Bay loses 5,740 acres of grasses

Heavy rains, runoff from poultry farms blamed for '98 drop

30% loss in Tangier Sound

Bottom vegetation provides vital shelter, food for fish, wildlife

May 28, 1999|By Timothy B. Wheeler | Timothy B. Wheeler,SUN STAFF

Underwater grasses, a vital sign of the Chesapeake Bay's health, declined by 8 percent overall last year and by an alarming 30 percent in the Tangier Sound, a critical nursery area for blue crabs.

The 5,740-acre decrease, announced yesterday at a news conference on the Severn River, comes after two years of steady improvement in the extent of bay bottom covered by aquatic grasses.

Federal and state environmental officials blamed the drop-off on a combination of weather and man-made factors, including runoff from poultry farms on the Delmarva Peninsula.

"What we do on our land has a big impact on the health of the bay grasses," said Robert Magnien, director of tidewater assessment for the Maryland Department of Natural Resources.

Grass beds are important to the bay because they shelter fish and crabs, provide food for ducks and geese, and help clean the water by controlling erosion and consuming nutrients. So integral are the 13 species of aquatic vegetation to the bay's vitality that federal and state officials have set a goal of restoring 114,000 acres by the year 2005.

Underwater grasses declined in the 1970s and early '80s, but have been recovering gradually since. With last year's setback, there are 63,495 acres now. That acreage is only a tenth of the nearly 600,000 acres that experts estimate once blanketed the bay's bottom.

Heavier than average rains during the first half of last year clouded the water with sediment and nutrients washed off the land, Magnien said. Some grass beds fared poorly because murky water and nutrient-fed algae blooms blocked out the sunlight they need.

Some bright spots

The annual survey, conducted by analyzing aerial photographs of the bay, had some bright spots. Aquatic vegetation increased by 3 percent in the upper bay, with dramatic gains of 20 percent or more in the Magothy, South and Severn rivers.

Officials gathered at the Sherwood Forest community pier in Anne Arundel County yesterday to highlight the grassy renaissance of the Severn.

Kent Mountford, senior scientist in the U.S. Environmental Protection Agency's bay office, and Peter Bergstrom of the U.S. Fish and Wildlife Service scooped handfuls of horned pondweed and widgeon grass from a bottom that was barren until five years ago. Such grass beds offer important shelter for fish, and the scientists netted dozens of tiny silversides fish and translucent grass shrimp.

But grasses declined by 14 percent in the mid-bay area south from Eastern Bay to the Pocomoke and Rappahannock rivers, and by 5 percent in the Virginia waters of the lower bay.

Most troubling of all was the continued disappearance of underwater vegetation in Tangier Sound, which has lost 63 percent of its grass beds since 1992.

"We're very concerned about the loss of grasses in Tangier Sound, because they comprise 25 percent of the bay's [total] grasses," said William Matuszeski, director of the EPA's Chesapeake Bay restoration efforts. "It's extremely important we get to the bottom of what's happening [there]."

Tangier Sound is a key nursery for juvenile crabs, which seek grass beds for shelter from predators as they grow and mate. Its importance is underscored by the poor commercial crab harvest last year.

Magnien said there is evidence that nutrient pollution could be a factor. Nitrogen and phosphorus from sewage, animal manure and lawn and farm fertilizer are overloading the bay, fueling algae blooms and clouding the water.

Nutrient pollution

While water quality has improved in some bay tributaries on the Western Shore, notably because of sewage treatment plant upgrades, Magnien said nutrient pollution either is worsening or unchanged in some lower Eastern Shore rivers.

Matuszeski produced a map of the Nanticoke River, which drains into Tangier Sound, showing hundreds of chicken houses in the tributary's upper drainage basin. About 40 percent of the watershed lies in Delaware, he noted, which is debating legislation that would require farmers to take steps to reduce poultry manure runoff. Maryland adopted a law two years ago requiring farmers to control nutrient-rich fertilizer and manure runoff.

Farm runoff "can't be ignored" as a possible cause of the Tangier Sound grass decline, agreed Robert Orth, a biologist at the Virginia Institute of Marine Science who compiles the annual acreage estimates. But he suggested there could be other factors as well.

"That's part of the detective story we've got ahead of us," Orth said.

Until scientists understand better why grasses are rebounding in upper bay rivers and declining elsewhere, Orth warned that the restoration goal will be "a real hard target."

Pub Date: 5/28/99

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