The ability of some freshwater and marine microalgae to ingest particulate food is a remarkable and ecologically significant behavior. Despite the important implications of this behavior for the flow of energy and nutrients in plankton communities and for the survival strategies of the algae, there has been relatively little experimental work to establish constraints on this behavior (i.e., maximum ingestion rates), to examine the potential physiological benefits to the mixotroph (e.g., acquisition of C,N, or P), or to determine the competitive advantage that this behavior might confer on the alga. This project will continue research to obtain baseline data on this important, but generally overlooked, group of free-living protists. Goals for future work are to continue to examine freshwater and marine isolates of mixotrophic algae in laboratory culture for their ability to consume particulate food. In addition, a survey of 10 lakes of varying trophic status and several environments in the North Atlantic Ocean will be conducted for the presence and abundance of mixotroph algae, and the rates of bacterial consumption by these species. Project fundings will contribute to ecological theory and the knowledge base with potential application to water pollution control.
