Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies

Area of Science:

• Geomicrobiology
• Environmental Science
• Subsurface Biogeochemistry

Background:

• Sediment physical properties define lithofacies and influence subsurface microbial communities.
• Spatial distribution of lithofacies presents an opportunity to predict microbial attributes.
• Biogeochemical facies (oxidized, reduced, transition) are key to understanding microbial ecology.

Purpose of the Study:

• Characterize biogeochemical facies within a lithofacies.
• Elucidate relationships between facies features and microbial community attributes (biomass, richness, composition).
• Develop a predictive model for microbial biomass concentration based on facies distribution.

Main Methods:

• Characterization of three biogeochemical facies: oxidized, reduced, and transition.
• Analysis of microbial community biomass, richness, and composition in relation to facies.
• Null modeling to assess ecological selection pressures (redox state, mineralogy).
• Spatial prediction of microbial biomass using coupled facies distribution and biomass-facies relationships.

Main Results:

• Elevated microbial biomass observed in the transition zone between oxidized and reduced facies.
• Microbial richness was lower in reduced facies, correlated with pH and mineralogy.
• Ecological selection, driven by redox state and mineralogy, influenced microbial community composition.

Conclusions:

• Biogeochemical facies significantly control subsurface microbial community structure and biomass.
• Predictive modeling of microbial biomass is feasible by integrating facies distribution and established relationships.
• This approach can reduce uncertainty in hydro-biogeochemical models by constraining simulated dynamics.