Microbial communities in CO₂-rich springs have adapted to environmental pressure including low pH resulting from high concentrations of CO₂. Microbial community composition and hydrochemical characteristics in the CO₂-rich springs are important features affected by high levels of CO₂ in groundwater ecosystems, and they may be useful indicators of CO₂ leakage from carbon capture and storage (CCS) sites where CO₂ is injected into deep geological reservoirs for the mitigation of climate change. To determine how long-term CO₂ leakage affects the groundwater ecosystems, we analyzed the bacterial and archaeal community composition and hydrochemical features of two different natural CO₂-rich springs, Hansil (HS) and Chosukol (CS), located in south-eastern Korea which are natural analog sites for groundwater ecosystems affected by CO₂ leakage from geological CO₂ storage sites. Analyses of hydrochemical characteristics and 16S rRNA gene amplicon sequencing of bacteria and archaea revealed a marked distinction between the two springs. The pH, the concentrations of bicarbonate ion (HCO₃-), major cations including Ca²⁺ and Mg²⁺, and specific trace elements including Fe and Mn were higher in HS as compared to CS while no distinction in pCO₂ between the two springs was observed. Microbial community composition was distinct between the two springs at the genus level. Specifically, the relative abundance of Gallionella, an iron-oxidizer, was significantly higher in HS whereas that of Albidiferax known as dissimilatory iron-reducing bacteria was higher in CS than HS, reflecting the difference of iron concentration in the two springs. In our study, microbial community composition appeared to be more strongly affected by the concentration of iron than that of CO₂. Our results enhance the understanding of hydrochemical features and microbial communities in natural CO₂-rich springs and suggest that microbial communities may be useful indicators of CO₂ leakage from CCS sites.

富含CO _2的弹簧中的微生物群落已适应环境压力，包括高浓度CO ₂导致的低pH值。在CO微生物群落的组合物和化学特征的₂富弹簧受高水平CO的重要特征₂在地下水的生态系统，并且它们可以是CO的有用的指标₂从碳捕获和储存（CCS）位点泄漏，其中CO ₂是注入深层地质储层以缓解气候变化。确定多长时间的CO ₂渗漏影响地下水生态系统，我们分析了位于韩国东南部的两个天然富含CO _2的天然细菌Hansil（HS）和Chosukol（CS）的细菌和古细菌群落组成以及水化学特征，它们是地下水的天然模拟地受地质CO ₂储存地点泄漏的CO ₂影响的生态系统。对细菌和古细菌的水化学特性和16S rRNA基因扩增子序列的分析表明，这两个弹簧之间存在显着区别。pH值，碳酸氢根离子（HCO _3-）的浓度，包括Ca ²⁺和Mg ²⁺在内的主要阳离子，与铁相比，HS中的特定微量元素（包括铁和锰）更高，而在两个弹簧之间未观察到pCO _2的区别。在属水平上，两个弹簧之间的微生物群落组成是不同的。具体来说，铁氧化物的Gallionella的相对丰度在HS中显着较高，而被称为异化铁还原细菌的Albidiferax在CS中的相对丰度高于HS，反映了两个温泉中铁浓度的差异。在我们的研究中，微生物群落组成似乎受铁浓度的影响比对CO _2的影响更大。。我们的结果加深​​了对富含CO _2的天然温泉中水化学特征和微生物群落的了解，并表明微生物群落可能是CCS站点泄漏CO _2的有用指标。