Eutrophication

Eutrophication is the excessive enrichment of a body of water with nutrients, chiefly the nitrogen and phosphorus carried in agricultural runoff and fertilizer, which fuels algal blooms that, as they die and decompose, consume the water's dissolved oxygen and can create a hypoxic dead zone unable to support fish and other aquatic life. The seasonal dead zone in the Gulf of Mexico, fed by nutrient runoff carried down the Mississippi River basin's farmland, is among the most closely monitored examples of agriculturally driven eutrophication.