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Homogeneous Environmental Selection Structures the Bacterial Communities of Benthic Biofilms in Proglacial Floodplain
Jade Brandani1, Hannes Peter1, Stilianos Fodelianakis1
1River Ecosystems Laboratory, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Applied and Environmental Microbiology
|February 27, 2023
Summary
Microbial communities in glacier-fed streams are shaped by homogeneous selection, with specific bacterial clades thriving across different stream types. Future warming may alter these communities as habitats become greener.
Area of Science:
- Microbial ecology
- Environmental microbiology
- Glacial ecosystem dynamics
Background:
- Proglacial floodplains exhibit environmental gradients due to glacier recession, influencing microbial biodiversity in stream biofilms.
- Understanding the selective forces shaping these microbial communities is crucial, especially in rapidly changing high-mountain ecosystems.
Purpose of the Study:
- To investigate bacterial community assembly processes in proglacial streams by identifying ecologically successful phylogenetic clades.
- To determine the relative importance of environmental constraints versus spatial structuring in biofilm community formation.
Main Methods:
- Comparative analysis of bacterial communities in glacier-fed mainstems and non-glacier-fed tributaries across three Swiss Alps proglacial floodplains.
- Identification of bacterial clades with low phylogenetic turnover rates and assessment of their abundance and distribution.
- Correlation analysis between the proportion of bacteria under homogeneous selection and photoautotroph abundance.
Main Results:
- Specific bacterial clades, including Gammaproteobacteria and Alphaproteobacteria, showed low phylogenetic turnover and were present across all stream types.
- These successful clades constituted significant portions of community diversity and relative abundance in both mainstems and tributaries.
- The abundance of bacteria under homogeneous selection was inversely related to photoautotroph abundance, suggesting a future shift with ecosystem 'greening'.
Conclusions:
- Homogeneous selection plays a dominant role in structuring bacterial communities in proglacial biofilms, alongside nested, spatially structured assembly processes.
- Environmental differences between glacier-fed and tributary streams impose distinct selective pressures.
- Future climate warming and increased primary production may lead to shifts in bacterial community composition in these dynamic ecosystems.
