Subsurface microbial communities as a tool for characterizing regional-scale groundwater flow.

Area of Science:

• Environmental microbiology
• Hydrogeology
• Geochemistry

Background:

• Subsurface microbial communities are influenced by groundwater flow and geochemistry.
• Understanding these connections is crucial for characterizing groundwater systems.

Purpose of the Study:

• To examine the regional-scale microbial community of the Death Valley Regional Flow System (DVRFS).
• To evaluate the utility of subsurface microbial communities in identifying groundwater-flow paths between recharge and discharge areas.

Main Methods:

• Collected samples from 36 sites across three groundwater basins (PMOV, AM, AFFCR).
• Analyzed microbial diversity and community structure using network and null model analyses.
• Integrated microbial data with hydrologic, geologic, and water-chemistry information.

Main Results:

• Microbial communities separated into two main groups, correlating with groundwater basins (AM and PMOV/AFFCR).
• Network analysis corroborated known hydraulic connections between recharge and discharge areas.
• Null model analyses indicated deterministic and stochastic processes shape microbial assemblages, with dispersal limitation and geochemical differences being key factors.

Conclusions:

• Microbial community analysis supports established hydraulic connections within the DVRFS.
• This approach demonstrates the value of integrating microbial data with other hydrogeologic information for comprehensive groundwater system characterization.
• Limitations include potential well-associated artifacts affecting sample interpretation.