Abstract
Subglacial Lake Whillans lies below around 800 m of Antarctic ice and is isolated from fresh sources of photosynthetic organic matter to sustain life. The diverse microbial ecosystems within the lake and underlying sediments are therefore dependent on a combination of relict, overridden, marine-derived organic matter and mineral-derived energy. Here, we conduct experiments to replicate subglacial erosion involving both gentle and high-energy crushing of Subglacial Lake Whillans sediments and the subsequent addition of anoxic water. We find that substantial quantities of reduced species, including hydrogen, methane, acetate and ammonium and oxidised species such as hydrogen peroxide, sulfate and carbon dioxide are released. We propose that the concomitant presence of both hydrogen and hydrogen peroxide, alongside high concentrations of mineral surface radicals, suggests that the splitting of water on freshly abraded mineral surfaces increases the concentrations of redox pairs from rock-water reactions and could provide a mechanism to augment the energy available to microbial ecosystems.
Highlights
Subglacial Lake Whillans lies below around 800 m of Antarctic ice and is isolated from fresh sources of photosynthetic organic matter to sustain life
Analysis of the Subglacial Lake Whillans (SLW) lake and sediment pore waters revealed a phylogenetically diverse microbial ecosystem[3], with taxa involved in chemolithotrophy, heterotrophy, methanotrophy[4], N-1 and S-cycling[10]
This research demonstrates that comminution and wetting of fine-grained subglacial lake sediment produces a spectrum of gases, together with organic and inorganic solutes, that are readily utilised by subglacial microbes
Summary
Subglacial Lake Whillans lies below around 800 m of Antarctic ice and is isolated from fresh sources of photosynthetic organic matter to sustain life. The diverse microbial ecosystems within the lake and underlying sediments are dependent on a combination of relict, overridden, marine-derived organic matter and mineral-derived energy. Analysis of the SLW lake and sediment pore waters revealed a phylogenetically diverse microbial ecosystem[3], with taxa involved in chemolithotrophy, heterotrophy, methanotrophy[4], N-1 and S-cycling[10]. Some of the types of oxidising and reducing reactions that can occur in subglacial environments are shown, along with the change in Gibbs free energy (ΔGoR) for the half reactions. Microbial metabolisms across a redox gradient can largely be predicted based on the assumption that the redox reactions involving the largest negative change in free energy occur preferentially, this may not always be the case[17]. They illustrate the potential of a variety of inorganic and organic C compounds to form by a spectrum of reactions that are associated with the degradation of organic matter
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