Investigating the hydrological origins of Blood Falls – geomicrobiological insights into a briny subglacial Antarctic aquifer

Tuesday, 15 December 2015: 15:25
2008 (Moscone West)
Jill Mikucki1, Slawek M Tulaczyk2, Alicia M. Purcell1, Bernd Dachwald3, William B Lyons4, Kathleen Ann Welch5, Esben Auken6, Hilary A Dugan7, Jake Walter8, Erin C Pettit9, Peter T Doran10, Ross A Virginia11, Cyril Schamper12, Neil Foley13, Marco Feldmann3, Clemens Espe3, Dhritiman Ghosh1, Gero Francke3 and MIDGE-EnEx Science Team, (1)University of Tennessee, Knoxville, TN, United States, (2)University of California Santa Cruz, Earth and Planetary Sciences, Santa Cruz, CA, United States, (3)FH Aachen, Aachen, Germany, (4)Ohio State University Main Campus, Columbus, OH, United States, (5)Ohio State Univ, Columbus, OH, United States, (6)Aarhus University, Institute for Geoscience, Aarhus, Denmark, (7)University of Wisconsin, Madison, WI, United States, (8)Institute for Geophysics, Austin, TX, United States, (9)University of Alaska Fairbanks, Fairbanks, AK, United States, (10)Univ Illinois at Chicago, Chicago, IL, United States, (11)Dartmouth College, Hanover, NH, United States, (12)Sorbonne Universités, Paris, France, (13)University of California Santa Cruz, Santa Cruz, CA, United States
Subglacial waters tend to accumulate solutes from extensive rock-water interactions, which, when released to the surface, can provide nutrients to surface ecosystems providing a ‘hot spot’ for microbial communities. Blood Falls, an iron-rich, saline feature at the terminus of Taylor Glacier in the McMurdo Dry Valleys, Antarctica is a well-studied subglacial discharge. Here we present an overview of geophysical surveys, thermomechanical drilling exploration and geomicrobiological analyses of the Blood Falls system. A helicopter-borne transient electromagnetic system (SkyTEM) flown over the Taylor Glacier revealed a surprisingly extensive subglacial aquifer and indicates that Blood Falls may be the only surface manifestation of this extensive briny groundwater. Ground-based temperature sensing and GPR data combined with the helicopter-borne TEM data enabled targeted drilling into the englacial conduit that delivers brine to the surface. During the 2014-15 austral summer field season, we used a novel ice-melting drill (the IceMole) to collect englacial brine for geomicrobiological analyses. Results from previously collected outflow and more recent samples indicate that the brine harbors a metabolically active microbial community that persists, despite cold, dark isolation. Isotope geochemistry and molecular analysis of functional genes from BF suggested that a catalytic or ‘cryptic’ sulfur cycle was linked to iron reduction. Recent metagenomic analysis confirms the presence of numerous genes involved in oxidative and reductive sulfur transformations. Metagenomic and metabolic activity data also indicate that subglacial dark CO2 fixation occurs via various pathways. Genes encoding key steps in CO2 fixation pathways including the Calvin Benson Basham and Wood Ljungdahl pathway were present and brine samples showed measureable uptake of 14C-labeled bicarbonate. These results support the notion that, like the deep subsurface, subglacial environments are chemosynthetic, deriving energy in part by cycling iron and sulfur compounds. Collectively our interdisciplinary dataset indicates that subsurface brines are widespread in the Taylor Valley polar desert and this previously unknown groundwater network likely supports unique microbial life.