The amount of plastic pollution in the oceans is rapidly increasing. This is problematic, as at least 700 species of marine animals – including sharks, whales, seabirds and turtles – can become entangled in the stuff or mistake it for a tasty snack.
While we know that some species seem to eat plastic because it looks like jellyfish or some other food source, less research has been carried out into what plastic smells like to marine animals.
But now, a study from the University of North Carolina at Chapel Hill has found that the coating of algae and microbes that naturally builds up on ocean plastics causes the rubbish to give off the aroma of food.
The researchers took 15 captive-reared loggerhead turtles, each around five months old, and placed them in a laboratory aquarium. They then piped in aromas of clean water, clean plastic, turtle food, and plastic that had been soaking in the marine environment for five weeks.
The turtles showed no reaction to the odours of clean water or clean plastic. But when they were exposed to the smells of ocean-soaked plastic or turtle food, they exhibited foraging behaviour – like poking their noses out of the water and showing increased activity.
“This finding is important because it’s the first demonstration that the odour of ocean plastics causes animals to eat them,” said Dr Kenneth J Lohmann, who took part in the study.
“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.”
According to the researchers, areas of the ocean with dense concentrations of plastic may trick turtles and other animals into thinking that there is an abundant food source, when the reverse is true.
“Once these plastics are in the ocean, we don’t have a good way to remove them or prevent them from smelling like food,” said Lohmann. “The best thing we can do is to keep plastic from getting into the ocean at all.”