Microbes trap massive amounts of carbon – Science

Violent continental collisions and volcanic eruptions are not things normally associated with comfortable living conditions. However, a new study, involving the University of Tennessee, Knoxville, associate professor of microbiology Karen Lloyd, unveils a large microbial ecosystem living deep in the earth that is fueled by chemicals produced during these tectonic cataclysms.

When the oceanic and continental plates collide, one plate is pushed downward, or subducted, into the mantle and the other plate is pushed upward and dotted with volcanoes. It is the primary process by which chemical elements are moved between the Earth’s surface and the interior and ultimately recycled back to the surface.

“Subduction zones are fascinating environments – they produce volcanic mountains and serve as portals for the movement of carbon between the Earth’s interior and exterior,” said Maarten de Moor, associate professor at the National University. from Costa Rica and co-author of the study.

This process is normally believed to occur beyond the reach of life due to the extremely high pressures and temperatures involved. While life almost certainly does not exist under the extreme conditions where the Earth’s mantle mixes with the crust to form lava, in recent decades scientists have learned that microbes extend much deeper into the earth. earth’s crust than previously thought.

This opens up the possibility of discovering previously unknown types of biological interactions occurring with deep plate tectonic processes.

An interdisciplinary and international team of scientists has shown that a large microbial ecosystem primarily eats the carbon, sulfur and iron chemicals produced during the subduction of the oceanic plate beneath Costa Rica. The team obtained these results by sampling deep underground microbial communities that are brought to the surface in natural hot springs, as part of work funded by the Deep Carbon Observatory and the Alfred P. Sloan Foundation.

The team discovered that this microbial ecosystem sequesters a large amount of carbon produced during subduction that would otherwise escape into the atmosphere. The process results in an estimated decrease of up to 22 percent in the amount of carbon transported to the mantle.

“This work shows that carbon can be siphoned off to fuel a vast ecosystem that largely exists without the input of solar energy. This means that biology could affect the flow of carbon in and out of the Earth’s mantle, forcing scientists to change the way they think. the deep carbon cycle on geological timescales, ”said Peter Barry, associate researcher at the Woods Hole Oceanographic Institution and co-author of the study.

The team found that these microbes – called chemolithoautotrophs – sequester so much carbon due to their unique diet, which allows them to produce energy without sunlight.

“Chemolithoautotrophs are microbes that use chemical energy to build their bodies. So they’re like trees, but instead of using sunlight they use chemicals,” said Lloyd, co-author of the study. “These microbes use chemicals from the subduction zone to form the basis of an ecosystem that is large and filled with various primary and secondary producers. It’s like a vast forest, but underground.”

This new study suggests that the known qualitative relationship between geology and biology may have important quantitative implications for our understanding of how carbon has changed through deep time. “We already know of many ways that biology has influenced the habitability of our planet, leading to increased atmospheric oxygen, for example,” said Donato Giovannelli, professor at the University of Naples Federico II and co – corresponding author of the study. “Today, our work in progress reveals another exciting way of co-evolving life and our planet”.

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