fuuuuuuuuuuuuuuuuuuuck
It’s called dark oxygen because it’s produced without any light fueled chemical reactions such as photosynthesis - instead, it’s produced by water electrolysis, an oxidation/reduction reaction occurring due to metallic nodules with differing electrostatic potentials on the sea floor. In essence, a natural electric current is splitting seawater into hydrogen and oxygen.
It’s not called dark oxygen because it’s made of dark matter or anything like that, if anyone was wondering.
dark oxygen, show me the forbidden electron orbitals