Effectiveness of the natural bacterial flora, biostimulation and bioaugmentation on the bioremediation of a hydrocarbon contaminated Antarctic soil

Microcosms systems (250 g soil in 1 l flasks) were performed in Jubany Station (King George Island, South Shetland Islands) to analyse biodegradation of gas-oil in Antarctic soils under natural conditions. Abiotic loss of hydrocarbons, biodegradation activity of indigenous microflora and biostimulation with N and P were studied. In addition, biaugmentation with a previously isolated psychrotolerant strain (B-2-2) was analysed. Hydrocarbon concentration, heterotrophic and hydrocarbon-degrading bacterial counts and predominant bacterial groups were evaluated during 51 days. A significant loss of hydrocarbons was observed in abiotic control. Indigenous microflora showed increased heterotrophic counts and hydrocarbon-degrading/heterotrophic ratio. This fact was associated with a significant degrading activity (35% higher than the control). Bioaugmentation with B-2-2 strain improved the bioremediation efficiency (75% of the hydrocarbon was removed). High levels of N and P produced an initial inhibition of bacterial growth. Finally, bacterial diversity was reduced in contaminated soil. Our results showed that autochthonous bacterial flora from Antarctic soils is able to degrade an important fraction of the gas-oil and that bioaugmentation represents a valuable alternative tool to improve bioremediation