Scientists Still Eyeing the ‘Dead Zone’

By Terry
team keeps watch on coastal waters
transition is the time of year when coastal wind patterns switch from winter’s
southerly flow to summer’s northerly pattern. The summer pattern favors
upwelling, the ocean process that ushers nutrients to the surface, providing
nourishment for near-shore marine life. It also brings conditions conducive to
hypoxia, or low oxygen levels, in the water, creating “dead zones” that can
either suffocate marine animals or force them to migrate to the surface or
other areas closer to shore to find adequate oxygen levels.

For the past
decade, the hypoxia team at Oregon State University (OSU)’s Partnership for
Interdisciplinary Studies of Coastal Oceans (PISCO) has monitored the waters
off Oregon’s coast.
During the
summer of 2002, oxygen levels in water near the Oregon coast dropped so low
that fish, crabs and other marine life had to flee the area or die by
suffocation. Scientists said the low oxygen levels – known as hypoxia – were
more extreme than they had ever documented so shallow and so close to shore in the
prior 50 years. Since then, the dead zone has recurred every summer at varying
intensities, some severe. The most severe occurred in 2006, when oxygen levels
dropped to all-time lows, including a few places with no oxygen, and created
huge areas of hypoxia along both the Oregon and Washington coasts.


In 2008, OSU researchers published a study in the journal “Science” based on a
review of all available ocean data records, and the hypoxia that has occurred
every summer since 2002. Although the size, duration, and severity of the dead
zone varies from year-to-year, the researchers concluded that those hypoxic
events are unprecedented, and could be connected to the stronger, persistent
winds stirred up by global climate change.

researchers suggested hypoxic occurrences could be the rule rather than
exception under current conditions.

“In this part
of the marine environment, we may have crossed a tipping point,” PISCO’s lead
scientist Jane Lubchenco said at the time.

“Levels of
oxygen in the summertime have suddenly become much lower than levels in the
previous 50 years,” added Lubchenco, who now heads up the National Oceanic and
Atmospheric Administration. “And 2006 broke all records, with parts of the
shallow shelf actually becoming anoxic, meaning that they lacked oxygen
altogether. We’ve never seen that before.”

Water oxygen
levels in these zones have repeatedly reached hypoxic levels, below which most
marine animals either suffocate or are severely stressed if they cannot escape
the area. If oxygen levels drop to zero, most – if not all – animals die. The
research report said the massive 2006 zone covered at least 3,000 square
kilometers, and lasted four months. Fish died or fled, thousands of crabs died,
and sedentary marine seafloor life faced almost total mortality.

While the
cause of all this is less than certain, the researchers said the hypoxic events
are “completely consistent” with global climate change.

Chan conducted
the survey of all known oxygen level records on the Oregon continental shelf
for the past 60 years, gleaning measurements taken from research cruises and
other ocean-going vessels from more than 3,000 stations. He said scientists
were seeing very low oxygen water “lasting for long periods and closer to shore
than at any other time in more than 50 years.” Chan’s survey encompassed
several El Nino and La Nina events – both of them suspects in any change that
occurs in Pacific Ocean conditions – as well as shifts in what’s called the
Pacific Decadal Oscillation, which affects short-term climate trends. None of
that trio appeared to have any relation to the hypoxia, the scientists noted.

In 2008,
Lubchenco said coastal upwelling systems like those off the Oregon coast occupy
only about 1 percent of ocean area, yet contain about 20 percent of global
fishery production. “These areas have historically been highly productive,” she
added. “The appearance or increase in severity of hypoxia in these ecosystems
would be cause for concern.”

In addition,
recovery from the 2006 event was slow, lending a sense of urgency to the
monitoring efforts by PISCO and others.

This rapid,
disturbing shift of ocean conditions in what is traditionally one of the
world’s most productive marine areas – what’s known to scientists as the
California Current Large Marine Ecosystem – has received much attention during
the past decade or so, raising questions about whether it has occurred before
and what’s causing it. Researchers say the situation is definitely different
than anything that has happened before, but still aren’t sure exactly what’s
causing the hypoxic conditions, other than it being consistent with climate

Jack Barth, an
OSU oceanographer and another PISCO lead scientist, said unusual weather events
– hurricanes, droughts and changes in wind patterns – have always occurred
naturally, making it difficult to pinpoint whether any particular event is the
direct result of climate change.

“Having said
that, we expect global warming to generally cause stronger and more persistent
winds,” he said. “These winds contribute to the hypoxic events by increasing
plankton production and holding low-oxygen water on the continental shelf for
longer periods.”

Blowin’ in
the Wind

Unlike hypoxic areas in the Gulf of Mexico caused by agricultural runoff and pollution,
low-oxygen water off the Oregon coast is a natural phenomenon triggered by
seasonal upwelling – wind-driven mixing of cold, nutrient-rich deep water and
surface water.

What changed,
Barth said, is the pattern of Northwest wind, and decreasing oxygen levels in
the deep, offshore waters that are part of the seasonal upwelling.

winds would blow at the coast for a week or so, then settle down for several
days,” he noted. “As the winds eased, so did the upwelling, and low-oxygen
water was washed away. Those traditional wind patterns have shifted, and now
may last 20 to 30 days instead of a week. The system doesn’t have time to
cleanse itself.”

Water oxygen
levels in those zones now repeatedly reach hypoxic levels, below which most
marine animals either suffocate or are severely stressed if they cannot escape
the area.

“The 2006
situation was not only the strongest, most widespread hypoxia event yet seen
off the Pacific Coast – it was also the most long-lasting,” said Chan. “The
oxygen levels were off the charts, and they continued through October, which is
unheard of. For the first time we’ve ever observed, some parts of the
near-shore ocean actually ran out of oxygen altogether.”

If an area
becomes anoxic (oxygen levels drop to nil), most – if not all – animals die.

expect hypoxia to continue. In fact, hypoxic occurrences could become the rule
rather than exception under current conditions, which is why the PISCO team and
others are watching so intently.

Pitch In

In 2009 and 2010, OSU researchers in a program funded by Oregon Sea Grant
worked with Oregon crabbers to use their crab pots as underwater monitoring
stations. Sensors attached to the pots gathered vital oceanographic
information, including data that could provide the answers to why and when
hypoxia zones form in coastal waters. Because crab pots are positioned using
GPS and distributed throughout much of Oregon’s coastal ocean, researchers can
gather data from a much broader geographical range than using high tech ocean
observing methods.

fishermen are leery of researchers for fear that the information could be used
to close fisheries or restrict catches and seasons. Scientists are often
skeptical of the quality of data gathered by fishermen. Representatives from
the fishery and the university said this effort demonstrated the effectiveness
of such collaboration by collecting excellent data, cutting research costs and
– as a bonus – provide good information for the Dungeness crab fishery, which
is Oregon’s most valuable.

trust took time, but “we’ve figured out that engaging the fishermen actually
improves the data,” said Michael Harte, director of OSU’s Marine Resource
Management Program. “This is fantastic for us. It would cost many thousands of
dollars to deploy one scientific buoy, but by working with the crab fishermen,
we can deploy fixed buoys for about $100 each.”

Led by
oceanographer Kip Shearman, the researchers worked with 10 Oregon crabbers,
attaching sensors to about 60 crab pots deployed between Port Orford and
Astoria. Because many crabbers use anywhere from 300 to 500 pots, the
researchers could select locations, where the sensors recorded temperatures
every 10 minutes during the crab season (December through August). 
scanned and uploaded that information to analyze and evaluate. They later
developed larger sensors that could record both temperature and dissolved
oxygen levels in the water surrounding the crab pots. The information gleaned
is moving the scientists closer to understanding and predicting hypoxia and the
appearance of dead zones.

“Fishing has
been good to me and I’m happy to be giving something back,” Al Pazar, one of
the crabbers involved in the project, said at the time. “I love working with
OSU, and Sea Grant in particular has helped establish a good connection between
Oregon’s fishing industry and academia. It’s a no-brainer to utilize the local
volunteers from the fishing fleets and their gear.”

The project
offered valuable information for both groups, but bringing folks together who
traditionally are at odds was a plus.

“No oxygen
means dead crabs (as in 2006) or no crab, so the crab fishermen are happy to
work with us,” Harte noted. “They and their crab pots are going to be out there
anyway, and we don’t need huge research grants to tap into this ready-made
ocean observing system. We’re learning that scientists and fishermen, working
together, can collect valid scientific data in a robust way using a relatively
inexpensive system that improves our understanding of the ocean.”

researchers said dead zones with severe hypoxia formed during the summer of
2009 near the seashore on the mid- to inner shelf in coastal waters, but were
“about average” in size and duration.
“We also saw
the now-classic ribbon of low dissolved water near the seafloor extending along
the coast,” said Barth.

But the
hypoxia team observed no anoxic (zero oxygen) zones like the infamous killer
off Newport, Oregon in 2006. In early August, oxygen levels dropped as low as
0.5 milliliters per liter off Newport and Cape Perpetua – at the cusp of
“severe” – when the wind backed down and they – according to Barth – “caught a
break” that weakened and shortened the hypoxia.

They know such
luck won’t always intervene, and they point to other areas around the world –
such as the Benguela Current off South Africa and Humboldt Current off Chile –
undergoing the same process as the Pacific Northwest. Such areas, scientists
say, have historically endured hypoxic conditions, including more extreme
upwelling and more frequent marine die-offs than the Pacific Northwest. The
main concern is whether or not those similar systems are harbingers of the
future for the Pacific Northwest.


Oregon is far from alone in experiencing hypoxia zones in its coastal waters.
In 2008, scientists and researchers mapped 415 eutrophic (overly nutrient-rich)
and hypoxic coastal systems worldwide – 169 of them documented hypoxic areas
(dead zones), 233 “areas of concern,” and 13 considered “in recovery.” 

Coastal dead zones could appear every summer from now on, said Barth, because
ocean and atmospheric conditions “are now primed for their regular, repeated

The vital
concerns are how big those zones become, how long they last, and how often
oxygen levels drop to cause marine life die-offs.

OSU scientists
run regular transects off Newport using undersea gliders equipped with oxygen
sensors, as well as similar instruments aboard four moorings ranging from 15 to
80 meters (49.2 to 262.5 feet) deep.

Barth said
oceanographers’ ability to monitor and measure hypoxic conditions improves
every year, and should take a quantum leap when OSU deploys a new network of
undersea gliders and cabled moorings off the coast as part of the national
Ocean Observatories Initiative to measure the effects of climate change on the

In 2010 and
2011, hypoxic events were less severe and less widespread, with no recorded
mass die-offs of any marine life, according to PISCO. As of the end of August
2012, multiple ocean observations from various locations indicated “moderate to
severe hypoxia occurring along parts of the central Oregon shelf” from Cape
Perpetua to Newport, with the most severe levels “as usual” found south of
Newport. They expected conditions conducive to hypoxia to exist through late
September or early October.

Dillman can be reached at