For the second year in a row, underwater grasses in the Chesapeake Bay are showing signs of recovery after enormous losses in 1998.

Officials still don't know what caused the great losses of the grasses two and half years ago and they say the problems are far from over. According to a recent report, overall acreage of the submerged grasses crept up just 1 percent in 2000 to about 69,000 acres and they remain at little more than 10 percent of their historic levels of about 600,000 acres.

Some scientists blame a persistent algae bloom that afflicted the middle Bay last year for the losses in those areas. Pollution and sediment are also big obstacles to the growth of lush bay grass beds.

The year for bay grasses in Maryland was mixed, says Bill Street of the Chesapeake Bay Foundation.

"We had some very nice gains in the upper Bay where we had some grass beds that looked as healthy as we have seen them in many years," he says. In the middle Bay, however, "we had quite a lot of algae and that algae blocks the sunlight for the grasses and the grasses are not able to grow as much, so we had very steep declines in some of the rivers in the middle Bay."

For example, the Severn River lost 70 percent of its grasses, but in areas of the lower Bay such as Tangier Sound, grasses increased.

Why do bay grasses matter?

"Bay grasses really are the single best indicator of the health of the Bay because they rely on water clarity and water quality to get the sunlight that they need to grow," says Street.

"They really are a reflection of how well we're doing cleaning up the water quality in the Bay." Grasses are also important for animals and fish that inhabit the Bay, such as blue crabs and trout.

Bay grasses aren't really grasses. Scientists call them submerged aquatic vegetation. The plants are rooted on the bottom and grow completely underwater, making them "totally at the mercy of water clarity to get that sunlight." The Chesapeake Bay is home to a dozen species of bay grasses.

The importance of bay grasses did not escape the attention of the Chesapeake 2000 agreement signed last year. Under the agreement, Maryland, Virginia, the District of Columbia and Pennsylvania have all promised to work together to increase acreage throughout the watershed.

The so-called "C2K" document "really set some strong goals for us to remove the limitations for the Bay for growing grasses," such as significant reductions in the nutrients and sediments that flow into the Chesapeake Bay, Street says.

The Chesapeake Bay Foundation estimates that it could cost $8.5 billion to reach the goals.

"We think that the benefits that would come from that would far surpass that number," says Street. "We think it would be a good investment, and really is something that we need to do to bring the Bay back to what it should be."

Part of the agreement focuses on restoring vegetation around the shore of the Bay. "That's a very important component to restore the natural filters, the wetlands and the forests along our streams and rivers to filter out the sediments and the nutrients before they are able to get to the Bay."

The foundation and the Maryland Department of Natural Resources sponsor programs in which students plant bay grasses. In addition to learning about why the grasses are so important to the health of the Bay, the efforts can help in restoration.

For example, the South River lost almost all its grasses last year. Plantings by citizens and students have led to the comeback of Redhead Grass there for the first time in 35 years. "That's really providing the plant material that hopefully will spread to other other creeks on that river."

Such plantings "really can play an important role, but certainly water quality is the most important factor."