River Project Offers New Hope for Oysters, Researchers Say
Friday, July 31, 2009
Scientists say they've created something in a Virginia river that hasn't been seen since the late 1800s: a vast, thriving reef of American oysters, the shellfish that helped create the Chesapeake Bay's ecosystem and then nearly vanished from it.
The reef sits on the bottom of the Great Wicomico River, a bay tributary about 80 miles southeast of Washington. The scientists say they found a better way to plant oysters, creating an 87-acre colony of bivalves that teems with other marine life.
That's a long way from bringing oysters back in all of the Chesapeake. Virginia and Maryland officials said this week that they doubted this success could be replicated widely.
But the oyster researchers said their work, published online Thursday in the journal Science, provides new hope for one of the bay's most beleaguered species. The oyster, depleted by overfishing, pollution and disease, has fallen to less than 1 percent of its historical population.
When an underwater camera hovered over the new reef, "we knew we were looking at something that no one had ever seen before" -- or at least, no one living -- said David Schulte, a researcher with the U.S. Army Corps of Engineers who worked on the project.
They saw small fish, blue crabs and oysters blowing out underwater "smoke rings," showing that they were filtering out algae and dirt. "That just had been something that hadn't been in the bay for more than a century," Schulte said.
For centuries, the bay and the bivalve were as tightly linked as a forest and its trees. Oysters filtered the water as they fed, and they clustered in reefs that were as busy with life as Caribbean corals.
But, after Europeans arrived, these reefs were destroyed by centuries of watermen towing rakelike metal "dredges" and silted over by dirt flowing from the mid-Atlantic's farms and growing cities. The final blow came in the mid-20th century: A pair of new diseases killed oysters by the millions.
Now, in many places, the bay bottom is a flat expanse of green mud.
"Just picture, you know, a clear-cut forest," said Kennedy Paynter, a biology professor at the University of Maryland who did not work on the Great Wicomico project. "I mean, we're down to one or two oysters per square meter [of bay floor], when we suspect it was 200 or 300 at least back in the day."
For years, efforts to save the oyster, and the Chesapeake watermen who caught them, came to little. Federal and state governments spent $58 million from 1994 to last year and wound up with fewer of both. They considered bringing in a new oyster species from Asia but shelved that idea this year.
In the Great Wicomico River, the researchers said they used a new strategy. They closed the area to harvesting, then in 2004 piled old oyster shells one to two feet high -- higher than previous researchers had, they said. They waited for baby oysters to latch on. The idea was to give the oysters a perch out of the dirt-choked water on the bottom.