, 2009). Its relative pristine status makes it an interesting site for investigating the biodegradation of PAHs by indigenous microorganisms in these soils without any history of exposure to lignin, PAHs or similar compounds. Indigenous PAHs have been previously investigated (Aislabie et al., 2000, 2006; Ferguson et al., 2003a, b; Coulon et al., 2005) in Antarctic and sub-Antarctic soils, but these studies have been performed on potentially

contaminated soils with high levels of soil PAHs concentration, from areas impacted by Antarctic settlements and scientific stations. To our knowledge, no direct biodegradation measurements have been carried out in soils with extremely low this website amounts of PAHs, such as those collected from different sites of Livingstone Island and used in this study. In the present paper we investigate the degradation of 14C-phenanthrene by indigenous

soil microorganism in soil samples from Livingstone Island at different temperatures. Phenanthrene (> 99.6%), and [9-14C] phenanthrene (specific activity = 50 mCi mmol−1, Bleomycin radiochemical purity > 95%) standards were obtained from Sigma Aldrich, UK. Chemicals for the minimal basal salts (MBS) solution were obtained from BDH Laboratory Supplies and Fisher Chemicals. The liquid scintillation cocktail (Ultima Gold) and glass scintillation vials (7 mL) were obtained from Canberra Packard, UK. Sodium hydroxide was obtained from Sigma Aldrich. Dichloromethane, hexane and methanol were supplied

by Merck, Darmstad, Germany. Agar-agar and plate count agar were obtained from Oxoid Ltd, UK. Soil samples were collected from background areas of Livingstone Island. A map with the sampling sites is provided in Fig. 1. The top 5 cm were taken using a stainless steel corer. Samples were frozen (−20 °C) in sterile glass Teicoplanin jars for transportation to Lancaster University. Soil physicochemical properties are shown in Table 1. Soil redox, soil pH and soil moisture content were measured by standard methods described elsewhere(Cabrerizo et al., 2011). Particle size analysis was determined according to the method by Gee and Bauder (1979) and calculations according to Gee and Bauder (1979). Total carbon and nitrogen were determined by analysing 4 mg of oven-dried (105 °C) and sieved (2 mm) soil samples on a Carlo Erba CHNS-OEA 1108 CN-Elemental analyser. For total organic carbon (TOC) analysis, soils were heated to 430 °C to remove all organic carbon, the ash containing inorganic carbon alone was measured on the analyser and the TOC determined by mass balance (Rhodes et al., 2007). Extraction and quantification: Briefly, 30 g of soil samples were homogenized and dried by mixing with anhydrous sodium sulphate and ground using a mortar and a pestle.