Scientists are finding microplastics everywhere they look for them. A new study finds these tiny plastic particles in sea turtle nests on a remote Malaysian island. Researchers warn that microplastics could alter nest temperatures, potentially skewing the sex ratio of incubating turtles that could further endanger species already facing significant challenges.
Up to 1,700 green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) sea turtles make their way to Chagar Hutang Turtle Sanctuary on Malaysia’s Redang Island each year. They arrive at the beach where they hatched to create a nest and lay their own eggs that then form the next generation of sea turtles. But often, those nests are not just made of sand and stones, the study finds.
Researchers recorded an average of roughly 2,000 pieces of microplastics per kilogram (2.2 pounds) of dry sand. There were tiny bits of plastic in every nest they examined and throughout the nests at every depth.
The findings in Malaysia add to the body of evidence that microplastics are in sea turtle nests worldwide, including the Gulf of Mexico, Türkiye (Turkey) and the Galápagos. Previous studies have even found microplastics inside the eggs of unhatched, nonviable loggerhead turtles (Caretta caretta) in Florida, U.S.
The most common microplastic found in the Malaysian study was black fibers, most likely from fishing nets, food packaging and textiles, the authors write.
Some studies show microplastic can change the physical properties of sand, making it warmer and less permeable to water. Plastic holds heat longer than sand, potentially making the nests warmer for longer, the authors write.
Warmer nests are concerning because the sex ratio of incubating turtles is highly dependent on the ambient temperature. Warmer temperatures result in more female hatchlings and cooler temperatures, more males. Research suggests that climate change may already be putting a thumb on the scale for female turtles. A 2018 study, for example, found more than 99% of green sea turtles that hatched on warmer beaches near the northern Great Barrier Reef (GBR) in Australia were female, while about 67% of the turtles originating from the cooler southern GBR nesting beaches were female.
The new study’s authors warn that microplastics are potentially adding to an existing sex ratio imbalance that can make threatened species even more vulnerable. Green sea turtles are considered endangered and hawksbills are critically endangered.
“Protecting sea turtles is vital not only for maintaining marine ecosystems but also for supporting local economies, preserving biodiversity, and safeguarding Malaysia’s cultural heritage,” the authors write.
This article by Bobby Bascomb was first published by Mongabay.com on 26 March 2025. Lead Image: A green sea turtle by Mongabay’s Rhett A. Butler.
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