Changes in subsurface microbiology following CO2 injection have the potential to impact carbon trapping in CO2 storage reservoirs. However, much remains to be learned about responses of natural microbial consortia to elevated CO2 in basaltic systems. This study asks: how will microbes from deep (700 m) groundwater change along a gradient in CO2 (0–20 psi) in batch reactor systems containing basalt chips and groundwater amended with lactate? Reactors incubated for 87 days at 23 °C. Results for reactors with low CO2 (0 and 3 psi) differed considerably from those with high CO2 (10 and 20 psi). In reactors with low CO2, pH was >6.5 and lactate started to be used within 24 days. By 40 days, lactate was completely consumed and acetate increased to ~4 mM. As lactate was consumed, sulfate decreased from 0.16 to 0 mM after 40 days. In contrast, in reactors with high CO2, pH was <6.5, lactate and sulfate concentrations varied little and acetate was not produced. Biogeochemical modeling and community analyses indicate that differences between reactors with low and high CO2 reflect tolerances of reactor microbes to CO2 exposure. Communities in the low CO2 reactors carried out syntrophic lactate oxidation coupled with methanogenesis and sulfate reduction. Bacteroidota and Firmicutes became dominant phyla after 24 days and groups capable of sulfate reduction and methanogenesis were detected. In reactors with high CO2, however, biogeochemical activity was insignificant, no groups capable of sulfate reducion or methanogenesis were observed, and the community became less diverse during the incubation. These findings show that the response of microbial consortia can vary sharply along a CO2 gradient, creating significant differences in community composition and biogeochemistry, and that the timescale of basalt weathering is likely not rapid enough to prevent significant stress following a rapid increase in CO2 abundance.
Bibliographical noteFunding Information:
This research was supported by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources (KIGAM) funded by the Ministry of Science and ICT of Korea and the Korea University Grant.
© 2021 Elsevier B.V.
- Biogeochemical modeling
- Hydrogenotrophic methanogenesis
- Microbial community
- Syntrophic lactate oxidation
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal