Deciphering Microbial Assembly and Coexistence in Rivers Subjected to Long-Term Reclaimed Water Replenishment

Abstract

Reclaimed water recharge into rivers is an important supplementary approach to address water resource shortages in arid and semi-arid areas worldwide. However, the ecology impacts of reclaimed water recharge on the rivers are still unknown, especially for the microbial assemble and species coexistence in different seasons. Here, the evolution of microbiome and its response to different reasons in the Jialu River, which was subjected long-term reclaimed water recharge, is investigated by using 16S rRNA gene sequencing and multivariate statistical methods. The results indicate that microbial communities exhibit significant temporal heterogeneity across different periods and are negatively correlated with river discharge. Their assembly is primarily influenced by stochastic processes such as dispersal limitation and drift. As the transition occurs from the dry season to the normal season, the role of drift diminishes, while the deterministic effects of dispersal limitation and niche selection intensify. The relationships among planktonic bacterial species are primarily positive (cooperative), and the complexity and positive correlations within the ecological network show a trend of first decreasing and then increasing with the change of seasons. Temperature, dissolved oxygen, and ammonia nitrogen are the main driving forces influencing the structure of microbial communities. In summary, these findings provide insights into the impact of seasonal variations on the microbial community patterns in reclaimed water-supplemented river ecosystems.

Keywords: planktonic bacteria, reclaimed water recharge, flood seasons, assembly mechanism, species coexistence