Dimethylsulphoxide and other biogenic sulphur compounds in the Galapagos Plume

Concentrations of biogenic sulphur compounds were measured at a series of stations inside and outside the high productivity plume to the west of the Galapagos Islands, during the PlumEx study in November 1993. This is the first field data set generated using a new specific enzyme technique for the determination of dimethylsulphoxide (DMSO). DMSO in seawater arises from the photochemical and bacterial oxidation of dimethylsulphide (DMS) and is thought to be a key compound in the marine biogeochemical sulphur cycle. The distribution of DMSO is discussed relative to DMS and dimethylsulphoniopropionate (DMSP) levels, together with data for chlorophyll and hydrography. Clearly elevated concentrations of DMSO, DMSPp and DMS were seen within the high productivity plume, and the significance of DMSO in deep waters is discussed.