On June 23, 2015, federal and state scientists working on the Chesapeake Bay announced the prediction for 2015 of the so-called “dead zone” in the Bay—that is, the area where dissolved oxygen levels are expected to be too low to support the Bay’s normal community of organisms (that condition is called “hypoxia”). The maximum volume affected by mid-summer is predicted to be approximately 1.37 cubic miles, about 10 percent lower than the long-term average as measured since 1950. More details are given below in an excerpt from the U.S. Geological Survey’s 6/23/15 news release on the prediction for 2015.
For “dead zone” predictions from previous years, plus access to various annual “report cards” of dissolved oxygen and other conditions in the Bay and several tributaries, see the “Ecocheck” Web site provided by the University of Maryland’s Center for Environmental Science, online at http://ian.umces.edu/ecocheck/forecast/chesapeake-bay/2015/.
Excerpt from Scientists Expect Slightly Below Average Chesapeake Bay ’Dead Zone’ this Summer; Low river flow and nutrient loading reason for smaller predicted size – U.S. Geological Survey news release, 6/23/15.
“Scientists are expecting that this year’s Chesapeake Bay hypoxic low-oxygen zone, also called the ‘dead zone,’ will be approximately 1.37 cubic miles—about the volume of 2.3 million Olympic-size swimming pools. While still large, this is 10 percent lower than the long-term average as measured since 1950.
“The anoxic portion of the zone, which contains no oxygen at all, is predicted to be 0.27 cubic miles in early summer, growing to 0.28 cubic miles by late summer. Low river flow and low nutrient loading from the Susquehanna River this spring account for the smaller predicted size.
“This is the ninth year for the Bay outlook which, because of the shallow nature of large areas of the estuary, focuses on water volume or cubic miles, instead of square mileage as used in the Gulf of Mexico dead zone forecast announced last week. …
“The Bay’s hypoxic and anoxic zones are caused by excessive nutrient pollution, primarily from human activities such as agriculture and wastewater. The nutrients stimulate large algal blooms that deplete oxygen from the water as they decay. 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 important fisheries.
“The Chesapeake Bay Program coordinates a multi-year effort to restore the water and habitat quality to enhance its productivity. The forecast and oxygen measurements taken during summer monitoring cruises are used to test and improve our understanding of how nutrients, hydrology, and other factors affect the size of the hypoxic zone. They are key to developing effective hypoxia reduction strategies.
“The predicted ‘dead zone’ size is based on models that forecast three features of the zone to give a comprehensive view of expected conditions: midsummer volume of the 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.”