While humans were busy bombing the Earth with atomic bombs in the second half of the 20th century, sea and land turtles around the world were living quietly (and very slowly). Unbeknownst to them, the legacy of the terrible explosions was etched deep into their shells.
The new research examined the shells of sea and land turtles found near atomic bomb test sites and nuclear waste landfills. Scientists discovered clear traces of anthropogenic uranium from nuclear fallout in the keratin layers of their shells.
Just like tree rings, the shells of these animals grow in layers that act as “environmental information storage”. This can be used as a tool to reconstruct the history of nuclear bomb explosions, the researchers explain in their new paper.
Scientists at the University of New Mexico and Los Alamos National Laboratory, the birthplace of the first atomic bomb, collected five shells from various hotspots linked to the use of nuclear bombs. Unusual traces of uranium in the shells of a green sea turtle from the Republic of the Marshall Islands, a desert turtle from southwestern Utah, a river turtle from the Savannah River Area in South Carolina, and a box turtle from the Oak Ridge Conservation Area in eastern Tennessee found.
Shells what nuclear events overlap
Some of the uranium traces in the shells closely coincide with nuclear events. The crust from the Oak Ridge Conservation Area contained a signature of uranium in growth rings between 1955 and 1962. These traces peaked in 1958, and this appears to be directly related to the release of highly enriched uranium into the air in the region.
The crust from the Marshall Islands is particularly noteworthy. This beautiful, remote group of islands served as the Pacific Test Site for the United States from 1946 to 1958 and witnessed nearly 67 nuclear tests that left an unwelcome legacy.
A nuclear test in the Marshall Islands in 1946.The green sea turtle shell used in this latest study was collected from the belly of a tiger shark caught near Enewetak Atoll in 1978, nearly 20 years after nuclear testing in the area ended. The turtle was relatively young and unlikely to have survived at the time of the explosion, but traces of uranium were still found in its shell.
The researchers suspect that the radionuclide evidence in its crust shows how cleanup activities on Coral Island are mobilizing ancient contaminated sediments. Alternatively, this may indicate that old pollution from the bombardment is still present in the atoll lagoon and reaches the tortoise shell through a diet of irritated seaweed and algae.
Shelled reptiles aren’t the only creatures that can be used to trace the history of atomic bombs. Coral skeletons and mollusk shells have also been used in the past. The eyes of the Greenland shark, one of the longest-living vertebrates, are also surprisingly effective.
But the researchers say sea and tortoises are particularly useful tools to piece together the history of nuclear activity on Earth. So they hope they can be used for further research into how atomic bombs are changing our planet.
The research was published in the journal PNAS Nexus.
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