CORRELATION OF VIABLE CELL COUNTS, METABOLIC-ACTIVITY OF SULFUR-OXIDIZING BACTERIA AND CHEMICAL-PARAMETERS OF MARINE-SEDIMENTS

Viable counts of aerobic and anaerobic chemotrophic sulphur-oxidizers as well as phototrophic sulphur bacteria were determined in sediment s amples taken from two different areas along the Baltic Sea shore which were known to regularly develop sulphidic conditions. Depth profiles of bacterial cell counts were correlated with concentration profiles o f chloride, sulphate, sulphide, nitrate and phosphate in the pore wate r of these sediments and with potential activities of nitrate reductio n, thiosulphate transformation and sulphate formation. The data reveal ed a complex multilayered structure within the sediments. Sulphide was released into the water from sediments of both sampling areas, but it was found that light and the availability of oxygen significantly red uced this amount. In the highly reduced sediment at Hiddensee, the hig hest numbers of phototrophic and chemotrophic sulphur-oxidizers were f ound near the sediment surface. Therefore, it was concluded that the c ombined action of both groups of bacteria most efficiently oxidizes re duced sulphur compounds in the top;layers of the sediments. Nitrate ma y replace oxygen as final electron acceptor and will support oxidation of sulphide, in particular when oxygen and light are limiting.