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Ocean Acidification Could Mean Smaller Scallops, Threatened Industry

Eve Zuckoff
Juvenile sea scallops in the Aquaculture and Marine Systems Laboratory at Mass Maritime Academy in Bourne. There are more than 10,000 scallops in this lab's nursery.

In a new experiment, scientists working at the Mass Maritime Academy in Bourne are finding that ocean acidification may have a profound effect on juvenile sea scallops.  

Scientists at the Academy, in partnership with the National Oceanic and Atmospheric Administration (NOAA), are exposing sea scallops to three different levels of acidity, to see how they adapt to changing ocean chemistry.

Over the last 25 years, oceans have become increasingly acidic and that trend is expected to continue, as the water absorbs greenhouse gases produced by human activity.

“Research has shown that other bivalves [like oysters, clams, and quahogs] are affected by ocean acidification,” said Shannon Meseck, a research scientist at the NOAA Fisheries Millford Laboratory. “But to date, there's no published research on the sea scallop, which is surprising because it is the second most important fishery in the Northeast. Second, to lobster.”

When Meseck started working toward her PhD more than two decades ago, she said, she learned the pH of the ocean—which measures its acidity—was 8.15. Today, the pH has dropped to 8.1, and in the next 100 years it could be as low as 7.8.

The findings raise concerns locally, as the port of New Bedford leads the nation in scallop landings, bringing in revenues of more than 300 million dollars annually.

The experiment itself is only 8-weeks long, and future modeling to determine long-term growth of scallops exposed to high levels of acidity will be necessary, but early results show juvenile scallops exposed to more acidic conditions are growing slower than their counterparts.

And still, Meseck says, we’ve only just begun to ask right questions.

“For example, if it takes four years to harvest now, what if it eventually would take six years [for scallops] to get to harvest size? How would that affect our economy and our food source?”

Beyond size, she adds, ocean acidification weakens scallops’ shells, putting them at even greater risk.

“They may not exist if they can’t make it past the larval stage because their shells are dissolving. That’s a big issue,” she said.

New Bedford has been home to the most valuable fishing port in the nation for almost 20 years on the strength of its scallop fishery. Longer growing periods, could threaten this economy.

Still, Meseck notes, individuals can help scallops and the industry that relies on them by limiting carbon emissions that they’re responsible for.

“Reducing our CO2 footprint is something that everyone can do. Even the smallest amount makes a difference.”

Eve Zuckoff covers the environment and human impacts of climate change for CAI.