Describe the process of eutrophication in freshwater ecosytems?

Question

I can only find definitions of eutrophication, but nothing really on the process. Please help me out and thank you in advance.

Answer 1

Eutrophication occurs when nitrates from fertilisers are leached from the soil and washed into lakes and ponds and there is an increase of phosphates from detergents. An increase in the nitrates  and phosphates leads to and increase in the metabolic activity of algae casing algal bloom which covers the surface of the water. Light is prevented from reaching the other plants in the water therefore cannot photosynthesise and begin to die. The decomposition of plants causes increase in bacteria and so the Biological Oxygen Demand (BOD) increases and the oxygen concentration decreases. This leads to death of larger animals such as fish, which leads to more decomposition and increase in BOD.