First observations on airborne prokaryotes in a subArctic Atlantic marine area.

Among extreme environments, bioaerosol includes a wide range of primary atmospheric organic particles associated with and emitted by living and dead organisms. Bioaerosol samples were collected along two transects at a subArctic Atlantic spatial scale, including the eastern Fram Strait and the Greenland, Norwegian, and North Seas. This study was aimed at first estimating microscopically the prokaryotic abundance, biomass and phenotypic traits, along with the number of potential viable and respiring cells. Moreover, physiological profiles at community level were assessed. Prokaryotic abundance ranged from 104 to 107 cells m􀀀 3, with the predominance of small sized cells (0.1 μm3). Prokaryotic biomass reached higher values (mean value 233 μg C m􀀀 3) in relation to the occurrence of large sized rods. Overall, the percentage of the viable cells was lower than the dead ones, while respiring cells were in lower abundance than total cells. The physiological profiles revealed various potential metabolic pathways among the samples, highlighting the utilization of phosphate-carbon, carboxylic and amino acids. These first results on the metabolism and physiology of microbes, which survived transport in the atmosphere of the Northern Hemisphere, suggest that bioaerosol constitutes an extremely dynamic environment of remarkable ecological interest, also considering future global warming scenarios.