One of the strongest greenhouse gasses is methane. Basic human activity such as using natural gas, cooking in the kitchen, or having a backyard barbeque party contributes to methane gas emissions.
On Earth, there are only 3 main natural producers of methane--subsurface water-rock interactions, volcanoes, and microbes, according to Whats Your Impact.Org. Out of the three, microbes produce the most and have deposited more than hundreds of gigatons of methane deep within the seafloor.
At the seafloor, methane seeps deep within and then percolates to the open ocean, where microbial communities consume most of the methane before it ever reaches the planet's atmosphere. Through the years, researchers have dug deep into the methane deposits beneath the planet's seafloor; however, since little reaches the atmosphere, the question remains? How do tiny oceanic microbes help regulate the Earth's temperature?
How Oceanic Microbial Communities Consume Methane
Jefferey Marlow, a former researcher in Organismic and Evolutionary Biology, Harvard University, led a team of researchers and discovered that oceanic microbial communities rapidly consume methane in the ocean before it escapes into the planet's atmosphere.
The study published in the journal Proceedings of the National Academy of Sciences, entitled "Carbonate-hosted microbial communities are prolific and pervasive methane oxidizers at geologically diverse marine methane seep sites," gathered various samples of methane-eating microbes from 7 diverse seafloor seeps. Researchers surprisingly found that carbonate rocks from one of the sites host methane-oxidizing microbial communities with, to date, the highest rate of methane consumption.
Peter Girguis, a professor at organismic and Evolutionary Biology, Harvard University, explains that the microbes found in carbonate rocks act like methane bio-filters that consume the methane before it percolates to the surface.
Carbonate rocks on the seafloor are common; in some locations, these rocks form chimney-like structures that can reach 12-60 inches in height. Unlike other types of rocks, carbonate rocks are porous, which creates channels that become home to a dense community of methane-consuming oceanic microbes.
Studying Oceanic Microbes
In 2015, researchers embarked on an expedition funded by the Ocean Exploration Trust, where Girguis discovered a reef of carbonate chimney off the coast of southern California, Point Dume. Returning in 2017, Girguis received funding from NASA to build an observatory on the seafloor.
Girguis explains that researchers measured the rate that microbes from carbonate rocks ate methane compared to oceanic microbes found in sediment. Here researchers discovered that carbonate dwelling microbes consume methane 50 times faster than those who thrived in sediment, which are the highest rates measured by the team anywhere reported by PhysOrg.
Marlow explains that the rate of methane oxidation and consumption far surpassed early predictions, which is why the team set out to understand why carbonate dwelling microbes had significantly faster rates.
The team found that the structure and composition of carbonate chimneys were ideal to house oceanic microbes that exacerbate the rate of consumption. Marlow explains that the chimneys that exist due to methane in fluid flowing out from the subsurface are transformed by oceanic microbes into bicarbonate which is then precipitated out of the seawater as carbonate rock.
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