Summertime seawater concentrations of dimethylsulfide in the western Indian Ocean: Reconciliation of fluxes and spatial variability with long-term atmospheric observations

Dimethylsulfide (DMS) measurements in the seawater of the subtropical and t he temperate western Indian Ocean were conducted for the first time from 3 December to 20 December 1997. In total, 443 surface seawater DMS determinat ions were performed between 24 degrees S-49 degrees S and 50 degrees E-77 d egrees E with a frequency of 1 sample every 10 km. An important spatial var iability was observed in seawater DMS concentrations with values ranging fr om 0.9 to 35.8 nM. DMS maxima coincided in most cases with thermal fronts a nd were in reasonable agreement with mean pigment figures obtained from sat ellite observations. The deduced DMS fluxes are consistent with long-term o bservations of atmospheric DMS and rainwater concentrations of nss-SO4= and MSA measured at Amsterdam island (37 degrees S, 77 degrees E); then accoun t for the differences observed in atmospheric DMS concentrations between Am sterdam island and Cape Grim, Indian Ocean monitoring stations.