We know so little of the hidden world beneath the seas. This is a perfect example of why it is so risky to just power ahead and start mining our oceans.
https://www.bbc.com/news/articles/c728ven2v9eo
Dark oxygen made by deep sea 'batteries'
The discovery that lumps of metal on the seafloor produce oxygen raises questions over plans to mine the deep ocean.Victoria Gill (BBC News)