90 
Michael A. Mallin 
MATERIALS AND METHODS 
Zooplankton samples were collected monthly from January 1985 
through December 1985 at two locations using a 10.5-liter Juday-style 
closing plankton trap fitted with a 75-jum mesh net. Traps have been 
found to be more efficient than nets for zooplankton samples, especially 
for smaller forms (Kankaala 1984). The 75-/im mesh is more efficient 
than a larger size for capturing microzooplankton (Evans and Sell 
1985). Station 6B was a midreservoir station over deep water (10 m), 
and Station 6C was a near-shore station in about 1 m of water. Three 
replicate samples were taken at each station at about the 0.5-m depth. 
Samples were field preserved with formalin to 2% of volume. 
In the laboratory the samples were mixed, and an aliquot containing 
at least 100 organisms was removed and placed in a circular counting 
chamber. Copepods, cladocerans, rotifers, and protozoans were counted 
using a dissecting microscope and identified to the lowest practical 
taxon using a compound microscope. Taxonomic keys included Pennak 
(1953), Brooks (1957, 1959), Voigt (1951), Edmondson (1959), and 
Wilson and Yeatman (1959). Biomass of zooplankton was determined 
using literature biomass values for piedmont reservoir zooplankton 
(Horton and Carter 1980). Biomass of species not listed was determined 
by applying dry-weight regression equations (Dumont et al. 1975) to 
specimens measured for length in the laboratory. A two-way analysis of 
variance blocked on months was used to compare various log e (X + 1) 
transformed zooplankton population density and biomass variables 
between stations. A Type I error significance level of a - 0.05 was used 
in the analyses. Densities are reported as number/ m 3 and biomass as 
mg/m 3 . Correlation analyses were run to detect linear relationships 
between water temperature and selected zooplankton and plytoplankton 
variables. 
Phytoplankton and chlorophyll a were sampled monthly at a single 
midwater station by combining whole water samples from the surface, 
Secchi depth, and twice Secchi depth. Fifty ml of field-preserved sample 
were sedimented in Utermohl settling chambers and examined for 
phytoplankton taxonomic composition and density at 400X using an 
inverted microscope. Chlorophyll a analysis was conducted spectro- 
photometrically using the method described in Strickland and Parsons 
(1972). 
Monthly surface water samples were collected and analyzed for 
nutrients and other chemical constituents by the CP&L Analytical 
Chemistry Laboratory according to standard methods (USEPA 1979, 
APHA 1981). Field measurements of water temperature, dissolved 
oxygen, pH, and conductivity were also taken on a monthly basis 
concurrent with the plankton samples. 
