Microbial functional genes can be used as indicators of soil health in response to fuel spills in Antarctica

Several fuel spills have occurred near Australia’s Antarctic stations, associated with the use of SAB diesel for power generation. This has resulted in significant petroleum hydrocarbon contamination in soils. Successful remediation of fuel spills requires knowledge of the impact of hydrocarbons on the soil ecosystem. Microorganisms play an integral role the normal functioning of soils, and are useful indicators of soil health. In this study, microorganisms were used to assess the toxicity of hydrocarbons in Antarctic soils. qPCR was used to measure the numbers of microbial genes responsible for a range of soil processes (alkane monooxygenase, catechol 2 3-dioxygenase, nitrous oxide reductase and nitrogenase reductase) in response to both fresh and aged fuel contamination. Soil was freshly spiked with a range of concentrations of SAB. A clear dose-response relationship between hydrocarbon concentration and the numbers of total microorganisms, alkane degraders and denitrifiers (measured by the rpoB, alkB and nosZ genes respectively) was observed. Additionally, alkane degraders dominated the community in soils containing higher concentrations of hydrocarbons. Soils collected at a contaminated site at Casey Station currently undergoing in-situ remediation were diluted with clean soils to create a natural aged contamination gradient. A similar trend in gene numbers was observed in these soils, although this relationship was less clear. Data obtained in this study will be used to advise remediation activities and to monitor in-situ progress, and will be incorporated into the development of targets that define trigger-points and set end points for remediation.