A Pacific oyster releases its cloudy sperm at Oregon's Whiskey Creek Shellfish Hatchery. In some coastal waters acidification is already severe; here it has cut production in half by stunting oyster larvae. David Littschwager / nationalgeographic.com

By Eric Scigliano
18 August 2011 In the summer of 2007, something strange and troubling happened at the Whiskey Creek Shellfish Hatchery on Netarts Bay in Oregon, which raises oyster larvae for shellfish growers from Mexico to Canada. The hatchery’s “seed,” as the oyster larvae are called, began dying by the millions, for no apparent reason. Disease isn’t uncommon in a hatchery’s tanks, but that same year, up the coast in Washington, wild oyster larvae also failed in Willapa Bay, which has been the heart of the Pacific Northwest’s oyster industry since the 1850s. The Willapa Bay growers scrambled to replace their natural beds with farm-raised seed from Whiskey Creek and other hatcheries. But there was very little of it to buy. Washington state’s Taylor Shellfish Farms, the Pacific Coast’s largest grower, also lost most of its larvae that year. The situation was dire. Whiskey Creek and Taylor are key links in the nation’s seafood supply chain. They and another Washington hatchery provide nearly all the seed for the West Coast’s growers, who in turn produce more than a quarter of the 700 million or so farmed oysters that Americans slurp down every year. […] They eventually found a larvae-eating bacterium called Vibrio tubiashii raging through their tanks. Attacking it with maximum force, they hired an engineer-turned-hatchery manager from Oregon State University named Alan Barton to build a $200,000 state-of-the-art system to filter and sterilize the water they drew from the bay. It squelched the Vibrio but failed to stop the carnage; the infestation, it seemed, was a symptom of some underlying problem, rather than the cause. The larvae were still dying, and Cudd and Wiegardt were facing ruin. So were many of the Pacific oyster farmers who relied on them. […] In July 2008, all of the remaining larvae at Whiskey Creek died suddenly. At the same time, the water in Netarts Bay (and hence in the hatchery’s tanks) became noticeably more acidic — an indication that it had welled up from lower depths offshore. […] It was the breakthrough Whiskey Creek’s operators had been waiting for. The culprit behind their die-offs, it turned out, was part of a much bigger change in oceans around the world. Called “ocean acidification,” it results from too much carbon dioxide in the atmosphere. The sea is the world’s great carbon sink, holding about 50 times as much of the element as the air. Phytoplankton at the ocean’s surface absorb carbon dioxide for photosynthesis, and when the tiny plants die, they sink and decompose, releasing CO2 into the water column. Dissolved CO2 forms carbonic acid, the same weak acid that gives soda water its tang. Cold water can hold more CO2, so the frigid waters at the ocean bottom are more carbon-saturated, and more acidic, than the warmer surface water above.  […] Already, Barton sees the problems that nearly shut down the West Coast’s hatcheries settling in on the East, thanks both to local conditions and, he believes, to bigger changes in the sea itself. That’s good for his business, at least in the short term; natural oyster beds have failed in many East Coast estuaries, just as they did on Willapa Bay, and Eastern oystermen are turning to hatcheries like his for seed. But his current success will be cold comfort if carbon emissions don’t abate and the sea undergoes catastrophic change. “I’m afraid the ocean will be dead long before we have to worry about the other implications of global warming,” Barton says quietly. “I didn’t believe any of this stuff three years ago. I was always skeptical about our global models … But ocean acidification is pretty cut and dried for me now. You see it every day. You can’t escape it.”

The great oyster crash