Modelling marine ecosystems A model, which measures the effect of climate change on marine ecosystems, has been developed. Climate Change and Environment © PhotoDisc The common fisheries policy set out to examine the interactions between fisheries and the ecosystem concerning fisheries management decisions. The ecosystem approach is based on identifying processes, which impact function, productivity and biological diversity. Hence, it takes the interaction between food webs into consideration. Additionally, it protects the chemical, physical and biological environment involved in the well-being of the ecosystems. In order for this to take place, HAMSOM, a non-linear 3-d baroclinic model using a turbulent eddy viscocity as a function of turbulent eddy kinetic energy was developed and implemented. The important variables used for prognosis in the model included temperature, salinity, water transport, sea surface elevation, turbulent vertical eddy viscosity and diffusivity and turbulent sea surface fluxes. Additionally a particle tracking model with individual based motion was designed in order to study local aggregation effects and was applied near the Dogger Bank region. Also made to couple the HAMSOM model was the ecosystem model, which can study local production effects at frontal locations. It is made up of three nutrient cycles: nitrogen, phosphorus and silicate, which comprise the major nutrients that limit phytoplankton production in shelf areas. The ecosystem model the nutrients to simulate the dynamics of phytoplankton diatoms and flagellates based on each groups respective nutrient, light and physiological characteristics. The anticipated benefits of the model include allowing for resolution of historic distribution of hydrograph properties in the North Sea and Baltic Sea. As a result, this can be used as a comparison to fish surveys. It can also be used in the distribution of fishery activities. Furthermore, it can allow for scenario testing of climatic process effects on the dynamics of the ecosystems in these regions and their exploited fish populations.