9509042 Williamson Questions about what processes regulate community organization have been a central theme in ecology for a long time. With increasing evidence for important changes in abiotic factors such as climate, and UV-B radiation, our need for a better understanding of the interactions between abiotic and biotic variables in natural communities becomes crucial. While a great deal is known about the role of predation and visible light in structuring pelagic communities in lakes, the ecology of damaging short wavelength solar radiation in these pelagic communities is poorly understood. The objective of the proposed research is to investigate the role of damaging solar radiation (DSR) in zooplankton communities, and more specifically, to examine the ecological interactions between this abiotic factor and predation, an important biotic factor. Dissolved organic carbon (DOC) is the primary factor controlling attenuation of damaging solar radiation along a vertical gradient in lakes, as well as among lakes. In this study, several hypotheses will be tested regarding the interactive effects of DOC and DSR on zooplankton communities along environmental gradients in Pennsylvania and Alaska. Both field and laboratory manipulations and observations will be used to test these hypotheses. The focus on damaging solar radiation has important implications for community structure and function in aquatic ecosystems. Zooplankton provide a key link in aquatic food webs and their distribution and abundance has important implications for both water quality and energy transfer to higher trophic levels. The data collected will also permit evaluation of the relative importance of physiological versus behavioral responses of organisms to gradients of damaging solar radiation both within and among lakes.
