A group of Finnish researchers traced carbon atoms in polyethylene from bodies of water to when they enter the food chain, and discovered that they can be used as a source of nutrition

What is the fate of microplastics? From tiny plastic fragments that could be harmful to the environment and to the health of living beings, to “good” components of the food chain, thanks to the activity of certain microorganisms. According to the authors of a study recently published in Scientific Report, this seems to be the pathway, which is surprising in many ways, of the carbon atoms contained in microplastics. 

“Increasing abundance of microplastics in marine and freshwaters is currently one of the greatest environmental concerns,” explain the authors, led by Sami Taipale from the University of Jyväskylä, Finland. “Plastics are designed to be resistant to chemical decomposition, and reutilization of MP carbon requires microbial carbon removal,” they add, pointing out that only a few studies so far have assessed the fate of microplastic carbon in the food chain. To explore the topic in greater depth, Taipale and colleagues evaluated the ability of different communities of microorganisms to reuse the carbon atoms in microplastics, by first experimenting with polyethylene (one of the most common types of plastic) in which the carbon atoms were “marked” and therefore traceable on a molecular level. 

“Eating” microplastics

Analyses have revealed that microplastic carbon is partially assimilated and used for cell growth, and assimilation is greater in the case of bacteria derived from so-called humic water, where there are substances that are difficult to decompose and use. Going further along the food chain, the researchers observed that some algae and zooplankton species use carbon that microorganisms have derived from microplastics to form the fatty acids in their cells. 

But that’s not all. Starting from microplastic carbon, aquatic microorganisms can synthesize essential fatty acids, such as Omega 3 and Omega 6, by feeding these atoms into the food chain within nutritionally important biomolecules. 

“These results show that the biodegradation of microplastics is now a reality in aquatic environments and that the atoms of such microplastics become part of the biomolecules valuable to the organisms living in these environments,” the experts conclude.