The annual dead zone in the Chesapeake Bay is expected to be smaller than average this summer, according to a forecast released by the Chesapeake Bay Program and scientific partners.
Low river flows and reduced nitrogen pollution entering the Bay this spring are the main reasons for the milder outlook. From January through April 2026, river flow into the Bay was 32% below the long-term average, while nitrogen loads were 39% lower than average, totaling about 59 million pounds.
Scientists predict the total annual hypoxic volume — a measure that accounts for both the size and duration of low-oxygen areas — will be about 31% below the long-term average. The severity of this year’s dead zone is expected to rank among the lowest 10% of years since extensive monitoring began in 1985.
“This year’s forecast suggests that the Chesapeake Bay may experience one of its milder dead zones in recent decades,” said Aaron Bever, senior managing scientist with FlowWest. “Lower nitrogen loads entering the Bay this spring are expected to translate into better oxygen conditions for fish, crabs, oysters and other Bay life this summer.”
Dead zones form when excess nutrients, primarily nitrogen and phosphorus, fuel large algal blooms. When the algae die and decompose, they consume oxygen in the water, creating areas where fish, crabs, and other marine life struggle to survive. These conditions are influenced by both nutrient pollution from human activities and year-to-year weather patterns.
Dr. Peter Tango, monitoring coordinator with the U.S. Geological Survey at the Chesapeake Bay Program, noted that this year’s milder conditions are welcome compared to years with higher river flows and nutrient loads that create larger and longer-lasting areas of low oxygen.
While the forecast is positive, scientists caution that summer weather conditions — such as heavy rainfall, heat waves, or extended calm periods — can still affect the size and duration of the dead zone. These factors are difficult to predict months in advance and add some uncertainty to the outlook.
Alison Hooper Prost, Senior Vice President for Programs at the Chesapeake Bay Foundation, welcomed the smaller forecast but emphasized that dry weather alone will not restore the Bay. She noted that the long-term trend for the region points toward wetter weather and more intense storms, which can increase polluted runoff. Prost called for continued action on the updated Chesapeake Bay Watershed Agreement, including sustained funding for monitoring and pollution reduction efforts.
Researchers will conduct a full assessment of the dead zone’s extent and duration in the fall. Throughout the summer, conditions can be tracked through the Chesapeake Bay Environmental Forecast System and Maryland Department of Natural Resources hypoxia reports.
For Southern Maryland communities along the Chesapeake Bay and its tributaries, the size of the dead zone directly affects water quality, fisheries, and the local economy. Blue crabs, fish, and oysters are important to both commercial watermen and recreational users in Calvert, Charles, and St. Mary’s counties. Milder conditions this summer could support better habitat for these species during critical months.
Chesapeake Bay Program partners continue to work on reducing nutrient pollution from wastewater treatment plants, agricultural lands, and urban and suburban areas through conservation practices and infrastructure improvements. These long-term efforts remain essential to improving the Bay’s overall health and resilience, regardless of annual weather variations.
