Hypoxia: Causes
By Charlie Kyne
Hypoxia, or "ocean dead zones" are areas in bodies of water such as oceans, lakes, rivers and deltas without enough oxygen to sustain life. This can occur naturally but at the rate new ocean dead zones are being created a finger is definately pointing toward human activity as the cause.
https://www.youtube.com/watch?v=yh5Ev8VEbZ0
1 Oceans Monthly/June, 2014