Nearly 50,000 acres of the Bay’s bottom — an area slightly larger than Washington, D.C. — may eventually be permanently zoned as a safe harbor for oysters.

Setting aside 10 percent of the Chesapeake’s historic oyster beds as permanent sanctuaries was one of the key areas of agreement reached among scientists, managers, watermen and environmentalists from Maryland and Virginia during a recent workshop.

Ultimately, the sanctuaries would become the focus of oyster restoration efforts in the Bay, where reefs would be built, and oysters would be allowed to grow old, large and — hopefully — disease tolerant. As they reproduce, those protected oysters would form the base of the Bay’s future oyster population and support a growing harvest in areas outside the sanctuaries.

An agreement document stemming from a two-day January workshop lays out the path states will follow to achieve the tenfold oyster increase called for in the draft Chesapeake 2000 Bay Agreement.

“We’ve certainly moved forward on how we are going to implement this tenfold goal, and the consensus is that sanctuaries will be one of the most important ways,” said James Wesson, who heads oyster restoration projects for the Virginia Marine Resources Commission. “That’s a pretty important statement.”

The agreement — expected to be backed by millions of dollars of increased state and federal spending — is the latest sign of growing optimism that the beleaguered oyster, whose population is near an all-time low because of decades of overharvesting and disease, can make a comeback in the Chesapeake.

Restoring a healthy oyster population is increasingly seen as a critical element of the Bay’s recovery. The Chesapeake was once filled with oyster bars rising far above the bottom and sometimes breaking the surface of the water.

The reefs support not only oysters but provide habitat for a variety of fish and the food they prey upon. Over the years, the reefs were knocked down, the oysters overharvested and — in recent decades — diseases piled on, driving the oyster population to only about 1 percent of its historic level.

Now, scientists and managers see efforts to bring back the oyster as a way to not only revive a fishery, but to enlist a new partner in Bay restoration. Oysters are powerful water filterers, which could help the states meet water quality goals. Historically, cleanup efforts have focused only on curbing runoff and reducing discharges into the water.

“We need to enhance our biological communities and habitat in the Bay because they can also contribute in our efforts to clean up the Bay,” said Frank Dawson, of the Maryland Department of Natural Resour ces, who chairs the Bay Program’s Living Resources Committee. “That is why there is an emphasis on the ecological function of oysters.”

The Chesapeake 2000 Agreement, expected to be signed in June by the Chesapeake Executive Council — the governors of Maryland, Virginia, Penn sylvania; the EPA administrator; the mayor of the District of Columbia; and the chairman of the Chesapeake Bay Commission, representing state legislatures — also calls for new water quality goals based on water clarity. Clearer water would help restore underwater grasses and other important resources.

Steve Jordan, director of the state-federal Sarbanes Cooperative Oxford Laboratory in Maryland, said a tenfold increase in oysters could filter a “significant” amount of water. That would be about the number of oysters that existed in the Bay during the early 1980s, he said. Back then, Jordan estimated the oyster population was able to filter about 11 percent of the summer algae production. “They definitely would provide some benefits in terms of water clarity,” he said.

Scientists estimate that oysters were once able to filter all of the water in the Chesapeake, removing water-clouding sediment and algae, in a matter of days. It takes today’s depleted population about a year to do the same job.

For years, efforts to restore oysters have been stymied by two diseases, MSX and dermo. Although harmless to humans, they can kill huge numbers of oysters before they grow old enough to reproduce.

The new oyster restoration agreement seeks to outpace disease mortality by focusing on habitat improvements that improve reproduction and survival. “We can’t do anything about disease,” said Mark Luckenbach, a researcher with the Virginia Institute of Marine Science. “But we can do something about creating habitat, and we can do something about managing harvest.”

To that end, the agreement largely adopts a strategy laid out last year in a first-ever consensus among oyster scientists from universities in Virginia, Maryland and North Carolina. But the new agreement is significant because it broadens that consensus beyond scientists by getting others — most importantly managers from both states — to agree.

“The thing that has really amazed me is that everyone has embraced this,” said Gene Burreson, research director at VIMS, and the organizer of last year’s scientific consensus meeting. “The public is behind it, the scientists are behind it, the managers — everyone is sort of going down the same path and thinks it is doable and has got this gung ho attitude — let’s go out and get it done.”

With the new agreement, the oyster restoration strategy is about to go from academic exercise to full-scale implementation.

States were already stepping up activity. Virginia and Maryland have each spent about $1 million annually on oyster restoration projects, but Maryland Gov. Parris Glendening has pledged to increase that to $25 million over 10 years.

For its part, Virginia last year launched a partnership between the Virginia Marine Resources Commission, the Department of Environmental Quality and private groups to step up reef restoration efforts, starting in the Rappahannock River. Federal agencies spent nearly $4 million on oyster restoration efforts in the Bay last year as well.

With the new agreement in hand, the Chesapeake Bay Foundation has called on Congress to commit an additional $50 million to oyster restoration over the next 10 years. That amount, combined with existing efforts, would be enough to restore more than 200 reefs and rehabilitate surrounding harvest areas, according to the CBF. Congressional aides have indicated that legislation to increase spending was expected.

Bill Goldsborough, CBF senior scientist, argued that — dollar for dollar — oyster restoration may be the best investment in the Bay because it combines habitat, water quality and fishery benefits. “I really think that $10 million a year Baywide for oyster restoration, even counted above and beyond current spending, can be viewed as relatively modest compared to some other things,” he said. “I think you could justify a lot more than this.”

The agreement envisions a series of sanctuaries that stretch up each major river, covering a range of salinities. Because oyster spawning is unpredictable, the hope is that having oysters exposed to variety of different conditions will increase the odds each year that some areas will have good reproduction.

Reefs would be built in the sanctuaries and stocked with large oysters bought back from watermen and with oysters obtained from hatcheries or “oyster gardeners” who rear oysters in rivers.

Then, the sites would be left alone.

In the past, oysters were harvested when they reached market size. Under the new plan, scientists say, older oysters — which have shown some ability to withstand disease — will be protected and allowed to reproduce in the hope that they will pass on disease-resistant traits to their offspring.

And because larger oysters are more productive that smaller ones, they should be able to produce even more young. Wesson called the sanctuaries “spawning factories.”

“The bigger they are, the more they spawn so they become a bigger part of the gene pool,” he said. “So you not only get more oysters, but you also get oysters with a better genetic strength for fighting disease. It’s so simple in the biological principles that are involved, you think you ought to be doing something more innovative.”

Areas outside the sanctuaries would be covered with thin layers of shells, rather than high reefs, to provide oyster larvae, or “spat” with something solid to latch onto, or “set.” Those surrounding areas would be open for harvest.

Theoretically, the strategy would replace the need to continually “plant” areas with young oysters for harvest; in Virginia, reefs have shown they can increase spat sets for miles.

Part of the long-term goal is to restore not only oysters, but also a sustainable fishery. Oysters were once the most valuable fishery in the Bay.

The plan is largely based on a model that has proved successful in Virginia in recent years. The Virginia reefs, stocked with large, old oysters, have shown good reproduction and signs of disease tolerance.

Reefs are considered important because they clump oysters together. Oysters reproduce by releasing eggs and sperm into the water, in the hope that they will mix; grouping oysters together helps to improve the odds of the eggs being fertilized.

But rebuilding habitat will be slow because it is costly, and the amount of oyster shell available for reef construction and covering harvest areas is limited.

Maryland and Virginia have already set aside 27,000 acres of sanctuaries, but only about 200 acres of habitat has been restored in those areas. Goldsborough said that even the stepped-up program would be doing good if it were able to construct 1,000 acres of reefs over the next decade.

Even without reefs to jump-start oyster restoration efforts, officials say the safe haven provided by sanctuaries should be beneficial. “We think they spawn better and they survive better on these three-dimensional structures,” Wesson said. “But at the same time, we see that if they are ideally located, sanctuaries alone are very, very valuable and the oysters will start rebuilding on their own.”

There is no timetable for when the 10 percent sanctuary goal, which had been recommended by the scientific panel, will be met. Based on historical estimates of oyster habitat, the 10 percent goal should work out to about 50,000 acres of sanctuary Baywide, Goldsborough said.

Although scientists express optimism that the restoration strategy will work in the long run, they caution that the speed of recovery rests more in Mother Nature’s hands than in management.

The severity of disease infestations, which can knock back the populations, is largely influenced by nature: dry, high-salinity years like 1999 lead to increased disease and mortality. And while scientists believe oysters can become tolerant to disease, they don’t expect them to become altogether immune. Also, the success of oyster reproduction from year to year depends on a host of natural variables, not all of which are understood. A series of poor spat sets, coupled with high disease, could set efforts back

Also, the methods that proved successful in Virginia may be less straightforward in Maryland, some caution. Because the Bay is less salty in Maryland, its oysters usually have less disease pressure. That means oysters with little disease resistance may survive longer — only to be wiped out in high-salinity years. Over time, oysters with more disease resistance could still be produced, scientists say, but it may take longer than Virginia. Another problem in Maryland is that its lower salinities often contribute to lower spat sets.

And unlike Virginia, where there is little harvest, Maryland still has a fishery that produces about 400,000 bushels of oysters a year. That will make the job of allocating areas between sanctuaries and harvesting more difficult. Good spat sets vary from place to place, and from year to year, and harvest activity moves to where the oysters are. When habitat is restored, there is no guarantee that is where the spat will set.

Still, said Jordan, of the Oxford lab, the sanctuaries may represent the best long-term strategy for oysters. “One thing that can beat disease to a certain extent is recruitment. We can’t have strong recruitment unless we have good habitat. If we really want to restore oysters to the Bay, we’re going to have to take a gamble, and I think this particularly applies to Maryland. We’re going to have to establish some substantial areas of good habitat, and we’re going to have to hope that we get a strong spat set in those areas. That’s probably the only way we’re going to be able to accomplish this [tenfold] goal.”

Whether that gamble pays off, he and others acknowledge, may not be known for years because so many natural variables influence oyster survival and reproduction. The biggest threat to the strategy, scientists say, may not be the whims of nature, but the impatience of humans. They worry that support will wane over the years, particularly if there is a series of bad disease years.

“We are going to have disease setbacks along the way when we have really dry years like this,” Burreson said. “But that shouldn’t suggest that the strategy is not valid and that we should give up and concede to the diseases. I don’t favor that at all. It’s just a question of holding a steady path and just keep moving forward.”