Hydrogeochemical Constraints Shape Hot Spring Microbial Community Compositions: Evidence From Acidic, Moderate‐Temperature Springs and Alkaline, High‐Temperature Springs, Southwestern Yunnan Geothermal Areas, China

Abstract

AbstractEnvironmental factors (e.g., temperature and pH) shaping the distribution of microbial communities in hot springs have been extensively studied, whereas how hydrochemical formation mechanisms and hydrological circulation processes affect microbial community composition is not comprehensively elucidated. In the present study, hydrochemical, isotopic, and high‐throughput sequencing methods were employed to investigate hydrochemical characteristics and evolution of springwater as well as their underlying roles in shaping the microbial community in multiple acidic and alkaline hot springs in southwestern Yunnan, China. Distinct hydrochemical (e.g., pH, temperature, sulfate, SiO2, and trace metals) and isotopic (δ2H and δ18O) characteristics revealed the recharge sources and circulation processes of springwater were different in alkaline, high‐temperature and acidic, moderate‐temperature hot springs. Two acidic, moderate‐temperature springs (43°C–55°C), characterized by high sulfate, showed shallow circulation depths and were potentially heated by upwelling hot, high H2S abundance gases, and sulfur oxidation might be one of the main underlying hydrochemical processes. Seven alkaline, high‐temperature springs (>70°C), in contrast, which originated from a different recharge source as indicated by the lighter isotopic compositions (δ2H and δ18O), showed characteristics of deeper circulation. Hydrogenobacter sp. is the most abundant microorganism in alkaline, high‐temperature springs, whereas acidic, moderate‐temperature springs are mainly composed of Chlorobiaceae, Thiomonas sp., Halothiobacillus sp., Sulfurihydrogenibium sp., and Hydrogenobaculum sp. which have been reported to possess the potentials to cycle sulfur. The hydrochemical constraints on shaping microbial communities may help us better understand biogeochemical cycles across a range of temperatures in acidic and alkaline springs.