Ocean acidification and oysters: Shellfish are already suffering.

The Pickled Ocean Is Eating Away at Oysters, Clams, and Sea Butterflies

Which species will adapt to climate change—and which ones won’t.
Feb. 18 2013 1:20 PM

Are Oysters Doomed?

Don’t believe in climate change? Talk to a clam digger.

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Unlike other problems caused by CO2, ocean acidification is spurring some action, possibly because the effects are so visibly tied to the cause. “With climate change there’s often a schism between scientists and those who flat out don’t want to believe it,” says Green. “It’s hard to get a man to believe something if his job depends on not believing it.” But in this case, he says, it’s the people in the industry who are leading awareness. “Talk to shellfish clammers—the guys who dig—and every one of them is on board, especially the old timers. They have seen over the years the populations go from incredibly productive to virtually disappearing in many cases.” One bit of anecdotal evidence diggers have reported is clams with thinner shells—so thin, they say, that sometimes it’s not possible to fill bushel baskets to the top because the fragile shells at the bottom will be crushed.

For the diggers, a scientific fix is the only hope they have of saving their industry. But even the best near-shore solution can’t stop the pH drop that’s taking place oceanwide, not unless we plan to stop releasing carbon dioxide into the atmosphere and replace it with Milk of Magnesia.

Last fall, some of the first evidence of how ocean acidification is affecting organisms in the wild came from scientists investigating Southern Ocean pteropods, tiny marine snails also known as sea butterflies. NOAA’s Nina Bednarsek, lead author of the report, says the team found dissolving shells in pteropods at far shallower depths than expected. The spiraling shells were pitted and peeling like paint on a neglected house. “It was fascinating and a bit disturbing to see,” she says. The dissolution won’t necessarily kill pteropods, “but they will definitely be more vulnerable to predators and infectious diseases.” Pteropods are an abundant, important part of the ocean food web, preying on the ocean’s phytoplankton—drifting plants—and providing food for larger species. Pteropods make up 50 percent of the diet of pink salmon in the North Pacific. According to NOAA chemical oceanographer Richard Feely, a 10 percent drop in the production of pteropods produces a 20 percent weight drop in a mature pink salmon. Sea butterflies are an indicator species, showing that ocean acidification is already affecting marine ecosystems.

The long-term projections for ocean acidification make people even more anxious.Even if we change our CO2 emissions policies today, the problem’s going to get worse in the next 30 to 50 years before it gets better,” says Dewey, given how long carbon dioxide persists in the atmosphere. “We’re anticipating that down the road it is probably going to affect our adult oysters as well as our seedlings.”

The corrosive surface water scientists are measuring is in effect a time capsule from the 1960s. Carbon dioxide is absorbed by phytoplankton on the water’s surface. When those organisms die, they sink deep into the ocean, taking the CO2 along for the ride. At depth, the dead phytoplankton release the CO2 back into the water. For this and other reasons, the deeper ocean tends more toward acidity than shallow waters. In places where we are seeing the effects of ocean acidification first, such as the northwestern United States and the parts of the Southern Ocean studied by Bednarsek, that old, corrosive water has risen to the surface. As the years pass, that upwelling water will have a lower and lower pH, reflecting the increase in our carbon dioxide output from the 1980s, the 1990s, and today. By midcentury, it’s likely that about 50 percent of the seawater will be too corrosive for growing oysters.

It’s like: holy crap,” says Dewey. “Seawater conditions are getting such that they are dissolving our animals, and the source of that problem is global CO2 emissions—what can we possibly do? Even a big shellfish company like ours can’t fix that problem.”

As with climate change, ocean acidification will require more comprehensive, aggressive measures. But, hey, if we don’t fix this? We’ll need to invent some new recipes for jellyfish and seagrass.

Maria Dolan is a freelance writer in Seattle. Follow her on Twitter.

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