Restoration on the half shell
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By Kirsten Weir
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PHOTO: JENNIFER GREENE |
Last summer, Caroline Wilson, then 7, and her 6-year-old sister Hannah helped to raise some unlikely pets: thousands of baby oysters. Happily for the science-savvy sisters, their grandparents, Lynn and John Badger, had signed on as “oyster conservationists.” The project - a collaboration among the University of New Hampshire (UNH), The Nature Conservancy, and the New Hampshire Estuaries Project - is just one component of an effort to restore eastern oysters to New Hampshire's Great Bay Estuary. “It's a wonderful way to get the community involved in doing something for the bay,” Lynn Badger said.
Besides being a food source for humans and animals, oysters are natural water purifiers. They filter out pollutants from the water of Great Bay, which faces increasing pollutant loads. In 1995, a disease triggered a major oyster die-off in New Hampshire waters, said Ray Grizzle, research professor of zoology at UNH. “We've lost 90 percent of our [oyster] stock in the last 10 years,” he said. He intends to try to bring it back.
The conservationist program started last year with 15 volunteer families, said Jennifer Greene, Grizzle's lab supervisor, who heads up the project. In July, she gave each family a cage full of old oyster shells seeded with as many as 2,000 larvae or spat, each about the size of a pinky fingernail. Every two weeks, the conservationists looked in on their oysters, checked their growth, counted the number of young on five randomly chosen shells, and noted whether oyster drills, mud crabs, or other oyster enemies were present inside the cages. The Wilson sisters and their grandparents were all amazed to see the spat up close, said Lynn Badger. Her husband John agreed. “We hope the project is successful. A thriving oyster population would really help to clean up the bay.”
The eastern oyster (Crassostrea virginica) lives its quiet life in estuarine waters along the Atlantic Coast, from the Gulf of St. Lawrence to the Florida Keys, as well as the Gulf of Mexico. Throughout their range, wild oysters have a history of hard knocks. In the Gulf of Maine, their problems started shortly after European settlers arrived. As the human population increased, oyster numbers plummeted due to sedimentation, water pollution, and extreme overharvesting. In Great Bay, harvesting regulations were imposed as early as 1879, but the shellfish never quite bounced back.
Recently, oysters once again fell on hard times. This time disease is to blame. Two potentially lethal oyster parasites, MSX (Haplosporidium nelsoni) and Dermo (Perkinsus marinus), first began striking the shellfish in the mid-Atlantic some 50 years ago. By 1984, the diseases had worked their way into the Gulf of Maine.
Like the challenges oysters have faced, oyster reef restoration isn't new. It's been going on for some time in the Chesapeake Bay, the area Grizzle described as “the Mecca of oyster research.” In the Gulf of Maine, Grizzle said, efforts to grow oysters have mostly been fisheries-oriented. Aquaculture outfits farm the shellfish in parts of the gulf, and some small-scale “oyster gardening” projects teach citizens how to grow their own oyster crops.
Adult oysters are completely sessile (unable to move), spending their days permanently cemented to one another in a mass known as an oyster reef. Those reefs are crucial to the next generation of oysters. Oysters spawn over a four-to-six week period around August. The resulting spat must anchor themselves to hard, clean surfaces, traditionally an existing oyster reef. But the decline of oysters has led to a lack of suitable reefs for spat to land on. “If you don't have sufficient hard substrate, they don't have anywhere to settle…and they die,” Grizzle said.
Oyster harvesting - even New Hampshire's small recreational-only harvest - removes shells from the already-depleted reefs. “There literally are tons of shells going into landfills,” Grizzle said. “This is not a way to treat a valuable resource.”
To salvage that resource for new reefs, he and Greene launched a shell-recycling program last year. They've invited residents to return empty shells to a drop-off center at Adams Point in Durham. So far, most of the recycled shells have come from oysters harvested from Great Bay, Greene said. She and Grizzle hope to scale up the program and begin collecting shells from seafood markets and restaurants as well.
After a quarantine period to assure the shells are free of disease, Grizzle and Greene use the shells, along with gravel, granite, and other materials, to build new reefs. Since 2000, Grizzle's team has restored four acres (1.6 hectares) of oyster reef in four separate areas of Great Bay. To give their spat a head start, they've seeded the reefs with young oysters bred to have some resistance to disease.
For organisms that usually spend their entire adult life rooted in one spot, Grizzle's oysters are considerably well traveled. Some come from local stocks, others from disease-resistant stocks elsewhere in New England or the mid-Atlantic. Before being placed on their new reefs, many of the baby oysters spend time in other parts of the bay, tethered to the docks of oyster conservationists like the Badgers.
The data collected by the Badgers and other volunteers provided important information about how the oysters fared at different sites around the estuary, Greene said. In October, the researchers collected the surviving oysters, many of which had tripled in size, and placed them on the recycled shell reefs that would become their permanent homes.
This year, Grizzle plans to take a closer look at the oyster reefs to characterize the other organisms that rely on the habitat. “There's no question that these reefs provide habitats for dozens of species,” he said.
He said he hopes restoration efforts will continue to move toward an ecosystem-based approach. Some conservation groups are working toward removing dams, others toward restoring eelgrass or certain species of fish, he noted. He'd like to see them team up and create a grand plan to restore Great Bay estuary overall. “I think it's time for all of the restoration people to take a look at the bigger picture,” Grizzle said. He thinks it's a big dream, but not an impossible one. “There is a movement,” he said. “Let's look at the estuary as a whole and see what we can do.” For more information about the oyster conservationist program or oyster-shell recycling, please visit: http://www.oyster.unh.edu.
Kirsten Weir is a free-lance writer in Saco, Maine, who focuses on science, health, and the environment.
© 2007 The Gulf of Maine Times