The Role of Microorganisms in Transformation of Selenium in Marine Waters

The activity of microorganisms is a decisive factor in the transformation of the essential and, at the same time, toxic selenium (Se) in marine waters. This review provides an analysis of the literature data on the microbiological regulation of the state of Se in marine waters: the role of microorganisms in eliminating toxic Se from marine waters through precipitation of reduced Se forms and in the reverse process, transformation of Se into a form available to be taken up by organisms and involvement of this element in the biogeochemical cycle. The processes of transformation of the oxidized and reduced Se forms with the participation of microorganisms in marine waters are considered. It has been shown that in anaerobic conditions bacteria use the oxidized Se forms as electron acceptors (reduction). Bioavailable selenite and selenate ions are formed in the case of aerobic oxidation. Biotransformation of dissolved Se is a key mechanism for the formation of methylated gaseous Se forms in marine waters as one of the ways to remove this element from the aquatic environment.