Ocean surface waters normally contain 5—8 milliliters of oxygen per liter of water, a number that declines rapidly with depth. But on his first day out, Chan found that at a depth of 150 feet the inner coastal waters off Oregon were hypoxic — oxygen levels there were lower than 1.43 milliliters per liter, so low that fish cannot survive.

Similar low oxygen levels were found further offshore, the researchers knew that something unprecedented was happening.

The changes in Oregon may be related to a broader pattern around the globe, in which subsurface patches of permanent hypoxia seem to be growing in size and losing yet more oxygen, for unknown reasons. And whether or not global warming is responsible for the changes to date, ocean models forecast that in the coming decades increasing water temperatures and changes in circulation will drive oxygen concentrations down even further.

"What we have been experiencing is a perfect storm — where weather, climate and currents can come together to crash an ecosystem," says Chan.

via www.enn.com

the size and growing number of oceanic dead zones is alarming, and i expect will increasing hammer global food webs.