Candy wrappers. Balloons. Grocery bags. Every day, the equivalent of 2,000 full garbage trucks worth of plastic gets dumped in the world's oceans.
Scientists have long known that plastic waste is harmful to marine life. A new study, published in the journal Proceedings of the National Academy of Sciences, shows much plastic a marine animal has to eat for it to be lethal.
"What surprised me the most is how little it takes to become deadly," said Britta Baechler, a co-author of the study and director of Ocean Plastics Research at the Ocean Conservancy.
Less than three sugar cubes' worth of plastic could kill an Atlantic puffin. Two baseballs' worth would do in a sea turtle. The equivalent of a soccer ball is enough to off a seal or dolphin.
"For seabirds, ingesting just six tiny pieces of rubber, each smaller than about the size of a pea, can result in a 90 percent chance of death," Baechler said.
To determine the amounts and the kinds of plastic that marine animals were eating, researchers compiled the autopsy data of more than 10,000 deceased animals from 53 studies that had been conducted around the world. Among the victims: an albatross with an entire plastic bottle in its digestive tract.
"In another instance, there was a sperm whale that had died from eating an entire bucket that broken up in its gut and caused an obstruction," Baechler said.
The study focused on macroplastics, debris that can be seen with the naked eye. It didn't look at microplastics, which can be microscopic and have been found even in the deepest parts of the ocean. Nor did it look at entanglements, the other primary way plastics impact marine animals.
Greg Merrill, a researcher who focuses on plastics and marine animals and wasn't involved in the study, said scientists have known for years that marine animals are eating plastic, often because it looks like their natural food.
"Like if you are a sea turtle, for example, and you eat jellyfish, a plastic grocery bag is pretty similar," he said. "It's fluid. It's not got a lot going on with it."
He published a study last year that found whales, which use sonar to prey on food in the blackness of the deep ocean, can even be confused by plastic. The acoustic signature — the strength of the echo — a whale would hear coming off of a piece of plastic waste was similar to what they'd hear coming off of their natural prey.
"So it kind of suggested that perhaps they're mistaking their acoustic cues and ingesting plastic that way," he said.
The new study, Merrill said, is the kind of research that's needed to show policymakers and the general public how plastic is negatively affecting the health of marine animals. He and the authors of the new study said policy changes are needed internationally to reduce the production of plastic products — particularly single-use plastics, like soda bottles and food packaging, that have a long life after their single use.
"I think it's pretty obvious but plastic pollution is not just unsightly," Baechler said. "It really does represent a serious immediate threat to marine life and we need urgent action."
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