Tag Archives: dissolved oxygen

Puget Sound freshens up with a little help from winter snowpack

In the latest “Eyes Over Puget Sound” report, one little note caught my attention: “Puget Sound is fresher than it’s ever been the past 17 years.”

Jellyfish are largely missing this fall from Puget Sound. Some patches of red-brown algae, such as this one in Sinclair Inlet, have been observed.
Photo: Washington Department of Ecology

At least temporarily, something has changed in the waters of Puget Sound over the past few months. It may not last, but it appears to be a good thing.

The monthly EOPS report, compiled by a team of state environmental experts, lays out recent water-quality data for the Department of Ecology. The report also includes personal observations, aerial photographs and scientific interpretations that keep readers abreast of recent conditions while putting things in historical context.

The “fresh” conditions called out in the report refers to the salinity of Puget Sound, which is driven largely by the freshwater streams flowing into the waterway. The reference to 17 years is a recognition that the overall salinity hasn’t been this low since the current program started 17 years ago.

Dissolved oxygen, essential to animals throughout the food web, was higher this fall than we’ve seen in some time. Hood Canal, which I’ve watched closely for years, didn’t come close to the conditions that have led to massive fish kills in the past. The only problem areas for low oxygen were in South Puget Sound.

Water temperatures in the Sound, which had been warmer than normal through 2015 and 2016, returned to more average conditions in 2017. Those temperatures were related, in part, to the warm ocean conditions off the coast, often referred to as “the blob.” In South Puget Sound, waters remained warm into October.

Why is the water fresher this fall than it has been in a long time? The reason can be attributed to the massive snowpack accumulated last winter, according to oceanographer Christopher Krembs, who leads the EOPS analysis. That snowpack provided freshwater this past spring, although rivers slowed significantly during the dry summer and continued into September.

“We had a really good snowpack with much more freshwater flowing in,” Christopher told me, adding that the Fraser River in southern British Columbia was well above average in July before the flows dropped off rapidly. The Fraser River feeds a lot of freshwater into northern Puget Sound.

Freshwater, which is less dense than seawater, creates a surface layer as it comes into Puget Sound and floats on top of the older, saltier water. The freshwater input fuels the circulation by generally pushing out toward the ocean, while the heavier saltwater generally moves farther into Puget Sound.

“The big gorilla is the upwelling system,” Christopher noted, referring to the rate at which deep, nutrient-rich and low-oxygen waters are churned up along the coast and distributed into the Puget Sound via the Strait of Juan de Fuca. Lately, that system has been turned down to low as a result of larger forces in the ocean.

In an advisory issued today (PDF 803 kb), NOAA’s Climate Prediction Center says a weak La Niña is likely to continue through the winter. For the northern states across the country, that usually means below-average temperatures and above-average precipitation. (It’s just the opposite for the southern states.)

With a favorable snowpack already accumulating in the mountains, experts can’t help but wonder if we might repeat this year’s conditions in Puget Sound over the next year.

Christopher told me that during aerial flights this fall, he has observed fewer jellyfish and blooms of Noctiluca (a plankton known to turn the waters orange) than during the past two years. Most people think this is a good thing, since these organisms prevail in poor conditions. Such species also have a reputation as a “dead end” in the food web, since they are eaten by very few animals.

Christopher said he noticed a lot of “bait balls,” which are large schools of small fish that can feed salmon, birds and a variety of creatures. “I assume most of them are anchovies,” he said of the schooling fish.

I would trade a jellyfish to get an anchovy on any day of the year.

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Will Hood Canal experience a fish kill this year?

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.
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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.

Low 02 9-17

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.)

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Oxygen levels improve in Hood Canal past few days

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

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Oxygen in Hood Canal reaches dangerous levels

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.

In addition to the low-oxygen problem, Hood Canal was closed to the harvest of oysters after people became sick from vibriosis, a natural bacteria that multiplies in warm conditions. See Kitsap Sun story Sept. 10 and Washington Department of Health maps.

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.

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