Injection-based microbially induced carbonate precipitation: soil improvement and restructuring of native microbial communities

Abstract Purpose Microbially induced carbonate precipitation (MICP) is increasingly applied as an environmentally oriented soil-improvement technique; however, its ecological effects on native soil microbial communities remain insufficiently understood. This study investigated injection-based MICP for soil improvement and the associated restructuring of soil microbial communities. Methods A soil column experiment employing a two-phase injection strategy was conducted to investigate the effects of cementation solution (CS) concentration, nutrient addition, and injection cycles. Soil improvement performance was evaluated through CaCO₃ content (CC), permeability, mineral characterisation and physicochemical measurements. Microbial diversity, taxonomic composition and community-environment relationships were characterised using 16 S rRNA gene sequencing and exploratory multivariate analyses. Results CC increased from approximately 4.1% to 11.1–14.4% following MICP treatment, accompanied by substantial reductions in soil permeability. Higher CS concentration, nutrient addition and more injection cycles enhanced carbonate precipitation, although nutrient addition also increased its spatial heterogeneity. Microbial diversity decreased following repeated injection, and community restructuring became more pronounced with higher CS concentration and more injection cycles. Although the dominant phyla were generally retained across treatments, their relative abundances shifted substantially, particularly with the enrichment of Bacillota . Community restructuring was primarily associated with two contrasting physicochemical gradients represented by CC and electrical conductivity (EC), indicating that both carbonate precipitation and injection-associated physicochemical changes contributed to microbial community structuring. Conclusions Injection-based MICP caused substantial short-term restructuring of soil microbial communities. This restructuring involved both changes in the relative abundances of dominant phyla and differences in phylogenetic lineage occurrence, and was primarily associated with the combined influence of carbonate precipitation and physicochemical changes accompanying repeated injection. These findings highlight the need to balance engineering effectiveness with consideration of microbial ecology, providing an empirical basis for the development of ecology-aware geotechnical design.