Study: Sea Turtles Found to Be Ingesting Large Amounts of Plastic

A green sea turtle swimming in the waters off Redang island in Malaysia on June 28, 2020. Mohd Rasfan/AFP via Getty Images

Small juvenile marine turtles from several species are ingesting large quantities of plastic, a form of pollution that affects more than just turtles, researchers from the United Kingdom and Australia have found.

The scientists studied 121 juvenile turtles, including greens, loggerheads, flatbacks, olive ridleys, and hawksbills. The specimens, which were either stranded or bycaught (the portion of a commercial catch that isn’t caught intentionally), came from either the Indian Ocean near Western Australia or the Pacific Ocean near Queensland, Australia.

“It is difficult to study this [life] stage, as most species [develop] in open ocean areas and are hard to sample,” said Emily Duncan, a researcher at the University of Exeter and lead author of the paper.

She and her colleagues found plastic in the gastrointestinal tracts of many turtles, although with significant variation across species and oceans. Green turtles from the Pacific Ocean contained an average of 18 pieces of plastic, while flatback turtles from the Indian Ocean contained an average of 3 pieces. One green turtle from the Indian Ocean contained 343 pieces of plastic.

Although scientists had previously found plastic in the bladders of post-hatchling turtles, the team didn’t find any plastics in the bladder or other locations outside the GI tract.

“Further research needs to explore whether smaller [microplastics] can move from the GI tract into other areas of the body,” Duncan said.

While the sample could be considered somewhat small, Duncan emphasized the uniqueness and importance of her group’s data.

“This life stage is very cryptic and difficult to study due to the habitats that they inhabit, so any studies that can report any information on this life stage [are] very valuable,” she said.

Post-hatchling turtles from the Pacific Ocean were far more likely to have ingested plastic than those from the Indian Ocean. For example, while 83 percent of green turtles from the Pacific had ingested plastic, just 9 percent of green turtles from the Indian Ocean had ingested it.

“The sources of plastic and movement within the different oceans and [their] overlap could play a possible role in levels of ingestion,” Duncan said.

A 2017 Nature article that modeled plastic outflow from rivers to oceans estimated that 1.15 million to 2.41 million tons of plastic reach the world’s oceans via riverine systems every year, with a particularly heavy contribution from river systems in Asia.

China is the top source of plastic in the world’s oceans, generating over a quarter of global mismanaged plastic waste, according to a 2015 article in Science.

Writing in a 2020 Science Advances article, other researchers have pegged the United States as the top global producer of plastic waste when one accounts for plastic waste exported from the United States to other countries for recycling.

China officially banned the import of most plastic waste in 2018 as part of its ‘National Sword’ policy.

“Plastic is an essential material and does not belong in the environment,” the Plastics Industry Association told The Epoch Times. “Most of the plastics that find their way to the ocean are used consumer products (e.g., bottles, caps, containers, etc.) that have been carelessly discarded, the vast majority of which comes from rivers located in Asia. These nations must invest in modern recycling infrastructure to manage all waste, not just plastic.”

Other research has linked plastic ingestion to worse outcomes for baby turtles. A 2021 study of newborn turtles that washed ashore dead on Florida’s central Atlantic coast showed that animals with more plastic in their bodies were in worse physical condition.

Duncan’s own past research has suggested that microplastics, tiny plastic particles ranging from the millimeter to the nanometer scale that are produced through the breakdown of larger pieces of plastic, are ubiquitous in turtles. She and her coauthors detected microplastics in all 102 marine turtles that they sampled, spanning seven species across the Atlantic Ocean, the Pacific Ocean, and the Mediterranean.

Turtles are among the many life forms, including humans, for which plastics are endocrine disruptors, or chemicals that interfere with the hormonal system. Indeed, researchers studying the impact of plastics on turtles have done so in part to understand the potential impact of synthetic particles on a variety of organisms, including humans.

In turtles, bisphenol A, a chemical commonly used in water bottles and other plastic goods, has been tied to abnormal sexual development. According to a Science Daily summary of one 2015 study, “BPA—which mimics estrogen—can alter a turtle’s reproductive system and disrupts sexual differentiation.”

In humans, plastics and other endocrine disruptors have been linked to obesity, early puberty in young girls, cancer, altered neurodevelopment, and both male and female reproductive disorders.

Follow Nathan Worcester on Twitter: @nnworcester