[Vulcan]

Oxygen-depletion (“hypoxia”) has recently reached levels that can sicken or kill cod in large areas ("more than 1000 km2") of the Gulf of St. Lawrence, and no live cod have been found in these areas in recent surveys done by The Canadian Department of Fisheries and Oceans (DFO) (2). (see map at right - click on map to enlarge)

Why a shortage of oxygen? Bacterial decomposition (rot) of dead organic matter (animals or plants) exerts a severe oxygen-draining effect on seawater, and this process is widely recognized as a primary cause of “hypoxic” seawater. This is how ocean “dead zones” are being formed in various other parts of the world ocean (e.g. the Gulf of Mexico, Chesapeake Bay, Baltic Sea and others) (3).

http://www.fisherycrisis.com/seals/hypoxia.htm