According to an article in OregonLive,
The Pacific Ocean off Oregon experienced low-oxygen conditions for the eighth consecutive summer, Oregon State University researchers said today, an indication that the "hypoxic" conditions that kill crabs and other creatures on the ocean floor are here to stay.This phenomenon does seem to have become a staple of late summer and early fall Oregon science news. I've always found it a little hard to believe. Our coastal waters are so cold (which means their ability to dissolve and carry gases like oxygen should be high compared to warmer water), and so rough (which means they have plenty of opportunity to contact and dissolve oxygen), that it seems oxygen depletion should be the least of our worries. I'm guessing that eutrophication at deeper levels simply overwhelms the ability of oxygen-rich surface water to mix in. Upwelling of nutrient-rich deep water is characteristic of the PNW coast, and is not a new phenomenon; the annual dead zones appear to be new. I can't help but wonder, though, if it's mostly a matter of scale and severity- a matter of degree- rather than an actually "new" phenomenon.
The picture of the tidepool full of dead crabs is riveting, an image that brings the message home more powerfully than all the articles I've read about this issue.