A “dead zone” with little or no oxygen content that forms each summer across the bottom of the Chesapeake Bay is forecast to be one of the largest on record in 2019.
Rivers have been flowing above normal for the past year, washing an excess of farm fertilizer and sewage pollution into the bay. Those nutrients feed large blooms of algae; the plants strip oxygen from the water when they die and decompose.
The dead zone can kill crabs, oysters and fish, and limits the livable habitat in the bay. Those creatures rely on dissolved oxygen, absorbed into the water from the air and also released by underwater plant life, to breathe.
Scientists at the University of Maryland Center for Environmental Science and University of Michigan said Wednesday they expect oxygen levels will drop harmfully low across about 2.1 cubic miles of the Chesapeake this summer.
They predict an area of about half a cubic mile will contain no dissolved oxygen whatsoever.
Those forecasts suggest one of the Chesapeake’s four largest dead zones of the past 20 years will form this summer, the scientists said. They have been measuring the bay’s dead zone since 1950, and the 30-year mean maximum dead zone volume is 1.74 cubic miles.
Record rainfall fell across much of the Chesapeake watershed in 2018, including nearly 72 inches at Baltimore-Washington International Thurgood Marshall Airport. That surge of stormwater, and the pollution it carries with it, has already been blamed for other setbacks in the bay’s health in recent months.