In the 1830s, when Charles Darwin was in the middle of the Atlantic ocean aboard HMS Beagle, he decided to collect samples of falling dust, which he sent to his colleague Christian Gottfried Ehrenberg to test for the presence of living organisms. The team were surprised to find the airborne dust was carrying over sixty types of single-celled organisms they called “infusoria” (protists) ref.

Since then, a large number of studies have tested atmospheric samples from various altitudes and locations, and every study has shown that the Earth's air is carrying countless numbers of DNA and RNA-based organisms.

Including :

• bacteria
• viruses
• fungi
• algae
• archaea
• yeasts
• spores of mosses, ferns, 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. 14(3): 871–876

As an example, the density of bacteria alone routinely reach numbers of 10⁴ to 10⁸ cells per cubic metre (ref.)

As might be expected, the number of organisms per cubic metre tends to decrease with distance from land and with altitude.

The number of viruses falling to the Earth's surface each day has also been measured :

[…] we demonstrate that even in pristine environments, above the atmospheric boundary layer, the downward flux of viruses ranged from 0.26 × 10⁹ to >7 × 10⁹ m⁻² per day. These deposition rates were 9–461 times greater than the rates for bacteria, which ranged from 0.3 × 10⁷ to >8 × 10⁷ m⁻² per day."

Source : ISME J, v.12(4)

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

Notes:

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

[2] Some research papers refer to the proliferation of viruses in the atmosphere as the 'Virosphere' or 'Virusphere'.

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