Oregon State University

The Whiskey Creek Shellfish Acid Tests

Baskets of oyster shells on Netarts Bay

by Nathan Gilles

The sun chips away at the marine layer on this swiftly warming May morning in the bay. On the estuary’s muddy banks, clammers dressed in knee-high rubber boots dig in the dark sludge, while throughout the bay other aquatic farmers dredge for their prize: oysters.

The oysters are Crassostrea gigas, commonly called the Pacific oyster. These “giant oysters” measure from 3 to 15 inches long. They’re huge moneymakers for global aquaculture, and they have a special relationship to this place. This is Netarts Bay, Oregon, the center of the state’s oyster industry and home to the Whiskey Creek Shellfish Hatchery, one of the nation’s largest producers of Pacific oyster larvae. Hatcheries such as Whiskey Creek are linchpins for industry. That’s because the Pacific oyster is originally from Japan, and here on the west coast its delicate larvae grow wild in only a handful of places. For oyster growers from California to Canada to succeed, hatcheries must raise larvae. Unfortunately, as an incident at Whiskey Creek proved, the larvae are under siege.

In 2007, Pacific oyster larvae at Whiskey Creek started dying en masse. Oregon State University scientists later pinned the crime on ocean acidification. This is the term many are using to describe what’s happening in the world’s oceans as excessive atmospheric carbon dioxide (CO2)—a product of human industry’s hunger for fossil fuels—is dissolved in seawater. Once it’s in the ocean, CO2 forms carbonic acid, which lowers the water’s pH level, making it more acidic. The consensus is that ocean acidification is just getting started. As CO2 is continually pumped into the air, the world’s oceans are expected to slide further toward the acid side of the spectrum, and that, say researchers, won’t be good for animals like the Pacific oyster. That’s because oysters and other mollusks make their shells from calcium carbonate, which is becoming increasingly susceptible to breaking down in our ever-more corrosive seas. This is what happened at Whiskey Creek: the seawater in which the hatchery was raising its larvae had succumbed to ocean acidification; the larvae struggled to make shells, and died. But this isn’t the whole story.

Today, with Oregon Sea Grant’s help, OSU researchers are continuing to investigate ocean acidification’s nefarious ways. They’re gaining a better understanding of oyster larvae’s response to the phenomenon. They’re developing better seawater monitoring techniques. And they’re connecting with stakeholders in an effort to develop useful diagnostic tools for hatcheries and growers. Yet getting to this point took time. When the hatchery’s larvae started dying, it was mystifying.

Acid’s first inklings

The tide is very low. The moon has pulled back the saline blanket covering Netarts Bay, revealing a normally concealed landscape of sandbars, muddy flats, and Whiskey Creek’s intake pipes.

“It’s usually not like this,” says hatchery employee Alan Barton, gesturing at the bay. “There’s usually water over all this.”

Barton is standing on the estuary side of a two-lane road hugging the bay, with Whiskey Creek behind him. In front of him, a small slope declines toward the bay. Jutting from it are two intake pipes. They hang mid-air over a still-submerged bed of aquatic eelgrass.

Normally, these pipes help pump between 100 and 200 gallons of water per minute into the hatchery. Not today. Today, other pipes—still underwater—do it all, pumping bay water, under the road and to the hatchery, where it’s treated and then dumped into massive tanks filled with Pacific oyster and other shellfish larvae.

Barton is wearing a T-shirt bearing NASA’s logo. It’s an odd choice for such a down-to-earth guy, which is exactly what he purports to be.

“I don’t do science,” says Barton. “I work in a hatchery.” Although that may be true, everyone agrees he was the first to solve the mystery.

In 2012, Barton and the hatchery gained national attention when he and several OSU researchers published a paper announcing they’d discovered that the bay water drawn from those intake pipes was killing the hatchery’s Pacific oyster larvae.

Getting to that conclusion took time. At first, the only thing anyone knew was that something was horribly wrong.

“We had three or four months when we had zero production. We’d never seen anything like it,” says Mark Wiegardt.

Sue Cudd strains oyster larvae from tanksWiegardt owns a small oyster farm on the bay’s south end. Since 1997, his wife, Sue Cudd, has owned and operated Whiskey Creek, with what he says is modest input from him. True to his words, as Wiegardt is outside, leisurely relating the tale of the hatchery’s bad acid trip, Cudd bustles among the rows of enormous tanks. Using trays covered in fine netting, she’s sifting tank water for nearly microscopic organisms no wider than a strand of human hair. The result of her sieving is what looks like a mess of fine mud. But it isn’t mud; it’s Pacific oyster larvae, millions per tray. Larvae that at two weeks of age are put on ice, placed in insulated boxes, and next-day shipped to oyster growers the world over, growers who then raise the animals to maturity before the tasty critters end up as someone’s dinner.

All that’s happening inside. Outside, Wiegardt is hunched over his truck bed, separating oysters for breeding and describing how the hatchery and its OSU helpers uncovered the larvae killer.

Weigardt says the troubles began in the late summer of 2007. “To be honest, we didn’t know what was causing it,” he says, “but [Vibrio] tubiashii was present, so at first we thought it was that.”

A bacteria named Vibrio tubiashii (V. tubiashii) was the initial culprit on the hatchery’s wanted list. V. tubiashii preys on Pacific oysters and occasionally blooms when conditions are right. Suspecting a pathogen was at work, Wiegardt started sending samples off for testing. Sure enough, the water tested positive for V. tubiashii. To ward off future outbreaks, Whiskey Creek installed an enhanced system to cleanse the incoming water. This helped, but, says Wiegardt, “There were definitely still problems.”

With their new defenses up and running, Whiskey Creek hired Barton as monitor. Then came another die-off, only this time the water was nearly clean of V. tubiashii. Something else had to be at work.

At the time, Barton was perusing Richard Feely’s work. Feely, an expert in chemical oceanography at the University of Washington, had concluded ocean acidification’s low pH waters were corrosive to calcium carbonate, a necessary ingredient in oyster shells.

That’s when Barton thought maybe the larvae slayer was ocean acidification. To test this, he sent water samples to OSU Professor Burke Hales, also an expert on ocean chemistry. After testing the water, Hales—who continues to work closely with the hatchery, and was a co-principle investigator on that 2012 paper—confirmed Barton’s suspicions. “Pretty soon,” says Wiegardt, “it became obvious…we had a pH problem.”

Understanding how the hatchery’s corrosive waters made their mayhem came soon after.

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