Not even four weeks old, Gentoo penguin chicks already have large amounts of microplastics in their digestive tract, especially polyethylene, a study shows. The high number of particles – 27 per chick on average – surprised even the Korean research team.
While gentoo penguins invest a lot of energy in raising their chicks to ensure a good start in life, they also unknowingly pass on a portion of microplastics to them, possibly even with each krill meal.
The research team, consisting of scientists from Seoul National University and the Korea Institute of Analytical Science and Technology, examined the carcasses of 14 gentoo penguin chicks that they had collected from the colony at Narebski Point on King George Island in the South Shetland Islands in the austral summer of 2018/2019. In the lab, they examined the entire digestive tract of each for microplastic particles (plastic between 1 micrometre and 5 millimetres in size) and found an average of 27 particles per chick, and as many as 81 particles in one of the chicks.
Their study, recently published in the journal Nature Scientific Reports, shows that the number of microplastic particles remaining in the digestive tract is considerably higher than studies based on the analysis of faecal samples had suggested previously.
Gentoo penguins continue to feed their young until they are about 100 days old. However, the chicks studied by the research team were only between 12 and 26 days old. Nevertheless, the team does not correlate the number of microplastic particles with the age of the chicks: the researchers found 42 particles in a chick only 16 days old, for example, while a 25-day-old juvenile had nine particles in its digestive tract. The most common particles they found were fragments of polyethylene, and 94 percent of the particles were less than 300 microns in size.
In contrast, previous studies that had analysed faecal samples reported larger particles. The authors of the current study therefore suspect that mainly the larger particles are excreted, while the smaller and lighter ones probably remain attached to the intestinal mucosa and the surface structures of the gastrointestinal tract.
The researchers also tried to identify the sources of microplastic pollution by combining their findings with data from litter surveys on beaches near the penguin colony. During these surveys, which had, however, already taken place in 2013/2014 and 2014/2015, teams had recorded 151 pieces of debris washed up along a stretch of about seven kilometres, almost 80 per cent of which was plastic: fragments, lines, polystyrene, foam insulation and others. The authors can only speculate about the plastic origin, but they suggest that the debris came from nearby stations and ships (fishing, tourism) or was transported into the region by currents.
Although these data on washed-up trash are already ten years old, they do indicate that the waters off King George Island, where the penguins forage, are believed to be polluted with (micro)plastic. As a result, adult gentoo penguins are more likely to catch polluted krill and feed it to their chicks. Previous studies have already proven that krill also ingest microplastics.
The effects of the ingestion and retention of microplastic particles in the body for the penguins and other species at the top of the food web are still not sufficiently understood. Besides physiological problems, inflammations or internal injuries, the pollutants adhering to the plastic can also have negative effects on the organism.
At any rate, more research is needed, and the team of authors also calls for increased efforts to reduce plastic pollution in Antarctica.
Julia Hager, PolarJournal
Link to the study: Kim, Y., Kim, H., Jeong, MS. et al. Microplastics in gastrointestinal tracts of gentoo penguin (Pygoscelis papua) chicks on King George Island, Antarctica. Sci Rep 13, 13016 (2023). https://doi.org/10.1038/s41598-023-39844-6
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