For all the folks thinking about Project Azorian[0], I recently read "Blind Man's Bluff"[1] and recommend it for the larger context of oceanic subsurface reconnaissance.
0. https://www.cia.gov/legacy/museum/exhibit/project-azorian/
1. https://www.amazon.com/Blind-Mans-Bluff-Submarine-Espionage/...
The "Sealab 2020" cartoon show had an episode about this in 1972 (so, over 50 years ago): https://en.wikipedia.org/wiki/Sealab_2020 "7 "Where Dangers Are Many" October 21, 1972 Sealab crew investigates a disturbance to find an automatic bottom-dredging mining operation in their area. The captain of the operation, Samuel Carlson, becomes trapped under his dredge and is rescued by Sealab. While Carlson is decompressing after having received medical attention at Sealab, the crew manage to convince him to allow them 24 hours to demonstrate how to mine less destructively."
Available here: https://archive.org/details/sealab-2020-the-complete-series
Specifically: https://archive.org/download/sealab-2020-the-complete-series...
One issue though: in the episode, the Sealab 2020 crew were worried about damage to sealife as a byproduct of mining. They were OK with removing the nodules if they could be done without causing significant seafloor disturbance. But it sounds like removing the nodules might by itself harm sealife by depriving sealife of oxygen.
Another theme in the episode is the need for a person in the loop to guide the dredging machine to do less damage -- compared to a fully automated system the owner was so proud of investing in. Interesting to think about given the push to AI these days.
I watched Sealab 2020 at the time as a kid and very much enjoyed it and saw these characters as role models. I very much dreamed back then of leading such a lab when 2020 rolled around (like a "Paul" character did in the cartoon). Heartbreaking in 2001 to see "Sealab 2021" make fun of all this hopefulness for the future and the environment -- when I was hoping for a good sequel building on the Sealab 2020 values.
Sadly, my own plans from the 1980s to make Sealab-like habitats in the oceans, in outer space, and elsewhere never got very far (yet):
https://pdfernhout.net/princeton-graduate-school-plans.html
https://pdfernhout.net/sunrise-sustainable-technology-ventur...
No one wondered how it would disturb the seafloor since so little was known about the deep sea environment back then.
The nodules were going to be the answer to mineral shortages that would naturally occur as you deplete all the economically recoverable deposits in your own country or as deposits in friendly countries become unavailable due to geopolitical changes. Countries that have little mineral wealth of their own but do have a coastline that gives them access to deep water could benefit by opening their offshore areas to seafloor mining.
I think the discovery or the notion that oxygen could be produced in the deep sea by processes acting on or with these nodules is not unusual. Extremophile organisms able to live in anoxic conditions in total darkness on the seafloor should surprise no one. It also should surprise no one that some of the organisms may have evolved to produce oxygen as a by-product of their interaction with mineralized rocks.
It's a big ole beautiful world out there and we don't understand a lot about it. It seems unlikely that in 4.5 billion years nothing has evolved to fill that niche. Personally I think it's bacteria all the way down.