Exposure of soil collembolans to microplastics perturbs their gut microbiota and alters their isotopic composition

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 (similar to 44%), Bacteroidetes (similar to 30%), Proteobacteria (similar to 12%) and Firmicutes (similar to 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 delta N-15 and delta C-13 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.