Eutrophication occurs when the chemicals and nutrients typically, compounds containing nitrogen and phosphates leach into water during rains and find their way to water bodies. This result in increase of nitrates and phosphate in the water that gives boost to growth of algae which at times covers up the entire water body. This is one of the major reasons for impairment of water quality. It causes hypoxia or depletion of oxygen and gives raise to harmful algae blooms. This is one major reason for destruction of aquatic life in those affected areas.
These nutrients flow through fresh water systems and finally reach the sea. However, here these excess nutrients give raise to excessive growth of phytoplanktons, micro algae and macroalgea. As these cover the vast expense of the water body, these organic materials die and fall to the ocean floor and decompose. As these decompose the oxygen is consumed leaving the living organisms of the ocean floor to suffocate, especially the slow-moving species and they perish in such an environment. This causes hypoxia in the waters of the coastal regions. This can hamper the most productive areas of the ocean. Excessive of growth of planktons and other microalgae becomes a barrier for the sun rays to reach the depth of the ocean floor. Moreover, such excessive is the growth that even the grazing marine animals are unable to consume all this over growth. This Eutrophication has serious negative impact like loss of species, and destruction of the ecosystem.