Halophilic algal-bacterial and cyanobacterial communities and their role in carbonate precipitation

Abstract

This work studies the diversity of cyanobacterial and algal-bacterial communities of saline water bodies in the Crimean Peninsula and Altai Region. Plant-bacterial communities are described for the first time. The dependence of the production and destruction on the season and salinity of the water body is shown. The development of planktonic cyanobacteria is related to the presence of zooplankton, the development of which is controlled by hydrogen sulfide. The high hydrogen sulfide tolerance of benthic cyanobacteria secures the integrity of cyanobacterial communities. Observations in nature and laboratory modeling show that the formation of mineral layers is restricted to conditions of supersaturation with mineral components. Carbonate precipitation can take place in cyanobacterial communities under conditions of mixing sea water enriched with Ca and Mg with continental water enriched with sodium carbonate. Cyanobacteria are able to form and transform various Ca-Mg-carbonates. Dolomite formation is a derived process that occurs in cyanobacterial mats in the presence of sulfate-reducing bacteria. Carbonatization of cyanobacterial cells is considered using the example of the unicellular halophilic-alkaliphilic cyanobacterium Euhalothece sp. The accomplished study is of certain interest for interpretation of geological and paleontological data in the context of the supposed analogy between cyanobacterial mats and ancient stromatolites.