Ocean Acidification

The waters of Puget Sound are more susceptible to ocean acidification and sliding faster into dangerous territory for its marine wildlife than other places around the world, a new study shows.

Should the trend continue, our marine wildlife and fisheries will likely suffer greatly years or decades earlier than previously anticipated, said Alex Gagnon, a chemical oceanographer with the University of Washington.

“This sounds pretty bad,” Gagnon wrote in an email. “And it is.”

Gagnon and a team of colleagues from UW published their novel study earlier this month, outlining their findings and serving as a new warning for the potentially catastrophic risk posed by climate change. They leaned on a series of chemical analyses but also a bit of detective work, delving further into the past than those who preceded them.

Put simply, as our oceans absorb increasing amounts of carbon dioxide, a greenhouse gas produced as we burn fossil fuels, their chemistry becomes more corrosive. This acidification has accelerated since the start of the Industrial Revolution. The larger our population and emissions grew, the more carbon dioxide we pumped into the atmosphere. The ocean absorbs about a quarter of the emissions humans generate.

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Now the world sits on a major precipice.

Not only is the accumulation of these greenhouse gases dangerously warming our atmosphere, it’s also pushing our ocean chemistry lower and lower on the pH scale. Already, the world’s oceans are about 30% more acidic than they were 200 years ago, according to a release from UW announcing the study.

Older, deeper waters tend to be more acidic, Gagnon said. This is because organic matter like dead fish and plants sink, and as they decompose or are eaten by microscopic organisms, they release carbon dioxide, turning the water more corrosive.

Already, Pacific waters up and down the North American coast are more acidic than those of most other places in the world, Gagnon said. This is due to a combination of wind patterns, undersea topography (known as bathymetry) and other factors, which churn up those deep and acidic waters and bring them closer to the surface. 

The phenomenon is even more pronounced throughout the Salish Sea thanks to the large number of rivers emptying into the water, which churns the mix even more, Gagnon said.

For years, the question was whether naturally high acidity throughout the Salish Sea (and the Pacific Coast, more broadly) would guard the waters against intensifying ocean acidification, Gagnon said. Or would it worsen the problem?

These orange cup corals live and grow throughout the waters of Puget Sound and along the Pacific Coast. This species is among those sensitive to ocean acidification, which is occurring more rapidly in the Pacific Northwest than most other places on earth. (Bob Evans)

The answer, he said, could be found in the brightly colored cup corals living throughout these waters. The scientists grew coral samples in their own lab, raising and lowering levels of acidity in the water.

The process also works in reverse, Gagnon said. They can use the corals to determine the acidity of the water in which they live. At best, though, most coral samples available are only a few decades old. They don’t date far back enough to make big-picture generalizations about human-caused climate change.

But his team knew where to find some old samples. 

The USS Albatross, the first vessel built and dedicated for marine research, sailed these waters before the turn of the 20th century, collecting coral samples along the way.

The scientists examined some of these samples, dating as far back as 1888, from the Smithsonian Museum, alongside samples from other labs and museums across the country and in Canada, Gagnon said.

They found that carbon dioxide levels in the Salish Sea and along the Pacific Coast rose faster than did levels of the greenhouse gas in the atmosphere during that same time frame, Gagnon said. And they published the study this month in Nature Communications. 

Basically, this confirmed scientists’ fears, Gagnon said. Conditions that make our regional waters more acidic than normal are compounding the effects of ocean acidification. So as these conditions worsen across the world, our waters will become an increasingly hostile environment to its native species.

Ocean acidification can bleach and kill coral reefs, increase the number of toxic algae blooms and hamper the ability of oysters, mussels and crabs to form their proactive shells. It can kill plankton and other tiny creatures forming the base of the underwater food chains, and these effects will ripple throughout the ecosystem and into our communities.

“The Salish Sea is a region with a lot of cultural, commercial and recreational ties to marine organisms that are all rooted in the health of these ecosystems,” Mary Margaret Stoll, a doctoral student in oceanography at UW and a lead author of the study, said in a release. 

As we continue to pump carbon dioxide into the atmosphere, levels of the gas within the Salish Sea and other Pacific Ocean waters will continue to climb higher and faster than levels in the rest of the world, Gagnon said. Major problems will emerge for the environment and our fisheries years or decades earlier than we previously expected.

But when precisely? 

In many ways, Gagnon said, that’s up to us.

Humanity has already failed to curb emissions enough to limit global warming to 1.5 degrees Celsius, scientists warned this fall. Beyond that threshold, we expect devastating consequences across the planet, like extreme weather, record temperatures, invasive species and ocean acidification.

But, Gagnon said, we have been able to reduce our emissions significantly in recent years. So we have the power to cut them further in the future by transitioning away from fossil fuels even more aggressively.

We have the power to slow this ocean acidification process, he said. We just have to use it.

Conrad Swanson, The Seattle Times, 20 November 2025. Article.