Bacterial activity at –2 to –20◦C in arctic wintertime sea ice

• Main Authors: Karen Junge, Hajo Eicken, Jody W. Deming
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Lium; ice core; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.499.3191; http://www2.gi.alaska.edu/~eicken/he_publ/04JED.pdf

Arctic wintertime sea-ice cores, characterized by a temperature gradient of 2 to 20°C, were investigated to better understand constraints on bacterial abundance, activity, and diversity at subzero temperatures. With the fluorescent stains 4,6-diamidino-2-phenylindole 2HCl (DAPI) (for DNA) and 5-cyano-2,3-ditoyl tetrazo-lium chloride (CTC) (for O2-based respiration), the abundances of total, particle-associated (>3-m), free-living, and actively respiring bacteria were determined for ice-core samples melted at their in situ temperatures (2 to20°C) and at the corresponding salinities of their brine inclusions (38 to 209 ppt). Fluorescence in situ hybridization was applied to determine the proportions of Bacteria, Cytophaga-Flavobacteria-Bacteroides (CFB), and Archaea. Microtome-prepared ice sections also were examined microscopically under in situ conditions to evaluate bacterial abundance (by DAPI staining) and particle associations within the brine-inclusion network of the ice. For both melted and intact ice sections, more than 50 % of cells were found to be associated with particles or surfaces (sediment grains, detritus, and ice-crystal boundaries). CTC-active bacteria (0.5 to 4 % of the total) and cells detectable by rRNA probes (18 to 86 % of the total) were found in all ice samples, including the coldest (20°C), where virtually all active cells were particle associated. The percentage of active bacteria associated with particles increased with decreasing temperature, as did the percentages of CFB (16 to 82 % of Bacteria) and Archaea (0.0 to 3.4 % of total cells). These results, combined with correlation analyses between