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Sunday, December 5, 2021
FairfaxNewsNew report serves up good news for Chesapeake Bay

New report serves up good news for Chesapeake Bay

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A smaller than average “dead zone” due to reduced river flows, as well as less nutrient and sediment pollution, will benefit the Chesapeake Bay and the plant and animal life that relies on it, according to a new yearly estimate.

Researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey are forecasting a lower than usual dead zone for the second year in a row, and attributed it, in part, to management actions taken across the Chesapeake Bay watershed.

Dr. Jeremy Testa, an associate professor at the Chesapeake Biological Laboratory at the University of Maryland Center for Environmental Science, called the news “an example of a positive trajectory for the Bay.”

“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,” Testa said. “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.”

“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 percent lower than average, while the volume of water with no oxygen is predicted to be 18 percent lower than average.

The level of pollution reaching the Chesapeake Bay each year varies due to the amount of spring rainfall that impacts river flows coming from Delaware, the District of Columbia, Maryland, New York, Pennsylvania, Virginia and West Virginia, and has seen reductions due to efforts of those states and other partners.

The U.S. Geological Survey, in partnership with Maryland and Virginia officials, monitors nitrogen loads and other important pollutants flowing into the Bay from 78 percent of the watershed. The hypoxia forecast model, enhanced in 2020, allows for projections for an average July, average summer and the total annual hypoxic volume, and is based on the monitoring of nitrogen pollution and river flow at the nine monitoring stations along the Appomattox, Choptank, James, Mattaponi, Pamunkey, Patuxent, Potomac, Rappahannock and Susquehanna rivers.

“These annual forecasts are a fine example of the collaboration that brings together high-quality monitoring data and cutting-edge science to support Chesapeake Bay restoration efforts,” said Joel Blomquist, a hydrologist with the U.S. Geological Survey.

Excess nutrients drive the growth of algae blooms, which eventually die and decompose, removing oxygen from the surrounding waters faster than it can be replenished. This creates low-oxygen conditions. Plant and animal life are often unable to survive in this environment.

“Less hypoxia is important, as it means better habitat for our iconic Bay species, such as crabs, oysters and striped bass,” said Tom Parham, director of the Tidewater Ecosystem Assessment of the Maryland Department of Natural Resoruces.

Though different types of nutrients contribute to the annual dead zone, the amount of nitrogen that enters the Bay from January to 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 percent below average, within the normal range.

Weather conditions also play a role in the size and duration of the annual dead zone. Heavy rainfall can lead to strong river flows entering the Bay, which carries along increased amounts of nutrient and sediment pollution.
Above average spring freshwater flows to the Bay, along with hot temperatures and weak winds in the summer, provide the ideal conditions for the dead zone to grow larger and last longer.

(A Bay-wide assessment of the 2021 dead zone will be available this fall. In 2020, the Virginia Institute of Marine Science reported the dead zone to be smaller than 80 percent of those monitored since 1985.)

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