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Dungeness crabs are one of many Puget Sound species that can be impaired by low-oxygen conditions. Photo: Crabmanners via Wikimedia Commons

Low oxygen challenge, part 1: The debate over oxygen in Puget Sound

A new report, Draft Puget Sound Nutrient Reduction Plan, is out today for public review. Experts at the Washington Department of Ecology along with many other researchers have spent years studying and debating the problem of low oxygen in Puget Sound. Now, many new developments — technical, scientific and legal — are reaching a critical stage and setting up a framework to make some major decisions. This four-part series in Our Water Ways looks back on how we have reached our present condition, including a consideration of possible solutions. Part 3 describes findings in the new report.

In Puget Sound, low oxygen levels are a proven threat to marine creatures, from fish to shellfish and even tiny organisms. This threat has long been recognized by scientists — particularly within slow-flushing bays and inlets where low levels of dissolved oxygen can impair sea life and occasionally create deadly conditions in late summer and fall.

For decades, government agencies have been studying the low-oxygen problems of Puget Sound, some natural, some man-made. Now, the Washington Department of Ecology has put together a plan to reduce the inflow of nutrients, particularly nitrogen, which can fuel a rapid growth of plankton, setting off a natural process of deoxygenation. A draft plan, released today, will be discussed in parts 3 and 4 of this series. Comments on the plan will be accepted by Ecology until Aug. 27.

Altogether, recent scientific discoveries, advances in computer modeling and a series of legal rulings have established an atmosphere for change. Ecology is pushing forward with plans to control nitrogen coming from sewage-treatment plants and from upstream sources, such as farms and urban areas. Critics on one side say Ecology has overstated the problem and failed to come up with workable solutions. Critics on the other side say actions have been taking way too long.

In this blog post and the next, I hope to describe how we got into our current situation and the factors that will help shape the future health of Puget Sound and ultimately determine which marine species will survive.

Biological effects

Pacific herring spawning in eelgrass, Holms Harbor, Whidbey Island. Photo: Florian Graner, Sealife Productions

Although we rarely see dead fish washing up on shore, marine organisms may succumb to a multitude of unseen stresses caused by low-oxygen waters, stresses that reverberate through the food web, affecting species from plankton to killer whales.

Many aquatic creatures respond to oxygen deficiency with a shift in their physiological makeup, according to Tim Essington, professor of aquatic and fishery sciences at the University of Washington. Without adequate oxygen, they may struggle to find food and avoid predators. They may become susceptible to disease and reproductive failure. Although very real, these and other effects are difficult for researchers to observe in real-world conditions.

“Organisms have a range of responses available to them to try to cope with thresholds of low oxygen,” Essington said in a presentation summarized in the Encyclopedia of Puget Sound. “Typically, they can move, acclimate, or in the worst-case scenario, they may die.” 

Essington has compared low-oxygen conditions for marine organisms to high-altitude effects on humans, an analogy supported by Mindy Roberts, director of the Puget Sound Program for Washington Conservation Action, an environmental group.

“Imagine if you were suddenly transported to the summit of Mount Rainier, where oxygen is 40 percent lower than sea level,” said Roberts, a former environmental engineer for Ecology. “In addition to finding it difficult to breathe, your cognitive processes are affected. With my climbing background, I know that this occurs.”

Some species are more tolerant of low-oxygen conditions than others. In areas of Puget Sound where oxygen levels are chronically low, some species are no longer present and those that remain are fewer in number. As scientists say, oxygen levels can affect both biodiversity and abundance, causing shifts throughout the entire food web.

Oxygen levels often decline the most at the bottom of Puget Sound, particularly in smaller bays and inlets where the habitat supports a multitude of invertebrates and fish.  As oxygen levels decline, sometimes on annual cycles, fish and other mobile species may seek more breathable waters at shallower depths, thus increasing the risk that predators will eat them. Less mobile species may acclimate over time, or they may die out.

While some researchers strive to understand the complex physiological changes at work in low-oxygen conditions, others are using computer models to better understand how nitrogen enters and flows through the waters of Puget Sound, feeding a variety of planktonic species at the base of the food web.

 Plankton are an essential food source for many higher-level animals, but excessive nitrogen can produce massive plankton blooms that overwhelm the consumptive capacity of the food web. When that happens, the excess plankton die, sink, and decay, enhancing bacterial growth that consumes the available oxygen (Encyclopedia of Puget Sound).

The latest computer models are designed to replicate the physical and biological conditions throughout Puget Sound, revealing when and where low-oxygen conditions are likely to occur. They also help researchers figure out how to rectify the problem by reducing nitrogen inputs at locations where reductions would have the greatest effect.

A large plankton bloom photographed by Ecology’s Eyes Over Puget Sound program in 2023, looking from Seattle to Bainbridge Island. Photo: Washington Department of Ecology.

A major focus of Ecology’s strategy is sewage treatment plants, most of which discharge nitrogen directly into Puget Sound. Also important are diffuse sources such as farms and housing developments, where nitrogen from fertilizers and animal wastes get into stormwater and enter rivers and streams that discharge to Puget Sound.

Computer models must also account for complex circulation patterns as well as a massive flows of nitrogen in seawater that move into Puget Sound from the ocean. This oceanic seawater, being saltier and denser than other water in Puget Sound, comes in along the bottom, as lower-density freshwater moves out at the surface. This is typical estuarine flow found in many parts of the world. Because of turbulence, some of the deeper, nitrogen-rich water mixes into the surface layers, where sunlight allows for the growth of plankton and low-oxygen conditions.

The worst conditions can be seen near the bottom in areas with low circulation, where mixing with oxygen-rich water is slow and organic decay draws down oxygen levels. Southern Hood Canal and inlets in South Puget Sound are among the vulnerable areas. These waters can, on occasion, create conditions uninhabitable to most sea life.

Ecology’s regulatory efforts to constrain human sources of nitrogen have been on a bumpy course, sometimes challenged by both environmental groups and treatment plant operators.

Most recently, Ecology’s plan to control nitrogen from sewage effluent using a new “general permit” has hit a roadblock in a ruling from the state’s Pollution Control Hearings Board. The board ruled that Ecology cannot legally require a treatment plant to comply with a general permit if the facility already operates under an individual permit, as most do. As a result, Ecology has shifted its regulatory approach, as will be explained in the final part of this series.

King County is among the local entities participating in studies of low-oxygen conditions and exploring how dissolved oxygen levels affect Puget Sound’s varied species and habitats. With billions of dollars needed to upgrade sewage-treatment plants, county officials are asking for a regional strategy focused on the most cost-effective actions.

“King County is committed to protecting Puget Sound, including addressing nutrients,” said Akiko Oda, public information officer for the county’s Wastewater Treatment Division. “We are continuing the water quality monitoring, technology evaluation and treatment planning that was originally required under the original nutrient general permit.”

Roberts, who helped develop early computer models for Ecology, is now a leader in the environmental community. It is past time, she says, to get the major sources of nitrogen under control and begin to restore the health of the waterway.

Natural and unnatural conditions in history

While some areas of Puget Sound are naturally low in oxygen, human activities have been affecting water quality since the first settlers began altering the landscape in the 1800s. References to low-oxygen problems date back to the 1920s, a time when several pulp mills were dumping their industrial wastes into local bays. Cities with one or more mills at that time include Port Angeles, Port Townsend, Shelton and Tacoma, and later Everett (1936) and Bellingham (1938).

A lumber and pulp mill in Shelton, 1947, Ellis Postcard Co. // Photo courtesy of Washington State Historical Society

Effluent from the production of pulp, used to make paper, contains chemicals that can be toxic to fish, shellfish and other organisms. In those early days, another effluent constituent, wood waste, triggered the growth of bacteria that consumed nearly all the oxygen in the vicinity of the mills, upsetting the food web and sometimes creating “dead zones” where nothing could live. Oxygen levels often remained low even after the industrial chemicals dispersed. Chemists at the time debated whether it was toxic compounds or a lack of oxygen causing the most damage to nearby oyster beds.

The Washington Pollution Control Commission, established in 1945, became the first agency authorized to rein in pollution. But early commissioners saw their role as educators more than enforcers, launching a statewide campaign called “Keep Washington Clean,” according to a 1967 article by L.A. Powe Jr. in Washington Law Review.

Commercial oyster growers, already fighting to protect their depleted beds, wanted stronger action from the commission. Scientific studies, public hearings and lawsuits became part of the battle by local oystermen, led by the Pacific Coast Oyster Growers Association.

In 1955, the Legislature imposed a permit system to control pollution, giving the commission new authorities.  “Instead of waiting for a complaint and then investigating, the commission was placed in a position where industry came to them to request permission to discharge wastes,” Powe explained.

Although oyster growers were not satisfied with the pace of progress, stricter limitations on effluent were added to permits over time, and the waters got cleaner. But getting some operations to comply with new requirements remained a concern, according to Dave Nunnallee, who joined the Washington Department of Ecology in 1969 and became an inspector.

“We had laws, but the enforcement was very weak,” Nunnallee said in an interview for a “Historically Speaking” (PDF), an Ecology publication celebrating the agency’s 35th anniversary in 2005. Nunnallee, who retired in 2006, recently recalled several investigations of untreated wastes, including those from a concrete plant in Renton, a slaughterhouse in Auburn and fish-processing plants on the Seattle’s “filthy” waterfront.

In 1973, during a growing environmental movement, the Legislature increased penalties for permit violations from $100 to $5,000 a day, strengthening Ecology’s hand with pollution, Nunnallee said.

Effects of sewage

Besides industrial effluent, state pollution officials were aware that sewage treatment plants of the 1970s were releasing organic materials that could deplete oxygen levels — particularly in small, enclosed bays. The Pollution Control Commission, whose name was changed in 1967 to the Water Pollution Control Commission, had long pushed local governments to build “primary” treatment plants to end the practice of discharging raw sewage. But when it came to organic pollutants and dissolved oxygen, the commission was more focused on lakes and rivers than on Puget Sound, Nunnallee recalled.

“Frankly, we weren’t too concerned about Puget Sound,” he said during the 2005 interview. State officials generally believed that Puget Sound, outside a few small bays, had the capacity to absorb the organic pollution, he said. For example, the costly effort to clean up Lake Washington during the 1960s was declared a tremendous success, but it led to releasing considerably more organic wastes into Puget Sound.

One of the standard tests used to quantify the effects of sewage effluent on water quality involves a calculation of “biochemical oxygen demand,” or BOD. The test typically measures the concentration of oxygen in an effluent sample at the beginning and at the end of a five-day period. The result represents the amount of oxygen required for bacteria to break down organic waste in the sample — a rough indicator of the environmental impact. The BOD of raw sewage is typically 300-600 milligrams per liter.

In the midst of an environmental movement that began in the 1960s, Congress took an ambitious leap to clean up the nation’s waters by passing the Clean Water Act of 1972. This powerful law has elicited profound changes in regulations by federal, state and local governments — right up to today.

Among its many provisions is a requirement that sewage treatment plants nationwide be upgraded to reduce organic pollutants and improve oxygen conditions. Federal water-quality standards were established based on the capability of existing treatment systems — which could produce effluent with an average BOD less than 45 milligrams per liter. These standards and the processes that could meet them became known as “secondary treatment.” Initially, municipalities were given until 1977 to begin construction on the upgrades, although deadlines were extended, and federal waivers were allowed when warranted by water conditions.

At first, Washington state officials refused to push for secondary treatment for facilities discharging into Puget Sound, Nunnallee said. Studies at the time failed to show that major problems resulted from sewage effluent, except in the immediate vicinity of the outfall, he noted. “So, we encouraged the entities to apply for their waivers, not thinking it was that big a water-quality issue.”

By 1983, with concerns growing over pollution in Puget Sound, proponents of sewer upgrades argued that state law mandated improvements, specifically because secondary treatment was well-proven technology. They cited the water pollution law of 1945:

“Section 1. It is declared to be the public policy of the State of Washington to maintain the highest possible standards to insure the purity of all waters of the state consistent with public health and public enjoyment thereof … and to that end require the use of all known available and reasonable methods by industries and others to prevent and control the pollution of the waters of the State of Washington (emphasis added).”

Amendments in 1967 had changed the law slightly to require wastes to undergo “all known, available, and reasonable methods of treatment prior to their discharge,” but the intent has remained the same since 1945. This idea of keeping the waters as clean as possible imposed what became known as a “technology-based standard,” which Ecology must enforce “regardless of the quality of the water,” according to the statute. Many lawsuits would follow, and AKART — “all known, available, and reasonable treatment” — appeared in legal documents again and again right up to recent court rulings, which will be discussed in the next part of this series.

Donald Moos, director of Ecology in 1983, asked for a state attorney general’s opinion to determine whether the language of the law would expressly require secondary treatment at all sewage facilities in Washington state.

In his response, Attorney General Ken Eikenberry said “secondary treatment” is not specifically defined in the law. So, while the law clearly calls for modern treatment technology, it must also be “known,” “available,” and “reasonable.” This is an engineering, not a legal question, he said in his legal opinion.

“A review must be conducted by the department of existing engineering technologies in order to enable it to decide which methods of treatment … are suitable with respect to the waste situation involved in the particular case,” Eikenberry stated.

After a review by Ecology officials, the agency drafted a policy defining water quality standards that were consistent with secondary treatment. Although some treatment plant operators objected, the standards were generally upheld by the state’s Pollution Control Hearings Board. As a result, the issue of feasible technology (AKART) has become a factor in setting effluent limits in permits for all sewage treatment plants.

“The basic problem, however, was that most of us in Ecology didn’t feel that secondary treatment was needed, and ultimately we were proved wrong,” Nunnallee said in the 2005 interview. Secondary treatment, now the universal standard, has effectively reduced the discharge of organic pollutants into Puget Sound. But the typical secondary-treatment process does little to reduce nitrogen, which can trigger the rapid growth of plankton and produce low-oxygen conditions. The question of what should be done to control nitrogen in Puget Sound has been engaging a host of scientists while prompting legal battles along the way. 

This article was funded in part by King County in conjunction with a series of online workshops exploring Puget Sound water quality. Its content does not necessarily represent the views of King County or its employees. 

The series

Part 1: The debate over oxygen in Puget Sound

Part 2: Water-cleanup plans and the search for ‘reasonable’ actions

Part 3: Computer models spell out the extent of the water-quality problem.

Part 4: Many actions may be needed to improve Puget Sound waters

2 Replies to “Low oxygen challenge, part 1: The debate over oxygen in Puget Sound”

  1. I support scientific study and scientific resolution of the problem. I live on the Sound and still do not feel that it is safe enough for swimming, etc.

  2. After many years of traveling the world on the ocean and much of my research on what happened to the abundance of marine life in my eariler years, has caused me to realize that where ever there is human populations there is ocean floor anoxic conditions or in fresh water creeks, rivers and lakes in some degree of deterioration.
    I have been working on a means to convert the anoxic / hypoxic ocean and lake floors to compost and get growing again.
    Please contact me if you may wish to learn more as I continue to develop my Ocean Floor Composter.