Degradation of petroleum hydrocarbons in two sub-antarctic soils: Influence of an oleophilic fertilizer

In order to determine the long‐term effects of fertilizer on the degradation rate and the toxicity of hydrocarbons in sub‐Antarctic soils contaminated by petroleum hydrocarbons, a field study was initiated in December 2000 on two different soils of the Kerguelen Islands (69°42′E, 49°19′S). The number of hydrocarbon‐degrading bacteria (HDB) increased greatly after crude‐oil and diesel‐fuel contamination, and the fertilizer addition had a favorable effect on HDB growth and activity. Hydrocarbon‐degrading bacteria counts remained high until the end of the experiment although the total hydrocarbon content in all contaminated soils was reduced to 80 to 90% of their initial value after 330 d. Degradation of n‐alkanes was enhanced significantly in the presence of the fertilizer, while the degradation of polycyclic aromatic hydrocarbons (PAHs) was only barely enhanced. Toxicity results showed a noticeable reduction with time, although toxicity remained present and important in both soils at the end of the experiment. In addition, fertilized plots showed a toxic signal greater than unfertilized ones. Overall results clearly show that fertilizer addition improves the rate of degradation of both oil contaminants. However, remaining toxic residues may constitute a drawback of the fertilizer‐assisted biodegradation process at low temperatures.