Researchers are growing native oysters in a lab to return to Elkhorn Slough.

As Kerstin Wasson, research coordinator at the Elkhorn Slough National Marine Estuary Reserve in Moss Landing, steps into a shallow marsh, she’s absorbed waist deep into the mire – a reminder of the near absence of a foundational species and the uphill battle underway to bring it back.

Using thin PVC pipes for leverage, Wasson and master’s researcher Jacob Harris from Moss Landing Marine Labs trudge toward a row of 10 stakes poking out of the low-tide swamp. To the outside observer, the evenly placed stakes, caked under algae and mud and adorned with dirty ceramic squares dangling from zip-tied loops, appear to mark a primal ritual ground, long abandoned by bottom-feeding magicians. A closer look at the tiles – much closer – indeed reveals the once-abundant sorcerers: the translucent bodies of young, lab-bred Olympia oysters.

A matriarchal species leaned on over eons by a diverse range of birds and fish, Native Americans and Gold Rush miners, the West Coast’s only native oyster is as important to the health of estuarine habitats as salt marshes and grass beds. Wasson calls them the temperate climate’s version of coral reefs, fostering biodiversity and fortifying the ecosystem. Yet, as with corals, human influence over recent decades has crippled this critical feature of the California coast.

Without the skeletal structure provided by a healthy oyster population, the floor of the estuary shores soften into a mushy expanse of mud, hostile toward harboring life. Although they can eventually become a tether themselves, a burgeoning oyster colony needs something sturdy to latch onto, such as ceramic tiles tied to metal stakes.

As Harris and Wasson lift the tiles from the water, their expectations are confirmed. Since installing this batch in December, the lab-bred oysters have largely grown from dime-sized to quarter-sized. Those on tiles that sit deeper underwater – where they are less subject to tidal impacts – show greater growth rates.

The oysters are thriving once introduced back into their native habitat. However, the same problem persists as when this project began in 2018: They aren’t having oyster sex and, beyond the lab, the population is stagnant.

“The ultimate metric of success is an oyster population reproducing on its own with consistency,” Harris says.

Wasson and Smith are among a select few oyster ombudsmen leading this “aquaculture” project. The effort to manufacture an Olympia oyster comeback is happening at nine other estuaries between British Columbia and Baja California, the species’ native range.

In contrast to coral reefs, their colorful companions of the tropics, the muck-covered oysters suffer somewhat from a publicity problem, leading this ecological crisis to fly under the radar. At Elkhorn Slough, Wasson estimates the population fell apart between 1929 – when a Stanford PhD student’s thesis noted their abundance – and 1980 – when an estuary survey noted their rarity. Between and beyond, the local species had received scant attention until 2007, when Wasson became curious about the health of the one of the habitat’s ecological pillars.

“Oysters are considered a foundational species, meaning they form habitat and support other species as food, as refuge, and influence the environmental conditions,” Wasson says. “Think redwood forests or native grasslands. When you have oysters, you have a structured habitat where different species can live.”

By 2018, studies showed local Olympia oysters needed a lifeline, with only about 2,500 living in Moss Landing and no new oysters since 2012. Researchers aren’t certain why reproduction has stalled. Although Elkhorn Slough is now protected, it is a changed habitat – a maze of human infrastructure has altered natural tidal flow, and the surrounding agriculture industry means unhealthy fertilizer-rich runoff.

Harris is confident in the return of the oyster population to Elkhorn Slough. “We’re trying one thing at a time to help that happen,” he says.

If successful, oyster aquaculture at Moss Landing could be a commercial tool, selling oysters to local markets. However, that cannot happen until the oysters start having sex.