The atmosphere of Earth is permanently teeming with countless numbers of microscopic organisms - including :

• bacteria
• viruses
• fungi
• algae
• archaea
• spores of mosses, fungi, etc etc.
• ( and, in addition, raw DNA and RNA fragments )

It has been called :

[…] the least understood biome on Earth despite its critical role as a microbial transport medium. The influence of surface cover on composition of airborne microbial communities above marine systems is unclear.

Source : ISME J. 2020 Mar; 14(3): 871–876

The number of organisms per cubic metre tends to decrease with distance from land and with altitude. As an example, the density of bacteria alone routinely reach numbers of 10⁴ to 10⁸ cells per m^{3 (ref.)}

Very little is known about the effects of the 'aerobiome' on :

• Climate change
• Geological processes
• Human health
• Disease proliferation
• Agriculture
• Ecology
• Cloud seeding

Some of these effects are likely to be very profound.

Further information on this very under-researched subject can be found at wikipedia

Note: In addition to the uni-cellular organisms, there are also significant quantities of small insects, spiders, nematodes etc. etc..

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