The production of DMSP by phytoplankton and the fate through the marine system of both DMSP and DMS were followed for a period of 21 rno in the natural environment by studying a Wadden Sea tidal inlet. The major production and emission of DMS appeared to be limited to a period of only 2 mo, which was closely linked to the presence of phytoplankton blooms. The production of DMS in the water column was not well correlated with chlorophyll a concentrations or plankton species composition. It was however, found to be closely related to the start of a Phaeocystis bloom early in spring. Contrary to our expectations, the senescence phase of this Phaeocystis bloom did not result in high DMS accumulation. It is postulated that this phenomenon could be the result of a bacterial consumption which increased with time in combination with a decreasing DMSP-lyase activity of Phaeocystis. A slmple model, into which the overall DMSP consumption could be introduced, could very well ~mitate the measured concentrations of DMS In the water column of the natural system studied.

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