This is your ocean on acid

As emissions continue to rise, the world’s oceans are becoming corrosive, threatening shellfish, corals and the entire ocean food web

On most days, Bill Dewey can be found wearing waist-high waders and inspecting Manila clams—the West Coast version of the littleneck—at his Washington clam farm, Chuckanut Shellfish. Under an arrangement that’s unique to the state, Dewey owns 32 acres of tidelands. Unlike land-based farms, he can only harvest when the tide recedes, leaving over a mile of mudflats, and shellfish, exposed. He gathers the clams with the help of a former tulip-bulb harvesting machine that’s carried out aboard his boat, the Clamdango!

A SHELLFISH STORY

For centuries, shellfish farmers have cultivated oysters in Washington’s Willapa Bay, a massive, shallow estuary separated from the Pacific Ocean by the Long Beach Peninsula. The bay’s warm waters are particularly suited for growing Pacific oysters, identified by their rough, fluted shells marked with purple streaks, and a white interior bearing “a single muscle scar that is sometimes dark, but never purple or black,” according to a Biological Report from the U.S. Fish and Wildlife Service. The oyster was imported from Japan to the western U.S. coast in 1903. “Puget Sound and Washington waters are a little bit cold compared to what the oyster had in Japan,” says Dewey. “So it doesn’t reproduce particularly well here. Except for a few areas—Willapa Bay is one of them. There’s dependable natural reproduction from one year to the next. The water basically has to get up to 72 degrees and stay there for three weeks for the oysters to spawn.”

Beginning in 2005, these oysters in the bay, known as natural sets, stopped reproducing. They have never successfully reproduced since. In 2006, the hatchery-produced Pacific oysters followed suit. In the hatcheries, spawning happens year-round in conditioning tanks where water temperature and algae levels (for food) are closely controlled.

Both Taylor Shellfish and Whiskey Creek Shellfish Hatchery in Tillamook, Oregon, witnessed oyster larvae die-offs that they couldn’t explain and that continued for years. Initially, they suspected a bacteria known as Vibrio tubiashii was to blame. But even after Whiskey Creek installed an expensive filtration system, the oyster larvae continued to die. By 2008, Whiskey Creek, which alone accounts for 75% of all oyster seedlings used by West Coast oyster farmers, had lost 80% of its oyster larvae. Taylor Shellfish had lost 60%. Despite the controlled environment, the ocean water they were pumping into their hatcheries was corrosive. Upwelling—or deep ocean water rising to the surface following north winds off the Washington coast—was carrying acidic water to the surface. The shellfish farmers were experiencing the devastating impacts of ocean acidification sooner than researchers had anticipated. With support from Senator Maria Cantwell (D-WA), ocean acidification sensors were set up in 2010 near Washington’s hatcheries. Combined with Integrated Ocean Observing System (IOOS) buoys from NOAA measuring wind velocity, they track ocean acidity—and predict the upwelling events that cause increased acidity—in real time.

Brita Belli, emagazine.com, 1st May 2012. Full article.


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