Beneath the ocean floor, in layers of ancient sediment, lie microscopic storytellers, marine organisms called foraminifera, or “forams” for short. These single-celled protists, no larger than a grain of sand, hold within their calcium carbonate shells a detailed record of Earth’s climate history. But, rising carbon emissions and ocean acidification may be erasing their story before scientists can read it.
At the University of South Florida’s College of Marine Science in St. Petersburg, oceanographer Callie Crawford is at the forefront of a research effort to understand how ocean acidification, a direct result of human-caused climate change, is ultimately threatening the ocean’s ability to remember.
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Crawford, an early-career scientist with two degrees in marine science and a minor in chemistry, works in the Rafter Ocean, which is run by Patrick Rafter and Climate Lab. She and her team collaborate with other scientists and labs to study sediment cores pulled from the ocean floor, containing layers dating back tens of thousands of years; records that, when combined with research from other labs, help reconstruct Earth’s past climate.
Inside these cores, scientists find foraminifera shells that preserve the chemical conditions of the water they lived in, clues that help reconstruct ancient ocean temperatures, carbon levels, and other vital environmental data.
This field of study, called paleoceanography, is key to building climate models that help us predict the planet’s future.
Ocean Acidification Is Disrupting Paleoceanographer’s Tools
But there’s a problem: as carbon dioxide from the atmosphere dissolves into the ocean, it reacts with water to form carbonic acid, which lowers the ocean’s pH. This process, known as ocean acidification, breaks down the calcium carbonate that foraminifera use to build their shells.
“The more acidic the ocean becomes, the harder it is for these organisms to survive and for their shells to be preserved in the sediment record,” Crawford explains. “That means we’re losing one of the best tools we have to understand how Earth’s climate has changed over time.”
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“This work lets us piece together what the ocean looked like thousands of years ago,” Crawford says. “And by doing that, we can better predict what’s coming next.”
Though ocean acidification is a global issue, the research being done in St. Petersburg is a vital piece of the climate puzzle.
As ocean acidification makes Crawford’s research harder, the future of the ocean and what we know about its past becomes a much more challenging puzzle to piece together. Nonetheless, Crawford and her team persevere, as they aim to tell all the stories the foraminifera shells can tell.
Jorden Pompey, San Pedro Gazette, 27 June 2025. Full article.
