Ocean acidification puts pressure on oyster growers

SEATTLE – After 34 years rearing shellfish in Washington’s Willapa Bay, Dave Nisbet was in a bind: Nature had stopped providing.

Oysters were no longer reproducing naturally on the Washington coast. Oyster larvae were even dying in nearby hatcheries, which use seawater to raise baby shellfish that get sold as starter seed to companies like Nisbet’s Goose Point Oysters.

But when, in 2009, Nisbet heard oceanographers identify the likely culprit – increasingly corrosive ocean water, a byproduct of the same greenhouse gases that contribute to global warming – the oysterman did the unthinkable.

Nisbet took out a loan and spent three years testing and building a new hatchery that opened recently – in Hawaii.

Most of Washington’s $100 million-a-year oyster industry has been whipsawed in recent years by ecological problems. But Nisbet’s oyster company appears to be one of the first businesses in the Northwest – perhaps anywhere – to shift part of its business to a new region in response to ocean acidification.

“I just got nervous,” Nisbet said. “I was afraid if I didn’t do something, then our business would just slowly die.”

Now, rather than relying on oysters that have spawned in Willapa Bay or on juvenile oysters purchased from a nearby hatchery – as he has for years – Nisbet raises larvae in tanks in a million-dollar, 20,000-square-foot plant in Hilo, Hawaii. The tiny larvae are then sent by mail to Washington, where Nisbet and his team oversee the rest of the multiyear growing cycle in Willapa Bay.

“It would have been much easier and cheaper to start a hatchery here,” Nisbet said. “But we just saw the hatcheries having failures, the larvae dying in the tanks, and just decided to sidestep the issue completely.”

Nisbet’s move is just the latest sign of how the threat of ocean acidification is altering the way Washington’s shellfish growers do business.

Scientists for years have warned that excess carbon dioxide from the burning of fossil fuels eventually would be taken up by marine waters and begin lowering the pH of the world’s oceans.

In the past five years, oceanographers at the National Oceanic and Atmospheric Administration working along the West Coast repeatedly have documented that ocean chemistry is already changing, decades earlier than anyone predicted.

Scientists are still learning just how those changes ultimately may upend marine food webs. Researchers have shown that less-alkaline seawater causes sea urchin larvae to change shape, makes squid more lethargic and prompts clown fish to race toward rather than away from predators.

But the type of calcium carbonate used by juvenile oysters during the initial stage of forming their shells is particularly vulnerable to even slight increases in acidity. And the dark, frigid water that wells up from the deep along the Northwest coast during north winds already is naturally richer in carbon dioxide than most ocean surface water.

Those natural conditions combined with greenhouse-gas emissions, scientists reported earlier this year, have turned the tidal currents on Washington’s once oyster-rich coast into a death trap for juvenile oysters. “We’re the tip of the spear for the worst of the worst because of the way the ocean circulates,” said Bill Dewey, with Taylor Shellfish.

Oysters now haven’t reproduced on their own in Willapa Bay since 2005, so every grower now relies on hatchery-produced larvae. Once the oysters make it to that stage, they can survive acidic conditions just fine.

Goose Point Oysters employs 70 people and processes several million pounds of shellfish a year, which are sold all over the world. Since water quality is important to an oyster grower, the company had been following the changes closely.

“We didn’t know what was going on, but we knew by 2009 that we could no longer depend on our current seed supply,” said Kathleen Nisbet, Dave’s daughter.

When her father attended a meeting with NOAA oceanographers, the depth of the problem became clear.

“They said, ‘We’re on an escalator with this thing,’ ” she said. “The problem is going to get worse, and we’re going to have to adapt.”

Kathleen Nisbet had attended the University of Hawaii-Hilo and had contacts there, including Maria Haws, an associate professor of aquaculture. Hawaii also doesn’t experience the same upwelling events and acidification doesn’t appear to be a problem – at least not yet.

“The Northwest is really the canary in the coal mine, though sooner or later we won’t have any place to run if we don’t somehow reverse the trend,” Haws said.

She and the Nisbet family spent several years working out kinks and started operating the hatchery earlier this year.

“Luckily we’ve come out of this not too scarred,” Kathleen Nisbet said. “We think we’ve come up with a way to work around things.”