Monday , August 2 2021

Microbes can act as gatekeepers on Earth's deep carbon

Two years ago, a team of scientists visited the sub-area of ​​Costa Rica, where the ocean floor was sinking under the continent, and the volcanoes were rising above the surface. They wanted to know if microbes could affect the cycle of carbon moving from the surface of the Earth into the deep interior. According to their new study in Nature, the answer is affirmative – yes they can.

This innovative study, published in Nature, shows that microbes consume and – most importantly – help capture a small amount of sinking carbon in this area. This finding has important implications for understanding the underlying processes of the Earth and for discovering how nature can potentially help mitigate climate change.

In the subduction zone there is communication between the ground and the interior. Two slabs collide and the thicker slab sinks, transporting the material from the surface into the interior of the Earth. By showing that nearby microbes play a major role in how the carbon and other elements are locked in the Earth's crust, it gives a deep understanding of Earth's processes and helps researchers shape how the Earth's interior can evolve over time.

The co-author, Professor Chris Ballenin, Head of the Earth Sciences Department at Oxford University, said: "What we have shown in this study is that in areas critical to the return of chemicals to the planet – Large Sub-Zones Areas life produces carbon. In geological terms, life can control chemicals on the surface and store elements like carbon in the earth's crust.

gas sampling apparatusPeter Barry created a gas sampling machine with Maarten de Moor, Giulio Bini and Angelo Battaglia.

This is the first evidence that underground life plays a role in removing carbon from subduction zones. Microbes have been found to be capable of taking carbon dissolved in water and converting it into mineral in the rocks. This study shows that the process takes place on a large scale in a subduction zone. This is a natural CO2 separation process that can control the presence of carbon on the surface of the Earth.

The lead author, Dr. Peter Barry, who conducted the study while in the Department of Natural Sciences at Oxford University, said: "We have found that a significant amount of carbon is trapped in non-volcanic areas rather than escaping through volcanoes or sinking into The interior of the Earth.

Until now, scientists have assumed that life plays little or no role in whether this ocean carbon is transported to the mantle, but we have found that life and chemical processes work together to be the gatekeepers of carbon delivery to the mantle.

Karen Lloyd and Donato Giovanni try a spring in the hills of Irasu volcanoKaren Lloyd and Donato Giovanilli try a spring in the hills of Irasu volcano.

During a 12-day expedition, the 25-member group of multidisciplinary scientists collected samples of water from thermal springs in Costa Rica. Scientists have long predicted that these thermal waters spit out ancient carbon molecules that had been mounded millions of years ago. By comparing the relative quantities of two different types of carbon – called isotopes – scientists have shown that the predictions are true and that unrecognized processes are working in the earth's crust above the subduction zone by acting to capture large amounts of carbon.

Watch a video for the expedition

After their analysis, scientists estimate that about 94% of this carbon is converted to calcite minerals and microbial biomass.

Senior author, Karen Lloyd, Associate Professor of Microbiology at the University of Tennessee, Knoxville, said: "These microbes literally isolate carbon. Scientists are actively working on carbon sequestration to mitigate climate change and carbon capture and storage as a means of emitting greenhouse gases for long periods of time. Our study is a really good example of where this happens naturally and has not previously been recognized. This study shows that this is happening on a large tank scale.

Donato Giovannelli and Karen Lloyd collect samples from the crater lake in Poás volcanoDonato Giovannelli and Karen Lloyd collect samples from the crater lake in the Poás volcano.

Maarten de Moor, co-author and professor at the National University of Costa Rica's Volcanology and Seismology Observatory, said: "It is amazing to note that small microbes can potentially affect the geological processes of similar rocks like these powerful and visually impressive volcanoes , which are direct pipelines to the interior of the Earth. The processes we have identified in this study are less obvious, but they are important because they work in vast spatial areas compared to volcanoes.

Researchers are now planning to explore other subduction areas to see if this trend is widespread. If these biological and geochemical processes occur globally, they would lead to 19% less carbon entering the deep mantle than previously estimated.

Co-author Donato Giovannelli, assistant professor at the University of Naples, Federico II, and a related scientist at CNR-IRBIM and Rutgers University, say, "There are probably many ways biology has too much impact on geology, we just have not.

Dr. Peter Barry, an associate research associate at Woods Hole Oceanographic Institution, added: "We have people from three different areas working together, and with such an interdisciplinary approach you can make such breakthroughs. This will change the way people look at these systems. To me it is exciting.

The study is part of the Deep Carbon Observatory's Biology Meets Subduction project. The interdisciplinary team includes 25 researchers from six nations belonging to each of the Deep Carbon Observatory (DCO) scientific communities: Deep Life, Extreme Chemistry and Physics, Reservoirs and Streams, and Deep Energy.

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