MODEL STRUCTURE AND ANALYSIS OF DIMETHYLSULFIDE (DMS) PRODUCTION IN THE SOUTHERN NORTH-SEA, CONSIDERING PHYTOPLANKTON DIMETHYLSULPHONIOPROPIONATE (DMSP) LYASE AND EUTROPHICATION EFFECTS

A model for dimethylsulphide IDMS) production in the southern North Se a is presented. This model is coupled to the phytoplankton model FYFY, which calculates the biomass of different phytoplankton groups with t heir specific contents of dimethylsulphoniopropionate (DMSP), the prec ursor of DMS. The combined models provide a synoptic view of the seaso nal distribution of DMS and its sea-to-air exchange rates. Results are in close agreement with field data, showing a spring peak and high co ncentrations in the coastal area off continental Europe. Model analysi s shows high sensitivity to phytoplankton DMSP-lyase, particularly in the description of the spring peak of DMS. Omission of this pathway fo r DMS production leads to an underestimation of the annual sea-to-air flux of up to 25%. Model output also suggests that anthropogenic eutro phication of the southern North Sea may have caused a 2.5-fold increas e between the beginning of this century and the 1980s in the mean annu al emission of DMS to the atmosphere.