Microbial community dynamics and its relationship with biogeochemical processes under geochemical perturbations

Environmental microbial communities are crucial in regulating ecosystem functions and are increasingly affected by human-induced geochemical perturbations. While microbial communities are known to shift under such perturbations, the explicit link between these shifts and corresponding biogeochemical processes remains unclear. Here, we conducted time-series sediment incubation experiments under elevated nitrate conditions, combining 16S rRNA gene sequencing, qPCR, and metagenomics to track microbial taxonomic and functional dynamics. We further developed a gene-centric, process-based biogeochemical model to quantitatively connect microbial community structure to geochemical reaction kinetics. Our results revealed that functional metagenomics provided a broader view of functional diversity than qPCR and enabled detailed analysis of gene co-occurrence. Through modeling, we uncover a quantitative coupling between functional gene abundance and reaction rates under geochemical perturbations. However, this relationship can be obscured by redox-driven abiotic processes affected by perturbations and the nonlinear nature of enzyme-mediated reactions, making it difficult to resolve using standard statistical approaches. Together, these findings improve our understanding of the linkage between microbial function and biogeochemical processes, and underscore the value of gene-centric, process-based models for predicting ecosystem behavior under geochemical stress.