November 28, 2021

I, Science

The science magazine of Imperial College

The drilling ship Chikyu has discovered slow growing extremophile organisms living over 2000m below the sea bed

shipThousands of metres below the rocky sea floor, an environment devoid of light, water and oxygen, may not seem like the most likely place for life to thrive, but findings of microbial life from a drilling expedition by the International Ocean Discovery Program off the North West coast of Japan have proved otherwise.

The drilling ship, Chikyu, broke records in 2012 when it drilled 2442m below the sea bed of Pacific Ocean into ancient coal beds. Samples were analysed on board the ship and researchers were surprised to discover microbes surviving in the cores of the rock samples. Since coal beds are a source of carbon, the microbes were fed different types of hydrocarbons to determine what their energy source was. Tests concluded that these extremophile organisms were using methyl compounds as their main food source, but also that their metabolism was extremely slow, most likely due to the need to conserve energy when food is scarce.

The researchers, who presented their findings at the America Geophysical Union Fall Meeting, were also trying to find out about the diversity of microbial life present beneath the sea floor and how they got there to begin with.

“Were these microbes just in a swamp, and loving life in a swamp, because there is all sorts of carbon available, oxygen, organic matter… and then that gets buried?” asks Dr Trembath-Reichert, one of the researchers working on the project. It has also been hypothesised that the microbes could have originally existed much higher up in the ocean, but somehow made their way down.

Knowing more about the number of microbes present, and their origins, may give scientists more clues about the effect that these organisms are having on the carbon cycle and therefore global warming and climate change. As these microbes feed on a diet of hydrocarbons, they produce methane as a by-product, a greenhouse gas which has a weight-for-weight effect on climate change twenty times more potent than that of carbon dioxide over a hundred year period. Being able to estimate the number of these organisms could help to determine their effect on global warming.

Commercial offshore drilling remains a controversial topic to many, given the environmental disasters caused by events like the Gulf of Mexico oil spill in 2010. A civil trial against BP is currently in its final stages and could see the oil and gas giants paying up to $13.7 billion in fines.

Despite the bad press that offshore drilling is often given, the research carried out aboard Chikyu and further studies into estimating the global population sizes of these microbes beneath the world’s oceans may go some way towards predicting their total effect on climate change, both at present, and in the future.