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Deep-sea microbes produce oxygen without photosynthesis, researchers find

Written by Oceanographic Staff

While almost all oxygen on earth is produced by photosynthesis, biologists have recently discovered deep-sea microbes that produce oxygen in an entirely new way.

Most oxygen on land and in the sea is produced by photosynthesis – a process that needs light. However, through landmark research, a team of researchers at the University of Denmark now have found deep-sea microbes that live in complete darkness and are able to produce oxygen in a completely new way.

By analysing several microbes that live in the low-oxygen, dark spheres of the deep sea, the team of researchers have identified a deep-sea microbe that produces oxygen without photosynthesis. Don Canfield, who was part of that research team, said: “We wanted to see the limit of oxygen concentration where [organisms] can still live.”

During the research, the team took a closer look at a microbe named Nitrosopumilus maritimus which is known for oxidising ammonia to produce nitrogen – a process that requires oxygen. While the microbe tends to live in oxygen-rich ocean areas, it is also able to thrive in the dark, oxygen-depleted ocean. “Nobody had any idea as to why they were there,” said Canfield.

By storing archae cultures in airtight containers that were kept in the dark and reducing oxygen levels in the containers to reproduce deep sea conditions, the research team found out that oxygen levels actually started to rise after the microbes consumed all of it.

Even though there are three known ways in nature that produce oxygen without photosynthesis, the researchers don’t suspect any of these are used by N. maritimus because these microbes are able to generate oxygen and nitrogen oxide with their unique mechanism. Both products can’t be found in the three other known ways to produce oxygen without photosynthesis. Unfortunately, the researchers aren’t sure how the microbes generate the oxygen yet. They suspect a different biological mechanism is at play here, one that has never been seen before.

“It opens up the possibility that there’s this whole new metabolism functioning in the oceans that we didn’t know about,” says Canfield. The exciting finding might also suggest that the mechanism could be used by other species in the deep sea – yet another reminder of the importance of further studying and protecting the deep.

For more from our Ocean Newsroom, click here.

Photography courtesy of Unsplash (cover image) and NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011.

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