Spatial and temporal groundwater biogeochemical variability help inform subsurface connectivity within a...

Area of Science:

• Deep subsurface microbiology
• Hydrogeology
• Geomicrobiology

Background:

• Deep terrestrial subsurface ecosystems remain largely uncharacterized due to access challenges.
• Understanding these environments is crucial given their vast extent beneath Earth's landmasses.

Purpose of the Study:

• To establish and utilize the BedrettoLab Deep Life Observatory (DELOS) for studying deep groundwater biogeochemistry.
• To investigate the spatial and temporal diversity and connectivity of microbial communities in an Alpine subsurface environment.

Main Methods:

• Established the DELOS underground laboratory in a high-altitude Alpine catchment.
• Conducted spatial and temporal biogeochemical monitoring of groundwater from tens of meters to 1.6 km depth.
• Analyzed microbial community composition and hydrochemical parameters.

Main Results:

• Identified three dominant groundwater ecotypes: shallow (Leptospirillia), fault zones (ultra-small microbes), and bicarbonate-rich waters (Candidatus Kryptonia, Spirochaetota).
• Observed significant heterogeneity in groundwater composition between nearby fractures, with some showing greater similarity to distant sites.
• Demonstrated relative stability of microbial and hydrochemical groundwater composition over one year, with rapid recovery after seismic events.

Conclusions:

• Deep subsurface groundwater ecosystems exhibit complex spatial heterogeneity and connectivity.
• The DELOS provides a unique platform for advancing the study of deep life.
• Subsurface microbial communities show resilience and can recover baseline conditions post-disturbance.