Chesapeake Bay Hypoxia Report – June 2023

Dissolved oxygen conditions among the best recorded

Data collected by the Maryland Department of Natural Resources and Old Dominion University show that June 2023 dissolved oxygen conditions in the Chesapeake Bay mainstem of Maryland and Virginia were much better than average. The results are from samples collected during regular monitoring cruises conducted by research vessels.

The hypoxic water volume — waters with less than 2 mg/l oxygen — was 0.22 and 0.33 cubic miles during the early and late June monitoring cruises, compared to early and late June averages of 0.87 and 1.30 cubic miles since 1985. This year’s data from early June ranks as the second smallest volume of hypoxic water volume on record and late June was the smallest volume for their respective time periods. No anoxia  – areas of water with less than 0.2 mg/l oxygen – was observed in either June monitoring cruise.

In May, Hypoxia was essentially zero – 0.007 cubic miles.

Maryland and Virginia combined results are comparable to the yearly seasonal forecast by the U.S. Environmental Protection Agency’s Chesapeake Bay Program, U.S. Geological Survey, University of Maryland Center for Environmental Science, and University of Michigan.

In late June, this forecast expected Chesapeake Bay mainstem hypoxic volume to be 33% lower than the 38-year average, due to reduced river flows from January through May 2023, as well as less nitrogen carried to the Bay because of nutrient management efforts. Maryland and Virginia’s monitoring results thus far have matched the forecast of better-than-average conditions.

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.

Ongoing efforts to reduce nitrogen and phosphorus pollution from industrial sources, agricultural land, and cities and towns are aimed at reducing hypoxic conditions in the Bay. In the water, nitrogen and phosphorus fuel algal blooms that remove oxygen from the water when they die off. 

Each year from May through October, the Department of Natural Resources computes hypoxia volumes from the water quality data collected by department staff and the Virginia Department of Environmental Quality. Data collection is funded by these states and the Chesapeake Bay Program. Bay hypoxia monitoring and reporting will continue through the summer. Additional Maryland water quality data and information, including the Department of Natural Resources hypoxic volume calculation methods, can be found on the Eyes on the Bay website