Dead zone is a common term used for hypoxic or low oxygen zones occurring throughout the world; the second largest occurrence is the Gulf of Mexico. These dead zones in some cases occur naturally or due to over concentration of phosphates from runoff of farming operations upstream on the Mississippi River. The fertilizers used in farming operations along the Mississippi River flow downstream entering the Gulf of Mexico through the mouth of the river through South Louisiana. The Hypoxic situation occurs through the build up of nutrients which causes an over production of algae which decomposes, sinks, and depletes oxygen in the water, leaving marine life unsustainable. This occurs south of the Mississippi River in areas as large as 4,500 to 6,000 square miles in the northern Gulf of Mexico.