CORVALLIS, Ore. The longest, largest and most devastating hypoxic event ever observed in marine waters off the Oregon Coast has finally ended, researchers at Oregon State University say.
During mid-October, a normal shift arrived from summer southward-blowing winds to fall and winter northward-blowing winds, resulting in the end of the upwelling season and a rise in dissolved oxygen to levels that can generally support marine life, scientists said. The oxygen levels should continue to increase throughout the next month.
Monitoring efforts will continue, new technology will be utilized, federal funding will be sought for more work in the area, and work is already under way to identify the amounts of biological damage done by this event, the fifth "dead zone" in five years and, literally, one for the record books.
In 2006, the low-oxygen waters off Oregon stretched further north along the coast, reached closer to shore, and were thicker than any event previously detected. The event was four times larger than any previous episode and lasted four times as long. More important, the oxygen levels were by far the lowest ever recorded on the near shore of Oregon, approaching "anoxic" conditions in some places, or the complete lack of oxygen.
"The figures were just off the charts this year," said Francis Chan, a marine ecologist with OSU and the Partnership for Interdisciplinary Studies of Coastal Oceans, or PISCO. Any level of dissolved oxygen below 1.4 milliliters per liter is considered hypoxic for most marine life, and many areas were below that, some 10-30 times lower than normal, others approaching zero.
"We had stronger and more persistent winds from the north, causing greater upwelling and more severe hypoxic conditions, than we had ever seen before," said Jack Barth, OSU professor of oceanic and atmospheric sciences. "The winds were outside the normal summer range of anything seen in decades."