Up to 343 plastic parts in the stomach: Even young sea turtles swallow enormous amounts of rubbish, a study shows. This is linked to a behavior that once led them to safe feeding grounds – but today to the growing rubbish vortex of the oceans, the researchers explain. According to them, the intense stress on the young animals could have a particularly severe impact on the population development of the various turtle species.
Remnants of plastic of all kinds – the ugly relics of civilization are now floating everywhere in the oceans and millions of tons of plastic waste are added every year. Numerous studies have already shown how dangerous the stubborn plastic parts are for many marine animals. You may get caught in them or mistake them for food. If swallowed, the indigestible foreign bodies can then cause damage in a number of ways. It is already known that a group of marine animals is particularly affected: Sea turtles often die from ingested plastic waste, studies show.
Young animals in sight
But to what extent does this also affect the young? Scientists working with Emily Duncan from the University of Exeter investigated this question. In total, they examined 121 young sea turtles of different species for ingestion of plastic parts. These were specimens from the Indian and Pacific Oceans that had either been washed ashore or accidentally caught by fishermen. Their age ranged from shortly after hatching to a shell size of 50 centimeters.
As the team reports, they sometimes discovered high levels of contamination from plastic parts: “The young animals mostly contained fragments five to ten millimeters in length, and the particle size increased with the size of the turtles,” says Duncan. The record was set by a young green sea turtle (Chelonia mydas) from the Indian Ocean: It contained a total of 343 plastic parts. Apart from this record, the bottom line seems to be that the pollution in the Pacific is worse. For example, the scientists found there in 86 percent of the loggerhead turtles examined (Caretta caretta) Plastic parts – in the case of the specimens from the Indian Ocean, however, only 28 percent were contaminated.
There were also differences in the type of plastic between the marine regions, the researchers report Most of the plastics in the Indian Ocean were made up of fibers that may have come from fishing utensils, ”says Duncan.
Advantage becomes disadvantage
As part of their study, the scientists describe the problem as an evolutionary trap for the young sea turtles. As they explain, this effect occurs when a once sensible behavior adjustment or the choice of a habitat is now turned into a disadvantage for the survival of a species. The problem with the young sea turtles is the adaptation to the ocean currents. After they have hatched on the beaches and crawled into the water, they let the stream of water carry them into open ocean areas and spend their first years of life there. There is food there and comparatively few enemies.
But now there is a growing danger lurking there: the ocean currents not only transport the small turtles, but also the waste products of humans and concentrate them in certain regions. “The behavior of the young animals now leads them into these particularly heavily polluted areas, such as the so-called Great Pacific Garbage Carpet,” says Duncan. “Young sea turtles are omnivores – and our study shows that this includes plastic,” says the researcher.
“We don’t yet know exactly how plastic ingestion affects young turtles, but any loss at this early stage of life could have significant consequences for populations,” says Duncan. “In the next phase of our research, we want to work together with other research teams and veterinarians to find out more precisely to what extent the ingestion of plastic is harmful to the health of the young animals,” said the scientist.
Source: University of Exeter, Frontiers, technical article: Frontiers in Marine Science, doi: 10.3389 / fmars.2021.699521