Food-Web Structure in Relation to Environmental Gradients and Predator-Prey Ratios in Tank-Bromeliad Ecosystems

There is an urgent need to understand how food web structure changes along environmental gradients. In this study we investigated changes in trophic organisation and the relative importance of autotrophic sources sustaining fish assemblages along a transect from river to ocean. In order to address these topics, we analysed fish stomach contents and isotopic composition of consumers and food sources. The findings revealed a greater number of autotrophic sources sustaining fish assemblages in the continental systems (especially in the river) than in the adjacent marine system. Bipartite networks depicting trophic relationships between fish and prey also changed along the transect, showing comparatively higher complexity in the estuary. These findings could be explained by the greater number of food web components (autotrophic sources, fish trophic guilds and prey) associated with pelagic and benthic food chains within the estuary compared with the adjacent systems studied. The findings of this study highlight the need to take into account river-to-ocean changes in food web structure of fish assemblages in management plans to mitigate human impacts in coastal systems.

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Light-driven synchrony ofProchlorococcusgrowth and mortality in the subtropical Pacific gyre

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1424279112 ◽

2015 ◽

Vol 112 (26) ◽

pp. 8008-8012 ◽

Cited By ~ 59

Author(s):

Francois Ribalet ◽

Jarred Swalwell ◽

Sophie Clayton ◽

Valeria Jiménez ◽

Sebastian Sudek ◽

...

Keyword(s):

Food Web ◽

Mortality Rates ◽

Open Ocean ◽

Food Web Structure ◽

Predator Prey ◽

Cell Production ◽

Web Structure ◽

Cell Mortality ◽

Coexisting Species ◽

Winter Time

Theoretical studies predict that competition for limited resources reduces biodiversity to the point of ecological instability, whereas strong predator/prey interactions enhance the number of coexisting species and limit fluctuations in abundances. In open ocean ecosystems, competition for low availability of essential nutrients results in relatively few abundant microbial species. The remarkable stability in overall cell abundance of the dominant photosynthetic cyanobacteriumProchlorococcusis assumed to reflect a simple food web structure strongly controlled by grazers and/or viruses. This hypothesized link between stability and ecological interactions, however, has been difficult to test with open ocean microbes because sampling methods commonly have poor temporal and spatial resolution. Here we use continuous techniques on two different winter-time cruises to show thatProchlorococcuscell production and mortality rates are tightly synchronized to the day/night cycle across the subtropical Pacific Ocean. In warmer waters, we observed harmonic oscillations in cell production and mortality rates, with a peak in mortality rate consistently occurring ∼6 h after the peak in cell production. Essentially no cell mortality was observed during daylight. Our results are best explained as a synchronized two-component trophic interaction with the per-capita rates ofProchlorococcusconsumption driven either directly by the day/night cycle or indirectly byProchlorococcuscell production. Light-driven synchrony of food web dynamics in which most of the newly producedProchlorococcuscells are consumed each night likely enforces ecosystem stability across vast expanses of the open ocean.

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

10.7287/peerj.preprints.544 ◽

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.

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Invertebrate predator-prey body size relationships: an explanation for upper triangular food webs and patterns in food web structure?

Oecologia ◽

10.1007/bf00379364 ◽

1987 ◽

Vol 74 (2) ◽

pp. 231-235 ◽

Cited By ~ 143

Author(s):

P. H. Warren ◽

J. H. Lawton

Keyword(s):

Body Size ◽

Food Web ◽

Food Webs ◽

Food Web Structure ◽

Predator Prey ◽

Web Structure ◽

Invertebrate Predator

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Inferring food web structure from predator-prey body size relationships

Methods in Ecology and Evolution ◽

10.1111/2041-210x.12103 ◽

2013 ◽

Vol 4 (11) ◽

pp. 1083-1090 ◽

Cited By ~ 100

Author(s):

Dominique Gravel ◽

Timothée Poisot ◽

Camille Albouy ◽

Laure Velez ◽

David Mouillot

Keyword(s):

Body Size ◽

Food Web ◽

Food Web Structure ◽

Predator Prey ◽

Web Structure

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Temperature alters food web body-size structure

Biology Letters ◽

10.1098/rsbl.2014.0473 ◽

2014 ◽

Vol 10 (8) ◽

pp. 20140473 ◽

Cited By ~ 29

Author(s):

Jean P. Gibert ◽

John P. DeLong

Keyword(s):

Body Size ◽

Food Web ◽

Size Structure ◽

Large Body ◽

Effect Of Temperature ◽

Food Web Structure ◽

Predator Prey ◽

Marine Predator ◽

Web Structure ◽

Predator Size

The increased temperature associated with climate change may have important effects on body size and predator–prey interactions. The consequences of these effects for food web structure are unclear because the relationships between temperature and aspects of food web structure such as predator–prey body-size relationships are unknown. Here, we use the largest reported dataset for marine predator–prey interactions to assess how temperature affects predator–prey body-size relationships among different habitats ranging from the tropics to the poles. We found that prey size selection depends on predator body size, temperature and the interaction between the two. Our results indicate that (i) predator–prey body-size ratios decrease with predator size at below-average temperatures and increase with predator size at above-average temperatures, and (ii) that the effect of temperature on predator–prey body-size structure will be stronger at small and large body sizes and relatively weak at intermediate sizes. This systematic interaction may help to simplify forecasting the potentially complex consequences of warming on interaction strengths and food web stability.

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Food‐web structure varies along environmental gradients in a high‐latitude marine ecosystem

Ecography ◽

10.1111/ecog.03443 ◽

2018 ◽

Vol 42 (2) ◽

pp. 295-308 ◽

Cited By ~ 25

Author(s):

Susanne Kortsch ◽

Raul Primicerio ◽

Michaela Aschan ◽

Sigrid Lind ◽

Andrey V. Dolgov ◽

...

Keyword(s):

Food Web ◽

High Latitude ◽

Environmental Gradients ◽

Marine Ecosystem ◽

Food Web Structure ◽

Web Structure

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Pelagic Food Web Structure in Adirondack Mountain, USA, Lakes of Varying Acidity

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f93-017 ◽

1993 ◽

Vol 50 (1) ◽

pp. 149-155 ◽

Cited By ~ 15

Author(s):

Karl E. Havens

Keyword(s):

Food Web ◽

Adirondack Mountains ◽

Food Web Structure ◽

Predator Prey ◽

Web Structure ◽

Pelagic Food Web ◽

Softwater Lakes ◽

Ph Toxicity ◽

Adirondack Mountain ◽

Food Web Complexity

Pelagic food web models were constructed for 50 softwater lakes of varying acidity (pH 4.17–7.32) in the Adirondack Mountains, and relationships between food web parameters and several abiotic variables (pH, monomeric Al, dissolved organic carbon (DOC), zmax, and area) were quantified. With declining pH, pelagic food web complexity was reduced, as the number of species, links, links per species, predator generalization, and prey vulnerability all declined. The declines were less pronounced in lakes having high DOC levels. Some web parameters, including the predator/prey ratio, the portion of basal, intermediate and top species, and species redundancy, did not decline with pH but were more variable among the acid lakes. Those trends are consistent with the view that at low pH, toxicity becomes the major factor controlling community structure.

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