Bacterial diversity, co-occurrence networks, and assembly processes differed between sediment and water in alpine karst springs of the Baiyi Basin, southwest China

Water and sediment bacterial communities in karst springs exhibit close linkages yet pronounced differentiation. However, comprehensive studies on the differences in bacterial community structures between water and sediment habitats in alpine karst springs are lacking. To investigate the differences in bacterial community diversity, co-occurrence networks, and assembly processes between sediment and water in alpine karst springs, 53 samples were collected from Baiyi Basin in Yunnan, southwestern China. Our results indicated that bacterial communities differed significantly in taxonomic composition, α-diversity, and β-diversity between the water and sediment compartments in karst springs. Sediment bacterial communities exhibited significantly higher α-diversity than their water counterparts, and distinct clustering between sediment and water bacterial communities was also observed. Total phosphorus (TP) and total organic carbon (TOC) were identified as the strongest predictors of α-diversity in sediment and water communities, respectively, while water-soluble salts (WSS) and pH were the primary determinants of community structure in sediment and water habitats, respectively. The bacterial co-occurrence network in sediments showed higher topological complexity and connectivity, thus demonstrating enhanced stability than the water bacterial network. Deterministic processes, especially homogeneous selection, governed the assembly of sediment bacterial communities, while stochastic processes dominated the assembly of water bacterial communities. Total nitrogen (TN) and Ca 2+ were the best predictor of assembly processes of the sediment and water bacterial communities, respectively. This study addresses a significant knowledge gap regarding bacterial communities in both water and sediment from karst springs, and provides theoretical insights for maintaining ecosystem stability and ensuring drinking water safety in karst regions.