Puget Sound and the Salish Sea are on the leading edge of an ocean acidification crisis that could devastate West Coast fisheries within decades, UW research says.
SEATTLE —
The waters off the Pacific Northwest are becoming more acidic at a faster rate than the rest of the world’s oceans, a global problem exacerbated by the region’s unique geography, according to a University of Washington study.
Researchers found the California Current System, which runs along the West Coast from British Columbia to Baja California, and the Salish Sea, which includes Puget Sound, have experienced amplified acidification over the past 130 years, outpacing the rise in atmospheric carbon dioxide.
“We are already naturally acidic and then we see this bump and then we’re saying that extra bit is increasing faster than we expected,” said Alex Gagnon, an associate professor of oceanography at UW and principal investigator on the study.
The Pacific Northwest is naturally prone to acidic ocean conditions because of a process called upwelling, in which cold, nutrient-rich water is pulled up from the deep ocean to the surface.
“It’s almost like we have a straw in Puget Sound, waters off the coast,” Gagnon said. “So that makes Puget Sound, Salish Sea really productive, an incredibly great place for fisheries, for many of the organisms that we care about to live and flourish, but it also brings this acidic water with it.”
When atmospheric carbon dioxide, from tailpipes, power plants and burning forests, is then absorbed by the ocean, it compounds an already acidic environment. The oceans absorb roughly a quarter of all CO2 emitted into the atmosphere.
The study found that below 50 meters depth, ocean carbon dioxide levels in the California Current have outpaced the rise in atmospheric CO2 by 50% over the 20th century. The deeper the water, the worse the acidification.
The findings were made possible in part by tiny, unassuming creatures: orange cup corals collected more than a century ago.
“These little corals are growing all along the West Coast of the U.S.,” Gagnon said. “As they grow, their skeletons are grabbing information about seawater into them, and then they preserve them. They lock them into the skeletons. They’re like these little time capsules.”
Scientists used boron isotopes preserved in the coral skeletons to reconstruct ocean chemistry stretching back to the 1890s, before the Industrial Revolution significantly altered atmospheric CO2 levels. The historic specimens came from the Smithsonian National Museum of Natural History, collected by the crew of the USS Albatross, the country’s first purpose-built research vessel.
“The USS Albatross, an old wooden tall ship, was going up and down the West Coast of the United States in the 1890s, 1880s, looking for halibut fisheries,” Gagnon said. “There were scientists on board who were dutifully, when they were looking for halibut, anything else they caught in their nets, they were putting in jars, taking notes, and we still have the log books from the 1880s, 1890s.”
Those preserved specimens were then compared to modern corals collected from the same locations in 2020, revealing a measurable and significant shift in ocean chemistry.
The accelerating acidification has direct consequences for marine life, and the people who depend on it.
“Marine organisms that make shells or skeletons, whether that’s oysters, crabs, corals, they rely on having the right ocean chemistry around them,” Gagnon said. “And as that ocean chemistry changes because of us, it makes it a lot harder for them to grow.”
The study specifically calls out Dungeness crab, the largest fishery on the West Coast by revenue, as facing reduced growth and survival in early life stages as acidification worsens. Shellfish industries along the coast are already feeling early impacts, researchers say.
Under a high-emissions scenario, the study projects that by the end of the 21st century, pH levels in the subsurface California Current could drop by 0.30, equivalent to the total projected change for the global surface ocean, while some areas could see pH levels as low as 7.5.
“That business as usual scenario has really dire consequences for marine ecosystems, for the fisheries we care about,” Gagnon said.
Despite the alarming projections, Gagnon says the research is ultimately meant to be empowering.
“The thing that gives me hope, and many of the people that work in this field, is that we can make a difference,” he said. “The amount of carbon dioxide we emit is really what controls our future, so in many ways this information can be empowering. It helps us understand what we have to do.”
The most impactful step, researchers say, is reducing CO2 emissions. But the Pacific Northwest is also emerging as a testing ground for carbon removal technology. Lower electricity costs in Washington state make it an attractive location for pilot projects aimed at extracting CO2 from ocean water and the atmosphere and storing it in materials like rock and cement.
Companies including Ebb Carbon, which is testing commercial marine CO2 removal, and Banyu Carbon, a University of Washington spinoff focused on low-energy carbon removal, are among those developing scalable solutions in the region. Tribal nations and government agencies are also engaged in monitoring and mitigation efforts.
“We have the capacity to do this, but we have to act really strongly, more than we have, and we have to do that today,” Gagnon said.
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