In a cabinet at Charleston’s Hollings Marine Laboratory, 30 years of dolphin teeth hold clues to where the animals have lived. This summer, University of Michigan student Hannah Baker used some of those samples to explore whether a natural element in teeth can reveal how much freshwater Tamanend’s bottlenose dolphins have encountered.
The dolphins live in the Charleston Estuarine System, where increased freshwater exposure can harm their skin and lead to lesions and other health problems. Researchers need ways to understand that exposure over time. A dolphin’s teeth may help: as they grow, they take in chemicals that can preserve information about the animal’s diet, habitat and environmental conditions.
Baker, a 2025 Ernest F. Hollings Scholarship student studying Earth and Environmental Sciences, focused on barium. The element occurs naturally in freshwater, making it a possible marker of freshwater exposure in dolphin teeth. She worked at the National Centers for Coastal Ocean Science’s Hollings Marine Laboratory, scanning teeth that had previously been collected from stranded animals.
To measure barium, Baker used scanning electron microscopy with energy-dispersive X-ray spectroscopy, a method that scans a sample and identifies elements in it. She cut the teeth in half and scanned a section. Over the summer, she examined about 30 bottlenose dolphin teeth and one tooth from a pygmy sperm whale, a small whale species also known as Kogia breviceps.
The project offers a way to investigate a threat that is not always easy to track from a single observation. Because teeth record chemical information as they form, they could help scientists study environmental exposure across an animal’s life. The source does not report a final finding about barium levels, but the work tests whether this natural chemical signature can help researchers learn more about freshwater conditions facing Charleston’s dolphins.
For Baker, the internship also opened a door into marine science. She had not worked with marine mammal specimens before, and said using dolphin teeth for conservation was a highlight. Outside the lab, she helped identify dolphins from photographs in the Kiawah River, attended examinations of a loggerhead sea turtle, a bottlenose dolphin and a dwarf sperm whale, and toured the research vessel Nancy Foster with a NOAA Corps officer.
The summer gave Baker hands-on experience with both laboratory research and field-based conservation work. As she continues her studies at the University of Michigan, the tooth samples remain a starting point for a larger question: whether the chemistry held in a dolphin’s teeth can help scientists trace freshwater exposure and better understand the conditions these coastal animals face.