Chesapeake Bay

Scientists predict a smaller dead zone in the Chesapeake Bay this summer.

ANNAPOLIS — Researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey announced June 23 that they are forecasting, for the second year in a row, a smaller than average “dead zone” due to reduced river flows entering the Chesapeake Bay, as well as less nutrient and sediment pollution thanks to the management actions taken across the watershed to improve water quality.

“This year’s forecast suggests a smaller dead zone than is typical because the river flows that carry nutrients to the Bay were slightly lower than normal. But the amount of nutrients carried to the Bay by a given amount of flow has lessened over time due to effective nutrient management in the watershed. This is an example of a positive trajectory for the Bay,” said Dr. Jeremy Testa, associate professor, Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science.

Hypoxic and anoxic regions, which are areas of low and no oxygen, respectively, are caused by excess nutrient pollution flowing into the Bay. Compared to the last 35 years, this year’s Chesapeake Bay hypoxic volume, or “dead zone”, is predicted to be 14% lower than average, while the volume of water with no oxygen is predicted to be 18% lower than average. In 2020, the Virginia Institute of Marine Science reported the dead zone to be smaller than 80% of those monitored since 1985.

The levels of pollution reaching the Chesapeake Bay each year varies due to the amount of spring rainfall that impacts river flows. Additionally, the many efforts of Chesapeake Bay Program partners — Delaware, the District of Columbia, Maryland, New York, Pennsylvania, Virginia, West Virginia, academic institutions, local governments, federal agencies and non-governmental organizations — are making a difference in gradually reducing the amount of nutrient and sediment pollutants that are entering the Bay.

“Less hypoxia is important as it means better habitat for our iconic Bay species, such as crabs, oysters and striped bass. The Maryland Department of Natural Resources will be working with our fellow Chesapeake Bay Program partners to monitor and report on the 2021 hypoxia,” said Tom Parham, director, Tidewater Ecosystem Assessment, Maryland Department of Natural Resources,

Though different types of nutrients contribute to the annual dead zone, the amount of nitrogen that enters the Bay from January-May is a key driver in how hypoxic conditions can vary from year-to-year. In spring 2021, river flows entering the Bay were 13% below average, but still fell within the normal range. Nine river input monitoring stations located on major Bay tributaries showed that the Chesapeake received 19% less nitrogen pollution when compared to the long-term average. Overall, nitrogen loads entering the Bay included an estimated 98 million pounds recorded at the nine river input monitoring stations, as well as an additional 6.6 million pounds from treated wastewater discharge and non-point sources (e.g., agricultural, stormwater and urban runoff) located downstream of these stations.

A Bay-wide assessment of the 2021 dead zone will be available this fall.

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