Scientists are expecting a slightly above average “dead zone” in the Chesapeake Bay this year, and an average, but still large, size hypoxic area in the Gulf of Mexico. The forecast for the Chesapeake Bay predicts a slightly larger than average dead zone in the nation's largest estuary.
"Monitoring the largest dead zones in the United States is critical as we work to preserve and protect our coastal ecosystems,” said Donald Boesch, president of the University of Maryland Center for Environmental Science. “Our continuing efforts to respond to the challenges in the Chesapeake Bay will aid communities around the world who are confronting increasing coastal hypoxia.”
The Chesapeake forecast predicts a midsummer low-oxygen hypoxic zone of 1.97 cubic miles and 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.
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 impact the size of dead zones.
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.
NOAA-supported modeling is also forecasting this year's Gulf of Mexico hypoxic zone to cover an area ranging from about 4,633 to 5,708 square miles (12,000 to 14,785 square kilometers) or about the size of the State of Connecticut.
While close to average since the late 1900s, these hypoxic zones are many times larger than what research has shown them to be prior to the significant human influences that greatly expanded their sizes and impacts.
The Gulf of Mexico prediction is based on an ensemble of 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.
“We are making progress at reducing the pollution in our nation’s water that leads to ‘dead zones,’ but there is more work to be done,” said Kathryn D. Sullivan, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. "These ecological forecasts are good examples of the critical environmental intelligence products and tools that NOAA is providing to interagency management bodies such as the Chesapeake Bay Program and Gulf Hypoxia Task Force. With this information, we can work collectively on ways to reduce pollution and protect our marine environments for future generations.”
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.
USGS nutrient-loading estimates for the Mississippi River and Chesapeake Bay are used in the hypoxia forecasts for the Gulf and Chesapeake Bay. The Chesapeake data are funded with a cooperative agreement between USGS and the Maryland Department of Natural Resources. USGS operates more than 65 real-time nitrate sensors in these two watersheds to track how nutrient conditions are changing over time.
