Scientists have long known that seabirds ingest microplastics by mistaking them for food. And according to a study published Monday, this waste not only clogs or passes through the stomach, but also disrupts the balance of the entire digestive system.
By studying the digestive tracts of two Atlantic seabird species, the Northern fulmar and the Cory’s shearwater, the researchers found that the tiny plastic particles messed up their microbiome – a complex set of microorganisms, including good and bad bacteria.
Basically, the more microplastics the bird ingests, the more gastric bacteria, mostly beneficial, decrease, while potentially pathogenic agents proliferate.
At the origin of intestinal dysbiosis
The study published in la revue Nature Ecology & Evolution also shows an increase in antibiotic-resistant microbes and reveals that certain types of microplastics could also release chemicals that disrupt the gut microbiome of birds.
The study confirms previous findings that prolonged ingestion of microplastics causes what is called gut dysbiosis, which is an imbalance between healthy bacteria and harmful bacteria in the digestive tract. Its implications can be far-reaching because, like birds, many species, including humans, have an important microbiome within their digestive system.
“It’s a whole symbiosis that takes place, both in birds and in humans,” said Gloria Fackelmann, from the University of Ulm (Germany), main author of the study. . The diversity of this intestinal flora is often a guarantee of good digestion and helps to strengthen the immune system. But some of these bacteria and microbes can also have a deleterious effect on health and cause disease, even if for the moment the precise effect of each of them on the body is still poorly defined.
Humans affected too?
But overall, more and more studies highlight the harmful effects of microplastics – diameter less than five millimeters – on the health of animals.
In humans, their presence can cause allergic reactions and cell damage, and the chemicals they contain have also been linked to increased cancer risks, reproductive problems and DNA mutations. The study authors hope that their findings in seabirds will lead to related studies in humans.
“If this man-made substance (plastic) can alter our microbiome, I think that should give people pause,” Gloria Fackelmann said. Microplastics, derived from the breakdown of plastic products in the environment, are found across the globe, from the deepest ocean trenches to the summit of Mount Everest, and in most animal food chains. In humans, traces have been detected in blood, breast milk and placenta.