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Airborne bacteria confirm the pristine nature of the Southern Ocean boundary layer
- Source :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Year :
- 2020
- Publisher :
- National Academy of Sciences, 2020.
-
Abstract
- Significance We found that the summer airborne bacterial community in the marine boundary layer over the Southern Ocean directly south of Australia is dominated by marine bacteria emitted in sea spray, originating primarily from the west in a zonal band at the latitude of collection. We found that airborne communities were more diverse to the north, and much less so toward Antarctica. These results imply that sea spray sources largely control the number concentrations of nuclei for liquid cloud droplets and limit ice nucleating particle concentrations to the low values expected in nascent sea spray. In the sampled region, the sources of summer cloud-active particles therefore are unlikely to have changed in direct response to perturbations in continental anthropogenic emissions.<br />Microorganisms are ubiquitous and highly diverse in the atmosphere. Despite the potential impacts of airborne bacteria found in the lower atmosphere over the Southern Ocean (SO) on the ecology of Antarctica and on marine cloud phase, no previous region-wide assessment of bioaerosols over the SO has been reported. We conducted bacterial profiling of boundary layer shipboard aerosol samples obtained during an Austral summer research voyage, spanning 42.8 to 66.5°S. Contrary to findings over global subtropical regions and the Northern Hemisphere, where transport of microorganisms from continents often controls airborne communities, the great majority of the bacteria detected in our samples were marine, based on taxonomy, back trajectories, and source tracking analysis. Further, the beta diversity of airborne bacterial communities varied with latitude and temperature, but not with other meteorological variables. Limited meridional airborne transport restricts southward community dispersal, isolating Antarctica and inhibiting microorganism and nutrient deposition from lower latitudes to these same regions. A consequence and implication for this region’s marine boundary layer and the clouds that overtop it is that it is truly pristine, free from continental and anthropogenic influences, with the ocean as the dominant source controlling low-level concentrations of cloud condensation nuclei and ice nucleating particles.
- Subjects :
- Oceans and Seas
Indoor bioaerosol
Air Microbiology
Antarctic Regions
Subtropics
Microbiology
bioaerosol
Latitude
Earth, Atmospheric, and Planetary Sciences
Cloud condensation nuclei
Seawater
Southern Ocean
Aerosols
Multidisciplinary
Bacteria
Geography
Microbiota
Northern Hemisphere
Temperature
marine aerosol
Biological Sciences
Aerosol
Oceanography
Physical Sciences
Environmental science
Biological dispersal
Bioaerosol
Subjects
Details
- Language :
- English
- ISSN :
- 10916490 and 00278424
- Volume :
- 117
- Issue :
- 24
- Database :
- OpenAIRE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Accession number :
- edsair.doi.dedup.....9967f3a869bbc0c26b81fa15ec593b1a