Turtles, the WWF alarm: killed by too much plastic in the Mediterranean

The association's report: every year 570 thousand tons in the waters of the Mare Nostrum, 5 kg of waste accumulates every day for every kilometer of coastline

by Federico Coppini
Turtles, the WWF alarm: killed by too much plastic in the Mediterranean

The life of sea turtles is severely compromised by plastic, which in various forms is found in Mediterranean waters. They risk being trapped by nylon lines and nets abandoned or accidentally lost by fishermen. To be suffocated by the ingestion of waste exchanged for jellyfish or small fish.

To be intoxicated or poisoned by microplastics that are ingested and then deposited in the stomach, both directly and in the form of bioaccumulation, i.e. the sum of the substances swallowed directly and those contained in the organisms of the crustaceans or of the small marine fauna they eat.

WWF Italia has put together some numbers and today, on World Turtle Day - which is celebrated on June 16 in honor of Archie Carr, the American herpetologist who had dedicated his life to their study -, he draws several sums.

But one, in particular, must make you think: every year there are about 570 thousand tons of plastic that pour in various forms into the Mare Nostrum and which correspond to more than 5 kg per day per kilometer of coast. Because the Mediterranean is a closed sea and currents bring 80% of waste materials back to shore.

But plastic is everywhere, even offshore, and already in 2016 a study published in ScienceDirect had estimated that 80% of the Caretta Caretta pelagic turtles, one of the three species present in our sea and the only one that nests also on the Italian coasts, turned out to have ingested plastic.

Olfactory trap
Plastic is not the only threat to turtles, endangered by accidental catches during fishing, by intensive tourism, by collisions with boats. But it is what is predominant today. And, as mentioned, not only the most obvious one, such as plastic bags, which was often thought to attract turtles due to their resemblance to jellyfish.

A new study published in Current Biology tries to give a different explanation: it would not be the shape but the smell of plastic to attract animals. Not the original one, which has nothing natural and attractive, but what is determined by the accumulation of layers of bacteria and algae that are deposited on the fragments, which instead are a strong attraction.

A real olfactory trap with potentially lethal consequences. Bioaccumulation has been said above and research published in Nature two years ago confirmed that even the Pelagia noctiluca jellyfish, the most common in our seas, feed on themselves despite plastic, which ends up becoming an additional ingredient in the turtle diet .

Endangered species
The consequences of this plastic indigestion - which is likely to increase due to the greater use of disposable plastic products as a consequence of the Covid emergency - are intestinal blockages, alteration of the sense of satiety, intoxication.

Every year there are many who die from accidental catches or plastic. Today the Caretta caretta is classified as vulnerable in the red list of the International Union for the Conservation of Nature (Iucn), as well as the Dermochelys Coriacea (also called "leatherback turtle", the largest existing), while the green turtle Chelonia Mydas is referred to as "endagered".

An even worse situation is found for two species not present in the Mediterranean, the Kemp turtle (Lepdochelys kempii) and the imbricate turtle (Eretmochelys imbricata) which are at the "critically endagered" level, one step away from extinction.