'Dead Zones' Expand in the World's Oceans
August 19, 2008 -- The number of coastal areas known as dead zones is on the rise. A new study published in Science counted more than 400 dead zones globally, including 166 in U.S. waters, covering 245,000 square kilometers. Once filled with fish and many other organisms, these ocean waters are no longer habitable.
Dead zones are areas where marine life can not be supported due to depleted oxygen levels. A major cause of the increase in hypoxic zones is agriculture, specifically fertilizer. Fertilizer that runs off fields enters rivers and then flows out to sea. After the fertilizer reaches the ocean, algae and vegetation are fed by the nutrients and multiply. When they eventually die, the decomposition process robs the water of its oxygen. Very few organisms can tolerate the lack of oxygen and either suffocate or abandon the zone.
The National Research Council report Mississippi River Water Quality and the Clean Water Act: Progress, Challenges, and Opportunities offers recommendations for how the Environmental Protection Agency and the Mississippi river states can work together to diminish nutrient pollution in the Mississippi River and the Northern Gulf of Mexico.
Another National Research Council report Clean Coastal Waters: Understanding and Reducing the Effects of Nutrient Pollution proposes immediate local action by coastal managers and a longer-term national strategy to curb the problems of nutrient over-enrichment in coastal waters.