Effect of Polycaprolactone Microplastics on Soil Microbial Communities and Plant Growth

Microplastics (MPs), especially those of biodegradable plastic origin, have received sufficient attention. However, the effects of polycaprolactone (PCL) microplastics on soil microbial communities and plant growth have not been fully explored. The study aimed to evaluate the effect of MPs on soil microbial communities and plant growth. We performed 16 S rDNA high-throughput sequencing to analyze the soil bacterial composition after exposure to different concentration PCL-MPs(0.02, 0.2 and 2%, W/W) for 30 days. Additionally, we conducted pot experiments to investigate the effect of soil with PCL-MPs on the growth of oilseed rape and lettuce. According to α-diversity analysis, the presence of PCL-MPs did not have an impact on the structure and diversity of the soil microbial community, and there was no significant difference in microbial communities between soils containing different with varying concentrations of PCL-MPs based on β-diversity analysis. However, the relative abundance of Proteobacteria decreased and Acidobacteria increased in soils with low and medium concentrations of PCL-MPs. Despite this change, the dominant species (Actinobacteria, Acidobacteria, Proteobacteria, and Chloroflexi) remained unchanged in each sample in terms of relative abundance and order. The pot experiments revealed that that PCL-MPs caused a temporary decrease in soluble protein in the leaves of both oilseed rape and lettuce, but this effect disappeared over time. The chlorophyll levels in both plants were not significantly affected by PCL-MPs. However, there was a significant difference in MDA levels, with no effect on oilseed rape but a reduction in lettuce. PCL-MPs also caused a decrease in POD in both plants. Based on these results, it can be concluded that PCL-MPs do not have an impact on soil microbial communities and the growth of oilseed rape and lettuce.