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Maryland Department of Natural Resources monitoring data show that dissolved oxygen conditions in the Maryland portion of the Chesapeake Bay mainstem were better than average in early August 2020. The hypoxic water volume — waters with less than 2 mg/l oxygen — was 0.92 cubic miles compared to a historical early August average (1985-2019) of 1.2 cubic miles. 

Oxygen conditions improved from late July to early August, with the early August hypoxic volume being nearly half the volume observed in late July. Early August conditions ranked 10th best out of the 36-year monitoring record for the period. An additional 0.24 cubic miles of hypoxia was observed in Virginia Chesapeake Bay mainstem waters.

No anoxic zones — areas with less than 0.2 mg/l oxygen — were observed in the Maryland or Virginia mainstem eyes.

Better conditions can be partially attributed to oxygen mixing into deeper waters following the winds of Tropical Storm Isaias on Aug. 4. Lower bay sampling began Aug. 6, and upper bay sampling was completed Aug. 11.

Maryland’s water quality data can be further explored with a variety of online tools at the department’s Eyes on the Bay website.

Crabs, fish, oysters, and other creatures in the Chesapeake Bay require oxygen to survive. Scientists and natural resource managers study the volume and duration of bay hypoxia to determine possible impacts on bay life.

Each year (June-September), the Maryland Department of Natural Resources computes these volumes from data collected by Maryland and Virginia monitoring teams during twice-monthly monitoring cruises. Data collection is funded by these states and the Environmental Protection Agency’s Chesapeake Bay Program.

Bay hypoxia monitoring and reporting will continue through the summer.


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