The shell of a sea turtle holds the story of its life. It is made up of keratin shields that grow in layers, similar to annual rings. Each layer captures chemical signals from the environment.
Scientists from the University of Florida have developed a method for reading this record. They used radiocarbon dating and the 'bomb pulse' — traces of nuclear tests from the mid-20th century that have been preserved in the ocean. These markers can be used to reconstruct the chronology of a turtle's life with an accuracy of several months.
The study showed that shell growth slows during periods of ecological stress. Several turtles exhibited simultaneous growth slowdowns during red tides and sargassum blooms. This indicates common threats rather than individual characteristics. Young turtles in the open ocean grow more slowly than their coastal counterparts. Females slow their growth during breeding seasons.
The shell not only protects the turtle but also acts as an onboard recorder. It captures where the animal lived, what it ate, and when it faced danger. The method can also be applied to other animals with layered tissues. For the conservation of marine species, it is important not only to know where they currently live but also to understand what they have gone through. The shell tells this story layer by layer.
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