Explain the process of eutrophication.

Nitrates and phosphates are leached into a slow-moving water body (e.g. a lake). This results in an algal bloom on the surface of the water body. The algae block sunlight and prevent it from reaching aquatic plants beneath them. Consequently, these aquatic plants die due to a lack of photosynthesis. Microorganisms (saprobionts) thrive from decaying these dead plants . These microorganisms carry out a lot of aerobic respiration, which depletes the oxygen supply in the river. Aquatic animals (e.g. fish) die from a lack of oxygen for aerobic respiration.