Role of vertical mixing in controlling the oceanic production of dimethyl sulphide

Marine microbiota are important for the global biogeochemical sulphur cycle, by making possible the transfer of reduced sulphur from the ocean to the atmosphere in the form of dimethyl sulphide1,2, DMS. Subsequent oxidation of DMS to acidic aerosols influences particle nucleation and growth over the oceans3, and so has the potential to influence radiative balance and global climate. It has been suggested4 that this plankton–climate interaction is self-regulated, but tests of this hypothesis have remained elusive as little is known about the feedback effects of climate on the marine DMS cycle2. DMS is produced by enzymatic cleavage of the abundant algal component dimethylsulphoniopropionate5 (DMSP), which suggests a high potential for DMS generation in the ocean. But there are competing processes6 that utilize DMSP in the food web without producing DMS, and the external controls on these processes are unknown. Here we present data of DMSP consumption, DMS production and mixing-layer depths (which are driven by climate) in the subpolar North Atlantic, and compare these data with published results from other latitudes. We find evidence that the mixing-layer depth has a substantial influence on DMS yield in the short term. This finding, combined with the seasonal effect of vertical mixing on plankton succession and food-web structure, suggests that climate-controlled mixing controls DMS production over vast regions of the ocean.