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The AMT programme has facilitated detailed study of the north and south Atlantic oligotrophic gyres.Profiles of dimethylsulphide (DMS) and related parameters were measured throughout five AMT cruises between 1995 and 2003.This dataset confirms that ambient surface DMS concentrations are low in such regions (mean = 1.2 nM),while fluxes were highly variable (mean =3.2; range = 0.4 – 12.2 μmol m-2 day-1).As the surface area of oligotrophic regions represents approximately 40% of the world ocean (McClain et al.,2004),these areas represent a significant contribution to the global DMS flux.We interpret our dataset in conjunction with ancillary AMT data such as pigment concentrations,carbon fixation rates and bacterial numbers.In addition,the dataset was divided into biogeochemical provinces (Longhurst,1995) enabling us to address inter-province variability.During AMT-14,the in vitro activity of the enzyme responsible for DMS production (DMSP-lyase) was often substantially higher at the surface compared to the chlorophyll maximum.These results provide support for the protective role of DMS and related parameters during periods of oxidative stress,as suggested previously (Sunda et al.,2002).Measured surface DMS concentrations were also compared with those forecast using predictive models from the literature.Our results represent a step forward in understanding the reduced sulphur cycle,while the consistent overestimation of established global predictive models demonstrates how much further the subject needs to advance,particularly for oligotrophic regions.