RUI: Food Quality Gradients and Exploitation Tradeoffs for Zooplankton in Freshwater Lakes

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DEB 9983383DeMott Abstract In both terrestrial and aquatic systems, limited knowledge of how poor food quality impacts herbivores is a major deficiency in our understanding of food chain function. Zooplankton are the dominant herbivores in the open waters of lakes and ocean, forming a key link between phytoplankton and fish. Although effects of food quality on zooplankton have been documented in laboratory experiments, evidence from nature is very limited. DeMott proposes we propose to use new techniques developed by DeMott to study natural gradients in food quality for zooplankton. Two questions will be addressed: 1) What mechanisms explain differences in food quality between stratified (deep) and unstratified (shallow) lakes and along depth and horizontal gradients within lakes? and 2) What physiological traits underlie differences in the abilities of zooplankton species to exploit food resources along these gradients. Growth and feeding experiments will be conducted at the Kellogg Biological Station, Michigan with food resources from lakes. These experiments are designed to test alternative hypotheses of food quality simultaneously, and to obtain results that can be generalized within and across lake types. The second part of the project, to be conducted at DeMott's laboratory in Indiana, will test zooplankton species along gradients of food quality using laboratory foods. This project will enhance our understanding of food chain function in the plankton and in herbivore-plant interactions in general.