Effects of conventional and biodegradable microplastics on earthworm Eisenia andrei in two generations

Summary

Mulching films, used in agriculture, can act as a source of microplastics (MPs) and plastic additives in soils. Due to the persistence of conventional mulching films and the repeated use of biodegradable films, soil organisms are exposed to MPs generation after generation. To study the long-term effects of MPs on functionally important soil invertebrates, we exposed earthworm Eisenia andrei in two generations (7 months) to MPs made of conventional polyethylene (PE-MP) and biodegradable blend of starch and polybutylene adipate terephthalate (PBAT-BD-MP) mulching film materials at concentrations ranging from 0.005 % to 5 %. In the first generation, earthworms exposed to the PE-MP and PBAT-BD-MP at concentrations higher than 0.1 % grew faster compared to the control, but reproduction was not affected. In the second generation, PE-MP decreased reproduction at 5 % and growth in all concentrations, while PBAT-BD-MP increased reproduction and growth at 5 % concentration. The total energy reserves were not affected, but the activity of electron transport system (ETS) decreased at 0.5–5 % concentrations of PBAT-BD-MP in the second generation. The number of ingested MPs increased with increasing exposure concentration. In addition, the soil water holding capacity (WHC) increased and pH value decreased. Our results highlight the long-term ecological risks of microplastics in agricultural soils.