Researchers trying to figure out why turtles eat tonnes of ocean plastic have found it could be due to what the material smells like.
With the Great Pacific Garbage Patch just one part of a massive pollution problem in our oceans, the diets of various marine creatures are being significantly affected. Now, researchers from the University of North Carolina at Chapel Hill have discovered why sea turtles, in particular, eat such large quantities of ocean plastic.
In a paper published to Current Biology, the researchers found that ocean plastic builds a coating of algae and microorganisms that, to the turtles, smells like food.
“This finding is important because it’s the first demonstration that the odour of ocean plastics causes animals to eat them,” said researcher Kenneth J Lohmann.
“It’s common to find loggerhead turtles with their digestive systems fully or partially blocked because they’ve eaten plastic materials. There also are increasing reports of sea turtles that have become ill and stranded on the beach due to their ingestion of plastic.”
To understand sea turtle behaviour around ocean plastics, the researchers compared how the creatures reacted to smelling odours of turtle food, ocean-soaked plastic, clean plastic and water. In tests, the turtles ignored the clean plastic and water, but responded to the odours of food and ocean-soaked plastics as part of foraging behaviour.
This included poking their noses out of the water repeatedly as they tried to smell the food source, and increasing their activity as they searched.
“Very young turtles feed at the surface, and plastics that float on the surface of the ocean affect them,” said Kayla M Goforth, a doctoral student who worked on the study.
“Older turtles feed further down in the water column, sometimes on the ocean bottom. Regardless of where plastics are distributed in the ocean, turtles are likely to eat them.”
The study now raises questions on the long-term impacts plastics have on all ocean species and whether they think dense concentrations may be food, according to Lohmann.
“These areas may draw in marine mammals, fish and birds because the area smells like a good foraging ground,” he said. “Once these plastics are in the ocean, we don’t have a good way to remove them or prevent them from smelling like food.”