Vertical distribution of bacteria in arctic sea ice

Abstract

1. SUMMARY Heterotrophic bacteria were enumerated in north polar sea ice cores obtained near Point Barrow, Alaska. Highest concentrations of total and viable bacteria were found in the layer con-taining the sea ice microbial community identi-fied by the maximum chlorophyll a content. Gas vacuolate bacteria were also found in the sea icc, a discovery which is consistent with their recent report from antarctic sea ice microbial communi-ties. The gas vacuolate bacteria comprised 0.2% or less of the viable bacteria isolated from sea ice cores, lower than conccntrations reported for most antarctic samples. Most gas vacuolate iso-lates from the sea ice cores were pigmented pink, orange, or yellow. An ice core from nearby saline Elson Lagoon contained an inverted sea ice mi-crobial community with highest chlorophyll a concentrations and bacterial counts found in the top 0-20 cm of the ice. This surface layer also