Can oysters save San Francisco’s shoreline from climate change?

Repopulating the Bay Area’s native reefs holds promise

Linda Hunter strolled into the Bay Natives nursery in Bayview on a crisp fall day and casually greeted a herd of goats and a flock of multicolored chickens.

Holding a white plastic bucket brimming with discarded oysters from local restaurants, Hunter scattered the used shells about. Lunch, at least for the chickens, was served.

Left: Volunteer Charlotte Hill serves shells collected from restaurants to Bay Natives Nursery’s hens, which will pick them clean. <ins>(Kevin N. Hume/The Examiner)</ins>

Left: Volunteer Charlotte Hill serves shells collected from restaurants to Bay Natives Nursery’s hens, which will pick them clean. (Kevin N. Hume/The Examiner)

“If you leave that little bit of muscle on there, then they get really stinky, also attract critters,” said Hunter. “So, the chickens clean them up for us.”

These shells, once cleaned by chickens and cured in the sun, could eventually help form new oyster reefs in San Francisco Bay. Hunter’s nonprofit, the Wild Oyster Project is just one of a number of organizations working to revive the Bay’s native Olympia oyster population and build new reefs in sub-tidal zones to buffer against worsening impacts of climate change.

Called “living shorelines,” native oyster reefs, eelgrass beds and other wetlands projects are starting to be established throughout the Bay Area, including San Francisco’s Pier 94, Heron’s Head Park and Crissy Field’s Quartermaster Reach Marsh, in an effort to buffer against sea-level rise, reduce wave energy, and prevent shoreline erosion.

“A lot of people think it means a beautiful, healthy shoreline,” said Marilyn Latta, a project manager with State Coastal Conservancy, who oversees several living shoreline sites in San Rafael, Richmond and Hayward. “Which is true,” she said, adding that living shorelines are also “really important in providing habitat and green infrastructure that helps to strengthen our ability to adapt to climate change.”

San Francisco Bay once teemed with Olympia oysters. So much so, that their abundance under-girded an important fishery here in the 1850s. But as the Bay Area became increasingly urbanized and tastes trended toward the larger eastern oysters, the local fishery collapsed. Native Olympia populations began to die off.

Today, scientists estimate oyster grounds in San Francisco Bay to be around 1% of historic levels.

Discarded oyster shells dry on a roof at Bay Natives Nursery. <ins>(Kevin N. Hume/The Examiner)</ins>

Discarded oyster shells dry on a roof at Bay Natives Nursery. (Kevin N. Hume/The Examiner)

But that could soon be changing. Scientists have deployed several reef structures made from bags of discarded shells, cement reef balls and fiberglass panels throughout the Bay to attract juvenile oysters, which swim freely through the water column with wing-like appendages before attaching to rocks, shells and other substrates.

“Their whole scientific name is Ostrea lurida, which means shell loving,” said Latta. “So, they are attracted to the shell.”

But restoring native reefs is not as easy as spraying shells into the water and hoping oysters adhere to them. For starters, there’s simply less habitat in the Bay today for oyster recruitment. According to Latta, the Bay — one of the most urbanized estuaries in the country — has shrunk by nearly a third as cities have filled it in.

California’s steep coastlines and intense wave energy also pose challenges for restoration and research.

“It’s cold in these waters, it’s murky in these waters because there’s a lot of sediment, so it’s not clear water. There are high currents,” said Latta. “It’s difficult to map and conduct work.”

While Hunter has ambitions to create a series of oyster reefs like that of the Billion Oyster Project in New York City, experts are skeptical it’s possible here. Unlike eastern oysters which build tall reefs by stacking on top of one another, Olympia oysters, which are also significantly smaller than their eastern counterparts, tend to create shallower structures.

“As far as we can determine, they make what we call beds rather than reefs,” said Chela Zabin, a researcher at the Smithsonian Environmental Research Center.

That said, these bivalves can help buffer against worsening storm surges and sea-level rise. “Oyster beds certainly slow down and reduce wave stress,” said Ted Grosholz, a professor of Environmental Science at UC Davis.

Olympia oysters have also become integral to the restoration efforts at the Presidio’s Quartermaster Reach, a marshy interface where a freshwater creek flows into the salty Crissy Marsh and ultimately, out to the bay.

A restoration effort for oysters is underway at the Presidio Quartermaster Reach. <ins>(Courtesy Jonathan Young)</ins>

A restoration effort for oysters is underway at the Presidio Quartermaster Reach. (Courtesy Jonathan Young)

Over the last year, ecologist Jonathan Young has worked to attract oysters onto recently installed reef balls and fiberglass panels. So far, his efforts seem to be paying off.

“It’s working so far. They’re here. They’re growing,” said Young. But he added, “We’re still in the very early stages…we’re not 100% sure how it’s going to pan out.”

After October’s atmospheric river dumped historic rains onto The City, Young worried about how these newly recruited oysters, which need a certain amount of salinity, would fare.

“I would predict that some of those oysters aren’t going to survive,” he said. “They can handle some freshwater influx, but if it’s sustained freshwater for too long, they just die.”

Despite the challenges of restoration work and the pressures of a changing climate, scientists have seen promising results, not just for oysters, but for the entire ecology of the Bay.

“It shouldn’t be called oyster restoration. It should be called food web restoration,” said Grosholz.

In many ways, oysters act as the structural scaffolding that props up the rest of the marine food web. Not only do the physical beds provide refuge for crabs, small fish and invertebrates, but scientists like Zabin and Grosholz have also noticed rare birds and migrating fish like green sturgeon showing up at test sites.

“Oysters have a lot of superpowers,” said Hunter. “One of their superpowers is they create this ecosystem for other critters.”

While Zabin is doubtful that the bay will become the thriving oyster haven of old, she stressed the value of building a robust native ecosystem here. “The native oyster is like the Golden Gate Bridge. If you’re looking at a native oyster, you know you’re on the West Coast, you know you’re in San Francisco Bay,” she said.

“This is the same oyster that the Native Americans ate. It’s the same oyster that the Forty-Niners ate when they came out to the West Coast before the railroad was built. … So just as we place a value in preserving languages and cultures, I think there’s value in preserving what was here in terms of the native species that were part of that and makes us who we are.”

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