Abstract
Since the first descriptions of Antarctic subglacial lakes, there has been a growing interest and awareness of the possibility that life will exist and potentially thrive in these unique and little known environments. The unusual combination of selection pressures, and isolation from the rest of the biosphere, might have led to novel adaptations and physiology not seen before, or indeed to the potential discovery of relic populations that may have become extinct elsewhere. Here we report the first microbiological analysis of a sample taken from a former subglacial lake sediment in Antarctica (Lake Hodgson, on the Antarctic Peninsula). This is one of a number of subglacial lakes just emerging at the margins of the Antarctic ice sheet due to the renewed onset of deglaciation. Microbial diversity was divided into 23.8% Actinobacteria, 21.6% Proteobacteria, 20.2% Planctomycetes and 11.6% Chloroflexi, characteristic of a range of habitat types ( Overall, common sequences were neither distinctly polar, low temperature, freshwater nor marine). Twenty three percent of this diversity could only be identified to “unidentified bacterium”. Clearly these are diverse ecosystems with enormous potential.
Highlights
Since the first descriptions of Antarctic subglacial lakes [1,2], there has been a growing interest and awareness in the possibility that life will exist and potentially thrive in these unique and little known environments
Lake Vostok beneath the Eastern Antarctic plateau [6], Lake Ellsworth beneath more than 3 km of ice near the ice divide in the Ellsworth mountains [7,8,9] and the Whillans Ice Stream near the coast in the Ross Sea region [10]. It was in preparation for the direct access and sampling of Lake Ellsworth, that we sampled the subglacial sediment from Lake Hodgson, a former subglacial lake emerging from the margins of the Antarctic Peninsula Ice Sheet
Microbial counts direct from the pore water gave a minimum cell density of >10 3 DAPI stained cells mL−1 which was equivalent to 5 × 104 cells g−1 wet sediment
Summary
Since the first descriptions of Antarctic subglacial lakes [1,2], there has been a growing interest and awareness in the possibility that life will exist and potentially thrive in these unique and little known environments. Having demonstrated that subglacial lakes beneath the Vatnajökull ice cap in Iceland hosted endemic communities of microorganisms adapted to cold, dark and nutrient-poor waters, Marteinsson et al [18] extended this study to include samples of two related Icelandic subglacial lakes, a subglacial flood and a lake that was formerly subglacial but partly exposed to the atmosphere They found that the dominant taxa were closely related to cultivated anaerobes and microaerobes, and suggest that they might occupy unique metabolic niches in a chemoautolithotrophic ecosystem. Based on the sequence data, they speculated that the lake appeared to contain a mixture of autotrophs and heterotrophs capable of performing nitrogen fixation, nitrogen cycling, carbon fixation and nutrient recycling All such studies have contributed significantly to a growing awareness of glacial ice as an ecosystem, yet direct access, sampling and analysis of an Antarctic subglacial lake ecosystem has only just been achieved. For the first time, we describe the microbiological analyses of an Antarctic subglacial lake sediment using a range of complementary technologies
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