To facilitate the transition from fossil fuels to renewable energy, offshore wind farms are being planned at a massive scale in the North Sea. Improved governance is required to ensure that the farms have minimal negative impact on the environment and other activities, and do not reduce regulatory indicators such as the (Good) Environmental Status defined in the European Marine Strategy Framework Directive. There is evidence that turbine foundations change water turbulence, stratification and suspended sediment concentrations. Such oceanographic changes will affect the under-water light climate, nutrient availability and primary production, the effects of which will propagate through the ecosystem. Moreover, turbine foundations provide hard substrate for epifouling communities that filter particles from the water and participate in the nutrient cycling. We do not know enough about these processes and how they interact to make reliable predictions of the effects of large-scale wind farms on the marine environment necessary for decision making. There is a lack of in-situ evidence of filtering capacity and metabolism of epifouling communities. We also need improved methods to scale physical processes from turbine scale to farm scale, as a function of structure size and distance, while accounting for the hydrographical characteristics (depth, tidal current speeds, wave climate, stratification, seabed composition). That requires, among others, insight into the interactions between structures that are in each other's wake. Moreover, we do not know the spatial ecological footprint of large-scale wind farms, nor what happens at the scale of the North Sea if these overlap. Setting governance boundary conditions on technical details like sizes and distances may allow optimising wind farm implementation to satisfy ecological as well as economical requirements. We will carry out field observations, use remote sensing, improve and apply numerical hydrodynamics-ecosystem models and develop governance mechanisms to address these gaps.
