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COCODRIE, La. (AP) — The Gulf of Mexico's dead zone, where there is too little oxygen to support sea life, covered a record 8,006 square miles this year, university researchers said Thursday.

The dead zone is about the size of the state of Massachusetts.

The zone near the Mississippi River delta stretched west into Texas waters this year, chief scientist Nancy Rabalais said. Researchers did not map the entire area off Texas, so the figure is probably low, she said.

The research was done by a group of Louisiana universities as well as Florida State University and Texas A&M at Galveston.

The dead zone is formed where Mississippi River freshwater enters the salty Gulf. Microscopic plants called phytoplankton feed on nitrogen and phosphorus in the river water, but when they die, they decompose and use up the oxygen in the Gulf.

Around the edges of the dead zone, the oxygen-starved water is a thin layer near the sea floor. In other areas it rises 40 to 50 feet above the bottom, Rabalais said. It begins near shore and stretches out as far as 50 miles.

The layers formed by the light freshwater and heavier seawater don't mix unless a storm stirs up the waters. Tropical Storm Allison broke up the oxygen-starved zone, but since mid-June it has re-formed.

The previous largest dead zone measurement was 7,728 square miles in 1999. Wind patterns and drought throughout the Mississippi Basin last year reduced the area to 4,000 square miles, Rabalais said.

That reduction and the increase after this year's heavy rains is yet more evidence that fertilizer and sewage runoff carried by the Mississippi and Atchafalaya rivers fuel creation of the dead zone, Rabalais said.

The research is funded by the National Oceanic and Atmospheric Administration, Coastal Ocean Program.

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