It’s a global issue. Among major shellfish producers, New Zealand is creating an acidification monitoring network while resear

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publicized research that shows oyster larvae in hatcheries along Washington’s coast are having trouble forming shells because of the acidic waters.

“Mussels are the new oysters,” Carrington says. But there’s a twist: Mussels confirm that ocean acidification’s impact extends in mollusks beyond an inability to form a shell.

The lab finding is “part of a growing body of evidence that ocean acidification alone and combined with other stressors will have effects beyond shell mineralization,” says Terrie Klinger, a University of Washington marine sciences professor studying the impacts of acidification.

Other research, she said, shows more acidic seas spur “changes in fish behavior and toxin production in harmful algae.”

Penn Cove Shellfish and the UW researchers joined forces after company harvesters saw empty patches on some cultivation ropes that should have had mussels. Was that due to weakened byssus?

“We had a significant amount two years ago, and little bit less last year,” says Ian Jefferds, general manager at Penn Cove Shellfish. “The question arose, ‘Was there something related to that?’” Concern about what the industry calls “slough-off” goes well beyond Penn Cove. “We know that mussel slough-off has periodically been an issue but we don’t know why,” says Margaret Barrette, director of the Pacific Coast Shellfish Growers Association.

It’s a global issue. Among major shellfish producers, New Zealand is creating an acidification monitoring network while researchers in Spain are planning a study similar to that in Penn Cove.

And across the Mediterranean, mussel farmers have reported problems. “A great majority of producers experienced important difficulties in past years as a consequence of summer heat waves,” says Luis Rodrigues, a researcher with a European Commission panel studying acidification.

Those issues include slough-off in Italy and Montenegro, as well as thinning of shells and even die-offs in waters that topped 82.4 degrees.

A related lab study showed “total mortality” of mussels when exposed to waters above 82.4 degrees, said researcher Frederic Gazeau.

That team also “observed a very clear impact of acidification on the capacity of mussels to produce their byssal thread,” noted Gazeau. “At low pH, it was very easy to pick up mussels individually; they could not attach themselves anymore.”

Of course, it’s not just loss on the farms that worries scientists. In the wild, mussels form vast beds along coastlines, and some areas have seen slough-off as well.

“It’s quite common in California in recent years,” says Herb Waite, a University of California, Santa Barbara, biochemist who studies mussels. “A favorite collecting spot will suddenly disappear.”

Any widespread slough-off in the wild could have other repercussions as well. It hasn’t happened yet, but researchers are worried.

Mussel beds in sandy areas “stabilize shores against erosion,” Waite noted, and any loss there could expose beaches to the erosive power of waves.

Carrington thinks her team’s research could lead to an “early warning system” for a global mussel farming sector valued at $1.5 billion a year.

Establishing pH thresholds, farmers could better monitor areas and, if needed, seek out safe havens in less acidic and cooler waters.

“It does matter where in the water mussels are,” Newcomb added, noting that even preliminary results suggest growing them closer to the surface tends to mean less acidity. However, a tradeoff there can be warmer temperatures.

The research will need two more years of data gathering before any definitive conclusions, but Carrington said the earlier lab tests underscore the need for field data.

“Would you be worried about being weakened by 40 percent?” she asked. “I would be.”

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