Impacts of conventional and biodegradable microplastics in maize-soil ecosystems: Above and below ground

Abstract

The increasing accumulation of microplastics (MPs) in agroecosystems has raised significant environmental and public health concerns, facilitating the application of biodegradable plastics. However, the comparative effects of conventional and biodegradable MPs in agroecosystem are still far from fully understood. Here we developed microcosm experiments to reveal the ecological effects and risks of conventional (polyethylene [PE] and polypropylene [PP]) and biodegradable (polyadipate/butylene terephthalate [PBAT] and polycaprolactone [PCL]) MPs (0, 1%, 5%; w/w) in maize-soil ecosystems. We found that PCL MPs reduced plant production by 73.6-75.2%, while PE, PP and PBAT MPs elicited negligible change. PCL MPs decreased soil biomass-related enzymes activities critical for nutrients cycling by 71.5-95.3%. Biodegradable MPs tended to reduce bacterial α-diversity. The 1% of PE and PBAT, and PCL enhanced bacterial networks complexity, whereas 5% of PE and PBAT, and PP had adverse effect. Differently, biodegradable MPs appeared to reduce the α-diversity and networks complexity of fungal community. Overall, PCL reduced the ecosystem multifunctionality, mainly by inhibiting the microbial metabolic activity. This study offers evidence that biodegradable MPs can impair agroecosystem multifunctionality, and highlights the potential risks to replace the conventional plastics by biodegradable ones on a large scale in agricultural practices.