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SUBGLACIAL LAKE WHILLANS: a MICROBIAL ECOSYSTEM BENEATH DEEP ANTARCTIC ICE. Brent C. Christner1, John C. Priscu2, Amanda M. Achberger1, Carlo Barbante3, Alexander B

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SUBGLACIAL LAKE WHILLANS: a MICROBIAL ECOSYSTEM BENEATH DEEP ANTARCTIC ICE. Brent C. Christner1, John C. Priscu2, Amanda M. Achberger1, Carlo Barbante3, Alexander B Astrobiology Science Conference 2015 (2015) 7133.pdf SUBGLACIAL LAKE WHILLANS: A MICROBIAL ECOSYSTEM BENEATH DEEP ANTARCTIC ICE. Brent C. Christner1, John C. Priscu2, Amanda M. Achberger1, Carlo Barbante3, Alexander B. Michaud2, Jill A. Mikucki4, Andrew C. Mitchell5, Alicia M. Purcell4, Mark L. Skidmore6, Trista J. Vick-Majors2, and the WISSARD Science Team. 1Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA [[email protected]], 2Department of Land Resources and Environmental Science, Montana State University, Bozeman, MT, USA, 3Institute for the Dynamics of Environmental Processes – CNR, Venice, and Department of Environmen- tal Sciences, University of Venice, Venice, Italy, 4Department of Microbiology, University of Tennessee, Knoxville, TN, USA, 5Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK, 6Department of Earth Science, Montana State University, Bozeman, MT, USA Introduction: There is a large liquid water rese- gen, iron, or sulfur compounds as energy sources. The voir beneath the Antarctic ice sheet (~107 km3) and profusion of taxa related to bacterial and archaeal nitri- ~400 subglacial lakes have been identified in West and fiers in concert with elevated ammonium and ∆17O- East Antarctica. Dark chemosynthetic microbial eco- NO3 values in the water column implied that nitrifica- systems have been proposed to exist at subzero tem- tion may be a fundamental chemoautotrophic pathway peratures at the ice sheet bed [1-3], but direct observa- of new organic carbon production in SLW [6]. tions are lacking. Here we provide results from the first analysis of water and surficial sediments collected Discussion: These new data indicate that envi- directly from a subglacial lake beneath the West Ant- ronments beneath the world’s major ice sheets support arctic ice sheet using microbiologically clean drilling viable ecosystems and corroborate previous reports and sampling techniques. suggesting that subglacial microbial communities can Subglacial Lake Whillans (SLW) lies beneath ~800 mobilize elements from the lithosphere and influence m of ice on the lower portion of the Whillans Ice marine geochemical and biological systems. Given the Stream in West Antarctica and is part of an extensive prevalence of subglacial water in Antarctica, we con- and evolving hydrological system. The subglacial tend that aquatic microbial ecosystems are common drainage network regulates water transport to the sub- features of the sub-ice environment that exists beneath ice coastal margin beyond the grounding line, linking the Antarctic ice sheet. the hydrological system to the sub-ice-ocean cavity Antarctic subglacial lakes have been repeatedly beneath the Ross Ice Shelf [4]. The drilling location to identified as the most promising terrestrial analogs for access SLW was selected using reflection seismology the habitability of icy worlds beyond earth [7]. The and ice-penetrating radar data, and corresponded to the scientific exploration of subglacial lakes also presents region of maximum predicted water column thickness, similar technological and scientific challenges and lowest hydropotential, and largest satellite-measured shares many of the same concerns about forward con- surface elevation changes. tamination as astrobiological studies of other planetary bodies. The sampling and analysis of a sub-ice aquatic Results: During January 2013, a hot water drill environment experiencing long-term isolation from was used to create a ~0.6 m diameter borehole through solar energy and atmospheric input not only has the overlying ice sheet into SLW, allowing for direct broadened our understanding of Earth’s biosphere, it measurements in the water column and the collection has provided new information that will aid in defining of discrete water and and sediment samples [5]. The the limits and survivability of of life in the sub-ice ~2.2 m water column of SLW contained metabolically oceans of Europa, Enceledus, Ganymede, and Titan. active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic References: [1] Christner et al. (2006) Limnol weathering and a minor seawater component. The wa- Oceanogr, 51, 2485–2501. [2] Christner et al. (2008) ter showed oxygen under-saturation (~2 mg L-1; ~ 17% Bacterial in subglacial environments, In: Psychro- of air saturation) and N:P molar ratios implied a bio- philes: From Biodiversity to Biotechology, Springer. logically nitrogen deficient environment, relative to [3] Priscu et al. (2008) Antarctic Subglacial Water: phosphorus [6]. Origin, Evolution and Microbial Ecology. In: Polar Chemoautotrophic primary production in SLW was Limnology, Oxford University Press. [4] Fricker et al. adequate to support heterotrophic metabolism in the (2007) Science, 315, 1544-1548. [5] Tulaczyk et al. subglacial ecosystem. The most abundant phylotypes (2014) Annal Glaciol, 55, 51-58. [6] Christner et al. in the SLW water column were most closely related to (2014) Nature, 512, 310–313. [7] Priscu & Hand chemolithoautotrophic species that use reduced nitro- (2012) Microbe, 7, 167-172. .
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