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eutrophication
Eutrophication (Greek: ''eutrophia''—healthy, adequate nutrition, development; (ドイツ語:Eutrophie)) or more precisely hypertrophication, is the ecosystem's response to the addition of artificial or natural nutrients, mainly phosphates, through detergents, fertilizers, or sewage, to an aquatic system.〔Schindler, David and Vallentyne, John R. (2004) ''Over fertilization of the World's Freshwaters and Estuaries'', University of Alberta Press, p. 1, ISBN 0-88864-484-1〕 One example is the "bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Negative environmental effects include hypoxia, the depletion of oxygen in the water, which may cause death to aquatic animals.
==Mechanism of eutrophication==
Eutrophication arises from the oversupply of nutrients, which induces explosive growth of plants and algae which, when such organisms die, consume the oxygen in the body of water, thereby creating the state of hypoxia.
According to Ullmann's Encyclopedia, "the primary limiting factor for eutrophication is phosphate." The availability of phosphorus generally promotes excessive plant growth and decay, favouring simple algae and plankton over other more complicated plants, and causes a severe reduction in water quality. Phosphorus is a necessary nutrient for plants to live, and is the limiting factor for plant growth in many freshwater ecosystems. Phosphate adheres tightly to soil, so it is mainly transported by erosion. Once translocated to lakes, the extraction of phosphate into water is slow, hence the difficulty of reversing the effects of eutrophication.〔M. Nasir Khan and F. Mohammad "Eutrophication of Lakes", Date: 19 Nov 2013; in A. A. Ansari, S. S. Gill (eds.), Eutrophication: Challenges and Solutions; Volume II of "Eutrophication: Causes, Consequences and Control", Springer Science+Business Media Dordrecht 2014 〕
The source of this excess phosphate are detergents, industrial/domestic run-off, and fertilizers. With the phasing out of phosphate-containing detergents in the 1970s, industrial/domestic run-off and agriculture have emerged as the dominant contributors to eutrophication.〔Wilfried Werner "Fertilizers, 6. Environmental Aspects" Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim.〕
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