Oyster shells help restore chemical balance to acid waters

Healthy young oyster spatThe shells of oysters – a commercially important shellfish whose reproduction and growth is threatened by climate-linked ocean acidification – may help counteract the effects of increased local acidity levels, according to a new study of New England’s Chesapeake Bay by a team of researchers led by Oregon State University’s George Waldbusser.

The study, published in the journal Ecology and reported this week in the New York Times , concludes that the buildup of old shells in undisturbed oyster beds – along with the oysters’ waste – can help restore alkalinity to waters that might otherwise be too acid for the shellfish to survive.

Like ocean waters around the world, the Chesapeake has become more and more acidic as a result of rising levels of carbon dioxide in the atmosphere. Now, by studying oyster populations in relation to acidity levels,Waldbusser’s team has concluded that oysters — particularly their shells — can play a significant role in reducing that acidity.

“Oyster shells are made out of calcium carbonate, so they’re sort of like an antacid pill,” said Waldbusser, an assistant professor of earth, ocean and atmospheric sciences at OSU and an author of the study. “In an undisturbed oyster reef, healthy oysters are generating a lot of biodeposits,” a genteel term for excrement, “which helps generate CO2 to help break down those shells, which helps to regenerate the alkalinity back into the environment.”

Ocean acidification is of great concern to commercial oyster growers. Additional  research by Waldbusser and colleague Burke Hales, conducted at an Oregon oyster hatchery, has shown that increasing acidity near commercial shellfish operations inhibits the larval oysters from developing shells and growing at a pace that makes oyster farming economically viable.

Waldbusser is also working on a Sea Grant-funded project to develop Web-based tools that would allow oyster growers and resource managers to better understand how acidification affects larval oysters so they can more effectively adapt, mitigate and adjust their operations to increase oyster survival and growth.

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