Distribution of dissolved and particulate dimethylsulfoxide in the East China Sea in winter

Abstract

The concentrations of particulate and dissolved dimethylsulfoxide (DMSOp, DMSOd) in the surface water of the East China Sea (ECS) in December 2009 were measured for the first time. The concentrations of DMSOp and DMSOd ranged from 2.4 to 80.0 nmol L −1 and from 3.2 to 357.0 nmol L −1 with average values of 21.3 nmol L −1 and 61.9 nmol L −1, respectively. The distribution of DMSOd was obviously influenced by the Yangtze River, with high concentrations appearing around the mouth of it. DMSOd represented the main methylated sulfur compound and dominated over dimethylsulfide (DMS) and dissolved dimethylsulfoniopropionate (DMSPd) by 1–2 orders of magnitude. The distribution of DMSOp did not show the same pattern as that of DMSOd. The concentrations of DMSOp increased offshore in the northeast ECS due to the change of phytoplankton species coupled to the increasing temperature, while in the southwest ECS the concentrations of DMSOp decreased offshore due to the poor DMSO-producers in the open sea. A weak positive correlation was observed between DMSOd and DMS in the whole study area. In addition, a significant relationship between DMSOp/Chl-a and temperature in the northeast ECS as well as a negative significant relationship between DMSOp and particulate DMSP in the southwest ECS was found. However, no relationship was observed between DMSOp and the environmental factors such as chlorophyll a, temperature and salinity. The vertical profiles of DMSOd in the study area were characterized by a maximum at depth from 2 to 25 m, while the DMSOp concentrations were characterized by a maximum at the bottom. Both DMSOd and DMSOp concentrations exhibited obvious diurnal variations with the maxima 7.4 and 2.4 times higher than the minima, respectively.