Primary Productivity of a Hypersaline Antarctic Lake

Abstract

Although viable unicellular green algae are found in Deep Lake (a perenially ice-free hypersaline lake in Antarctica, 68� 34'S., 78� 11'E.), attempts made throughout a year to detect primary production using 14C failed. It is concluded that the rate of production in the limnetic zone does not exceed 0.15 mg C m-3 h-1. Only one positive measurement of carbon fixation was obtained: a sample collected near the bottom after the sediments had been disturbed gave a value of 0.18 mg C m-3 h-1. It was calculated that the upper limit of phytoplankton production was 3.3 g C m-1 year-1 and that total primary production could not exceed 10 g C m-2 year-1. Thus Deep Lake is one of the least productive lakes yet recorded. The combined effects of nutrient deficiency, hypersalinity, low temperatures and annual extremes in the availability of light in restricting the species diversity, population and productivity are stressed. One experiment in the nearby freshwater Watts Lake indicated a primary productivity in the limnetic zone ranging from 0.20 to 0.94 mg C m-3 h-1.