Stakes are high with ocean acidification

Lobsters are already slowly moving out of southern New England as waters warm, but the iconic crustacean faces another future threat as the climate changes.

As oceans absorb more carbon and become increasingly acidic, juvenile lobsters will likely have a harder time growing and forming strong shells to protect them from predators, according to a recent University of Rhode Island study.

“I’m not sure yet what the mechanism is that is affecting their growth,” said URI doctoral student Erin McLean who led the research. “But it takes energy for them to regulate the increased acidity, which is energy they cannot then put toward growth.”

And it’s not just lobsters that could be harmed by the oceans’ changing pH levels. Shellfish populations in Rhode Island and Massachusetts in general are among the most vulnerable in the United States to ocean acidification, according to a recent study in the journal Nature Climate Change.

The study identified the two states among 15 at-risk areas in the nation because colder, northern waters, such as Narragansett Bay, Buzzards Bay and Nantucket Sound, are absorbing more carbon dioxide from the atmosphere and acidifying faster than warmer waters.

Other more localized factors are also playing a part, including nutrient pollution from fertilizers and sewage systems that can add more carbon to the water and the flow of fresh water from poorly buffered rivers, such as the Blackstone in Rhode Island or the many waterways that drain into the Gulf of Maine, that lack minerals to mitigate the effects of acid. Shallow coastal waters are also more susceptible to changes in the ocean’s chemistry.

About a quarter of all carbon emissions from power plants, cars and other sources are absorbed by the oceans, making them more acidic and reducing carbonate levels. Shellfish use carbonates to make their shells, and when fewer of the compounds are available, organisms must expend more energy to build shells and less on eating and survival, researchers say.

The stakes are high in Rhode Island and Massachusetts because of the value of shellfish as an environmental, cultural and economic resource. Southern Massachusetts makes more money from shelled mollusks than any other region in the United States with annual harvests in Bristol and Plymouth counties, Cape Cod and the islands totaling more than $300 million in revenues annually in recent years. And tiny Rhode Island ranks seventh in the nation in economic dependence on shellfishing, with annual harvests bringing in an average of $14 million over the past decade.

While Rhode Island’s wild quahog beds have recovered over the past several years after decades of decline, the state has also seen a steady increase in aquaculture. There are now 52 farms in the state, and the total value of their products — mainly oysters — has more than doubled in the past five years to $4.2 million, according to the state Coastal Resources Management Council. In Massachusetts, the value of farmed oysters and other shellfish was estimated at $25.4 million in 2013, according to the state Executive Office of Energy and Environmental Affairs.

Alex Kuffner, Providence Journal, 18 December 2015. Full article.

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