Articles | Volume 14, issue 6
Biogeosciences, 14, 1445–1455, 2017
Biogeosciences, 14, 1445–1455, 2017

Research article 21 Mar 2017

Research article | 21 Mar 2017

Viable cold-tolerant iron-reducing microorganisms in geographically diverse subglacial environments

Sophie L. Nixon1, Jon P. Telling2, Jemma L. Wadham3, and Charles S. Cockell4 Sophie L. Nixon et al.
  • 1School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
  • 2Department of Civil Engineering and Geosciences, Newcastle University, Newcastle, NE1 7RU, UK
  • 3School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
  • 4UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK

Abstract. Subglacial environments are known to harbour metabolically diverse microbial communities. These microbial communities drive chemical weathering of underlying bedrock and influence the geochemistry of glacial meltwater. Despite its importance in weathering reactions, the microbial cycling of iron in subglacial environments, in particular the role of microbial iron reduction, is poorly understood. In this study we address the prevalence of viable iron-reducing microorganisms in subglacial sediments from five geographically isolated glaciers. Iron-reducing enrichment cultures were established with sediment from beneath Engabreen (Norway), Finsterwalderbreen (Svalbard), Leverett and Russell glaciers (Greenland), and Lower Wright Glacier (Antarctica). Rates of iron reduction were higher at 4 °C compared with 15 °C in all but one duplicated second-generation enrichment culture, indicative of cold-tolerant and perhaps cold-adapted iron reducers. Analysis of bacterial 16S rRNA genes indicates Desulfosporosinus were the dominant iron-reducing microorganisms in low-temperature Engabreen, Finsterwalderbreen and Lower Wright Glacier enrichments, and Geobacter dominated in Russell and Leverett enrichments. Results from this study suggest microbial iron reduction is widespread in subglacial environments and may have important implications for global biogeochemical iron cycling and export to marine ecosystems.

Short summary
Despite their permanently cold and dark characteristics, subglacial environments (glacier ice–sediment interface) are known to harbour active microbial communities. However, the role of microbial iron cycling in these environments is poorly understood. Here we show that subglacial sediments harbour active iron-reducing microorganisms, and they appear to be cold-adapted. These results may have important implications for global biogeochemical iron cycling and export to marine ecosystems.
Final-revised paper