Eutrophication

Eutrophication is the response of a body of water to enrichment by nutrients. The nutrients greatly promote the growth of simple algae and plankton over other more complicated plants, causing algal blooms.

The water body becomes starved of oxygen and the normal ecosystem is disrupted. Fish and shellfish may die and the water becomes cloudy, green, yellow, brown, or red.

Surveys indicate that 48% of lakes in North America suffer from eutrophication; 53% in Europe, and 54% in Asia.

Although industrial and sewage discharges of phosphate have been reduced greatly during the past 25 years, eutrophication remains a major environmental issue. Most phosphorus enters bodies of water through soil erosion from agricultural lands. Improved planting methods, fertilizer management, and soil conservation techniques are being used to reduce phosphorus runoff.

Eutrophication of Oceans
Eutrophication also occurs in marine and coastal waters. The World Resources Institute has identified 375 hypoxic coastal zones in the world, concentrated in coastal areas in the Southern coasts of the US, Western Europe, the Eastern and, and East Asia, particularly in Japan.