Outline the process of eutrophication

Eutrophication occurs when nitrate fertilisers are carried by ground water into lakes and ponds. The fertliser encourages algal growth in the water, which in turn blocks out sunlight. This causes submerged plants to die and decompose, as they rely on sunlight to photosynthesise. The dead plants are broken down by the bacteria in the water, which flourishes, and consumes oxygen in the water. The oxygen levels may drop so much that the fish and other organisms living in the water cannot respire, resulting in their death. Eventually, this process can cause oxygen levels to get so low that no living organisms can live in the water.