Dr. Deegan is interested in the relationships between ecosystem dynamics and animal populations. With the knowledge that grazing, predation and physical disturbance by animals can influence a host of processes at the ecosystem level, Dr. Deegan’s research combines the ecosystem perspective of energy and nutrient flows with traditional population and community dynamics. She is particularly interested in aquatic ecosystems because of their importance in connecting landscape elements through the flow of water and animals. She has examined problems ranging from the importance of fish in exporting nutrients and carbon from estuaries, and the effect of habitat degradation on fish community structure in coastal embayments, to the response of upper trophic levels to increased nutrients in arctic streams.