OSU scientists believe global warming contributing to growing dead zone off Oregon coast

By Shelby Bateson
December 20, 2:53 PM, Green Technology Examiner

South Africa Oceanic Dead Zones


There is a dead zone off the Oregon coastline which has been growing since 2002.  A group of scientists at Oregon State  University (OSU), working in conjunction with PISCO, the Oregon Department of Fish and Wildlife, National Oceanic and Atmospheric Administration, University of Washington and the Olympic Coast National Marine Sanctuary, believe that the warming ocean water is, at least in part responsible for the dead zone. The dead zone now stretches from Newport Beach to Florence and to ocean depths of 90 feet.

The dead zone reached its peak in 2006 when the oxygen level of the water reached a reading of zero.  The sea floor in the area was littered with dead crabs and fish, and the zone actually reached all the way up the coast of Oregon and into the Washington coastline. 

OSU scientists have been studying a similar dead zone off the coast of Chile.  They have been taking sea floor samples dating back to the last ice age and found that the current dead zone in Chile was teeming with life at that time.  They were able to analyze the samples using CAT scans.  As the ice age receded and the ocean waters began warming, oxygen levels changed which caused a change in the marine life in the oceans.  AS the waters continue to warm, the oxygen levels continued to drop and life continued to decrease.

Different areas of the ocean support different ecological niches of life.  When conditions change, these areas are unable to support those niches and living species die off.  The decomposing plant and animal life adds to the loss of oxygen.  This is a very inexact science, and the true effect of the loss of oxygen cannot be accurately measured because it is unknown how much of the dead plant and animal life is washed out to deeper levels in the ocean with the tides.

The temperature of the waters is affected by many variables, including tidal currents and winds.  During normal years, cold water rich in nutrients but low in oxygen "upwells" from the deep ocean off Oregon.  These colder waters mix with oxygen-rich water near the surface, causing some phytoplankton growth and provide the basis for a thriving fishery and healthy marine food chain.

Since the tidal currents and offshore winds do tend to change from year to year, the size of the dead zone is not constant.  Life can and does return to areas where the oxygen level supports that life. 

However, it is a concern that the reduced oxygen levels do correlate with warmer water.   "Jane Lubchenco, the Valley Professor of Marine Biology at OSU and principle investigator for PISCO, also said that the biological monitoring of species health and impacts in the nearshore Pacific Ocean is "grossly inadequate," making it difficult to evaluate the long-term impacts of low-oxygen and other events." 

There are currently approximately 400 dead zone throughout all the oceans on the planet.  Almost all the other zones have been attributed to causes such as fertilizers and sewage, that flow down rivers and streams to the ocean.   When the microscopic marine plants called phytoplankton are exposed to excess nutrients, such as fertilizers and sewage, these tiny plants bloom, then die and decompose, robbing the ocean of life-sustaining oxygen. Animals that fail to escape dead zones either suffocate or suffer severe stress.  The number of these dead zones is actually doubling every 10 years, but this is a situation that can be corrected with more careful use of fertizers and trash. 

The zones in Oregon, Washington, could be a continuum with  zones off the coasts of Peru and Chile.  There are two other zones off the east and west coasts of Africa that are all behaving in a similar manner to those in Oregon. These zones are not consistent with the excessive fertizer and trash flow into the oceans, which is what has led to the study being conducted in these areas.

Jack Barth, a professor of oceanography at OSU, says, "I wouldn’t be surprised if coastal dead zones appear every summer from now on because oceanic and atmospheric conditions are now primed for their regular, repeated formation.", "How big will the dead zones be? How long will they last? And how often will oxygen levels plunge low enough to cause marine die-offs?"  Research will continue.

Resources:  Marine Dead Zone

Oregon Dead Zone 

Theory for the Dead Zone off the Oregon Coast