Ocean acidification responsible for deaths of billions of baby oysters in Pacific Northwest

By Craig Welch / The Seattle Times

Researchers said Wednesday they have conclusive evidence that ocean acidification is at least partly responsible for killing oysters on the West Coast.

It’s been eight years since baby oysters started dying by the billions at an Oregon hatchery and in Washington’s Willapa Bay.

In 2009, top scientists drew global attention when they said evidence suggested the culprit might be changing ocean chemistry from the same greenhouse gases that contribute to global warming. They just couldn’t prove it — until now.

Researchers said Wednesday they can definitively show that ocean acidification is at least partly responsible for massive oyster die-offs at the hatchery in Netarts Bay, Ore.

It’s the first concrete finding in North America that carbon dioxide being taken up by the oceans already is helping kill marine species.

“This is the smoking gun for oyster larvae,” said Richard Feely, an oceanographer and leading marine-chemistry researcher with the National Oceanic and Atmospheric Administration in Seattle and one of the paper’s authors.

Said Alan Barton, another of the paper’s authors: “It’s now an incontrovertible fact that ocean chemistry is affecting our larvae.”

In a paper published this week in the journal Limnology and Oceanography, the scientists studied the water that gets pumped from the Pacific Ocean into the Whiskey Creek Hatchery, which supplies baby shellfish for most of the West Coast’s $110 million-a-year oyster industry.

Here’s why: Since 2005, wild oysters along the Washington coast and at the hatchery had been dying inexplicably in their larval stages. At first the suspect was a bacterial disease, but hatchery workers soon noticed that the die-offs only occurred after high winds drew water from the ocean deep.

Unlike the complex mechanics of climate change, ocean acidification is just basic chemistry. Scientists long had predicted that as carbon dioxide from fossil fuels gets taken up by the seas, ocean waters — typically slightly alkaline — would slide closer to the acidic side of the pH scale. They just expected it would take 50 to 100 years.

But Feely and other top researchers in 2007 and 2008 had discovered that the pH of marine waters along the West Coast had dropped decades earlier than expected.

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