scholarly journals Estimation of predator-prey mass ratios using stable isotopes: sources of errors

2014 ◽  
Author(s):  
Eric Hertz ◽  
James Robinson ◽  
Marc Trudel ◽  
Asit Mazumder ◽  
Julia K Baum
Keyword(s):  
Stable Isotopes ◽  
Food Web ◽  
North Sea ◽  
Trophic Position ◽  
Trophic Levels ◽  
Environmental Stability ◽  
Food Web Structure ◽  
Predator Prey ◽  
Web Structure ◽  
Prey Mass

In aquatic systems, the ratio of predator mass to prey mass (PPMR) is an important constraint on food web structure, and has been correlated with environmental stability. One common approach of estimating PPMR uses nitrogen stable isotopes (δ15N) as an indicator of trophic position, under the assumption that the discrimination between diet and tissue is constant with increasing diet δ15N (an additive approach). However, recent studies have shown that this assumption may not be valid, and that there is a negative trend between the δ15N of the diet and the discrimination value (a scaled approach). We estimated PPMR for a simulated food web using the traditional additive approach and improved scaled approach, before testing our predictions with isotope samples from a North Sea food web. Our simulations show that the additive approach gives incorrect estimates of PPMR, and these biases are reflected in North Sea PPMR estimates. The extent of the bias is dependent on the baseline δ15N and trophic level sampled, with the greatest differences for samples with low baseline δ15N sampled at lower trophic levels. The scaled approach allows for the comparison of PPMR across varying δ15N baselines and trophic levels, and will refine estimates of PPMR.

scholarly journals Estimation of predator-prey mass ratios using stable isotopes: sources of errors

2014 ◽  
Author(s):  
Eric Hertz ◽  
James Robinson ◽  
Marc Trudel ◽  
Asit Mazumder ◽  
Julia K Baum
Keyword(s):  
Stable Isotopes ◽  
Food Web ◽  
North Sea ◽  
Trophic Position ◽  
Trophic Levels ◽  
Environmental Stability ◽  
Food Web Structure ◽  
Predator Prey ◽  
Web Structure ◽  
Prey Mass

In aquatic systems, the ratio of predator mass to prey mass (PPMR) is an important constraint on food web structure, and has been correlated with environmental stability. One common approach of estimating PPMR uses nitrogen stable isotopes (δ15N) as an indicator of trophic position, under the assumption that the discrimination between diet and tissue is constant with increasing diet δ15N (an additive approach). However, recent studies have shown that this assumption may not be valid, and that there is a negative trend between the δ15N of the diet and the discrimination value (a scaled approach). We estimated PPMR for a simulated food web using the traditional additive approach and improved scaled approach, before testing our predictions with isotope samples from a North Sea food web. Our simulations show that the additive approach gives incorrect estimates of PPMR, and these biases are reflected in North Sea PPMR estimates. The extent of the bias is dependent on the baseline δ15N and trophic level sampled, with the greatest differences for samples with low baseline δ15N sampled at lower trophic levels. The scaled approach allows for the comparison of PPMR across varying δ15N baselines and trophic levels, and will refine estimates of PPMR.

scholarly journals Effects of ontogeny and invasive crayfish on feeding ecology and mercury concentrations of predatory fishes

2019 ◽  
Vol 76 (11) ◽  
pp. 1929-1939 ◽  
Author(s):  
Kate Prestie ◽  
Iain D. Phillips ◽  
Douglas P. Chivers ◽  
Timothy D. Jardine
Keyword(s):  
Invasive Species ◽  
Food Web ◽  
Littoral Zone ◽  
Trophic Position ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Web Structure ◽  
Top Predators ◽  
Invasive Crayfish ◽  
Predatory Fishes

Lake food web structure dictates the flow of energy and contaminants to top predators, and addition of invasive species can shift these flows. We examined trophic position (TP), proportional reliance on the littoral zone (Proplittoral), and mercury (Hg) concentrations across the life-span of two predatory fishes, walleye (Sander vitreus) and northern pike (Esox lucius), in lakes with and without invasive virile crayfish (Faxonius virilis). The littoral zone was the dominant foraging zone for both species regardless of size, accounting for 59% and 80% of the diet of walleye and pike, respectively. Both species increased in TP and Hg with body size, as did crayfish. Walleye in crayfish-present lakes had lower Proplittoral, TP, and Hg concentrations compared with non-present lakes, but trophic magnification of Hg through the food web was consistent across all six lakes. These findings underscore a strong role for the littoral zone in channeling energy and contaminants to higher trophic levels and how invasive species can occupy new habitats at low abundance while altering food web structure and contaminant bioaccumulation.

scholarly journals Biomarkers in Ringed Seals Reveal Recent Onset of Borealization in the High- Compared to the Mid-Latitude Canadian Arctic

2021 ◽  
Vol 8 ◽  
Author(s):  
Camille de la Vega ◽  
Claire Mahaffey ◽  
David J. Yurkowski ◽  
Louisa Norman ◽  
Elysia Simpson ◽  
...  
Keyword(s):  
Food Web ◽  
Trophic Position ◽  
Canadian Arctic ◽  
High Arctic ◽  
Trophic Levels ◽  
The Arctic ◽  
Food Web Structure ◽  
Web Structure ◽  
Ringed Seals ◽  
Ecological Changes

Warming of the Arctic has resulted in environmental and ecological changes, termed borealization, leading to the northward shift of temperate species. Borealization has occurred across all trophic levels, altering the structure of the food web. The onset and rate of borealization likely varies with latitude, depending on local warming and advection of warmer water into the Arctic. In order to assess latitudinal trends in food web structure in the Arctic, we analyzed stable nitrogen isotopes of specific amino acids alongside bulk stable carbon isotopes in ringed seal muscle tissue from the Canadian Arctic Archipelago (high-Arctic) and Southern Baffin Bay (mid-Arctic) from 1990 to 2016. Our results indicate a shift in food web structure in the high-Arctic that has occurred more recently when compared with the mid-Arctic. Specifically, over the past 25 years, the trophic position of ringed seals from the mid-Arctic was largely constant, whereas the trophic position of ringed seals decreased in the high-Arctic, reaching similar values observed in the mid-Arctic in 2015–2016. This suggests a potential shortening of the food chain length in the high-Arctic, possibly driven by changes in zooplankton communities feeding complexity in association with sea ice decline. This study identifies a temporal offset in the timing of borealization in the Canadian Arctic, resulting in different response of food webs to ecological changes, depending on latitude.

Decrease in diatom dominance at lower Si:N ratios alters plankton food webs

2020 ◽  
Vol 42 (4) ◽  
pp. 411-424
Author(s):  
Kriste Makareviciute-Fichtner ◽  
Birte Matthiessen ◽  
Heike K Lotze ◽  
Ulrich Sommer
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Phytoplankton Community ◽  
Plankton Community ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Web Structure ◽  
Copepod Grazing ◽  
Important Food Source

Abstract Many coastal oceans experience not only increased loads of nutrients but also changes in the stoichiometry of nutrient supply. Excess supply of nitrogen and stable or decreased supply of silicon lower silicon to nitrogen (Si:N) ratios, which may decrease diatom proportion in phytoplankton. To examine how Si:N ratios affect plankton community composition and food web structure, we performed a mesocosm experiment where we manipulated Si:N ratios and copepod abundance in a Baltic Sea plankton community. In high Si:N treatments, diatoms dominated. Some of them were likely spared from grazing unexpectedly resulting in higher diatom biomass under high copepod grazing. With declining Si:N ratios, dinoflagellates became more abundant under low and picoplankton under high copepod grazing. This altered plankton food web structure: under high Si:N ratios, edible diatoms were directly accessible food for copepods, while under low Si:N ratios, microzooplankton and phago-mixotrophs (mixoplankton) were a more important food source for mesograzers. The response of copepods to changes in the phytoplankton community was complex and copepod density-dependent. We suggest that declining Si:N ratios favor microzoo- and mixoplankton leading to increased complexity of planktonic food webs. Consequences on higher trophic levels will, however, likely be moderated by edibility, nutritional value or toxicity of dominant phytoplankton species.

scholarly journals Food web structure in a double-basin ultra-oligotrophic lake in Northwest Patagonia, Argentina, using carbon and nitrogen stable isotopes

Limnologica ◽  
2013 ◽  
Vol 43 (2) ◽  
pp. 131-142 ◽  
Author(s):  
Marina Arcagni ◽  
Linda M. Campbell ◽  
María Angélica Arribére ◽  
Kurt Kyser ◽  
Kerry Klassen ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Food Web ◽  
Oligotrophic Lake ◽  
Nitrogen Stable Isotopes ◽  
Food Web Structure ◽  
Carbon And Nitrogen ◽  
Web Structure

scholarly journals Benthic biodiversity and food web structure in the European sector of the Arctic Ocean during spring time

2018 ◽  
Author(s):  
Barbara Oleszczuk ◽  
Katarzyna Grzelak ◽  
Monika Kędra
Keyword(s):  
Sea Ice ◽  
Food Web ◽  
Barents Sea ◽  
Benthic Communities ◽  
Trophic Levels ◽  
The Arctic ◽  
Feeding Guild ◽  
Food Web Structure ◽  
Web Structure ◽  
Ice Conditions

Arctic marine ecosystems are currently facing sea ice decrease. Changes in the sea ice cover will influence the Organic Matter (OM) fluxes to the bottom and thus benthic communities. We aimed to examine meio- and macrobenthic biodiversity and community structure, and food web, with use of stable isotopes of carbon (δ13C) and nitrogen (δ15N), in relation to depth, sea ice type, and bloom stage. Benthic samples were collected in Svalbard area during spring time in 2015 and 2016 along with samples of particulate and sediment OM. Svalbard fjords, Storfjorden, Barents Sea shelf, continental slope, and Nansen Basin were characterized by different environmental settings including various sea ice conditions, bloom stage, sediment OM and particulate OM in bottom water. The highest biodiversity and biomass were found at the shelf and slope stations where intensive bloom was observed and was related to higher concentrations of fresh, high-quality OM. Low benthic infaunal diversity, abundance, and biomass were noted in fjords and deep stations where quality and quantity of OM was markedly lower. Deposit feeders were the only feeding guild sampled in the deep stations while at other stations 3-4 trophic levels were found.

Impacts of macrozoobenthic invasions on a temperate coastal food web

2020 ◽  
Vol 653 ◽  
pp. 19-39
Author(s):  
AS Jung ◽  
HW van der Veer ◽  
CJM Philippart ◽  
AM Waser ◽  
BJ Ens ◽  
...  
Keyword(s):  
Food Web ◽  
Native Species ◽  
Wadden Sea ◽  
Marine Species ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Total Consumption ◽  
Predator Prey ◽  
Carbon Transfer ◽  
The Impact

Invasions of marine species are changing coastal food webs worldwide, impacting on trophic interactions between native species (e.g. predator-prey relationships). Here, the impact of 3 macrozoobenthic invasive species on food web structure and functioning at Balgzand (western Wadden Sea) is quantified by using ecological network analysis (ENA). The bivalves Ensis leei and Magallana gigas were observed for the first time in 1984 and 2001, respectively, and the polychaete Marenzelleria viridis appeared in 1989. Although E. leei and M. viridis reached similar peak biomasses in the 2000s (ca. 1700 and 2000 mg C m-2, respectively), the bivalve consumption was higher (>45% of total consumption) than that of the polychaete (<10%). Biomass and impact of M. gigas remained relatively low. E. leei occupied an ecological niche that was relatively unoccupied, which led to competitive advantage with respect to other suspension feeders. Increasing biomass of E. leei coincided with a 70% increase of trophic carbon transfer from primary to secondary producers and an 80% increase from secondary producers to detritus. Carbon flows from secondary producers to higher trophic levels were reduced by more than 60%. These shifts in trophic transfer were stronger than those observed during the invasion of M. gigas in the NE Wadden Sea. At Balgzand, biomass of M. gigas and M. viridis rapidly declined to low values in the 2010s, implying a temporally limited impact. In the 2010s, E. leei was still responsible for 30% of the total consumption in the 2010s, indicating a longer-term impact.

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 Preliminary examination of food web structure of Nicola Lake (Taim Hydrological System, south Brazil) using dual C and N stable isotope analyses

2006 ◽  
Vol 4 (2) ◽  
pp. 279-284 ◽  
Author(s):  
Alexandre M. Garcia ◽  
David J. Hoeinghaus ◽  
João P. Vieira ◽  
Kirk O. Winemiller ◽  
David M. L. Motta Marques ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Food Web ◽  
Biological Diversity ◽  
Isotope Analysis ◽  
Carbon Sources ◽  
Stable Isotope Ratio ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Web Structure ◽  
Hydrological System

Taim Ecological Reserve is located within the Taim Hydrological System and was created to protect a heterogeneous and productive landscape harboring exceptional biological diversity in southern Brazil. Using stable isotope ratio analyses of carbon (delta13C) and nitrogen (delta15N), we provide a preliminary description of the food web structure, including estimates of production sources supporting fish populations and vertical trophic structure, within a representative lake of this system. A total of 21 organisms (5 macrophytes, 3 mollusks and 13 adult fishes) representing 16 species were collected for isotope analysis. Fishes had delta13C values ranging from -24.30º/oo to -28.31º/oo , showing concordance with the range of values observed for macrophytes (-25.49 to -27.10º/oo), and suggesting that these plants could be a major carbon source supporting these fishes. delta13C signatures of Corbicula (-30.81º/oo) and Pomacea (-24.26º/oo) indirectly suggest that phytoplankton and benthic algae could be alternative carbon sources for some consumers. Nitrogen isotope ratios indicated approximately three consumer trophic levels. The pearl cichlid Geophagus brasiliensis was a primary consumer. Two catfishes (Trachelyopterus lucenai and Loricariichthys anus) were secondary consumers. Two congeneric pike cichclids (Crenicichla lepidota and C. punctata), a catfish (Pimelodus maculatus) and the characids Astyanax fasciatus and Oligosarcus robustus were tertiary consumers. Further studies including additional primary producers and consumers and greater sample numbers should be conducted to provide a more complete and detailed description of food web structure and dynamics within the reserve.

Distribution and burdens of bioaccumulative contaminants in the Lake Erie food web: A review

2003 ◽  
Vol 11 (3) ◽  
pp. 141-160 ◽  
Author(s):  
Sarah B Gewurtz ◽  
Miriam L Diamond
Keyword(s):  
Food Web ◽  
Exotic Species ◽  
Organic Contaminants ◽  
Lake Erie ◽  
Trophic Levels ◽  
Algal Toxins ◽  
Food Web Structure ◽  
Chemical Contaminants ◽  
Web Structure ◽  
Internal Distribution

The bioaccumulation of organic contaminants in the Lake Erie food web is reviewed in context of the numerous changes experienced by the system. In the late 1960s, internal lake processes, related to the eutrophic status of the lake, minimized contaminant bioaccumulation despite high contaminant loadings. From the 1970s to 1980s contaminant concentrations decreased at different rates in many species of different trophic levels, coincident with decreased loadings to the lake. Since the early 1980s contaminant concentrations in biota have not changed consistently. Several factors have been proposed to account for these patterns, including reduced nutrient loadings and productivity, and the invasion of several exotic species such as zebra mussels. These factors have altered the food web structure and the internal distribution of contaminants in the lake. Emerging and continuing issues, such as climate change, invasions of additional exotic species, new chemical contaminants of concern, and algal toxins will likely impact contaminant dynamics in the future.Key words: Lake Erie, bioaccumulative contaminants, food web.

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