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Therefore, human causes of eutrophication include the use of agricultural fertilizers. Other causes include sewage and aquaculture, which is the growing or farming of fish, shellfish and aquatic plants. Wastewater from certain industries and burning fossil fuels can also contribute to eutrophication.
Sometimes it is caused by a kind of blue green algae called cyanophyceae. It causes a phenomenon called water bloom. It makes the water dark green in color. Causes are an unusual amount of sunshine, or deposits of phosphorus or nitrogen in the water derived from human activity. large deposition of algae on the surfacxe of water resulting into non availability of oxygen to the marine life resulting in their death causes eutrophication...........