This was published in 2011 but remains a nice summary of the major issues concerning exploitation and protection of the deep ocean; an area we still know little about.
This will probably help us understand the bigger picture. Note particularly the comments in the article that in 2014 the global CO2 emissions were 65% greater than in 1990: despite constant promises to curb CO2 and increase the use of renewable energy. No one is interested! 🙁