This Is How Much Plastic It Takes To Kill A Sea Turtle

Turtles are playing a game of chance with the plastic in our oceans.

A sea turtle which has ingested just one piece of plastic has more than a one in five chance of dying from it, new Australian research has revealed.

The study by CSIRO researchers found the more plastic a turtle consumes, the higher their risk of dying.

While this may sound like an obvious observation, it was previously not known if the plastic pollution in our oceans was actually killing  sea turtles, or simply being ingested without significant harm.

Green sea turtles are an icon of the Great Barrier Reef. Image: Getty

"The big challenge is we know that there’s lots of sea birds, and turtles and other marine wildlife that has plastic in their digestive system, that’s not a question," CSIRO Chief Research Scientist and author of the study Chris Wilcox told ten daily.

"But the issue is, we don’t know what the impact of that is. You know, could be it's just benign, it doesn’t actually bother them or it could be that it actually causes pretty substantial impacts."

The results, published in Scientific Reports, revealed by the time a turtle has taken 14 pieces of plastic into its gut, there is a one in two chance of it causing death.

Wilcox said he was surprised by the number, which proves it takes "not that much" to kill an animal.

Plastic removed from the large intestine of a green sea turtle. Image: provided

"Obviously, if you put enough plastic in an animal it’s going to have to kill them ultimately at some point, but the fact that you would see that at 14, 10, 20, you know that was actually quite surprising,” he said.

While 14 doesn't represent some "magic number," Wilcox said the animals are essentially drawing cards when it comes to eating plastic.

"Each card has some chance of killing you and eventually you get the joker and you die. Around about 14 is about how many it takes to get the joker.”

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The study, which analysed nearly 1,000 turtles found dead and washed up on Australian beaches, also found younger sea turtles are at greater risk of dying from plastic ingestion than their adult counterparts.

Fifteen percent of juvenile and 42 percent of post-hatchling turtles died from plastic ingestion, compared to 8 percent of sub-adult and 16 percent of adult turtles.

Younger turtles were at greater risk of dying from plastic ingestion due to the higher amount of plastic they tend to be eating. Image: Getty

This suggests the feeding location may impact on a turtle's risk of dying, as younger turtles tend to feed in coastal waters closer to the surface which are more likely to be contaminated with plastic items.

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Turtles in the data set which had died of non-plastic related causes had less plastic in their gut than those that died of either indeterminate causes or due to plastic ingestion directly.

This tiny turtle ended up consuming over 40 pieces of difference pieces of plastic, including bits of hard plastic, duct tape and balloons. Image: CSIRO

As for how much plastic scientists found turtles had ingested, the count and mass of plastic ranged from on to 329 pieces and weighed up to 10.41 kg.

Why sea turtles eat plastic they encounter in the ocean is yet to be completely determined.

While it may simply be a function of what the animals come across in their environment, research suggests plastic which physically resembles turtles' natural food is ingested at a higher rate than other types.

As a species which can feed on jellyfish, plastic bags make for an easy case of mistaken identity.

The jellyfish some sea turtles eat look very similar to a floating plastic bag. Images: getty
The Great Plastic Debate

Plastic, which has managed to find its way to even remote parts the Antarctic waters, has been the topic of heated debate in Australia.

There was fierce debate when supermarket giants Woolworths and Coles announced they would no longer provide free single use plastic bags to customers. An arguably fiercer debate was sparked when Coles later backflipped on the decision, before backflipping on that backflip.

McDonalds have even vowed to ditch plastic straws nation wide by 2020.

Wilcox says this study is only another step in determining the exact impact dropping a straw on the ground, for example, has on an entire species.

“I think for lots of people it’s really difficult to connect the thing that’s in their hand to the stuff that they then see on the street, to the pictures they then see of plastic in the ocean to the impact on the turtles that we all value," he said.

"And so being able to make the linkage that here’s the chance that if you drop that plastic bottle on the ground it’s going to kill a turtle, I think is a useful thing.”

Featured image: Getty

Contact the author: vquested@networkten.com.au