Thorough studies of samples from deep boreholes, using a variety of molecular techniques, have shown an active biosphere composed of diverse groups of microorganisms. Since microorganisms represent very effective geochemical catalysts, the investigation of their distribution and physiology could be of great importance for the process of CO2 storage. In the frame of the EU Project CO2SINK a field laboratory to study CO2 storage into saline aquifer is operated. Our studies aim at the monitoring of biological and biogeochemical processes and their impact on the technical effectiveness of CO2 storage technique. Interactions between microorganisms and the minerals of both the reservoir and the cap rock may cause major changes to the structure and chemical composition of the rock formations, which may influence the permeability within the reservoir. In addition, precipitation and corrosion may occur around the well affecting casing and cement. Moreover, the growth of microorganisms on the material surface (biofilms) can have a profound effect on material performance. Therefore, analyses of the composition of microbial communities and its changes should contribute to an evaluation of the effectiveness and reliability of the long-term CO2 storage, e.g. speed up of mineralisation. In order to investigate processes in the deep biosphere that will occur between injected supercritical CO2, the rock substrate and the microorganisms, the PCR SSCP method (Single-Strand-Conformation Polymorphism) and FISH method (Fluorescence in situ Hybridisation) were used. The identification and quantification of microorganisms enables the correlation to metabolic classes and provides information about the biochemical processes in the deep biosphere. Although saline aquifers could be characterised as an extreme habitat for microorganisms due to reduced conditions, high pressure and salinity, high numbers of diverse groups of microorganisms were found. The deep biosphere community was dominated by the haloalkalifilic fermentative bacteria (Halomonas, Halolactibacillus, Halobacteroides), extremophilic organisms like Deinococcus, and sulphate reducing bacteria (Desulfosporosinus, Desulfotomaculum, Desulfohalobium). Of great importance was the identification of sulphate reducing bacteria, which are known to be involved in corrosion processes. Microbial monitoring during CO2 injection has shown that microbial communities were strongly influenced by the CO2 injection. In addition, microbial communities revealed high adaptability to the changed environments after CO2 injection. Further analyses of the microbial community using PCR-DGGE (Denaturing Gradient Gel Electrophoresis) as well as 16S rRNA molecular cloning of the complete gene are in progress.


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