Zooplankton Dynamics in a Great Lakes Coastal Marsh

Abstract

The zooplankton ecology of coastal marshes of the Laurentian Great Lakes is virtually unknown, although these systems are believed to perform important functions in the overall Great Lakes ecosystem. Thus, the composition and seasonal dynamics of the crustacean zooplankton communities of a riverine coastal marsh and the adjoining wave zone of Lake Erie were compared over 13 months. The open waters of the marsh upstream possessed a zooplankton community distinctly different from that in the wave zone, in terms of both the species composition and the population dynamics of some shared species. The downstream end of the marsh possessed a transitional zooplankton community which shared species with both the upstream marsh and wave zone communities and which had intermediate abundances of most species common to both habitats. A small summer storm runoff event briefly disrupted the development of several zooplankton populations in the marsh. Further studies are needed to identify the important factors which influence the marsh zooplankton ecology. Preliminary evidence indicates that the factors probably include planktivory by fishes and Chaoborus, aquatic macrophyte beds, a chemical and chlorophyll gradient from upstream to the lake, persistent high suspended sediments, and the flushing action of storm runoff events.