Nearly all seabirds—and other ocean creatures, like sea turtles and whales—are consuming plastic. According to a new study, ingesting even just a few bits of plastic can have long-term health consequences, especially for baby seabirds.
To understand the impact of plastic pollution on the animals, a group of researchers from Australia studied a colony of flesh-footed shearwaters, Ardenna carneipes. The population of interest lives on Lord Howe Island, a remote speck of land several hundred miles offshore right between of Australia and New Zealand. In recent years, the birds have undergone a 29 percent drop in population, partially due to problems with plastic, reports Stephen Leahy from National Geographic.
The birds spend most of their lives on the open water, but return to the island to breed, feeding their chicks over the course of several weeks. In previous studies, scientists have found that seabirds mistake plastic pieces for food, often feeding plastic shards, bottle lids, pen caps and other trash to their young. Consuming too much plastic can be a death sentence for birds, like the one that was found with 274 pieces of plastic trash in its tummy. But researchers have found that 80 to 90 percent of the chicks had at least one piece of plastic in their system, not enough to kill them, but perhaps enough to interfere with development. The study appears in the journal Environmental Science & Technology.
To analyze the sub-lethal impact of that plastic, the team pumped the stomachs of chicks on the island, cataloguing the plastic they found. To investigate the chemicals the plastic was likely leaching into their systems, they took a blood sample from each that was tested back in the lab.
They found that even one piece of plastic in a chick’s stomach was enough to alter its blood chemistry. Those little birds had higher cholesterol and more amylase, an enzyme that turns starch into sugar. The birds also had lower dissolved calcium in their bloodstream and more uric acid, which could be signs of kidney disfunction.
Rob Picheta at CNN reports that the plastic contaminated birds also had overall lower body masses as well as shorter bills and wingspans. As they mature into adults, the birds might look fine, but the study suggests they may have chronic health problems that could impact the health of the species as a whole.
What the impact is on their life cycle may be is hard to say and will require more research. Co-author Alex Bond, senior curator of birds at the Natural History Museum, says if the plastic is disrupting the birds' kidneys, it could spell trouble for the species.
“This can have some pretty significant consequences for a bird that has to fly unaided to the Sea of Japan when they leave the island,” Bond tells National Geographic’s Leahy.
According to a press release, it’s not yet clear if these blood chemistry changes are caused by chemicals leaching into the birds from the plastic itself or from colonies of bacteria that form when the plastic floats in the ocean for years and sometimes decades.
Another recent study in Marine Pollution Bulletin, however, suggests it may be the plastic’s fault. Researchers from the Tokyo University of Agriculture and Technology analyzed 194 plastic fragments collected from seabird guts finding additives, including UV stabilizers and flame retardants, accumulated in the birds’ soft tissue. They estimate that if a bird eats 15 pieces of plastic trash, it has a 73 percent chance of being contaminated by the additives.
While humans don’t feed plastic chunks to their babies, these studies make first author Jennifer Lavers, a marine toxicologist at the Institute for Marine and Antarctic Studies, wonder what the impact of being surrounded by so much plastic has on our species.
“The data is alarming. It is not a big leap to think that what’s happening to wildlife might be happening to us,” she tells Leahy.