The bacterial population and the process of hydrogen sulfide oxidation

Methods are described to study the mechanism and rate of sulphide oxidation in water using 35S. These methods were used in the Black Sea together with measurements of O2, H2S, Eh, bacterial biomass and production. Sulphide oxidation proceeds via two main steps: chemical oxidation of sulphide to sulphate and thiosulphate, and the biological oxidation of thiosulphate to sulphate. The rate of sulphide oxidation varied from 0-4--0-9 g H2S/m2 day. The maximum rate of oxidation took place at depths of 150-170 m at Eh- 10 to —20 mV, and at a maximum rate of chemosynthesis of 8 mg C/m3/day. Data are given for the biomass of the microflora and its production in the water column. The maximum efficiency of chemosynthesis was 15 %. The results are discussed in relation to the budget of the organic matter