[Shift of Microbial Communities During the CO₂-Brine-Sandstone Interaction Process]

Area of Science:

• Microbiology
• Geochemistry
• Environmental Science

Background:

• Investigating microbial community dynamics is crucial for understanding subsurface processes.
• Carbon dioxide (CO2) injection for storage can significantly impact indigenous microbial ecosystems.
• Sandstone-brine interactions under CO2 influence microbial structure, function, and biodiversity.

Purpose of the Study:

• To investigate the dynamic changes in indigenous microorganisms during CO2-brine-sandstone interactions.
• To assess the impact of CO2 injection on microbial structure, functionality, and biodiversity.
• To explore the potential role of these microorganisms in CO2 capture and storage.

Main Methods:

• MiSeq sequencing techniques were employed to analyze microbial community structure.
• Analysis included assessing species abundance, diversity (Shannon index), and functional potential.
• Geochemical parameters like pH and brine composition were monitored.

Main Results:

• CO2 injection led to a significant reduction in microbial biodiversity (Shannon index decreased from 5.3302 to 1.9465).
• Microbial communities shifted towards a single dominant species, with Proteobacteria reaching 99.77% relative abundance.
• Key genera identified include *Pseudomonas*, *Citrobacter*, *Brevundimonas*, *Bacillus*, *Hydrogenophaga*, and *Rhizobium*.
• Functional analysis revealed bacteria capable of iron reduction, denitrification, and enhancing CO2 solubility-trapping.
• Microbial metabolism accelerated feldspar and chlorite dissolution, facilitating calcite and siderite formation.

Conclusions:

• Indigenous microorganisms can adapt to extreme conditions created by CO2 injection.
• Specific bacterial groups, particularly Proteobacteria, dominate post-CO2 injection.
• Microbial functionalities, including iron reduction and denitrification, alongside metabolic processes, show potential for enhancing CO2 capture and storage.
• Changes in pH and brine chemistry are primary drivers of microbial community variation.