It only takes this plastic pollution to kill a turtle

We know that there is a lot of plastic in the ocean and that turtles (and other endangered species) eat it. It is not uncommon to find dead turtles stranded with full plastic casings.

But we did not really know if the plastic consumed by the turtles actually kills them or if they happen to have plastic at their death. Another way to see this would be to ask: how much plastic for turtles is too high?

Plastic bags, balloons and rope fragments were among more than 100 pieces of plastic in the intestine of a single turtle. Qamar Schuyler

It's a really important question. Just because there is a lot of plastic in the ocean, we can not necessarily assume animals are dying to eat it. Even if some animals do, it does not mean that all animals that eat plastic will die. If we can estimate the amount of plastic needed to kill a turtle, we can begin to answer the question of how turtle populations eat plastic debris.

In our research, published today in Scientific reports on natureWe examined nearly 1,000 turtles dead and stranded on beaches in Australia or found in nets. About 260 of them we examined ourselves; the others were reported to the Queensland turtle database. We carefully studied why turtles died and, for those we examined, we counted the number of pieces of plastic that they had eaten.

Some turtles have died from causes that have nothing to do with plastic. They may have been killed by a boat or entangled in fishing lines or abandoned nets. It is even known that turtles die after accidentally eating a blue-ringed octopus. Others are definitely dead from eating plastic, plastic either puncturing or blocking their gut.

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One of the first meals taken by this sea turtle after birth proved deadly. He died by consuming over 20 tiny pieces of plastic, many of which were about the same size as a grain of rice. Kathy Townsend

Some turtles that were killed by boat attacks or fishing nets, however, had large amounts of plastic in their guts, even though they had not been killed while eating plastic. These turtles allow us to see how much plastic an animal can eat and still be alive and functional.

The table below presents this idea. If an animal is drowning in a fishing net, its probability of being killed by plastic is zero and it lies at the bottom left of the graph. If a plastic bag blocks the digestive tract of a turtle, its chances of being killed by plastic are 100%, and it is at the top right.

Animals that had died of plastic in their intestines, but had other possible causes of death, have a chance to die due to plastic between 0 and 100% – we just do not know and they can fall n & # 39; Anywhere in the graph. Once we have all the animals in the plot, we can ask if we see an increased risk of death from plastic when the amount of plastic in an animal increases.

Conceptual framework for estimating the probability of death from ingestion of plastic debris. Britta Denise Hardesty / Chris Wilcox / Kathy Ann Townsend / Qamar Schuyler

We tested this idea using our turtle samples. We examined the relationship between the probability of death due to plastic, determined by an autopsy of the turtle, and the number of pieces of plastic found inside the animals.

Unsurprisingly, we discovered that the more turtles had plastic pieces, the more likely they were to be killed by plastic. We calculated that for a medium-sized turtle (about 45 cm long), eating 14 plastic objects equates to a 50% chance of being fatal.

That's not to say that a turtle can eat 13 pieces of plastic safely. Even one piece can potentially kill a turtle. Two of the turtles we studied had only eaten a piece of plastic, which was enough to kill them. In one case, the intestines were perforated and in the other, the soft plastic clogged the digestive tract of the turtle. Our analyzes suggest that a turtle has a 22% chance of dying if she only eats a piece of plastic.

A green turtle who died after eating 13 pieces of soft plastic and balloons, blocking his gastrointestinal system. Kathy Townsend

A few other factors have also affected the chances of animals being killed by plastic. Juveniles eat more debris than adults and the rate also varies between different turtle species.

Now that we know how much there is too much plastic, the next step is to apply this method to global estimates of turtle ingestion rates and to determine how plastic is a threat to threatened sea turtle populations.

Britta Denise Hardesty is Senior Researcher at CSIRO Ocean and Atmosphere Flagship Program; Chris Wilcox is Principal Investigator at CSIRO; Kathy Ann Townsend is a lecturer in animal ecology at Sunshine Coast University, and Qamar Schuyler is a researcher at Oceans and Atmospheres of CSIRO.

This article is republished from The Conversation under a Creative Commons license. Read the original article.