Sulfate and pH drive microbial assembly and coexistence in hyporheic zone contaminated by acid coal mine drainage

Abstract

Overflow of Acid Mine Drainage (AMD) from coal mining poses critical ecological restoration challenges to the surrounding water, sediment and soil. However, little is known about the assembly processes and coexistence patterns of microbial communities in AMD-contaminated rivers. Therefore, by using high-throughput sequencing combined with multivariate statistical analysis, the seasonal dynamics of microbial distribution, community assembly, and coexistence patterns in the Shandi River, a river seriously polluted by overflowed AMD were revealed. The results indicated that the patterns of contamination, community assembly and coexistence in high- and low-contaminated areas showed similar patterns in both two seasons. The levels of hydrogen ion, sulfate and heavy metals increased from low-contaminated areas toward high-contaminated areas. Microbial diversity and community structure significantly differed along the river. Acidiphilium and Ferrimicrobium, which were capable of thriving in environments with high acidity and sulfate levels, were predominant in high-contaminated areas. Stochastic processes predominantly influenced microbial assembly in low-contaminated areas, while deterministic processes were more pronounced in high-contaminated areas. Meanwhile, negative interactions in microbial co-occurrences, were more frequent in high-contaminated areas with increased network modularity. Linear regression analysis results demonstrated that pH and sulfate were significantly correlated with biodiversity indicators, βNTI and closeness centrality, and determined as the primary drivers of microbial community structure and assembly processes. These findings highlight the crucial role of sulfate content and pH in shaping microbial diversity, community assembly, and species coexistence in coal AMD-contaminated areas.