The Pacific Northwest’s suffocating ocean

A U.S. government research vessel found trouble during its June and July cruise off the coasts of Oregon and Washington. Scientists aboard the National Oceanic and Atmospheric Administration research vessel Ronald H. Brown pulled up greenish-black debris in the ship’s plankton net.

Oceanographer Richard Feely said the dark sludge was a bad sign: “We added a little alcohol, and we began to realize that it was a large mass of phytoplankton, either still living or dead, sinking into the deeper water.”

The discovery is concerning for the region’s marine life. As the tiny creatures decompose near the ocean floor, they consume oxygen. And if too much oxygen gets consumed at once, it leaves the waters inhospitable to other lifeforms, according to NOAA scientists.

An onshore lab hasn’t yet examined the substance, but Feely and other scientists aboard the research vessel saw enough. Using data from a broad array of underwater sensors as well as the evidence of dead and dying plankton, the researchers in late July announced they found evidence of a worsening dead zone, or area of poorly oxygenated water, off the Oregon and Washington coasts. It makes the area one of a list of coastlines around the world where oxygen-poor dead zones are increasing.

Dead zones—the informal descriptor for underwater locations suffering from hypoxia—sometimes occur naturally, according to NOAA. Naturally occurring hypoxia may help explain an at least century-old phenomenon that locals of Mobile Bay, Ala., call jubilee, where fish and crustaceans periodically cast themselves ashore.

But NOAA is concerned about dead zones caused by human activity. According to the agency, fertilizer runoff into waterways can spark algae blooms that leach oxygen out of the water when they die off and decompose.

Researchers previously identified a dead zone in the Gulf of Mexico south of Louisiana and East Texas where waters periodically become hypoxic and unable to support some marine life. Scientists studying the Pacific Northwest’s coastal waters have also detected evidence of seasonal hypoxia. But data from the Ronald H. Brown indicate worsening conditions and a quicker arrival this year of low oxygen levels.

Fisherman working the Washington and Oregon coastlines are anecdotally confirming the phenomenon. During years with more hypoxia, crabbers commonly pull up cages filled with crustaceans that suffocated at depth, according to Oregon Dungeness Crab Commission spokesman Tim Novotny. “Unfortunately, this is another one that’s looking like it could be a landmark year for these hypoxia zones,” Novotny told Oregon Public Broadcasting.

Novotny said crabbers welcome the research monitoring the oxygen levels as well as an Oregon law passed in July devoting $1.9 million to fund more study of the problem. “Any kind of data that comes in is gold, as far as we’re concerned,” Novotny said. “You can’t fight what you don’t know.”