NASA – March 29, 2007
“Dead zones” in this context are areas where the bottom water (the water at the sea floor) is anoxic – meaning that it has very low (or completely zero) concentrations of dissolved oxygen. These dead zones are occurring in many areas along the coasts of major continents, and they are spreading over larger areas of the sea floor. Because very few organisms can tolerate the lack of oxygen in these areas, they can destroy the habitat in which numerous organisms make their home.
The map below, created in 1999-2000 by Dr. Robert Diaz of the Virginia Institute of Marine Science (VIMS), shows dead zones throughout the world (a version of this map also appeared in the March 2000 issue of Discover magazine). Diaz estimates that the number of such sites will double by 2010.
see full article at the NASA web site