Complexity involved in the transport of soils and the restrictive legislation for the area makes on‐site bioremediation the strategy of choice to reduce hydrocarbons contamination in Antarctica. The effect of biostimulation (with N and P) and bioaugmentation (with two bacterial consortia and a mix of bacterial strains) was analysed by using microcosms set up on metal trays containing 2·5 kg of contaminated soil from Marambio Station. At the end of the assay (45 days), all biostimulated systems showed significant increases in total heterotrophic aerobic and hydrocarbon‐degrading bacterial counts. However, no differences were detected between bioaugmented and nonbioaugmented systems, except for J13 system which seemed to exert a negative effect on the natural bacterial flora. Hydrocarbons removal efficiencies agreed with changes in bacterial counts reaching 86 and 81% in M10 (bioaugmented) and CC (biostimulated only) systems. Results confirmed the feasibility of the application of bioremediation strategies to reduce hydrocarbon contamination in Antarctic soils and showed that, when soils are chronically contaminated, biostimulation is the best option. Bioaugmentation with hydrocarbon‐degrading bacteria at numbers comparable to the total heterotrophic aerobic counts showed by the natural microflora did not improve the process and showed that they would turn the procedure unnecessarily more complex.

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Several studies have shown that biostimulation can promote hydrocarbon bioremediation processes in Antarctic soils. However, the effect of the different nutrient sources on hydrocarbon removal heavily depends on the nutrients used and the soil characteristics. In this work, using a sample of chronically contaminated Antarctic soil that was exposed to a fresh hydrocarbon contamination, we analyzed how a complex organic nutrient source such as fish meal (FM) and a commercial fertilizer (OSEII) can affect hydrocarbon biodegradation and bacterial community composition. Both amended and unamended (control) biopiles were constructed and controlled at Carlini Station and sampled at days 0, 5, 16, 30 and 50 for microbiological, chemical and molecular analyses. FM caused a fast increase in both total heterotrophic and hydrocarbon degrading bacterial counts. These high values were maintained until the end of the assay, when statistically significant total hydrocarbon removal (71 %) was detected when compared with a control system. The FM biopile evidenced the dominance of members of the phylum Proteobacteria and a clear shift in bacterial structure at the final stage of the assay, when an increase of Actinobacteria was observed. The biopile containing the commercial fertilizer evidenced a hydrocarbon removal activity that was not statistically significant when compared with the untreated system and exhibited a bacterial community that differed from those observed in the unamended and FM-amended biopiles. In summary, biostimulation using FM in biopiles significantly enhanced the natural hydrocarbon-degradation activity of the Carlini station soils in biopile systems and caused significant changes in the bacterial community structure. The results will be considered for the future design of soil bioremediation protocols for Carlini Station and could also be taken into account to deal with dieselcontaminated soils from other cold-climate areas.

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SummaryThe plant-assisted removal of phenol, with special emphasis on the effects of this compound on some plant's physiological parameters, was investigated. Hydroponic cultures of alfalfa (Medicago sativa L., var. Romagnola) were employed as a model system. These cultures were exposed to two phenol concentrations: 100 and 500 mg/l. A first order kinetic approach was used to describe the removal of phenol from the solution. After 30 days of cultivation, the initial amount of phenol (100 mg/l) was reduced to non-detectable levels in the presence of plants. In the absence of plants, 20% of phenol remained in the solution. The half-life of phenol was reduced from 7.2 to 4.5 days in the presence of plants. After 25 days, the initial amount of 500 mg/l of phenol was reduced to non-detectable levels in the presence of plants not previously exposed to phenol and to approximately 20% with plants previously exposed to the contaminant. In the absence of plants, almost 40% remained in the solution. The presence of plants reduced the half-life of phenol from 18.3 days to 10.4 in the case of plants previously exposed and to 7.8 days in the case of plants without previous contact. Chlorophyll contents in alfalfa leaves of plants exposed to 100 mg/l of phenol were similar to those of control plants and a decrease in total chlorophyll content was observed when plants were exposed to 500 mg/l of phenol. The activity of soluble peroxidases of the roots increased in the presence of 100 mg/l of phenol but the amount of 500 mg/l had a negative effect on the peroxidase fraction. No changes were observed in the case of the ionically-bound cell wall fraction. The growth index of the plants exposed to 100 mg/l of phenol was comparable to that of non-exposed plants, while this parameter was negatively affected in the case of plants exposed to 500 mg/l of phenol. Although alfalfa plants were able to survive an exposure to 500 mg/l of phenol, their physiological parameters and their removal capacity were negatively affected.

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