Geomicrobiology of Antarctic Subglacial Environments - Subglacial Lake Whillans
Latest version published by SCAR - Microbial Antarctic Resource System on Apr 21, 2015 SCAR - Microbial Antarctic Resource System
Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years,but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW)lies beneath approximately 800m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes that can mobilize elements from the lithosphere and influence Southern Ocean geochemical and biological systems.
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Researchers should cite this work as follows:
Christner BC, Priscu JC, Achberger A, Barbante C, Carter SP, Christianson K, Mikucki JA,Michaud AB, Mitchell A, Skidmore ML, Vick-Majors TJ, and the WISSARD Science Team. 2014. A microbial ecosystem beneath the West Antarctic Ice Sheet. Nature. 512:310-313.
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Subglacial Lake Whillans; Antarctic; subglacial; geomicrobiology; microbiology; bacteria; archaea; Metadata
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Samples were collected from Subglacial Lake Whillans, at the lower portion of the Whillans Ice Stream, West Antarctica. Samples were collected through a 800m borehole created with a clean, hot water drill system.
|Bounding Coordinates||South West [-85.02, -155.33], North East [-83.79, -131.77]|
Planktonic microbial cells were collected on 0.2, 0.8, 3.0, and 10.0 micron filters and community structure was determined from 16S rRNA gene identities. Microbial community structure was also determined for samples from a shallow sediment core (0-40 cm).
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|Title||Whillans Ice Stream Subglacial Access Research and Drilling - Geomicrobiology of Subglacial Lake Whillans|
|Funding||The Whillans Ice StreamSubglacial Access Research Drilling (WISSARD) project was funded by National Science Foundation grants (0838933, 0838896, 0838941, 0839142, 0839059, 0838885, 0838855, 0838763, 0839107, 0838947, 0838854, 0838764 and 1142123) from the Division of Polar Programs. Partial support was also provided by funds from NSF award 1023233 (B.C.C.), NSF award1115245(J.C.P.), the NSF’s Graduate Research FellowshipProgram(1247192; A.M.A.), the Italian National Antarctic Program (C.B.), and fellowships from the NSF’s IGERT Program(0654336) and the Montana Space Grant Consortium (A.B.M.)|
|Study Area Description||Water and sediments of Subglacial Lake Whillans, located 800 meters beneath the surface of the Whillans Ice Stream, West Antarctica.|
|Design Description||A hot water drilling system was used between 23–27 January 2013 to melt through the ~801 m thick ice sheet, creating an access borehole (minimum diameter ~60 cm) for direct sampling and to conduct in situ measurements of the SLW water column and sediments. Microbial cells in the drilling water and on exposed surfaces of the hose, cables, and deployed equipment were reduced and killed through the use of four complementary technologies: (1) filtration, (2) ultraviolet irradiation, (3) pasteurization, and (4) disinfection with 3% w/v H2O2. The drilling water, derived from the overlying ice sheet, was continuously circulated through a water treatment system that removed micron and sub-micron sized particles (>0.2 μm), irradiated the drilling water with two germicidal wavelengths of ultraviolet radiation (185 nm ~40,000 µW s−1 cm−2 and 254 nm ~175,000 µW s−1 cm−2), and pasteurized the water at 90 °C to reduce the viability of persisting microbial contamination. Ports were plumbed along the system’s flow path, allowing discrete water samples to be obtained before and after each stage. The drill hose and instrument cables were deployed at a rate no greater than 1 m s−1 through a custom borehole collar that contained 12 amalgam pellet ultraviolet lamps, providing a cumulative germicidal ultraviolet dosage of at least 40,000 µW s−1 cm−2 (Arapahoe SciTech). All borehole sampling tools and instruments were spray-saturated with 3% w/v H2O2 and staged in sealed polyethylene bags until tool deployment. Single-use protective apparel (Tyvek) was worn by all personnel during borehole science operations. The efficacy of the clean access technology and procedures were tested thoroughly before use in the field.|
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Water samples were collected and brought to the surface in Niskin bottles. Particulate matter for DNA sequence analyses was collected on 10.0, 3.0, 0.8, and 0.2 micron filters by an in situ filtration unit. Sediment samples were collected and brought to the surface using a shallow sediment multicorer. See Christner, et al 2014 for details.
|Study Extent||See Geographic Coverage|
|Quality Control||Paired end sequence reads were assembled and quality filtered using the Mothur phylogenetic analysis pipeline (v1.33.2). The sequences were aligned with the SILVA Incremental Aligner47 (SINA v1.2.11; database release 115). The aligned reads were checked for chimaeras using the Uchime algorithm, as implemented within Mothur, and chimaeric sequences were removed from the data. Sequences with >97% SSU rRNA gene sequence similarity were clustered into an OTU and representative sequences for each OTU were chosen for classification using the SILVA database.|
Method step description:
- Descriptions can be found in Christner et al., 2014.