Experimental Studies of Food Webs: Causes and Consequences of Trophic Interactions

Trophic levels can be applied to describe the ecological role of organisms in food webs and assess changes in ecosystems. Stable isotopes analysis can assist in the understanding of trophic interactions and use of food resources by aquatic organisms. The local ecological knowledge (LEK) of fishers can be an alternative to advance understanding about fish trophic interactions and to construct aquatic food webs, especially in regions lacking research capacity. The objectives of this study are: to calculate the trophic levels of six fish species important to fishing by combining data from stable isotopes analysis and fishers’ LEK in two clear water rivers (Tapajós and Tocantins) in the Brazilian Amazon; to compare the trophic levels of these fish between the two methods (stable isotopes analysis and LEK) and the two rivers; and to develop diagrams representing the trophic webs of the main fish prey and predators based on fisher’s LEK. The fish species studied were Pescada (Plagioscion squamosissimus), Tucunaré (Cichla pinima), Piranha (Serrasalmus rhombeus), Aracu (Leporinus fasciatus), Charuto (Hemiodus unimaculatus), and Jaraqui (Semaprochilodus spp.). A total of 98 interviews and 63 samples for stable isotopes analysis were carried out in both rivers. The average fish trophic levels did not differ between the stable isotopes analysis and the LEK in the Tapajós, nor in the Tocantins Rivers. The overall trophic level of the studied fish species obtained through the LEK did not differ from data obtained through the stable isotopes analysis in both rivers, except for the Aracu in the Tapajós River. The main food items consumed by the fish according to fishers’ LEK did agree with fish diets as described in the biological literature. Fishers provided useful information on fish predators and feeding habits of endangered species, such as river dolphin and river otter. Collaboration with fishers through LEK studies can be a viable approach to produce reliable data on fish trophic ecology to improve fisheries management and species conservation in tropical freshwater environments and other regions with data limitations.

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Resolving Food-Web Structure

Annual Review of Ecology Evolution and Systematics ◽

10.1146/annurev-ecolsys-110218-024908 ◽

2020 ◽

Vol 51 (1) ◽

pp. 55-80

Author(s):

Robert M. Pringle ◽

Matthew C. Hutchinson

Keyword(s):

Food Web ◽

Food Webs ◽

Trophic Interactions ◽

Sampling Methods ◽

Taxonomic Resolution ◽

Major Focus ◽

Web Data ◽

Food Web Structure ◽

Web Structure ◽

Abundant Evidence

Food webs are a major focus and organizing theme of ecology, but the data used to assemble them are deficient. Early debates over food-web data focused on taxonomic resolution and completeness, lack of which had produced spurious inferences. Recent data are widely believed to be much better and are used extensively in theoretical and meta-analytic research on network ecology. Confidence in these data rests on the assumptions ( a) that empiricists correctly identified consumers and their foods and ( b) that sampling methods were adequate to detect a near-comprehensive fraction of the trophic interactions between species. Abundant evidence indicates that these assumptions are often invalid, suggesting that most topological food-web data may remain unreliable for inferences about network structure and underlying ecological and evolutionary processes. Morphologically cryptic species are ubiquitous across taxa and regions, and many trophic interactions routinely evade detection by conventional methods. Molecular methods have diagnosed the severity of these problems and are a necessary part of the cure.

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Reconstructing hyperdiverse food webs: Gut content metabarcoding as a tool to disentangle trophic interactions on coral reefs

Methods in Ecology and Evolution ◽

10.1111/2041-210x.13206 ◽

2019 ◽

Vol 10 (8) ◽

pp. 1157-1170 ◽

Cited By ~ 16

Author(s):

Jordan M. Casey ◽

Christopher P. Meyer ◽

Fabien Morat ◽

Simon J. Brandl ◽

Serge Planes ◽

...

Keyword(s):

Coral Reefs ◽

Food Webs ◽

Trophic Interactions ◽

Gut Content

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Food Chains and Food Webs in Aquatic Ecosystems

Applied Sciences ◽

10.3390/app10145012 ◽

2020 ◽

Vol 10 (14) ◽

pp. 5012

Author(s):

Ihn-Sil Kwak ◽

Young-Seuk Park

Keyword(s):

Food Webs ◽

Species Interactions ◽

Aquatic Ecosystems ◽

Empirical Studies ◽

Experimental Studies ◽

Environmental Dna ◽

Gut Contents ◽

Food Chains ◽

Energy Flows ◽

Structure Of Communities

Food chains and food webs describe the structure of communities and their energy flows, and they present interactions between species. Recently, diverse methods have been developed for both experimental studies and theoretical/computational studies on food webs as well as species interactions. They are effectively used for various applications, including the monitoring and assessment of ecosystems. This Special Issue includes six empirical studies on food chains and food webs as well as effects of environmental factors on organisms in aquatic ecosystems. They confirmed the usefulness of their methods including isotope, DNA-barcoding with gut contents, and environmental DNA for biological monitoring and ecosystem assessment.

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Trophic interactions in rockpool food webs: regulation of zooplankton and phytoplankton by Notonecta and Daphnia

Freshwater Biology ◽

10.1046/j.1365-2427.1998.00262.x ◽

1998 ◽

Vol 39 (1) ◽

pp. 79-90 ◽

Cited By ~ 32

Author(s):

Marie Arnér ◽

Sanna Koivisto ◽

Jon Norberg ◽

Nils Kautsky

Keyword(s):

Food Webs ◽

Trophic Interactions

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Trophic interactions in changing landscapes: responses of soil food webs

Basic and Applied Ecology ◽

10.1016/j.baae.2004.09.002 ◽

2004 ◽

Vol 5 (6) ◽

pp. 495-503 ◽

Cited By ~ 80

Author(s):

Katarina Hedlund ◽

Bryan Griffiths ◽

Sœren Christensen ◽

Stefan Scheu ◽

Heikki Setälä ◽

...

Keyword(s):

Food Webs ◽

Trophic Interactions ◽

Soil Food Webs

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How habitat-modifying organisms structure the food web of two coastal ecosystems

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.2326 ◽

2016 ◽

Vol 283 (1826) ◽

pp. 20152326 ◽

Cited By ~ 24

Author(s):

Els M. van der Zee ◽

Christine Angelini ◽

Laura L. Govers ◽

Marjolijn J. A. Christianen ◽

Andrew H. Altieri ◽

...

Keyword(s):

Species Richness ◽

Food Web ◽

Food Webs ◽

Trophic Interactions ◽

Trophic Levels ◽

Interaction Networks ◽

Habitat Modification ◽

Seagrass Meadows ◽

Link Density ◽

Trophic Role

The diversity and structure of ecosystems has been found to depend both on trophic interactions in food webs and on other species interactions such as habitat modification and mutualism that form non-trophic interaction networks. However, quantification of the dependencies between these two main interaction networks has remained elusive. In this study, we assessed how habitat-modifying organisms affect basic food web properties by conducting in-depth empirical investigations of two ecosystems: North American temperate fringing marshes and West African tropical seagrass meadows. Results reveal that habitat-modifying species, through non-trophic facilitation rather than their trophic role, enhance species richness across multiple trophic levels, increase the number of interactions per species (link density), but decrease the realized fraction of all possible links within the food web (connectance). Compared to the trophic role of the most highly connected species, we found this non-trophic effects to be more important for species richness and of more or similar importance for link density and connectance. Our findings demonstrate that food webs can be fundamentally shaped by interactions outside the trophic network, yet intrinsic to the species participating in it. Better integration of non-trophic interactions in food web analyses may therefore strongly contribute to their explanatory and predictive capacity.

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