Gulf dead zone triple forecasted size

COCODRIE — Local scientists on a cruise to the Gulf of Mexico last week discovered the dead zone is triple the size their federal colleagues predicted earlier this summer.

Last month, National Oceanic and Atmospheric Administration researchers forecast that the dead zone, or amount of dissolved oxygen killing marine life in the ocean, would be 1,400 square miles, the smallest in 15 years.

But in a weeklong trip that ended Saturday, scientist Nancy Rabalais and her 12 coworkers found otherwise.

Rabalais, executive director of the Louisiana Universities Marine Consortium in Cocodrie, said the dead zone mapped during the Gulf Coast excursion last week is 4,564 square miles, or slightly smaller than the state of Connecticut.

But it could grow to 6,200 square miles if major storms do not stir up the Gulf in the coming months.

The zone, which forms in June when polluted water from the Mississippi and Atchafalaya rivers dump into the Gulf, stretches from the Mississippi River to the state’s border with Texas.

A larger-than-anticipated dead zone means fishermen will have a smaller area in which to trawl. It also confirms that pollutants from farms and factories in Northern states continue to have a major impact on the quality of water and marine life along south Louisiana’s shore, said Rabalais.

"Nutrient loads from the river still dictate the dead-zone size," said Rabalais. "To get smaller, nutrients need to be reduced, and there needs to be more management."

Rabalais and a dozen scientists spent eight days exploring the dead zone aboard a ship named Pelican. Their findings, released Monday, accompany a new map that follows the roller-coaster pattern of Louisiana’s marshy coast. The zone is formed when elevated amounts of water, pollutants and nutrients from the North are discharged into the Gulf, where they form massive, oxygen-starved pools where fish and marine life cannot grow.

While the dead zone is larger than NOAA forecasted, it is slightly smaller than the long-term average of 4,800square miles. Scientists began mapping hypoxia in 1985 when the connection was made between low oxygen in the ocean and the failure to catch fish, shrimp and crabs in bottom-dragging nets.

The dead zone’s size varies each year. Last year’s was 5,800-square miles.

The biggest zone on record was

8,500, slightly smaller than New Jersey, in 2002.

During the Pelican’s research excursion, a team of scientists took water samples at various spots along the coast, from southwest pass to Barataria, Fourchon, Cocodrie, Atchafalaya and western Texas. Using electronic probes, the group found that the water depths impacted by low oxygen ranged from 20 feet to 85 feet. The dead zone also was smaller between the Mississippi River and the Atchafalaya in central Louisiana than between the Atchafalaya delta and Calcasieu estuary to the west.

The dead-zone map that resulted from these findings is based on a model developed by Eugene Turner of Louisiana State University, an investigator on the hypoxia research team. Turner predicted this summer’s dead zone would be 6,200-square miles. Like NOAA forecasters, Turner’s prediction was off the mark, but Rabalais said he was more on target than the federal scientists because he took last year’s data into account.

The dead zone is smaller than average because nutrients flowing down the Mississippi River were also lower than normal, most likely because of below-average precipitation across the river basin.

The purpose of studying the dead zone is to improve assessments of its causes and consequences. A federal hypoxia task force plans to reassess its action plan for states bordering the Mississippi River over the next several months. The 7-year-old panel will study the Gulf Coast dead zone at a meeting in St. Louis, Mo., in October and another one in March, said Rabalais, who will present her findings to the task force.

"The real issue is getting money to do the work that needs to be done," such as conservation for farmers, said Rabalais. Other issues impacting the dead zone include runoff from developed land, atmospheric deposition, soil erosion and agricultural fertilizers. Sewage and industrial discharges also contribute nutrients.

The scientific party that mapped this summer’s zone included researchers from LUMCON, LSU, Harvard School of Public Health and Nicholls State. The expedition was paid for with money from NOAA’s Center for Sponsored Coastal Ocean Research.

Senior Staff Writer Kimberly Solet can be reached at 857-2209 or kimberly.solet@houmatoday.com.