A model system approach to biological climate forcing: The example of Emiliania huxleyi

The following is an extended summary of the project "A model system approach to biological climate forcing: the example of Emiliania huxleyi," that was carried out within the framework of the Dutch National Programme on Air Pollution and Climate Change (NRP) - phase II. In this report the progress is described that has been made in the formulation of the Dynamic Energy Budget (DEB) Theory that now includes photosynthesis, nutrient limitation and calcification. On top of this the next level of organisation was explored in the adaptation of the model towards a small ecosystem comprising an autotrophic and a heterotrophic organism together with a decomposer, -the dynamics of biomass in vertical profiles has been analysed. At the same time experiments were conducted with E. huxleyi in order to be able to validate the DEB-models at the organismic level. The experiments involved exploration of the genes that control calcification, photosynthesis and nutrition, a detailed description of growth based on chemostat experiments, and an inventory of environmental factors that determine the production of dimethylsulfoniopropionate, the precursor of the biogenic gas dimethylsufide (DMS) that regulates climate once it has reached the atmosphere acting as a source of cloud condensation nuclei.