Freshwater food webs: towards a more fundamental understanding of biodiversity and community dynamics

Abstract

SUMMARY1. Food webs are a powerful whole-system way to represent the patterns of biodiversity and energy flow in a readily quantifiable framework amenable to comparative analyses. Integrated theory and data on complex trophic interactions provide useful and novel ways to study ecosystem structure, dynamics, function and stability. 2. Freshwater ecology has contributed considerably to the advancement of food-web ecology. This has occurred through early application of methodological advances such as stable isotope analysis and description of some of the most detailed food webs, including Little Rock Lake and the Broadstone Stream food webs. 3. Freshwater food webs are often highly resolved, although the inclusion of components such as bacteria continues to be challenging. Characteristics of stream food webs appear to include high rates of omnivory and a strong role for body size as a structuring influence. 4. While freshwater ecology has often included landscape factors, food webs from freshwaters have most often been collected at small spatial scales. There is a need to take a landscape approach to the study of food-web dynamics in freshwater ecosystems. 5. Studies of food webs that take an experimental approach or utilise natural gradients remain rare but will be vital to untangling causative relationships between changing environmental conditions and food-web structure and dynamics. 6. Emerging directions in freshwater food-web research involve integrating individual-level variation and information on traits into food-web studies. This is allowing a growing understanding of the ways in which food webs can be used to integrate community, evolutionary and population processes into studies of biodiversity. Freshwater food webs: a brief history Darwin (1859) described species as being embedded in an 'entangled bank' of interdependent interactions, implicitly recognising the key role of food webs in understanding the diversity of species. Ecologists have long sought to characterise the complexity of the entangled bank by quantifying food webs and seeking generalities in structure and the factors that underpin them. While early studies described food webs from a range of ecosystems,

Food Web Structure in a Harsh Glacier-Fed River

“…Compared with the majority of food web studies undertaken in temperate zone rivers [30], [80], taxon richness within the Ödenwinkelkees river was consistently lower than that found in almost all other food web studies, due to the harsh glacier-fed river. Only one published web (from the French Pyrénées) had similarly low numbers of S and L but this web had low taxonomic resolution of basal taxa [31] and is therefore not directly comparable to our webs where we attempted to resolve the diatoms as far as possible.…”

Variation partitioning of diatom species data matrices: Understanding the influence of multiple factors on benthic diatom communities in tropical streams

“…Although observational studies like ours limit Table 3. the assessment of mechanism, the amount of variation explained by nutrient enrichment, organic pollution, metal pollution and hydromorphological alterations provide us with some insight into what factors determine diatom community structure and composition in tropical streams. The inclusion of biotic factors in this study was particularly relevant since it helped to improve our understanding of the potential role of biological interactions in tropical streams for which our knowledge is still limited (Thompson et al, 2012). However, the relationship between macroinvertebrate grazer abundance and diatom community composition was insignificant.…”

Extreme Climatic Events Alter Aquatic Food Webs

“…The history of food-web research in the context of environmental change, and its progression from qualitative binary approaches to the use of more sophisticated quantitative methods, has been covered elsewhere in recent reviews (e.g. Ings et al, 2009;Thompson et al, 2012). Nevertheless, a brief overview is instructive here, as much of the research conducted in our model mesocosm system mirrors these general trends (Stewart et al, 2013).…”