The marine biogeochemical cycle of dimethylsulfide (DMS), the main natural source of sulfur to the global atmosphere, was studied during a 2-week Lagrangian experiment in the subpolar North Atlantic, at 60¿N 21¿W. A bloom of coccolithopores, mostly of the species Emiliania huxleyi, dominated the phytoplankton assemblage over the first week. High surface concentrations of dimethylsulfoniopropionate (DMSP, 37--70 nM) were found along with moderate DMS concentrations (3--9 nM) during the entire experiment. Rates of biological DMSP consumption (8--51 nM d-1) and DMS production (1--14 nM d-1) and consumption (0--6 nM d-1) were measured in short-term dark incubations of surface seawater. Rates of DMSP biosynthesis (11--31 nM d-1) and DMS photochemical loss (1--10 nM d-1) were estimated by budgeting concentrations and transformation rates between Lagrangian samplings. Air-sea exchange rates for DMS (0.03--3 nM d-1) were calculated from surface concentrations, seawater temperature, and wind speed. All major processes involved in the DMS cycle showed significant short-term variability in coupling to the variability of solar radiation, wind speed, and mixing. Biotic and abiotic DMS turnover rates were of similar magnitude and very dynamic, with a prompt response to a rapidly changing physical environment. The rapid impact of meteorological forcing factors on DMS cycling provides the basis for a sulfur-mediated, short-term plankton/climate interaction. ¿ 1999 American Geophysical Union