The coastal waters of the Southern Bight of the North Sea receive large quantities of nutrients of anthropogenic origin via rivers and the atmosphere. Eutrophication is apparent in the coastal zone in the form of undesirable qualitative changes in the structure and functioning of the planktonic ecosystem, and can be observed in the form of occasional accumulation of foul-smelling foam on beaches. Guaranteeing sustainable North Sea resources for future generations and protecting the quality of coastal waters is now both a national and an international concern. National and international regulations on sewage treatment facilities and farming practices aiming at the reduction of nutrient supply to the coastal sea have already been implemented in the various countries which border the North Sea. However, the scientific knowledge needed for a rational estimate of the reduction required and of the nutrient(s) which have highest priority for reduction (ammonium, nitrates and/or phosphates) is currently lacking. The subproject wants to study the related changes in the higher trophic levels, particularly zooplankton.