Bioaccumulation trends of arsenic and antimony in a freshwater ecosystem affected by mine drainage

2016 ◽  
Vol 13 (1) ◽  
pp. 149 ◽  
Author(s):  
Meghan A. Dovick ◽  
Thomas R. Kulp ◽  
Robert S. Arkle ◽  
David S. Pilliod
Keyword(s):  
Food Web ◽  
Trophic Level ◽  
Microbial Mats ◽  
Mine Drainage ◽  
Trophic Levels ◽  
Whole Body ◽  
Freshwater Ecosystem ◽  
High Tolerance ◽  
Mine Site ◽  
The Past

Environmental context The food web behaviours of As and Sb are poorly understood. We compare As and Sb bioaccumulation in a contaminated freshwater ecosystem. Metalloid accumulation decreased with increasing trophic level. Bioprecipitated minerals in microbial mats represent a direct route of uptake (by ingestion) of metalloids to tadpoles, which contained the highest concentrations ever reported. We demonstrate food web bioaccumulation, but not biomagification, of As and Sb. We also report an unexpectedly high tolerance of tadpoles to metalloid toxicity. Abstract We compared As and Sb bioaccumulation and biomagnification when these metalloids co-occurred at varying environmental concentrations in a stream and wetlands near a contaminated mine site in Idaho (USA). We measured As and Sb concentrations in water and substrate samples, and in tissues of organisms representing several trophic levels. Bioaccumulation of both As and Sb was observed in stream organisms with the following trend of bio-diminution with increasing trophic level: primary producers>tadpoles>macroinvertebrates>trout. We also note reductions in metalloid concentrations in one of two stream remediation reaches engineered within the past 17 years to ameliorate metalloid contamination in the stream. Several wetlands contained thick microbial mats and were highly populated with boreal toad tadpoles that fed on them. The mats were extremely contaminated (up to 76564mgkg–1 As and 675mgkg–1 Sb) with amorphous As- and Sb-bearing minerals that we interpret as biogenic precipitates from geomicrobiological As- and Sb-cycling. Ingested mat material provided a direct source of metalloids to tadpoles, and concentrations of 3867mgkg–1 (As) and 375mgkg–1 (Sb) reported here represent the highest whole body As and Sb levels ever reported in living tadpoles. The bulk of tadpole metalloid burden remained in the gut despite attempts to purge the tadpoles prior to analysis. This study adds to a number of recent investigations reporting bioaccumulation, but not biomagnification, of As and Sb in food webs. Moreover, our results suggest that tadpoles, in particular, may be more resistant to metalloid contamination than previously assumed.

scholarly journals Drivers of trophic amplification of ocean productivity trends in a changing climate

2014 ◽  
Vol 11 (24) ◽  
pp. 7125-7135 ◽  
Author(s):  
C. A. Stock ◽  
J. P. Dunne ◽  
J. G. John
Keyword(s):  
Food Web ◽  
21St Century ◽  
Trophic Level ◽  
Net Primary Production ◽  
Trophic Levels ◽  
The Arctic ◽  
Phytoplankton Production ◽  
Planktonic Food ◽  
Projected Changes ◽  
Zooplankton Growth

Abstract. Pronounced projected 21st century trends in regional oceanic net primary production (NPP) raise the prospect of significant redistributions of marine resources. Recent results further suggest that NPP changes may be amplified at higher trophic levels. Here, we elucidate the role of planktonic food web dynamics in driving projected changes in mesozooplankton production (MESOZP) found to be, on average, twice as large as projected changes in NPP by the latter half of the 21st century under a high emissions scenario in the Geophysical Fluid Dynamics Laboratory's ESM2M–COBALT (Carbon, Ocean Biogeochemistry and Lower Trophics) earth system model. Globally, MESOZP was projected to decline by 7.9% but regional MESOZP changes sometimes exceeded 50%. Changes in three planktonic food web properties – zooplankton growth efficiency (ZGE), the trophic level of mesozooplankton (MESOTL), and the fraction of NPP consumed by zooplankton (zooplankton–phytoplankton coupling, ZPC), explain the projected amplification. Zooplankton growth efficiencies (ZGE) changed with NPP, amplifying both NPP increases and decreases. Negative amplification (i.e., exacerbation) of projected subtropical NPP declines via this mechanism was particularly strong since consumers in the subtropics have limited surplus energy above basal metabolic costs. Increased mesozooplankton trophic level (MESOTL) resulted from projected declines in large phytoplankton production. This further amplified negative subtropical NPP declines but was secondary to ZGE and, at higher latitudes, was often offset by increased ZPC. Marked ZPC increases were projected for high-latitude regions experiencing shoaling of deep winter mixing or decreased winter sea ice – both tending to increase winter zooplankton biomass and enhance grazer control of spring blooms. Increased ZPC amplified projected NPP increases in the Arctic and damped projected NPP declines in the northwestern Atlantic and Southern Ocean. Improved understanding of the physical and biological interactions governing ZGE, MESOTL and ZPC is needed to further refine estimates of climate-driven productivity changes across trophic levels.

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

2007 ◽  
Vol 79 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Alexandre L. Pereira ◽  
Evanilde Benedito ◽  
Cássia M. Sakuragui
Keyword(s):  
Stable Isotopes ◽  
Carbon Source ◽  
Isotopic Composition ◽  
Spatial Variation ◽  
Food Web ◽  
Trophic Level ◽  
Trophic Position ◽  
Trophic Levels ◽  
C3 Plants ◽  
The One

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

scholarly journals Trophic Patterns of Bighead Carp and Silver Carp Follow the Seasonality of Resource Availability

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1429
Author(s):  
Jia Yu ◽  
Jun Chen ◽  
Xuwei Deng ◽  
Zhixu Wu ◽  
Zuoming Yu ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Food Web ◽  
Trophic Level ◽  
Seasonal Variations ◽  
Silver Carp ◽  
Food Resources ◽  
Freshwater Ecosystems ◽  
Trophic Levels ◽  
Bighead Carp ◽  
Filter Feeding

The influence of seasonality of the aquatic environment on food web has been notoriously understudied in empirical ecology. In this study, we focus on seasonal changes in one key attribute of a food web, the trophic level. We determine whether seasonal variations of fish trophic levels could be indicated by the change in food resources. Silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) were used to explore the responses of trophic levels of the filter-feeding fish to seasonal variations of food resources. Combined stable isotopic analysis and dietary analysis revealed that filter-feeding fish tended to have a higher trophic level in spring (May) and autumn (September and October). This may result from the abundant density of food resources (zooplankton and phytoplankton) and fish flexible foraging strategy, as we predicted that the trophic level follows the seasonality of food availability. Pearson’ correlation analysis and a structural equation model showed that seasonal variation of total phosphorus and water temperature could indirectly affect trophic levels of silver carp and bighead carp by mediating the abundance of phytoplankton and zooplankton directly and indirectly along the food chain. According to these findings, the seasonal variation of food resources could be an important indicator of the temporal dynamics of the food web trophic pattern in freshwater ecosystems.

scholarly journals Top predators govern multitrophic diversity effects in tritrophic food webs

2020 ◽  
Author(s):  
Ruben Ceulemans ◽  
Christian Guill ◽  
Ursula Gaedke
Keyword(s):  
Temporal Variation ◽  
Food Web ◽  
Food Webs ◽  
Functional Diversity ◽  
Trophic Level ◽  
Ecosystem Functioning ◽  
Initial Conditions ◽  
Trophic Levels ◽  
Natural Food ◽  
Model Parameters

AbstractIt is well known that functional diversity strongly affects ecosystem functioning. However, even in rather simple model communities consisting of only two or, at best, three trophic levels, the relationship between multitrophic functional diversity and ecosystem functioning appears difficult to generalize, due to its high contextuality. In this study, we considered several differently structured tritrophic food webs, in which the amount of functional diversity was varied independently on each trophic level. To achieve generalizable results, largely independent of parametrization, we examined the outcomes of 128, 000 parameter combinations sampled from ecologically plausible intervals, with each tested for 200 randomly sampled initial conditions. Analysis of our data was done by training a Random Forest model. This method enables the identification of complex patterns in the data through partial dependence graphs, and the comparison of the relative influence of model parameters, including the degree of diversity, on food web properties. We found that bottom-up and top-down effects cascade simultaneously throughout the food web, intimately linking the effects of functional diversity of any trophic level to the amount of diversity of other trophic levels, which may explain the difficulty in unifying results from previous studies. Strikingly, only with high diversity throughout the whole food web, different interactions synergize to ensure efficient exploitation of the available nutrients and efficient biomass transfer, ultimately leading to a high biomass and production on the top level. The temporal variation of biomass showed a more complex pattern with increasing multitrophic diversity: while the system initially became less variable, eventually the temporal variation rose again due to the increasingly complex dynamical patterns. Importantly, top predator diversity and food web parameters affecting the top trophic level were of highest importance to determine the biomass and temporal variability of any trophic level. Overall, our study reveals that the mechanisms by which diversity influences ecosystem functioning are affected by every part of the food web, hampering the extrapolation of insights from simple monotrophic or bitrophic systems to complex natural food webs.

scholarly journals Phenotypic variation explains food web structural patterns

2017 ◽  
Vol 114 (42) ◽  
pp. 11187-11192 ◽  
Author(s):  
Jean P. Gibert ◽  
John P. DeLong
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Level ◽  
Phenotypic Variation ◽  
Structural Features ◽  
Trophic Levels ◽  
Intake Rate ◽  
Food Web Structure ◽  
Total Food Intake ◽  
Variation Sets

Food webs (i.e., networks of species and their feeding interactions) share multiple structural features across ecosystems. The factors explaining such similarities are still debated, and the role played by most organismal traits and their intraspecific variation is unknown. Here, we assess how variation in traits controlling predator–prey interactions (e.g., body size) affects food web structure. We show that larger phenotypic variation increases connectivity among predators and their prey as well as total food intake rate. For predators able to eat only a few species (i.e., specialists), low phenotypic variation maximizes intake rates, while the opposite is true for consumers with broader diets (i.e., generalists). We also show that variation sets predator trophic level by determining interaction strengths with prey at different trophic levels. Merging these results, we make two general predictions about the structure of food webs: (i) trophic level should increase with predator connectivity, and (ii) interaction strengths should decrease with prey trophic level. We confirm these predictions empirically using a global dataset of well-resolved food webs. Our results provide understanding of the processes structuring food webs that include functional traits and their naturally occurring variation.

scholarly journals Drivers of trophic amplification of ocean productivity trends in a changing climate

2014 ◽  
Vol 11 (7) ◽  
pp. 11331-11359 ◽  
Author(s):  
C. A. Stock ◽  
J. P. Dunne ◽  
J. G. John
Keyword(s):  
Sea Ice ◽  
Food Web ◽  
21St Century ◽  
Trophic Level ◽  
Net Primary Production ◽  
Trophic Levels ◽  
Phytoplankton Production ◽  
Planktonic Food ◽  
Projected Changes ◽  
Zooplankton Growth

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

scholarly journals An approach for coupling higher and lower levels in marine ecosystem models and its application to the North Sea

2015 ◽  
Vol 8 (7) ◽  
pp. 5577-5618 ◽  
Author(s):  
J. A. Beecham ◽  
J. Bruggeman ◽  
J. Aldridge ◽  
S. Mackinson
Keyword(s):  
Environmental Change ◽  
Food Web ◽  
North Sea ◽  
Trophic Level ◽  
Coupled Model ◽  
Trophic Levels ◽  
Biogeochemical Model ◽  
The North ◽  
The North Sea

Abstract. End to end modelling is an attractive and rapidly developing approach to solve developing strategies in marine systems science and management. However problems remain in the area of data matching and sub-model compatibility. A mechanism and novel interfacing system (Couplerlib) is presented whereby a physical/biogeochemical model (GOTM-ERSEM) that predicts dynamics of the lower trophic level (LTL) organisms in marine ecosystems is coupled to a dynamic ecosystem model (Ecosim) that predicts food-web interactions among higher trophic level (HTL) organisms. Coupling is achieved by means of a bespoke interface which handles the system incompatibilities between the models and a more generic Couplerlib library which uses metadata descriptions in extensible mark-up language (XML) to marshal data between groups, paying attention to functional group mappings and compatibility of units between models. In addition, within Couplerlib, models can be coupled across networks by means of socket mechanisms. As a demonstration of this approach, a food web model (Ecopath with Ecosim, EwE) and a physical/biogeochemical model (GOTM-ERSEM) representing the North Sea ecosystem were joined with Couplerlib. The output from GOTM-ERSEM varies between years dependent on oceanographic and meteorological conditions. Although inter-annual variability was clearly present, there was always the tendency for an annual cycle consisting of a peak of diatoms in spring, followed by (less nutritious) flagellates and dinoflagellates through the summer resulting in an early summer peak in the mesozooplankton biomass. Pelagic productivity, predicted by the LTL model, was highly seasonal with little winter food for the higher trophic levels. The Ecosim model was originally based on the assumption of constant annual inputs and, consequently, when coupled, pelagic species suffered population loss over the winter months. By contrast, benthic populations were more stable (although the benthic linkage modelled was purely at the detritus level). The coupled model was used to examine long term effects of environmental change, and showed the system to be nutrient limited, relatively unaffected by forecast climate change, especially in the benthos. The stability of an Ecosim formulation for large higher tropic level food webs is discussed and it is concluded that this kind of coupled model formulation is better for examining the effects of long term environmental change than short term perturbations.

scholarly journals Adaptive harvesting drives fishing down processes, regime shifts, and resilience changes in predator-prey systems

2018 ◽  
Author(s):  
Eric Tromeur ◽  
Nicolas Loeuille
Keyword(s):  
Food Web ◽  
Trophic Level ◽  
Regime Shifts ◽  
Trophic Levels ◽  
Top Down ◽  
Predator Species ◽  
Predator Prey ◽  
Abrupt Changes ◽  
Mean Trophic Level ◽  
High Adaptation

AbstractMany world fisheries display a declining mean trophic level of catches. This “fishing down the food web” is often attributed to reduced densities of high-trophic-level species, reflecting changes in the structure of harvested food webs. However, this pattern can also result from a restructuring of the fishery, that shifts from a focus on depleted upper trophic levels to abundant lower trophic levels. In fact, we show here that fishing down the food web can emerge from the adaptive harvesting of a predator-prey community, where changes in fishing patterns are driven by the relative profitabilities of the harvested species. The shift from a predator- to a prey-focused fishing pattern can yield abrupt changes in the system, and cause sudden losses in species densities. Such regime shifts occur when the predator species is highly valuable relative to the prey, and if it exerts a strong top-down control on the lower trophic level. Moreover, we find that when the two species are jointly harvested, high adaptation speeds can reduce the resilience of fisheries. Our results therefore suggest that flexibility in harvesting strategies will not necessarily benefit fisheries but may actually harm their sustainability.

Relationship between morphometrics and trophic levels in deep-sea fishes

2020 ◽  
Vol 637 ◽  
pp. 225-235 ◽  
Author(s):  
MA Ladds ◽  
MH Pinkerton ◽  
E Jones ◽  
LM Durante ◽  
MR Dunn
Keyword(s):  
Stable Isotopes ◽  
Trophic Level ◽  
Deep Sea ◽  
Strong Relationship ◽  
Ecosystem Model ◽  
Trophic Levels ◽  
Fish Size ◽  
Wide Range ◽  
Gape Size ◽  
Morphological Variables

Marine food webs are structured, in part, by predator gape size. Species found in deep-sea environments may have evolved such that they can consume prey of a wide range of sizes, to maximise resource intake in a low-productivity ecosystem. Estimates of gape size are central to some types of ecosystem model that determine which prey are available to predators, but cannot always be measured directly. Deep-sea species are hypothesized to have larger gape sizes than shallower-water species relative to their body size and, because of pronounced adaptive foraging behaviour, show only a weak relationship between gape size and trophic level. Here we present new data describing selective morphological measurements and gape sizes of 134 osteichthyan and chondrichthyan species from the deep sea (200-1300 m) off New Zealand. We describe how gape size (height, width and area) varied with factors including fish size, taxonomy (class and order within a class) and trophic level estimated from stable isotopes. For deep-sea species, there was a strong relationship between gape size and fish size, better predicted by body mass than total length, which varied by taxonomic group. Results show that predictions of gape size can be made from commonly measured morphological variables. No relationship between gape size and trophic level was found, likely a reflection of using trophic level estimates from stable isotopes as opposed to the commonly used estimates from FishBase. These results support the hypothesis that deep-sea fish are generalists within their environment, including suspected scavenging, even at the highest trophic levels.

History Teaching in Rural Areas: The University of Venda

1996 ◽  
Vol 24 (1) ◽  
pp. 17-23
Author(s):  
Alan Kirkaldy
Keyword(s):  
Rural Areas ◽  
Whole Body ◽  
Social Forces ◽  
Historical Writing ◽  
Social Formation ◽  
History Teaching ◽  
The Past ◽  
The Social ◽  
The University

I would argue that history students should understand that the whole body of historical writing consists of interpretations of the past. They should be able to analyse a wide variety of texts and form their own opinions on a historical topic, and should be able to construct a coherent argument, using evidence to support their opinion. In doing so, they should be actively aware that their argument is no more “true” than that offered by any other historian. It is as much a product of their personal biography and the social formation in which they live as of the evidence used in its construction. Even this evidence is the product of other personal biographies and other social forces.

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