Eutrophication is caused by excess nutrients like nitrogen and phosphorus entering water bodies from sources like agricultural and urban runoff. This causes harmful algae blooms which can reduce oxygen levels and kill fish and aquatic life. Two examples are the hypoxic "Dead Zone" in the Gulf of Mexico caused by Mississippi River runoff and a large "Dead Zone" in the Baltic Sea from Swedish and Finnish fertilizer use. Preventing eutrophication requires reducing nutrient inputs from fertilizers and sewage as well as planting vegetation to absorb excess nutrients.

1. Eutrophication (Anthropogenic eutrophication) Mina Ivanova Lassie Milanova Ivaylo Danailov 10/7