A Warning from the Pacific: North America’s Waters Are Becoming Too Acidic for Marine Life
- Ritambhara K
- 4 days ago
- 3 min read
Credit:Robert Evans, bobevansphotography.com
The waters around North America may soon become hostile to key marine species if acidification in the Northeastern Pacific continues at its current pace, a new study warns.
Earth’s oceans have grown about 30% more acidic since the Industrial Revolution began over two centuries ago. As acidity rises, marine chemistry shifts and essential minerals disappear—minerals that corals, clams, and other calcifying organisms rely on to build their shells and skeletons. The Northeastern Pacific is naturally more acidic than many other ocean regions, raising urgent questions about how much and how quickly its chemistry will deteriorate in the coming decades.
A study published November 13 in Nature Communications reveals that the region’s already acidic baseline makes it far more sensitive to the additional carbon dioxide generated by human activities. By analyzing coral skeletons from the past century, scientists discovered that CO₂ has been accumulating in coastal waters faster than in the atmosphere, accelerating acidification at an alarming rate.
“This is part of a critical set of records showing how the world has changed during the human era,” said senior author Alex Gagnon, associate professor of oceanography at the University of Washington.“The findings affect not just marine ecosystems, but all the people who depend on them,” added lead author Mary Margaret Stoll, a UW doctoral student.
Why the Ocean Is Acidifying Faster Here
When carbon dioxide dissolves in seawater, it forms carbonic acid, releasing hydrogen and bicarbonate ions that lower pH. Along North America’s west coast, the California Current sweeps cold water southward. Combined with strong winds, this creates ideal conditions for upwelling—a process in which deep, CO₂-rich water rises to the surface.
As organic matter sinks and decomposes on the seafloor, it releases even more carbon dioxide. Upwelling then brings this CO₂ back to the upper layers, intensifying acidity in both surface and subsurface waters.
These natural swings make it difficult for researchers to distinguish human-driven acidification from background variability—until now.
A Century of Clues Hidden in Coral Skeletons
Corals absorb elements from seawater as they grow, creating chemical archives within their skeletons. In the Northeastern Pacific, the small but vibrant orange cup coral provides an invaluable record of changing ocean conditions. Gagnon’s lab had already been studying these corals when researchers became intrigued by historical specimens.
Beginning in 2020, they gathered 54 coral samples collected between 1888 and 1932 from the Smithsonian and other museums across the U.S. and Canada, focusing on specimens from the Salish Sea and the broader west coast.
Using handwritten logbook notes, the team located the original collection sites and returned over 100 years later to gather new samples. By measuring boron ratios—a chemical fingerprint of seawater acidity—the researchers reconstructed a timeline of CO₂ changes from 1888 to 2020.
The results were striking:
CO₂ levels in seawater rose faster than atmospheric CO₂.
Acidification was strongest 100–200 meters below the surface, challenging the common view that ocean acidification is primarily a surface phenomenon.
“No one has acidity measurements older than a few decades,” Gagnon said. “We had to dig back in time and decode the chemical signals the corals preserved.”
A Troubling Amplification Effect
The study shows that the Northeastern Pacific’s natural chemistry amplifies the effects of human-generated CO₂—and this amplification will only intensify as emissions rise.
Using climate models, researchers simulated worst-case future conditions. The projections were stark: dramatic chemical changes that could reshape ecosystems central to the cultural, commercial, and recreational life of the region.
“The changes were really dramatic,” Stoll said. “The Salish Sea relies deeply on the health of these ecosystems.”A Narrow Window for Action
Despite the severity of the findings, the researchers insist that the situation is not hopeless.
“This is no time for nihilism. The ocean is not destroyed,” Gagnon emphasized. “As major emitters, we have the power to change our emissions and influence the ocean’s future.”
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Studying fast-changing regions like the Northeastern Pacific can also provide an early preview of what the rest of the world’s oceans may face in the coming decades.
“This area is at the leading edge of ocean acidification impacts,” Stoll said. “It offers a window into the future—one we need to pay close attention to.”
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