An international team of scientists from the LOEWE Center for Translational Biodiversity Genomics (TBG), the Senckenberg Biodiversity and Climate Research Center Frankfurt (SBiK-F) and the Estonian National Laboratory for Chemistry and Physics shows for the first time that microplastics can trigger evolutionary changes. Their genomic study was published in the journal Chemosphere. Accordingly, the ingestion of microplastic particles triggers an evolutionary adaptation in the midge Chironomus riparius.
Microplastics are entering the environment in ever-increasing concentrations and decompose very slowly. The plastic particles, which are up to five millimeters in size, are spread by water and wind. Microplastics have now been detected in all ecosystems, from the deep sea to high alpine glaciers. These particles can even get into the brain of mammals, for example. Although there is increasing evidence that the intake of microplastics - depending on their size, quantity and composition - could be harmful to organisms, the degree of danger has not yet been finally clarified.
In an experiment over several generations of mosquitoes, the midge was exposed to a concentration of microplastics that can also be found in the environment. This initially showed a loss of fitness in the form of death rates of up to 50 percent. However, an interesting development then began: within three generations, the mosquitoes adapted to absorbing the pollutant, so that there was no longer any difference in survival rates compared to the control group. At the same time, however, changes were registered in their entire genome, which can be interpreted as the reason for this extremely rapid adaptation. In particular, genes involved in fighting inflammation and oxidative stress -- a metabolic imbalance in cells that impairs repair and detoxification functions -- have shown signs of evolutionary adaptation.
Study author Dr. Halina Binde Doria from the LOEWE Center TBG and the SBIK-F classifies the results: "Even if the midges were able to adapt very quickly to the microplastics, this is only partly good news. Because this may not reflect the situation in natural populations and ecosystems. To do this, many different factors have to be taken into account.” On the one hand, the experimental situation may not show all the negative effects of microplastics on survival or the reproduction rate, in short evolutionary fitness. For example, the intake of microplastic particles directly or indirectly affects nutrient absorption in the intestine and can have negative effects in nutrient-poor phases, for example in winter. Adaptation to microplastics can also override important other adaptations, such as controlling the mutation rate. In addition, it is known that not all species can adapt as quickly as the midge. Microplastics would have long-term harmful effects on them.
Study leader Prof. Markus Pfenninger, who also works at the LOEWE Center TBG and the SBiK-F as well as at the Johannes Gutenberg University Mainz, summarizes: “Our study shows that microplastics in the environment have the potential to change the evolutionary development of those exposed to them ways to change forever. Even if there appear to be no direct harmful effects, microplastics pose a threat to all ecosystems that has been underestimated [...].”