Effects of microplastics on aquatic organisms have been widely studied in recent years but effects on soil biota, and especially on the gut microbiota of soil animals, remain poorly understood. An experiment was therefore conducted using the common soil collembolan Folsomia candida exposed to microplastics for 56 days to investigate the effects of plastics on gut microbiota, growth, reproduction and isotopic turnover of collembolans in the soil ecosystem. A diverse microbial community was observed in the collembolan gut, consisting of (at phylum level) Actinobacteria (～44%), Bacteroidetes (～30%), Proteobacteria (～12%) and Firmicutes (～11%). Distinctly different bacterial communities and lower microbial diversity were found in the collembolan gut compared with the surrounding soil. We also found that exposure to microplastics significantly enhanced bacterial diversity and altered the microbiota in the collembolan gut. Moreover, collembolan growth and reproduction were significantly inhibited (by 16.8 and 28.8%, respectively) and higher δ¹⁵N and δ¹³C values were observed in the tissues after exposure to microplastics. These results indicate that exposure to microplastics may impact non-target species via changes in their microbiota leading to alteration of isotopic and elemental incorporation, growth and reproduction. The collembolan gut microbial data acquired fill a gap in our knowledge of the ecotoxicity of microplastics.

A significant difference in bacterial families was observed between the collembolan gut and the soil. When family level annotation of microbiota was not possible the order was selected denoted by (o). Families with >1% relative abundance in the collembolan gut and the soil are presented.