Tiny oysters paint the bottom of Tisbury and Edgartown Great Ponds. There has been a huge set of oysters this summer and the future looks bright for a bumper crop to be ready for harvest in three years. And all this is welcome news to a community of shellfish biologists, shellfish constables and water quality experts who have worked for years trying to restore what was historically a prosperous and healthy fishery.

The science now shifts from trying to save the oyster fishery on the Island to also learning about what happened and sustaining it. Whether you are a swimmer standing on the shore, a riparian owner with a home overlooking the pond, or the sailor speeding along the pond in a sailfish — everyone wants more oysters in the great ponds. They are a sign of a healthy pond and they contribute to its health by consuming vast amounts of algae. Oysters are filter feeders. They are the future of the great ponds.

A great set of oysters in the two ponds is welcome news especially to Rick Karney, director of the Martha’s Vineyard Shellfish Group. He has been raising baby oysters, clams and bay scallops for the Island’s ponds for over 30 years. It is also good news to Bill Wilcox, water resource planner for the Martha’s Vineyard Commission, who has been monitoring the water quality of Island ponds going back to 1977. The return of the oysters also brings a shift in the science they’ve been studying on the pond for years.

The two met on Wednesday at the shellfish hatchery on Lagoon Pond to talk about what lies ahead.

“The presence of shellfish in the ponds is our goal,” said Mr. Wilcox. “It is what we are all working for. Our success in improving water quality will be measured by the amount of shellfish production in the pond.”

Mr. Wilcox said for years he has measured the many characteristics of saltwater coastal ponds: salinity, temperature, dissolved oxygen and clarity. But the biggest gauge of healthy water quality is the level of nitrogen in a pond. As nitrogen levels rise, algae blooms. This affects eelgrass beds, the shellfish that live in the ealgrass beds and ultimately other animals. There is a direct correlation between high levels of nitrogen and poor water quality. In recent years steps have been taken to reduce the nitrogen that makes its way into the groundwater, the watershed and ultimately the ponds.

Mr. Wilcox said it is imperative to remain vigilant about measuring the nitrogen entering the ponds; this summer he continued with a sampling program that measures nitrogen levels in the two ponds. And there is evidence that it is dropping.

“The things we are doing in the watershed are going to improve the water quality over a time frame. We have to keep our eye on that ball, even if we don’t see instantaneous results,” Mr. Wilcox said.

The effects of the juvenile oysters themselves on pond water quality won’t be seen at least for another year. Oysters are filter feeders and they consume the phytoplankton that can be harmful. “The amount of water that they filter is directly related to their size. The real small ones filter considerably less than the large ones,” Mr. Wilcox said. “It is going to be interesting beginning next year to see if their extraordinary numbers are going to have an impact, and we’ll be monitoring that.”

Meanwhile, the recovery of oysters in the two great ponds, produces a whole new chapter of science for Mr. Karney and his associates. Mr. Karney said he has never seen so many baby oysters spawned in Tisbury Great Pond in one summer. In the weeks and months ahead, he said he and the shellfish constables and others will be surveying the pond to find the largest concentrations of baby oysters. “There are problem areas in the pond that we want to look at,” Mr. Karney said. For example, he said Deep Bottom Cove has had no oysters for some time, and Mr. Karney said he wants to see if there are any there now. “We seem to have a heavy set of oysters in the tidal areas. A lot of shellfish were stranded when the pond was opened to the sea. Is that where they mostly set? Or are there a lot of oysters in other areas, in deeper water?” he said.

Connecting the large oyster set to the recent spawning programs initiated by the Chilmark and West Tisbury shellfish constables, with floating cages where adult oysters could spawn, will be the next step. Mr. Karney said everyone wants to know to what degree the spawning cages helped. The constables also built up culch on the pond bottom by dropping piles of broken shells, another assist for oysters.

The constables set up aquaculture sites on the pond for juvenile oysters spawned at the hatchery to grow and later be released. Mr. Karney said the remote sites will continue even with the huge set of wild juvenile oysters this summer.

“This is a learning experience for us,” he said.

The frequency of pond openings to the sea and how long they last is another part of the great pond oyster recovery. Both Mr. Karney and Mr. Wilcox said salinity, nitrogen and algae levels can be varied considerably when the pond is opened to the sea.

Emma Green-Beach has been working at the shellfish group hatchery since May of 2006. She is researching oyster diseases and shellfish genetics as she pursues a master’s degree at Rutgers University. She is the shellfish group’s expert on Dermo, an oyster disease that came from southern waters and infected the Island’s great ponds.

Among her colleagues she is jokingly called their “Dermo-tologist.” Ms. Green-Beach has her own theories about this summer’s huge oyster spawn. Dermo is in decline, she noted. The Vineyard’s wild oysters have developed a resistance to the disease and the environmental conditions of the ponds have changed.

But of course there is always the unknown, including this: could Dermo come back with a vengence?

Ms. Green-Beach concurs with Mr. Karney that a hot, dry summer is conducive to the growth and spread of the disease. But Dermo doesn’t like low-salinity water, and she believes the longer and more frequent pond openings to the sea may have helped counter the otherwise prime Dermo weather conditions this year.

In September and October, Ms. Green-Beach will test shellfish for the disease; she said fall is the best time to check. “There should be ongoing monitoring to see how the disease changes over time,” she said, driving home the point that there are so many factors at work: environment, climatic changes, salinity and water temperature.

Ms. Green-Beach said her adviser, David Bushek, with the Haskin Shellfish Research Laboratory in Port Norris, N.J. was delighted to hear about the oyster successes this summer on the Vineyard. She said he has been monitoring the health of oysters in the Delaware and Chesapeake waterways.

Ms. Green-Beach said the prospect of the Vineyard oysters beating back Dermo is better and quite different from the disease battles farther south.

When Dermo hit the Vineyard ponds, all the oysters were affected. That caused the oysters to respond by producing subsequent generations with resistence. In short, we have a more hardy oyster here. “You have to have the constant pressure of the disease to come up with a more resistent oyster,” she said. By contrast, she said, in southern waters there is often crossbreeding between resistent and nonresistent oysters; the end result is more vulnerable offspring.

But when all is said and done about the health of oysters, scientists point to water quality as the key factor and the constant.

“The bottom line, the Vineyard is not the pristine place that we think it is,” said Mr. Karney. “There are a lot of people here. It is August and it doesn’t take much to figure out what is going on. We essentially have an environment that is under a lot of stress from a lot of people,” he added.

“With these oysters, we now have an opportunity. If we have a good fishery and we manage it properly, we can think of sustainability.

“Further, I think we are all concerned now about how effective these animals can be at keeping our water quality up. We want to manage them and maintain enough of them them to buffer the impacts from all these people.”