Distinct ecological patterns of abundant and rare prokaryotic taxa across sediment and water habitats in an acid mine drainage-impacted river system.

Acid mine drainage (AMD) can lead to severe pollution of surrounding aquatic systems like rivers. Although microbial ecosystems have been documented in the AMD-impacted riverine systems, the ecological patterns and potential assembly mechanisms of abundant and rare taxa are still largely unexplored. Herein, we examined the diversity, composition, co-occurrence networks and assembly of the whole prokaryotic communities, abundant taxa, and rare taxa along an AMD-impacted river. The results revealed a strong correlation between prokaryotic communities and environmental variables in the AMD-impacted river. Significant spatial variations in diversity and composition were observed for the whole community and abundant taxa in sediment habitats, but not in water habitats. Specifically, in sediment habitats, the relative abundances of Gamma- and Beta-proteobacteria decreased along the river, while Alphaproteobacteria and Acidobacteriota increased. Conversely, water habitats were characterized by Acidovorax and Acidocella. Furthermore, the alpha diversity of rare taxa showed no significant correlation with spatial distance in either sediment or water habitats. However, rare taxa occupied important topological positions in the co-occurrence network. Stochastic processes (dispersal limitation and undominated processes) generally dominated community assembly especially for rare taxa, but the roles of deterministic processes (heterogeneous and homogeneous selection) in shaping whole communities and abundant taxa of sediment habitats should not be neglected. These findings offer novel insights into microbial patterns and assembly mechanisms in AMD-impacted riverine ecosystem.