Eutrophication

• Nitrates and phosphates are mineral fertilisers that helps plants grow in fields

• However too much fertiliser can leak into rivers and lakes as rain pours and the minerals travel through the soil

Process of Eutrophication

1. Fertilisers enter the water, adding extra nutrients

2. Extra nutrients cause algae to grow fast on the surface of the water body, blocking out light

3. Plants below the water can’t photosynthesise due to the lack of light and start to die

4. With more dead plants, there are more food available for microorganisms to feed on, increasing them in number and using up the oxygen in the water

5. Organisms that need oxygen die due to lack of availability (like fish)

Sewage can also cause eutrophication, as they contain phosphates from detergents and nitrates from waste products