Plantonic herbivores controlled the growth of phytoplankton in the open waters of Southern Lake Huron during the late summer and fall; larger algae remained untouched during the spring diatom bloom. Over a growing season these crustaceans grazed 0.3 to 41.9% of the standing crop of phytoplankton. Immature copepods (nauplii and copepodites) were the most effective grazers. Selective grazing by crustaceans centered on nannoplankton (less then 22 micrometers), whereby 92 to 2804% of the daily productivity was grazed by large cladcerans and immature copepods. In contrast, netplankton was harvested to a much lesser degree. Laboratory experiments reinforced this picture of selective cropping. Presently in Lake Huron such selective grazing accounts for an effective biological control over algal production.

"July 1980." "Grant no. R803178." Includes bibliographical references (pages 113-114).