Maryland Department of Natural Resources monitoring data show that dissolved oxygen conditions in the Maryland portion of the Chesapeake Bay mainstem were average in early July 2020. The hypoxic water volume — waters with less than 2 mg/l oxygen — was 1.35 cubic miles compared to a historical early July average (1985-2019) of 1.38 cubic miles. Low dissolved oxygen extended into the Virginia Chesapeake Bay mainstem for an additional 0.35 cubic miles of hypoxia, for a total baywide estimate of 1.7 cubic miles. Based on historical data, bay hypoxia volumes historically peak during the early portion of July. No anoxic zones — areas with less than 0.2 mg/l oxygen — were observed in the Maryland or Virginia bay mainstem.

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

In June, the Chesapeake Bay Program, U.S Geological Survey, University of Maryland Center for Environmental Science, and University of Michigan scientists released their prediction for slightly smaller-than-average 2020 hypoxic conditions based on slightly less-than-average water and nitrogen flows into the bay from January to May 2020. Monitoring results thus far have matched that forecast.

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 to 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.