Influence of bedrock mineral composition on microbial diversity in subglacial environments.

CfG staff: Mitchell, Andrew.

Key collaborators: Montana State University, Dr Mark Skidmore and Dr. Eric Boyd. Queens University, Canada: Dr. Melissa Lafrenière.

The lack of light energy capable of driving photosynthesis in subglacial environments suggests that energy for cellular synthesis and the maintenance of microorganisms is supplied from chemical energy (chemosynthesis), likely derived from weathering of the local bedrock (e.g., minerals). Indeed, numerous lines of evidence suggest that many geochemical processes, including mineral weathering and redox transformations in subglacial environments, are driven by microorganisms. Hydrological regimes, nutrient availability and redox conditions have been shown to impact the function of microorganisms in subglacial environments. However, the influence of bedrock mineralogy on the structure, composition and activity of microbial assemblages in subglacial systems remains poorly understood despite its potential importance over a significant portion of Earth’s surface both today and on glacial-interglacial time scales. At Robertson Glacier, Canada, we have been using a combination of in situ mineral incubation and DNA fingerprinting techniques (TRFLP) to investigate the potential role that bedrock mineral composition has upon on microbial diversity in subglacial environments.

Previous studies have demonstrated the importance of particulate-associated microbes in subglacial environments and indicate that this biomass represents a larger fraction of the community when compared with planktonic populations. Our results from Robertson Glacier indicate that mineralogy, due to the influence on community composition, structure, and abundance may help to explain these previous observations. Specifically, pyrite is the dominant mineralogical control on subglacial community structure at Robertson Glacier as revealed by TRFLP, and mineral associated biomass was proportional to the abundance of Fe in the incubated minerals. This suggests the importance of Fe and S metabolism at the mineral surface, as supported by the recovery of 16S rRNA gene sequences which were closely affiliated with organisms that are known to metabolize these species.

Solid phase mineral utilization by microbial populations is therefore likely to be a critical, life-sustaining strategy that enables subglacial ecosystems to persist during extended glacial-interglacial time scales when ice masses have covered between 30% and 100% of Earth’s continental land surface.

Key publications:
Mitchell, AC, Lafrenière, MJ, Skidmore, ML, Boyd, ES (2013) Influence of bedrock mineral composition on microbial diversity in a subglacial environment. Geology 10.1130/g34194.1.

Mitchell, AC and Brown, GH. (2008) Modelling geochemical and biogeochemical reactions in subglacial environments. Arctic, Antarctic and Alpine Research, 40, 531-547.

Boyd, ES.; Skidmore, M.; Mitchell, AC.; Bakermans, C.; Peters, JW. (2010)  Methanogenesis in subglacial sediments. Environmental Microbiology Reports. DOI: 10.1111/j.1758-2229.2010.00162.

Boyd, ES, Lange, RK, Mitchell, AC, Havig, JR, Hamilton, TR, Lafrenie, MJ, Shock, EL, Peters, JW, Skidmore, ML (2011) Diversity, Abundance, and Potential Activity of Nitrifying and Nitrate-Reducing Microbial Assemblages in a Subglacial Ecosystem. Applied and Environmental Microbiology, 77, 4778–4787.

NASA EPSCoR Space Grant (2008-2009). Methanogenesis in subglacial environments – Implications for Quaternary deglaciation. PI: AC Mitchell.

European Centre for Arctic Environmental Research (ARCFAC V) (2009-2010). Debris entrainment and transfer in Svalbard valley glaciers. Principal investigator with Michael Hambrey, Duncan Quincey (Aberystwyth University), Sean Fitzimons (Otago University, New Zeland). EC contract no. 026129.