Microbial Signatures in Deep CO2-Saturated Miocene Sediments of the Active Hartoušov Mofette System (NW Czech Republic)

Abstract

The Hartoušov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system.

Microbial diversity and community dynamics in an active, high CO2subsurface rift ecosystem

“…Similar to Liu et al [20], we detected methanogenic Euryarcheota, as especially Methanobacterium and Methanosarcina signatures were identified across almost the entire length of the analyzed core. While relative abundances were highest in shallow and intermediate sediments down to 110 m, their presence in deeper samples suggest the potential for methanogenic activity to persist throughout.…”

“…Nevertheless, we identified taxa with these functional traits throughout the examined samples, suggesting this unique environmental feature to have somewhat of an impact on the ecology. Similar to previous studies from high CO 2 environments [11,67,68], including the Eger subsurface [20,32], we frequently identified taxa belonging to the Comamonadaceae family. While the Comamonadaceae contain a diverse group of water and soil bacteria, the here discovered genera Acidovorax, Rhodoferax, Hydrogenphaga, and Curivbacter have all been detected in high CO 2 environments [12,13,69,70], and have been suggested to fix or utilize CO 2 or H 2 in their likely mixotrophic lifestyle [11,71].…”

“…the aim to evaluate whether the increased fluid and substrate flow can accelerate microbial life in active fault zones and CO 2 conduits [20,22].…”

“…Large diversity highlights importance of archaeal communities One of the most important goals of this study, was to evaluate the presence and diversity of Archaea, as the Eger subsurface has been hypothesized to provide methanogenic substrates, H 2 and CO 2 through frequent swarm earthquake activity [18,19,22], with primary production through methanogenic archaea providing the basis for secondary heterotrophic lifestyle by bacteria. Previous studies have detected Archaea in Cheb Basin subsurface sediments [20] and mofette and spring waters from the region [32]. These efforts primarily detected Euryarchaea signatures, and especially in sediment samples archaea communities were low in abundance and diversity.…”

Circular Metagenome-Assembled Genome of Methanobacterium sp. Strain ERen5, a Putative Methanogenic, H 2 -Utilizing Terrestrial Subsurface Archaeon

“…With frequent seismic activity and consistently high CO 2 fluxes, the Eger Rift in Western Bohemia ( 1 ) represents a rare subsurface ecosystem and a scientifically relevant location to study microbial behavior and biological-geological interactions in the deep subsurface ( 2 – 4 ). Seismic activity in this region has been suggested to release H 2 , thereby promoting the production of biogenic methane through methanogenic Archaea ( 5 ).…”