Diversity and functional traits of microbial communities in the terrestrial subsurface habitat along a climatic gradient: from surface into the weathering front at depth

• Applicants: Professor Dr. Thomas Friedl; Professor Dr. Dirk Wagner
• Subject Area: Palaeontology
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409277596

Goal of the project is to assess the diversity and functional traits of microbial communities in the subsurface critical zone (CZ) of terrestrial habitats across an aridity gradient, i.e. the EarthShape transect in the Coastal Cordillera in Chile. It will be tested whether (1) the terrestrial subsurface habitat of the CZ is connected with the surface habitat and, therefore, influenced by climatic conditions. The Earth’s Critical Zone (CZ) is a thin living layer connecting atmosphere and geosphere. It is increasingly impacted by human activities. The subsurface part of CZ with the weathering zone is an active part of the “deep biosphere” which comprises of habitats deep beneath the Earth’s surface. It is among the most poorly understood habitats of the earth. Weathering processes transform hard and biologically inert bedrock to a friable weathered rock which is a hospitable substrate for organisms and from which soil develops. Therefore, weathering of rock is crucial for the support of life on earth, as it delivers nutrients to organisms. Rock-linked life forms may occupy essential key roles in shaping the earth to support life. Further, the project will investigate (2) whether species diversity and the abundance of microbial weathering processes related with it increase at the deep weathering front. The microbial communities at the saprolite-bedrock interface (weathering front) may share a phylogenetic origin with (non-photoautotrophic) organisms from rock surfaces, whereas the communities associated with weathering processes in the saprolite have their origin in soil microbial communities. (3) Prokaryotic and eukaryotic microorganisms may form a network that mainly drives the mineral dissolution at the weathering front and in deep saprolite profiles. Deep taxonomic insights at the level of species will be realized by an amplicon-based meta barcoding DNA sequencing approach using paired-end reads. Various functional gene sequences will be employed to infer functional traits of the microbial communities, i.e. to determine the abundances and phylogenetic diversities of biomass production and mineral weathering activities. A novel sophisticated DNA extraction protocol to separate intracellular DNA of active cells from the extracellular DNA pool and DNA of dormant stages (bacterial endospores) will be used. These efforts support evaluating the hypothesis that the advancement of weathering fronts across the EarthShape transect is a recent feature and still evolving today. The project will take advantage of the drilling campaign proposed by the DeepEarthshape package, i.e. to drill a core through soil and saprolite into the unweathered bedrock at the four study sites along the aridity gradient.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1803: EarthShape: Earth Surface Shaping by Biota