Eutrophication is a natural process taking place in water. The process is characterized by a development towards an environment rich in nutrients and a proliferous plant production.
Man-made eutrophication of inland water courses and shallow coastal waters is caused by excessive discharge of nutrients, especially phosphorus (P) and nitrogen (N) in the form of PO4 and NO3. In Norway the nutrients come primarily from agricultural activities, sewage and fish farms along the coast.
Visual effects of eutrophication include muddled and discoloured water, excessive algae- and bacteria production, and aquatic organisms killed by oxygen depletion. Thus, biodiversity in these aquatic ecosystems is often disturbed and depleted .
