Humble Hero
Can the oyster really save our rivers and bays?

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Great Bay by Fred Meissner '14
Photo of Great Bay courtesy of Fred Meissner '14

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.

Ray Grizzle Erin Gleason/UNH Photographic Services
Researcher Ray Grizzle throws oyster shells with spat attached into the 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.

Ray Konisky Rich Beauchesne/Portsmouth Herald
IN THE BAG: Marine ecologist Ray Konisky '03G orchestrated the building of a new oyster reef using 100 tons of clamshells transported by barge in giant feedbags.

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.

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