eutrophication
as defined in Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water…, Article 2, point (11)
the enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned