Crop management strategies key to a healthy Gu...( OAK RIDGE Tenn. April 21 2008 Impro...)

OAK RIDGE, Tenn., April 21, 2008 Improved management of crops and perennials could go a long way toward alleviating the problem of hypoxia, which claims thousands of fish, shrimp and shellfish in the Gulf of Mexico each spring.

An assessment by a team led by Virginia Dale of Oak Ridge National Laboratorys Environmental Sciences Division concludes that low oxygen levels in water, or hypoxia, causes problems throughout the ecosystem. The death zone, scientifically documented in the Gulf since 1985, has consistently covered about 6,000 square miles, usually off the coast of Louisiana west of the Mississippi Rivers mouth.

The problem is caused in part by fertilizer run-off from agricultural activities in the Mississippi basin, which drains about 48 percent of the U.S. land. These nutrients combined with stratification caused by warm freshwater from the Mississippi and Atchafalaya rivers running into the colder saltwater of the Gulf sets up the deadly process. Algae grows, then dies and sinks to the bottom, where it decomposes, using up oxygen in the process.

The oxygen-depleted water at the bottom is not replenished because of the lack of circulation, Dale said. The more water that flows into the Gulf and the more nutrients in the water, the worse the hypoxia becomes.

While scientists initially believed nitrogen was the major culprit, the assessment team for the Science Advisory Board of the Environmental Protection Agency realized that phosphorus also plays a significant role. The team is recommending a 45 percent reduction in phosphorus and nitrogen from the 1980-1996 average flux during the spring (April, May and June) on a five-year running average.

The assessment team found that the most significant opportunities for nitrogen and phosphorus reduction in the Mississippi Basin are promotion of the production of environmentally sustainable biofuel and other perennial crops, improved infield management of nutrients, co
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