Fluorescense Measurements of Microbial Life in the WAIS Divide Ice Core

We present a combination of autofluorescence studies and direct biological examinations to characterize the abundance and type of microbes in the WAIS Divide Ice Core. Rapid one-dimensional fluorescence scans were conducted on 2/3rds of the 580 meters thus far archived from WAIS Divide in order to characterize both the bulk abundance of microbes and the fraction that were phototrophs. These scans show a greater than 90% loss of cells during the ~120 m over which snow and firn are compacted into ice, with additional slow declines thereafter. In addition, detailed mapping was conducted on a dozen selected pieces from the core to further characterize the microbial abundance and distribution within each piece. Typical cell distributions were found to be highly heterogeneous, with clumping commonly observed. This work also established that contamination from drill fluid frequently penetrates approximately 2.5 mm from the exterior surface of the core. After the fluorescence scans were completed, these selected pieces were melted and their biological content studied via direct examination. These observations have allowed us to calibrate fluorescence to cell counts directly and characterize representative microbial types.