Geochemical consequences of microbiological processes on the northwestern Black sea shelf

The rates of H2S and CH4 production and microbial CH4 oxidation on the surface of the bottom sediments on the low-depth northwestern Black sea shelf, were estimated from 35S and 14C isotope measurements. It was shown that microbial processes of sulfate reduction and methane production are accompanied with changes in O2 concentration in the near-bottom waters, salt composition of mud waters, and isotope composition of sulfate and bicarbonate carbon. An expressed exponential dependence of the isotope composition reduced sulfur compounds on sulfate reduction rate was observed. In sediments that exhibit high rates of sulfate reduction, the 13C concentration of antigenic carbonates and Corg decline. values of δ13C (from -58 to -78 per mil) prove its autochtonous microbial origin