To assess sources and sinks of DMS in the North Sea and in the Mediterranean sea.
Once released to the atmosphere, DMS affects aerosol formation upon oxidation to various sulphur acids. Future changes in the ocean's pelagic ecosystem related to greenhouse warming of the earth will probably be modulated due to temperature-induced shifts in the network of production, transformation and utilisation processes that determine the concentration of DMS in the marine environment. It is known that only a fraction of the DMS in seawater reaches the air above it. Therefore, detailed information on environmental factors affecting the biological cycling of DMS is required to allow a proper assessment of the potential contribution of biogenic sources to the total sulphur load in the atmosphere.
It is intended to identify the environmental factors that govern the rate of DMS precursor production in key algal species e.g. Phaeocystis and the transformation processes that are determined by the producers themselves through algal enzymatic action and by the activity of bacteria and microflagellates, both in oxic and in anoxic microenvironments. The origin and fate of the oxidation product DMSO will be followed since its importance in the sulphur cycle cannot be assessed simply by concentration measurements.
Biological, physical and photochemical processes influencing the sea-to-air flux of DMS in the microlayer at the sea surface will receive special attention; the flux itself will be measured under controlled conditions in mesocosms for extrapolation to variety of field situations.
Finally, model simulations will be used to place all process rates in the context of the future changes in the marine environment that are expected due to human perturbations and consequences of these changes for the rate of DMS emissions to the atmosphere in the years to come.
Funding SchemeCSC - Cost-sharing contracts
1790 AB Texel, Den Burg