Primary production of organic matter and phototrophic communities in the soda lakes of the Kulunda steppe (Altai krai)

The rates of photosynthesis and dark CO 2 fixation were determined in 12 soda lakes of the Kulunda steppe. Characterization of the phototrophic communities was given, and the cell numbers of anoxygenic phototrophic bacteria (APB) were determined. The photosynthetic production in different lakes was substantially different, constituting from 0.01 to 1.32 g C m −2 day −1 . The main part of carbon dioxide was assimilated in the process of oxygenic photosynthesis. Anoxygenic photosynthesis was recorded only in 5 of the 12 lakes studied. Its values varied between 0.06 and 0.42 g C m −2 day −1 , constituting from 8 to 34% of the total photosynthetic activity. Anoxygenic photosynthesis was revealed in the lakes where the number of APB reached 10 7 –10 9 CFU cm −3 . Dark CO 2 fixation constituted 0.01–0.15 g C m −2 day −1 . Positive correlation was observed between the primary production value and water alkalinity. No relationship between productivity and water mineralization was revealed in the 30–200 g l −1 range, whereas an increase in salinity above 200 g l −1 suppressed the photosynthetic activity. The mechanisms of influence of the environmental factors on the rate of photosynthesis are discussed.