Effects of near-bottom water oxygen concentration on biogeochemical cycling of C, N and S in sediments of the Gulf of Gdansk (southern Baltic)

191Rates of benthic exchange of hydrogen sulfide, ammonium and dissolved inorganic carbon (DIC) in the Gulf of Gdansk and molar ratios of organic carbon (OC) to total nitrogen (TN) and total sulfur (TS) in surface (0-2 cm) sediment layer. Sediment under oxic conditions is source of DIC to near-bottom water. Under hypoxic and anoxic conditions DIC fuxes are several times lower and sediments are source of hydrogen sulfide and ammonium. Highest fluxes of hydrogen sulfide and ammonium were observed for sediments from intermediate depth where hypoxia is a seasonal phenomenon. As a result of high sedimentation rate and oxygen deficit in near-bottom water preservation of OC and accumulation of TS in sediment takes place in the area below halocline.