"Dead Zone" Projected to Shrink, Again

UMCES, Smaller Chesapeake Bay Dead Zone Forecast for Second Year in a  Row. Make that five in a row, and I'll start to believe it's a real trend.

Researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey are forecasting, for the second year in a row, a smaller than average “dead zone” due to reduced river flows entering the Chesapeake Bay, as well as less nutrient and sediment pollution thanks to the management actions taken across the watershed to improve water quality.

"This year's forecast suggests a smaller dead zone than is typical because the river flows that carry nutrients to the Bay were slightly lower than normal. But the amount of nutrients carried to the Bay by a given amount of flow has lessened over time due to effective nutrient management in the watershed. This is an example of a positive trajectory for the Bay,” said Jeremy Testa, Associate Professor, University of Maryland Center for Environmental Science Associate Professor.

Hypoxic and anoxic regions, which are areas of low and no oxygen, respectively, are caused by excess nutrient pollution flowing into the Bay. Compared to the last 35 years, this year’s Chesapeake Bay hypoxic volume, or “dead zone”, is predicted to be 14% lower than average, while the volume of water with no oxygen is predicted to be 18% lower than average. In 2020, the Virginia Institute of Marine Science reported the dead zone to be smaller than 80% of those monitored since 1985.

As usual, what it's really about is the weather. Relatively dry years are good for the "dead zone" and bad for Sea Nettles. But they're going claim credit anyway. 

I do believe the achieved nutrient reductions ("Bay Diet")have slightly reduced the propensity of the Bay to produce hypoxia in summer, but the Bay does have the ideal physical setup to produce it. A large body of water, with deep areas out of reach of easy wind mixing, and substantial freshwater inputs that create a density barrier to further mixing, and a substantial amount of organic material input which fuels the algal blooms and the respiration that  remove oxygen from the bottom waters. I don't think it's likely we'll ever get to a point where there is no "dead zone."