Bioremediation of diesel oil contaminated subAntarctic soils (Crozet Island)

An accidental contamination occurred in the subAntarctic Crozet Island between July and November 1997 near the "Alfred Faure" scientific station (51degrees 51'E- 46degrees 25'S). More than 20 000 L of diesel fuel were spilled in the soil in the direct vicinity of the power station. A field study was initiated in 1999 with the objective of determining the long-term effects of some bioremediation agents on the biodegradation rate and the toxicity of oil residues under severe subAntarctic conditions. In order to evaluate bioattenuation efficiency, the contaminated area was sampled in December 1999 and bacteria were enumerated. All samples were analysed for total bacteria, heterotrophic viable assemblages and hydrocarbon utilising microflora. The results of this first analytical survey clearly show a significant response of subAntarctic microbial soil communities to hydrocarbon contamination. Significant increases of total, hetrotrophic and hydrocarbon utilizing bacteria occurred in the more contaminated zone (from less than 5 x 104 MPN ("Most Probable Number") g(-1) to more than 10(8) MPN g(-1) for hydrocarbon degrading bacteria). The very high numbers of hydrocarbon-degrading bacteria present in the more contaminated zone are probably an indication of bioattenuation activities. However, biostimulation treatments may accelerate the restoration of the contaminated soils. A bioremediation treatement of the contaminated area by addition of a slow release fertilizer (Inipol EAP-22, Elf Atochem) and temperature elevation (agricultural plastic sheets) will begin in January 2001.