Sea turtles' unfortunate appetite for plastic trash could be due to the misleading smell of reeking plastic.
It’s long been assumed turtles eat plastic marine pollution because they visually mistake its appearance for food. After all, a floating plastic bag can look a lot like a jellyfish with hungry eyes. However, a new study suggests turtles might also be mistaking the scent of plastic for food.
Research by the University of Florida has found that bacteria and algae can often accumulate on plastic pollution in the sea, a process referred to as being “biofouled,” giving the impression it smells of nutritious food.
“We found that loggerhead sea turtles respond to odors from biofouled plastics in the same way they respond to food odorants, suggesting that turtles may be attracted to plastic debris not only by the way it looks but by the way it smells," lead author Joseph Pfaller said in a statement.
"This 'olfactory trap' might help explain why sea turtles ingest and become entangled in plastic so frequently."
Using 15 young captive-reared loggerhead turtles in a lab setting, the team tested their reactions to four different smells sprayed into the air above their tank: a fish and shrimp meal, “biofouled” plastic, neutral deionized water, and clean plastic. Reporting in the journal Current Biology, the researchers found that sea turtles appear to react to these biofouled plastic chunks in exactly the same way they respond to food. In fact, the turtles stuck their noses out of the water to sniff the plastic for three times longer than the food scent.
At the risk of sounding obvious, this is not good news. Plastic pollution continues to be a growing problem in our world’s oceans, known to threaten almost 700 species of marine animals, from sharks and rays to turtles and whales.
In one especially shocking example, a sperm whale washed up in Scotland just a couple of months ago with a 100-kilogram (220 pounds) ball made up of plastic trash and fishing equipment in its guts. Even more recently, a sea turtle was rescued off the coast of Argentina with a belly full of plastic pollution, causing it to poop out plastic for weeks, and a brand new species of amphipod was discovered in the Mariana Trench, the deepest trench on the planet, only for researchers to discover plastic microfibers in its gut.
It doesn’t even take huge amounts of plastic to cause problems with marine life either. A previous study in 2018 found that sea turtles can sometimes die from ingesting as little as one piece of plastic.
The effect of plastic pollution on marine life is complex and a relatively new problem. However, as this new study displays, researchers are quickly putting the puzzle pieces together. "The plastic problem in the ocean is more complex than plastic bags that look like jellyfish or the errant straw stuck in a turtle's nose," Pfaller added. "These are important and troubling pieces to the puzzle, and all plastics pose dangers to turtles."