Microbial processes in the deep biosphere of the active CO2-dominated fault zone in NW Bohemia

The Cheb Basin (CZ) is a shallow neogene intracontinental basin filled with fluvial and lacustrine sediments. The central and northern parts of the seismic active rift are characterized through diffuse degassing of mantle-derived CO2 in form of so-called mofettes. The Hartoušov mofette field shows the highest CO2 flux and soil gas concentration among those mofettes. The aim of the present study was to characterize the influence of elevated CO2 concentrations on the geochemistry and microbial community of soil and sediment from the mofette. Two 3 m drillings were performed, one located in the centre of the degassing structure and the other 8 m away served as an undisturbed reference. The sites were compared in terms of their physical and geochemical features, microbial abundances (qPCR), community structures (Illumina 16S rDNA amplicon sequencing) and methanogenic activity.