Microbial dynamics and seasonal resilience in constructed wetlands: a scoping review.

Microbial communities in constructed wetlands (CWs) drive wastewater treatment efficacy through pollutant biodegradation and outcompeting of pathogenic taxa. Nevertheless, evidence on the ecological complexity of these communities and the effects of seasonal variability on treatment outcomes remains fragmented across climates and system configurations. This scoping review (ScR) addresses the need to map the available literature on microbial dynamics in CWs and the impact of seasonality on the mitigation of antimicrobial resistance and opportunistic pathogens, to inform future CW applications and environmental pollution management. Database search followed by deduplication and screening yielded 116 relevant records published between 2005 and 2025, spanning 36 countries worldwide, seven wastewater types, ten wetland configurations, and seven molecular detection methods. This ScR pinpoints that: i) microbial communities shift across macrohabitats and treatment stages towards pollutant removal capabilities (Rhodoferax, Polaromonas, Flavobacterium) at the expense of fecal and pathogenic contaminants (Arcobacter, Mycobacterium, Pseudomonas); ii) CWs can achieve >99% removal of carbapenem-resistant bacteria and antimicrobial resistance genes (ermB, bla/sul/tet genes), with the highest overall removal achieved by subsurface flow designs; iii) warmer temperatures can enhance persistence of ARGs by increasing microbial biomass turnover and horizontal gene transfer potential; iv) future environmental pollution management should incorporate long-term AMR monitoring.