North Temperate Lakes LTER: Phytoplankton - Trout Lake Area 1984 - current

Phytoplankton samples from the seven northern Wisconsin LTER lakes in the Trout Lake
area (Allequash, Big Muskellunge, Crystal, Sparkling, and Trout lakes and bog lakes 27-02
[Crystal Bog], and 12-15 [Trout Bog]) are collected six times per year at the deep hole
sampling station at the same time as our other limnological sampling is conducted. We use a
peristaltic pump and tubing, collecting a separate sample from the epilimnion, metalimnion
and hypolimnion for most of the lakes. For 27-2 Bog Lake, which is only 2m deep, we collect
one 0-2m composite sample. The samples are preserved with Lugols iodine solution. We create
a single hypsometrically pooled composite sample per lake from subsamples of the strata
samples. The pooled samples are sent to PhycoTech, Inc., a private lab specializing in
phytoplankton analysis, to be made into permanent slide mounts. The slide mounts, 3 slides
per sample, are archived at the University of Wisconsin - Madison Zoology Museum
Phytoplankton are identified to species using an inverted microscope (Utermohl technique)
and are reported as natural unit (i.e., colonies, filaments, or single cells) densities per
mL, cell densities per mL, and algal biovolume densities per mL. Multiple entries for the
same species on the same date may be due to different variants or vegetative states - (e.g.,
colonial or attached vs. free cell.) Biovolumes for individual cells of each species are
determined during the counting procedure by obtaining cell measurements needed to calculate
volumes for geometric solids (e.g., cylinders, spheres, truncated cones) corresponding to
actual cell shapes. Biovolume concentrations are then computed by mulitplying the average
cell biovolume by the cell densities in the water sample. Note that one million
cubicMicrometers of biovolume PerMilliliter of water are equal to a biovolume concentration
of one cubicMillimeterPerMilliliter. Assuming a cell density equal to water, a
cubicMillimeterPerMilliliter of biovolume converts to a biomass concentration of one
milligramPerLiter. Sampling Frequency: 6 samples per year Number of sites: 7