Veronica Padilla Vriesman ’17, an assistant professor of geosciences at Oberlin College, is uncovering how shells tell the story of climates past, present, and future.
Inside the Quaternary Invertebrate Paleo Lab where Veronica Padilla Vriesman ’17 works at Oberlin College, the white-tailed deer and tractor trailers of small-town Ohio are nowhere to be found. Plastic baggies full of wedge-shaped aquatic mollusks from the Pacific Coast litter the shelves. A microscope sits on a lab bench, surrounded by specimens of pearlescent mussels. In the back, shells overflow from a cardboard box.
A paleontologist and marine scientist, Vriesman’s research focuses on how changes in the ocean’s temperature, acidity, and other factors — either natural or human- induced — affect the composition and structure of shells. In doing so, she hopes to understand what those changes mean for the overall health of coastal environments.
Vriesman is not alone in her fascination with shells: “Shells have this long-standing relationship with humans because humans have eaten shell[fish] and collected or used shells for tools or jewelry for more than 10,000 years,” she explains. She has become especially interested in California mussels, which, beyond being culturally important, play a critical role in coastal ecosystems, supporting the well-being of hundreds of other coastal species by filtering water, providing shelter, and minimizing erosion.
These mussels grow their shells through a process called calcification, during which they produce proteins and minerals. These minerals form bands, like how tree trunks have growth rings, but they don’t only show the organism’s age. The composition of the minerals also acts like a tiny time capsule that captures features of the environment in which the shell grew. “We can get estimates of conditions like temperature and acidity, but then we can also look at qualities and characteristics of the shell: its shape, its size, its pattern, how fast the shell was growing, how happy [the organism] was in its environment,” Vriesman says.
Vriesman started researching historic shells and the information they held when she was a graduate student at University of California, Davis, where she graduated with her PhD in 2022. “I was interested in reconstructing past climates,” she explains. She wanted to look at shells from the past 12,000 years to assess previous ocean conditions to build a better understanding of how ocean climates once looked — on scales as large as millennia and as short as seasons — and about how mussels responded to those climates.
But to understand shells of the past, Vriesman first had to learn more about the shells of the present. Using tools like microscopes and chemical analyses, she examined California mussel shells from the early 2000s and 2020s and compared them to already-recorded ocean conditions to develop a better baseline understanding of shell composition so she could use that knowledge to study older shells.
Some of her findings were quite surprising. Over those two decades — which, according to Vriesman, “is really geologically fast” — the minerals in mussels’ shells had become much more disarrayed, showing that their composition and growth was changing rapidly. “It was an unexpected result that is now making up a central aspect of my research,” Vriesman says.
Now, she’s curious about what this rapid change means for the mussels and their ability to thrive in oceans with increasing temperatures and acidity. “Are they trying to calcify faster, and they’re adapting? Or are they really being negatively impacted, and this is a sign that they aren’t doing well?” she says. Vriesman is interested in figuring these questions out: “It’ll involve looking at modern shells but also looking into archival records to see if we’ve seen this before and it bounces back or if this variability has never appeared.”
But California mussels aren’t the only species that can provide some of these answers. Since Vriesman joined Oberlin’s geosciences faculty two years ago, much of her research time has been spent developing her lab and recruiting students, who are already starting to look into different types of shells — gathered from the coasts of the Pacific to the Atlantic and even to the Great Lakes. “The plan is to study many ecologically and economically important shells to see how a variety of species are responding and to get a big-picture understanding of what we’re doing to coastal ecosystems,” she says. “Mussels are just one example of many species’ stories.”
Vriesman never planned to go into science, but her experiences in Colgate geology classrooms — including one where she got to hold a multimillion-year-old seashell — motivated her to pursue research.