Turtles are omnivorous animals (most of them); that is to say, they feed both on animal prey (crickets, worms, small fish, jellyfish …) and on vegetables such as algae, and green leafy plants such as kale.
Specifically, jellyfish are one of the turtles’ favorite prey. But this is a trap for them, since eight million tons of plastic end up in the ocean each year, and the appearance of some plastic waste can be confused with that of these delicious, jelly-like organisms. In the same way, traces of plastic of certain colors can resemble algae that can be ingested by turtles. The risk of this happening is clear: many marine animals die from ingesting plastic, or die from being trapped in it.
Specifically, the green turtle ( Chelonia mydas ), a species of sea turtle, is the type of turtle most likely to swallow plastic that resembles its food , according to research by scientists at the University of Exeter and the Society. for the Protection of the Turtles of Cyprus.
Through examination of the guts of turtles found on the beaches of Cyprus, the investigation revealed that the remains of transparent plastic, or natural colors such as green or black, are the “favorites” of the turtles, above the remains of other shapes and colors.
Knowing these characteristics would allow us to identify with which plastic debris we must be more careful when recycling (or what type of plastics we must completely eliminate from use) to avoid ending up in the sea.
But the worrying fact is that, of the turtles whose entire gastrointestinal tract could be examined (of the 34 turtles examined, the scientists were able to examine the complete gastrointestinal tract of 19) some trace of plastic was found in all of them. One of the copies contained no less than 183 pieces; the least, contained 3 pieces of plastic.
Although scientists know that ingesting plastic can be the cause of the death of many marine animals , this particular study could not determine what role plastic played in the death of the turtles, and concluded that the majority had probably died as a result of interaction with fishing nets.
A deliberate choice, a potentially deadly trap
As the Society for the Protection of Turtles indicates, sea turtles are primarily visual predators, capable of choosing food by size and shape, and in this study we found strong evidence that green turtles show a preference for certain sizes, shapes and colors: black, transparent or green threads and sheets.
Sources of this plastic could be black garbage bags and fragments of items such as fishing ropes and carrying bags.
Furthermore, the study found that smaller turtles tend to contain more plastic , and this could be for two reasons: either because they are less experienced and therefore more likely to eat the wrong food; or because diet choices change with age and size.
Previous research had suggested that leatherback turtles eat plastic that looks like their jellyfish prey , and at the University of Exeter they wanted to know if something similar could be happening with green turtles.
According to Professor Brendan Godley, who leads Exeter Marine’s research strategy: “Research like this helps us understand what sea turtles eat and whether certain types of plastic are ingested more than others.”
“It is important to know what types of plastic could be a particular problem, as well as highlighting problems that can help motivate people to keep working to reduce overall plastic consumption and pollution,” the professor continues.
The research has been published in the journal Scientific Reports .
Source : Diet-related selectivity of macroplastic ingestion in green turtles ( Chelonia mydas ) in the eastern Mediterranean (2019) Scientific Reports. https://www.nature.com/articles/s41598-019-48086-4
