Effects of different earthworm species on the remediation efficiency of BaP-contaminated soils and microbial community structure

Benzo[ a ]pyrene a representative high-molecular-weight PAH, accumulates persistently in soils due to its strong carcinogenicity and environmental recalcitrance, posing long-term ecological risks. Although earthworm-assisted remediation is considered a promising and eco-friendly biostimulation strategy, remediation performance among different earthworm species in BaP-contaminated soils and the associated microbial regulatory mechanisms remain insufficiently compared. In this study, soil microcosms contaminated with BaP were established and incubated for 30 d to comparatively evaluate the remediation performance of four earthworm species ( Eudrilus eugeniae , Eisenia fetida , Lumbricus rubellus , and Pheretima guillelmi ). BaP removal efficiency, bioaccumulation characteristics of earthworms, and changes in soil physicochemical properties and enzyme activities were comprehensively assessed. In addition, 16S rRNA high-throughput sequencing combined with microbial co-occurrence network analysis was applied to characterize microbial communities in soils and earthworm guts. The results showed pronounced interspecific differences in BaP remediation performance. Among the tested species, E. fetida and P. guillelmi significantly enhanced BaP removal from soil during the incubation period, while maintaining relatively high survival rates and bioaccumulation capacities. Earthworm introduction markedly reshaped soil microbial community structure, with significant enrichment of key BaP-removal genera, including Flavobacterium and Sphingomonas , in the E. fetida and P. guillelmi treatments. Microbial co-occurrence network analysis further revealed higher network connectivity in these treatments, as indicated by significant increases in average degree and network density. Overall, this study demonstrates that E. fetida and P. guillelmi exhibit greater remediation adaptability and stability in BaP-contaminated soils, providing valuable guidance for earthworm species selection and practical application of earthworm-based remediation strategies at PAHs-contaminated sites.