Lake Pocotopaug Lake and Watershed Restoration Evaluation ...

Phytoplankton samples were collected by filling a 6-m long, ¾ inch diameter plastic tube withlake water. The tube is immersed vertically, with a terminal weight maintaining the tube verticalposition throughout the water column. When the tube is full, the top end is sealed, the bottomend is retrieved and the content is emptied in a container. The water sample collected this wayis a composite sample of the water column from the surface to the length of the tube (~ 6 m inthis case). Because most of the phytoplankton community lives in the upper water layers of alake, samples collected this way were representative of the open-water algal community. Thecollected planktonic algae were preserved by addition of a few milliliters of Lugol’s solution.Taxonomic identification and algal counts (density and biomass) were performed by an ENSRtaxonomist, and served as the basis for an expanded ecological discussion of phytoplankton(including community structure, relative abundances, species richness, diversity, and evenness)as related to water quality and other biological components of Lake Pocotopaug. Samples wereconcentrated and the concentrate was viewed in a counting chamber under phase contrastoptics at 400X power. Algae were identified, sized and enumerated, and a computer programconverted the raw data to density, either as cells/ml or biomass (µg/L).Zooplankton were collected by means of a 53-µm mesh, funnel-shaped plankton net loweredthrough the water column to a depth of ~10 m, and slowly retrieved up to the water surface.The procedure was repeated at least three times for each sample, yielding a concentratedsample of almost 1000 L of lake water. The collected zooplankton were preserved by additionof a few drops of 25% glutaraldehyde solution.Taxonomic identification and organism counts (density and biomass) were performed by anENSR taxonomist, and served as the basis for an expanded ecological discussion ofzooplankton (including community structure, relative abundance, size distribution, speciesrichness, diversity, and evenness) as related to water quality and other biological components ofLake Pocotopaug. Samples were concentrated and the concentrate was viewed in a countingchamber under brightfield optics at 100X power. Zooplankton were identified, sized andenumerated, and a computer program converted the raw data to density, either as individuals/Lor biomass (µg/L).Lake Pocotopaug Restoration Evaluation 26May 2002