This year, the oxygen-deprived “dead zone” that plagues the Chesapeake Bay every summer was much larger than in 2020 but similar in size to those of other recent years. This measure, like others, points to the complexities of tracking the Bay’s progress toward ecological improvement, especially amid a changing climate.

Reducing nutrient pollution, which causes the annual “dead zone” in the Chesapeake Bay, is one of the primary goals of the Bay cleanup effort. Dave Harp

Dead zones refer to deep areas of the Chesapeake where low oxygen levels render them off-limits to most aquatic animals. This happens when algae blooms, fed by excess nutrient pollution, die and decompose, removing oxygen from the water faster than it can be replenished. Plant and animal life are often unable to survive in such hypoxic conditions, which have been dubbed “dead zones.”

The Chesapeake Bay Program, a regional partnership that leads the Bay restoration effort, monitors nutrient and oxygen levels from May to October to track the hypoxic conditions that peak in the Bay each summer.

In 2020, the region posted the smallest observed dead zone since 1985. This year, though, the dead zone size was near average compared with historical data. But it also lasted longer than the dead zones in 89% of other recorded years.

Scientists pointed to the ways in which climate change influenced conditions in this year’s dead zone, including increased precipitation and warmer temperatures in August and September.

“This year’s estimate of the Chesapeake’s ‘dead zone’ illustrates the challenge between Chesapeake Bay Program management actions and climate change that brings increased rainfall volume and river flows,” said Michelle Price-Fay, acting director of the U.S. Environmental Protection Agency’s Chesapeake Bay Program Office. “While the long-term trend is toward a reduction in hypoxia due to management actions taken throughout the watershed and airshed, warming from climate change is a headwind that may increase hypoxia’s duration and extent.”

This article originally appeared on on Wednesday, December 1, 2021.

Whitney Pipkin is a Bay Journal staff writer based in Virginia. You can reach her at

Leave a comment

Leave a Reply