Dimethylsulfide in the water column and the sediment porewaters of the Peru upwelling area1

The concentration of dimethylsulfide (DMS) and supporting parameters were determined on longshore and cross‐shelf traverses in the Peru upwelling area. Vertical DMS profiles were measured at several stations in the marine water column and in the sedimentary porewaters. The distribution of DMS in surface waters is related to the patchiness of the upwelling process and of the resulting phytoplankton biomass. Substantial concentrations of DMS were found in the sedimentary porewaters, with a sharp maximum a few centimeters below the sediment‐water interface. The source of this DMS is most likely the decomposition of algal material which settles to the bottom beneath the upwelling areas. The rates of DMS production in the water column and its flux into the atmosphere across the air‐sea interface are only a small fraction of the rate of sulfate assimilation by the plankton community. The concentrations of DMS in the surface waters of the Peru shelf are similar to those found in other coastal areas; the fluxes of reduced sulfur gases to the atmosphere from this upwelling region do not require special consideration in the global atmospheric sulfur budget.