Explain eutrophication.

How I would explain to the student:pollution of streams and rivers because of fertiliser use, open sewers into water courseexcess nutrients get washed up in water courseplants flourish using these mineralsso excess growth of aquatic plants, algae causing algae bloom.oxygen gets depleted and this algae will block sunlight reaching other plants so they all die as they cannot photosynthesise to survivedecomposition then leads to further usage of oxygen so no oxygen left for bacteriadeath of the ecosystem ensues as oxygen levels reach a low that can no longer sustain life.