Trophic Interactions and Food Web Stability -- As a postdoctoral scholar with Dr. Michael Vanni, I obtained NSF funds to examine how omnivorous gizzard shad affect the resistance and resilience of aquatic food webs to nutrient perturbations. Recent theoretical studies suggest that omnivory confers stability to food webs through the addition of trophic interactions, but empirical studies are needed to test predictions generated by this hypothesis. Reservoirs are excellent study systems for such tests. Allochthonous material enters reservoirs from landscapes following storm events, supplying large, discrete pulses of nutrients. These perturbations can cause rapid shifts in food-web structure, especially affecting phytoplankton producers and zooplankton herbivores. The gizzard shad is an especially important component of reservoir food webs; by feeding on sedimented detritus and subsequently excreting sediment-derived nutrients, individuals of this abundant fish species transport nutrients to the pelagic food web. Such transport of nutrients, which otherwise would be unavailable to the grazer-based food web, represents a large, steady supply. Theory indicates that a large, steady supply of limiting nutrients can confer stability to food webs, suggesting another mechanism by which these omnivorous fish could stabilize food webs. Using modeling, pond experiments, and ecosystem monitoring, the preliminary results of this ongoing research support the hypothesis that gizzard shad confer stability. We are currently attempting to elucidate the underlying mechanism responsible for observed increases in resistance and resilience. This research integrates several important issues, including how food-web structure affects stability, how omnivory influences patterns of nutrient cycling, and how grazing- and detritus-based food chains are functionally linked. Results may enhance the management of reservoirs for water quality and recreational use by providing insight into how these systems respond to accidental or intentional changes in food-web structure and nutrient-loading rates. In the future, I hope to expand my research of the relationship between trophic interactions and ecosystem stability into other systems where omnivores and detritivores are important components of food webs, such as in streams, estuaries, and soils.