Tag Archives: nitrogen

Orange plankton bloom is not a good sign for ecological health

If you notice an orange tint to the waters of Central Puget Sound, it’s not your imagination. It is a dense plankton bloom dominated by the dinoflagellate Noctiluca scintillans.

Noctiluca scintillans bloom comes ashore at Saltwater State Park in Des Moines on Monday of this week.
Video: Washington Department of Ecology

Noctiluca is often seen in some numbers at this time of year, but it may be a bit more intense this time around, according to Christopher Krembs, an oceanographer with the Washington Department of Ecology. Christopher tells me that the orange color may stick around awhile.

The orange-colored species does not produce any toxins found to be harmful to humans, but it is not exactly a friendly organism either. It often shows up in marine waters that are out of balance with nutrients or impaired in some other way. It can gobble up other plankton that feed tiny fish and other creatures, but it does not seem to provide a food supply that interests very many species — probably because of its ammonia content. Consequently, Noctiluca is often referred to as a “dead end” in the food web.

A plankton bloom at the north end of Vashon Island gets a distinct edge from the tidal currents flowing through Colvos Passage.
Photo: Eyes Over Puget Sound, Ecology

I had a lot of discussions with Christopher and other plankton biologists earlier this year while writing a series of articles about the importance of plankton to the entire Puget Sound food web — right up to orcas. A primary point to the series was to describe how excessive nitrogen from human sources may be upsetting the balance in Puget Sound.

For a deeper dive into plankton, please take a look at this package of stories in the Encyclopedia of Puget Sound titled “Nutrient Pollution,” with a special focus on plankton in the second story in this list:

Christopher Krembs manages a program that assesses water conditions throughout Puget Sound, including aerial views of the surface waters, where he often observes different types of plankton, as well as jellyfish and other creatures that provide clues to water quality. See the webpage Eyes Over Puget Sound, where he expects to post his latest report next week.

The waters in Budd Inlet turned green from a plankton bloom near Olympia.
Photo: Eyes Over Puget Sound, Ecology

His flight on Monday revealed intense blooms of Noctiluca throughout Central Puget Sound, including the waters near Vashon Island.

“What is striking is the very high phytoplankton biomass in Central Sound and not so much in South Sound and other places from the air,” Christopher said in an email. “The jury is still out when the monitoring data come in.”

He’s not sure why the Noctiluca bloom is occurring right now. May was a record-dry month, he noted, and rain-fed rivers are running low. On the other hand, snow-fed rivers are running fairly high, while the mighty Fraser River in British Columbia has dropped down from its previous levels.

Rivers can bring nitrogen down from the uplands to feed the phytoplankton, which capture the energy of the sun to grow and multiply rapidly.

As Christopher points out, we need more studies focused on the base of the food web, which supports our salmon populations and ultimately thousands of species in and around Puget Sound. Clues that could help us understand how to recover Puget Sound are likely to be hidden in the water, where basic biological responses result from water chemistry and circulation patterns throughout Puget Sound.

As a result of the current Noctiluca bloom, the Department of Ecology has posted a discussion as part of its “Puget Sound Nutrient Watch” series on the blog ECOconnect. Efforts to reduce nutrient loading in Puget Sound are being discussed in a workgroup called the Puget Sound Nutrient Forum, which anyone can follow online or in person.

Nitrogen and plankton: Do they hold the missing keys to the food web?

In a way, some of Puget Sound’s most serious ecological problems have been hiding in plain sight. I have been learning a lot lately about plankton, an incredibly diverse collection of microscopic organisms that drift through the water, forming the base of the food web.

Sources of nitrogen in Puget Sound (click to enlarge)
Graphic: Washington Department of Ecology

To put it simply, the right kinds of plankton help to create a healthy population of little fish that feed bigger fish that feed birds and marine mammals, including the endangered Southern Resident killer whales. On the other hand, the wrong kinds of plankton can disrupt the food web, stunt the growth of larger creatures and sometimes poison marine animals.

OK, that’s a bit of an oversimplification, but Puget Sound researchers are just beginning to understand the profound importance of a healthy planktonic community to support a large part of the food web. That’s one of the main points that I try to bring out in five stories published today in the Encyclopedia of Puget Sound. I am grateful to the many researchers who have shared their knowledge with me.

Average daily nitrogen coming in from rivers and wastewater treatment plants (1 kg = 2.2 pounds)
Graphic: Washington Department of Ecology

These stories tie together several major issues all related to nutrients — mainly nitrogen — that feed the marine phytoplankton, which use their chlorophyll to take energy from the sun as they grow and multiply. In the spring and summer, too much nitrogen can mean too much plankton growth. In turn, excess plankton can lead to low-oxygen conditions, ocean acidification and other significant problems.

The complex interplay of planktonic species with larger life forms in Puget Sound is still somewhat of a mystery to researchers trying to understand the food web. As part of the effort, the Washington Department of Ecology is working on a computer model to show how excess nitrogen can trigger low-oxygen conditions in the most vulnerable parts of the Salish Sea, such as southern Hood Canal and South Puget Sound.

Areas of Puget Sound listed as “impaired” for dissolved oxygen (click to enlarge)
Graphic: Washington Department of Ecology

Stormwater is often cited as the most serious problem facing Puget Sound, and we generally think of bacteria and toxic chemicals flowing into the waterway and causing all sorts of problems for the ecosystem. But stormwater also brings in nitrogen derived from fertilizers, animal wastes and atmospheric deposits from burning fossil fuels. Stormwater flows also pick up natural sources of nitrogen from plants and animals that end up in streams.

Sewage treatment plants are another major source of human nitrogen. Except for a few exceptions, not much has been done to reduce the release of nutrients from sewage-treatment plants, which provide not only nitrogen but also micronutrients such as vitamins and minerals. Some experts suspect that nutrients other than nitrogen help to determine which types of plankton will dominate at any given time.

I plan to follow and report on new scientific developments coming out of studies focused on the base of the food web. Meanwhile, I hope you will take time to read this package of related stories:

Hood Canal report compiles oxygen studies

Despite millions of dollars spent on research in Hood Canal, the precise causes of low-oxygen problems in Southern Hood Canal are still not fully understood, according to a report released this week by the U.S. Environmental Protection Agency and the Washington Department of Ecology.

News articles about the report have created some confusion, and I’ll get to that in a moment.

As I reported in Tuesday’s Kitsap Sun, research has not proven that nitrogen from human sources is responsible for a decline in oxygen levels greater than 0.2 milligrams per liter anywhere in Hood Canal. That number is important, because it is the regulatory threshold for action under the Clean Water Act.

Mindy Roberts, one of the authors of the report, told me that scientists who have worked on the low-oxygen problem have gained an appreciation for Hood Canal’s exceedingly complex physical and biological systems. So far, they have not come to consensus about how much human inputs of nitrogen contribute to the low-oxygen problems in Lower Hood Canal.

The report, which examined the complexity and scientific uncertainty about these systems, seems to have generated some confusion, even among news reporters. I think it is important to understand two fundamental issues:

1. The deep main channel of Hood Canal is almost like a separate body of water from Lower Hood Canal (also called Lynch Cove in some reports). This area is generally defined as the waters between Sisters Point and Belfair. Because Lower Hood Canal does not flush well, low-oxygen conditions there are an ongoing and very serious problem.

2. Fish kills around Hoodsport cannot be equated or even closely correlated with the low-oxygen conditions in Lower Hood Canal. The cause of these fish kills was not well understood a decade ago, but now researchers generally agree that heavy seawater coming in from the ocean pushes up a layer of low-oxygen water. When winds from the south blow away the surface waters, the low-oxygen water rises to the surface, leaving fish no place to go.

I’m not aware that researchers were blaming nitrogen from septic systems for the massive episodic fish kills, as Craig Welch reports in the Seattle Times. At least in recent years, most researchers have understood that this was largely a natural phenomenon and that human sources of nitrogen played a small role, if any, during a fish kill.

The question still being debated is how much (or how little) humans contribute to the low-oxygen level in the water that is pushed to the surface during a fish kill and whether there is a significant flow of low-oxygen water out of Lower Hood Canal, where oxygen conditions are often deadly at the bottom.

The new report, which was reviewed by experts from across the country, concludes that fish kills can be explained fully without considering any human sources of nitrogen. Evidence that low-oxygen water flows out of Lower Hood Canal in the fall is weak, the report says, though it remains a subject of some debate.

“We have not demonstrated that mechanism to their satisfaction,” Jan Newton of the Hood Canal Dissolved Oxygen Program told me in an interview. “We never said it caused the fish kill, only that it can reduce the oxygen level below what it was. In some years, it wouldn’t matter, but in some years it would make it worse.”

A cover letter (PDF 83 kb) to the EPA/Ecology reports includes this:

“While the draft report concludes that although human-caused pollution does not cause or contribute to the fish kills near Hoodsport, our agencies strongly support additional protections to ensure that nitrogen and bacteria loadings from human development are minimized.

“Water quality concerns extend beyond low dissolved oxygen and include bacteria and other pathogens that limit shellfish health. Overall, human impacts to Hood Canal water quality vary from place to place and at different times of year. Hood Canal is a very sensitive water body and people living in the watershed should continue their efforts to minimize human sources of pollution.”

One of the most confounding factors is the large amount of nitrogen born by ocean water that flows along the bottom of Hood Canal. An unresolved but critical questions is: How much of that nitrogen reaches the surface layer, where it can trigger plankton growth in the presence of sunlight?

Plankton growth is a major factor in the decline of oxygen levels, because plankton eventually die and decay, consuming oxygen in the process.

Human sources of nitrogen often enter Hood Canal at the surface, but researchers disagree on how much of the low-oxygen problem can be attributed to heavy seawater that reaches the sunny euphotic zone near the surface.

Here are the principal findings in the EPA/Ecology report, “Review and Synthesis of Available Information to Estimate Human Impacts to Dissolved Oxygen in Hood Canal” (PDF 3.8 mb).

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Hood Canal report finds septic systems a problem

An investigation into the causes of low-oxygen conditions in Hood Canal is coming to a close with this week’s release of a final report by the Hood Canal Dissolved Oxygen Program.

The pattern of fall oxygen levels show severely depleted waters from Twanoh State Park to Hoodsport with much better conditions to the north. (Click to enlarge.)
Map courtesy of Hood Canal Dissolved Oxygen Program

I described the report in general terms in a story published in yesterday’s Kitsap Sun. You may read the report for yourself at the HCDOP website.

What the five-year study learned about Hood Canal seems quite impressive. The full report contains extensive discussions about what causes oxygen to decline, the triggering mechanism for fish kills, the inputs of nitrogen that drive the system and much more.

One of the conclusions, which I focused on in my latest story, is that nitrogen from septic systems in Southern Hood Canal appears to be a pivotal factor in fish kills. When the natural decline in oxygen approaches a dangerous range, the added nitrogen from septic systems can tip the balance, causing excessive stress and sometimes death for marine creatures.

According to the report, one cannot easily separate the natural factors from the human factors that create problems in Hood Canal. The long, narrow fjord is flushed slowly compared to most marine systems. Organic carbon and nitrogen, which are the major players in oxygen decline, naturally come in from streams, groundwater and the Pacific Ocean. Numerous human sources, such as septic systems and fertilizers, must be taken into account.

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How do we address Hood Canal’s oxygen deficit?

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.
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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.

Ocean conditions are playing tricks on Hood Canal

Hood Canal continues to baffle us humans with scenarios that we have never seen before, as I outline in a story in today’s Kitsap Sun. The canal’s latest failing is to forget that, by this time of year, there is supposed to be a layer of dense, oxygenated water lying on the bottom.

I’m being facetious, of course, about how the canal is “supposed to” behave. The fact that researchers are seeing something for the first time in Hood Canal does not mean it has never occurred before. And the fact that natural conditions can be highly variable does not mean that human inputs of nitrogen have no influence over the life or death of sea creatures.

As it has been explained to me, in years when natural conditions push Hood Canal close to the danger zone, human factors can push it over the edge. So limiting nitrogen flowing into the canal can make a real difference, especially in years when natural factors gang up to deplete the oxygen supply.

As I explained in some detail in today’s story, conditions in Hood Canal the past 18 months have been interesting to watch. Early in 2009, the average dissolved oxygen in the canal was near record highs, then the level dropped rapidly to measurements at or below what is normally seen in the fall. Over the winter, the levels never came back up — which is something never observed before. Now the levels are beginning to drop again, and we don’t know how low they will go.

What is encouraging about all the monitoring and studies conducted the past few years is that we can actually measure what is happening in real time, and we are in a better position to explain why the canal is responding as it does. Now if only we could predict the weather and ocean conditions, which seem to have a mind of their own …

Let me make some observations about Hood Canal

I had fun writing a piece for Sunday’s paper about the crazy and not-so-crazy ideas for fixing Hood Canal’s dissolved oxygen problem.

If you subscribe to the printed newspaper or buy it on the newsstand, you were able to see a giant graphic drawn by Jon Williams of our staff. I’m hoping that Jon can link his artwork to the online text in the next day or so. Meanwhile, you can view the text by itself on the Web site.

You may have heard some of these ideas before: digging a trench to North Bay, dredging out the raised “sill” that blocks flow, removing the Hood Canal bridge to increase mixing, skimming off algae with a boat, increasing natural algae-eaters such as clams and oysters, and pumping large amounts of air or oxygen into the water.

I also wrote a more serious story, pointing out unfinished work for the Hood Canal Dissolved Oxygen Program and questioning what kind of actions may be made and who will make them.

That story gathered a lot of comments, as Hood Canal stories generally do. I’d like to respond with several points of my own on issues that have been raised since the first story from June 30:

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