SUMMER ABUNDANCE AND ACTIVITIES OF BACTERIA IN THE FRESH-WATER LAKES OF SCHIRMACHER-OASIS, ANTARCTICA

Bacterial biomass and heterotrophic potential (using C-14-labeled gluc ose, glutamic acid and sodium acetate) of water, ice and sediment micr obial populations were studied from different lakes of the Schirmacher Oasis, Antarctica. Epifluorescence counts of total bacteria in these lakes were observed to be lower by a factor when compared to some of t he ultraoligotrophic Antarctic lakes. Biovolumes of bacteria from diff erent samples did not show significant variations, suggesting that reg ulatory factors were oligotrophy and low temperatures rather than micr ozoan grazing. Microbial uptake rates of glutamic acid were generally the fastest, followed by glucose and/or sodium acetate in the lakewate r samples. The mean values of V-max cell(-1) for glutamic acid, sodium acetate and glucose were 3.81, 0.91 and 0.71 pg C h(-1). Results of t his study are potentially useful in recognizing the relative abundance and activity of limnetic microbial populations in the Schirmacher Oas is during summer - the active period of microbial growth - and for com paring their activities with other ecosystems elsewhere in continental Antarctica.