Southern Hood Canal avoided a major fish kill this year, but for
a few days in September it looked like conditions were set for
low-oxygen waters to rise to the surface, leaving fish in a
critical state with no place to go, experts say.
Data from the Hoodsport buoy
show the rise of low-oxygen waters to the surface over time (purple
color in top two graphs). // Graphic:
NANOOS
Seth Book, a biologist with the Skokomish Tribe, has been
keeping a close watch on a monitoring buoy at Hoodsport. Dissolved
oxygen in deep waters reached a very low concentration near the end
of September, raising concerns that if these waters were to rise to
the surface they could suddenly lead to a deadly low-oxygen
condition. This typically happens when south winds blow the surface
waters to the north.
“I started asking around the community to see if anyone had seen
evidence of low DO (fish at surface; dead fish; deep fish being
observed or found in fishing nets at surface; diver observations)
and luckily I had no reports,” Seth wrote to me in an email.
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.
UPDATE, Sept. 26
The Hoodsport monitoring buoy was placed back online yesterday. The
dissolved oxygen levels at the surface are much higher now than
they were two weeks ago, coming up to about 9 milligrams per liter
at a 10-foot depth. But oxygen levels in the middle layer remain
about the same — about 2.5 milligrams per liter. And the middle
layer still contains less oxygen than levels close to the bottom,
which is getting an infusion of heavy seawater from the ocean.
A south wind could still bring low-oxygen waters to the surface,
but I don’t believe the levels are low enough to cause a fish kill.
Still, the low-oxygen water could force deep-water fish to move
upward in the water column. I’m waiting to hear from divers if they
are seeing anything unusual, and I’ll let you know if conditions
take a turn for the worse.
—–
Are we about to see one of the infamous fish kills that we have
observed in Southern Hood Canal in past years?
I am unable to sound any alarms at this time, but if you live in
the Hoodsport-Potlatch area or are scuba diving nearby, you might
want to watch for dead fish on the surface, rockfish or shrimp
swimming in shallow water, or wolf eels and octopuses acting
strangely.
Usually, we can look to the monitoring buoy offshore of
Hoodsport to answer questions about whether fish are starving for
oxygen. The buoy tells us about dissolved oxygen levels at all
depths. I watch this buoy every fall for clues about dangerous
conditions, such as when the surface and middle layers of Hood
Canal become depleted of oxygen.
Unfortunately, the Hoodsport ORCA buoy has been down for most of
the past 10 days. University of Washington technicians are trying
to get it back in operation, but it appears to be an
Internet/local-network problem at the moment.
As of Sept. 10, the surface layer at 10 feet deep was down to
less than 2 milligrams per liter, an alarming level, and conditions
were not much better at 66 feet. (See chart.) That means there is a
lot of low-oxygen water that could be brought to the surface when
we get a wind blowing out of the south. Well, we’ve had some
moderate south winds today, and I’m wondering what is happening out
there right now.
South winds blow the surface layer away and bring low-oxygen
water up from the depths. Fish may come to the surface seeking
better conditions, but they may find oxygen levels even worse as
they go up — and the fish have no idea that better conditions may
lie below.
So far, I have not seen any concerns posted on the Facebook
pages of divers who may have gone out recently. Feel free to post a
comment to this blog or send me an email (cdunagan@kitsapsun.com)
if you see or hear anything that can contribute to the
discussion.
A statewide hotline used to report oil spills also will take
your calls and alert biologists to reports of dead fish. That
number is (800) OILS-911.
With some luck, the UW folks will have the Hoodsport buoy back
on line in the next couple days and we’ll see if conditions have
improved or gotten worse. For now, we’ll just have to wait. The
chart is generated by the Data Explorer at the Northwest
Association of Networked Ocean Observing Systems (NANOOS). (Click
on “regions” to get to Puget Sound.)
I’m becoming something of a nerd when it comes to oxygen levels
in southern Hood Canal. I’m sure it stems from the realization that
we now have the technology to predict when fish will react to
low-oxygen conditions by swimming to the surface, acting sluggish
and sometimes dying.
Wolf eels at Sund Rocks in
Hood Canal are disturbed by low-oxygen conditions.
Photo courtesy of Pat Lynch
In a story published in
Monday’s Kitsap Sun, I took a step back from the immediate
low-oxygen conditions and discussed our knowledge of Hood Canal,
along with plans being formulated to address the low-oxygen
problem.
Low-oxygen conditions reared their ugly head during the last
week in September (Water
Ways, Sept. 27). No major fish kills were reported before
things began to improve somewhat by Friday (Water
Ways, Sept. 30).
I’m keeping my eye on the charts and graphs and noticed a couple
things that we can talk about. Compare the two oxygen profiles
below with an eye to the surface conditions at Hoodsport (blue
line) and deeper waters there below 40 meters.
Oxygen profile from Sept.
30Oxygen profile today (Oct.
5)
The first thing I noticed was that the top of the hypoxic layer
moved up from about 17 to 10 meters. That means if fish are
avoiding that low-oxygen water, they will also move up. As far as I
know, divers have not reported any observations to confirm or deny
that change. One explanation is that the heavy ocean layer at the
bottom is pushing up the entire water column. It also could mean
that the surface layer has grown thinner, such as when south winds
blow or north winds stop.
Meanwhile, the bottom of that middle hypoxic layer has moved up
from about 70 to 50 meters and the edge has smoothed. That is an
indication that the heavy ocean water, which contains more oxygen,
is mixing with the bottom of the hypoxic layer.
One may also notice that the deep water at Twanoh (turquoise
line) has become more oxygenated all the way through and is sharply
higher in oxygen at the bottom. Perhaps this is an indication that
the heavy ocean water has reached Twanoh and is mixing at the
bottom, while winds and tides mix the water at the top.
University of Washington oceanographer Jan Newton has noticed a
decline in the oxygen concentration in the middle layer at
Hoodsport. She raises the prospect that this could result, in part,
from low-oxygen water being pushed back from Lower Hood Canal by
the annual intrusion of heavy ocean water. It needs to be checked
further, she said.
I hope we get some diver observations this weekend or sooner. In
discussing the current conditions with Dan Hannifious of Hood Canal
Salmon Enhancement Group, we both wondered when deep-water fish
will move back to their normal depth. What would it take for them
to break through the middle low-oxygen layer to reach deeper water
that is higher in oxygen.
If you would like to become an armchair observer of these
conditions in Hood Canal, check out the graphs on the website of
the Hood
Canal Dissolved Oxygen Program. You’ll have to save old graphs
to compare them closely, although another graph on the Nanoos
website shows you changes in oxygen levels and other parameters
over time for selected depths. (Click on “Regions” then “Puget
Sound” and locate the Hoodsport buoy to find the graphs.)
Will the conditions in Hood Canal get better or worse this year?
I’ll let you know, but if you see something unusual, feel free to
post a comment here.
Fish and other sea creatures are finding some room to breathe in
southern Hood Canal as higher oxygen levels have returned to the
upper portion of the waterway after things looked pretty bleak on
Monday. See
Water Ways post.
I reported yesterday that fish could safely go down to 60 feet
in a story posted on the
Kitsap Sun website, but conditions are changing all the time.
Now it looks like the cutoff depth is closer to 50 feet, while
waters closer to the surface appear to be more oxygenated than
yesterday.
I discussed the situation with Dan Hannifious of the Hood Canal
Salmon Enhancement Group and included some of Dan’s comments in the
story. Rather than repeat those comments here, I’ll let you
click on the story.
What I did want to share are a couple graphs that show current
conditions as of 9:30 this morning. Most of the real-time analysis
comes from monitoring buoys in Hood Canal.
This is a profile of the
oxygen levels from the surface down to the bottom of Hood Canal, or
close to it. The blue line is for the Hoodsport buoy, turquoise for
Twanoh and green for Dabob Bay. The black line is for Carr Inlet in
South Puget Sound and purple is Point Wells near Edmonds.
Biological "stress" occurs at less than 5 milligrams per liter,
while "hypoxia" is shown at 2 mg/l. At Hoodsport, if fish go below
about 18 meters, they will be in hypoxic conditions. Earlier this
week, these condition were seen at the surface.
Data from the Hood Canal Dissolved Oxygen
Program.This graph shows changes
over time. While conditions have gotten better near the surface
(blue line), it doesn't show much change at 66 feet (green line).
As we can see in the previous graph, the changes are occurring in
shallower water and will take time to reach this depth. The red
line shows the intrusion of heavy seawater containing more oxygen.
When comparing, remember one graph uses meters, the other
feet.
Data compiled by the Integrated Ocean Observing
System
Southern Hood Canal is back to its dirty tricks again, as
dissolved oxygen concentrations have dropped to dangerous levels
even at the surface. Numerous researchers are watching to see how
these conditions play out.
A giant Pacific octopus,
which should be hiding, clings to a rock wall Saturday at Sund
Rocks Marine Preserve.
Photo by Pat Lynch
The mechanism that causes the oxygen to decline is a little
complicated, but it’s pretty well understood. It involves nitrogen,
sunlight, plankton, heavy sea water and south winds. See the story
I wrote for
today’s Kitsap Sun for a brief explanation, or check out a
story from April 12, when I described findings from a
scientific panel about the sources of nitrogen in the canal.
The graph below shows the oxygen levels at three depths near
Hoodsport. As you can see from the blue line, oxygen levels near
the surface declined rapidly over the past five days, a period when
winds blew out of the south. Levels below 2.5 milligrams per liter
are considered highly stressful for sea life.
At Hoodsport, oxygen levels rose at the 10-foot mark starting
about midday yesterday. They declined again this morning, starting
after midnight. Being close to the surface, oxygen levels in these
waters are greatly influenced by winds and waves.
Waters at 66 feet deep stayed low in oxygen but fairly stable,
as shown by the green line. Fish tend to swim into shallow waters
to avoid those low-oxygen levels. A huge mass of low-oxygen water
lies in this mid-range area.
Meanwhile, the low-oxygen waters in the middle layers are being
pushed upward by heavy seawater coming in from the ocean. That deep
ocean water contains more oxygen than the layer above it, as shown
by the red line.
To follow these changes in close to real time, go to the
Nanoos website and
click on “Click here to view all assets” then on “regions” in the
left column and “Puget Sound.” You can get information from most of
these buoys. Hoodsport is the closest to the action in southern
Hood Canal.
Five years ago, a lot of people were wondering why fish were
dying more often in southern Hood Canal during the fall.
Researchers knew that Hood Canal was sensitive to nitrogen. In
other words, when nitrogen was introduced to the canal during
summer months, nearly all of it was taken up by plankton, which
grew into large blooms. When the plankton died, they sank to the
bottom, where bacterial decay sucked up the available oxygen.
Beyond that, the questions were numerous: What were the most
critical sources of nitrogen affecting the low-oxygen problem? What
role does weather and water circulation play? And what can humans
do to help the problem — or at least keep it from getting
worse.
After a five-year, $4-million study, these questions can be
answered with some certainty, as I point out in a story in
Sunday’s Kitsap Sun. Now it is time for researchers to convey
this information to political leaders and the public, as the Hood
Canal Coordinating Council prepares a plan of action.
Scott Brewer, executive director of the HCCC, told me that the
eventual plan is likely to include a suite of actions to address
nitrogen inputs to the canal, particularly from human sources. Continue reading →
Conditions have remained pretty much the same the last couple of
days, although the intrusion of dense higher-oxygen water from the
ocean is beginning to create a thicker layer at the bottom of Hood
Canal. The middle layer of low-oxygen water remains fairly thick,
but the upper layer with higher oxygen concentrations is still
providing fish some relief. South winds remain a threat, as I’ve
explained for the last few weeks.
One can observe the three layers in the upper graph. The lower
graph shows changes over the past week or so. Notice how oxygen
concentrations are rising in the deep layer. Continue reading →
I hate to be the voice of doom, but low-oxygen conditions in
Hood Canal have never been worse — if you can believe the data
gathered since the 1950s, alongside more intense monitoring the
past several years.
In the southern portion of Hood Canal, you only need to go down
about 30 feet to begin to see stressful oxygen levels in the range
of 2 milligrams per liter. For current conditions at Hoodsport, go
directly to the Hood Canal Dissolved Oxygen Program’s website,
which lists data sent back from the Ocean Remote
Chemical Analyzer (ORCA).
Sea creatures are beginning to show signs of stress, according
to scuba diver Janna Nichols, who described her findings to me
Wednesday after a dive in Hood Canal. She talked about fish
“panting” as their gills moved in and out rapidly. Some fish,
shrimp and other sealife had moved into shallower water. Watch
Janna’s
video of a wolf eel and other visuals she captured on the
dive.
When low-oxygen conditions are that close to the surface, the
danger is that a south wind will blow away the surface layer and
bring low-oxygen water right to the surface, leaving fish with no
place to go.
Of course, I have no desire to see a massive fish kill, but we
already know that fish are probably dying in deep water due to the
stressful conditions. I collect this information and offer these
reports so that people can alert researchers when something
happens. Being on the scene when fish are dying could provide
important information about the nature of the low-oxygen problem.
For details, please check out my stories in the Kitsap Sun
Sept. 7 and
Sept. 15 as well as the more technical report
from Jan Newton on Sept. 7 (PDF 320 kb).
The phone number to report fish kills or oil spills is (800)
258-5990 or (800) OILS-911
If you haven’t heard, the worst low oxygen conditions normally
occur in the fall after a summer of burgeoning numbers of plankton,
encouraged by nitrogen and sunlight. By fall, much of the plankton
has died and dropped to the bottom, where decay consumes the
available of oxygen.
While there are plenty of natural sources of nitrogen in Hood
Canal, computer models have demonstrated that human inputs from
septic systems and stormwater can push things over the edge in the
fall.
Officials are hoping that a new sewage-treatment plant in
Belfair will begin to reduce the inputs of nitrogen into Lynch
Cove. Another treatment plant is being planned in Potlatch.
Stormwater upgrades also are being proposed for Belfair and other
areas.
The orange triangles represent
this year's composite oxygen levels for the south half of Hood
Canal. The latest reading, near the end of August, is the lowest
ever seen.
