Eutrophication is the process by which a body of water acquires a high concentration of nutrients (nitrogen, N, and phosphorus, P) promoting excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish (Art, 1993).
Eutrophication is a natural, slow-aging process for a water body, but human activity like intensive agriculture or population pressure greatly speeds it up. When nutrients that comes from domestic and industrial effluents are deposited in large quantities, occurs the production of sharp deterioration of rivers, lakes, reservoirs and coastal waters, causing numerous direct and indirect effects on aquatic biodiversity. Furthermore, eutrophication commits the multiple uses of water resources and surface and groundwater, causing substantial losses for the local and regional economy.
Among many nutrients, studies has demonstrated that Phosphorus (P) is the main nutrient responsible for eutrophication. Due to that, over the last years, mitigating P has been adopted as the major water parting management tool to control freshwater eutrophication. P can come into freshwater from point sources (e.g., sewage) and from non-point sources (e.g., agricultural runoff; residential runoff). Decreasing external loading (point) has proven easier to deal than reducing internal point (non-point). This happens because recycling P from bottom sediments can cause problems on the water quality, and the ecosystem recovery after P remediation can be complex. In some studies, phosphorus-based treatment have not delivered ecological improvements in some lakes. It is also important to understand the causes of the time lags in water quality associating it with Legacy P.
Legacy P is the surplus P derived from past land use activities that is stored in soils and sediments and re-released as the P storage capacity becomes gradually saturated, or after a change in land use, land management, or effluent management (Kleinman et al., 2011). These association may be one explanation of why indeed point-source controls is failing to yield the expected improvements in river water quality.
It is necessary to understand the complete process (causes and development) of eutrophication to control it. Also it is necessary carefully evaluate the management solutions to be used in the mitigation and remediation of eutrophication. Although they are very expensive, I believe that conventional wastewater treatment systems are adequate.
Often the nature can be a reflection of the society. Eutrophication is an example also in a careless manner that people deal with their waste and also with the inappropriate application of land use. So it is interesting that everyone is aware of ecological problems like this and do their part so that there will be a reduction of pollution of freshwater improving aquatic quality.
Bio Enterprise and Employability 
I like the points you make in this entry however I think mitigating eutrophication requires a lot of thought. There will inevitably have to be a trade off between different organisms if eutrophication is to be thoroughly controlled. Nitrogen and phosphorous are often important in lake ecosystems as they can sustain life and play a part in controlling temperature and water quality. Therefore ‘improving’ water quality to benefit humans (eg. for drinking water or to control economical losses) may not be beneficial to all the aquatic life.
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