The seasonal dynamics of Spirogyra in a shallow, maritime Antarctic lake

The filamentous chlorophyte Spirogyra forms a mat covering extensive areas of Spirogyra Lake, a small, shallow, Antarctic lake. It has an annual growth pattern, with a maximum standing crop of 400 μg chlorophyll-α m-2 during the ice-free summer period. Nutrient concentrations were low and there was evidence for P-limitation. The attainment of such a high standing crop was probably dependent on the lake's high specific dilution rate. Radiation flux was very low under winter ice cover and Spirogyra died back almost completely. The lake water became hypoxic and inorganic nutrients accumulated in both the water column and overwintering algal filaments. Spore formation was not observed, but changes in the composition of filaments indicated that polysaccharides, which had accumulated in summer, were depleted over the long, ice-covered winter period.