Climate change threatening indigenous oysters

Carbon in the atmosphere is falling into the oceans, increasing acid levels, and impacting shellfish.
January 21, 2014 8:37:13 PM PST
Global warming isn't the only consequence of climate change. Carbon in the atmosphere is falling into the oceans, increasing acid levels, and impacting shellfish. Oysters are in the crosshairs of this future crisis.

Around the Bay Area, the name Tomales Bay is closely associated with eating oysters. But there is one type of oyster they will not be eating on the beach there -- the native Olympia oyster has all but disappeared.

If you want to find Olympias in abundance, look up Eric Sanford, Ph. D., at the Bodega Marine Lab. He has been raising them to study the effects of that global warming-bookend crisis also known as ocean acidification.

"So as carbon dioxide goes into the oceans, it's like adding carbonation, makes it more acidic," Sanford said.

And acid eats shells. For several years, Sanford has been growing the oysters in the kind of acidic ocean water we'll have a few decades from now. He expected the shells to be thinner, but instead, the Olympias have adapted by growing 30-40 percent smaller. But that presents another problem relating to a non-native predator, a snail called the Atlantic oyster drill.

"They have an organ in one foot that secrets acid and then a file in their tongue that files away their shell," Sanford explained.

Essentially, they drill through the shells to eat the oysters alive. And because the oysters aren't as large as they used to be, they're eating more of the oysters.

In bays from Mexico to Washington, including Tomales, 99 percent of a formerly healthy population has disappeared. This matters because if ocean acidification makes one species vulnerable, it could also affect the oysters we eat.

"We would expect them to grow more slowly, take longer to actually reach market size, become more expensive because growers will have to spend more time," Sanford said.


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