Grazing and nutrient influences of Daphnia and Eudiaptomus on phytoplankton in laboratory microcosms

In two experiments, top-down and bottom-up influences of theherbivorous crustaceans Daphnia pulicaria and Eudiaptomus grac$$$loideson phytoplankton were compared in laboratory microcosms. Ina long-term experiment (63 days), both grazers were able toestablish populations. The Daphnia population exerted strongergrazing pressure, whereas Eudiaptomus fed more selectively.Daphnia retained relatively more phosphorus (P) and thus causedalgal P limitation; with Eudiaptomus as a grazer, both nitrogen(N) and P remained limiting. In a short-term experiment (1 day),N and P release rates and algal-specific grazing rates by bothconsumers were measured. In this experiment, the increase inconcentrations of soluble mineral nutrients (