For years, Jack Auty studied how inflammation in the human body drives diseases, ranging from stroke to sepsis to Alzheimer’s, at the Tasmanian School of Medicine. But a visit to a seabird colony five years ago, where he saw many dead sable shearwater (Ardenna carneipes) chicks washed up ashore with their guts full of plastics, changed his course. When he dissected one of them, his first seabird, his trained eyes couldn’t miss the signs of severe inflammation in the bird’s gut. Heartbroken, he decided to offer his knowledge about inflammation to his colleagues studying the impacts of plastics on wildlife.

Since then, Auty and his colleagues have studied how plastics and microplastics, tiny fragments broken down from larger plastic pieces, affect the health of seabirds. In a 2023 paper, they identified a fibrotic disease, called plasticosis, caused by stomach tissue inflammation that results from ingesting microplastics.

“We are exposing all wildlife to plastic, to toxins, to pollution, to global warming — we are doing a giant experiment right now,” Auty told Mongabay, adding that it’s important to study these threats’ impacts on wildlife. “I think we can learn a lot about what’s going on in the human body from wildlife.”

So far, much of that research has been based on insights from dead, washed-up animals stuffed with plastics. But Auty and his colleagues wondered how ingesting plastics continuously affected seabirds that appeared healthy at first look.

In a recent study, published in March in the journal Science Advances, the researchers found an answer: Plastics caused irreversible tissue damage in sable shearwater chicks as young as 3 months, even though the chicks showed no outward signs of ill health. Using a technique called proteomics to analyze proteins in the blood, the researchers found chicks that ingested more plastics had abnormal levels of certain proteins that indicated damage to multiple organs and cognitive decline in their young brains.

“It didn’t seem like there were many organs untouched,” Auty said. “We saw heart proteins, liver proteins, kidney proteins, stomach proteins and brain proteins, all affected by the plastic.”

“The study is really interesting and innovative,” said conservation biologist Jennifer Provencher, who studies plastic pollution and its impact on Arctic seabirds at Environment and Climate Change Canada, the Canadian federal department responsible for environment policy, and was not involved in this study. “This tool, proteomics, is a really exciting new tool in the toolbox to assess the effects of plastic pollution.”

Long-lasting damage in long-lived seabirds

Sable shearwaters are long-lived marine birds that nest in large colonies on islands and shores throughout the Indian and Pacific oceans. During the breeding season, the parents feed chicks fish and squid until they fledge and begin their journey northward. As surface feeders, these birds often scoop up floating bits of plastic that resemble their prey to feed their young. Since both the Pacific and the Indian oceans have floating garbage patches, these birds are susceptible to eating a diet high in plastics.

While the adult birds vomit and put out most of the ingested plastics, the chicks don’t throw up until they fledge, giving researchers an opportunity to study the long-term effects of plastics in the gut.

The authors of this study chose 31 healthy-looking shearwater chicks in the breeding colony at Lord Howe Island, located in the Tasman Sea. They induced vomiting in the chicks and measured how much plastic they had ingested, then divided them into two groups: One for those with more than eight pieces of plastic, or 0.65 grams, in their gut, and the other for those with fewer than five pieces, or 0.5 grams. The researchers then collected blood samples from the two groups and compared the levels of nearly 750 different proteins in them.

They found the chicks that ate more plastics had fewer proteins secreted by the stomach, liver and kidneys, suggesting these organs weren’t functioning normally. There were also signs of trouble with the heart tissues as well, but they weren’t as clear-cut. These birds also had higher levels of cellular proteins in the blood, indicating large-scale cell death in the body.

The most surprising finding, however, was related to the brain. When researchers compared brain proteins, they found a marked difference in a particular protein called brain­derived neurotrophic factor (BDNF), a marker for brain health that’s vital for nerve cells to grow and function, and which helps in learning and memory formation. Chicks that ate more plastics had up to 50% less BDNF than those with fewer plastics in their gut.

In humans, low BDNF is associated with neurodegenerative diseases such as Alzheimer’s and Parkinson’s. In sable shearwaters, the researchers say low BDNF could cause challenges in learning birdsongs and other vocal cues necessary to survive and communicate during courtship and mating. As these chicks fly toward Japan once they fledge and later return to Lord Howe Island to breed, they have to map and remember the directions in their tiny brains — a capability that might deteriorate with plastic-induced cognitive decline.

“We were absolutely shocked,” Auty said about this finding, adding that the brain is a highly protected organ and the surrounding blood-brain barrier blocks most harmful substances. “These birds are 100 days old at most and we are seeing signs of dementia in these birds.” When the researchers looked at proteins in the brains of dead birds, they also saw signs of tissue damage.

Seabird ecologist Richard Phillips at the British Antarctic Survey, who was not involved in the study, called its approach a “big step forward” in understanding the impacts plastics have on seabirds. “It’s very worrying for that species and it points towards longer-lasting effects that might not show until after the chicks have fledged,” he told Mongabay.

Menacing microplastics

Understanding exactly how ocean plastics harm cells and tissues is tricky because there are many parts to this puzzle. Over time, large plastic pieces disintegrate into microplastics and, in the process, release chemicals added during the manufacturing process, many of which are harmful. Floating plastic bits also act as magnets for waterborne pollutants, whose health impacts are barely known.

While the study’s authors say they believe microplastics, which travel easily throughout the body, may be damaging the organs and tissues, they note that further research is needed to ascertain this.

“There’s something special and unique about the toxicity of plastics,” Auty said. “The next question is: What is it about plastic that makes it uniquely damaging to the brain and the stomach and the liver and the kidney?”

Nevertheless, the findings are concerning for seabirds and their future generations.

“It’s not that the birds are just eating plastics and then pooping out the plastics — that’s not what we’re seeing,” Provencher said. “We’re seeing that the plastics cause this suite of sublethal effects, and overall, these things might add up to have negative consequences for populations.” Given that this study was conducted on one species with a fairly small sample size, she said more research is needed to understand if the results hold true for other species in different places.

In a world where seabirds and other marine life face a laundry list of threats — being caught in gillnets, ravaged by hurricanes and heat waves intensified by climate change, starved and decimated by diseases — plastic pollution adds one more item to the list. The good news, however, is that unlike many of these other threats, the solutions are relatively simple, such as improving waste management and reducing plastic use.

“The problem is already quite clear, and the solution is quite clear,” Phillips said. “Now it’s time to act.”

Banner image: Sable shearwaters are long-lived marine birds that nest in large colonies on islands and shores throughout the Indian and Pacific oceans. Image courtesy of jimchurches via iNaturalist (CC BY-NC-SA).

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Citations:
Rivers-Auty, J., Bond, A. L., Grant, M. L., & Lavers, J. L. (2023). The one-two punch of plastic exposure: Macro- and micro-plastics induce multi-organ damage in seabirds. Journal of Hazardous Materials, 442, 130117. doi:10.1016/j.jhazmat.2022.130117

Charlton-Howard, H. S., Bond, A. L., Rivers-Auty, J., & Lavers, J. L. (2023). ‘Plasticosis’: Characterising macro- and microplastic-associated fibrosis in seabird tissues. Journal of Hazardous Materials, 450, 131090. doi:10.1016/j.jhazmat.2023.131090

De Jersey, A. M., Lavers, J. L., Bond, A. L., Wilson, R., Zosky, G. R., & Rivers-Auty, J. (2025). Seabirds in crisis: Plastic ingestion induces proteomic signatures of multiorgan failure and neurodegeneration. Science Advances, 11(11). doi:10.1126/sciadv.ads0834

Vincoff, S., Schleupner, B., Santos, J., Morrison, M., Zhang, N., Dunphy-Daly, … Somarelli, J. A. (2024). The known and unknown: Investigating the carcinogenic potential of plastic additives. Environmental Science & Technology, 58(24), 10445-10457. doi:10.1021/acs.est.3c06840

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