New "tissue clock" technique reconstructs sea turtle life histories from shell chemistry
MIAMI — Techniques developed to study the distant past—from dating ancient artifacts to reconstructing climate records in ice cores—are now being repurposed to better understand the lives of modern sea turtles. Using radiocarbon methods from archaeology, researchers show that sea turtle shell plates are biological time capsules that record signs of major environmental disturbances in the ocean.
A new study published in the journal Marine Biology, shows that scutes, the hard plates that make up a turtle's shell, grow continuously and preserve chemical signals that reflect environmental conditions over time. By analyzing these layers, scientists can determine where turtles have been foraging, what they were eating, and how marine environmental stress events affected them.
The research was led by Bethan Linscott , Ph.D., and Amy Wallace, Ph.D., in collaboration with researchers from the University of Florida, the University of Bristol, and Earth Sciences New Zealand.
Linscott is a research assistant professor of sea turtle conservation at the Robert K. Johnson Center for Marine Conservation at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science. She is an archaeological geochemist who specializes in isotopic methodologies to investigate the interactions between humans, animals, and their environments throughout history. Wallace is a faculty research assistant at the Hatfield Marine Science Center in Newport, Oregon, specializing in the aging, migration, and trophic dynamics of marine fishes and sea turtles.
Sea turtle scutes are made of keratin—the same material found in human hair and nails. Keratin grows in successive layers that capture chemical information about a turtle's diet and environment when the tissue forms. Scientists have long used stable isotope analysis of scutes to study turtle ecology, but the timescale represented by these layers has remained uncertain.
"Sea turtle shells grow continuously throughout their lives, and each layer preserves evidence of past environmental conditions," said Linscott. "By analyzing these sequential layers, we can reconstruct foraging patterns, diet, and environmental changes over time."
To determine how quickly the layers form, researchers analyzed shell samples from 24 stranded sea turtles—loggerheads (Caretta caretta) and green turtles (Chelonia mydas)—collected along the Florida coast between 2019 and 2022. The team removed small circular biopsies from the scutes and sliced them into ultra-thin sections approximately 50 microns thick.
Each layer was radiocarbon dated and compared with the mid-20th-century "bomb pulse," a spike from nuclear weapons testing that serves as an environmental tracer in the marine environment.
The researchers then used Bayesian age-depth modeling, a statistical approach commonly used in archaeology to date sediment layers to estimate how quickly the shell tissue accumulated.
The results showed that scute growth rates vary among turtles, but on average each 50-micron layer represents about seven to nine months of growth.
By reconstructing these timelines, the scientists identified synchronized slowdowns in shell growth across multiple turtles. These slowdowns coincided with major environmental disturbances in Florida waters, including harmful algal blooms known as "red tides" and large Sargassum seaweed events.
"These shells are effectively recording environmental stress in the ocean," Linscott said. "It's a bit like sea turtle forensics. We can use chemical fingerprints preserved in scutes to detect ecological shifts."
Understanding where sea turtles forage, how their diets change, and how environmental stress affects their growth can help scientists better protect these threatened marine species. Because sea turtles are long-lived and spend much of their lives in the open ocean, directly observing their life histories is often difficult.
"Our findings can help scientists better understand how marine ecosystems are changing and how species respond to those changes."
The study, titled "Bomb radiocarbon reveals keratin growth dynamics in loggerhead (Caretta caretta) and green (Chelonia mydas) turtles," was published in the journal Marine Biology, January 28, 2026.
Funding for the research was provided in part by the Florida RESTORE Act Centers of Excellence Research Grants Program (FLRACEP), Sub agreement No. 4710-1129-00-B awarded to Hannah Vander Zanden and Will Patterson III.
Co-authors include Amy A. Wallace, Archie Carr Center for Sea Turtle Research, University of Florida, and Oregon State University; Lorena Becerra-Valdivia, University of Bristol; Matt R. P. Harris, National Isotope Centre, Earth Sciences New Zealand; Alexandra L. Fireman and Jenna D. Bennett, Archie Carr Center for Sea Turtle Research, University of Florida; William F. Patterson III, Fisheries and Aquatic Sciences, University of Florida; and Hannah B. Vander Zanden, Archie Carr Center for Sea Turtle Research, University of Florida.
About the University of Miami and Rosenstiel School of Marine, Atmospheric and Earth Science
The University of Miami is a private research university and academic health system with a distinct geographic capacity to connect institutions, individuals, and ideas across the hemisphere and around the world. The University's vibrant academic community comprises 12 schools and colleges serving more than 19,000 undergraduate and graduate students in more than 180 majors and programs. Located within one of the most dynamic and multicultural cities in the world, the University is building new bridges across geographic, cultural, and intellectual borders, bringing a passion for scholarly excellence, a spirit of innovation, and a commitment to tackling the challenges facing our world. The University of Miami is a member of the prestigious Association of American Universities (AAU).
Founded in 1943, the Rosenstiel School of Marine, Atmospheric, and Earth Science is one of the world's premier research institutions in the continental United States. The school's basic and applied research programs seek to improve understanding and prediction of Earth's geological, oceanic, and atmospheric systems by focusing on four key pillars:
*Saving lives through better forecasting of extreme weather and seismic events.
*Feeding the world by developing sustainable wild fisheries and aquaculture programs.
*Unlocking ocean secrets through research on climate, weather, energy and medicine.
*Preserving marine species, including endangered sharks and other fish, as well as protecting and restoring threatened coral reefs. www.earth.miami.edu .
