Whole-lake Manipulations of Food Webs and Nutrients: Benthic Community Responses and Benthic-Palagic Coupling

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Worldwide, many lakes undergo large changes in fish populations and nutrient loading. The impact of each of these common changes is well-known for pelagic communities, but poorly known for benthic communities. Furthermore, nothing is known about the interaction of fish and nutrients in structuring benthic communities, or about the impact of this interaction on benthic-pelagic coupling. This project will test the responses of benthic algae, macrophytes, and invertebrates to the three levels of fish predation and two levels of nutrients created by the Madison team. Benthic response variables will include abundance, species composition, size structure, biomass, and production of algae, macrophytes, and invertebrates. A central focus is the degree to which benthic responses to fish and nutrients will compensate for pelagic responses. A central hypothesis is that progressive fertilization will prompt a rapid, threshold shift from benthic to pelagic primary production. Without the simultaneous measurements of pelagic and benthic responses, our understanding of the response of lake dynamics to management efforts would suffer. Lakes serve as major landscape features on most continents, so the results of the research should be important for a broad array of habitats.