Thriving Biosphere Found in Rocks Deep Underneath Seafloor

bacteria under sea rocks photo

Photo credit: M. McCarthy via University of California, Santa Cruz

There's a reason for leaving "no stone unturned" when it comes to scientific exploration -- there's probably life underneath even the most unlikely rock. Even if that rock is well under the seafloor. Researchers from the University of California, Santa Cruz, have found evidence for a biological community of living organisms camped out in porous rock deep underneath the seabed. The microbes are "chemoautotrophic," getting their energy from chemicals rather than sunlight or sunlight-dependent organisms. With a whole new-to-us biosphere that fixes carbon in a similar way that grasslands or forests fix carbon, the findings could change what we know about the ocean's carbon cycle, Lead researcher Matthew McCarthy states, "This study provides the strongest evidence yet that a really large biosphere exists in the warm fluids in the porous upper-oceanic crust. It's large not just in area, but in productivity. In the same way that forests and grasslands fix carbon and produce organic matter on land, our data suggest these microbes produce enough organic matter to export carbon to other systems. That's a real expansion of our ideas about the oceanic carbon cycle."

University of California, Santa Cruz reports that the team used carbon dating, measuring carbon-12, -13 and -14 and using a ratio of the three to provide clues to the origins of the organic matter within the porous rock. The carbon-14 analysis revealed that the carbon came from carbonate ions formed as the ocean absorbed carbon dioxide from the atmosphere somewhere around 11,800 years to 14,400 years ago.

These dates are important, because knowing how old deep-ocean water is tells researchers how quickly the ocean's layers circulate. If there is very old carbon being mixed in at the deepest layers, it could mean researchers have been underestimating how rapidly the ocean circulates, which shifts what we know about the absorption of carbon dioxide by the ocean.

The team will publish their findings in January in Nature Geoscience, though it is already available online.

The ocean is a vital part of circulating carbon dioxide out of the atmosphere -- it absorbs roughly two-thirds of the CO2 emitted into the air. However, such rapid absorption is changing the ocean's chemistry, making it more acidic. Understanding how the ocean deals with CO2, including how rapidly it captures, stores, and circulates, can have wide-reaching impacts on our understanding of marine systems. These new findings might bring on a change in how we understand the ocean's capabilities with dealing with CO2.

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