ABSTRACT
The presence of active and diversified microbial communities down to 1000 m depths or more in Baltic shield groundwater is well established. A series of different projects has been accomplished during the last decade, aiming at understanding the fate of oxygen in a deep (500 m) high level radioactive waste repository and processes of importance for the redox situation in deep groundwater. The general conclusion from these projects is that microbes will dominate oxygen removal and control redox processes.
