Debris-Rich Basal Ice as a Microbial Habitat, Taylor Glacier, Antarctica

Abstract

Two ∼4 m vertical sequences of basal ice were collected from tunnels dug into the northern lateral margin of Taylor Glacier, McMurdo Dry Valleys, Antarctica. In both cases the basal sequences exhibit two contrasting ice facies groups; clean (debris-free) and banded dispersed (debris-rich). Debris-rich ices exhibit elevated CO₂ and depleted O₂ concentrations compared to the clean facies. Bacterial cell numbers, respiration rates, and nutrient concentrations are highest in debris-rich layers. Together, our geochemical and biological data indicate that microbial heterotrophic respiration is likely occurring in situ within the basal ice matrix at ambient temperatures near −15°C. This implies that the basal ice zone of polar glaciers and larger ice sheets is a viable subglacial microbial habitat and active biome of significant volume that has not previously been considered.

Keywords:

• biogeochemical cycling
• sediments
• subsurface microbiology

Acknowledgments

The research was supported by NSF-OPP grants 0636770 and 0636828 to MS and BC respectively. MS also acknowledges funding from NSF-EPSCoR and MSU VP for Research and is grateful for the use of the Subzero Science and Engineering Research Facility at MSU. SM was supported by a NSF-IGERT fellowship (NSF DGE 0654336) and a Geological Society of America Student Research Grant. JLT and RL were supported by the Belgian Scientific Programme on Antarctica (Science Policy Office, contract n°AA4DDE021). T. Brox and P. Amato provided field assistance in 2007. T. Brox also provided assistance in ice subsampling in the lab at MSU.