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- Australian researchers examined the digestive tract of 246 sea turtles caught along the Queensland coast and counted up to 329 pieces of plastic.
- The younger turtles have consumed amounts of plastic pieces much higher than adult turtles, according to the study, perhaps because they are less selective about what they eat. Young turtles also drift with ocean currents, just as plastic debris tends to do, and both could end up in the same places.
- The more plastic parts a turtle has in its gut, the greater the chance of it being killed by the plastic. For a medium-sized turtle, ingesting more than 14 pieces of plastic results in a 50% probability of death.
In a video that became viral in 2015, researchers spent nearly 10 minutes extracting a 10-centimeter (4-inch) plastic straw from the nostril of a male olive-headed tortoise (Lepidochelys olivacea) off the coast of Costa Rica. During the entire duration of the extraction, the turtle was writhing in pain.
Plastic straws are just one of the trillions of plastic waste that has been found in the ocean, many of which sink deepest and darkest depths. Previous research has shown that almost half of the world's marine turtles may have ingested some form of plastic. Floating plastic pieces and balloons can look like jellyfish or squid – food that turtles eat in the sea. However, not all turtles that eat plastic die because of plastic. Some die after getting entangled in fishing nets, while others are hit by ship propellers.
Do all age groups of turtles consume plastic? And how much plastic is deadly for a sea turtle? A new study has answers.
Australian researchers examined the digestive tract of 246 sea turtles caught along the coast of Queensland state and found that 58 individuals had plastic in their bowels, with a number of pieces up to 329.
Researchers report that younger turtles, both after birth (or a small turtle that feeds in the ocean) and juveniles, consumed significantly greater amounts of plastic than adult turtles. Scientific reports.
This may be due to the fact that young turtles are less selective about what they eat and eat what they encounter, said Britta Denise Hardesty, Principal Investigator at the Ocean Science and Atmosphere Unit of the Scientific Research Organization and Commonwealth Industrial, Australia. Young turtles also tend to feed on the surface of the ocean, where floating plastic pieces are more likely to occur. In addition, young turtles drift with ocean currents, just as plastic debris tends to do so, and both could end up aggregating in the same places.
"We know that not only do these smaller and younger turtles eat more plastic, but they also tend to eat more different types of plastic, including balloons and other types of plastic," Hardesty said in an email. "It may be that they are simply less selective and that they encounter higher concentrations of floating debris than they then ingest."
Brendan Godley, professor of conservation science at the University of Exeter, UK, who was not involved in the study, told Mongabay that the likelihood of plastic being a significant threat at this stage Early life of turtles is worrisome.
"This is particularly worrying because pieces of plastic and baby turtles are likely to be clustered in similar areas," he said. "It is thought that most sea turtles undertake at least the first years to drift offshore."
In addition to data from the 246 autopsied turtles, the team also examined 706 sea turtle autopsy records in a government-run strandings database to determine the likelihood of death from plastic ingestion.
The team used turtles that died from a known cause, such as those who drowned in fishing gear or died after a boat attack, as a control group; the probability that these animals were killed by plastic was zero. The researchers compared this control group with turtles who died of uncertain causes (their intestines had plastic at the time of the autopsy, but their deaths could have been due to other causes such as infections or an attack. d & # 39; propeller). or blocking their intestines. They then plotted all turtle data to see if there was any relationship between the probability of death from plastic ingestion and the concentration of plastic in the bowels of turtles.
In the end, there is East a relationship. The more plastic parts a turtle has in its gut, the greater the chance of it being killed by the plastic. For a medium-sized turtle, ingesting more than 14 pieces of plastic results in a 50% probability of death.
"I think it's pretty hard to learn that you have a 50% chance of dying if you are a turtle that has eaten 14 pieces of plastic, even if they are very small pieces," Hardesty said. "Even a piece of plastic means you have more than a 20% chance of dying while eating it."
According to Hardesty, hard plastic shards are more likely to cause intestinal perforation, while thin film-like plastics are more likely to block the digestive tract, preventing other foods from getting through.
Hardesty's team then considers how the size or type of plastic affects the turtles. "It's an obvious next step and something very interesting," she said.
Godley said the study was "a great first step toward measuring what we know to be a vast and pernicious threat to marine vertebrates such as turtles and seabirds."
"The authors provide a very defensible framework for us to measure the mortality risk from plastic ingestion," he said. "Ongoing interdisciplinary work will be needed with multinational collaborative efforts … to clarify if and where this threat can become a limiting factor to the population."
Quote:
Wilcox, C., Puckridge, M., Schuyler, Q.A., Townsend, K. and Hardesty, B.D. (2018) A quantitative analysis linking the mortality of sea turtles and the ingestion of plastic debris. Scientific reports, 8 (12536). DOI: 10.1038 / s41598-018-30038-z
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