The 2016 mid-summer Chesapeake Bay hypoxic low-oxygen zone or “dead zone” will be approximately 1.58 cubic miles, roughly average, according to a two university study sponsored by the National Oceanic and Atmospheric Administration (NOAA).
The nutrient loading, from the mouth of the Susquehanna River in Havre de Grace, Maryland, accounts for the 10 percent smaller predicted size of hypoxic areas in the Bay this summer.
The anoxic portion of the zone, which contains no oxygen at all, is predicted to be 0.28 cubic miles in early summer, growing to 0.31 cubic miles by late summer, both of which are smaller than average. Low river flow and low nutrient loading from the Susquehanna and Potomac rivers this spring account for the smaller predicted size of the anoxic portion.
The Bay’s hypoxic and anoxic zones are caused by excess nutrient pollution, primarily from human activities such as agriculture and wastewater. The low oxygen levels are insufficient to support most marine life and habitats in near-bottom waters and threaten the Bay’s production of crabs, oysters, and other fisheries.
The predicted “dead zone” size is based on models that forecast three of its features: midsummer low-oxygen hypoxic zone, early-summer oxygen-free anoxic zone, and late-summer oxygen-free anoxic zone.
The models were developed by NOAA-sponsored researchers at the University of Maryland Center for Environmental Science and the University of Michigan. They rely on nutrient loading estimates from the U. S. Geological Survey.
USGS provides nutrient runoff and river stream data used in the forecast models. USGS estimates that the Susquehanna River delivered 66.2 million pounds of nitrogen to the Bay from January to May 2016, which is 17 percent below average conditions.
The data are funded through a cooperative agreement between USGS and the Maryland Department of Natural Resources. USGS operates more than 400 real-time stream gauges and collects water quality data at numerous long-term stations throughout the Chesapeake Bay basin to track how nutrient loads are changing over time.
Later this year researchers will measure oxygen levels in the Chesapeake Bay, based on surveys by the Chesapeake Bay Program’s partners from the Maryland Department of Natural Resources and the Virginia Department of Environmental Quality.
The history of hypoxia in the Chesapeake Bay since 1985 can be found at EcoCheck, a website from the University of Maryland Center for Environmental Science.
source: National Oceanic and Atmospheric Administration