What is Eutrophication? What are the stages of Eutrophication?

Eutrophication is the loss of oxygen in a body of water (e.g. pond or lake). This is usually due to algal bloom caused by artificial fertilisers and other chemicals being washed into the water by rain.The 5 stages:1.Chemicals/ artificial fertilisers: Chemicals and artificial fertilisers used on the land (e.g. for farms/crops) are washed into a pond/ lake by rainwater.2. Algal bloom: The excess nutrients from the chemicals cause the algae in the water to grow at a fast rate and bloom over the surface of a pond/lake.3. Plants die: The algal bloom on the surface of the water blocks sunlight to the plants at the bottom of the pond/lake. As plants require light for photosynthesis and this light is blocked, the plants die.4. Decomposition of the dead plants and algae: The algae eventually die and bacteria decompose both the dead plants and the dead algae, further using up the oxygen in the pond/lake.5. Fish die: As there are no longer plants to supply oxygen to the water and bacteria are decomposing dead plants and algae further using up the oxygen, the oxygen in the lake depletes. As there is not enough oxygen in the pond/lake to survive, the fish suffocate and die.At ths point the pond/lake is anoxic (no oxygen in the water) and only bacteria/aglae which do not need oxygen to survive are left.