The proposed study is to investigate the distribution of key properties - abundance, community composition and community metabolic capabilities - of bacterioplankton communities in the Arctic Ocean. In conjunction with data collected during April on the SCICEX 95 cruise, the seasonal and spatial variation of these properties will be studied. The patterns of spatial and temporal variation of these properties will be examined and related to sources of organic matter fueling heterotrophic production. The investigation will be conducted using samples collected from a submarine dedicated to Arctic oceanography and analyzed in the laboratory after the cruise. Community composition will be analyzed using a method developed in the investigation's laboratory based on separating partial sequences of the 16S rRNA gene. Community metabolic capabilities will be assessed by the ability of bacteria to grow heterotrophically on a battery of 95 different sole C sources. Bacterioplankton abundance will be determined by epifluorescence microscopy. We will analyze water samples chemically to determine the concentrations amino acids, carbohydrates and dissolved organic carbon, and conduct bioassays using native bacteria to determine directly the proportion of dissolved organic carbon that they can metabolize.
