What does Eutrophication mean?

Due to use of excess fertilizers, there is leaching of nitrates and phosphates into water bodies. This causes overgrowth of aquatic plants, covering the surface of water body which further leads to increased biological oxygen demand. Therefore, the process by which the excess phosphates and nitrates lead to overgrowth of algae and other aquatic plants in a water body, depleting the oxygen of water, is called Eutrophication. It leads to death of aquatic animals due to oxygen deficiency.