Resilience and resistance of a pristine aquifer towards toluene contamination – impact assessment using microbes and elucidation of factors limiting natural attenuation.

The resistance and recovery potential of an oligotrophic groundwater ecosystem towards organic impact is still unknown. In this thesis, the response of a pristine groundwater model system to toluene input and its recovery was studied. The system revealed a spontaneous aerobic degradation within 63 hours, being limited by transport processes on later stages. After depletion of toluene and the fast recovery of redox conditions, the microbial community composition remained altered. We conclude that aerobic hydrocarbon degraders are omnipresent and can respond fast. However, anaerobic degradation constrained by transport limitations of oxygen and other electron acceptors, need more than 63 days to become significant