Plastic pollution is creating an "evolutionary trap" for young sea turtles because they "eat anything", according to a new study.
Research led by the University of Exeter found plastic in the stomachs of small juvenile turtles along both the east (Pacific) and west (Indian Ocean) coasts of Australia.
The animals travel on currents and start out life in the open ocean after hatching on beaches.
But many young turtles swallow plastic as the currents accumulate vast quantities of waste.
Dr Emily Duncan, of the Centre for Ecology and Conservation on Exeter's Penryn Campus in Cornwall, said: "Juvenile turtles have evolved to develop in the open ocean, where predators are relatively scarce.
"However, our results suggest that this evolved behaviour now leads them into a trap - bringing them into highly polluted areas such as the Great Pacific Garbage Patch.
"Juvenile sea turtles generally have no specialised diet - they eat anything, and our study suggests this includes plastic."
She added: "We don't yet know what impact ingesting plastic has on juvenile turtles, but any losses at these early stages of life could have a significant impact on population levels."
The study examined juvenile sea turtles that either washed up or were accidentally caught by fishers on the Australian coasts.
It included a total of 121 sea turtles from five of the world's seven species: green, loggerhead, hawksbill, olive ridley and flatback.
Data revealed that the proportion of turtles containing plastic was much higher on the Pacific coast, with 86% of loggerheads, 83% of greens, 80% of flatbacks and 29% of olive ridleys.
Comparatively, 28% of flatbacks, 21% of loggerheads and 9% of green turtles contained plastic on the Indian Ocean coast.
The researchers found that plastic in the Pacific turtles was mostly hard fragments, which could come from a vast range of products used by humans, while Indian Ocean plastics were mostly fibres - possibly from fishing ropes or nets.
The polymers most commonly ingested by turtles in both oceans were polyethylene and polypropylene.
Dr Duncan said: "These polymers are so widely used in plastic products that it's impossible to pin down the likely sources of the fragments we found.
"Hatchlings generally contained fragments up to about 5mm to 10mm in length, and particle sizes went up along with the size of the turtles.
"The next stage of our research is to find out if and how plastic ingestion affects the health and survival of these turtles.
"This will require close collaboration with researchers and veterinarians around the world."
Sea Life Trust and the National Geographic Society funded the research, which was published in the journal Frontiers in Marine Science.
The research team also included Murdoch University, the Department of Environment and Science (Queensland) and the Department of Biodiversity Conservation and Attractions (Western Australia).
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