The deep ecosystems of Earth (and other planets)

Collaborators at the Deep Carbon Observatory, exploring the "Galapagos of the deep", add to what is known and unknown about the most pristine ecosystem on Earth.

Bacteria, archaea, and other microbes exist even in the deepest known subsurface, and are weirder than their surface counterparts. Approximately 70% of Earth's bacteria and archaea live underground. Deep life on Earth suggests that microbes could inhabit the subsurface of other planets

Barely living "zombie" bacteria and other life forms make up a vast amount of carbon deep underground on Earth.

On the eve of the American Geophysical Union's annual meeting, scientists at the Deep Carbon Observatory today reported on several transformative discoveries, including the amount and type of life that exists deep underground, under the most extreme extremes of pressure. , temperature and low consumption of energy and nutrients. availability.

Drilling 2.5 kilometers into the seabed, and sampling microbes from continental mines and wells more than 5 km deep, the team has used the results to build models of the ecosystem deep within the planet.

Using information obtained from hundreds of sites under the continents and seas, they have evaluated the size of the deep biosphere: 2 to 2.3 trillion cubic kilometers (almost twice the volume of all oceans), as well as the mass of deep-life carbon: 15 to 23 [1] billion tons (an average of at least 7.5 tons of carbon per cu km km).

The work also helps determine the types of alien environments that could support life. Among many key discoveries and ideas, the following are noted:

The deep biosphere constitutes a world that can be seen as a kind of "underground Galapagos" and includes members of the three domains of life: bacteria and archaea (microbes without a nucleus with a membrane) and eukaryotes (microbes or multicellular organisms with cells). containing a nucleus as well as membrane-bound organelles)

Two types of microbes, bacteria and archaea, dominate Deep Earth. Among them there are millions of different types, most of which have yet to be discovered or characterized. This so-called microbial "dark matter" dramatically expands our perspective on the tree of life. Deep Life scientists say that about 70% of Earth's bacteria and archaea live underground

Deep microbes are often very different from their surface cousins, with life cycles on quasi-geological timescales, in some cases eating only energy from rocks.

The genetic diversity of life below the surface is comparable to or greater than the surface. While subsurface microbial communities differ greatly between environments, certain genera and higher taxonomic groups are ubiquitous: they appear all over the planet

The richness of the microbial community is related to the age of the marine sediments where the cells are found, suggesting that in older sediments, the energy from food has decreased over time, reducing the microbial community

The absolute limits of life on Earth in terms of temperature, pressure, and energy availability have yet to be found. Records are continually breaking. A pioneer for the hottest organism on Earth in the natural world is Geogemma barossii, a single-celled organism that thrives in hydrothermal vents on the seafloor. Its cells, tiny microscopic spheres, grow and replicate at 121 degrees Celsius (21 degrees higher than the boiling point of water)

Microbial life can survive up to 122 ° C, the record set in a laboratory culture (in comparison, the warmest place on the Earth's surface in an uninhabited Iranian desert, is about 71 ° C, the temperature of a steak well done) )

The record depth at which life has been found in the continental subsoil is approximately 5 km; the record in marine waters is 10.5 km from the ocean surface, a depth of extreme pressure; at a depth of 4,000 meters, for example, the pressure is approximately 400 times higher than at sea level

Scientists have a better understanding of the impact on life in human-manipulated subsurface locations (e.g., fractured shales, carbon capture and storage)

The increasing precision and decreasing cost of DNA sequencing, coupled with advances in deep-sea drilling technologies (pioneering the Japanese science vessel Chikyu, designed to drill to the bottom in some of the most seismically active regions the planet) did it.Researchers may see the composition of the deep biosphere for the first time.

There are comparable efforts to drill deeper and deeper into continental environments, using pressure-holding sampling devices to preserve microbial life (none of which are believed to pose a threat or benefit to human health).

To estimate the total mass of Earth's subcontinental deep life, for example, the team compiled data on cell concentration and microbial diversity from locations around the world.

Led by Cara Magnabosco of the Flatiron Institute's Center for Computational Biology, New York, the scientists analyzed a number of considerations, including global heat flux, surface temperature, depth, and lithology (the physical characteristics of rocks in each location) to estimate that continental subsoil houses 2 to 6 × 1029 cells.

Combined with estimates of subsurface life below the oceans, the total global biomass of the deep Earth is about 15 to 23 petagrams (15 to 23 billion tons) of carbon.

Says Mitch Sogin of the Marine Biology Laboratory, Woods Hole, USA, Co-Chair of DCO's Deep Life community with more than 300 researchers in 34 countries: "Exploring deep underground is similar to exploring the Amazon rainforest. There is life. everywhere, and everywhere there is an impressive abundance of unexpected and unusual organisms.

"Molecular studies increase the likelihood that microbial dark matter is much more diverse than we currently know, and deeper branching lineages challenge the three-domain concept introduced by Carl Woese in 1977. Perhaps we are getting closer to a nexus where the first possible branching patterns could be accessible through a deep investigation of life ".

"Ten years ago, we knew much less about the physiology of the bacteria and microbes that dominate the subsurface biosphere," says Karen Lloyd of the University of Tennessee in Knoxville, USA. "Today, we know that, in many places, They spend most of their energy simply maintaining their existence and little to growing, which is a fascinating way to live.

“Today too, we know that subsurface life is common. Ten years ago, we had only tried a few places, the kind of places we would hope to find life in. Now, thanks to ultra-deep sampling, we know that we can find them almost everywhere, although the sampling has obviously reached only an infinitesimally small part of the deep biosphere. "

"Our studies of deep biosphere microbes have produced a lot of new knowledge, but also a much greater realization and appreciation of how much we still have to learn about life underground," says Rick Colwell, Oregon State University, USA. “For example, scientists still don't know all the ways that deep subsurface life affects life on the surface and vice versa. And for now we can only marvel at the nature of the metabolisms that allow life to survive in the extremely impoverished and prohibitive conditions for life on deep Earth. "

Among the many remaining enigmas of life deep on Earth:

Movement: How does life spread deep, laterally through cracks in rocks? Up and down? How can deep life be so similar in South Africa and Seattle, Washington? Did they have similar origins and were they separated by plate tectonics, for example? Or do the communities themselves move? What role do major geological events (such as plate tectonics, earthquakes, the creation of large igneous provinces, meteorite bombardments) play in the movements of deep life?

Origins: Did life start deep within the Earth (either within the crust, near hydrothermal vents, or in subduction zones) and then migrate to the sun? OR

 References:  

https://deepcarbon.net/life-deep-earth-totals-15-23-billion-tonnes-carbon

The deep-sea mystery is changing our understanding of life; Karen lloyd https://www.youtube.com/watch?v=PbgB2TaYhio