Spatial distributions of dimethylsulfide in the South China Sea

The concentration of dimethylsulfide (DMS) and supporting parameters were d etermined in surface seawater and vertical profiles at 26 stations in the S outh China Sea. The concentrations of DMS in surface seawater ranged from 6 1 to 148 ng S/l, with a mean of 82 ng S/l. High concentrations of DMS were found in the productive regions. The vertical profiles of DMS were characte rized by a maximum at depths typically between 20 and 75 m. The concentrati ons of DMS were correlated with the levels of chlorophyll a both in the sur face seawater and in the vertical distribution. The concentrations of DMS w ere higher than expected for this chlorophyll-poor tropical sea, as indicat ed by markedly high DMS (ng S/l)/chlorophyll a (mu g/l) ratios ranging from 315 to 3524 with a mean of 1768 for all the surface seawater samples. DMS concentration was significantly correlated with seawater temperature and di ssolved oxygen, but it showed an inverse relationship to nutrients (includi ng nitrate, phosphate and silicate). On the basis of sea surface concentrat ions of DMS and gas exchange calculations, the mean flux of DMS from the So uth China Sea to the atmosphere was estimated to be 5.5 mu mol m(-2) d(-1). (C) 1999 Elsevier Science Ltd. All rights reserved.