Death hits western Pacific

The most severe low-oxygen ocean conditions ever observed on the West Coast of the United States have turned parts of the seafloor off Oregon into a carpet of dead Dungeness crabs and rotting sea worms, a new survey shows. Virtually all of the fish appear to have fled the area.

Scientists, who this week had been looking for signs of the end of this “dead zone,” have instead found even more extreme drops in oxygen along the seafloor. This is by far the worst such event since the phenomenon was first identified in 2002, according to researchers at Oregon State University. Levels of dissolved oxygen are approaching zero in some locations.

OSU scientists with the university-based Partnership for Interdisciplinary Studies of Coastal Oceans, in collaboration with the Oregon Department of Fish and Wildlife, used a remotely operated underwater vehicle this week to document the magnitude of the biological impacts and continue oxygen sampling. This recent low-oxygen event began about a month ago, and its effects are now obvious.

Any level of dissolved oxygen below 1.4 milliliters per liter is considered hypoxic for most marine life. In the latest findings from one area off Cape Perpetua on the central Oregon coast, surveys showed 0.5 milliliters per liter in 45 feet of water; 0.08 in 90 feet; and 0.14 at 150 feet depth. These are levels 10-30 times lower than normal. In one extreme measurement, the oxygen level was 0.05, or close to zero. Oxygen levels that low have never before been measured off the U.S. West Coast.