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
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