Participation of algal–bacterial community in the formation of modern stromatolites in Cock Soda Lake, Altai Region

Resumo

Modern dolomite stromatolites are found in Cock Soda Lake (Kulunda Steppe) at a salinity of 100–200 g/L and pH of 10. The mineralogical analysis has revealed the presence in the stromatolites of Ca⎯Mg-carbonates of various compositions. The organisms–edificators of the phototrophic community developing in the lake are determined. They are identified as a part of the mineralized biota (cyanobacteria, bacteria, and eukaryotic alga Ctenocladus circinnatus). Morphological and ultrastructural features of exopolysaccharides secreted by cyanobacteria and bacteria dominant in the phototrophic community are characterized. It is shown that polysaccharides secreted primarily by cyanobacteria have the utmost importance for the formation of stromatolites in Petukhovskoe Soda Lake.