Chesapeake Bay hypoxia levels remained below average through August 2026

Hypoxia levels in the Chesapeake Bay remained significantly below average for much of August 2026. Data from the Maryland Department of Natural Resources and Old Dominion University indicate that early August hypoxic volumes—waters with less than 2 milligrams of oxygen per liter—ranked as the fifth-smallest observed for that period in over three decades.

By late August, hypoxic volumes rose to 1.12 cubic miles, slightly exceeding the long-term average of 1.06 cubic miles. Anoxia, a more severe form of oxygen depletion, measured between 0.23 and 0.25 cubic miles during the month, which was lower than levels recorded in July.

Researchers attribute the milder-than-usual dead zone conditions to ongoing drought within the Chesapeake watershed. The drought has reduced the volume of water and nutrient pollution, such as nitrogen and phosphorus, flowing into the Bay. Lower nutrient loading limits the algal blooms that typically decompose and strip oxygen from deeper waters.

Dead zones pose a risk to aquatic life, as low oxygen levels shrink available habitats for fish, crabs, and other organisms. While mobile animals can often relocate to oxygen-rich waters, those unable to move face higher mortality risks.