A new study by researchers at the University of Florida and Stanford University has found the reason why plastic in the ocean is such a threat to Turtles, and the answer is complex and difficult to overcome.
By now it is an accepted fact amongst conservationists and those who follow efforts to rehabilitate the ocean that sea turtles are among the animals most threatened by the dumping of plastic into the sea. One study conducted across numerous Australian universities estimated that as much as 52 percent of the global sea turtle population has consumed some form of plastic. Further, another study by CSIRO in Australia found that a turtle that has consumed just a single piece of plastic has a 22 percent chance of dying from it, while that probability increased to 50 percent when they had 14 plastic items in their bellies.
But just why the turtles were eating the plastic in the first place was difficult to understand. Numerous people had attempted to explain the phenomenon, with the most widely accepted theory being that plastic in the ocean looked to the turtle like jellyfish, their natural prey, and this, in turn, lead them to try eating it.
The University of Florida study has however found a different phenomenon is to blame. In order to make their findings, researchers conducted experiments where 15 young loggerhead turtles raised in captivity were recorded on video reacting to different stimuli. The researchers had previously established that while the appearance of the plastic in the water could cause some confusion, Turtle’s were generally able to differentiate the plastic from prey items, the same could not be said for smell.
The team had found that the same odours sea turtles rely on to track down food can also arise from biofouled plastic debris, meaning trash that has accumulated microbes, algae and plants on its surface can give off the same smells as the food they like to eat.
The experiments were therefore designed to see if the turtles could differentiate between waste and food using only their noses. The team fed odours through a pipe into the turtle’s tank that ranged from deionized water and clean plastics for control to shrimp meal, fish and biofouled plastic and the results were astonishing. The team found that the turtles reacted to the biofouled plastic the same way they reacted to food, keeping their nostrils above the water for three times longer than the control odours to properly take in the scent.
“We found that loggerhead sea turtles respond to odours 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,” says Joseph Pfaller of the University of Florida, Gainesville. “This ‘olfactory trap’ might help explain why sea turtles ingest and become entangled in plastic so frequently.”
The results bare direct correlation with a 2016 study that found that albatross and petrels are often drawn to eating plastic from the sea due to the smell.
“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 said. “These are important and troubling pieces to the puzzle, and all plastics pose dangers to turtles.”