THE PROTOZOAN-METAZOAN TROPHIC LINK IN PELAGIC ECOSYSTEMS

The evidence for a qualitatively and quantitatively important trophic link between planktonic Protozoa and higher order metazoan consumers is reviewed. The available data are obtained primarily, but not exclusively, from laboratory studies of calanoid copepod consumers and tintinnid ciliate prey from marine estuarine and nearshore environments. The data indicates that the protozoan-metazoan link is of similar magnitude and importance in the pelagic ecosystems of freshwaters. It is proposed that planktonic Protozoa constitute a high quality, nitrogen-rich food in the diets of their metazoan consumers. Implications of the trophic link to the consumers, prey, and ecosystem are discussed.