Earlier this month there was an area off the Oregon coast where the
seafloor was littered with piles of dead sea life (typically slow-moving sea life, like crabs, worms, jellyfish – but no dead fish were found).  This is the fifth year in a row that this has happened in the area, so scientists have a pretty good bead on what’s happening.

The phenomenon is referred to as a hypoxic "dead zone".  Scientists believe that dead zones are caused by coastal upwelling, a natural process by which changes in ocean currents cause deep water to rise to the surface. When the oxygen level of the upwelling deep water is too low, it can suffocate any sea life in the area.

Dead zones have been observed near other coasts, as well, including Peru, Namibia and India.  Researchers are still working to understand the seasonal and geographical patterns of Oregon’s dead zone.  There is speculation that global warming is causing changes in ocean currents, which, in turn, create the dead zones.  My guess is that they’ll need to gather some more data before we can draw any conclusions.

Next time you paddle through a patch of icy, cold water and say, "Man, upwelling gives me the chills,"  stop for a minute and think . . .  are you cold because the water temperature dropped suddenly or are those goose bumps caused by the silent cries of all those poor, defenseless crabs, gasping for their last breath . . .

Here are some links if you want to read more on the topic.

http://www.sciencedaily.com/releases/2004/08/040810091946.htm 

http://www.voanews.com/english/AmericanLife/2006-08-29-voa32.cfm 

UPDATE: 9/1/06

It’s been reported that large algae blooms can cause dead zones.  The algae blooms are often attributed to raw nutrients (fertilizer, treated sewage, etc) being dumped into the water.  latimes.com has a good graphic.    Link