Tortoise and turtle shells can be used to study nuclear contamination, scientists have found.
Just as tree rings can provide snapshots of the Earth’s climate, and ice cores can give us information on past temperature, researchers found that the layers of shells can be used as a time stamp of periods with nuclear fallout.
Research published in the scientific journal PNAS Nexus investigates how uranium builds up in the outer shells of chelonians, the order of reptiles that includes tortoises and turtles.
“When we consider the legacies of 20th century nuclear deployment, testing, and production, we must now also consider chelonians and their lived experience in areas where these activities occurred,” the research stated.
The researchers focused on turtles and tortoises from areas that have seen nuclear contamination, and measured the uranium that was present in the scute, the bony outer shell that is usually made of keratin. Each layer of shell equates to one year of its life, and so can reveal what happened in the tortoise’s surrounding environment.
Five different chelonians from natural history collections were studied. One of these came from Enewetak Atoll, and was collected in 1978. Enewetak Atoll and its neighbour, Bikini Atoll, in the Pacific, were the site of 67 nuclear tests, with Enewetak the site of 43 of these. Though the sea turtle was probably not alive during the time of the testing, researchers still found uranium contamination in the turtle 20 years after testing ended.
However, consumption of uranium-contaminated algae, or other legacy contamination present in the atoll, may have contributed to the presence of uranium in that turtle.
Researchers also looked at an eastern box turtle from Oak Ridge, Tennessee, in the US. Oak Ridge is the site of a nuclear facility that has produced and processed uranium since 1943. The turtle that was studied from there was collected in 1962 and may have bioaccumulated radionuclides, or radioactive materials, from uranium waste products in the area.
The researchers were able to identify uranium isotopic composition across the scute from these turtles.
The research supports the idea that these animals can bioaccumulate human-made radionuclides, or from the environment. It also supports the idea that these animals, which often live a long time, can record information about human activity with nuclear landscapes over a long period.
“We anticipate that combining analyses of historically collected and modern specimens will significantly expand our environmental monitoring abilities as they relate to ongoing nuclear contamination questions,” the study said.
