Dynamics of Denitrifying Anaerobic Methane Oxidizing Archaea in River Networks: Activity, Community Structure, and Assembly Process

The denitrifying anaerobic methane oxidizing archaea (DAMO archaea) plays a key role in mitigating methane emissions in river ecosystems, but its activity, community structure, and assembly process under different hydrological conditions remain poorly understood. This study investigated the dynamics of DAMO archaea in river networks (Taihu basin) across wet, normal, and dry seasons. Microcosm incubation with 13C-CH4 was employed to determine the potential activity of DAMO archaea. The potential methane oxidation rates varied from 0.22 to 2.19 nmol 13C-CO2·g–1·d–1, with the wet season exhibiting significantly higher rates than other seasons (p < 0.0001). Further, amplicon sequencing revealed that the diversity and community structure of DAMO archaea also showed seasonal dynamics. The neutral community model and normalized stochasticity model were employed to investigate the community assembly process influenced by seasonal dynamics. Both deterministic and stochastic factors shaped DAMO archaeal communities, with the wet season showing notably higher stochasticity compared with other seasons. Co-occurrence network analysis demonstrated that DAMO archaeal communities exhibited the lowest robustness and greatest vulnerability in the wet season, indicating their instabilities in this season. This study highlighted the dynamics of DAMO archaeal communities in river ecosystems and offered new insights into the underlying mechanisms.