The research investigates the specific aspects of algal food quality that affect feeding and fecundity of herbivores. While the physiological condition of the algae is a critical factor influencing ingestion rates and reproduction, biochemical components of the algae are frequently not characterized or controlled. To test the hypothesis that the major cellular constituents of algae vary with different limiting resources (N, P, Si, light), the PIs will assess patterns of biochemical components over a range of growth rates in three species of algae grown in continuous cultures, under various resource limitations. To test whether algal biochemical composition affects the feeding and reproductive rates of herbivores, the PIs will measure fecundity of Daphnia pulicaria with the various diets. To assess if seasonal variation in lipid production reflects changes in the quality of phytoplankton, the PIs will monitor seasonal fluctuations of lipids in algae and zooplankton in three lakes across a trophic gradient. Food quality in aquatic ecosystems is highly dynamic. The aim is to identify the general patterns of accommodation of algae and herbivores to the variable resource base.
