Seasonal Abundance of Crustacean Zooplankton and Net Plankton Biomass of Lakes Huron, Erie, and Ontario

Abstract

Crustacean zooplankton concentrations (numbers per m3) in the upper 50 m found in lakewide cruises during all or most of the seasons on lakes Ontario and Erie in 1970 and on Lake Huron in 1971 showed that the species of zooplankton crustaceans present in the three lakes were generally identical, although the times of maxima and relative species compositions differed. Calanoid copepods were most abundant and diverse in Lake Huron and western Lake Erie. Cyclopoids and cladocerans were most abundant in lakes Erie and Ontario and in the Saginaw Bay region of Lake Huron. The most abundant cyclopoid throughout the year in all three lakes was Diacyclops bicuspidatus thomasi; Tropocyclops prasinus and Acanthocyclops vernalis were abundant especially in lakes Ontario and Erie, respectively. Cladocerans were most numerous in lakes Erie and Ontario. Numbers of individuals fluctuated markedly through the season with maxima in the spring or summer months in all three lakes.Biomass values (ash-free dry weight) were highest in Lake Erie, especially the Western Basin, and in Saginaw Bay of Lake Huron. Although numbers of crustaceans/m3 were much lower in Lake Huron than in Lake Ontario, net biomass values were similar. This was due to the greater size and average weight of crustaceans in Lake Huron samples. Inshore waters of lakes Ontario and Huron and all three basins of Lake Erie were subject to greater fluctuations in concentrations of crustacean zooplankton and net biomass values than in the pelagic waters of lakes Ontario and Huron.