Spatial and Temporal Variability of Dissolved Sulfur Compounds in European Estuaries

The spatial and temporal distribution of Dimethylsulfide (DMS), Dimethylsulfoniopropionate (DMSP) - its precursor -, Dimethylsulfoxyde (DMSO) - one of its oxidation products - Carbonyl sulfide (COS) and Carbonyl disulfide (CS2) were investigated during nine oceanographic cruises carried out in six major tidal European estuaries between July 1996 and May 1998. Low levels of DMS were recorded (mean of 0.6 nM, standard deviation (σ) 0.3 nM) during these 9 cruises. Positive correlations between DMS and salinity were frequently observed, with the highest DMS concentrations in the plume of estuaries, which could be explained by change in phytoplankton speciation from estuarine to shelf waters. Strong correlation between DMSP and DMS was reported for most of the estuaries denoting a simple conservative mixing of riverine and marine waters controlled by tide. In contrast to DMS, significant levels of COS and CS2 with mean concentrations of 220 ± 150 (pM; pM=10-12 M) and 25±6 pM respectively were recorded in four estuaries, indicating that estuaries could be a significant source of these compounds.