What is eutrophication and what are its effects?

Eutrophication occurs when excess nutrients, like nitrates and phosphates, enter a body of water. These excess nutrients cause an increase in plant and algal growth in the water, often leading to an algal bloom. Nitrates and phosphates are most commonly found in fertilisers, sewage and detergents and often enter the water system via run-off from farming and industry. When an algal bloom occurs, the plants and algae cover the surface of the water body. This prevents light reaching the bottom of the water, thereby killing bottom dwelling plants. Algal blooms also lead to an overall reduction in water quality. Once the excess algae and plants begin to die, they are decomposed by bacteria in the water. These bacteria use up the oxygen in the water, reducing its level, causing fish deaths. In this way eutrophication not only reduces overall water quality, but it also reduces biodiversity by harming living organisms in the water body.