Sky River: The Microbiome

A closed cycle. Atmosphere is an important part of the water cycle. Water evaporates and is carried in the form of particles by major and minor currents of air, moved here and there, before cooling down, aggregating into droplets of water, and falling as rain or snow. Like water on land, streams that form as small headwaters that flow into larger streams, then rivers, then oceans, the water of the atmosphere flows from small source vapors similar to headwaters, then flows into the major jet streams, sometimes to form spiraling eddies or storms along the way. Except. Except the atmosphere is so much deeper, an inverted ocean of air.

An ocean of air. The water in large lakes and oceans stratifies into layers separated by boundaries of rapidly changing temperatures called thermoclines. The air ocean also stratifies, separated by thermoclines. The layer near the surface of the earth is dynamic, the next layer is slow moving or static, then the next layer out is dynamic again until eventually the uppermost layer simply thins into the vacuum of space. Of course, these different layers, particularly the troposphere, the one closest to earth, drive weather and climate in collaboration with the Earth.

The three system problem.  Water threads through rocks, beneath and upon the surface of the Earth and is an integral part of the lithosphere. Water rises from the lithosphere to the atmosphere where it flows through the different strata, shifting between its three forms of matter, ice, water, and vapor. The biosphere links the two spheres forming a complex network of interactions that create the world we live in. The study of this network requires teams of ecologists, climatologists, biogeochemists, geologists, physicists, environmental scientists, and social scientists. The complexity of interactions between these three systems is daunting, but we are teasing out some interesting threads. One relatively recent find about this network is that bacterial communities otherwise called the microbiome or microbial community live and thrive in the atmosphere.

The atmospheric microbiome. Initially, microbes in the atmosphere were thought to be wind-blown, accidently tourists in the aeolian stream like frogs or insects or fish picked up by the storm and carried far from their homes. Eventually, researchers hypothesized that some microbiomes may have permanent residency in the sky river. Studies have supported this, with communities composed of both transient and permanent residents. In other words, the sky is alive. These bacteria may play a role in ice formation thereby affecting weather. Other bacteria may play a role in carbon fixation. An important role that could be used in mitigation of high concentrations of carbon dioxide and climate change.

Sky Rivers. Our understanding of microbiomes has increased exponentially in the past two decades. We now know that the microbiome in humans and other organisms is an important part of a healthy life and should be studied as an ecosystem. We have found thriving microbiomes on rocks in rivers, in the open water of lakes, and at the depths of the ocean. In fact, the microbiome may be living within the deepest water and rocks of the lithosphere. On this Earth, all of life is composed of cells that create beings that are more than the sum of their parts. Taking a larger view, the Earth is composed of small entities, microbiomes, other communities, and ecosystems creating the biosphere, that is more that the sum of its parts. And through all the individual cells, through the communities, through the rocks and the air threads streams of water, this is the Tethysphere.

More Readings:

DeLeon-Rodriguez, N., Lathem, T.L., Rodriguez-R, L.M., Barazesh, J.M., Anderson, B.E., Beyersdorf, A.J., Ziemba, L.D., Bergin, M., Nenes, A. and Konstantinidis, K.T., 2013. Microbiome of the upper troposphere: species composition and prevalence, effects of tropical storms, and atmospheric implications. Proceedings of the National Academy of Sciences, 110(7), pp.2575-2580.

Dutta, A., Gupta, S.D., Gupta, A., Sarkar, J., Roy, S., Mukherjee, A. and Sar, P., 2018. Exploration of deep terrestrial subsurface microbiome in Late Cretaceous Deccan traps and underlying Archean basement, India. Scientific reports, 8(1), p.17459.

Womack, A.M., Bohannan, B.J. and Green, J.L., 2010. Biodiversity and biogeography of the atmosphere. Philosophical Transactions of the Royal Society B: Biological Sciences, 365(1558), pp.3645-3653.