In what is becoming an annual event, portions of Hood Canal have
changed colors in recent days, the result of a large bloom of
armored plankton called coccolithophores.
Coccolithophore from Hood
Canal’s Dabob Bay viewed with scanning electron microscope.
Image: Brian Bill, Northwest Fisheries Science
Center
Teri King, a plankton expert with Washington Sea Grant, has been
among the first to take notice of the turquoise blooms each year
they occur.
“Guess who is back?” Teri wrote in the blog
Bivalves for Clean Water. “She showed up June 24 in Dabob Bay
and has been shining her Caribbean blueness throughout the bay and
spreading south toward Quilcene Bay.”
Yesterday, I noticed a turquoise tinge in Southern Hood Canal
from Union up to Belfair, although the color was not as intense as
I’ve seen in past years.
The color is the result of light reflecting off elaborate
platelets of calcium carbonate, called coccoliths, which form
around the single-celled coccolithophores. The species in Hood
Canal is typically Emiliania huxleyi.
Death came early to Hood Canal this year, demonstrating just how
odd and unpredictable ocean conditions can be.
Fish kills caused by low-oxygen conditions in southern Hood
Canal usually occur in late September or October. That’s when
low-oxygen waters near the seabed are pushed upward by an intrusion
of heavier water coming in from the Pacific Ocean and creeping
along the bottom. Winds out of the south can quickly blow away the
surface waters, leaving the fish with no escape.
That’s basically what happened over the past month, as
conditions developed about a month earlier than normal. South winds
led to reports of fish dying and deep-water animals coming to the
surface to get enough oxygen, with the worst conditions occurring
on Friday. Check out the video on this page by Seth Book, a
biologist with the Skokomish Tribe, who found deep-water ratfish
swimming near the surface.
The story of this year’s strange conditions actually begins
about a year ago and involves a 1,000-mile-long “blob” of unusually
warm ocean water off the West Coast. State Climatologist Nick Bond,
who coined the term “blob,” explains its formation in an article in
Geophysical
Research Letters with a summarized description by Hannah Hickey
in
UW Today.
The warm, low-density coastal waters related to the blob came
into Hood Canal on schedule last fall, but they were not dense
enough to flush out the low-oxygen waters, according to University
of Washington oceanographer Jan Newton.
Hood Canal entered 2015 with the least-dense waters at depth
over the past 10 years. They remained in a hypoxic state, meaning
that levels were below 2.5 parts per million. Sea creatures unable
to swim away can be unduly stressed and unable to function normally
at that level. Conditions worsened into the summer, when the
hypoxic layer at Hoodsport grew to about 300 feet thick.
By then, the annual intrusion of deep seawater with somewhat
elevated oxygen levels was on its way into Hood Canal, spurred on
by upwelling off the coast. This year’s waters are more normal in
density, though their arrival is at least a month early. By August
9, the hypoxic layer at Hoodsport was reduced from 300 to 60 feet,
pushed upward by the denser water.
It’s always interesting to see this dynamic play out. The layer
of extreme low-oxygen water becomes sandwiched between the
higher-oxygen water pushing in from the ocean and the surface
water, which ordinarily stays oxygenated by winds and incoming
streams. Without south winds, the middle low-oxygen layer
eventually comes up and mixes into the surface layer.
If south winds come on strong, however, the surface layer is
blown to the north, causing the low oxygen water to rise to the
surface. Fish, shrimp and other creatures swim upward toward the
surface, trying to stay ahead of the rising low-oxygen layer. When
the low-oyygen layer reaches the surface, fish may struggle to
breathe in the uppermost mixing layer. Unfortunately, the fish have
no way of knowing that safer conditions lie down below — beneath
the low-oxygen layer and within waters arriving from the ocean.
Jan Newton reported that the low oxygen levels in southern Hood
Canal earlier this year were the most extreme measured over the
past 10 years. So far, however, the fish kills don’t seem as bad as
those in 2003, 2006 and 2010, she said.
The graph below shows how the deep layer coming in from the
ocean at 279 feet deep contains more oxygen than the middle layer
at 66 feet deep. The surface layer, which normally contains the
most oxygen, dipped to extremes several times near the beginning of
August and again on Friday, Aug. 28. These data, recorded from a
buoy near Hoodsport, are considered unverified.
Hood Canal Coordinating Council is undertaking an effort to
bring average residents into the discussion about how to preserve
the Hood Canal ecosystem.
While Hood Canal is becoming known for its low-oxygen problem
and occasional fish kills, it’s good to remember that the canal
remains famous for its shrimp, oysters and crabs. Furthermore,
history tells us that the canal once abounded in sealife, including
all kinds of salmon and bottomfish.
Can the canal ever come close to its heyday? I don’t know, but
plenty of people would like to give it a try. (By the way, if you
want to argue that the problems are caused entirely by
over-fishing, we’ll need to discuss individual species — including
those that aren’t harvested at all.)
The underlying premise of the Hood Canal Integrated Watershed
Management Plan is that people can find ways to benefit from a
healthy ecosystem, that natural processes — including the survival
of plants and animals — can continue without wrecking the
lifestyles of humans. Check out my story in the
Kitsap Sun Oct. 26 for an overview of this project.
Incidents of hypoxia have increased 30-fold since 1960,
according to the report. The new federal review describes the
causes of hypoxia, discusses past and ongoing research efforts and
lays out policy recommendations to deal with the problem. Eight
troubled waterways are reviewed as “case studies.”
In a
news release (PDF 116 kb) accompanying the report, Jane
Lubchenco, administrator of the National Oceanic and Atmospheric
Administration, offered these comments regarding hypoxia and the
seasonal low-oxygen area off the coast of Washington and
Oregon:
“The report shows good progress on research into the causes of
hypoxia and the specific management requirements to restore systems
such as the Gulf of Mexico and Chesapeake Bay, but we still have a
long way to go to reduce this environmental threat. The discovery
of a new seasonal hypoxic zone off the coast of Oregon and
Washington that may be linked to a changing climate emphasizes the
complexity of this issue.”
That West Coast dead zone is now ranked the second largest in
the United States and the third largest in the world. Federal
officials say there may be serious consequences to the ecological
health of the region.
Lisa Jackson, administrator of the Environmental Protection
Agency, said the EPA is proud to have played a role in the research
leading up to the report:
“These growing dead zones endanger fragile ecosystems and
potentially jeopardize billions of dollars in economic activity.
This science can be the foundation for measures that will preserve
our waters and reverse the trend, including innovative,
watershed-based solutions to this challenge.”
Mike Lee, a reporter with the
San Diego Union-Bulletin, interviewed Tony Koslow, who studies
low-oxygen areas at the Scripps Institution of Oceanography.
“This is a large phenomenon not due to nutrient outflows” from
land, Lee quoted Koslow as saying. “The big question is, ‘Is this
due to climate change?’ ”
As the oxygen-rich surface layers warm up, they mix less with
colder layers down deep where oxygen levels are low, Koslow said.
Global climate models predict that the oxygen levels in deep oceans
will decline 20 to 40 percent the next century.
“There are substantial ecosystem concerns,” Koslow said. “A
number of species that live in the deep ocean are very sensitive to
changes in oxygen levels. These species — although they are not of
commercial interest — are prey to squid, fish, marine mammals and
seabirds, so changes in oxygen will have repercussions throughout
the food web.”
The report suggests these policy actions:
Develop and implement cost-effective and scientifically
sound nutrient reduction strategies to achieve healthy water
quality in rivers, lakes and coastal waters.
Improve ecosystem models to assess how hypoxia
affects commercially important fish populations in order to
refine management strategies to protect coastal economies.
Improve scientific understanding for emerging sites such
as the Oregon and Washington shelf, where hypoxia may be
driven primarily by events linked to climate change. This
knowledge will help managers mitigate impacts on natural
resources and coastal economies.
Expand stream and river monitoring to document extent
and sources of nutrients and progress in achieving management
goals. This can lead to more strategic and effective targeting
of
nutrient reduction actions.
More systematically monitor oxygen levels in coastal
waters using new technologies and observing systems. This is
critical for forecast model development, fisheries management,
and determining nutrient reduction success.
