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Spatio-temporal patterns of microbial communities in a hydrologically dynamic pristine aquifer
Yuxiang Zhou1, Claudia Kellermann, Christian Griebler
1Institute of Groundwater Ecology, Helmholtz Zentrum München, German Research Center for Environmental Health, GmbH, Neuherberg, Germany.
FEMS Microbiology Ecology
|March 29, 2012
Summary
Seasonal hydrological changes significantly impact alpine groundwater microbial communities, reducing bacterial diversity in spring and summer. Sediment microbial communities, however, remained stable throughout the year.
Area of Science:
- Environmental Microbiology
- Aquatic Ecology
- Geomicrobiology
Background:
- Alpine aquifers experience significant seasonal hydrological shifts due to snowmelt and precipitation.
- Groundwater microbial communities are sensitive to environmental changes, including water table fluctuations and nutrient availability.
- Sediment-water interfaces in aquifers can act as important microbial habitats.
Purpose of the Study:
- To investigate the seasonal dynamics of microbial communities in groundwater and sediments of a dynamic alpine aquifer.
- To understand the influence of hydrological fluctuations on microbial diversity and abundance.
- To compare the stability of indigenous sediment microbial communities with those colonizing introduced sterile sediments.
Main Methods:
- Time-resolved sampling of groundwater and sediment from monitoring wells in an alpine porous aquifer.
- Total bacterial DNA extraction and analysis using T-RFLP (Terminal Restriction Fragment Length Polymorphism) for community fingerprinting.
- Measurement of bacterial cell densities and Shannon diversity index (H') in groundwater and sediments.
- Incubation of sterile and riverbed sediments in monitoring wells to assess colonization and stability.
Main Results:
- Groundwater bacterial Shannon diversity (H') significantly decreased from 3.22 ± 0.28 (autumn/winter) to 1.31 ± 0.35 (spring/summer) with rising groundwater levels.
- Elevated bacterial numbers in autumn groundwater correlated with nutrient inputs and high concentrations of assimilable organic carbon.
- Sterile sediments incubated in wells were colonized, reaching bacterial densities and diversity comparable to natural riverbed sediments after one year.
- Microbial communities in riverbed sediments remained largely unchanged in composition, diversity, and cell numbers during the year-long incubation.
Conclusions:
- Seasonal hydrological dynamics, particularly snowmelt-driven water table rise, profoundly impact groundwater microbial community structure and diversity in alpine aquifers.
- While groundwater microbial communities exhibit high seasonal variability, sediment microbial communities appear more stable and resilient.
- Aquifer sediments serve as a stable habitat, supporting microbial communities that can recover or establish similar diversity and biomass to natural environments over time.
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