Wednesday, July 6, 2022

Scientists Predict a Better than Average Year for the 'Dead Zone'

 Bay Journal, Chesapeake Bay ‘dead zone’ expected to have another below-average year

Researchers from the Chesapeake Bay Program, University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey have predicted that the Bay’s summertime “dead zone” will be about 13% smaller in 2022 than the average size of the dead zone recorded between 1985 and 2021.

According to the state-federal Chesapeake Bay Program, which leads the restoration effort, this is due to less water entering the Bay from its rivers this spring, as well as a decrease in nutrient pollution from some areas of the Bay’s six-state watershed.

The Bay’s dead zone is a deepwater area with low levels of dissolved oxygen that are hostile to marine life, including fish, blue crabs and oysters. The dead zone is mostly caused by nutrient pollution from human wastewater, animal manure and fertilizer.

Even so, it's not a particularly good year for stripers and blue crabs. Stripers are in a persistent pattern of low recruitment, for causes that are largely unknown, but is thought to be weather/climate related, while crabs have had a couple of bad years of recruitment as well and are facing new harvesting restrictions. Oysters, while above recent years lows, have not rebounded to their historic levels. 

The amount of pollution reaching the Bay each year varies and is based on the amount of rainfall, which flushes nutrients and sediment into rivers that flow into the Bay. The load is also impacted by the number and effectiveness of conservation practices that reduce and manage those pollutants.

The 2021 dead zone was approximately 14% lower than the long-term average.

An assessment of the 2022 dead zone will be available this fall.

13% doesn't strike me as particularly significant. If they told me that the dead zone was half as large as the long term average, I'd be more impressed. On the other hand, I haven't detected the telltale signs of anoxia near our shores so far this year; fish and crabs crowded into the shallow water, pushed up by the anoxic water, which is, in turn, pushed into shallow water by a particular combination of winds.

It certainly does not look like the "Bay Diet" is on track to beat anoxia by 2025 as hoped.

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