Unlocking the Secrets of Saline Lakes: How Environmental and Microbial Interactions Shape Protodolomite Formation

Protodolomite formation in saline lakes remains enigmatic, despite favorable conditions for dolomite precipitation. To unravel this mystery, sediment samples were collected from two saline lakes in northeastern Inner Mongolia: Jibuhulangtu Nuur (JBHLT) and Dabusan Nuur (DBS). These samples were subjected to comprehensive analysis, including mineral composition detection, measurement of physicochemical variables, analysis of extracellular polymeric substances (EPS), and 16S rRNA sequencing. Results showed that protodolomite was exclusively observed in JBHLT, even though both lakes were supersaturated with respect to dolomite. Microbial communities in JBHLT were dominated by Gammaproteobacteria and Desulfuromonadia . Polysaccharide in EPS extracted from sediments was significantly enriched in JBHLT and positively correlated with microbial alpha diversity. pH was found to be the main factor significantly impacting microbial community composition, diversity, and functions. In DBS, increased pH led to the dominance of Halanaerobiaeota , while decreased microbial diversity and polysaccharide contents. The interplay of pH, microbial community structure, and sediment EPS content concurrently impacts protodolomite formation. Our findings highlight the interaction between environmental conditions and microbial communities and their consequence in terms of protodolomite mineralization.