- That plastic pollution is harmful to marine life, including seabirds, is well known, but recent research finds that the impacts may be “grossly underestimated” and that plastics can affect multiple organs.
- A new study investigated plastic ingestion by flesh-footed shearwaters and found that — as was determined in past research — initial consumption can harm the stomach. New evidence also showed that impacts are far more expansive, and may cause ongoing health problems distributed throughout body organs.
- Some forms of tissue damage detected by the new research suggest that plastic particles may also act as chemical pollutants, though this requires further study.
- Plastic pollution is a massive growing problem for the world’s oceans and marine life. Earlier this year, researchers announced that the global planetary boundary for novel entities — including plastics — has been surpassed, threatening Earth’s operating systems and life as we know it.
When seabirds ingest plastic, it delivers a “one-two punch” to multiple internal organs, leading researchers to suggest that the impact of widespread ocean pollution on marine bird health may be “grossly underestimated.” Those are the findings of a new study, published in the Journal of Hazardous Materials, that investigated the impact of plastic on flesh-footed shearwaters (Ardenna carneipes).
Researchers collected shearwater fledglings from Lord Howe Island, off the coast of Australia. These birds are known to often consume large amounts of plastic and past research showed that the synthetic contaminants can change their blood chemistry. In the current study, after autopsy, microplastics and nanoplastics were found in the birds’ kidneys, spleen, and proventriculus, with evidence of tissue damage.
Researchers noted that the initial plastic “punch” impacts the proventriculus, the bird’s stomach, with larger chunks of plastic potentially causing punctures or blockages. But as it sits in the stomach, the plastic can also “significantly alter [that organ’s] structure,” Jennifer Lavers, a study co-author and marine ecologist with London’s Natural History Museum Bird Group, told Mongabay in an interview.
The presence of plastic in the stomach specifically damaged rugae and tubular glands, both involved in digestion. How exactly this occurs is unknown, but one hypothesis is that the harm is caused by the numerous synthetic chemicals found within different plastics.
“We didn’t study that in this particular study, so I can’t draw that as a solid conclusion,” said Lavers. But it is known that there’s a “myriad of toxic chemicals” on the surface of plastics, she continued. “So, as [plastics are] sitting there for weeks and weeks on end being… turned over in the stomach, there’s no doubt they would be leeching a pretty horrendous array of toxic chemicals [which] could be contributing to harm to those tissues.”
The second “punch” occurs when plastic is ground into smaller parts in the bird’s gizzard, a kind of second stomach, Lavers said. This process can release microplastics and nanoplastics which then move around the body to become embedded in other organs, causing inflammation, fibrosis, loss of organ structure and other health problems.
The study, limited by funding and time constraints, only looked at a few organs in relation to the pollutants. Yet in all of those investigated, the team found plastic nanoparticles in “very large quantities” and that areas of the organs where they had become embedded “had been really significantly damaged,” Lavers said. Other organs — including the brain and lungs — might also be damaged by micro and nanoplastics, but that remains to be investigated, she added.
The damage caused by this one-two punch — first, by the deformation of the stomach and second, due to the penetration and embedding of very tiny pieces of plastic in various organs — is potentially serious and irreversible.
Heath impacts could include “slower development, nutritional stress and poor body condition,” the study notes, while also possibly compromising chicks’ ability to absorb nutrients from food. Though the full health implications and wider impact on shearwater populations are not known at this stage, the outlook is undoubtedly not positive, the researchers stated.
The team also found that the quantity of plastic, and frequency with which it is consumed, do not necessarily impact the amount of damage caused to internal organs. A single “macroplastic ingestion event,” could pose significant issues due to the breakdown in the stomach.
However, “If you have a bird with very low plastic exposure and one with very high plastic exposure in its stomach, do you then find differing levels of plastics embedded within its tissues? The answer is no,” Lavers said. The research “demonstrates that you can have individuals with just one or two pieces of plastic in their proventriculus, and you can still have extremely high exposure to the small stuff.”
Though the study only looked at flesh-footed shearwaters, the authors state that similar effects are likely to be found in other birds that consume plastic.
“A bird stomach is a bird stomach, for all intents and purposes; and plastic is in all intents and purposes, plastic,” explained Alex Bond, principal curator of birds at the Natural History Museum and a study co-author. “So, when you put the two of them together, there’s nothing that would suggest that the responses that we’re seeing are unique to this species.”
Upon reading the new paper’s title, marine ecologist Gerardo Zardi, of Caen University in France, assumed it would be yet another study on plastics ingestion, confirming known “negative impacts on birds.”
But Zardi, who studies seabirds in Portugal and who was not involved in the research, told Mongabay that the new study adds weight “to the argument that we still do not know much about the [comprehensive] impacts of plastic, which we just think [of as mostly being] ingestion and entanglement, and we are starting to see some behavioral effects.” Every year “the negative effects are piling up,” he added.
“The title of this paper was a ‘one-two punch,’” Zardi noted, but “I’m afraid it’s going to be a ‘knock-out’ for biodiversity soon because of plastic pollution.”
Earlier this year, researchers warned that our world has transgressed a planetary boundary for human release of novel entities into the environment, threatening Earth’s operating systems and life as we know it. Plastics in their many forms are among tens of thousands of synthetic novel entities produced since World War II, flowing into the world’s coastal waters and oceans, causing as yet largely undescribed and unquantified impacts on species, ecosystems and biodiversity.
This study offers more evidence of the potential sublethal effects of plastic ingestion, said Bond, but it does even more than that. “I think it contributes to the mounting evidence that plastics [impacts] are just more pervasive than we thought they were.”
“I think part of what we need to think about in terms of plastics is to stop considering them as a physical contaminant and think of them more as a chemical pollutant,” Bond continued, noting that, similar to other pollutants such as mercury, getting rid of plastics entirely is not possible.
“I think we need to reconcile with that, and we need to start mitigating the effects of plastics and regulating their use, disposal, transportation, etc, in the same way that we do with chemical pollutants, rather than [treating it] as a physical object.”
Banner image: Plastic pieces found inside a dead shearwater. Image © Alex Bond.
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