It is believed that more than half of the world's sea turtles have plastic in their bowels, while millions of tons of garbage continue to be dumped into the oceans each year, say CSIRO researchers.
An analysis of approximately 1000 turtles found dead on Australian beaches found hundreds of plastic pieces in the entrails of the animals.
These included plastic bags, hard plastic shards, balloons, pole wrappers and pieces of string.
"Some of the turtles we studied had eaten only one piece of plastic, which was enough to kill it," Dr. Kathy Townsend of the University of Sunshine Coast said on Friday.
"In one case, the intestine was perforated, and in the other, the soft plastic obstructed the intestine."
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Researchers found that once a turtle had eaten a piece of plastic, had a 22 percent chance of dying and by the time he had ingested 14 plastic items, the probability of death increased to 50 percent.
When the load reaches around 100 pieces, death is certain.
"We knew that the turtles consumed a lot of plastic, but we did not know for sure if that plastic really killed the turtles," said CSIRO Oceans and Atmosphere researcher Chris Wilcox.
Sea turtles were some of the first animals that were discovered to be ingesting plastic.
Being able to understand the effect of plastic on them will help scientists determine the impact of pollution on the world population in all seven species.
Modeling can also be adapted to study other marine animals affected by plastic in the world's oceans.