Using automated overwinter sampling devices, we collected preserved phytoplankton samples from multiple depths in Lake Fryxell, a permanently ice-covered lake in southern Victoria Land, Antarctica. Photosynthetic algae were maintained in a stable water column throughout winter darkness. The algal taxa overwintered in different ways in a species-specific manner. Typical vegetative cells were the most abundant form for all species found in the water column. Populations of one chlorophyte, Stichococcus sp., were observed in winter, but the species was absent in both summers.
Ice thickness was measured from the bottom of the ice cover to the piezometric water level and to the top of the ice cover. Because most limnological sampling holes are drilled in low-lying areas, it was thought that ice thickness measurements were biased. Therefore, random ice thickness measurements were performed in a 1000 m^2 sampling grid on each lake in past years. Statistical analyses by Dr. Priscu have shown that measurements from three ice holes are representative of the ice thickness measured by this grid system.