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Zooplankton Annual Report

The Laurentian Great Lakes constitute the largest continuous body of fresh water on earth, and with a volume of 24,620 km² (Wetzel, 1983), contain nearly 20% of the world’s unfrozen fresh water.  These lakes represent an enormous cultural and economic resource for both the United States and Canada.  Increasing population and industrial growth in recent history, however, has produced a trend of increasing eutrophication and raised concerns about declining water quality in the lakes.  As a result of these concerns, in 1972 the United States and Canada signed the Great Lakes Water Quality Agreement as an expression of each country’s commitment to restore and maintain the chemical, physical and biological integrity of the Great Lakes Basin Ecosystem.  

The Great Lakes National Program Office (GLNPO) of the United States Environmental Protection Agency (USEPA) has primary responsibility within the US for conducting surveillance  monitoring of the offshore waters of the Great Lakes.  This monitoring is intended to fulfill the provisions of the Great Lakes Water Quality Agreement (International Joint Commission, 1978) calling for periodic monitoring of the lakes to: 1) assess compliance with jurisdictional control requirements; 2) provide information on non-achievement of agreed upon water quality objectives; 3) evaluate water quality trends over time; and 4) identify emerging problems in the Great Lakes Basin Ecosystem.  The monitoring effort is focused on whole lake responses to changes in loadings of anthropogenic substances, so sampling is largely restricted to the relatively homogeneous offshore waters of each lake.  Because of the daunting logistical exigencies of sampling such a large area, temporal resolution is currently limited to two well-defined periods during the year: the spring isothermal period and the stable, stratified summer period.  

GLNPO's monitoring of the Great Lakes began in 1983, with coverage at that time including Lakes Michigan, Huron and Erie. Initially Lakes Ontario and Superior were excluded from monitoring because the former was already monitored annually by Canada, and the latter was not felt to be susceptible to eutrophication. In 1986 sampling was extended to include Lake Ontario, and in 1992 sampling of Lake Superior was added. In addition to a wide range of physical and chemical parameters, the lakes have been sampled for phytoplankton and zooplankton, including crustaceans and rotifers, since the inception of the program. In 1997, a benthic invertebrate biomonitoring program was added to complement the existing open water surveillance sampling. This sampling program is unique in that all five lakes are sampled by one agency, and samples are analyzed by one primary lab. Consequently, analytical methods, and most importantly taxonomy, remain consistent both over time and across all five lakes. 

In this report we will present, for the first time, results of GLNPO's biological surveillance sampling program from all five Laurentian Great Lakes. Our goal here is to provide a brief general description of the offshore planktonic and the benthic communities of all five Great Lakes from GLNPO's 1998 surveys.

Questions regarding this report should be directed to:
Marc Tuchman, Environmental Scientist
email: tuchman.marc@epa.gov