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Project Progress

The hot-water drilling apparatus and sampling mechanism used during the 2006 expedition to the western Skaftárkatlar subglacial lake has been described in a paper submitted to the Icelandic glaciological journal Jökull and a paper that appeared in the Journal of Glaciology. Data on the temperature profile and geochemistry of the lake water column has been analyzed and interpreted in a paper in review in Geophysical Research Letters. The paper has passed through one round of minor revisions and we expect acceptance for publication. We are also making progress in analyzing our single water sample using molecular biological techniques. We have completed cell counts based on DNA-staining of intact cells. We have also categorized the cells as bacteria or archaea using a suite of general oligonucleotide-fluorophore probes in the technique of fluorescent in situ hybridization (FISH), showing that the lake?s microbial community consists almost entirely of bacteria with few or no archaea. We have also carried out partial sequencing of two clone libraries constructed from a fragment of the 16S ribosomal RNA gene amplified using PCR: These libraries suggest an extremely low diversity community consisting of phylotypes related (by sequence) to cultivated psychrotolerant organisms capable of acetogenesis, sulfur reduction, and ferric iron reduction. This indicates a lake ecosystem based on using hydrogen to reduce CO₂, sulfur, and ferric iron to produce energy and is consistent with our geochemical data indicating high amounts of CO₂, sulfide, and detectable but unknown concentration of H₂. Further sequencing of these libraries has been completed, as well as 454 pyrosequencing of the V6 hypervariable region of the ribosome, and we used highly-specific FISH probes to enumerate some of the species heavily represented as phylotypes in our clone libraries. This research results to date have been described in talks given at the fall meeting of the AGU in San Francisco, the Volcano-Ice Interactions Workshop 2 in Vancouver, Canada,the Society for Molecular Biology and Evolution meeting in Halifax, Canada, and a seminar at Cal Berkeley; a manuscript describing the biology results is also in preparation.

An Iceland team jointly supported by Science Foundation of Iceland and NASA Astrobiology funds successfully sampled the eastern Skaftÿrkatlar lake in June of 2007. Two boreholes were drilled for sampling and a total of 8 one-liter water samples were obtained from different depths; this represents a 20-fold increase in total sample volume over the previous expedition. Like the western lake, the eastern lake is covered by nearly 300 m of ice and is about 100 m deep; the samples are also anoxic/sulfidic. Cell counts are approximately equal to that in the western lake. Detailed analysis of these samples is now getting underway in Iceland.