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Found in Alaskan fisheries, Tanner crabs have been shown to grow more slowly and die off in laboratory studies.

Found in Alaskan fisheries, Tanner crabs have been shown to grow more slowly and die off in laboratory studies.


Worsening ocean acidification threatens Alaska fisheries

A new study finds that Alaska fisheries are particularly vulnerable to the effects of ocean acidification as the region’s seas continue to sour.

The catch from Alaska fisheries—which accounted for 50% of the United States’ total catch in 2009—is part of a complex food web that relies on delicate levels of chemicals in the ocean. But the pH levels in the four seas that ring Alaska—the Chukchi, Beaufort, Bering, and Gulf of Alaska—has dropped by 0.1 units since the Industrial Revolution and is forecast to lower about another 0.4 units by the end of the century. Alaska’s cold waters naturally absorb more carbon dioxide from the atmosphere than warmer waters do, and its upwelling currents bring more acidic waters to the surface, making it harder for organisms like mollusks to form their shells.

Meanwhile, a series of laboratory studies have shown that key shellfish and finfish species—and the microorganisms they eat—could be negatively harmed by those acidified waters, facing risks to their shells or metabolic systems.  

The new research, to be published in Progress in Oceanography, sought to forecast how the risk of souring seas could impact Alaska economically.

The researchers used a computer model to predict how rising atmospheric levels of CO2 would increase the acidity of the ocean around the state in various regions. Social scientists on the team of authors assigned scores to the commercial or nutritional importance of each species to 29 regions around the state, ranking the areas qualitatively by their reliance on affected species and their ability to adapt to this economic loss.

The takeaway? That southwest and southeast regions around the Gulf of Alaska will be particularly hard hit, says oceanographer Jeremy Mathis, the study’s co-lead researcher at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle, Washington. Southeast Alaska is a hub for commercial fisheries, where communities “derive the lion’s share of their economic revenue … directly from the fishing industry,” Mathis says. Subsistence communities, meanwhile, predominate in southwest Alaska, where ocean acidification could threaten food security. “If you take the fish away, they can’t just go down to the grocery store and buy chicken or beef, because it’s prohibitively expensive,” Mathis says.

Alaska’s commercial fisheries pulled in $4.6 billion in harvests in 2009, while fishing-related tourism composes half of Alaska’s income from tourism. Mathis recommends that policymakers help increase job training and educational initiatives, to boost the adaptability of areas facing risk from ocean acidification. But if anything, Mathis says, the study shows why more fieldwork on the impacts of souring seas is needed soon. “This study is not a smoking gun on the impacts of ocean acidification in Alaska,” says Mathis, noting that the authors did not attempt to put dollar amounts on the potential risk to the state. Rather, he says, the work highlights the areas facing the highest risks. And he says it highlights the need for new research cruises to look for the impacts of ocean acidification on species that have shown vulnerability to Alaska’s acidified waters in a number of lab studies. Some of that research has been published as long as a decade ago. “Astonishingly, no one has looked at that yet,” he says.