Can the oyster really save our rivers and bays?
The tiny crab is fast, skittering just out of reach, headed for cover in a pile of oysters. But Ray Grizzle is faster. “Ha!” He plucks the critter, about the size of a nickel, from the pile of shells and holds it between his thumb and index finger, squinting against the brilliant September sunshine. “See this? He’s one of the main culprits. These guys love baby oysters.”
The UNH research professor of zoology has just cut the motor on his 18-foot skiff, and the only sound is the gentle slap of waves against the hull. Heaped in the bow is a mess of muddy shells, each one host to several baby oysters, or spat, that have grown big enough to survive in the wild against crabs and other predators. Grizzle goes back to work, scooping “spat on shell” into the water. Scoop and scatter, scoop and scatter. Each toss carries with it a little more hope for the future of New Hampshire’s Great Bay.
For centuries, the Eastern oyster (Crassostrea virginica) thrived in these waters. The tides that roll in and out of this 10,000-acre estuary churn up a rich mix of sea and fresh water that supports 162 bird, fish and plant species, plus countless invertebrates, including the finicky oyster, which demands a complex balance of temperatures, tides and salt content. Prized by aficionados who pay handsome sums to slurp the tender meat raw from the half shell, oysters are loaded with zinc and other nutrients. Oyster lovers, though, tend to wax poetic about taste, not nutrition. They use words like “briny and bracing,” “salty and buttery,” “crunchy and slightly nutty.” They say an oyster is a taste of the ocean itself.
But oysters have an alter ego when it comes to their estuarine habitat. This humble mollusk, easily cupped in the palm of one hand, is, in fact, something of a superhero. Building craggy piles of shells as they multiply, oysters provide a rich habitat for fish and other estuary life, and slow shoreline erosion. Best of all, because a single oyster filters up to 40 gallons of water a day simply by dining on plankton, oyster reefs create massive natural filtration systems. “They function like kidneys for the bay,” says Grizzle.
That is, they used to. Over the past two decades, pollution from septic systems, fertilized lawns and pavement runoff has spiked, along with discharge from wastewater treatment plants, gradually suffocating the oysters. Then, in the mid-1990s, disaster struck. Parasites wiped out 90 percent of the remaining population. By 2000, the reefs, which had once covered a thousand acres in Great Bay, had dwindled to a mere 50. “We were verging on local extinction of a species,” says Grizzle. And Great Bay wasn’t the only place in trouble. Along much of the East Coast, where massive oyster reefs once posed navigational hazards to ships, populations had plunged—and so had the water quality. In Great Bay, oysters used to cycle the water every few days—now the process takes nearly a year.
Hoping to arrest an environmental catastrophe, Grizzle and his team spent five years experimenting with small restoration efforts as they searched for a disease-resistant strain of oysters. “We had little pockets of success,” says Grizzle. But it was slow going. Then in 2006, record rainfall flooded the bay with fresh water, and the oyster larvae population exploded—thanks in part to dramatically lower salt levels, which wiped out the infamous crabs. It was a turning point for Grizzle. “I realized that there were more oyster larvae in the water than we thought,” he says. But it was a missed opportunity. Choking in silt, Great Bay no longer had much oyster-friendly real estate. Any hope of restoration, he realized, would require a transformation of the geography itself.
While mollusk reproduction will never spark much water-cooler gossip, the sex life of the oyster does have its own intrigue. Some, like European oysters, are hermaphrodites, containing both eggs and sperm. Others, like Eastern oysters, begin life as males and then change to females. Triggered by warming temperatures, eggs and sperm are released into the water, and, should they happen to cross paths, become larvae. At this point, the race is on. The larvae have about 14 days to find their way to a hard surface—ideally a pile of oysters, but they’ll take anything they can get, including docks and piers and old beer bottles. Wherever they land, oysters excrete a unique calcium-carbonate adhesive and latch on for life.
“Check this out.” Ray Konisky ’03G, who works closely with Grizzle and is sometimes referred to as “the other Ray,” is kneeling in the mud near the mouth of the Oyster River. A marine ecologist with the Nature Conservancy, he pulls back a damp clump of rockweed. Underneath, stuck to a small rock, is an oyster—one lone mollusk. “There used to be huge reefs at the mouths of these rivers—now all we’ve got is mud,” says Konisky. “The rivers were like nutrient pumps from the towns, and oysters settled right in.”
To a point, Konisky explains, nutrients are beneficial for oysters. “In the past, there was enough natural flushing, with tides going in and out, to handle any excess.” Now there’s too much—especially nitrogen, which has risen 42 percent just in the past five years. Algae blooms, including a large alga known as sea lettuce, can spread in thick green mats, making it hard for anything else, including oysters, to survive. It’s a vicious cycle: Just when the bay needs its natural water treatment system more than ever, oysters are suffocating in sea lettuce and silt.
The two Rays are out to change that. Konisky scans the horizon, pointing to a dark speck. It’s a barge heading for the mouth of the Oyster River with 30 tons of clamshells—part of a reef-building experiment designed to transform one acre of muddy river bottom into a healthy oyster breeding ground. Konisky, who secured federal and state funds for the project (matched by the Nature Conservancy), has spent months orchestrating the details.
It began at Blount’s Seafood in Rhode Island, where clamshells leftover from making chowder were loaded into 18-wheelers and, instead of heading for a landfill, were trucked to UNH’s Kingman Farm. “Oyster shells are the ideal substrate,” says Grizzle, “but there just aren’t enough of them. Clams are a good alternative.” For six months, the shells baked in the sun, wiping out any foreign organisms. Then they were loaded into giant feedbags and hauled to the barge.
Now deckhands latch a cable dangling from the barge’s giant crane to a one-ton bag. Minutes later, shells cascade into the water below. In three days, 100 tons of shells, the foundation of a new reef, will be ready and waiting for oysters in search of a home.
Oysters aren’t much to look at, especially early on. The larvae Grizzle uses to seed his reef experiments, from a hatchery in Maine, would be easy to mistake for a small pile of sand. In the spring, when the larvae arrive, research technician Krystin Ward ’06 tosses one handful—roughly two million oysters—into each of two big gray tanks out behind UNH’s Jackson Lab on the edge of Great Bay. Then she waits. In a few days, the larvae have attached to the old oyster shells at the bottom and grown into spat, which look like brown smudges about the size of a pinky fingernail. Next stop: the “nursery raft,” anchored just offshore. Consisting of 160 cages lashed together in a sort of high-density oyster condo, the raft provides a relatively safe haven where the vulnerable spat spend the summer. Each cage holds about 200 shells, which serve as hosts to approximately 2,000 spat. During their weeks on the raft, Ward nurses the baby mollusks with regular cleanings, removing seaweed and other debris to improve water circulation through the cages.
Meanwhile, around the bay, about two dozen citizen-scientists are babysitting their own batches of spat-on-shell. Husband-and-wife team Jere Lundholm ’53 and Harriet Forkey ’54, ’67G love telling their friends that they spend the summer as foster parents—to about 500 baby oysters. Every other week, they go to the end of their dock and haul up a small wire cage. Along with removing plants and barnacles, Lundholm and Forkey take measurements and record their findings, which they hand over to Ward when she collects the cages in the fall.
Oysters raised by local residents like Lundholm and Forkey get so much attention that they grow extra big and healthy—which means they have a better chance of survival in the wild. Citizen-scientists also provide critical data, helping researchers compare growing conditions around the bay and determine where to locate the next reefs. In the past decade, Grizzle has worked on about a dozen restoration projects amounting to roughly 10 acres. Not all of them have been successful. Looking ahead to the next decade, the goal is to add two additional acres a year. The numbers may seem small, but the UNH-Nature Conservancy collaboration that has developed in recent years—combining scientific research, funding sources and logistics expertise—has generated new momentum. Successful “spawner sanctuaries,” which are off-limits to harvesting, could be the ecological sparkplugs that someday ignite a wild oyster revival. The hope is that oyster farming, too—the raising of oysters for consumption—will become a viable enterprise in the bay. For now, though, the focus is on oysters as defenders of the ecosystem.
Success can’t come soon enough. A recent study reported that globally, 85 percent of oyster reefs have been lost. Restoration efforts are underway around the world, and in nearly every state on both U.S. coasts. In New York harbor, for example, the New Hampshire team has been asked to help launch an effort to restore 5,000 acres of oysters by 2050.
In New Hampshire, even if all the towns around the bay updated their wastewater systems to meet new nutrient pollution standards, that would address only 40 percent of the problem. The other 60 percent is caused by widespread development-related pollution, which creeps steadily upward as the population density grows. “It’s a very long-term effort to educate people and change behaviors,” says Konisky. The oyster babysitting program helps, and so does a shell-recycling program, where oyster fishermen, restaurants, seafood markets and grocery stores collect and return shells to the bay by way of Grizzle’s lab. “The fact is,” says Konisky, “that for all our efforts to raise awareness and reduce pollution, we’re never going to keep all the excess nutrients out of the bay. But every little bit helps.”
On a brisk day in early December, the two Rays are huddled in the stern of the R/V Meriel B, hoping for signs of Crassostrea virginica. The wind is cold and the current is strong, pushing the lobster boat-turned UNH research vessel hard against its anchor. Grizzle gives the command and a giant rusty claw plunges into the water. Seconds later, the contraption, which works like an oversized pair of salad tongs, is hauled back up, drenching Grizzle’s rubber boots as he grabs the line and swings the loot up onto the deck—a goopy mess of mud and shells.
The researchers are looking for two things: oysters that got their start at UNH’s Jackson Lab, and wild oysters that spawned on their own. Grizzle and Konisky sift through the shells. Lots of clamshells. No oysters. The next several hauls are mostly mud. Ward packs samples into plastic bags to study back at the lab. Everyone works quickly. Urgently. Clouds roll across the late-afternoon sky, gray and heavy. The tongs go down again. Finally, they hit gold—four oysters, each about the size of a quarter.
It would be hard to find a more unlikely candidate for the job of superhero. Small. Immobile. Daring? Hardly. But like any true hero, the oyster has some tenacious enemies. Along with several species of crabs, there’s the oyster drill snail, sea urchin, starfish and octopus. And, then, of course, there are humans—countless oysters meet their demise on an appetizer plate. While they can’t do much to defend themselves, oysters lucky enough to survive boast an impressive list of accomplishments. Erosion fighters, habitat protectors, champions of clean water—oysters do it all. Indeed, the fate of whole ecosystems, the survival of entire species, rest squarely on the unassuming shell of this humble mollusk. Sounds like a job for a superhero.
Also read “Farmers of the Sea”.