Dimethyl sulfide production in a saline eutrophic lake, Salton Sea, California

Abstract

The concentrations and distribution of volatile organic sulfur compounds were quantified over a 13-month period in the Salton Sea, a warm eutrophic saline lake in Southern California, U.S.A. The concentrations of dimethyl sulfide (DMS) appear to be the highest reported thus far for a natural body of water, with an average surface (0–2 m) concentration of 2.5 µmol L−1. DMS concentrations as high as 11 µmol L−1 were measured, and the concentrations of DMS correlated strongly with chlorophyll a (r2 = 0.62, n = 265, p < 0.05). Dimethyl disulfide was also measured; concentrations were much lower than DMS and often below detection (<0.01-0.32 µmol L−1). Carbon disulfide concentrations were low (<0.03 µmol L−1) and associated with strongly reduced conditions. Very high concentrations of dimethylsulfoniopropionate (DMSP), an osmolyte in marine algae, were also measured (average total DMSP of 2.4 µmol L−1), with concentrations strongly correlated with chlorophyll a (r2 = 0.88, n = 36, p < 0.05). The biomass of the Salton Sea is composed mostly of marine phytoplankton species that are high DMSP producers; based on the correlations of DMS, chlorophyll a, and DMSP, it appears that the DMS in the Salton Sea is directly linked to algal biomass through DMSP. As a result of its very high DMS concentrations, the average estimated volatilization at the Salton Sea (480 µmol m−2 d−1) was greater than estimates for other lakes and the open ocean. We calculate ~9.6 × 105 mol of DMS was volatilized off the surface of the Sea during the course of this study.