More Than 1,200 Marine Animal Species Eat Plastic. Ingesting Even a Tiny Amount Can Kill Them, a New Study Suggests

Researchers examined more than 10,000 animal autopsies to figure out how much plastic is too much for ocean wildlife

Mary Randolph | Correspondent

November 21, 2025

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Each year, an estimated 24 billion pounds of plastic end up in oceans across the world.

Unable to distinguish that trash from natural food sources, many marine animals end up ingesting it. While scientists have long known about this problem, a new study that includes data from more than 10,000 marine animal autopsies shows just how much plastic can hurt wildlife.

“What surprised me the most is how little it takes to become deadly,” Britta Baechler, a co-author of the study and director of ocean plastics research at the nonprofit Ocean Conservancy, tells NPR’s Nathan Rott.

The researchers’ analyses suggest that a small seabird, such as an Atlantic puffin, has a 90 percent chance of death after eating just three sugar cubes’ worth of plastic, Baechler and her co-author Erin Murphy, manager of ocean plastics research at the Ocean Conservancy, write in the Conversation. A loggerhead sea turtle would face a similar fate after eating an amount of plastic equal to about two baseballs—and a harbor porpoise, too, after ingesting the equivalent of a soccer ball.

The findings were published on November 17 in the journal Proceedings of the National Academy of Sciences.

Nearly 1,300 species have been documented to make a meal of plastics. But Baechler and her colleagues wanted to know how much is too much plastic for an animal to eat, per the Conversation.

So, they gathered marine animal autopsy information from published literature, databases documenting stranded animals and the team’s own research. The final dataset included representatives from all seven sea turtle species, 57 seabird species and 31 mammal species.

The researchers then looked through the records for ingestion of macroplastics, pieces that are visible to the naked eye. Plastics of this size can block or slice an animal’s organs or cause its digestive tract to twist. 

In total, about half of the examined sea turtles, one-third of seabirds and one in eight marine mammals had plastics in their stomachs. Analyzing how many pieces of plastic and the volume of plastic that would likely kill the animals revealed how a small amount of ingested plastic can cause great harm.

Still, “this is likely an underestimate of the impacts of ingestion, and it’s definitely an underestimate of the lethality of plastics more broadly,” Murphy tells Susanne Rust of the Los Angeles Times. The study didn’t examine other ways plastics can hurt wildlife, such as strangulation, malnutrition or toxic effects. It also didn’t look at the harms of tinier pieces of plastics—microplastics—which have been found in the deep ocean and can also affect marine life.

And not all plastics cause harm equally, the team discovered. Rubber materials, such as balloons, seem to be the worst type for seabirds—merely six pea-sized pieces could be deadly, per the Conversation. Marine mammals, on the other hand, were most affected by lost fishing gear; 28 tennis balls’ worth could kill a sperm whale.

Greg Merrill, an ecologist at Duke University who was not involved in the study, tells the L.A. Times that this paper is “a brilliant contribution to the field.”

“We have thousands of examples of marine animals ingesting plastic debris,” he writes in an email to the publication. “But for a number of reasons, e.g. lack of data, difficulty of conducting laboratory-based experiments and ethical considerations, risk assessments are really challenging to conduct.”

Researchers say the best way to protect wildlife from plastic is to reduce the amount of it that enters the ocean, namely through local and national policy.

“I think it’s pretty obvious, but plastic pollution is not just unsightly,” Baechler tells NPR. “It really does represent a serious immediate threat to marine life, and we need urgent action.”

Mary Randolph | Read More

Mary Randolph is a former editorial intern with Smithsonian magazine.