There's a whole region of very deep water in the Gulf of Mexico so saturated with CO2 that no life lives there. None at all.

There was a well regarded documentary some while ago about how carbon moves around in the world and it touched on the industry in the Gulf. I can't seem to find it, unfortunately, as I seem to have mis-remembered the unusual scientific term for the intense level of CO2 dissolved, but there is CO2 sequestration happening. ISTR it wasn't planned; it was "just happening".

Wade.