Water Pollution (WJEC GCSE Biology)

Water Pollution

• Fertilisers and untreated sewage can be washed into water bodies such as lakes and streams, resulting in a process known as eutrophication 

• The following events occur with the continued run-off of fertilisers and sewage into water bodies:

  • These pollutants are high in nitrogen, an essential mineral for plant growth, so this can result in the overgrowth of aquatic plants and algae at the water surface

  • Light is blocked and aquatic plants below the surface die and are broken down by decomposers, e.g. bacteria and fungi

  • Decomposers increase in number, and the increased respiration of these organisms uses up oxygen in the water, reducing dissolved oxygen levels

  • The water no longer contains enough oxygen to support other organisms, so many aquatic organisms die

Water pollution from fertiliser run-off diagram

Fertiliser and sewage run-off can result in the suffocation of aquatic organisms