Spatial–temporal distribution of dimethylsulfide in the subtropical Pearl River Estuary and adjacent waters

Three cruises were carried out in the Pearl River Estuary (PRE) and adjacent northern South China Sea (SCS) in July 2000, May 2001 and November 2002 to collect seawater samples. Concentrations of dimethylsulfide (DMS), chlorophyll a (chl a), nutrients (N, P, Si), salinity and temperature in seawater were measured. The spatial and temporal distribution of DMS concentrations showed larger fluctuations compared with other estuaries reported in the literature. The mean DMS concentrations in three cruises ranged from 0.05 nM (nM=10−9 mol l−1) to 52.7 nM ( n = 76 ). The higher concentrations of DMS were observed at the mouth of the estuary. In wet season, high variations of environmental salinity might stimulate algae to release more DMSP to adjust osmotic pressure. Most of these DMS ‘hotspots’ were coincident with the area of high chl a concentrations, although no significant correlation between DMS and chl a was found. The values of DMS/chl a showed a clear trend along the north to the south transect, increasing sharply from estuary to shelf and open sea. There was no significant correlation between DMS and salinity in the wet season (July and May), but a significant positive correlation in the dry season. High primary production and more iron deposition implied that the NE monsoon might influence DMS production in the dry season.