A Toothy Summer in Charleston: Internship Reveals Rising Freshwater Exposure in Bottlenose Dolphins

Hannah Baker, a 2025 Ernest F. Hollings Scholarship student at the University of Michigan, spent her summer conducting research at the National Centers for Ocean Science (NCCOS) Hollings Marine Laboratory in Charleston, South Carolina. Her project focused on analyzing the teeth of Tamanend's bottlenose dolphins (*Tursiops erebennus*) to determine levels of freshwater exposure. The study utilized teeth collected from previously stranded dolphins. Baker cut the teeth in half using a saw and scanned them with scanning electron microscopy energy dispersive x-ray spectroscopy (SEM-EDS) to measure barium incorporation. Barium was selected as the biomarker because it is naturally found in freshwater and is incorporated into the teeth throughout a dolphin's lifespan, serving as a record of diet, habitat, and environmental conditions. The research indicates that Tamanend's bottlenose dolphins in the Charleston Estuarine System have faced increased exposure to freshwater. This shift is significant because freshwater exposure is harmful to these marine mammals, often resulting in skin lesions and other maladies. During the internship, Baker scanned approximately 30 bottlenose dolphin teeth and one pygmy sperm whale (*Kogia breviceps*) tooth. Beyond the laboratory analysis, the internship provided Baker with hands-on experience in marine conservation. Highlights included assisting with photo identification of dolphins in the Kiawah River, attending necropsies of loggerhead sea turtles, bottlenose dolphins, and dwarf sperm whales, and touring the Nancy Foster Research Vessel with a NOAA Corps officer. The work contributes to ongoing efforts to understand how changing environmental conditions affect marine mammal health and habitat usage in the region. #NexSouk #AIForGood #EthicalAI #MarineConservation #DolphinHealth **References** 1. NOAA Office of Education. "A toothy summer in Charleston: My internship studying barium in bottlenose dolphin teeth to determine freshwater exposure." https://www.noaa.gov/office-education/hollings-scholarship/stories/toothy-summer-in-charleston-my-internship-studying-barium-in-bottlenose-dolphin-teeth-to-determine