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 sulphide(1,2), DMS. Subsequent oxidation of DMS to acidic aerosols influences particle nucleation and growth over t he oceans(3), and so has the potential to influence radiative balance and g lobal climate. It has been suggested(4) that this plankton-climate interact ion is self-regulated, but tests of this hypothesis have remained elusive a s little is known about the feedback effects of climate on the marine DMS c ycle(2). DMS is produced by enzymatic cleavage of the abundant algal compon ent dimethylsulphoniopropionate(5) (DMSP), which suggests a high potential for DMS generation in the ocean. But there are competing processes(6) that utilize DMSP in the food web without producing DMS, and the external contro ls on these processes are unknown. Here we present data of DMSP consumption , DMS production and mixing-layer depths (which are driven by climate) in t he subpolar North Atlantic, and compare these data with published results f rom other latitudes, We find evidence that the mixing-layer depth has a sub stantial influence on DMS yield in the short term, This finding, combined w ith the seasonal effect of vertical mixing on plankton succession and food- web structure, suggests that climate-controlled mixing controls DMS product ion over vast regions of the ocean.