DIMETHYLSULFIDE (DMS) AND DIMETHYLSULFONIOPROPIONATE (DMSP) IN RELATION TO PHYTOPLANKTON IN THE GULF-OF-MAINE

Dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DM SP), in both particulate and dissolved forms, were surveyed during the early spring (March and April) and summer (July) of 1991 in coastal a nd offshore waters of the Gulf of Maine, USA, along with the hydrograp hy, inorganic nutrients, phytoplankton chlorophyll, and phytoplankton taxonomic composition and abundance. Concentrations as high as 15 nM D MS (in April and July), 208 nM particulate DMSP (in April), and 101 nM dissolved DMSP (in July) were recorded. Total DMSP (dissolved plus pa rticulate) reached 293 nM in a patch of the dinoflagellate Katodinium sp. in April. This is the first report of high DMSP concentrations in temperate waters in early spring associated with any organism other th an the prymnesiophyte Phaeocystis pouchetii. There were no correlation s between phytoplankton biomass, as measured by chlorophyll a, and DMS , and there were only slight correlations between chlorophyll a and DM SP in either dissolved or particulate form. As previously demonstrated by others, concentrations of intracellular (particulate) DMSP were re lated more to the presence of specific phytoplankton species rather th an to overall phytoplankton biomass. The occurrence of high DMSP and D MS levels in early spring, comparable with or higher than those seen i n summer maxima, at a time when bacterial activity is minimal and wind speeds are typically high may result in enhanced air-sea-fluxes of DM S.