By Cynthia Drummond | Courtesy of the Westerly Sun

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NARRAGANSETT — As more carbon dioxide is pumped into the earth’s atmosphere, approximately 25 percent of it is being absorbed by the ocean, where it forms carbonic acid and changes the pH balance of seawater. Ocean acidification is a less-studied effect of the complex process of climate change, but one that many researchers believe is important to understand.

Scientists are trying to determine how a more acidic ocean will affect the organisms that live there. Some of them, oysters, clams and sea scallops in particular, are commercially important to Rhode Island, and a lower pH makes it harder for the mollusks to obtain the calcium carbonate they need to build their shells.

“The impact that has gotten the most attention is the effect on organisms that use calcium to build skeletal structures,” said Jason Grear, a research ecologist at the Environmental Protection Agency Laboratory in Narragansett. “That would be things like shellfish and corals. But there are also plankton that use calcium in building their cellular structures, and there are even marine snails that swim in the water column. All of those are organisms that use calcium minerals to build their structures are therefore really sensitive to changes in pH, because that change in pH changes the availability of those calcium bio minerals.”

Robert Rheault, executive director of the East Coast Shellfish Growers Association, which represents growers from Maine to Virginia, is waiting for more scientific evidence to show how an increasingly acidic ocean will affect oysters and clams.

“Right now, the science on the impacts is weak,” he said. “The only thing that we know for sure is that the larvae, in that first 48-hour period before they start feeding, are tremendously susceptible to dissolution. Their energy budget goes negative because they haven’t started to feed yet, and if they haven’t got enough energy in that egg and they’re starting to dissolve, then it takes extra energy to lay down shell, and they sometimes don’t make it.”

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