The influence of temperature on bacterial assemblages during bioremediation of a diesel fuel contaminated subAntarctic soil

Full-scale in situ remediation of diesel-contaminated soils has not yet been used in Antarctica. This is partly because it has been assumed that temperatures are too low for effective biodegradation. To challenge this idea, the effects of temperature on the hydrocarbon mineralisation rate have been quantified during mesocosms, biopiles and field pilot studies carried out on an artificially contaminated subAntarctic soil. Field studies were initiated in December 2000 in a selected soil of The Grande Terre (Kerguelen Archipelago, 69° 42′E– 49° 19′S). Four experimental plots (0.75 × 0.75 m) were settled firmly into the studied soil. Each plot received 500 mL of diesel fuel and two of them were covered with a black plastic sheet. All plots were regularly sampled over a one-year period. Under natural subAntarctic conditions, the field tests revealed that up to 95% of the contaminants were degraded within one year, indicating that low temperatures (0–7 °C) can still accommodate oil biodegradation by indigenous microorganisms. Covering the soil with plastic sheets induced a small but permanent increase of the temperature in the surface soil (annual mean of + 2.2 °C). The microbial response was improved by this bioremediation treatment. Mesocosm studies and pilot biopile experiments confirmed that a constant heating of soil could be an effective mean to accelerate bioremediation of diesel-contaminated subAntarctic soils. However, the microbial response was always improved by a complementary fertilizer addition.