ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence

Submitted by		Karen Junge
Authors		Karen Junge, J. W. Deming, and H. Eicken
Category		Interdisciplinary Research
Title		Surface-Associated Bacterial Activity to -20°C in Arctic Wintertime Sea Ice
Affiliation		School of Oceanography, University of Washington, Seattle, WA, USA

Abstract

The lower temperature limit for life was examined in wintertime Arctic sea ice characterized by temperature ranging from -2 to -20°C. Active bacteria were revealed even in the coldest of ice horizons by novel in-situ and sub-zero (ice) dilution methods coupled with analysis by respiratory stain and rRNA probes. The active cells at -15 to -20°C were almost exclusively associated with surfaces. Correlations between bacterial parameters and measures of particulate matter in the ice, as well as a proportional increase in Cytophaga-Flavobacteria-Bacteroides cells at lower temperatures, confirm the importance of surfaces to bacterial activity at extremely low temperatures. Observations of cultured bacteria motile to -10°C and of natural assemblages within Arctic lake ice add to the concept that liquid inclusions in frozen environments provide adequate habitat for active microbial populations on Earth and possibly elsewhere.