Bay’s dead zone expected to be smaller this summer

By Linda Cicoira

The Chesapeake Bay’s annual dead zone is expected to be relatively mild this summer, scientists at William & Mary’s Batten School & VIMS, FlowWest, and the University of Maryland’s Center for Environmental Science agreed late last week.

Dead zones in the Chesapeake Bay are areas where low-oxygen, or hypoxic conditions, make it difficult for blue crabs, fish, and other marine life to survive. Hypoxia occurs when excess nutrients, such as nitrogen, fuel large algal blooms that eventually die and consume oxygen from the waters as they decompose.

According to the newly released 2026 Hypoxia Forecast, dead zone severity is predicted to be in the lowest 10 percent since extensive monitoring began in 1985, and below about 31 percent of the long-term average.

“This year’s forecast suggests that the … Bay may experience one of its milder dead zones in recent decades,” said Aaron Bever, senior environmental 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.”

While the forecast predicts a milder year, scientists say summer weather conditions, including heavy rains, heat waves, or extended calms, can still influence the size and duration of the dead zone and remain difficult to predict.

The favorable outlook is largely due to low river flows and reduced nitrogen pollution entering the Bay earlier in the year.

From January to April 2026, the amount of water entering the Bay from rivers was 32 percent below the long-term average, while the amount of nitrogen was 39 percent less than average, or about 59 million pounds of nitrogen.

Nitrogen load estimates from the U.S. Geological Survey were used to forecast the Bay’s total annual hypoxic volume. The metric reflects both the extent of low-oxygen waters and the duration of those conditions.

Long-term efforts to reduce nutrient runoff from wastewater treatment plants, agricultural lands, urban and suburban landscapes, and other sources have helped improve the Bay’s resilience. The scientists report that those gains are especially important as warming temperatures and changing precipitation patterns can intensify low-oxygen conditions and make continued progress more challenging.

“Annual forecasts, daily environmental predictions, and fall assessments each provide a different but complementary view of Chesapeake Bay conditions,” said Marjy Friedrichs, research professor at the Batten School of Coastal & Marine Sciences & VIMS. “Together, they help us understand how the Bay is responding to nutrient reductions, climate variability, and year-to-year weather, while also providing useful information for people who use and depend on the Bay.”

This year’s annual dead zone forecast complements the Chesapeake Bay Environmental Forecasting System or CBEFS, which provides five-day forecasts of conditions including sea nettles, harmful algal blooms, salinity, temperature, dissolved oxygen, and pH.