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NOAA, Partners Predict Average 'Dead Zone' for Gulf of Mexico; Slightly Above-average in Chesapeake Bay

Hypoxic zones, often called 'dead zones,' are areas in the ocean of such low oxygen concentration that animal life suffocates and dies.

animation of nutrient pollution run off into Gulf of Mexico

Invisible Menace

Hypoxic zones are areas in the ocean of such low oxygen concentration that animal life suffocates and dies, and as a result are sometimes called "dead zones." One of the largest dead zones forms in the Gulf of Mexico every spring. Each spring as farmers fertilize their lands preparing for crop season, rain washes fertilizer off the land and into streams and rivers. Learn more with this video visualization

Scientists are expecting an average, but still large, hypoxic or "dead zone" in the Gulf of Mexico this year, and slightly above-average hypoxia in the Chesapeake Bay. 

NOAA-supported modeling is forecasting this year's Gulf of Mexico hypoxic zone to cover an area ranging from about 4,633 to 5,708 square miles, or about the size of the state of Connecticut.

A second NOAA-funded forecast, for the Chesapeake Bay, predicts a slightly larger than average dead zone in the nation's largest estuary. The forecast predicts a mid-summer low-oxygen hypoxic zone of 1.97 cubic miles, an early-summer oxygen-free anoxic zone of 0.51 cubic miles, with the late-summer oxygen-free anoxic area predicted to be 0.32 cubic miles. Because of the shallow nature of large areas of the estuary the focus is on water volume or cubic miles, instead of square mileage as used in the Gulf.

The dead zone in the Gulf of Mexico affects nationally important commercial and recreational fisheries and threatens the region's economy. The Chesapeake Bay dead zones, which have been highly variable in recent years, threaten a multi-year effort to restore the water and habitat quality to enhance its production of crabs, oysters, and other important fisheries.

Later this year, researchers will measure oxygen levels in both bodies of water. The confirmed size of the 2014 Gulf hypoxic zone will be released in late July or early August, following a mid-July monitoring survey led by the Louisiana Universities Marine Consortium. The final measurement in the Chesapeake will come in October following surveys by the Chesapeake Bay Program's partners from the Maryland Department of Natural Resources and the Virginia Department of Environmental Quality.


The Gulf of Mexico prediction is based on models developed by NOAA-sponsored modeling teams and individual researchers at the University of Michigan, Louisiana State University, Louisiana Universities Marine Consortium, Virginia Institute of Marine Sciences/College of William and Mary, Texas A&M University, and the U.S. Geological Survey,  and relies on nutrient loading estimates from the USGS. The models also account for the influence of variable weather and oceanographic conditions, and predict that these can affect the dead zone area by as much as 38 percent.  

The Chesapeake Bay prediction is based on models developed by NOAA-sponsored researchers at the University of Maryland Center for Environmental Science, University of Michigan, and again relies on nutrient loading estimates from USGS.

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Hypoxic (very low oxygen) and anoxic (no oxygen) zones are caused by excessive nutrient pollution, primarily from human activities such as agriculture and wastewater, which results in insufficient oxygen to support most marine life and habitats in near-bottom waters. Aspects of weather, including wind speed, wind direction, precipitation, and temperature, also affect the size of dead zones.


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