"The Chesapeake dead zone forms annually as a consequence of the amount of pollution—particularly nitrogen and phosphorus—that enters the Bay from its watershed. But it is the weather that impacts its spread and how long it will last each year. Meaning that if climate change continues to negatively impact the Bay, the dead zone may stay around even longer and become more severe in the years to come.

The “dead zone” is an area of little to no oxygen that forms in Bay waters when excess nitrogen and phosphorus, otherwise referred to as nutrients, enter the water through polluted runoff and feed naturally-occurring algae. This causes algae blooms to grow and then eventually die off and decompose. When they decompose, the process removes oxygen from the surrounding waters faster than it can be replenished. This creates low-oxygen, or hypoxic, conditions at the bottom of the Bay. Plant and animal life are often unable to survive in this environment, which is why the area is referred to as a “dead zone”.

The main way in which nutrients can enter the Bay is through polluted runoff flowing from its tributaries around the watershed. When our region experiences more—and possibly heavier--rainfall throughout the year, river flows will be higher and faster, increasing the amount of pollution. While the spring of 2021 saw average rainfall and lower river flows, the U.S. Geological Survey (USGS) actually found that the overall average for the water year (October 1, 2020—September 30, 2021) was higher than normal, with flows entering the Bay around 84,880 cubic feet per second. To put that into perspective, an average-sized bathtub holds approximately 5.6 cubic feet of water (42 gallons). That’s the equivalent of 15,118 bathtubs being emptied into the Bay each second."

Read the full article at Chesapeake Bay Program

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