The Biogeochemistry beneath the Whillans Ice Stream, West Antarctica: Evidence for a Chemoautotrophically Driven Ecosystem

Abstract:

Antarctic sub ice environments represent some of the most understudied microbial ecosystems on Earth. The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project recently sampled sediments and water from Subglacial Lake Whillans (SLW) and its hydrologically connected grounding zone where this lake system empties beneath the Ross Ice Shelf. Here we highlight findings on the diversity and metabolic capabilities of the microbial community detected in these samples. We utilized a hot water drill with a novel filtration and UV treatment system to insure that our entry and sampling did not contaminate our samples or the pristine subglacial ecosystem. Geochemical and microbiological data suggests the water column hosts an active microbial community sustained by the production of fixed carbon from chemosynthesis with energy derived from reduced nitrogen, sulfur, and iron compounds. These energy sources appear to be influenced by bedrock weathering at the sediment surface. For example, dominant 16S rRNA gene phylotypes in the water column suggest ammonia oxidation as a potential source of chemoautotrophic energy. While in the SLW surficial sediments, diversity analysis of functional genes involved in both sulfur oxidation and sulfate reduction (aprA, dsrA, and rdsrA), aprA gene abundance, and 16S rRNA gene analysis indicate that sulfur-oxidizing microbes are dominant. These preliminary results represents the first data on microbial community structure and function from an Antarctic subglacial lake and its grounding zone.