The dead zone forms each summer in waters from Texas to Louisiana after tons of nutrients, carried down the Mississippi and Atchafalaya Rivers during spring runoff, stimulate massive blooms of algae. The algae die, and bacteria that consume their carcasses deplete oxygen in the water to levels too low to support most marine life.
In May, Louisiana State University ecologist R. Eugene Turner studied the level of nitrogen compounds in the Gulf. From that data, he predicted a 2010 dead zone of between 7,400 and 8,500 sq miles. The extent of the hypoxic waters and nitrogen carried by runoff are unambiguously related, he said.
The large dead zone is the latest bad news for the Gulf, which is still dealing with oil from the BP rig explosion. Researchers, however, point out that the oil is not necessarily a factor in this year’s dead zone. “It would be difficult to link conditions seen this summer with oil from the BP spill,” added Nancy Rabalais, executive director of the consortium.