Food limitation in herbivorous zooplankton (Daphnia, Diaptomus, also rotifers and protozoa) will be assayed using a recently developed technique--amendments of natural diets by additions of custom formulated microparticles containing lipid and fatty acids or proteins of various amino acid compositions. Concurrent analyses of diet--as (1) food items ingested, (2) biochemical composition of <30 um seston, (3) nutrient- limitations of ingestable algae, and (4) dietary deficiency effects on reproduction --will contrast spring ve summer conditions of nutrient--poor vs nutrient-rich lakes. Researchers focus field and laboratory experiments on potential compensation mechanisms such as diet breadth vs selectivity, excess feeding, omnivory and vertical migration as points of contrast between a generalist grazer (Daphnia) and a more selective feeder (Diaptomus), and test the idea that the "microbial loop" is effectively though differently utilized by both strategies.
