Northern Gulf of Mexico

One of the most documented dead zones on Earth is in the northern Gulf of Mexico in the summer when solar heating increases the buoyancy of surface waters thereby reducing mixing between the surface and the bottom. Phytoplankton - powered by the same sunlight and fed by a rich nutrient broth flowing out of local rivers - bloom, die, sink, and get re-mineralized by bacteria which use up all the available oxygen in the isolated bottom waters which then become dead zones. NASA image acquired January 3, 2012.