July 25, 2009

Gulf Dead Zone Smaller This Year

A scientist reported Friday that the Gulf of Mexico's "dead zone," where low amounts of oxygen in the water make it hard for anything to live there, is less than half the size as predicted earlier this year.

Every year in the gulf bacteria, Which feed on algae blooms from the flow of farming runoff and other nutrients from the Mississippi River, cause the notorious hypoxic area to form in the Gulf.

According to Nancy Rabalais, a researcher that specializes in the problem for the Louisiana Universities Marine Consortium, the area this year covers an area of 3,000 square miles, stretching from nearly the bottom to the surface. This hypoxic area is one of the smallest since 2000.

Scientists has predicted that this year's zone would be 7,500 to 8,500 square miles.

Rabalais wrote that the possible reasons for the difference include high winds and waves that helped mix more oxygen into some of the waters.

"This was surprisingly small given the forecast to be among the largest ever and the expanse of the dead zone earlier this summer," she said.

Hypoxia occurs when algae blooms - which nitrates and phosphates feed on - die and fall to the bottom.  While this happens the wind dies down, meaning that fresh water coming out of the rivers does not get mixed into the denser salt water below it.  Then microbes that feed on the dead algae use up oxygen from the bottom up, creating the dead zone.

In some areas where the oxygen was lowest, according to Rabalais, crabs, eels and shrimp, which are usually seen swimming on the bottom of the ocean, were seen swimming at the surface.

Other studies show that severely low oxygen levels in early July contributed to "jubilees," which is forced movement of fish, crabs and shrimp into shallow waters, off Grande Isle.

Monday, Rabalais and other researchers are expected to discuss the hypoxic problem through a telephone news conference with Jane Lubcheno of the National Oceanic and Atmospheric Administration (NOAA).

"We want to raise some of the issues behind it and some of the debate about the changes needed to shrink it," NOAA spokesman Ben Sherman said Wednesday.

According to researcher Robert Diaz of Virginia Marine Institute, the Gulf's dead zone is the largest of 250 hypoxic areas in the U.S. waters.


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