Insights into microbial community structure and function from a shallow, simulated CO₂ -leakage aquifer demonstrate...

Area of Science:

• Environmental Microbiology
• Geochemistry
• Biogeochemistry

Background:

• Geological carbon storage is a strategy to mitigate atmospheric carbon dioxide (CO2) release.
• Potential CO2 leakage into freshwater aquifers raises concerns about impacts on microbial communities and ecosystem functions.

Purpose of the Study:

• To investigate the effects of experimental in situ CO2 leakage on a freshwater aquifer microbial community.
• To understand how CO2 exposure influences microbial diversity, community structure, and metabolic functions.

Main Methods:

• High-throughput 16S rRNA gene sequencing to assess microbial diversity and community structure.
• Metagenomic sequencing and population genome binning to determine the metabolic potential of microbial populations.
• Analysis of samples from CO2-exposed wells and a control well.

Main Results:

• Microbial diversity decreased in freshwater wells with CO2 concentrations exceeding 1.15 g L−1.
• Metagenomic analysis revealed microbial populations with the capacity for CO2 utilization, including carbon fixation linked to sulfur and iron oxidation.
• Identification of an archaeal genome with the potential for methanogenesis.

Conclusions:

• CO2 leakage acts as a strong selective pressure on freshwater aquifer microbial communities.
• Leakage alters both the structure and metabolic functions of these microbial communities, affecting key biogeochemical cycles.