The 'dark oxygen' debate isn't helping anyone

The mysterious appearance of oxygen on the ocean floor is fuelling curiosity and controversy

- VICTORIA GILL

I've known since I was in school that oxygen - that defining molecule for life - is produced by plants in the presence of sunlight. But now, I'm not so sure.

A recent discovery may have turned that fundamental, biology-text-book fact on its head. The discovery is also fuelling a scientific row between high-tech mining companies and environmental campaigners.

But it's a dispute that could fuel a mission to understand more about the mysteries of the deep ocean - and perhaps resolve my new scientific uncertainty about oxygen.

The initial revelation was that oxygen might be being produced in parts of the deep ocean where light can't penetrate - earning it the nickname 'dark oxygen'. It sounds impossible, but it was a discovery published in the journal Nature Geoscience in the middle of 2024.

The finding itself dates back to 2013, which is when the researchers - led by Prof Andrew Sweetman at the Scottish Association for Marine Science - first saw "an enormous amount of oxygen being produced at the seafloor in complete darkness."