Dimethyl sulphide in a stratified coastal salt pond

Abstract

Dimethyl sulphide (DMS) is the major volatile reduced organic sulphur compound in open ocean and coastal waters, and its emission from surface water represents a major flux of biogenic reduced sulphur to the atmosphere^1–8. It is an algal natural product^4,9–11 as well as a product of microbial decomposition of organic matter^12–15. In the open ocean, the distribution of DMS is correlated with primary productivity^3,4,6,8. In a study of a stratified coastal salt pond reported here, DMS was the predominant volatile sulphur compound in the oxic epilimnion throughout the year. There was consistently a peak in DMS concentration just above the oxic–anoxic interface at low oxygen tensions, probably arising from a combination of physiological stress and decomposition of algal material. During winter and early spring, a second DMS peak was present in the epilimnion, probably associated with algal production. Elevated DMS concentrations did not seem to be related to strict anoxia, as the lowest concentrations were always found in the anoxic hypolimnion where H₂S (a volatile reduced inorganic sulphur compound) dominates.