DIMETHYL SULFIDE IN NORTH-SEA WATERS AND SEDIMENTS

Dimethyl sulphide (DMS) and dimethylsulphoniopropionate (DMSP) were me asured in the water column and sediments at a number of stations in th e southern half of the North Sea during three cruises. Both DMS and DM SP in the water column exhibited seasonal changes with higher concentr ations during summer. Concentration profiles of DMS and DMSP in the wa ter column on a number of occasions showed peaks near the bottom indic ating settlement of algal material. The concentrations of DMS and DMSP in the bottom sediments were, per unit volume, three orders of magnit ude greater than in the water column. Measurements of fluxes of reduce d sulphur gases from bottom sediments at five stations over the southe rn North Sea showed that DMS, methanethiol and hydrogen sulphide were emitted to the water column from the sediments at slow rates. The fast est rates of emission were at station ES in the central area of the No rth Sea which stratifies during summer. However, the rates of emission were slow compared to those from intertidal sediments. If the emissio n rates were typical, the emission of reduced sulphur gases from the s ediment accounted for only a small proportion of the annual input to t he sediment through settlement of organically bound sulphur in organic detritus. The majority of the deposited sulphur must be either reoxid ized before emission from the sediment or buried.