Widespread plastic pollution creating a deadly ‘evolutionary trap’ for young sea turtles

EXETER, United Kingdom — Widespread plastic pollution may be creating a deadly trap for sea turtles, a new study warns. Research led by a team of University of Exeter scientists discovered plastic inside small juvenile turtles along both the east (Pacific) and west (Indian Ocean) coasts of Australia.

After hatching on beaches, sea turtles travel on currents and spend their early years in the open ocean. However, these currents now accumulate vast quantities of plastic particles and – feeding near the surface – many young turtles swallow them.

“Juvenile turtles have evolved to develop in the open ocean, where predators are relatively scarce,” says Dr. Emily Duncan from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in a university release.

Turtles with microplastics in stomach
Some of the plastic fragments found in turtle during the study.

“However, our results suggest that this evolved behavior now leads them into a ‘trap’ – bringing them into highly polluted areas such as the Great Pacific Garbage Patch,” Duncan continues. “Juvenile sea turtles generally have no specialized diet – they eat anything, and our study suggests this includes plastic. 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.”

Pollution worse in the Pacific Ocean

Researchers examined juvenile sea turtles – from hatchlings to a shell measurement of up to 20 inches – that either washed up or were accidentally caught by fishers on the Australian coasts. In total, the study included 121 sea turtles from five of the world’s seven species: green, loggerhead, hawksbill, olive ridley, and flatback.

The proportion of turtles containing plastic was far higher on the Pacific coast. Specifically, scientists found plastic particles in 86 percent of loggerheads, 83 percent of greens, 80 percent of flatbacks, and 29 percent of olive ridleys.

On the Indian Ocean coast, 28 percent of flatbacks, 21 percent of loggerheads, and nine percent of green turtles contained plastic, according to the findings published in the journal Frontiers in Marine Science.

Different plastics in different oceans

Plastic in the Pacific turtles was mostly hard fragments, which could come from a huge range of products used by humans. Meanwhile, Indian Ocean plastics were mostly fibers – possibly from fishing ropes or nets. The polymers most commonly ingested by turtles in both oceans were polyethylene and polypropylene.

“These polymers are so widely used in plastic products that it’s impossible to pin down the likely sources of the fragments we found,” says Dr. Duncan. “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,” Duncan concludes. “This will require close collaboration with researchers and veterinarians around the world.”

Plastic pollution has become one of the most pressing threats to marine wildlife. Estimates show that more than 700 marine species, from blue whales to small barnacles, have had interactions with plastics in the oceans. Scientists warn that plastics now make up 80 percent of all marine debris and are literally everywhere, from surface waters to deep-sea sediments.

South West News Service writer Stephen Beech contributed to this report.