New Delhi, India

The deep seafloor - 12,000 feet below the surface of the Pacific Ocean - is covered by ancient rocks known as the Clarion-Clipperton Zone (CCZ).

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Although these rocks appear devoid of life, they may actually be hiding different kinds of tiny sea creatures and microbes, some of which may have adapted to survive in the dark.

The deep-sea rocks, which are called as polymetallic nodules, turn into a habitat for various marine organisms and also generate oxygen across the ocean floor.

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A team of scientists, which includes experts from Boston University, made this discovery which challenged the idea that sunlight is required for the production of oxygen and generally occurs near the surface of the ocean where photosynthesis of the phytoplankton occurs.

When the oxygen was detected at such depth amid darkness, initially the researchers felt that it was an error.

“This was really weird, because no one had ever seen it before,” said Jeffrey Marlow, who is the co-author of the study and an assistant professor of biology at Boston University’s College of Arts & Sciences.

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Scientists decode the production of dark oxygen

Marlow, who has an understanding of microbes present in extreme environments like deep-sea hydrothermal vents and hardened lava, initially believed that microbial activity is responsible for the production of oxygen.

For investigating the dark oxygen, deep-sea chambers which can land on the seafloors and encapsulate sediment, polymetallic nodules, living organisms and seawater were used by the researchers. 

For 48 hours, the oxygen levels in these chambers were measured by the team. Generally, if oxygen is consumed by the organisms, the levels will drop on the basis of the amount of activity carried out in the chamber. However, it was noted that in this case there was a rise in the oxygen levels.

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“We did a lot of troubleshooting and found that the oxygen levels increased many more times following that initial measurement,” said Marlow, adding, “So we’re now convinced it’s a real signal.”

The research was conducted by Marlow and his colleagues aboard a vessel which was dedicated to exploring the ecology of the CCZ. 

The team, which was headed by Andrew Sweetman from the Scottish Association for Marine Science, after conducting different experiments, reached the conclusion that microbial activity was not driving the production of the oxygen primarily even though a lot of microbes were present on and inside the rocks.

(With inputs from agencies)