Appearance Of Gulf Dead Zone Earliest Ever Recorded

"An annual dead zone in the Gulf of Mexico has appeared earlier this year than in the past, suggesting it might be larger this summer.

The dead zone is created by spring runoff, which carries fertilizer and other nutrients into the Gulf. Phytoplankton blooms around river mouths spread. When the creatures die and sink to the bottom, their decomposition strips oxygen from the water, creating inhospitable conditions for other marine life. The lack of oxygen is called hypoxia.

"We saw no hypoxia in this area until June of last year, and this year we found it in late March," Steve DiMarco of Texas A&M University said Tuesday. "If the physical conditions we noticed continue, it could mean an unusually strong hypoxic zone this year, and that's not good news." Fishing crews, which have noticed the dead zones for decades, are forced to venture farther to make a catch.

The dead zone is centered along the Louisiana coast where the Mississippi and Atchafalaya Rivers empty into the gulf. It typically develops in late spring and early summer, on the heels of floods and generally heavy runoff. The Mississippi drains 40 percent of U.S. land area and accounts for almost 90 percent of the freshwater flowing into the Gulf of Mexico. The runoff creates stratification, a tendency for the influx of fresh water and salt water to not mix. "During January and February of this year, the flow of the Mississippi River was larger than at any time in 2004," DiMarco said. "That means the stratification levels between the fresh river water and heavier salt water could results in increased hypoxia."

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