Microbial Communities in Terrestrial CO2 Springs: Insights into the Long-Term Effects of Carbon Sequestration on Subsurface Microorganisms

Abstract:

Over long timescales, microbial populations and communities living in environments where CO₂ has been sequestered will adapt to this environmental stress. Their presence and activities can have implications for fluid flow, geochemistry, and the fate of the stored CO₂. Because of the interplay between microorganisms and environment, many environmental factors beyond CO₂ will also contribute to community structure, including groundwater composition and mineralogy. To determine the long-term effect of CO₂ on microbial communities, we analyzed terrestrial CO₂ springs as analogues to CO₂ sequestration in 3 locations in the United States: the Little Grand Wash Fault (LGW), UT; Bravo Dome (BD), NM; and Klickitat Mineral Spring (KMS), WA. These sites differed in multiple aspects such as depth, salinity, Fe content, and mineralogy. LGW and BD were located in the Colorado Plateau in sedimentary locations while KMS was located within the Columbia River Basalt Group. Sites were compared to non-CO₂ springs in similar sedimentary formations for comparison. Microbial communities from sedimentary formations were characterized by low diversity and the dominance of the phylotypes Acinetobacter or Burkholderia compared to non-CO₂ springs, suggesting community stress and the selection of specific organisms most resilient to CO₂. Communities in the basalt formation were more diverse, though diversity is lower than a non-CO₂ community sampled from the same formation (Lavalleur and Colwell 2013). Organisms present at the basalt site contained novel lineages, such as the OP candidate phyla. KMS was also the only site containing Archaea, such as Methanoplanus, suggesting CH₄ production at depth. Statistical analyses indicate other factors such as depth and nutrient availability may be other factors that can affect diversity in addition to CO₂. Growth of a CO₂-tolerant organism from LGW also shows organisms in these environments are viable. Results confirm the presence of microbial communities at high PCO₂ and suggest that while CO₂ is one environmental stress that can lower diversity, many other environmental factors can also influence survival.

Lavalleur, H.J., Colwell, F.S., 2013. Microbial characterization of basalt formation waters targeted for geological carbon sequestration. FEMS Microbiology Ecology 85, 62-73.