes

    NARCIS (Netherlands)

    Stam, J.M.; Kroes, A.; Li, Y.; Gols, R.; Loon, van J.J.A.; Poelman, E.H.; Dicke, M.

    2014-01-01

    Every plant is a member of a complex insect community that consists of tens to hundreds of species that belong to different trophic levels. The dynamics of this community are critically influenced by the plant, which mediates interactions between community members that can occur on the plant

  12. A two-level solvable model involving competing pairing interactions

    International Nuclear Information System (INIS)

    Dussel, G.G.; Maqueda, E.E.; Perazzo, R.P.J.; Evans, J.A.

    1986-01-01

    A model is considered consisting of nucleons moving in two non-degenerate l-shells and interacting through two pairing residual interactions with (S, T) = (1, 0) and (0, 1). These, together with the single particle hamiltonian induce mutually destructive correlations, giving rise to various collective pictures that can be discussed as representing a two-dimensional space of phases. The model is solved exactly using an O(8)xO(8) group theoretical classification scheme. The transfer of correlated pairs and quartets is also discussed. (orig.)

  13. How Levels of Interactivity in Tutorials Affect Students' Learning of Modeling Transportation Problems in a Spreadsheet

    Science.gov (United States)

    Seal, Kala Chand; Przasnyski, Zbigniew H.; Leon, Linda A.

    2010-01-01

    Do students learn to model OR/MS problems better by using computer-based interactive tutorials and, if so, does increased interactivity in the tutorials lead to better learning? In order to determine the effect of different levels of interactivity on student learning, we used screen capture technology to design interactive support materials for…

  14. 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

  15. Genetic and genomic interactions of animals with different ploidy levels.

    Science.gov (United States)

    Bogart, J P; Bi, K

    2013-01-01

    Polyploid animals have independently evolved from diploids in diverse taxa across the tree of life. We review a few polyploid animal species or biotypes where recently developed molecular and cytogenetic methods have significantly improved our understanding of their genetics, reproduction and evolution. Mitochondrial sequences that target the maternal ancestor of a polyploid show that polyploids may have single (e.g. unisexual salamanders in the genus Ambystoma) or multiple (e.g. parthenogenetic polyploid lizards in the genus Aspidoscelis) origins. Microsatellites are nuclear markers that can be used to analyze genetic recombinations, reproductive modes (e.g. Ambystoma) and recombination events (e.g. polyploid frogs such as Pelophylax esculentus). Hom(e)ologous chromosomes and rare intergenomic exchanges in allopolyploids have been distinguished by applying genome-specific fluorescent probes to chromosome spreads. Polyploids arise, and are maintained, through perturbations of the 'normal' meiotic program that would include pre-meiotic chromosome replication and genomic integrity of homologs. When possible, asexual, unisexual and bisexual polyploid species or biotypes interact with diploid relatives, and genes are passed from diploid to polyploid gene pools, which increase genetic diversity and ultimately evolutionary flexibility in the polyploid. When diploid relatives do not exist, polyploids can interact with another polyploid (e.g. species of African Clawed Frogs in the genus Xenopus). Some polyploid fish (e.g. salmonids) and frogs (Xenopus) represent independent lineages whose ancestors experienced whole genome duplication events. Some tetraploid frogs (P. esculentus) and fish (Squaliusalburnoides) may be in the process of becoming independent species, but diploid and triploid forms of these 'species' continue to genetically interact with the comparatively few tetraploid populations. Genetic and genomic interaction between polyploids and diploids is a complex

  16. Interactive policy processes: a challenge for street-level bureaucrats

    DEFF Research Database (Denmark)

    Agger, Annika; Damgaard, Bodil

    2018-01-01

    public managers are expected to work closely and directly with affected stakeholders in order to solve cross-cutting ‘wicked problems’. More interactive and participative collaborative policy processes increasingly require public managers to move from back-office work to front-office work, in effect...... in order to secure transparent processes that keep the rule of law and that support well-functioning local communities – or in more broad terms: skills needed to secure democracy and economic efficiency....

  17. Interaction of cementitious materials with high-level waste

    International Nuclear Information System (INIS)

    Lemmens, Karel; Cachoir, Christelle; Ferrand, Karine; Mennecart, Thierry; Gielen, Ben; Vercauter, Regina

    2012-01-01

    Document available in abstract form only: Since a few years, the Belgian agency for radioactive waste (ONDRAF/NIRAS) has selected the Supercontainer design with an Ordinary Portland Cement (OPC) buffer as the reference design for geological disposal of High-Level Waste (HLW) and Spent Fuel (SF) in the Boom Clay formation. The Boom Clay beneath the Mol-Dessel nuclear zone is a reference methodological site for supporting R and D. Compared to the previous bentonite based reference design, described in detail in the final SAFIR 2 report, the supercontainer will provide a highly alkaline chemical environment allowing the passivation of the surface of the overpack and the inhibition of its corrosion. The Supercontainer will contribute to the containment of radionuclides, but it will also have an effect on the retardation of radionuclide release from the waste and it will retard the migration of the released radionuclides. In the Supercontainer design, the canisters of HLW or SF will be enclosed by a 30 mm thick carbon steel overpack and a concrete buffer about 700 mm thick. The overpack will prevent contact with the (cementitious) pore water during the thermal phase. On the other hand, once the overpack will be locally perforated, the high pH of the incoming water may have an impact on the lifetime of the vitrified waste or spent fuel. The behaviour of these waste forms in disposal conditions has been studied for several decades, but the vast majority of published data is related to the interaction with backfill or host rock materials at near-neutral pH. Very few studies have been reported for alkaline media, at pH >11. Hence, a research programme including new experiments, was started at the Belgian Nuclear Research Centre (SCK.CEN) and at INE (FZK) to assess the rate at which the radionuclides are released by the vitrified waste and spent fuel in such an environment. The presence of concrete will have an impact on the behaviour of the vitrified HLW and spent fuel. For

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-02-15

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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

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

    International Nuclear Information System (INIS)

    Simon, Olivier; Garnier-Laplace, Jacqueline

    2005-01-01

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

  1. Echinococcus-Host Interactions at Cellular and Molecular Levels.

    Science.gov (United States)

    Brehm, K; Koziol, U

    2017-01-01

    The potentially lethal zoonotic diseases alveolar and cystic echinococcosis are caused by the metacestode larval stages of the tapeworms Echinococcus multilocularis and Echinococcus granulosus, respectively. In both cases, metacestode growth and proliferation occurs within the inner organs of mammalian hosts, which is associated with complex molecular host-parasite interactions that regulate nutrient uptake by the parasite as well as metacestode persistence and development. Using in vitro cultivation systems for parasite larvae, and informed by recently released, comprehensive genome and transcriptome data for both parasites, these molecular host-parasite interactions have been subject to significant research during recent years. In this review, we discuss progress in this field, with emphasis on parasite development and proliferation. We review host-parasite interaction mechanisms that occur early during an infection, when the invading oncosphere stage undergoes a metamorphosis towards the metacestode, and outline the decisive role of parasite stem cells during this process. We also discuss special features of metacestode morphology, and how this parasite stage takes up nutrients from the host, utilizing newly evolved or expanded gene families. We comprehensively review mechanisms of host-parasite cross-communication via evolutionarily conserved signalling systems and how the parasite signalling systems might be exploited for the development of novel chemotherapeutics. Finally, we point to an urgent need for the development of functional genomic techniques in this parasite, which will be imperative for hypothesis-driven analyses into Echinococcus stem cell biology, developmental mechanisms and immunomodulatory activities, which are all highly relevant for the development of anti-infective measures. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Missing lynx and trophic cascades in food webs: A reply to Ripple et al.

    Science.gov (United States)

    John R. Squires; Nicholas J. DeCesare; Mark Hebblewhite; Joel Berger

    2012-01-01

    Ripple et al. (2011) proposed a hypothesis that the recovery of gray wolves (Canis lupus) may positively affect the viability of threatened Canada lynx (Lynx canadensis) populations in the contiguous United States through indirect species interactions. Ripple et al. (2011) proposed 2 key trophic linkages connecting wolf restoration with lynx recovery. First, recovering...

  3. 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

  4. 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

  5. Modeling lake trophic state: a random forest approach

    Science.gov (United States)

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

  6. Modelling emergent trophic strategies in plankton

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  7. 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.

  8. 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.

  9. Micro-Level Interactions in Business-Nonprofit Partnerships

    NARCIS (Netherlands)

    Vock, M.; van Dolen, W.; Kolk, A.

    2014-01-01

    While most research on business-nonprofit partnerships has focused on macro and meso perspectives, this article pays attention to the micro level. Drawing on various theoretical perspectives from both marketing and management, this study conceptually relates the outcomes of active employee

  10. Micro-Level Interactions in Business-Nonprofit Partnerships

    NARCIS (Netherlands)

    M. Vock (Marlene); W.M. van Dolen (Willemijn); A. Kolk (Ans)

    2013-01-01

    textabstractWhile most research on business-nonprofit partnerships has focused on macro and meso perspectives, this paper pays attention to the micro level. Drawing on various theoretical perspectives from both marketing and management, we conceptually relate the outcomes of active employee

  11. Interaction between electrons and tunneling levels in metallic glasses

    International Nuclear Information System (INIS)

    Black, J.L.; Gyorffy, B.L.

    1978-01-01

    A simple model in which the conduction electrons of a metallic glass experience a local time-dependent potential due to two-level tunneling states is considered. The model exhibits interesting divergent behavior which is quite different from that predicted by an earlier ''s-d Kondo'' model

  12. Interactive effect of dietary protein level and zilpaterol hydrochloride ...

    African Journals Online (AJOL)

    Bonsmara type steers were used to determine the effect of dietary zilpaterol hydrochloride (ZH) in combination with different dietary crude protein (CP) levels (100, 120 and 140 g CP/kg) on growth performance and meat quality. Treatment groups (T) consisted of 12 steers each. T1 – 100 g CP/kg + 0.15 mg ZH/kg live weight ...

  13. Trophic structure in the Gulf of Lions marine ecosystem (north-western Mediterranean Sea) and fishing impacts

    Science.gov (United States)

    Bănaru, D.; Mellon-Duval, C.; Roos, D.; Bigot, J.-L.; Souplet, A.; Jadaud, A.; Beaubrun, P.; Fromentin, J.-M.

    2013-02-01

    The Gulf of Lions ecosystem was described using the Ecopath mass-balance model to characterise its structure and functioning and to examine the effects of the multispecific fisheries operating in this area. The model is composed of 40 compartments, including 1 group of seabirds, 2 groups of cetaceans, 18 groups of fish, 12 groups of invertebrates, 5 groups of primary producers, detritus and discards. Input data were based on several recurrent scientific surveys, two alternative datasets for fishing data, stock assessment outputs, stomach content analyses and published information. Results showed that the functional groups were organised into five trophic levels with the highest one represented by dolphins, anglerfish, Atlantic bluefin tuna, European hake and European conger. European pilchard and European anchovy dominated in terms of fish biomass and catch. Other fish with high biomass such as Atlantic mackerel and blue whiting were highly important in the food web. Seabirds, dolphins and cuttlefish-squids represented keystone species. Important coupled pelagic-demersal-benthic interactions were described. The 7 different fisheries analysed were operating at mean trophic levels situated between 2.6 for small artisanal boats, and 4.1 for purse seines (> 24 m) targeting large pelagic fish, indicating an intensively exploited ecosystem. Large trawlers (24-40 m) had the highest impact on most of the groups considered; while purse seines (12-24 m) targeting small pelagic fish had the lowest impact. Preliminary results highlighted the importance of data sources for further ecosystem and fisheries analyses and management scenarios.

  14. Soil-structure interaction effects on high level waste tanks

    International Nuclear Information System (INIS)

    Miller, C.A.; Costantino, C.J.; Heymsfeld, E.

    1991-01-01

    High Level Waste Tanks consist of steel tanks located in concrete vaults which are usually completely embedded in the soil. Many of these tanks are old and were designed to seismic standards which are not compatible with current requirements. The objective if this paper is to develop simple methods of modeling SSI effects for such structures and to obtain solutions for a range of parameters that can be used to identify significant aspects of the problem

  15. 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.

  16. An exploration in kitchen blender interactions aimed at designing for high levels of engagement

    NARCIS (Netherlands)

    van Rheden, V.; Hengeveld, B.J.

    2015-01-01

    This paper illustrates three novel kitchen blender interactions aimed at bringing about a higher level of engagement with interactive products, as a response to current, seemingly un-engaging interactions. We describe our starting points and approach after which we present the designed blender

  17. From the epipelagic zone to the abyss: Trophic structure at two seamounts in the subtropical and tropical Eastern Atlantic - Part II Benthopelagic fishes

    Science.gov (United States)

    Denda, Anneke; Stefanowitsch, Benjamin; Christiansen, Bernd

    2017-12-01

    Specific mechanisms, driving trophic interactions between seamount associated fishes and the pelagic community may be highly variable in different seamount systems. This study investigated the trophic structure and the main prey of benthopelagic fishes from the summit and slope regions of Ampère and Senghor, two shallow seamounts in the subtropical and tropical NE Atlantic, and the adjacent deep-sea plains. For the identification of food sources and nutritional links to the pelagic realm a combination of stomach content and stable isotope ratio (δ13C and δ15N) analyses was used. δ13C ranged from -22.2‰ to -15.4‰ and δ15N covered a total range of 8.0-15.9‰. Feeding types of fish species comprised mainly zooplanktivores and mixed feeders, but also benthivores, piscivores, and predator-scavengers. Based on epipelagic particulate organic matter, they occupied trophic positions between the 2nd and 4th trophic level. Differences in stomach contents and stable isotope signatures indicate a resource partitioning among the benthopelagic fish fauna through distinct habitat choice, vertical feeding positions and prey selection. Topographic trapping of vertically migrating zooplankton on the summit seemed to be of minor importance for food supply of the resident near-bottom fishes, rather horizontal current-driven advection of the planktonic prey was assumed as major factor. Vertically migrating micronekton and mesopelagic fishes show up as key players within the food webs at Ampère and Senghor Seamounts and the adjacent deep-sea plains.

  18. 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.

  19. 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.

  20. 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.

  1. Invisible trophic links? Quantifying the importance of non-standard food sources for key intertidal avian predators in the Eastern Atlantic

    NARCIS (Netherlands)

    Lourenço, P.M.; Catry, T.; Lopes, R.J.; Piersma, T.; Granadeiro, J.P.

    2017-01-01

    Coastal wetlands are heterogeneous systems with multiple inputs and complex interactionswithin local food webs. Interpreting such complexity is limited by incomplete knowledgeof trophic interactions among organisms. Although widely recognized as secondary consumersand predators of intertidal

  2. Reconstruction of trophic pathways between plankton and the North Iberian sardine (Sardina pilchardus using stable isotopes

    Directory of Open Access Journals (Sweden)

    Antonio Bode

    2004-03-01

    Full Text Available Feeding on phyto- and zooplankton by juvenile (< 1 year old and adult sardines (Sardina pilchardus was inferred from analyses of natural abundance of stable carbon and nitrogen isotopes in samples from the northwestern Iberian Peninsula (Spain collected at the beginning of the upwelling season and peak spawning period of sardine. Plankton samples were fractionated through nets of 20, 200, 500, 1000 and 2000 ?m mesh-size and the muscle protein of individual sardines was isolated before isotopic determinations. Up to six planktonic components and two sardine feeding types were identified from the modes in the frequency distributions of isotope abundance values. Also, the most probable pathways for carbon and nitrogen flows between compartments were analysed. The resulting food web revealed a relatively large degree of omnivory, both in plankton and sardine components, which confirms that complex trophic interactions could also occur in pelagic upwelling ecosystems. Young sardines had isotope abundance values clustered around a single mode in the frequency distribution, while adult sardines displayed two main modes. These modes are interpreted as representative of two extreme feeding types: one related to the individual capture of zooplankton prey and the other to unselective filter-feeding. Although both types of feeding could include micro- (20-200 ?m and mesozooplankton (200-2000 ?m prey, phytoplankton appears to be ingested mainly by filter-feeding. However, even adult sardines must be mainly zoophagous to achieve the observed isotopic abundance values, taking into account current assumptions on stable isotope enrichment through trophic levels. From the differences in the resulting pathways using either carbon or nitrogen isotopes, we interpreted that sardines acquire most of the protein nitrogen from zooplankton while a substantial fraction of their carbon would derive from phytoplankton. These interpretations agree with the information

  3. 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.

  4. 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.

  5. 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.

  6. Interactions between Levels of Attention Ability and Levels of Bilingualism in Children's Executive Functioning

    Science.gov (United States)

    Sorge, Geoff B.; Toplak, Maggie E.; Bialystok, Ellen

    2017-01-01

    Attention difficulty is associated with poor performance on executive functioning (EF) tasks, yet EF is enhanced in bilingual children. However, no research to date has investigated the possible interaction between bilingualism and attention ability in children to determine the consequences for EF when both are present. We assessed a sample of…

  7. 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

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

    Science.gov (United States)

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

    2015-03-04

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

  9. 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.

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

    Directory of Open Access Journals (Sweden)

    Teresa Korniłłowicz

    2014-08-01

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

  11. Trophic 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).

  12. Multi-level learning: improving the prediction of protein, domain and residue interactions by allowing information flow between levels

    Directory of Open Access Journals (Sweden)

    McDermott Drew

    2009-08-01

    Full Text Available Abstract Background Proteins interact through specific binding interfaces that contain many residues in domains. Protein interactions thus occur on three different levels of a concept hierarchy: whole-proteins, domains, and residues. Each level offers a distinct and complementary set of features for computationally predicting interactions, including functional genomic features of whole proteins, evolutionary features of domain families and physical-chemical features of individual residues. The predictions at each level could benefit from using the features at all three levels. However, it is not trivial as the features are provided at different granularity. Results To link up the predictions at the three levels, we propose a multi-level machine-learning framework that allows for explicit information flow between the levels. We demonstrate, using representative yeast interaction networks, that our algorithm is able to utilize complementary feature sets to make more accurate predictions at the three levels than when the three problems are approached independently. To facilitate application of our multi-level learning framework, we discuss three key aspects of multi-level learning and the corresponding design choices that we have made in the implementation of a concrete learning algorithm. 1 Architecture of information flow: we show the greater flexibility of bidirectional flow over independent levels and unidirectional flow; 2 Coupling mechanism of the different levels: We show how this can be accomplished via augmenting the training sets at each level, and discuss the prevention of error propagation between different levels by means of soft coupling; 3 Sparseness of data: We show that the multi-level framework compounds data sparsity issues, and discuss how this can be dealt with by building local models in information-rich parts of the data. Our proof-of-concept learning algorithm demonstrates the advantage of combining levels, and opens up

  13. 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

  14. Trophic transfer of differently functionalized zinc oxide nanoparticles from crustaceans (Daphnia magna) to zebrafish (Danio rerio)

    DEFF Research Database (Denmark)

    Skjolding, Lars Michael; Winther-Nielsen, M.; Baun, Anders

    2014-01-01

    ) higher than toxic levels reported for zinc in D. magna. Consequently, the zinc recovered in the animals was not solely due to soluble zinc, but agglomerates/aggregates of ZnO NP or ZnO-octyl NP contributed to the body burdens. The trophic transfer study showed uptake of both ZnO NP and ZnO-octyl NP...

  15. Trophic position of soil nematodes in boreal forests as indicated by stable isotope analysis

    Science.gov (United States)

    Kudrin, Alexey; Tsurikov, Sergey

    2016-04-01

    Despite the well-developed trophic classification of soil nematodes, their position in soil food webs is still little understood. Observed deviations from the typical feeding strategy indicate that a simplified trophic classification probably does not fully reflect actual trophic interactions. Furthermore, the extent and functional significance of nematodes as prey for other soil animals remains unknown. Stable isotope analysis (SIA) is powerful tool for investigating the structure of soil food webs, but its application to the study of soil nematodes has been limited to only a few studies. We used stable isotope analysis to gain a better understanding of trophic links of several groups of soil nematodes in two boreal forests on albeluvisol. We investigated four taxonomic groups of nematodes: Mononchida, Dorylaimida, Plectidae and Tylenchidae (mostly from the genus Filenchus), that according to the conventional trophic classification represent predators, omnivores, bacterivores and root-fungal feeders, respectively. To assess the trophic position of nematodes, we used a comparison against a set of reference species including herbivorous, saprophagous and predatory macro-invertebrates, oribatid and mesostigmatid mites, and collembolans. Our results suggest that trophic position of the investigated groups of soil nematodes generally corresponds to the conventional classification. All nematodes were enriched in 13C relative to Picea abies roots and litter, and mycorrhizal fungal mycelium. Root-fungal feeders Tylenchidae had δ15N values similar to those of earthworms, enchytraeids and Entomobrya collembolans, but slightly lower δ13C values. Bacterivorous Plectidae were either equal or enriched in 15N compared with saprophagous macroinvertebrates and most mesofauna species. Omnivorous Dorylaimida and predatory Mononchida were further enriched in 15N and their isotopic signature was similar to that of predatory arthropods. These data confirm a clear separation of

  16. Looplessness in networks is linked to trophic coherence.

    Science.gov (United States)

    Johnson, Samuel; Jones, Nick S

    2017-05-30

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

  17. Blood lead levels, iron metabolism gene polymorphisms and homocysteine: a gene-environment interaction study.

    Science.gov (United States)

    Kim, Kyoung-Nam; Lee, Mee-Ri; Lim, Youn-Hee; Hong, Yun-Chul

    2017-12-01

    Homocysteine has been causally associated with various adverse health outcomes. Evidence supporting the relationship between lead and homocysteine levels has been accumulating, but most prior studies have not focused on the interaction with genetic polymorphisms. From a community-based prospective cohort, we analysed 386 participants (aged 41-71 years) with information regarding blood lead and plasma homocysteine levels. Blood lead levels were measured between 2001 and 2003, and plasma homocysteine levels were measured in 2007. Interactions of lead levels with 42 genotyped single-nucleotide polymorphisms (SNPs) in five genes ( TF , HFE , CBS , BHMT and MTR ) were assessed via a 2-degree of freedom (df) joint test and a 1-df interaction test. In secondary analyses using imputation, we further assessed 58 imputed SNPs in the TF and MTHFR genes. Blood lead concentrations were positively associated with plasma homocysteine levels (p=0.0276). Six SNPs in the TF and MTR genes were screened using the 2-df joint test, and among them, three SNPs in the TF gene showed interactions with lead with respect to homocysteine levels through the 1-df interaction test (plead levels. Blood lead levels were positively associated with plasma homocysteine levels measured 4-6 years later, and three SNPs in the TF gene modified the association. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

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

    Directory of Open Access Journals (Sweden)

    David S. Boukal

    2014-04-01

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

  19. Interaction Networks: Generating High Level Hints Based on Network Community Clustering

    Science.gov (United States)

    Eagle, Michael; Johnson, Matthew; Barnes, Tiffany

    2012-01-01

    We introduce a novel data structure, the Interaction Network, for representing interaction-data from open problem solving environment tutors. We show how using network community detecting techniques are used to identify sub-goals in problems in a logic tutor. We then use those community structures to generate high level hints between sub-goals.…

  20. Two-Level Designs to Estimate All Main Effects and Two-Factor Interactions

    NARCIS (Netherlands)

    Eendebak, P.T.; Schoen, E.D.

    2017-01-01

    We study the design of two-level experiments with N runs and n factors large enough to estimate the interaction model, which contains all the main effects and all the two-factor interactions. Yet, an effect hierarchy assumption suggests that main effect estimation should be given more prominence

  1. Modal Analysis on Fluid-Structure Interaction of MW-Level Vertical Axis Wind Turbine Tower

    OpenAIRE

    Tan Jiqiu; Zhong Dingqing; Wang Qiong

    2014-01-01

    In order to avoid resonance problem of MW-level vertical axis wind turbine induced by wind, a flow field model of the MW-level vertical axis wind turbine is established by using the fluid flow control equations, calculate flow’s velocity and pressure of the MW-level vertical axis wind turbine and load onto tower’s before and after surface, study the Modal analysis of fluid-structure interaction of MW-level vertical axis wind turbine tower. The results show that fluid-structure interaction fie...

  2. Human hypocretin and melanin-concentrating hormone levels are linked to emotion and social interaction.

    Science.gov (United States)

    Blouin, Ashley M; Fried, Itzhak; Wilson, Charles L; Staba, Richard J; Behnke, Eric J; Lam, Hoa A; Maidment, Nigel T; Karlsson, Karl Æ; Lapierre, Jennifer L; Siegel, Jerome M

    2013-01-01

    The neurochemical changes underlying human emotions and social behaviour are largely unknown. Here we report on the changes in the levels of two hypothalamic neuropeptides, hypocretin-1 and melanin-concentrating hormone, measured in the human amygdala. We show that hypocretin-1 levels are maximal during positive emotion, social interaction and anger, behaviours that induce cataplexy in human narcoleptics. In contrast, melanin-concentrating hormone levels are minimal during social interaction, but are increased after eating. Both peptides are at minimal levels during periods of postoperative pain despite high levels of arousal. Melanin-concentrating hormone levels increase at sleep onset, consistent with a role in sleep induction, whereas hypocretin-1 levels increase at wake onset, consistent with a role in wake induction. Levels of these two peptides in humans are not simply linked to arousal, but rather to specific emotions and state transitions. Other arousal systems may be similarly emotionally specialized.

  3. Examining Ecological and Ecosystem Level Impacts of Aquatic Invasive Species in Lake Michigan Using An Ecosystem Productivity Model, LM-Eco

    Science.gov (United States)

    Ecological and ecosystem-level impacts of aquatic invasive species in Lake Michigan were examined using the Lake Michigan Ecosystem Model (LM-Eco). The LM-Eco model includes a detailed description of trophic levels and their interactions within the lower food web of Lake Michiga...

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, M.; Tjeerdema, R. [Univ. of California, Santa Cruz, CA (United States). Dept. of Chemistry and Biochemistry; Sowby, M. [California Dept. of Fish and Game, Sacramento, CA (United States)

    1995-12-31

    When crude oil is accidentally released into the ocean, it threatens many levels of marine life. Intervention, in the form of chemical dispersing agents, alters the normal behavior of petroleum hydrocarbons (PH) by increasing their functional water solubility and the extent of their exposure to sub-surface organisms. Dispersing agents may modify bioavailability as a result of altered interactions between dispersed PH droplets and organismal cell membranes.The objective of this research was to determine the impact of dispersing agents on PH bioavailability and trophic transfer in primary levels of a marine food chain. Uptake, bioaccumulation, depuration, and metabolic transformation of a model PH, {sup 14}C-naphthalene, were measured and compared for Prudhoe Bay Crude Oil (PBCO) dispersed with Corexit 9527 and undispersed preparations of the water-accommodated fractions (WAF) of PBCO at two salinities and temperatures. The model food chain consisted of Isochrysis galbana and Brachionus plicatilis. Direct aqueous exposure was compared with combined aqueous and dietary exposure. Fractionation and identification of metabolites was done by HPLC co-chromatography with analytical standards, and quantitation was done by liquid scintillation counting. GC-FID characterization of WAF and dispersed oil (DO) preparations shows higher concentrations of petroleum hydrocarbons and a greater number of individual constituents in the dispersed oil preparations.

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

    International Nuclear Information System (INIS)

    Wolfe, M.; Tjeerdema, R.

    1995-01-01

    When crude oil is accidentally released into the ocean, it threatens many levels of marine life. Intervention, in the form of chemical dispersing agents, alters the normal behavior of petroleum hydrocarbons (PH) by increasing their functional water solubility and the extent of their exposure to sub-surface organisms. Dispersing agents may modify bioavailability as a result of altered interactions between dispersed PH droplets and organismal cell membranes.The objective of this research was to determine the impact of dispersing agents on PH bioavailability and trophic transfer in primary levels of a marine food chain. Uptake, bioaccumulation, depuration, and metabolic transformation of a model PH, 14 C-naphthalene, were measured and compared for Prudhoe Bay Crude Oil (PBCO) dispersed with Corexit 9527 and undispersed preparations of the water-accommodated fractions (WAF) of PBCO at two salinities and temperatures. The model food chain consisted of Isochrysis galbana and Brachionus plicatilis. Direct aqueous exposure was compared with combined aqueous and dietary exposure. Fractionation and identification of metabolites was done by HPLC co-chromatography with analytical standards, and quantitation was done by liquid scintillation counting. GC-FID characterization of WAF and dispersed oil (DO) preparations shows higher concentrations of petroleum hydrocarbons and a greater number of individual constituents in the dispersed oil preparations

  7. Low-level radiation: biological interactions, risks, and benefits. A bibliography

    Energy Technology Data Exchange (ETDEWEB)

    None

    1978-09-01

    The bibliography contains 3294 references that were selected from the Department of Energy's data base (EDB). The subjects covered are lower-level radiation effects on man, environmental radiation, and other biological interactions of radiation that appear to be applicable to the low-level radiation problem.

  8. Litter mixture interactions at the level of plant functional types are additive.

    NARCIS (Netherlands)

    Hoorens, B.; Stroetenga, M.J.; Aerts, R.

    2010-01-01

    It is very difficult to estimate litter decomposition rates in natural ecosystems because litters of many species are mixed and idiosyncratic interactions occur among those litters. A way to tackle this problem is to investigate litter mixing effects not at the species level but at the level of

  9. Dynamic evolution of double Λ five-level atom interacting with one ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 89; Issue 6. Dynamic evolution ... Five-level atom; squeezing; collapse revivals. Abstract. In this paper, the model describing a double Λ five-level atom interacting with a single mode electromagnetic cavity field in the (off) non-resonate case is studied. We obtained the ...

  10. Low-level radiation: biological interactions, risks, and benefits. A bibliography

    International Nuclear Information System (INIS)

    1978-09-01

    The bibliography contains 3294 references that were selected from the Department of Energy's data base (EDB). The subjects covered are lower-level radiation effects on man, environmental radiation, and other biological interactions of radiation that appear to be applicable to the low-level radiation problem

  11. Potential trophic cascades triggered by the barred owl range expansion

    Science.gov (United States)

    Holm, Samantha R.; Noon, Barry R.; Wiens, David; Ripple, William J.

    2016-01-01

    Recently, the barred owl (Strix varia) has expanded its range into the Pacific Northwest of the United States resulting in pronounced effects on the demography and behavior of the northern spotted owl (S. occidentalis caurina). The range expansion has brought together historically allopatric species, creating the potential for significant changes in the avian predator community with possible cascading effects on food-web dynamics. The adverse effects of the barred owl on the behavior and demography of the northern spotted owl are well-documented, but little is known about the immediate and long-term effects changes in the predator community may have on native species composition and ecosystem processes. Based on northern spotted owl and barred owl selection for diet and habitat resources, there is a potential for trophic cascades within the region's predator and prey communities, differing responses by their shared and unique prey species, and possible direct and indirect effects on ecosystem processes. We explored the possible ecological consequences of the barred owl range expansion to wildlife communities of the Pacific Northwest based on the theoretical underpinnings of predator–prey relationships, interspecific competition, intraguild predation, and potential cascading trophic interactions. Negative effects on fitness of northern spotted owls because of interspecific competition with barred owls are strong selection forces that may contribute to the regional extinction of the northern spotted owl. In addition, we posit that shared prey species and those uniquely consumed by barred owls, along with other competing native predators, may experience changes in behavior, abundance, and distribution as a result of increased rates of predation by rapidly expanding populations of barred owls.

  12. The effect of water level in a prey-predator interactions: A nonlinear analysis study

    International Nuclear Information System (INIS)

    Chiboub Fellah, N.; Bouguima, S.M.; Moussaoui, A.

    2012-01-01

    Highlights: ► A new model describing the interaction between predator and prey in Parloup Lake. ► Existence of periodic solution is proved. ► Seasonal variation in water level is an important factor for persitence. - Abstract: Water level may influence local community dynamics. We examine how seasonal variations in water level affect the outcome of prey-predator interactions in Parloup Lake in the south of France. We propose a new model to describe the annual cycle of persistence by using continuation theorem of coincidence degree.

  13. Subliminally and consciously induced cognitive conflicts interact at several processing levels.

    Science.gov (United States)

    Stock, Ann-Kathrin; Friedrich, Julia; Beste, Christian

    2016-12-01

    Controlled behavior is susceptible to conflicts that can emerge from subliminal or consciously processed information. While research suggests that both sources of conflicting information may interact in their modulation of controlled behavior, it has remained unclear which cognitive sub-processes involved in controlled behavior are affected by this interaction; i.e., at which processing level subliminally and consciously induced response conflicts interact in modulating controlled behavior. Moreover, we investigated whether this interaction of subliminally and consciously induced response conflicts was due to a nexus between the two types of conflict like a common cognitive process or factor. For this, n = 38 healthy young subjects completed a paradigm which combines subliminal primes and consciously perceived flankers while an electroencephalography (EEG) was recorded. We show that the interaction of subliminal and conscious sources of conflict is not restricted to the response selection level (N2) but can already be shown at the earliest stages of perceptual and attentional processing (P1). While the degree of early attentional processing of subliminal information seems to depend on the absence of consciously perceived response conflicts, conflicts during the stage of response selection may be either reduced or enhanced by subliminal priming. Moreover, the results showed that even though the two different sources of conflict interact at the response selection level, they clearly originate from two distinct processes that interact before they detrimentally affect cognitive control. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Direct observation of children's preferences and activity levels during interactive and online electronic games.

    Science.gov (United States)

    Sit, Cindy H P; Lam, Jessica W K; McKenzie, Thomas L

    2010-07-01

    Interactive electronic games have recently been popularized and are believed to help promote children's physical activity (PA). The purpose of the study was to examine preferences and PA levels during interactive and online electronic games among overweight and nonoverweight boys and girls. Using a modification of the SOFIT, we systematically observed 70 Hong Kong Chinese children (35 boys, 35 girls; 50 nonoverweight, 20 overweight), age 9 to 12 years, during 2 60-minute recreation sessions and recorded their game mode choices and PA levels. During Session One children could play either an interactive or an online electronic bowling game and during Session Two they could play an interactive or an online electronic running game. Children chose to play the games during 94% of session time and split this time between interactive (52%) and online (48%) versions. They engaged in significantly more moderate-to-vigorous physical activity (MVPA) during interactive games than their online electronic versions (70% vs. 2% of game time). Boys and nonoverweight children expended relatively more energy during the interactive games than girls and overweight children, respectively. New-generation interactive games can facilitate physical activity in children, and given the opportunity children may select them over sedentary versions.

  15. More Precise Estimation of Lower-Level Interaction Effects in Multilevel Models.

    Science.gov (United States)

    Loeys, Tom; Josephy, Haeike; Dewitte, Marieke

    2018-01-01

    In hierarchical data, the effect of a lower-level predictor on a lower-level outcome may often be confounded by an (un)measured upper-level factor. When such confounding is left unaddressed, the effect of the lower-level predictor is estimated with bias. Separating this effect into a within- and between-component removes such bias in a linear random intercept model under a specific set of assumptions for the confounder. When the effect of the lower-level predictor is additionally moderated by another lower-level predictor, an interaction between both lower-level predictors is included into the model. To address unmeasured upper-level confounding, this interaction term ought to be decomposed into a within- and between-component as well. This can be achieved by first multiplying both predictors and centering that product term next, or vice versa. We show that while both approaches, on average, yield the same estimates of the interaction effect in linear models, the former decomposition is much more precise and robust against misspecification of the effects of cross-level and upper-level terms, compared to the latter.

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Mauro Galetti

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

  18. Diet Composition and Trophic Ecology of Northeast Pacific Ocean Sharks.

    Science.gov (United States)

    Bizzarro, Joseph J; Carlisle, Aaron B; Smith, Wade D; Cortés, Enric

    Although there is a general perception of sharks as large pelagic, apex predators, most sharks are smaller, meso- and upper-trophic level predators that are associated with the seafloor. Among 73 shark species documented in the eastern North Pacific (ENP), less than half reach maximum lengths >200cm, and 78% occur in demersal or benthic regions of the continental shelf or slope. Most small (≤200cm) species (e.g., houndsharks) and demersal, nearshore juveniles of larger species (e.g., requiem sharks) consume small teleosts and decapod crustaceans, whereas large species in pelagic coastal and oceanic environments feed on large teleosts and squids. Several large, pelagic apex predator species occur in the ENP, but the largest species (i.e., Basking Shark, Whale Shark) consume zooplankton or small nekton. Size-based dietary variability is substantial for many species, and segregation of juvenile and adult foraging habitats also is common (e.g., Horn Shark, Shortfin Mako). Temporal dietary differences are most pronounced for temperate, nearshore species with wide size ranges, and least pronounced for smaller species in extreme latitudes and deep-water regions. Sympatric sharks often occupy various trophic positions, with resource overlap differing by space and time and some sharks serving as prey to other species. Most coastal species remain in the same general region over time and feed opportunistically on variable prey inputs (e.g., season migrations, spawning, or recruitment events), whereas pelagic, oceanic species actively seek hot spots of prey abundance that are spatiotemporally variable. The influence of sharks on ecosystem structure and regulation has been downplayed compared to that of large teleosts species with higher per capita consumption rates (e.g., tunas, billfishes). However, sharks also exert indirect influences on prey populations by causing behavioural changes that may result in restricted ranges and reduced fitness. Except for food web modelling

  19. 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...

  20. 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, ...

  1. 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

  2. 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.

  3. Investigation of the molecular level interactions between mucins and food proteins: Spectroscopic, tribological and rheological studies

    OpenAIRE

    Celebioglu, Hilal Yilmaz; Chronakis, Ioannis S.; Lee, Seunghwan; Guðjónsdóttir, María

    2017-01-01

    The thesis investigated the structure and molecular-level interaction of β-lactoglobulin (BLG) and mucins, representing major components of the dairy products and saliva/digestion systems, respectively. Mucins are long glycoprotein molecules responsible for the gel nature of the mucous layer covers epithelial surfaces throughout the body. A literature review of the interactions of different mucin types and saliva mucins with several food proteins and food protein emulsions, as well as their f...

  4. Multi-level machine learning prediction of protein–protein interactions in Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Julian Zubek

    2015-07-01

    Full Text Available Accurate identification of protein–protein interactions (PPI is the key step in understanding proteins’ biological functions, which are typically context-dependent. Many existing PPI predictors rely on aggregated features from protein sequences, however only a few methods exploit local information about specific residue contacts. In this work we present a two-stage machine learning approach for prediction of protein–protein interactions. We start with the carefully filtered data on protein complexes available for Saccharomyces cerevisiae in the Protein Data Bank (PDB database. First, we build linear descriptions of interacting and non-interacting sequence segment pairs based on their inter-residue distances. Secondly, we train machine learning classifiers to predict binary segment interactions for any two short sequence fragments. The final prediction of the protein–protein interaction is done using the 2D matrix representation of all-against-all possible interacting sequence segments of both analysed proteins. The level-I predictor achieves 0.88 AUC for micro-scale, i.e., residue-level prediction. The level-II predictor improves the results further by a more complex learning paradigm. We perform 30-fold macro-scale, i.e., protein-level cross-validation experiment. The level-II predictor using PSIPRED-predicted secondary structure reaches 0.70 precision, 0.68 recall, and 0.70 AUC, whereas other popular methods provide results below 0.6 threshold (recall, precision, AUC. Our results demonstrate that multi-scale sequence features aggregation procedure is able to improve the machine learning results by more than 10% as compared to other sequence representations. Prepared datasets and source code for our experimental pipeline are freely available for download from: http://zubekj.github.io/mlppi/ (open source Python implementation, OS independent.

  5. Interactive Approach for Multi-Level Multi-Objective Fractional Programming Problems with Fuzzy Parameters

    Directory of Open Access Journals (Sweden)

    M.S. Osman

    2018-03-01

    Full Text Available In this paper, an interactive approach for solving multi-level multi-objective fractional programming (ML-MOFP problems with fuzzy parameters is presented. The proposed interactive approach makes an extended work of Shi and Xia (1997. In the first phase, the numerical crisp model of the ML-MOFP problem has been developed at a confidence level without changing the fuzzy gist of the problem. Then, the linear model for the ML-MOFP problem is formulated. In the second phase, the interactive approach simplifies the linear multi-level multi-objective model by converting it into separate multi-objective programming problems. Also, each separate multi-objective programming problem of the linear model is solved by the ∊-constraint method and the concept of satisfactoriness. Finally, illustrative examples and comparisons with the previous approaches are utilized to evince the feasibility of the proposed approach.

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

    Directory of Open Access Journals (Sweden)

    Karine O. Bonato

    2018-03-01

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

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

    Directory of Open Access Journals (Sweden)

    Patricia Puerta

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  9. 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.

  10. 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

  11. Macrophytes shape trophic niche variation among generalist fishes

    Science.gov (United States)

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

    2017-01-01

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

  12. 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.

  13. Rotation gate for a three-level superconducting quantum interference device qubit with resonant interaction

    International Nuclear Information System (INIS)

    Yang, C.-P.; Han Siyuan

    2006-01-01

    We show a way to realize an arbitrary rotation gate in a three-level superconducting quantum interference device (SQUID) qubit using resonant interaction. In this approach, the two logical states of the qubit are represented by the two lowest levels of the SQUID and a higher-energy intermediate level is utilized for the gate manipulation. By considering spontaneous decay from the intermediate level during the gate operation, we present a formula for calculating average fidelity over all possible initial states. Finally, based on realistic system parameters, we show that an arbitrary rotation gate can be achieved with a high fidelity in a SQUID

  14. 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.

  15. 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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  17. 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;}

  18. Level crossings, excess times, and transient plasma–wall interactions in fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Theodorsen, A., E-mail: audun.theodorsen@uit.no; Garcia, O. E., E-mail: odd.erik.garcia@uit.no [Department of Physics and Technology, UiT The Arctic University of Norway, N-9037 Tromsø (Norway)

    2016-04-15

    Based on a stochastic model for intermittent fluctuations in the boundary region of magnetically confined plasmas, an expression for the level crossing rate is derived from the joint distribution of the process and its derivative. From this the average time spent by the process above a certain threshold level is obtained. This provides novel predictions of plasma–wall interactions due to transient transport events associated with a radial motion of blob-like structures in the scrape-off layer.

  19. Dynamics of a trapped two-level and three-level atom interacting with classical electromagnetic field

    International Nuclear Information System (INIS)

    Ray, Aditi

    2004-01-01

    The dynamics of a two-level atom driven by a single laser beam and three-level atom (Lambda configuration) irradiated by two laser beams are studied taking into account of the quantized center-of-mass motion of the atom. It is shown that the trapped atom system under appropriate resonance condition exhibits the large time-scale revivals when the index of the vibrational sideband responsible for the atomic electronic transition is greater than unity. The revival times are shown to be dependent on the initial number of vibrational excitations and the magnitude of the Lamb-Dicke parameter. The sub-Poissonian statistics in vibrational quantum number is observed at certain time intervals. The minimum time of interaction for which the squeezed states of motional quadrature are generated is found to be decreasing with the increase in the Lamb-Dicke parameter

  20. An In Vivo Characterization of Trophic Factor Production Following Neural Precursor Cell or Bone Marrow Stromal Cell Transplantation for Spinal Cord Injury

    Science.gov (United States)

    Hawryluk, Gregory W.J.; Mothe, Andrea; Wang, Jian; Wang, Shelly; Tator, Charles

    2012-01-01

    Cellular transplantation strategies for repairing the injured spinal cord have shown consistent benefit in preclinical models, and human clinical trials have begun. Interactions between transplanted cells and host tissue remain poorly understood. Trophic factor secretion is postulated a primary or supplementary mechanism of action for many transplanted cells, however, there is little direct evidence to support trophin production by transplanted cells in situ. In the present study, trophic factor expression was characterized in uninjured, injured-untreated, injured-treated with transplanted cells, and corresponding control tissue from the adult rat spinal cord. Candidate trophic factors were identified in a literature search, and primers were designed for these genes. We examined in vivo trophin expression in 3 paradigms involving transplantation of either brain or spinal cord-derived neural precursor cells (NPCs) or bone marrow stromal cells (BMSCs). Injury without further treatment led to a significant elevation of nerve growth factor (NGF), leukemia inhibitory factor (LIF), insulin-like growth factor-1 (IGF-1), and transforming growth factor-β1 (TGF-β1), and lower expression of vascular endothelial growth factor isoform A (VEGF-A) and platelet-derived growth factor-A (PDGF-A). Transplantation of NPCs led to modest changes in trophin expression, and the co-administration of intrathecal trophins resulted in significant elevation of the neurotrophins, glial-derived neurotrophic factor (GDNF), LIF, and basic fibroblast growth factor (bFGF). BMSCs transplantation upregulated NGF, LIF, and IGF-1. NPCs isolated after transplantation into the injured spinal cord expressed the neurotrophins, ciliary neurotrophic factor (CNTF), epidermal growth factor (EGF), and bFGF at higher levels than host cord. These data show that trophin expression in the spinal cord is influenced by injury and cell transplantation, particularly when combined with intrathecal trophin infusion

  1. Fatty acid biomarkers: validation of food web and trophic markers using C-13-labelled fatty acids in juvenile sandeel ( Ammodytes tobianus )

    DEFF Research Database (Denmark)

    Dalsgaard, Anne Johanne Tang; St. John, Michael

    2004-01-01

    A key issue in marine science is parameterizing trophic interactions in marine food webs, thereby developing an understanding of the importance of top-down and bottom-up controls on populations of key trophic players. This study validates the utility of fatty acid food web and trophic markers usi......), respectively. Lack of temporal trends in nonlabelled fatty acids confirmed the conservative incorporation of labelled fatty acids by the fish.......A key issue in marine science is parameterizing trophic interactions in marine food webs, thereby developing an understanding of the importance of top-down and bottom-up controls on populations of key trophic players. This study validates the utility of fatty acid food web and trophic markers using...... C-13-labelled fatty acids to verify the conservative incorporation of fatty acid tracers by juvenile sandeel (Ammodytes tobianus) and assess their uptake, clearance, and metabolic turnover rates. Juvenile sandeel were fed for 16 days in the laboratory on a formulated diet enriched in (13)C16...

  2. Effect of energy level sequences and neutron–proton interaction on α-particle preformation probability

    International Nuclear Information System (INIS)

    Ismail, M.; Adel, A.

    2013-01-01

    A realistic density-dependent nucleon–nucleon (NN) interaction with finite-range exchange part which produces the nuclear matter saturation curve and the energy dependence of the nucleon–nucleus optical model potential is used to calculate the preformation probability, S α , of α-decay from different isotones with neutron numbers N=124,126,128,130 and 132. We studied the variation of S α with the proton number, Z, for each isotone and found the effect of neutron and proton energy levels of parent nuclei on the behavior of the α-particle preformation probability. We found that S α increases regularly with the proton number when the proton pair in α-particle is emitted from the same level and the neutron level sequence is not changed during the Z-variation. In this case the neutron–proton (n–p) interaction of the two levels, contributing to emission process, is too small. On the contrary, if the proton or neutron level sequence is changed during the emission process, S α behaves irregularly, the irregular behavior increases if both proton and neutron levels are changed. This behavior is accompanied by change or rapid increase in the strength of n–p interaction

  3. Simulation of aerosol flow interaction with a solid body on molecular level

    Science.gov (United States)

    Amelyushkin, Ivan A.; Stasenko, Albert L.

    2018-05-01

    Physico-mathematical models and numerical algorithm of two-phase flow interaction with a solid body are developed. Results of droplet motion and its impingement upon a rough surface in real gas boundary layer simulation on the molecular level obtained via molecular dynamics technique are presented.

  4. Structures, values, and interaction in field-level partnerships: the case of UNHCR and NGOs

    NARCIS (Netherlands)

    Mommers, C.; Wessel, van M.G.J.

    2009-01-01

    This article discusses the process of transforming partnership from a conceptual framework into a practical, operational framework for field-level interaction among humanitarian organisations. The authors approach this transformation from the perspective of the core values of the partnership concept

  5. Glucose levels and genetic variants across transcriptional pathways: interaction effects with BMI

    NARCIS (Netherlands)

    Povel, C.M.; Feskens, E.J.M.; Imholz, S.; Blaak, E.E.; Boer, J.M.A.; Dollé, M.E.T.

    2010-01-01

    Objective: Much of the genetic variation in glucose levels remains to be discovered. Especially, research on gene–environment interactions is scarce. Overweight is one of the main risk factors for hyperglycemia. As transcriptional regulation is important for both weight maintenance and glucose

  6. Random model of two-level atoms interacting with electromagnetic field

    International Nuclear Information System (INIS)

    Kireev, A.N.; Meleshko, A.N.

    1983-12-01

    A phase transition has been studied in a random system of two-level atoms interacting with an electromagnetic field. It is shown that superradiation can arise when there is short-range order in a spin-subsystem. The existence of long-range order is irrelevant for this phase transition

  7. Effect of the Level of Inquiry on Student Interactions in Chemistry Laboratories

    Science.gov (United States)

    Xu, Haozhi; Talanquer, Vicente

    2013-01-01

    The central goal of our exploratory study was to investigate differences in college chemistry students' interactions during lab experiments with different levels of inquiry. This analysis was approached from three major analytic dimensions: (i) functional analysis; (ii) cognitive processing; and (iii) social processing. According to our results,…

  8. Trophic cascades: the primacy of trait-mediated indirect interactions

    Czech Academy of Sciences Publication Activity Database

    Schmitz, O. J.; Křivan, Vlastimil; Ovadia, O.

    2004-01-01

    Roč. 7, - (2004), s. 153-163 ISSN 1461-023X R&D Projects: GA ČR GA201/03/0091 Institutional research plan: CEZ:AV0Z5007907 Keywords : adaptive foraging * anti-predator behaviour * cascading effects Subject RIV: EH - Ecology, Behaviour Impact factor: 3.914, year: 2004

  9. Interacting trophic forcing and the population dynamics of herring

    DEFF Research Database (Denmark)

    Lindegren, Martin; Ostman, Orjan; Gardmark, Anna

    2011-01-01

    -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....... 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...... cycle. Our results indicate significant bottom-up effects of zooplankton and interspecific competition from sprat (Sprattus sprattus), particularly on younger age classes of herring. Although top-down forcing through fishing and predation by grey seals (Halichoerus grypus) and Atlantic cod (Gadus morhua...

  10. Urban land use decouples plant-herbivore-parasitoid interactions at multiple spatial scales.

    Directory of Open Access Journals (Sweden)

    Amanda E Nelson

    Full Text Available Intense urban and agricultural development alters habitats, increases fragmentation, and may decouple trophic interactions if plants or animals cannot disperse to needed resources. Specialist insects represent a substantial proportion of global biodiversity and their fidelity to discrete microhabitats provides a powerful framework for investigating organismal responses to human land use. We sampled site occupancy and densities for two plant-herbivore-parasitoid systems from 250 sites across a 360 km2 urban/agricultural landscape to ask whether and how human development decouples interactions between trophic levels. We compared patterns of site occupancy, host plant density, herbivory and parasitism rates of insects at two trophic levels with respect to landcover at multiple spatial scales. Geospatial analyses were used to identify landcover characters predictive of insect distributions. We found that herbivorous insect densities were decoupled from host tree densities in urban landcover types at several spatial scales. This effect was amplified for the third trophic level in one of the two insect systems: despite being abundant regionally, a parasitoid species was absent from all urban/suburban landcover even where its herbivore host was common. Our results indicate that human land use patterns limit distributions of specialist insects. Dispersal constraints associated with urban built development are specifically implicated as a limiting factor.

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

    Science.gov (United States)

    Wang, Xin; Fan, Meng; Hao, Lina

    2017-09-01

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

  12. Effect of sublethal levels of ionizing radiation on a predator-prey interaction

    International Nuclear Information System (INIS)

    Chee, P.C.

    1976-01-01

    The predator-prey interaction studied was that between the largemouth bass (Micropterus salmoides) and the fathead minnow (Pimephales promelas) in an artificial test environment. Experiments were first conducted to determine the 50% lethal dose at 30 days of the minnow. Three different dose rates were used to test the effect of dose rate on the 50% lethal dose value. After the 50% lethal dose was determined the predator-prey interaction experiment was conducted using 30% of the 50% lethal dose as the highest radiation dose, this dose being considered the upper limit to sublethal radiation levels. A 4 x 4 Latin square design was chosen for the experiment, with four treatment levels (control plus three radiation levels) and four replicates. In each test 10 prey minnow were offered to one predator bass and the number of prey left after 14 days was the parameter of interest. A predator-prey interaction experiment using a single high level of radiation and two types of controls as conducted to ascertain the ability of the test environment to detect changes in the predator-prey interaction. The two types of controls were irradiated prey not exposed to predation and non-irradiated prey exposed to predation. An experiment was also conducted to test the correlation between the physical activity patterns of minnow and different doses of radiation. At a dose rate of 37.8 rad/min the 50% lethal dose at 30 days for minnow was found to be 2650 rad. It was found that dose rate had a strong influence on the 50% lethal dose. In the predator-prey interaction test it was found that the 14-day survival rate of prey was unaffected by sublethal levels of ionizing radiation. No significant correlation was detected between the physical activity patterns of minnow and radiation dose

  13. Non-linear interactions of multi-level atoms with a near-resonant standing wave

    International Nuclear Information System (INIS)

    O'Kane, T.J.; Scholten, R.E.; Walkiewicz, M.R.; Farrell, P.M.

    1998-01-01

    Using a semiclassical density matrix formalism we have calculated the behavior of multi-level atoms interacting with a standing wave field, and show how complex non-linear phenomena, including multi-photon effects, combine to produce saturation spectra as observed in experiments. We consider both 20-level sodium and 24-level rubidium models, contrasting these with a simple 2-level case. The influence of parameters such as atomic trajectory and the time the atom remains in the beam are shown to have a critical effect on the lineshape of these resonances and the emission/absorption processes. Stable oscillations in the excited state populations for both the two-level and multi-level cases are shown to be limit cycles. These limit cycles undergo period doubling as the system evolves into chaos. Finally, using a Monte Carlo treatment, these processes average to produce saturated absorption spectra complete with power and Doppler broadening effects consistent with experiment. (authors)

  14. 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.

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

    Science.gov (United States)

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

    2006-08-01

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

  16. 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.

  17. 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...

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  19. Interaction between LRP5 and periostin gene polymorphisms on serum periostin levels and cortical bone microstructure.

    Science.gov (United States)

    Pepe, J; Bonnet, N; Herrmann, F R; Biver, E; Rizzoli, R; Chevalley, T; Ferrari, S L

    2018-02-01

    We investigated the interaction between periostin SNPs and the SNPs of the genes assumed to modulate serum periostin levels and bone microstructure in a cohort of postmenopausal women. We identified an interaction between LRP5 SNP rs648438 and periostin SNP rs9547970 on serum periostin levels and on radial cortical porosity. The purpose of this study is to investigate the interaction between periostin gene polymorphisms (SNPs) and other genes potentially responsible for modulating serum periostin levels and bone microstructure in a cohort of postmenopausal women. In 648 postmenopausal women from the Geneva Retirees Cohort, we analyzed 6 periostin SNPs and another 149 SNPs in 14 genes, namely BMP2, CTNNB1, ESR1, ESR2, LRP5, LRP6, PTH, SPTBN1, SOST, TGFb1, TNFRSF11A, TNFSF11, TNFRSF11B and WNT16. Volumetric BMD and bone microstructure were measured by high-resolution peripheral quantitative computed tomography at the distal radius and tibia. Serum periostin levels were associated with radial cortical porosity, including after adjustment for age, BMI, and years since menopause (p = 0.036). Sixteen SNPs in the ESR1, LRP5, TNFRSF11A, SOST, SPTBN1, TNFRSF11B and TNFSF11 genes were associated with serum periostin levels (p range 0.03-0.001) whereas 26 SNPs in 9 genes were associated with cortical porosity at the radius and/or at the tibia. WNT 16 was the gene with the highest number of SNPs associated with both trabecular and cortical microstructure. The periostin SNP rs9547970 was also associated with cortical porosity (p = 0.04). In particular, SNPs in LRP5, ESR1 and near the TNFRSF11A gene were associated with both cortical porosity and serum periostin levels. Eventually, we identified an interaction between LRP5 SNP rs648438 and periostin SNP rs9547970 on serum periostin levels (interaction p = 0.01) and on radial cortical porosity (interaction p = 0.005). These results suggest that periostin expression is genetically modulated, particularly by polymorphisms

  20. 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

  1. Acoustic interactions between inversion symmetric and asymmetric two-level systems

    International Nuclear Information System (INIS)

    Churkin, A; Schechter, M; Barash, D

    2014-01-01

    Amorphous solids, as well as many disordered lattices, display remarkable universality in their low temperature acoustic properties. This universality is attributed to the attenuation of phonons by tunneling two-level systems (TLSs), facilitated by the interaction of the TLSs with the phonon field. TLS-phonon interaction also mediates effective TLS–TLS interactions, which dictates the existence of a glassy phase and its low energy properties. Here we consider KBr:CN, the archetypal disordered lattice showing universality. We calculate numerically, using conjugate gradients method, the effective TLS–TLS interactions for inversion symmetric (CN flips) and asymmetric (CN rotations) TLSs, in the absence and presence of disorder, in two and three dimensions. The observed dependence of the magnitude and spatial power law of the interaction on TLS symmetry, and its change with disorder, characterizes TLS–TLS interactions in disordered lattices in both extreme and moderate dilutions. Our results are in good agreement with the two-TLS model, recently introduced to explain long-standing questions regarding the quantitative universality of phonon attenuation and the energy scale of ≈1–3 K below which universality is observed. (paper)

  2. Modal Analysis on Fluid-Structure Interaction of MW-Level Vertical Axis Wind Turbine Tower

    Directory of Open Access Journals (Sweden)

    Tan Jiqiu

    2014-05-01

    Full Text Available In order to avoid resonance problem of MW-level vertical axis wind turbine induced by wind, a flow field model of the MW-level vertical axis wind turbine is established by using the fluid flow control equations, calculate flow’s velocity and pressure of the MW-level vertical axis wind turbine and load onto tower’s before and after surface, study the Modal analysis of fluid-structure interaction of MW-level vertical axis wind turbine tower. The results show that fluid-structure interaction field of MW- level vertical axis wind turbine tower has little effect on the modal vibration mode, but has a great effect on its natural frequency and the maximum deformation, and the influence will decrease with increasing of modal order; MW-level vertical axis wind turbine tower needs to be raised the stiffness and strength, its structure also needs to be optimized; In the case of satisfy the intensity, the larger the ratio of the tower height and wind turbines diameter, the more soft the MW-level vertical axis wind turbine tower, the lower its frequency.

  3. INTERACTION LEVEL OF SPEAKING ACTIVITIES IN A COURSEBOOK SERIES OF TEACHING TURKISH AS A FOREIGN LANGUAGE

    OpenAIRE

    YAVUZ KIRIK, Muazzez

    2015-01-01

    Informed by the principles of communicative foreign language teaching, this study focuses on the interaction level of speaking activities in the coursebook series of ‘İstanbul- Yabancılar İçin Türkçe Ders Kitabı’. To this end, the study analyzed firstly the rate of two-way speech to one-way speech among speaking activities and then the characteristics of two-way activities were explored with a focus on their compatibility with the nature of real interaction as described in the relevant litera...

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  5. 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

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

    Science.gov (United States)

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

    2016-04-01

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

  7. High-Arctic Plant-Herbivore Interactions under Climate Influence

    DEFF Research Database (Denmark)

    Berg, Thomas B.; Schmidt, Niels M.; Høye, Toke Thomas

    This chapter focuses on a 10-year data series from Zackenberg on the trophic interactions between two characteristic arctic plant species, arctic willow Salix arctica and mountain avens Dryas octopetala, and three herbivore species covering the very scale of size present at Zackenberg, namely......, the moth Sympistis zetterstedtii, the collared lemming Dicrostonyx groenlandicus and the musk ox Ovibos moschatus. Data from Zackenberg show that timing of snowmelt, the length of the growing season and summer temperature are the basic variables that determine the phenology of flowering and primary...... production upon which the herbivores depend, and snow may be the most important climatic factor affecting the different trophic levels and the interactions between them. Hence, the spatio-temporal distribution of snow, as well as thawing events during winter, may have considerable effects on the herbivores...

  8. When ecosystem services interact: crop pollination benefits depend on the level of pest control

    Science.gov (United States)

    Lundin, Ola; Smith, Henrik G.; Rundlöf, Maj; Bommarco, Riccardo

    2013-01-01

    Pollination is a key ecosystem service which most often has been studied in isolation although effects of pollination on seed set might depend on, and interact with, other services important for crop production. We tested three competing hypotheses on how insect pollination and pest control might jointly affect seed set: independent, compensatory or synergistic effects. For this, we performed a cage experiment with two levels of insect pollination and simulated pest control in red clover (Trifolium pratense L.) grown for seed. There was a synergistic interaction between the two services: the gain in seed set obtained when simultaneously increasing pollination and pest control outweighed the sum of seed set gains obtained when increasing each service separately. This study shows that interactions can alter the benefits obtained from service-providing organisms, and this needs to be considered to properly manage multiple ecosystem services. PMID:23269852

  9. Men with elevated testosterone levels show more affiliative behaviours during interactions with women

    Science.gov (United States)

    van der Meij, Leander; Almela, Mercedes; Buunk, Abraham P.; Fawcett, Tim W.; Salvador, Alicia

    2012-01-01

    Testosterone (T) is thought to play a key role in male–male competition and courtship in many vertebrates, but its precise effects are unclear. We explored whether courtship behaviour in humans is modulated and preceded by changes in T. Pairs of healthy male students first competed in a non-physical contest in which their T levels became elevated. Each participant then had a short, informal interaction with either an unfamiliar man or woman. The sex of the stimulus person did not affect the participants' behaviour overall. However, in interactions with women, those men who had experienced a greater T increase during the contest subsequently showed more interest in the woman, engaged in more self-presentation, smiled more and made more eye contact. No such effects were seen in interactions with other men. This is the first study to provide direct evidence that elevating T during male–male competition is followed by increased affiliative behaviour towards women. PMID:21632627

  10. Investigation of the molecular level interactions between mucins and food proteins: Spectroscopic, tribological and rheological studies

    DEFF Research Database (Denmark)

    Celebioglu, Hilal Yilmaz

    The thesis investigated the structure and molecular-level interaction of β-lactoglobulin (BLG) and mucins, representing major components of the dairy products and saliva/digestion systems, respectively. Mucins are long glycoprotein molecules responsible for the gel nature of the mucous layer covers...... epithelial surfaces throughout the body. A literature review of the interactions of different mucin types and saliva mucins with several food proteins and food protein emulsions, as well as their functional properties related to the food oral processing is presented at the first chapter of the thesis (Paper...... V). Most of the studies suggest an electrostatic attraction between positively charged food proteins with negatively charged moieties of mucins (mainly on glycosylated region of mucins). The structural changes occurring during the interaction between BLG, the major whey protein, and bovine...

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Maximilian L Allen

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

  13. Landscape variation influences trophic cascades in dengue vector food webs.

    Science.gov (United States)

    Weterings, Robbie; Umponstira, Chanin; Buckley, Hannah L

    2018-02-01

    The epidemiology of vector-borne diseases is governed by a structured array of correlative and causative factors, including landscape (for example, rural versus urban), abiotic (for example, weather), and biotic (for example, food web) factors. Studies of mosquito-borne diseases rarely address these multiple factors at large spatial scales, which limits insights into how human alterations of landscapes and food webs alter mosquito abundance. We used structural equation modeling to identify the relative magnitude and direction of landscape, abiotic, and food web factors on Aedes larvae and adults across 70 sites in northern Thailand. Food web factors were modeled as mosquito-predator trophic cascades. Landscape context affected mosquito-predator communities in aquatic and terrestrial environments via cascading food web interactions. Several mosquito predators within these food webs showed potential as biocontrol agents in mosquito population control, but their potentials for control were landscape-dependent. In terrestrial food webs, the habitat-sensitive tokay gecko structured mosquito-predator communities, indicating that a conservation approach to vector control could be a useful addition to existing control efforts.

  14. Transmutations across hierarchical levels

    International Nuclear Information System (INIS)

    O'Neill, R.V.

    1977-01-01

    The development of large-scale ecological models depends implicitly on a concept known as hierarchy theory which views biological systems in a series of hierarchical levels (i.e., organism, population, trophic level, ecosystem). The theory states that an explanation of a biological phenomenon is provided when it is shown to be the consequence of the activities of the system's components, which are themselves systems in the next lower level of the hierarchy. Thus, the behavior of a population is explained by the behavior of the organisms in the population. The initial step in any modeling project is, therefore, to identify the system components and the interactions between them. A series of examples of transmutations in aquatic and terrestrial ecosystems are presented to show how and why changes occur. The types of changes are summarized and possible implications of transmutation for hierarchy theory, for the modeler, and for the ecological theoretician are discussed

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

    Science.gov (United States)

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

    2018-05-30

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

  16. 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

  17. Integrating Micro-level Interactions with Social Network Analysis in Tie Strength Research

    DEFF Research Database (Denmark)

    Torre, Osku; Gupta, Jayesh Prakash; Kärkkäinen, Hannu

    2017-01-01

    of tie strength based on reciprocal interaction from publicly available Facebook data, and suggest that this approach could work as a basis for further tie strength studies. Our approach makes use of weak tie theory, and enables researchers to study micro-level interactions (i.e. discussions, messages......A social tie is a target for ongoing, high-level scientific debate. Measuring the tie strength in social networks has been an important topic for academic studies since Mark Granovetter's seminal papers in 1970's. However, it is still a problematic issue mainly for two reasons: 1) existing tie...... strengthening process in online social networks. Therefore, we suggest a new approach to tie strength research, which focuses on studying communication patterns (edges) more rather than actors (nodes) in a social network. In this paper we build a social network analysis-based approach to enable the evaluation...

  18. Gene-diet interaction effects on BMI levels in the Singapore Chinese population.

    Science.gov (United States)

    Chang, Xuling; Dorajoo, Rajkumar; Sun, Ye; Han, Yi; Wang, Ling; Khor, Chiea-Chuen; Sim, Xueling; Tai, E-Shyong; Liu, Jianjun; Yuan, Jian-Min; Koh, Woon-Puay; van Dam, Rob M; Friedlander, Yechiel; Heng, Chew-Kiat

    2018-02-24

    Recent genome-wide association studies (GWAS) have identified 97 body-mass index (BMI) associated loci. We aimed to evaluate if dietary intake modifies BMI associations at these loci in the Singapore Chinese population. We utilized GWAS information from six data subsets from two adult Chinese population (N = 7817). Seventy-eight genotyped or imputed index BMI single nucleotide polymorphisms (SNPs) that passed quality control procedures were available in all datasets. Alternative Healthy Eating Index (AHEI)-2010 score and ten nutrient variables were evaluated. Linear regression analyses between z score transformed BMI (Z-BMI) and dietary factors were performed. Interaction analyses were performed by introducing the interaction term (diet x SNP) in the same regression model. Analysis was carried out in each cohort individually and subsequently meta-analyzed using the inverse-variance weighted method. Analyses were also evaluated with a weighted gene-risk score (wGRS) contructed by BMI index SNPs from recent large-scale GWAS studies. Nominal associations between Z-BMI and AHEI-2010 and some dietary factors were identified (P = 0.047-0.010). The BMI wGRS was robustly associated with Z-BMI (P = 1.55 × 10 - 15 ) but not with any dietary variables. Dietary variables did not significantly interact with the wGRS to modify BMI associations. When interaction analyses were repeated using individual SNPs, a significant association between cholesterol intake and rs4740619 (CCDC171) was identified (β = 0.077, adjP interaction  = 0.043). The CCDC171 gene locus may interact with cholesterol intake to increase BMI in the Singaporean Chinese population, however most known obesity risk loci were not associated with dietary intake and did not interact with diet to modify BMI levels.

  19. Trophic transfer of gold nanoparticles from Euglena gracilis or Chlamydomonas reinhardtii to Daphnia magna

    International Nuclear Information System (INIS)

    Lee, Woo-Mi; Yoon, Sung-Ji; Shin, Yu-Jin; An, Youn-Joo

    2015-01-01

    Understanding the trophic transfer of nanoparticles (NPs) is important because NPs are small enough to easily penetrate into organisms. In this study, we evaluated the trophic transfer of gold NPs (AuNPs) within the aquatic food chain. We observed AuNPs transfer from 2 species of primary producers (Chlamydomonas reinhardtii or Euglena gracilis) to the primary consumer (Daphnia magna). Also, bioaccumulation of AuNPs in E. gracilis was higher than that in C. reinhardtii. The reasons for the difference in Au accumulation may be the physical structure of these organisms, and the surface area that is available for interaction with NPs. C. reinhardtii has a cell wall that may act as a barrier to the penetration of NPs. The size of E. gracilis is larger than that of C. reinhardtii. This study demonstrates the trophic transfer of AuNPs from a general producer to a consumer in an aquatic environment. - Highlights: • This study evaluated the trophic transfer of AuNPs in an aquatic food chain. • Chlamydomonas reinhardtii and Euglena gracilis were selected as the primary producers. • Daphnia magna was used as the primary consumer. • The bioaccumulation of AuNPs in E. gracilis was higher than that in C. reinhardtii. • AuNPs were transferred from C. reinhardtii and E. gracilis to D. magna. - Gold nanoparticles can transfer from primary producers (Chlamydomonas reinhardtii or Euglena gracilis) to the primary consumer (Daphnia magna) in an aquatic environment

  20. Enhanced understanding of ectoparasite: host trophic linkages on coral reefs through stable isotope analysis

    Science.gov (United States)

    Demopoulos, Amanda W. J.; Sikkel, Paul C.

    2015-01-01

    Parasitism, although the most common type of ecological interaction, is usually ignored in food web models and studies of trophic connectivity. Stable isotope analysis is widely used in assessing the flow of energy in ecological communities and thus is a potentially valuable tool in understanding the cryptic trophic relationships mediated by parasites. In an effort to assess the utility of stable isotope analysis in understanding the role of parasites in complex coral-reef trophic systems, we performed stable isotope analysis on three common Caribbean reef fish hosts and two kinds of ectoparasitic isopods: temporarily parasitic gnathiids (Gnathia marleyi) and permanently parasitic cymothoids (Anilocra). To further track the transfer of fish-derived carbon (energy) from parasites to parasite consumers, gnathiids from host fish were also fed to captive Pederson shrimp (Ancylomenes pedersoni) for at least 1 month. Parasitic isopods had δ13C and δ15N values similar to their host, comparable with results from the small number of other host–parasite studies that have employed stable isotopes. Adult gnathiids were enriched in 15N and depleted in13C relative to juvenile gnathiids, providing insights into the potential isotopic fractionation associated with blood-meal assimilation and subsequent metamorphosis. Gnathiid-fed Pedersen shrimp also had δ13C values consistent with their food source and enriched in 15N as predicted due to trophic fractionation. These results further indicate that stable isotopes can be an effective tool in deciphering cryptic feeding relationships involving parasites and their consumers, and the role of parasites and cleaners in carbon transfer in coral-reef ecosystems specifically.

  1. Enhanced understanding of ectoparasite–host trophic linkages on coral reefs through stable isotope analysis

    Directory of Open Access Journals (Sweden)

    Amanda W.J. Demopoulos

    2015-04-01

    Full Text Available Parasitism, although the most common type of ecological interaction, is usually ignored in food web models and studies of trophic connectivity. Stable isotope analysis is widely used in assessing the flow of energy in ecological communities and thus is a potentially valuable tool in understanding the cryptic trophic relationships mediated by parasites. In an effort to assess the utility of stable isotope analysis in understanding the role of parasites in complex coral-reef trophic systems, we performed stable isotope analysis on three common Caribbean reef fish hosts and two kinds of ectoparasitic isopods: temporarily parasitic gnathiids (Gnathia marleyi and permanently parasitic cymothoids (Anilocra. To further track the transfer of fish-derived carbon (energy from parasites to parasite consumers, gnathiids from host fish were also fed to captive Pederson shrimp (Ancylomenes pedersoni for at least 1 month. Parasitic isopods had δ13C and δ15N values similar to their host, comparable with results from the small number of other host–parasite studies that have employed stable isotopes. Adult gnathiids were enriched in 15N and depleted in 13C relative to juvenile gnathiids, providing insights into the potential isotopic fractionation associated with blood-meal assimilation and subsequent metamorphosis. Gnathiid-fed Pedersen shrimp also had δ13C values consistent with their food source and enriched in 15N as predicted due to trophic fractionation. These results further indicate that stable isotopes can be an effective tool in deciphering cryptic feeding relationships involving parasites and their consumers, and the role of parasites and cleaners in carbon transfer in coral-reef ecosystems specifically.

  2. Ecological Interactions Affecting the Efficacy of Aphidius colemani in Greenhouse Crops

    Directory of Open Access Journals (Sweden)

    Sara G. Prado

    2015-06-01

    Full Text Available Aphidius colemani Viereck (Hymenoptera: Braconidae is a solitary endoparasitoid used for biological control of many economically important pest aphids. Given its widespread use, a vast array of literature on this natural enemy exists. Though often highly effective for aphid suppression, the literature reveals that A. colemani efficacy within greenhouse production systems can be reduced by many stressors, both biotic (plants, aphid hosts, other natural enemies and abiotic (climate and lighting. For example, effects from 3rd and 4th trophic levels (fungal-based control products, hyperparasitoids can suddenly decimate A. colemani populations. But, the most chronic negative effects (reduced parasitoid foraging efficiency, fitness seem to be from stressors at the first trophic level. Negative effects from the 1st trophic level are difficult to mediate since growers are usually constrained to particular plant varieties due to market demands. Major research gaps identified by our review include determining how plants, aphid hosts, and A. colemani interact to affect the net aphid population, and how production conditions such as temperature, humidity and lighting affect both the population growth rate of A. colemani and its target pest. Decades of research have made A. colemani an essential part of biological control programs in greenhouse crops. Future gains in A. colemani efficacy and aphid biological control will require an interdisciplinary, systems approach that considers plant production and climate effects at all trophic levels.

  3. Ecological Interactions Affecting the Efficacy of Aphidius colemani in Greenhouse Crops.

    Science.gov (United States)

    Prado, Sara G; Jandricic, Sarah E; Frank, Steven D

    2015-06-11

    Aphidius colemani Viereck (Hymenoptera: Braconidae) is a solitary endoparasitoid used for biological control of many economically important pest aphids. Given its widespread use, a vast array of literature on this natural enemy exists. Though often highly effective for aphid suppression, the literature reveals that A. colemani efficacy within greenhouse production systems can be reduced by many stressors, both biotic (plants, aphid hosts, other natural enemies) and abiotic (climate and lighting). For example, effects from 3rd and 4th trophic levels (fungal-based control products, hyperparasitoids) can suddenly decimate A. colemani populations. But, the most chronic negative effects (reduced parasitoid foraging efficiency, fitness) seem to be from stressors at the first trophic level. Negative effects from the 1st trophic level are difficult to mediate since growers are usually constrained to particular plant varieties due to market demands. Major research gaps identified by our review include determining how plants, aphid hosts, and A. colemani interact to affect the net aphid population, and how production conditions such as temperature, humidity and lighting affect both the population growth rate of A. colemani and its target pest. Decades of research have made A. colemani an essential part of biological control programs in greenhouse crops. Future gains in A. colemani efficacy and aphid biological control will require an interdisciplinary, systems approach that considers plant production and climate effects at all trophic levels.

  4. 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).

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the GodthAyenbsfjord (64 degrees N, 51 degrees W) SW Greenland, through a combination of fieldwork...... and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily...... ration of 1% body C d(-1). Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 mu m, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory...

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

    International Nuclear Information System (INIS)

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

    1983-01-01

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

  7. 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.

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

    Science.gov (United States)

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

    2015-09-01

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

  9. 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.

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

    Science.gov (United States)

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

    2016-01-01

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

  11. Some interactive factors affecting trench-cover integrity on low-level waste sites

    International Nuclear Information System (INIS)

    Hakonson, T.E.; Lane, L.J.; Steger, J.G.; DePoorter, G.L.

    1982-01-01

    This paper describes important mechanisms by which radionuclide can be transported from low-level waste disposal sites into biological pathways, discuss interactions of abiotic and biotic processes, and recommends environmental characteristics that should be measured to design sites that minimize this transport. Past experience at shallow land burial sites for low-level radioactive wastes suggest that occurrences of waste exposure and radionuclide transport are often related to inadequate trench cover designs. Meeting performance standards at low-level waste sites can only be achieved by recognizing that physical, chemical, and biological processes operating on and in a trench cover profile are highly interactive. Failure to do so can lead to improper design criteria and subsequent remedial action procedures that can adversely affect site stability. Based upon field experiments and computer modeling, recommendations are made on site characteristics that require measurement in order to design systems that reduce surface runoff and erosion, manage soil moisture and biota in the cover profile to maximize evapotranspiration and minimize percolation, and place bounds on the intrusion potential of plants and animals into the waste material. Major unresolved problems include developing probabilistic approaches that include climatic variability, improved knowledge of soil-water-plant-erosion relationships, development of practical vegetation establishment and maintenance procedures, prediction and quantification of site potential and plant succession, and understanding the interaction of processes occurring on and in the cover profile with deeper subsurface processes

  12. Toward a framework for levels of robot autonomy in human-robot interaction.

    Science.gov (United States)

    Beer, Jenay M; Fisk, Arthur D; Rogers, Wendy A

    2014-07-01

    A critical construct related to human-robot interaction (HRI) is autonomy, which varies widely across robot platforms. Levels of robot autonomy (LORA), ranging from teleoperation to fully autonomous systems, influence the way in which humans and robots may interact with one another. Thus, there is a need to understand HRI by identifying variables that influence - and are influenced by - robot autonomy. Our overarching goal is to develop a framework for levels of robot autonomy in HRI. To reach this goal, the framework draws links between HRI and human-automation interaction, a field with a long history of studying and understanding human-related variables. The construct of autonomy is reviewed and redefined within the context of HRI. Additionally, the framework proposes a process for determining a robot's autonomy level, by categorizing autonomy along a 10-point taxonomy. The framework is intended to be treated as guidelines to determine autonomy, categorize the LORA along a qualitative taxonomy, and consider which HRI variables (e.g., acceptance, situation awareness, reliability) may be influenced by the LORA.

  13. Single stage three level grid interactive MPPT inverter for PV systems

    International Nuclear Information System (INIS)

    Ozdemir, Saban; Altin, Necmi; Sefa, Ibrahim

    2014-01-01

    Highlights: • A three phase three-level NPC inverter for grid interactive PV systems is proposed. • A novel MPPT algorithm is introduced for single stage systems. • The proposed algorithm is robust with respect to parameter variations of PV system. • THD level is measured as 3.45% and it meets the international standards (<5%). • Total system efficiency is measured as 93.08%. - Abstract: In this study, three-phase, single stage neutral point clamped grid interactive inverter is designed and implemented. The reference current of the voltage source inverter is determined by maximum power point tracking sub-program in order to obtain maximum power from photovoltaic modules instantaneously. Proposed control is realized via TMS320F28335 32-bit floating point processor. The modified incremental conductance method is applied for maximum power point tracking; the PI regulator is used to control the inverter output current shape and level. Galvanic isolation is provided by a line frequency transformer that matches inverter output voltage to the grid voltage level and prevents DC current injection into the grid. Experimental results show that the designed inverter imports energy to the grid with unity power factor, total harmonic distortion level is 3.45% and this value is in the limits of the international standards. In addition, the total efficiency of the system is measured as 93.08%. The proposed system gets the maximum power from photovoltaic module and dispatches into the grid without using additional DC/DC converter

  14. Information Flow Analysis for Human-System Interaction in the SG Level Control

    International Nuclear Information System (INIS)

    Kim, Jong Hyun; Shin, Yeong Cheol

    2008-01-01

    Interaction between automatic control and operators is one of main issues in the application of automation technology. Inappropriate information from automatic control systems causes unexpected problems in human-automation collaboration. Poor information becomes critical, especially when the operator takes over the control from an automation system. Operators cannot properly handle the situation transferred from the automatic mode because of inadequate situation awareness, if the operator is out-of-the loop and the automatic control system fails. Some cases of unplanned reactor trips during the transition between the manual mode and the automatic mode are reported in nuclear power plants (NPPs). Among unplanned reactor trips since 2002, two cases were partially caused by automation-related failures of steam generator (SG) level control. This paper conducts information flow analysis to identify information and control requirement for human-system interaction of SG level control. At first, this paper identifies the level of automation in SG level control systems and then function allocation between system control and human operators. Then information flow analysis for monitoring and transition of automation is performed by adapting job process chart. Information and control requirements will be useful as an input for the human-system interface (HSI) design of SG level control

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-08-15

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

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

    Science.gov (United States)

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

    2002-04-01

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

  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. Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Francesco, E-mail: Francesco.Ambrosio@epfl.ch; Miceli, Giacomo; Pasquarello, Alfredo [Chaire de Simulation à l’Echelle Atomique (CSEA), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2015-12-28

    We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H{sup +}/H{sub 2} level defining the standard hydrogen electrode, the OH{sup −}/OH{sup ∗} level corresponding to the oxidation of the hydroxyl ion, and the H{sub 2}O/OH{sup ∗} level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band

  19. Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals

    Science.gov (United States)

    Ambrosio, Francesco; Miceli, Giacomo; Pasquarello, Alfredo

    2015-12-01

    We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H+/H2 level defining the standard hydrogen electrode, the OH-/OH∗ level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH∗ level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in overall

  20. Effects of irrigation levels on interactions among Lygus hesperus (Hemiptera: Miridae), insecticides, and predators in cotton.

    Science.gov (United States)

    Asiimwe, Peter; Naranjo, Steven E; Ellsworth, Peter C

    2014-04-01

    Variation in plant quality and natural enemy abundance plays an important role in insect population dynamics. In manipulative field studies, we evaluated the impact of varying irrigation levels and insecticide type on densities of Lygus hesperus Knight and the arthropod predator community in cotton. Three watering levels were established via irrigations timed according to three levels of percent soil water depletion (SWD): 20, 40, or 60, where 40% SWD is considered standard grower practice, 60% represents a deficit condition likely to impose plant productivity losses, and 20% represents surplus conditions with likely consequences on excessive vegetative plant production. The two key L. hesperus insecticides used were the broad-spectrum insecticide acephate and the selective insecticide flonicamid, along with an untreated check. We hypothesized that densities of L. hesperus and its associated predators would be elevated at higher irrigation levels and that insecticides would differentially impact L. hesperus and predator dynamics depending on their selectivity. L. hesperus were more abundant at the higher irrigation level (20% SWD) but the predator densities were unaffected by irrigation levels. Both L. hesperus and its predators were affected by the selectivity of the insecticide with highest L. hesperus densities and lowest predator abundance where the broad spectrum insecticide (acephate) was used. There were no direct interactions between irrigation level and insecticides, indicating that insecticide effects on L. hesperus and its predators were not influenced by the irrigation levels used here. The implications of these findings on the overall ecology of insect-plant dynamics and yield in cotton are discussed.

  1. The trophic role of a forest salamander: impacts on invertebrates, leaf litter retention, and the humification process

    Science.gov (United States)

    M. L. Best; H. H. Welsh

    2014-01-01

    Woodland (Plethodontid) salamanders are the most abundant vertebrates in North American forests, functioning as predators on invertebrates and prey for higher trophic levels. We investigated the role of Ensatina (Ensatina eschscholtzii) in regulating invertebrate numbers and leaf litter retention in a northern California forest. Our objective was...

  2. Biological-Physical Interactions on Georges Bank: Plankton Transport and Population Dynamics of the Ocean Quahog, Arctica islandica

    National Research Council Canada - National Science Library

    1997-01-01

    .... These alterations in bank trophic structure may reduce recruitment of higher trophic levels. NPZ and copepod stage structure models embedded in stratified flow over an idealized bank indicate that strong storms...

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

    Science.gov (United States)

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

    2017-12-26

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

  4. Reduced interhemispheric interaction in non-autistic individuals with normal but high levels of autism traits.

    Science.gov (United States)

    O'Keefe, Natalie; Lindell, Annukka K

    2013-11-01

    People with autism spectrum disorder (ASD) show superior performance for tasks requiring detail-focused processing. Atypical neural connectivity and reduced interhemispheric communication are posited to underlie this cognitive advantage. Given recent conceptualization of autism as a continuum, we sought to investigate whether people with normal but high levels of autism like traits (AQ) also exhibit reduced hemispheric interaction. Sixty right-handed participants completed the AQ questionnaire (Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001) and a lateralised letter matching task that assessed unilateral and bilateral performance in response to simple (physical) and complex (identity) matches. Whereas people with low self-rated AQ scores showed a bilateral advantage for the more complex task, indicating normal interhemispheric interaction, people in the high AQ group failed to show a bilateral gain for the computationally demanding stimuli. This finding of disrupted interhemispheric interaction converges with a dimensional conceptualisation of ASD, suggesting that the structural anomalies of ASD extend to non-autistic individuals with high levels of autism traits. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. Interaction betwen Lead and Bone Protein to Affect Bone Calcium Level Using UV-Vis Spectroscopy

    Science.gov (United States)

    Noor, Z.; Azharuddin, A.; Aflanie, I.; Kania, N.; Suhartono, E.

    2018-05-01

    This present study aim to evaluate the interactions between lead (Pb) and with bone protein by UV-Vis approach. In addition, this prsent study also aim to investigate the effect of Pb on bone calcium (Ca) level. The present study was a true experimental study design to examine the impact of Pb exposure in bone of male rats (Rattus novergicus). The study involved 5 groups, P1 was the control group, while the other (P2-P5) were the case group with exposure of Pb in different concentration within 4 weeks. At the end of the exposure, the interaction between Pb and protein was determined using UV-Vis spectrophotometric method, and the Ca level was determined using permanganometric method. The results shows that that there is an interaction between Pb and bone protein. The result also shows that the value of the binding constant of Protein-Pb is 32.71. It means Pb have an high affinity to bind with bone protein, which promote a further reaction to induced the release of bone Ca from the bone protein. In conclusion, this present study found an obvious relationship between Pb and bone protein which promote a further reaction to increase the releasing of bone calcium.

  6. [Simulating measles and rubella elimination levels according to social stratification and interaction].

    Science.gov (United States)

    Hincapié-Palacio, Doracelly; Ospina-Giraldo, Juan; Gómez-Arias, Rubén D; Uyi-Afuwape, Anthony; Chowell-Puente, Gerardo

    2010-02-01

    The study was aimed at comparing measles and rubella disease elimination levels in a homogeneous and heterogeneous population according to socioeconomic status with interactions amongst low- and high-income individuals and diversity in the average number of contacts amongst them. Effective reproductive rate simulations were deduced from a susceptibleinfected- recovered (SIR) mathematical model according to different immunisation rates using measles (1980 and 2005) and rubella (1998 and 2005) incidence data from Latin-America and the Caribbean. Low- and high-income individuals' social interaction and their average number of contacts were analysed by bipartite random network analysis. MAPLE 12 (Maplesoft Inc, Ontario Canada) software was used for making the simulations. The progress made in eliminating both diseases between both periods of time was reproduced in the socially-homogeneous population. Measles (2005) would be eliminated in high- and low-income groups; however, it would only be achieved in rubella (2005) if there were a high immunity rate amongst the low-income group. If the average number of contacts were varied, then rubella would not be eliminated, even with a 95 % immunity rate. Monitoring the elimination level in diseases like measles and rubella requires that socio-economic status be considered as well as the population's interaction pattern. Special attention should be paid to communities having diversity in their average number of contacts occurring in confined spaces such as displaced communities, prisons, educational establishments, or hospitals.

  7. Scaling the consequences of interactions between invaders from the individual to the population level.

    Science.gov (United States)

    Griffen, Blaine D

    2016-03-01

    The impact of human-induced stressors, such as invasive species, is often measured at the organismal level, but is much less commonly scaled up to the population level. Interactions with invasive species represent an increasingly common source of stressor in many habitats. However, due to the increasing abundance of invasive species around the globe, invasive species now commonly cause stresses not only for native species in invaded areas, but also for other invasive species. I examine the European green crab Carcinus maenas, an invasive species along the northeast coast of North America, which is known to be negatively impacted in this invaded region by interactions with the invasive Asian shore crab Hemigrapsus sanguineus. Asian shore crabs are known to negatively impact green crabs via two mechanisms: by directly preying on green crab juveniles and by indirectly reducing green crab fecundity via interference (and potentially exploitative) competition that alters green crab diets. I used life-table analyses to scale these two mechanistic stressors up to the population level in order to examine their relative impacts on green crab populations. I demonstrate that lost fecundity has larger impacts on per capita population growth rates, but that both predation and lost fecundity are capable of reducing population growth sufficiently to produce the declines in green crab populations that have been observed in areas where these two species overlap. By scaling up the impacts of one invader on a second invader, I have demonstrated that multiple documented interactions between these species are capable of having population-level impacts and that both may be contributing to the decline of European green crabs in their invaded range on the east coast of North America.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-01

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

  10. Interacting two-level defects as sources of fluctuating high-frequency noise in superconducting circuits

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Clemens [ARC Centre of Excellence for Engineered Quantum Systems, The University of Queensland, Brisbane (Australia); Lisenfeld, Juergen [Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe (Germany); Shnirman, Alexander [Institut fuer Theory der Kondensierten Materie, Karlsruhe Institute of Technology, Karlsruhe (Germany); LD Landau Institute for Theoretical Physics, Moscow (Russian Federation); Poletto, Stefano [IBM TJ Watson Research Centre, Yorktown Heights (United States)

    2016-07-01

    Since the very first experiments, superconducting circuits have suffered from strong coupling to environmental noise, destroying quantum coherence and degrading performance. In state-of-the-art experiments, it is found that the relaxation time of superconducting qubits fluctuates as a function of time. We present measurements of such fluctuations in a 3D-transmon circuit and develop a qualitative model based on interactions within a bath of background two-level systems (TLS) which emerge from defects in the device material. In our model, the time-dependent noise density acting on the qubit emerges from its near-resonant coupling to high-frequency TLS which experience energy fluctuations due to their interaction with thermally fluctuating TLS at low frequencies. We support the model by providing experimental evidence of such energy fluctuations observed in a single TLS in a phase qubit circuit.

  11. Charge separation at nanoscale interfaces: energy-level alignment including two-quasiparticle interactions.

    Science.gov (United States)

    Li, Huashan; Lin, Zhibin; Lusk, Mark T; Wu, Zhigang

    2014-10-21

    The universal and fundamental criteria for charge separation at interfaces involving nanoscale materials are investigated. In addition to the single-quasiparticle excitation, all the two-quasiparticle effects including exciton binding, Coulomb stabilization, and exciton transfer are considered, which play critical roles on nanoscale interfaces for optoelectronic applications. We propose a scheme allowing adding these two-quasiparticle interactions on top of the single-quasiparticle energy level alignment for determining and illuminating charge separation at nanoscale interfaces. Employing the many-body perturbation theory based on Green's functions, we quantitatively demonstrate that neglecting or simplifying these crucial two-quasiparticle interactions using less accurate methods is likely to predict qualitatively incorrect charge separation behaviors at nanoscale interfaces where quantum confinement dominates.

  12. Intermolecular interactions of decamethoxinum and acetylsalicylic acid in systems of various complexity levels

    Directory of Open Access Journals (Sweden)

    O. V. Vashchenko

    2016-07-01

    Full Text Available Intermolecular interactions between decamethoxinum (DEC and acetylsalicylic acid (ASА have been studied in the phospholipid-containing systems of escalating complexity levels. The host media for these substances were solvents, L-α-dipalmitoylphosphatidylcholine (DPPC membranes, and samples of human erythrocytes. Peculiar effects caused by DEC-ASА interaction have been observed in each system using appropriate techniques: (a DEC-ASА non-covalent complexes formation in DPPC-containing systems were revealed by mass spectrometry with electrospray ionization; (b joint DEC-ASА action on DPPC model membranes led to increasing of membrane melting temperature Tm, whereas individual drugs caused pronounced Tm decreasing, which was demonstrated by differential scanning calorimetry; (c deceleration of DEC-induced haemolysis of erythrocytes under joint DEC-ASА application was observed by optical microscopy.

  13. Interactive Sea Level Rise App & Online Viewer Offers Deep Dive Into Climate

    Science.gov (United States)

    Turrin, M.; Porter, D. F.; Ryan, W. B. F.; Pfirman, S. L.

    2015-12-01

    Climate has captured the attention of the public but its complexity can cause interested individuals to turn to opinion pieces, news articles or blogs for information. These platforms often oversimplify or present heavily interpreted or personalized perspectives. Data interactives are an extremely effective way to explore complex geoscience topics like climate, opening windows of understanding for the user that have previously been closed. Layering data onto maps through programs like GeoMapApp and the Earth Observer App has allowed users to dig directly into science data, but with only limited scaffolding. The interactive 'Polar Explorer: Sea Level Explorer App' provides a richly layered introduction to a range of topics connected to sea level rise. Each map is supported with a pop up and a short audio file of supplementary material, and an information page that includes the data source and links for further reading. This type of learning platform works well for both the formal and informal learning environment. Through science data displayed as map visualizations the user is invited into topics through an introductory question, such as "Why does sea level change?" After clicking on that question the user moves to a second layer of questions exploring the role of the ocean, the atmosphere, the contribution from the world's glaciers, world's ice sheets and other less obvious considerations such as the role of post-glacial rebound, or the mining of groundwater. Each question ends in a data map, or series of maps, that offer opportunities to interact with the topic. Under the role of the ocean 'Internal Ocean Temperature' offers the user a chance to touch to see temperature values spatially over the world's ocean, or to click through a data series starting at the ocean surface and diving to 5000 meters of depth showing how temperature changes with depth. Other sections, like the role of deglaciation of North America, allow the user to click and see change through

  14. Interactive Effects of Dopamine Baseline Levels and Cycle Phase on Executive Functions: The Role of Progesterone

    Directory of Open Access Journals (Sweden)

    Esmeralda Hidalgo-Lopez

    2017-07-01

    Full Text Available Estradiol and progesterone levels vary along the menstrual cycle and have multiple neuroactive effects, including on the dopaminergic system. Dopamine relates to executive functions in an “inverted U-shaped” manner and its levels are increased by estradiol. Accordingly, dopamine dependent changes in executive functions along the menstrual cycle have been previously studied in the pre-ovulatory phase, when estradiol levels peak. Specifically it has been demonstrated that working memory is enhanced during the pre-ovulatory phase in women with low dopamine baseline levels, but impaired in women with high dopamine baseline levels. However, the role of progesterone, which peaks in the luteal cycle phase, has not been taken into account previously. Therefore, the main goals of the present study were to extend these findings (i to the luteal cycle phase and (ii to other executive functions. Furthermore, the usefulness of the eye blink rate (EBR as an indicator of dopamine baseline levels in menstrual cycle research was explored. 36 naturally cycling women were tested during three cycle phases (menses–low sex hormones; pre-ovulatory–high estradiol; luteal–high progesterone and estradiol. During each session, women performed a verbal N-back task, as measure of working memory, and a single trial version of the Stroop task, as measure of response inhibition and cognitive flexibility. Hormone levels were assessed from saliva samples and spontaneous eye blink rate was recorded during menses. In the N-back task, women were faster during the luteal phase the higher their progesterone levels, irrespective of their dopamine baseline levels. In the Stroop task, we found a dopamine-cycle interaction, which was also driven by the luteal phase and progesterone levels. For women with higher EBR performance decreased during the luteal phase, whereas for women with lower EBR performance improved during the luteal phase. These findings suggest an important

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

    Science.gov (United States)

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

    2010-01-01

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

  16. 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).

  17. 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.

  18. 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

  19. 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.

  20. Content Interactivity: The Effect of Higher Levels of Interactivity on Learner Performance Outcomes and Satisfaction in Web-Based Military Training

    Science.gov (United States)

    Kenyon, Peggy L.

    2012-01-01

    The effect of content interactivity on performance outcomes and satisfaction has been studied by researchers who compared the results of Web-based and computer-based learning to classroom learning. Few scholars have compared the effects of the same content produced at different levels (low and high) of interactivity and the resulting effects. The…

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

    Science.gov (United States)

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

    2006-01-01

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

  2. Level Density In Interacting Boson-Fermion-Fermion Model (IBFFM) Of The Odd-Odd Nucleus 196Au

    International Nuclear Information System (INIS)

    Kabashi, Skender; Bekteshi, Sadik

    2007-01-01

    The level density of the odd-odd nucleus 196Au is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes.The IBFFM total level density is fitted by Gaussian and its tail is also fitted by Bethe formula and constant temperature Fermi gas model

  3. Levels of plasma selenium and urinary total arsenic interact to affect the risk for prostate cancer.

    Science.gov (United States)

    Hsueh, Yu-Mei; Su, Chien-Tien; Shiue, Horng-Sheng; Chen, Wei-Jen; Pu, Yeong-Shiau; Lin, Ying-Chin; Tsai, Cheng-Shiuan; Huang, Chao-Yuan

    2017-09-01

    This study investigated whether plasma selenium levels modified the risk for prostate cancer (PC) related to arsenic exposure. We conducted a case-control study that included 318 PC patients and 318 age-matched, healthy control subjects. Urinary arsenic profiles were examined using HPLC-HG-AAS and plasma selenium levels were measured by ICP-MS. We found that plasma selenium levels displayed a significant dose-dependent inverse association with PC. The odds ratio (OR) and 95% confidence interval (CI) for PC was 0.07 (0.04-0.13) among participants with a plasma selenium level >28.06 μg/dL vs. ≤19.13 μg/dL. A multivariate analysis showed that participants with a urinary total arsenic concentration >29.28 μg/L had a significantly higher OR (1.75, 1.06-2.89) for PC than participants with ≤29.89 μg/L. The combined presence of a low plasma selenium level and a high urinary total arsenic concentration exponentially increased the OR for PC, and additively interacted with PSA at levels ≥20 ng/mL. This is the first epidemiological study to examine the combined effects of plasma selenium and urinary total arsenic levels on the OR for PC. Our data suggest a low plasma selenium level coupled with a high urinary total arsenic concentration creates a significant risk for aggressive PC. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Ecological interactions affecting population-level responses to chemical stress in Mesocyclops leuckarti.

    Science.gov (United States)

    Kulkarni, Devdutt; Hommen, Udo; Schäffer, Andreas; Preuss, Thomas G

    2014-10-01

    Higher tiers of ecological risk assessment (ERA) consider population and community-level endpoints. At the population level, the phenomenon of density dependence is one of the most important ecological processes that influence population dynamics. In this study, we investigated how different mechanisms of density dependence would influence population-level ERA of the cyclopoid copepod Mesocyclops leuckarti under toxicant exposure. We used a combined approach of laboratory experiments and individual-based modelling. An individual-based model was developed for M. leuckarti to simulate population dynamics under triphenyltin exposure based on individual-level ecological and toxicological data from laboratory experiments. The study primarily aimed to-(1) determine which life-cycle processes, based on feeding strategies, are most significant in determining density dependence (2) explore how these mechanisms of density dependence affect extrapolation from individual-level effects to the population level under toxicant exposure. Model simulations showed that cannibalism of nauplii that were already stressed by TPT exposure contributed to synergistic effects of biotic and abiotic factors and led to a twofold stress being exerted on the nauplii, thereby resulting in a higher population vulnerability compared to the scenario without cannibalism. Our results suggest that in population-level risk assessment, it is easy to underestimate toxicity unless underlying ecological interactions including mechanisms of population-level density regulation are considered. This study is an example of how a combined approach of experiments and mechanistic modelling can lead to a thorough understanding of ecological processes in ecotoxicology and enable a more realistic ERA. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. The effect of exchange interaction on quasiparticle Landau levels in narrow-gap quantum well heterostructures.

    Science.gov (United States)

    Krishtopenko, S S; Gavrilenko, V I; Goiran, M

    2012-04-04

    Using the 'screened' Hartree-Fock approximation based on the eight-band k·p Hamiltonian, we have extended our previous work (Krishtopenko et al 2011 J. Phys.: Condens. Matter 23 385601) on exchange enhancement of the g-factor in narrow-gap quantum well heterostructures by calculating the exchange renormalization of quasiparticle energies, the density of states at the Fermi level and the quasiparticle g-factor for different Landau levels overlapping. We demonstrate that exchange interaction yields more pronounced Zeeman splitting of the density of states at the Fermi level and leads to the appearance of peak-shaped features in the dependence of the Landau level energies on the magnetic field at integer filling factors. We also find that the quasiparticle g-factor does not reach the maximum value at odd filling factors in the presence of large overlapping of spin-split Landau levels. We advance an argument that the behavior of the quasiparticle g-factor in weak magnetic fields is defined by a random potential of impurities in narrow-gap heterostructures. © 2012 IOP Publishing Ltd

  6. The impact of plant chemical diversity on plant-herbivore interactions at the community level.

    Science.gov (United States)

    Salazar, Diego; Jaramillo, Alejandra; Marquis, Robert J

    2016-08-01

    Understanding the role of diversity in ecosystem processes and species interactions is a central goal of ecology. For plant-herbivore interactions, it has been hypothesized that when plant species diversity is reduced, loss of plant biomass to herbivores increases. Although long-standing, this hypothesis has received mixed support. Increasing plant chemical diversity with increasing plant taxonomic diversity is likely to be important for plant-herbivore interactions at the community level, but the role of chemical diversity is unexplored. Here we assess the effect of volatile chemical diversity on patterns of herbivore damage in naturally occurring patches of Piper (Piperaceae) shrubs in a Costa Rican lowland wet forest. Volatile chemical diversity negatively affected total, specialist, and generalist herbivore damage. Furthermore, there were differences between the effects of high-volatility and low-volatility chemical diversity on herbivore damage. High-volatility diversity reduced specialist herbivory, while low-volatility diversity reduced generalist herbivory. Our data suggest that, although increased plant diversity is expected to reduce average herbivore damage, this pattern is likely mediated by the diversity of defensive compounds and general classes of anti-herbivore traits, as well as the degree of specialization of the herbivores attacking those plants.

  7. Canyon of current suppression in an interacting two-level quantum dot

    DEFF Research Database (Denmark)

    Karlström, O; Pedersen, Jonas Nyvold; Samuelsson, P

    2011-01-01

    Motivated by the recent discovery of a canyon of conductance suppression in a two-level equal-spin quantum dot system [Phys. Rev. Lett. 104, 186804 (2010)], the transport through this system is studied in detail. At low bias and low temperature a strong current suppression is found around...... the electron-hole symmetry point independent of the couplings, in agreement with previous results. By means of a Schrieffer–Wolff transformation we are able to give an intuitive explanation to this suppression in the low-energy regime. In the general situation, numerical simulations are carried out using...... for the current suppression. It is also shown how broadening, interference, and a finite interaction energy cause a shift of the current minimum away from degeneracy. Finally we see how an increased population of the upper level leads to current peaks on each side of the suppression line. At sufficiently high...

  8. The Interaction Features of the Multi-Level Retaining Walls with Soil Mass

    Directory of Open Access Journals (Sweden)

    Boyko Igor

    2017-09-01

    Full Text Available The interaction features of multi-level retaining walls with soil base were researched by changing their geometric parameters and locality at the plan. During excavation of deep foundation pits it is important to choose the type of constructions which influences on the horizontal displacements. The distance between the levels of retaining walls should be based on the results of numerical modelling. The objective of this paper is to present a comparison between the data of numerical simulations and the results of the in-situ lateral tests of couple piles. The problems have been solved by using the following soil models: Coulomb-Mohr model; model, which is based on the dilatation theory; elastic-plastic model with variable stiffness parameters.

  9. The Interaction Features of the Multi-Level Retaining Walls with Soil Mass

    Science.gov (United States)

    Boyko, Igor; Skochko, Liudmyla; Zhuk, Veronica

    2017-09-01

    The interaction features of multi-level retaining walls with soil base were researched by changing their geometric parameters and locality at the plan. During excavation of deep foundation pits it is important to choose the type of constructions which influences on the horizontal displacements. The distance between the levels of retaining walls should be based on the results of numerical modelling. The objective of this paper is to present a comparison between the data of numerical simulations and the results of the in-situ lateral tests of couple piles. The problems have been solved by using the following soil models: Coulomb-Mohr model; model, which is based on the dilatation theory; elastic-plastic model with variable stiffness parameters.

  10. Energy-level splitting of multicharged ions due to interaction with own radiation field

    International Nuclear Information System (INIS)

    Gajnutdinov, R.Kh.; Kalashnikov, K.K.

    1991-01-01

    The overlapping of the energy levels of He-like uranium states with identical principal quantum numbers is investigated. Results are presented of a numerical calculation of the states produced as a result of mixing of the 2s 1/2 8p 1/2 and 2p 1/2 8p 1/2 states and of the respective spectral lines. It is shown that the interaction between the ion and its own radiation field splits each of the overlapping energy levels into several sublevels. The sublevels are isolated from each to other such an extent that interference effects become insignificant. The shapes of the spectral lines differ pronouncedly from the Lorentz shape and many of the line are anomaously narrow

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

    Science.gov (United States)

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

    2015-01-01

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

  12. Use of a plant level logic model for quantitative assessment of systems interactions

    International Nuclear Information System (INIS)

    Chu, B.B.; Rees, D.C.; Kripps, L.P.; Hunt, R.N.; Bradley, M.

    1985-01-01

    The Electric Power Research Institute (EPRI) has sponsored a research program to investigate methods for identifying systems interactions (SIs) and for the evaluation of their importance. Phase 1 of the EPRI research project focused on the evaluation of methods for identification of SIs. Major results of the Phase 1 activities are the documentation of four different methodologies for identification of potential SIs and development of guidelines for performing an effective plant walkdown in support of an SI analysis. Phase II of the project, currently being performed, is utilizing a plant level logic model of a pressurized water reactor (PWR) to determine the quantitative importance of identified SIs. In Phase II, previously reported events involving interactions between systems were screened and selected on the basis of their relevance to the Baltimore Gas and Electric (BGandE) Calvert Cliffs Nuclear Power Plant design and perceived potential safety significance. Selected events were then incorporated into the BGandE plant level GO logic model. The model is being exercised to calculate the relative importance of these events. Five previously identified event scenarios, extracted from licensee event reports (LERs) are being evaluated during the course of the study. A key feature of the approach being used in Phase II is the use of a logic model in a manner to effectively evaluate the impact of events