Results from GLNPO's Biological Open Water Surveillance Program of the Laurentian Great Lakes 1999

INTRODUCTION

The Great Lakes National Program Office (GLNPO) of the United States Environmental Protection Agency (USEPA) has been conducting regular surveillance monitoring of the Great Lakes since 1983. 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 was initially limited to Lakes Michigan, Huron and Erie. 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.

In this report we will present results of GLNPO’s biological surveillance sampling program from all five Laurentian Great Lakes. Our goal here is to provide a general description of the offshore planktonic and the benthic communities of all five Great Lakes from GLNPO’s 1999 surveys. In addition, we will present information detailing the use of benthos data for the assessment of the ecological health of the Great Lakes.

SUMMARY

Spring phytoplankton communities in the Great Lakes were dominated by diatoms in all lakes. Biomass was highest in the western basin of Lake Erie and lowest in Lake Superior. Summer communities shifted away from diatoms, except in Lake Superior, where they remained co-dominant with chrysophytes. Dinoflagellates contributed a substantial amount of biovolume in Lake Michigan, while in communities in Lake Huron contained large populations of chrysophytes in the south and diatoms in the north. Both Lakes Erie and Ontario supported mixed communities with chlorophytes, cryptophytes and dinoflagellates all prominent.

Crustacean zooplankton communities were composed in most cases of less than a dozen species. Communities in the upper lakes contained about equal proportions of cyclopoid and calanoid copepods, in contrast to the clear dominance by calanoids in 1998. Lake Michigan exhibited marked north south differentiation in population sizes. Aside from the western basin of Lake Erie, the lower lakes were dominated by cyclopoid copepods. In summer, both Lakes Michigan and Huron supported populations of Bosmina relatively larger than were seen in 1998.

Benthos communities showed strong relationships between depth and both species richness and total abundance. The amphipod Diporeia dominated most deeper communities in the upper lakes and in Lake Ontario, while oligochaetes were most important at shallower sites. Comparison of Diporeia abundances with SOLEC criteria indicated that populations were less than desired at shallow stations in Lake Ontario and Michigan, Green Bay and Saginaw Bay. This organisms has entirely disappeared from Lake Erie. Use of an oligochaete community index classified most sites in the upper lakes as oligotrophic, all sites in Lake Erie as eutrophic, and deep and shallow sites in Lake Ontario oligotrophic and mesotrophic, respectively.

ACKNOWLEDGEMENTS

The data presented in this report was largely a result of the efforts of the following individuals: Jennifer Gronefeld, Larissa Granovski and Joseph B. Volerman (phytoplankton), Linda A. Kuhns, Lori L. Schacht and Ruth E. Little (zooplankton), and Ken K. Klubek (benthos) of Grace Analytical Lab. Their hard work and dedication is highly appreciated. Excellent graphical and analytical support was provided by Mark A. DiMartino. We would also like to express our great appreciation to captain Dave Moser and the entire crew of the R/V Lake Guardian for their assistance throughout the course of this work, and in particular the captain and crew of the Canadian Coast Guard Ship Samuel Risley for their extraordinary hospitality during the spring Lake Erie survey.

For Questions or Comments Contact: Marc Tuchman

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