Temporal Dynamics of In-Field Bioreactor Populations Reflect the Groundwater System and Respond Predictably to...

Area of Science:

• Environmental microbiology
• Geochemistry
• Microbial ecology

Background:

• Temporal variability in environmental conditions complicates the study of microbial community structure and function.
• Understanding in situ microbial responses to geochemical factors is crucial for environmental applications.

Purpose of the Study:

• To develop and utilize an in-field bioreactor system to assess the impact of oxic versus anoxic conditions on groundwater microbial communities.
• To correlate microbial community shifts with changes in biogeochemical parameters like dissolved oxygen (DO) and pH.

Main Methods:

• An in-field bioreactor system was deployed to manipulate dissolved oxygen (DO) levels in situ.
• Groundwater microbial communities were analyzed using 16S SSU rRNA gene sequencing.
• Biogeochemical parameters including metals, organic acids, anions, and sugars were quantified.

Main Results:

• Microbial communities fluctuated in response to DO and pH changes, mirroring in situ groundwater dynamics.
• Two distinct groups of operational taxonomic units (OTUs) were identified: one associated with high DO/pH (including heterotrophs and oxidizers) and another with low DO (nitrate reducers).
• A null model indicated that both experimental conditions and stochastic variability influenced bioreactor communities.

Conclusions:

• In-field bioreactors are effective tools for studying natural microbial community responses to geochemical alterations.
• Dissolved oxygen and pH are key drivers of groundwater microbial community structure and function.
• Microbial community composition is influenced by both deterministic (geochemical factors) and stochastic processes.