These Deep-Sea Organisms Make Oxygen without Sunlight

Tiny organisms living deep in the world’s oceans have stunned scientists, who now say some of these unusual creatures are making their own oxygen. And unlike extremophiles that inhabit niche environments, the researchers behind the groundbreaking discovery say that these oxygen-producing organisms are among the most plentiful in all of the world’s oceans.


Life finds a way…at least, if that life has access to oxygen. There are, of course, microscopic organisms that survive without it, but those extremophiles typically inhabit niche environments and are extremely small in number.

To produce live sustaining oxygen, plants, animals and certain types of bacteria uses sunlight in a process known as photosynthesis. But some life on earth, especially deep in the ocean, seems to be living in oxygen deprived environments, and without sunlight.

To try to understand how these creatures are getting by without light to make the oxygen they need, researchers from the University of Denmark took a closer look. And what they found was totally unexpected.


To better understand what was going on, the researchers looked at a common ocean microbe known as Nitrosopumilus maritimus, and its cousins, ammonia oxidizing archaea.

“These guys are really abundant in the oceans, where they play an important role in the nitrogen cycle,” said biologist Beate Kraft, in a press release announcing the new study.

“These microbes are so common, that every 5th cell in a bucket of sea water is one of them,” added Don Canfield, co-author of the paper

“{But} they need oxygen,” said Kraft, “so it has been a long-standing puzzle why they are also very abundant in waters where there is no oxygen.”

In an effort to understand how these oxygen-consuming organisms were thriving in an oxygen-depleted environment, the researchers gathered up some samples and took them back to the lab.

“We wanted to see what would happen if they ran out of oxygen,” said Canfield, “like they do when they move from the oxygen rich waters to oxygen depleted waters. Would they survive?”

To test this idea, the researchers put the Nitrosopumilus maritimus in an isolated tank and waited to see what happened once the oxygen ran out.

“We saw how they used up all the oxygen in the water,” said Canfield, “and then to our surprise, within minutes, oxygen levels started increasing again. That was very exciting!”

Shockingly, it turned out that the organism was making its own oxygen, and without sunlight! The researchers note that it was not enough oxygen to affect the overall levels of their environment, but instead was just enough for the organisms to keep themselves alive and thriving.


The researchers behind this exciting study, which was published in the journal Science, say that this unexpected result may force their fellow scientists to take a fresh look at the entire nitrogen cycle of the world’s oceans, especially since this type of organism is so abundant worldwide.

“If this lifestyle is widespread in the oceans, it certainly forces us to rethink our current understanding of the marine nitrogen cycle,” said Kraft. “My next step is to investigate the phenomenon we saw in our lab cultures in oxygen depleted waters in various ocean spots around the world.”

Towards that end, the team has already collected water samples in Mariager Fjord in Denmark and are preparing to do the same in the waters off Mexico and Costa Rica.

Follow and connect with author Christopher Plain on Twitter: @plain_fiction