The latest survey of underwater grasses, a key indicator of water quality, gives the Chesapeake Bay a mixed bill of health.

Results show that 1998 bay grass acreage in Maryland's portion of the bay declined overall by about 4,419 acres since 1997, a 13 percent decrease. Bay-wide acreage, including Virginia waters, decreased 8 percent.

Noting that bay grasses increased in some Maryland areas and declined in others, Department of Natural Resources Secretary John R. Griffin said in a statement released with the survey, "These findings indicate that there are still many areas that will require further nutrient and sediment pollution reductions in order to make significant progress in restoring our treasured bay and its tributaries."

The grasses are important because they produce oxygen and provide food and habitat for a variety of bay creatures, including crabs, fish and waterfowl. Bay grasses also protect shorelines from erosion and help absorb nutrient pollution and trap sediments that cloud the water.

The most significant increases in bay grasses were in Western Shore tributaries, including the Gunpowder, Magothy, Severn, South and Potomac rivers.

The largest declines were in the middle and lower Eastern Shore from Eastern Bay to the Tangier Sound-Smith Island region. The area has suffered long-term losses -- recording 16,026 acres of underwater grasses in 1992, but losing 13,054 acres since then.