| dc.description.abstract | Composition, abundance, and distribution of zooplankton
were determined during September, 1973 to September,
1974 in the Big Eau Pleine Reservoir, a eutrophic, 2832 ha
(10.93 m^2 ) fluctuating reservoir in central Wisconsin.
Yearly water level fluctuations of up to 9.6m (31.5 ft.)
occur commonly, and maximum drawdown occurs during winter.
The yearly drawdown appeared to have little affect on the
zooplankton populations because: a) zooplankton species
composition in the Big Eau Pleine Reservoir was typical
for lakes of the Great Lakes Region, b) the mean annual
total number of 298 zooplankton per liter and biomass of
362 mg/m^3 (13.8 kg/ha) for the ice-free period of September
20 through December 1, 1973 and May 13 through September 5,
1974, were high in comparison with other bodies of water,
c) the 30-year mean annual flushing rate of 158 days is
considerably greater than that thought to be limiting to
zooplankton, and d) a winter drawdown, as in the Big Eau
Pleine Reservoir, occurs when zooplankton numbers are low
and has less affect than if it occurred during summer,
when zooplankton numbers are high.
The reservoir remained thermally unstratified except
for a brief period during late June and early July. Low
water transparency could probably be attributed to algae
blooms and suspended sediments during summer and suspended
sediments during winter. Dissolved oxygen was minimal in winter, reaching concentrations as low as 0.1 ppm in
January and February. Of 25 zooplankton taxa in the
reservoir, at least 17 were found at each of 6 sampling
sites. Copepod nauplii, Rotifera, and Chydorus sphaericus
comprised 66 to 75% of zooplankton numbers. As is typical
in other bodies of water, maximum biomass and number per
liter occurred during summer and minima during winter.
The reservoir, probably due to a lack of horizontal and
vertical thermal stratification, had little horizontal or
vertical differences in zooplankton number per liter, and
no significant horizontal differences in zooplankton
biomass. | en_US |
