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Dead Zones Increasing Off Oregon Coast, Including California, Washington

Published 11/05/2018 at 2:29 AM PDT
By Oregon Coast Beach Connection Staff

According to findings by Francis Chan of Oregon State University in Corvallis (of which the Hatfield in Newport is a part), Oregon has seen a decline in oxygen in ocean waters near the seafloor for two decades now, resulting in what they term “hypoxia season.” It’s not dissimilar to the idea of a wildfire season, except here there are periods where oxygen levels nosedive in various pockets of the West Coast, killing off fish and crabs.

Chan and his colleagues said this past summer of 2018 was one of the worst, a claim backed up by many commercial crabbers who noted major die-offs in their harvesting areas. They turned to the scientific community for help, and now NOAA, OSU and Oregon Department of Fish and Wildlife (ODFW) have teamed up to further study the issue.

“Our ocean is changing and when we first measured hypoxia off Newport in 2002, we thought it might be a local phenomenon,” Chan said. “That is no longer the case. Low oxygen is striking a big swath of the West Coast and is returning year after year. So we’d better learn to live with it.”

OSU researchers received a $1.1 million grant from NOAA Coastal Hypoxia Research Program to work with ODFW and crabbers over the next four years to place sensors in crab pots, equipment that will check oxygen levels. A lack of data has been a major hurdle in understanding these dead zone pockets, with only about four sensors out in the ocean. This new project will bring the number up to 40.

Over the summer, one sensor near Heceta Head documented oxygen levels reaching to zero close to the sea floor in early June, which coincided with reports by fishermen in the area of dead crabs.

The evidence this was working in pockets was startling. ODFW researchers had received a report of one crabber over the summer who only obtained four live crabs after deploying 120 pots into the ocean. Yet Chan talked to another crabber who had similar dismal results in one part of the Oregon coast waters, but only eight miles away there were plenty of crab to be found.

A major cause behind the dead zones is a changing climate, said Chan, which is causing waters around the world to lose their ability to hold oxygen.

Another major factor is shifting wind patterns. Waters off the Oregon coast get filled with nutrients by upwellings, which is created by southward winds mixing up the water to bring up nutrients from the deep. This fuels blooms of phytoplankton, which boost the food chain when it happens in balance, but the flipside is if there are too many they choke the oxygen out of the water as they die and sink to the seafloor.

Normally, according to OSU oceanographer Jack Barth, Oregon has wind patterns that alternate between conditions that create upwellings and those that stop the process after about a week or two.

“That allows the system to flush out and re-oxygenates the water,” Barth said. “Over the past several years, though, that flushing hasn’t happened as frequently and the phytoplankton overwhelms the system and essentially chokes it.”

Barth added an alarming element to all this is that they’ve begun to see low oxygen levels in the middle water column and not just the bottom, at the seafloor. This has implications of affecting other fisheries, such as halibut.

Source: https://beachconnection.net/news/deadzone110518_201.php

 

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