File this under: “How little we know.”
The upper troposphere is apparently teeming with particles of bacteria and fungi, surprising researchers.* Proving that life is tenacious and that microbes can survive just about anywhere, a team at Georgia Institute of Technology have discovered that quite a bit of what we assumed was dust and sea-salt may be bacteria aloft. Some of the little critters made it as high as the upper troposphere which is 10km up (where commercial flights cruise). No one is quite sure if the microbes “live” up there, or were just visiting.
The study showed that viable bacterial cells represented, on average, around 20 percent of the total particles detected in the size range of 0.25 to 1 microns in diameter. By at least one order of magnitude, bacteria outnumbered fungi in the samples, and the researchers detected 17 different bacteria taxa – including some that are capable of metabolizing the carbon compounds that are ubiquitous in the atmosphere – such as oxalic acid.
The bacteria were probably tossed up there by wind and waves:
When the air masses studied originated over the ocean, the sampling found mostly marine bacteria. Air masses that originated over land had mostly terrestrial bacteria. The researchers also saw strong evidence that the hurricanes had a significant impact on the distribution and dynamics of microorganism populations.
The microorganisms likely reach the troposphere through the same processes that launch dust and sea salt skyward. “When sea spray is generated, it can carry bacteria because there are a lot of bacteria and organic materials on the surface of the ocean,” Nenes said.
Microbes might seed clouds
(It’s another factor the IPCC models don’t include).
The microorganisms could have an impact on cloud formation by supplementing (or replacing) the abiotic particles that normally serve as nuclei for forming ice crystals, said Athanasios Nenes, a professor in the Georgia Tech School of Earth and Atmospheric Sciences and School of Chemical and Biomolecular Engineering.
“In the absence of dust or other materials that could provide a good nucleus for ice formation, just having a small number of these microorganisms around could facilitate the formation of ice at these altitudes and attract surrounding moisture,” Nenes said. “If they are the right size for forming ice, they could affect the clouds around them.”
The clouds are alive… (maybe)
For the future, the researchers would like to know if certain types of bacteria are more suited than others for surviving at these altitudes. The researchers also want to understand the role played by the microorganisms – and determine whether or not they are carrying on metabolic functions in the troposphere.
“For these organisms, perhaps, the conditions may not be that harsh,” said Konstantinidis. “I wouldn’t be surprised if there is active life and growth in clouds, but this is something we cannot say for sure now.”
More information at Georgia Tech
Speaking of clouds and storms: thoughts go to people on the East Coast of Australia where the remnants of TC Oswald have flooded Brisbane again, four lives have been lost and it has dumped the heaviest rain in a decade on Sydney. [See the Sydney Radar here and 24 hour rainfall map]. People are still being evacuated in Bundaberg (north of Brisbane) where waters are still rising.
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* While these researchers were surprised. Lank points out in comments that an Asian study found something similar in July 2012.