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PENN COVE, Wash. – Cookie tray in hand and lifejacket around chest, Laura Newcomb looks more like a confused baker than a marine biologist. But the University of Washington researcher is dressed for work.

Her job: testing how mussels in this idyllic bay, home to the nation’s largest harvester of mussels, are affected by changing ocean conditions, especially warmer and more acidic waters. It’s a question critical to the future of mussel farmers in the region. More important, it’s key to understanding whether climate change threatens mussels around the world, as well as to the food chains mussels support and protect in the wild.

“Along the West Coast, mussels are well-known ecosystem engineers,” said Bruce Menge, an Oregon State University researcher who studies how climate impacts coastal ecosystems. “They provide habitat for dozens of species, they provide food for many predators and occupy a large amount of space, so are truly a ‘dominant’ species.” 

20 million years

Carbon from greenhouse gas emissions has steadily turned seawater more acidic, disrupting organisms accustomed to the slightly alkaline waters of the past 20 million years.

In the case of mussels, an earlier University of Washington lab study found that increased carbon dioxide weakens the sticky fibers, called byssus, that mussels use to survive by clinging to objects like shorelines or the ropes used by commercial harvesters.

“If byssal thread weakening does eventually become important,” Menge added, “the consequences would be major if not catastrophic.”

Newcomb’s goal now is to apply in the real world what was learned in the lab. “Instead of spending a lot of time tightly controlling the temperature and pH conditions mussels grow in, I use the natural seasonal variation to try to answer the same questions,” Newcomb said.

Newcomb’s field office is the rear deck of a harvesting boat – right between the toilet and the microwave. The quarters are cramped, but the view is grand: The blue waters of Penn Cove on Washington state’s Whidbey Island are set against rolling bluffs and snow-capped mountains.

30 percent increase in acidity

The University of Washington marine biologist is there courtesy of Penn Cove Shellfish, which is also the oldest and best known mussel operation in the United States. If you’re a mussel fan, you’ve probably had a few – they’re sold at Costco as well as upscale restaurants across the country.

Placing just-harvested mussels on her tray, Newcomb samples for size, thickness and strength. The mussels are grown on 21-foot-long ropes hanging from several dozen rafts in the bay, and Newcomb takes samples from two depths: Three feet and 21 feet. She also samples water temperature and pH levels at those depths.

Prior to the Industrial Revolution and the explosion of manmade CO2, ocean pH averaged 8.2. Today it’s 8.1, a 30 percent increase in acidity on the logarithmic scale. Computer models peg ocean acidity at 7.8 to 7.7 by the end of the century at the current rate of greenhouse gas emissions.

Washington state is a bit ahead of that curve because ancient carbon stores in the deep ocean are periodically churned up by local currents.