Gulf dead zone could be largest-ever by 10 percent -- USGS

This year's dead zone in the Gulf of Mexico could be as much as 10 percent larger than ever before, rendering a swath of ocean stretching from the mouth of the Mississippi River to Texas devoid of fish, shellfish or other marine life, the U.S. Geological Survey announced today.

The announcement confirms what scientists have been predicting for weeks: that record flooding along the Mississippi River has soaked up and delivered a well-above-average dose of nitrogen pollution from fertilized fields and urban areas in the basin to the Gulf (Greenwire, May 26). The nutrient pollution feeds a massive algae bloom that ultimately consumes the dissolved oxygen necessary to support ocean life.

USGS predicts this year's dead zone could measure between 8,500 and 9,421 square miles. The dead zone, which appears every summer, has averaged 6,000 square miles in the past five years, USGS said. The largest ever measured spanned more than 8,400 square miles in 2002.

Scientists found that May flow rates along the Mississippi and Atchafalaya rivers were nearly twice the normal rates, carrying significantly more nitrogen than normal into the Gulf. According to USGS estimates, 164,000 metric tons of nitrogen flowed into the Gulf -- 35 percent more than the average May load estimated in the last 32 years.

"While there is some uncertainty regarding the size, position and timing of this year's hypoxic zone in the Gulf, the forecast models are in overall agreement that hypoxia will be larger than we have typically seen in recent years," said National Oceanic and Atmospheric Administration chief Jane Lubchenco.

The actual size of this year's dead zone, or hypoxic zone, will be released following a NOAA-supported monitoring survey led by the Louisiana Universities Marine Consortium between July 25 and Aug. 6.

The data are collected annually, as required by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, which has set a target size for the dead zone of 1,900 square miles.

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