Successional dynamics of microbial communities in response to concentration perturbation in constructed wetland system

[Display omitted] •CWs showed a capacity of adapting to a wide range of influent COD perturbation.•Pollutant-removal of CWs experienced a transition from fluctuation to stability.•Influent COD perturbation promoted the inner environmental changes of CWs.•Rhizosphere stimulated the occurrence of Trichococcus in assisting organic shock.•Rhizosphere microorganisms competed for their niches when subjected to organic. Constructed wetlands (CWs) are widely considered as resilient systems able to adapt to environmental perturbations. Little attention has been paid, however, to microbial dynamics when CWs withstand and recover from external shock. To understand the resilience of CWs, this study investigated rhizosphere microbial dynamics when CWs were subjected to influent COD perturbation (200 mg/L-1600 mg/L). Results demonstrated that CWs had strong adaptability to different influent perturbations, characterized by transitions from fluctuating to stable pollutant removal. Microbial analysis showed that rhizosphere microorganisms competed for niches in response to increased COD concentrations, and Trichococcus played key roles in resisting concentration perturbations. Structural equation modeling indicated that rhizosphere community succession and microbial energy metabolism were shaped by pH and DO. These findings provide insights into the mechanism for CW stability maintenance when facing concentration perturbations.