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New York

James Cervino, a professor of marine biology at Pace University in New York City, thinks a little electricity could go a long way in helping oysters return to the city’s waterways.

On a recent morning in College Point, Queens, just a few blocks from where he grew up, Professor Cervino shows a visitor what he calls “the electric oyster reef project.” He’s installed a series of spiral-shaped bands of metal in the shallow water. At low tide, they jut from the water like giant strands of DNA.

“I had a dream one night of helixes coming out of the water,” he says. In retrospect, the shape “is actually not such a great idea.” But the concept, he says, is.

Solar panels perched atop poles provide the helixes with a low voltage. The current causes a chemical reaction in seawater, and limestone builds up on the electrified metal. The ready supply of shell-building minerals, Cervino says, will help the oysters, decimated here and elsewhere by overharvesting, pollution, and disease. Cervino’s collaborator, Thomas Goreau, president of the Global Coral Reef Alliance, has shown that electrification can help damaged coral reefs regenerate. It seems to be helping the oysters here as well, he says. Oysters in mesh sacks at the spirals’ base are alive while control oysters – those farther from the electric field – have all died.

He points to a lime-encrusted bit of metal: “That’s how I know it’s working,” he says. And then he adds, “If we recreated oyster reefs, we’d clear the water.”

This project is part of a larger movement along the East Coast and elsewhere to restore ecosystems drastically altered by human activity. Restoration almost invariably begins with so-called keystone species, the humble filter feeders once so numerous along the eastern seaboard that they cleaned entire bays within days.

Don Boesch, president of the Univer­sity of Maryland Center for Environ­­mental Science in Cam­bridge, Md., calls oysters “the coral reefs of the East Coast.” Oyster-restoration projects are at various stages in Florida, South Carolina, Chesapeake Bay, New York, and New Jersey. Before European settlement, oyster reefs covered some 350 square miles around New York. Their importance as a species stems from their ability to filter large amounts of water. Depending on its size, an oyster filters between 5 and 50 gallons of water daily. Water now murky with algae and other organic matter was, in earlier times, almost certainly clear.

“I suppose that when [Henry] Hudson sailed through the harbor, you could see right through to the bottom,” says Mark Kurlansky, author of “The Big Oyster: History on the Half Shell,” the tale of New York City’s long relationship with the mollusks. Their absence, he says, is “a symbol of how badly we’ve cared for New York.”

By the 1930s, oysters were deemed too dangerous to eat in New York. A few decades later, they were ecologically extinct from the city’s waterways. Thanks to the Clean Water Act, conditions have improved a lot since the 1970s when, as Mr. Kurlansky recalls, the water was black “with this sort of mother-of-pearl purplish green thing on the surface.” Says Cervino, “I’ll go swimming in this.” As an adolescent, he’d studiously avoided it.
Any restoration effort faces some serious obstacles.

“Once you mess around with nature – if you remove something from the food chain – that space isn’t reserved for it to come back,” says Mr. Kurlansky. “It’s very difficult to reverse these things because the absence has had all sorts of repercussions in nature.”

He points to cod’s nonrecovery after lengthy closures of Georges Bank and Canada’s Grand Banks to cod fishermen. “To have a drastic moratorium like that and have nothing come back is pretty scary,” he says.

Oysters need hard surfaces to attach to and access to minerals to form their shells, for example. When reefs are abundant, the shells of previous oyster generations serve as both a hard substrate and mineral source. Reefs self-perpetuate. But when oysters disappear, their habitat goes as well. With oysters gone, the area becomes less oyster-friendly.

In relatively enclosed waterways like Chesapeake Bay, high nutrient runoff from fertilizer and livestock, combined with the loss of filter feeders has led to more extensive algal blooms. That leads to low-oxygen conditions that, in turn, suffocate what bottom-dwelling filter-feeders remain, further exacerbating the problem.

In the 1950s, Asian oysters brought to the Eastern Seaboard for aquaculture also carried two parasites that American oysters had little resistance to. Native oysters succumbed easily. The bacteria linked to cholera in humans also exacted a toll. The  hurdles facing oyster restoration quickly began to look insurmountable. The abiding question: How can you tip the ecosystem back to a more oyster-friendly state?

Chesapeake Bay is a case study. It was once home to what were probably the largest oyster reefs in the United States, yielding around 15 million bushels of oysters a year in the late 19th century. The oysters used to filter the entire bay every three to four days. Even 20 years ago the bay still produced a couple million bushels a year. Then the diseases arrived. By last year, the harvest had dropped to 100,000 bushels. The oysters that remain now manage to filter the bay three to four times a year. And the ecosystem has changed. Sunlight can’t penetrate the now-murky water. Plants can no longer grow on the bottom. During the summer, large areas become oxygen-starved (hypoxic), hostile to animal life.

“The degree that the oyster as a living part of the ecosystem, as a filter feeder, was able to keep the bay clear of nutrients is a very important function,” says William Eichbaum, chair of the Maryland Oyster Advisory Commission in Washington, D.C. “And it’s gone.”

Intensive restoration efforts have so far failed to reestablish breeding oyster populations. And yet, Mr. Eichbaum and others think such efforts may be at a turning point. Oyster harvesters simply can’t live off what’s left. Many are moving to aquaculture. That’s good news for the bay’s beleaguered oysters, he says. Able to reproduce without pressure from the harvest, oysters will have a chance to rebuild habitat – to form structures that, by rising above the seafloor, help them avoid low-oxygen conditions and silt. With healthier reefs, oysters will have a chance to develop a resistance to the exotic parasites, says the University of Maryland’s Professor Boesch. “They’re going to have to confront the disease,” he says.

Cervino hopes to help the oysters in New York in a slightly different manner. He’s not sure how the electrified metal helps oysters fight off disease, but he suspects that by making their lives easier with a mineral-rich substrate, their ability to resist disease is strengthened.

“I’m a bottom-up guy,” Cervino says. Then he recites his mantra, taken from the 1989 movie “Field of Dreams”: “If you build it, they will come.”

In other words, bring the marsh grasses, the hard surfaces, and the minerals back, and the oysters and mussels will return. The horseshoe crabs, blue crabs, and fish will follow. People will ultimately benefit. The whole living system, shellfish included, will provide an alternative to bulkheads and other human antierosion measures that the shellfish can provide naturally.

“The only barrier to protect against erosion is wildlife – habitat,” he says.

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