Dead zone diet

By MEGHA SATYANARAYANA
Sun Herald, Biloxi, Mi; January 30, 2008

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Farms and their animals feed Gulf’s algae
The nutrient-rich muck created by corn, soybean and livestock farming in Mississippi and other states is fortifying the Gulf of Mexico dead zone, according to federal scientists in a new study. A possible trade-off of plentiful terrestrial food is the depletion of some of the nation’s popular seafoods, they said.

The dead zone is a seasonal occurrence caused by the overgrowth of algae in the Gulf. Nitrogen and phosphorous compounds from fertilizer and animal waste make their way into the Mississippi River, which dumps its nutrient-rich flow into the Gulf.

Algae, being primitive plants, feed off the nutrients as their more complex descendents do, and grow into large "blooms." In the process, they consume the oxygen in the water, choking out other life forms, including fish and bottom-dwellers. The water is oxygen-poor, or hypoxic, and cannot sustain life until the bloom dies down.

The Gulf of Mexico, said the scientists, needs a more balanced diet to slim down the dead zone.

Using computer modeling from water quality data gathered in the 1980s and 1990s, the scientists calculated that crops and animal agriculture are dumping 70 percent of the algae-feeding phosphorous and nitrogen into the water, which could create more frequent blooms. And while nitrogen has long been a culprit in the recurring dead zone, the contribution of phosphorous from untreated animal waste was a surprising finding, said lead author Richard Alexander of the USGS.

The Gulf of Mexico Hypoxia Task Force, which is composed of federal and state water and environment officials, will use data from the study to create guidelines for animal agriculture and runoff maintenance. They have just completed a draft action plan for cleaning up the Mississippi River Basin and the Northern Gulf of Mexico.

But once-plentiful monitoring stations have dwindled from 425 stations in the 1980s and 1990s to a current 35, said Tim Petty, deputy assistant secretary for Water and Science, U.S. Department of the Interior. The lack of data may hamper the ability to enact new guidelines.

megha@sunherald.com