Ocean acidification is sometimes described as climate change’s evil twin. The ocean absorbs carbon dioxide from fossil fuel emissions, causing the water to become more corrosive.
“Ocean acidification is already impacting the growth of oysters, clams, plankton, which in turn are important food sources for salmon, seabirds and other marine organisms,” said Mary Margaret Stoll, who just received her PhD from the University of Washington and is the lead author on a new study of ocean acidification, published in the journal Nature Communications.
Stoll said her love of chemistry, physics and biology led to a fascination with ocean acidification. She joined a project that was looking broadly at how ocean acidification is unfolding in the Salish Sea, which borders British Columbia and Washington state. The wind and ocean currents here cause regular upwellings of carbon rich waters from the deep, influenced by the powerful California Current that causes similar conditions off that coast.
To better understand the region’s chemical trajectory, Stoll got to work with a set of artifacts that were collected 130 years ago: the skeletons of native orange cup corals. Naturalists aboard the USS Albatross — a tall ship on a mission to survey halibut for the federal government — had the foresight to keep them.
Stoll said she’s still amazed that this un-commissioned collection was available to her in the archives of the Smithsonian.
“These corals were incredibly well preserved, and there was so much information attached to them as well — about the depths of collection and where they were collected, and when they were collected, how they were cleaned and preserved,” Stoll said.
Stoll and her team painstakingly practiced their knife skills before slicing tiny samples from the 130-year-old specimens in their lab at the University of Washington. Then, they followed the path that the USS Albatross had sailed through the Salish Sea to get modern coral samples that matched those locations, depths and species.
Cruising along in the UW research vessel RV Rachel Carson in 2020, they used a large net that pulled huge swaths of mud and rocks up from the sea floor along with the samples they were seeking.
“Alex and I spent hours kind of picking our way through these piles, looking for little flashes of orange — these tiny orange cup corals that we were looking for,” Stoll said.
Alex Gagnon, a University of Washington professor who co-authored the paper, said these corals gave them key information about the present that they could compare to the data stored in the corals from the past.
“You can read that information much like an ice core or tree rings,” Gagnon said. “If you know when the coral lived, and you have the right tools.”
They sent the samples to their collaborators in at the University of St Andrews in Scotland. Their review provided isotope measurements and analysis that the team also checked against computer models developed by colleagues at Princeton University and NOAA’s Pacific Marine Environmental Laboratory.
Stark findings
The findings shocked them. Their research showed that the Salish Sea has become 40% more acidic than other parts of the ocean in the 200 years since the start of the industrial revolution. This much faster pace is due to the constant deep upwelling off the west coast — the carbon brought up from the depths contains carbon-rich materials from decomposed sea life. That higher baseline level of carbon already in the water amplifies the uptake of carbon emissions and causes the faster pace of acidification here — and likely in a multitude of the world’s oceans that have similar upwelling.
Gagnon, who has decades of research behind him, said this is perhaps the most intellectually rewarding project he has ever done. It brought maritime history together with so many aspects of what make oceanography and science fun. They got to work with "really cool instruments, like mass spectrometers,” he said.
“And to come out with a really conclusive result is also incredibly satisfying,” he said.
The severity of those results surprised Gagnon — and led him to start researching ways to remove carbon from the atmosphere. He's now the co-founder and CEO of a carbon removal company called Banyu Carbon that he said uses less energy than most. It's a pursuit he still feels somewhat skeptical about, because tinkering with Mother Nature is not something he feels should be taken lightly.
“The fact that we're at this point where carbon dioxide removal has to be a significant part of our path forward is just a reflection that we haven't done the steep emissions reductions that we need to do," Gagnon said.
He said that along with carbon removal, those emissions reductions need to happen in less than a decade from now — by the 2030s — in order to reduce the dangers of a warming planet and keep local waters healthy.
