The process by which a body of water becomes rich in dissolved nutrients from fertilizers or sewage, thereby encouraging the growth and decomposition of oxygen-depleting plant life and resulting in harm to other organisms: Aquaculture has been resulting in small, but expanding into locally significant emissions of nutrients (nitrogen and phosphorus) into the Baltic Sea, contributing to eutrophication.

The condition of waters (lakes and or ponds) having rich in mineral and organic nutrients that promote a proliferation of plant life, especially algae, which reduces the dissolved oxygen content and often causes the extinction of other organisms: Agricultural fertilizers and many commercial detergents are rich in phosphorus and the pollution of a lake with the addition of more phosphorus to its waters first produces a green scum of algal growth on the surface of the lake and then, if the pollution continues, it proceeds to "kill" the lake.

After the initial bloom of rapid algal growth, aging algae die, and then the bacteria feeding on the dead algae cells use up so much of the lake's dissolved oxygen that fish and invertebrate animals suffocate.

The enrichment of fresh or saline water by chemical nutrients that may overly increase the growth of aquatic plant life: Cultural eutrophication is caused by human activities, such as excessive use of chemical fertilizers or the contaminations of water by sewage effluents.