Chesapeake Bay’s dead zone expected to be smaller than usual

Chesapeake Bay is on track for a smaller than usual dead zone this summer because a smaller flow of water into it is bringing fewer pollutants.

This year’s dead zone is forecast to be 13% smaller than the average seen from 1985 on and is likely to be roughly the same size as last year’s, researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey reported.

The flow of water into the Bay this spring was down 5% from the long-term average.

One key factor for the forecast of a smaller than average dead zone is a 22% decline in the volume of a key algae-feeding pollutant, the researchers said.

Fish, crabs and oysters can’t survive in dead zones — the term for areas of low oxygen caused by algae blooms. The bay’s fisheries employ thousands of watermen and hundreds of seafood processing plant workers, mainly on the Peninsula.

For the past three years, the dead zone has been forecasted to be lower than the long-term average. The forecasts proved to be accurate. This year’s dead zones emerged later than in the past four years, which they were first reported in mid to late May.

This year’s first low oxygen — hypoxia in the scientists’ jargon — areas weren’t reported until early June. A cooler than usual May was the main reason.

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Runoff of nitrogen and phosphorus, common ingredients in fertilizers used in suburbs and on farms, feeds dead zones, while weather conditions also affect size and duration.

Heavy rainfall can carry more pollutants to the Bay, while hot summer temperatures and weak winds help the dead zone grow.

“The fact that hypoxia in the Bay is once again forecasted to be lower than the long-term average is clearly a positive sign for Bay restoration,” said Marjy Friedrichs, a research professor at Virginia Institute of Marine Science.

But while the Bay is headed in the right direction, large portions still will not have enough oxygen for a healthy ecosystem, said Beth McGee, director of science and agriculture policy at the Chesapeake Bay Foundation.

She said farmers need financial and technical help in their efforts to reduce runoff.

”At the same time, EPA must hold the states, especially Pennsylvania, accountable to meet pollution reduction requirements from all sources,” she said. “Without those state and federal efforts, the Chesapeake Clean Water Blueprint will be yet another in the history of failed Bay restoration efforts.”

Dave Ress, 757-247-4535, dress@dailypress.com