A new study led by the University of Exeter suggests that the unchecked plastic pollution in the ocean is leading sea turtles into an evolutionary trap.
This comes after researchers found a variety of plastic fragments inside small juvenile turtles that are swimming across both sides of Australia: the Pacific Ocean on the east and the Indian Ocean on the west. Furthermore, researchers are looking to conduct further studies to better understand the impact of plastic pollution on the new generation of sea turtles. The team included members from Murdoch University.
Results of the study are published in the latest Frontiers in Marine Science, August 2, in the article titled "Plastic Pollution and Small Juvenile Marine Turtles: a Potential Evolutionary Trap."
This picture taken on January 7, 2016 shows Olive Ridley sea turtle hatchlings inside a plastic water basin before being released at a beach in Morong, Bataan, 80 kilometers west of Manila. Hundreds of tiny turtle hatchlings emerge above a Philippine beach at night and immediately look to the sea, hoping to beat huge odds and start a remarkable trans-oceanic journey lasting decades.
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The Life of Juvenile Sea Turtles
Sea turtles are highly migratory animals, taking decades to be sexually matured for reproduction and usually travelling thousands of miles before finding a breeding site. Females mate at sea and return to land to start laying their eggs before leaving again. After laying eggs, they refill the dug nest with sand and camouflaging it by smoothening the location or covering it with vegetation, according to the Carribean Conservation Corporation.
Once the hatchlings begin swimming away from the nest, they are generally not seen again until they return to coastal areas as juvenile sea turtles. However, the ocean currents that carry them are also filled with different forms of plastic pollution, leading the young sea turtles to swallow them.
"Juvenile turtles have evolved to develop in the open ocean, where predators are relatively scarce," explains Dr. Emily Duncan, from Exeter-Penryn's Centre for Ecology and Conservation, in a news release from the university. "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."
She explains that juvenile sea turtles, which include hatchlings to younglings with shells less than 50 centimeters (about 20 inches), do not have a specialized diet, meaning they eat just about everything, plastics now included. While their efforts do not yet pinpoint the effect of plastic pollution on sea turtle health, losing the turtles this early in their lives could severely affect their species' population down the line.
Plastics Too Common, They're Untraceable
Researchers examined a total of 121 sea turtles, covering five of the seven known species of sea turtles: loggerhead, hawksbill, green, olive ridley, and flatback. The sea turtles carrying bits of plastic were more common than those coming from the Pacific coast. This includes 86% of loggerheads, 83% in greens, 80% in flatbacks, and 29% in olive ridleys. On the western coast, facing the Indian Ocean, researchers found plastic in 28% of flatbacks, 21% of loggerheads, and 9% of green turtles.
While no plastic was found on the hawksbill turtles in the study, researchers noted that there were only seven of them in the population, a rather small sample size to draw conclusions from.
The most common types of plastic pollution found were polypropylene and polyethylene, materials that are so widely used for different applications that it's virtually impossible to pin down where they came from.
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