Explain what eutrophication is and how it is caused

Some farmers use too many fertilisers, so when heavy rain comes, these can run off the fields. This then pollutes nearby streams and rivers, leading to eutrophication.
The process of eutrophication is as follows:Excessive nutrients from fertilisers are flushed from the land into rivers or lakes by rainwater, leading to a nutrient build up.The pollutants cause aquatic plant growth of algae, duckweed and other plants.This causes an algae bloom, which is a build up of algae, which prevents sunlight reaching other plants meaning less photosynthesis occurs. This causes the other plants to die, as a result oxygen in the water is depleted.These dead plants are then broken down by decomposing bacteria. These bacteria use up even more oxygen in the water, so oxygen is even further depleted.Oxygen levels then reach a point where no life is possible. Fish and other organisms die as a result.