Seabirds that swallow ocean plastic waste have scarring in their stomachs – scientists have named this disease 'plasticosis'
Published in Science & Technology News
As a conservation biologist who studies plastic ingestion by marine wildlife, I can count on the same question whenever I present research: “How does plastic affect the animals that eat it?”
This is one of the biggest questions in this field, and the verdict is still out. However, a recent study from the Adrift Lab, a group of Australian and international scientists who study plastic pollution, adds to a growing body of evidence that ingesting plastic debris has discernible chronic effects on the animals that consume it. This work represents a crucial step: moving from knowing that plastic is everywhere to diagnosing its effects once ingested.
There’s wide agreement that the world is facing a plastic pollution crisis. This deluge of long-lived debris has generated gruesome photos of dead seabirds and whales with their stomachs full of plastic.
But while consuming plastic likely killed these individual animals, deaths directly attributable to plastic ingestion have not yet been shown to cause population-level effects on species – that is, declines in population numbers over time that are linked to chronic health effects from a specific pollutant.
One well-known example of a pollutant with dramatic population effects is the insecticide DDT, which was widely used across North America in the 1950s and 1960s. DDT built up in the environment, including in fish that eagles, osprey and other birds consumed. It caused the birds to lay eggs with shells so thin that they often broke in the nest.
DDT exposure led to dramatic population declines among bald eagles, ospreys and other raptors across the U.S. They gradually began to recover after the Environmental Protection Agency banned most uses of DDT in 1972.
Ingesting plastic can harm wildlife without causing death via starvation or intestinal blockage. But subtler, sublethal effects, like those described above for DDT, could be much farther-reaching.
Numerous laboratory studies, some dating back a decade, have demonstrated chronic effects on invertebrates, mammals, birds and fish from ingesting plastic. They include changes in behavior, loss of body weight and condition, reduced feeding rates, decreased ability to produce offspring, chemical imbalances in organisms’ bodies and changes in gene expression, to name a few.
However, laboratory studies are often poor representations of reality. Documenting often-invisible, sublethal effects in wild animals that are definitively linked to plastic itself has remained elusive. For example, in 2022, colleagues and I published a study that found that some baleen whales ingest millions of microplastics per day when feeding, but we have not yet uncovered any effects on the whales’ health.
The Adrift Lab’s research focuses on the elegant flesh-footed shearwater (Ardenna carneipes), a medium-size seabird with dark feathers and a powerful hooked bill. The lab studied shearwaters nesting on Lord Howe Island, a tiny speck of land 6 miles long by one mile wide (16 square kilometers) in the Tasman Sea east of Australia.