Study predicts slight gains in health of bay


Chesapeake Bay grasses could rebound slightly this summer, and dead zones are likely to cover less of the bay than they did last year, according to predictions released yesterday by the federal-state Chesapeake Bay Program.

The news isn't all good for the second year that the Annapolis-based program has tried to forecast conditions. This summer is expected to be an average one, but for the scientists trying to improve the bay, average isn't something to celebrate.

"The good news is, it's not going to be as bad as it was last year. But the bad news is, that's not good enough," said Bill Dennison, a biologist with the University of Maryland Center for Environmental Science, one of several researchers who conducted the study.

The outlook for grasses is perhaps the best news the report offered. Dennison and the other researchers are predicting slight increases in the density of grass beds in the northern bay and in the lower Potomac.

Bay grasses provide crucial habitat for crabs, fish and other bay creatures. Their presence in the bay indicates a healthy ecosystem. This spring, researchers were dismayed to find a die-off of grasses in the Tangier Sound due in part to warmer water temperatures; Dennison and his crew are predicting that some of those destroyed plants will come back this year as researchers re-seed the area.

"We're creeping back up, but we're far from our overall goal with grasses," Dennison said. "We're less than halfway there."

Last year, bay program scientists predicted the worst season for Chesapeake Bay dead zones in seven years, and that forecast was largely accurate. Heavy rain washed a significant amount of fertilizer and other pollutants into the bay and its tributaries, creating large swaths of water where the oxygen was too scarce to support marine life.

When an area becomes a dead zone, some of the larger organisms, including striped bass, can swim away. But the low-oxygen, or anoxic, conditions suffocate smaller creatures before they can escape.

The worst year for areas with near zero oxygen water was 1993, when 4.8 percent of the bay's main stem had less than 0.2 milligrams of dissolved oxygen per liter of water. This year, researchers are predicting that about half of that - 2.3 percent of the bay's deep-water main stem - will be anoxic.

If the weather stays dry, the Potomac River could get a reprieve from some of the harmful algae that researchers predict is on the way. The blue-green algae, which cover the water surface like a thick carpet and block light needed for photosynthesis, could coat parts of the Potomac as early as this month.

Peter Tango, chief of quantitative ecological assessment for the Maryland Department of Natural Resources' resource assessment service, said that at worst the bloom might cover 20 miles of river surface.

"The drier the conditions get, the less we'll see," Tango said.

For a program that has worked for 20 years to improve conditions in the bay, yesterday's news was only slightly encouraging. Though there were no dire predictions, the forecast underscored the need to reduce pollution from agricultural sources, power plants, wastewater treatment plants and impervious surfaces.

"We're trying on all fronts to make some progress," Dennison said. "We really need to redouble our efforts."

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