case study lake washington an environmental success story

Dr. Edmondson saved Lake Washington

Think of W. Thomas Edmondson when you look at the clear water of Lake Washington.

The University of Washington scientist whose research saved the lake and led to the inception of Metro, died Tuesday (Jan. 11) of cardiac arrest. He was 83.

He wrote in 1975, "I felt this was a normal part of my work as a university professor whose job, as I see it, is to find out things and tell people about them."

What Dr. Edmondson told people about Lake Washington in the mid-1950s became a blueprint for the way environmental science could change public policy, earning him the highest recognition his profession had to offer.

This was the flow of history:

The lake was dying. Chemicals from sewage-treatment plants along the lake had made the once-clear water cloudy. Stinking masses of algae were washing up on beaches.

Near the beginning of his career as a zoologist specializing in fresh-water biology in 1955, Dr. Edmondson identified the problem and what it would take to clean up the lake. Based on his findings, voters formed the Municipality of Metropolitan Seattle in 1958 and eventually ponied up what in 1965 was a near-unthinkable $165 million to resuscitate the lake.

"It was quite an amazing accomplishment for the 1950s, to be so convincing to the general population that they saw the need to do something based on science," said colleague Kathryn Hahn, UW zoology department administrator.

At one time, there was a whimsical proposal to rename Lake Washington "Lake Edmondson," recalled his wife, Yvette.

Although he had an outwardly formal bearing - he was rarely seen without a jacket and tie - Dr. Edmondson was known as "Tommy" and remembered as an elfin man with bright-blue eyes who never had an unkind word for anyone.

He was elected to the National Academy of Sciences in 1973 and a seat on its Environmental Studies Board. He also won a slew of major awards, including the highest in his field, the Naumann-Thienemann Medal of the International Society for Theoretical and Applied Limnology.

Born in Milwaukee in 1916, he walked with his mother along the shores of Lake Michigan at the age of 2. When the family moved to Indiana, Dr. Edmondson wrote, "For a long time every afternoon at the same hour I walked out of the house, tried hard to find the lake, and was reduced to tears by failure."

He earned his undergraduate and doctoral degrees at Yale, then lectured at Harvard for three years before coming to Seattle with his wife, who was also a respected figure in the same field.

Although university regulations forced Dr. Edmondson to retire at the age of 70, he continued to do research for the rest of his life.

An auto accident last August left Dr. Edmondson a paraplegic, his wife said. But that did nothing to diminish his drive for researching Lake Washington.

"Even in the hospital after the accident, he was talking about, `We have to get on this and get these papers done,' " Hahn said.

"He was an inspiration," said research scientist Arni Litt. "Some of my love of science comes from him. I started working with him right out of college and stayed with him all the way through (my career). He instilled that kind of loyalty in people."

Dr. Edmondson is also survived by a brother, Frank Edmondson, of Bloomington, Ill. No services have yet been planned.

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What does Lake Washington’s warming mean for its future?

ABOARD THE SOUNDGUARDIAN, Lake Washington — The region’s cold, watery heart is nestled between Seattle and the Eastside. It uniquely supports two major roadways atop floating bridges, has offered beachgoers a summertime respite for decades and is central to the identity of the Seattle area’s culture.

But Lake Washington is changing — by over half a degree Fahrenheit each recent decade. In fact, since 1963, the lake’s surface from June to September has warmed about 4.3 degrees , according to data collected and analyzed by King County and the University of Washington.

While some of the lake’s warming can be attributed to natural, long-term climate variations in the Pacific Ocean , global climate change due to greenhouse gas emissions is definitely playing a role in heating up the lake, said Curtis DeGasperi, a King County water quality engineer who manages the lake’s monitoring program.

The lake has warmed up earlier in the year and taken longer to cool down in the fall and winter months, which have even shown a modest warming trend , DeGasperi said.

“It’s not going to be the same lake. It’s going to change, and trying to anticipate and prepare for it requires people to sit around and think about it,” he said. “We know, it’s definitely going to be warmer. There is no doubt about that.”

It’s not clear exactly what the warming trend will mean for the hundreds who flock to Lake Washington each summer for easy access to swimming and boating. Even with the region’s population growth, the lake has become cleaner. With wastewater infrastructure, the nutrients that feed algae, which can cause blooms and adverse conditions, have declined in the past two decades, bucking the trend seen in most urban waterways.

But warmer waters are decidedly harmful for endangered salmon that rely on cold, well-oxygenated water to survive, and Lake Washington has seen more days when its surface water has risen above what salmon can tolerate.

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In each of the past 10 years the lake has experienced more than 40 days each summer when its surface has exceeded 68 degrees Fahrenheit. That can be compared with only three years of such warm temperatures between 1960 and 1980, according to an analysis by the county and University of Washington.

That surface water is what ends up flowing into the Ship Canal, which connects the lake to Puget Sound through the Ballard Locks, DeGasperi said. During the summer and fall months, that warm water in the roughly 30-foot-deep commercial and recreational passageway becomes a migration barrier for the adult and juvenile salmon trying to pass through — either vying for a chance to reproduce upstream or swimming toward their adult lives in the ocean.

What did it used to look like?

Lake Washington wasn’t always like it is today.

Between the 1940s and 1960s, over 20 billion gallons of untreated sewage flowed freely into the lake each year. People could barely see a few feet into the water, beaches were closed frequently and algae blooms turned the lake a “reddish” color, King County Ecologist Daniel Nidzgorski said.

The lake experienced a near-miraculous reversal after King County built two wastewater treatment plants — one at Discovery Park and the other in Renton.

By the 1980s, the pollution streaming into the lake shrunk to 2.3 billion gallons a year , and last year, 1.7 billion gallons of untreated stormwater and sewage flowed into Puget Sound and Lake Washington. Ongoing projects aim to decrease that amount further.

Lake Washington is a success story that’s equal parts luck and municipal planning, Nidzgorski said.

Investments in stormwater infrastructure have paid off, and now decades later the water is cleaner and clearer than it’s ever been in modern Seattle history. In a round of budget cuts in 2009, the county even stopped analyzing bacteria in its samples, concluding that the levels weren’t changing enough to make it worth measuring, he said.

“What we’re doing is actually working,” Nidzgorski said. “It’s really good news that we’ve been putting in a lot of new regulations, better technology, just better practices.”

But that doesn’t mean challenges for the future won’t exist. Longer summers mean that the lake’s period of stratification — when the water column forms distinct layers that barely mix — will be longer . Currently this has primarily been a problem in Lake Sammamish , where kokanee salmon and their predators are forced into a narrow band of breathable water between the warm surface and the bottom layer with little oxygen.

However, one potential risk of a longer stratification period for all lakes is its potential to affect both nontoxic and toxic algae blooms later in the fall, said DeGasperi. When the bottom layer of a lake during the summer loses oxygen, that can trigger a release of phosphorus from the sediment. That phosphorus — which can aid algae growth — later becomes mixed into the lake when fall temperatures arrive.

Future challenges for the Ballard Locks

A pinch point exists at the Ballard Locks and broader Ship Canal, which salmon traverse. Before the Locks were built, and the entirety of the water system was replumbed in the 1910s, Lake Washington was 8 feet higher and its annual rise fluctuated with mountain flows.

Now, the level of the lake is carefully engineered by people at the Ballard Locks.

As the lake is expected to warm with climate change, government officials and engineers are exploring plans to cool down the Ship Canal so salmon can still rely on it to migrate during the hottest months of the year.

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For spawning salmon and juveniles migrating to the sea, the only spots with reliably cool and well-oxygenated water are at each end of the 7-mile canal: one in cold Puget Sound, just west of the Ballard Locks where opportunistic seals camp out, and the other in Lake Washington, where the water drops to over 200 feet at its deepest portions and warm-blooded fish like yellow perch and bass have gotten hungrier as the water has warmed.

The sudden change from oxygen-rich saltwater to warm freshwater is a shock for salmon at the Locks, said Lauren Urgenson, a former King County coordinator for the Lake Washington, Sammamish and Cedar watershed. Often adult Chinook salmon looking to spawn will cycle through the fish ladder multiple times or wait upstream for weeks, losing energy and risking attacks from predators, she said.

The salmon get a breath of oxygen-rich cold water each time the Locks open and close to ferry kayakers and boaters through the engineered dam. In the past, engineers experimented with “false lockings,” or opening and closing the Locks even when boats were not around, but found it only increased the oxygen a short distance and not for very long, Urgenson said.

Each time the Locks are operated, the higher freshwater side of the Locks loses water. Drought and decreased river flows due to climate change are expected to affect operations at the Locks, said Kyle Comanor, senior water manager for the Army Corps of Engineers’ Seattle District. The Locks are the only outlet from Lake Washington, and engineers must keep the water level of the lake steady and not let too much saltwater mix inward, he said. To conserve water in the future, wait times for boaters at the Locks may increase or become scheduled, among other management options. 

Meanwhile, adult sockeye salmon have been trucked around the canal and lake to boost their survival. During and after the record-breaking heat wave of 2021, dead salmon were observed in the Locks’ fish ladder. While salmon won’t venture into water warmer than 70 degrees, any water above 59 degrees is considered “sublethal,” stressing the fish and making them susceptible for disease and developmental issues.

To get cold water into the entire length of the Ship Canal, tribes, federal and local government officials and members of Long Live the Kings, a Seattle nonprofit dedicated to salmon recovery, have proposed and are evaluating solutions .

These ideas include various ways of pumping cool water from the depths of Lake Washington directly into the Ship Canal with a series of pipes and valves or using a heat exchanger to cool existing water in the canal.

“If we want salmon here — and salmon have done so much for our region and for us — we need to address this issue,” Urgenson said. “Seattle without salmon is not a great future.”

The opinions expressed in reader comments are those of the author only and do not reflect the opinions of The Seattle Times.

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Cleaning up Lake Washington

Lake Washington was heavily contaminated by untreated sewage until extensive pollution controls by the city of Seattle. 

In the 1950s, an estimated 20 million gallons per day of sewage effluent entered Lake Washington from Seattle and other communities surrounding the Lake. The discovery of the cyanobacteria Oscillatoria rubescens in the lake in 1955, and the implication that phosphorus from sewage effluent was acting as fertilizer for its production, led to predictions by UW Zoology professor W.T. Edmondson and other scientists that nuisance algal conditions and water quality deterioration would worsen in the future. Although the lake was already visibly impaired, it had not yet deteriorated seriously, and the call for public action led to the creation of Metro in 1958. Between 1963 and 1968, over 100 miles of sewer trunk lines and interceptors were laid to carry sewage to treatment plants, and effluent entering the lake was reduced to zero in February, 1968. The $140 million project, considered the costliest pollution control program in the country at that time, was completely locally financed. 

The transparency of Lake Washington waters responded quickly, improving from only 30 inches in 1964 to a depth of 10 feet in 1968. The elimination of the phosphorus load from effluent set off a complex chain reaction of species responses, beginning with the decline of Oscillatoria . The water flea ( Daphnia ) is a filter-feeding crustacean that had been suppressed by Oscillatoria because it clogs the filter apparatus of Daphnia . The decline of Oscillatoria led to an improvement in conditions for Daphnia . Daphnia had also been suppressed by its predator—the possum shrimp ( Neomysis mercedis ). Improvements to spawning habitat in the Cedar River led to increases in long-fin smelt ( Spirinchus thaleichthys ), a predator on Neomysis . The combination of these conditions allowed populations of  Daphnia to increase and the Daphnia preyed on algal species, further improving the lake’s transparency to depths of 17 to 20 feet after 1976. A maximum depth of nearly 25 feet was recorded in 1993. 

The application of scientific information to public action and the successful rescue of Lake Washington from deterioration has been the focus of followup research by natural and social scientists for decades, and is an internationally known example of how such efforts can work.

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Ecological Knowledge and Environmental Problem-Solving: Concepts and Case Studies (1986)

Chapter: 20. control of eutrophication in lake washington.

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Or Control of Eutrophication in Lake Washington Most large cities in the world are situated on coastlines or the shores of rivers or lakes. Freshwaters and estuaries are the initial or eventual recipients of much of the waste products of technological societies. Con- sequently, water pollution is one of the first environmental problems to arise, and it continues to be pervasive even when discharges of wastes are reduced and waste materials are treated in more sophisticated ways. Because limnology is one of the more advanced fields of ecology, the key factors influencing the responses of lakes and rivers are rather well known, and the reasons for those response patterns are often understood. The Lake Washington case study is an example of creative interaction between the scientific community and the political arena in the develop- ment and execution of a plan that resulted in striking and rapid improve- ment of the quality of the waters of this lake, which was being increasingly influenced by growth of the metropolitan Seattle area. 301

Case Study JOHN T. LEHMAN, Division of Biological Sciences, University of Michigan, Ann Arbor Lake Washington at Seattle (47°37' N. 122°14' W) is a moderately deep (65 m), warm, monomictic basin in the drainage of the Cedar River and Sammamish River. The lake discharges into Puget Sound via a system of locks and canals built in 1916. Situated in an expanding metropolitan area, Lake Washington has for years experienced varied and intense de- mands for transportation, recreation, and waste disposal. The condition of the lake has changed greatly over the years in response to changes in nutrient income brought about by the sewerage arrangements. That its water quality today is as good as or better than at any other time in its history is due to a unique blend of scientific judgment and public action. During the expansion of suburban Seattle in the years after World War II, the lake deteriorated in proportion to the pressures applied by a growing populace. Reversing that trend by design, the citizens of the region re- sponded voluntarily to the environmental problem. The solution was costly, but public decision was guided by a firm statement of the problem and a plain alternative. Scientific knowledge helped to define possible future conditions of Lake Washington, and voting citizens selected the course. The story of deterioration and recovery of water quality in Lake Wash- ington on the one hand reflects changes in demographics and politics of a city and its suburbs and on the other hand shows a development and application of scientific thought on a problem that required special qualities of scientific leadership and communication for public education. Action and expenditure of public funds were linked to scientific arguments and to quantitative predictions about conditions of the lake. From a scientific perspective, the actions constituted an experiment and an opportunity to refine hypotheses about how lakes function. From a civil perspective, the case exemplifies transition from parochial, local concerns to a regional outlook in environmental matters. Seattle began discharging raw sewage into Lake Washington at the start of the twentieth century. The large (86.5 km2) and deep basin became the repository of street and septic discharges as the city expanded eastward from Puget Sound. In 1926, however, Seattle created a bond issue for a series of intercepting and trunk sewers to divert sewage from Lake Wash- ington to a treatment plant on the Duwamish River that discharged directly into Puget Sound. By 1941, the last sewer outfall into Lake Washington 302

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 303 from Seattle had been removed. Thereafter, water quality in the lake reflected development not of Seattle, but of its suburbs. Between 1941 and 1953, 10 sewage treatment plants began operating at points around the lake, with a combined daily effluent of 80 million liters. Alternative discharge options were not as readily available to the small municipalities as they had been to Seattle. By 1953, James Ellis, a lawyer whose clients included some of the sewer districts around Lake Washington, sought diversion of sewage from Bellevue, but could not get the cooperation of neighboring districts for the necessary routing. He therefore spoke to the Seattle-King County Municipal League, proposing a system of metropolitan organization that could oversee such regional issues. While these first steps were being discussed in the political arena, scientific investigations of Lake Washington attracted public notice with release of Technical Bulletin 18 of the Washington Pollution Control Commission, An Investigation of Pollution Effects in Lake Washington (1952-1953) (Peterson, 19554. This was the first substantial report of nutrient enrichment of the lake. It cited the work and data of Anderson (1954) and Comita (1953), who had conducted their doctoral studies under the guidance of W. T. Edmondson of the University of Washington. The Seattle Times trumpeted the report with its July 11, 1955, article, "Lake's Play Use Periled by Pollution." The Times returned to the issue a month later, when it reported the complaints of lakeshore residents and spectators at the Gold Cup yacht races (August 11, "Algae Increase Noted in Lake Washington"~. Sanitation authorities doubted that the problems stemmed from the increased entry of effluent into the lake. They blamed sunshine, weather, and water conditions for the changes. It turned out, however, that the conditions of the lake that day triggered a new dimension of scientific curiosity in Edmondson's laboratory. Anderson had returned from the lake with a water sample containing an alga never encountered during his doctoral investigations of the lake: the blue-green alga (cyano- bacterium) Oscillatoria rubescens. To Edmondson, the appearance of Oscillatoria signaled that the lake was deteriorating in classical fashion. The large, deep lakes of Western Europe, particularly Lake Zurich, had been similarly enriched with high- nutrient effluents decades earlier, and water quality had declined. A series of lakes near Madison, Wisconsin, had received treated discharges from that municipality and had deteriorated. Accounts of these cases were in the scientific literature (Hasler, 1947), and Edmondson was struck by the fact that the name Oscillatoria appeared in each account in connection with the earliest stages of decline. For Lake Washington, previous data were available for comparison from 1933 (Scheffer and Robinson, 1939)

304 SELECTED CASE STUDIES and from 1949-1950 (Comita and Anderson, 19591. The doctoral studies of Anderson and Comita and the earlier investigation from 1933 provided a baseline by which to judge changes (Edmondson et al., 19561. The main change in the watershed had been the increased load of nutrients from secondary-treatment waste discharge. Edmondson shared his observations in the October 13, 1955, University of Washington Daily ("Edmondson Announces Pollution May Ruin Lake"), recounting the appearance of Oscillatoria and its likely meaning. He defined his own interest as ob- serving and analyzing the transitional nature of the lake and adding to the research done in Germany and Switzerland. By 1956, the stage was set for developments that would bring civic leaders and scientists together. The scientists took the first step. Ed- mondson and two University of Washington engineering faculty members, R. O. Sylvester and R. H. Bogan, published a popular-science article in the university's journal The Trend in Engineering, "A New Critical Phase of the Lake Washington Pollution Problem" (Sylvester et al., 19561. The article told the history of sewage treatment for the area, described the problems posed by nutrient enrichment, and proposed three procedures for solution: comprehensive regional administration and planning, com- plete elimination of sewage discharge into Lake Washington, and research on the relationships among temperature, nutrients, and algal growth. It provided a concise layman's explanation of nutrient enrichment and its effects, including the appearance of O. rubescens, and it focused partic- ularly on enrichment with the mineral nutrient phosphorus and the diffi- culty of removing it from sewage. The Seattle Times publicized the article with the headline (April 18, 1956), "Lesson of Switzerland Lakes Brought Home to Seattle Area." By October, Edmondson and a new postdoctoral associate, J. Shapiro, had received funds from the National Institutes of Health to study water chemistry and photosynthesis by algae in Lake Washington. In December, Edmondson wrote a letter to James Ellis that marked his first involvement in the public action. James Ellis had been appointed chairman of Seattle's newly established Metropolitan Problems Advisory Committee by Mayor Gordon Clinton, and Edmondson wanted to ensure that Ellis and the committee understood that even well-treated sewage contained enough nutrients to stimulate the growth of plants in the lake. Lake Washington was already showing signs of the same series of changes toward deterioration as had been observed elsewhere. After his initial letter had produced a cordial and positive response from Ellis, Edmondson sent him, on February 13, 1957, a nine-page summary of the effect of drainage and effluent entry into Lake Washington. The letter was phrased as a question-and-answer document and included ref- erences to the professional literature. Edmondson listed answers to 15

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 305 questions that he thought Ellis might be asked in connection with his work on the advisory committee such questions as: How has Lake Washington changed? What will happen if fertilization continues? Why not poison the algae? Edmondson included a rudimentary nutrient budget for the lake constructed from available data, and he developed his case that the mass of algae present varied in strict proportion to the amounts of fertilizing nutrients added to the water. The letter included a mass of limnological cause-and-effect reasoning phrased in jargonless, objective tones. Ellis responded enthusiastically within the week, requesting copies of the letter for distribution to interested groups. The initiative passed back to the political arena for the remainder of 1957. The immediate obstacle was the absence of provisions whereby municipalities could combine some of their government functions in com- prehensive regional matters. Moreover, the notion faced opposition from some, on the grounds that it smacked of "big government." The next step required action at the state level. That aim was met when the Wash- ington state legislature passed a bill permitting the establishment of a metropolitan government ("Metro") with specified functions (Ch. 217, Laws of 19571. The floor manager in the House had been Daniel J. Evans, a first-term representative, former King County engineer, and future gov- ernor. The act permitted the formation of a metropolitan government with any or all of six functions: water supply, sewage and garbage disposal, transportation, comprehensive planning, and park administration. Estab- lishment of a Metro would require passage of a public referendum. The first effort to win public acceptance for spending money to clean up the lake occurred in March 1958, when a proposal to establish a Metro charged with sewage disposal, transportation, and comprehensive planning was placed on the ballot. The proposal won 54.4% of the vote, but was defeated through a complicated system of weighting votes separately in Seattle and the rest of King County. Many people outside Seattle believed that the plan was an effort to tax them for the expenses of the city. Ellis and his committee revised the scope of their plan, targeting only water pollution control and reflecting the urgency posed by the deteriorating state of Lake Washington. A revised proposal, with the single function of sewage disposal, was approved on September 9, 1958, winning 58% of the vote in Seattle and 67% in the rest of the county. Lake Washington obviously had become a focus of regional concern among the numerous communities that populated its shores. The water and beaches served for recreation, and the lake itself was deemed of aesthetic value. A genuine sense of pride and responsibility is evident in the political arguments that surrounded the issue. Citizens were asked to undertake, at the expense of about $2 per month for each household served,

306 SELECTED CASE STUDIES a public project of sewage diversion that was at the time the most costly pollution control effort in the nation. The plan called for construction of a massive trunk sewer to divert all effluent from around the lake, to treat it, and to discharge it at great depth in Puget Sound. Tidal flushing guaranteed that objectionable quantities of nutrients would not accumulate in the estuary. Edmondson played no part in the partisan politics, but his scientific knowledge and judgment were a deciding asset in the Metro campaign. By supplying facts and generally making himself available to answer questions from the mass media or private citizens, he provided the au- thority that backed the movement with facts and logic. Ellis praised Ed- mondson's stand years afterward for providing the facts needed to quiet the critics. When he spoke, Ellis reported, "he made us feel that the Lord God was standing right behind us on this one" (Chasan, 1971, p. 111. Privately and professionally, Edmondson reported the Lake Washington case as an experiment in lake fertilization. His scientific publications during this period traced the departure of chemical and biological con- ditions from the historical conditions and attempted to discern the general quantitative relationships between nutrient additions and primary produc- tivity in lakes. Edmondson had been able to predict in his letter to Ellis of February 1957 a serious and rapid decline in water quality. He wrote: "Within a few years we can expect to have serious scum and odor nuisances.... Judging by the speed with which the process has gone in other lakes, I would expect distinct trouble here within five years, although isolated occurrences might come earlier." The important elements of his predic- tions that gave heart to the proponents of the diversion plan were that Edmondson thought that the lake had not yet been irreversibly damaged and that diversion would lead to a decrease in the abundance of blue- green algae. These were the plants that clouded the fertilized water, rafted to shore, and decomposed or otherwise fouled the lake. His predictions were based on fundamental principles of mass balance, stoichiometry, and an opinion that, to a large degree, changes in lake conditions are reversible when factors forcing the changes are reversed. The specific basis for quantitative predictions was a conceptual and graphic model that related changes in lake properties from known initial conditions to changes in nutrients (Edmondson, 19791. The model assumed a limited return of nutrients from sediment deposits on the basis of chemical conditions in the lake and work done decades earlier in Germany and England (Mortimer, 1941, 1942; Ohle, 19341. Finally, it required knowl- edge of the lake's water budget, to permit calculation of a rate of dilution. From these basic facts and hypotheses, it was possible to project not only

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 307 the speed of deterioration, but also the rate of recovery with different diversion schemes. Years later, the same ideas were used by other lim- nologists to construct mathematical models of lake conditions in response to nutrient income and hydrology (Piontelli and Tonolli, 1964; Vollen- weider, 1969, 1975, 19761; and the principles remain guiding tenets of modern lake management (Chapra and Reckhow, 1983; Reckhow, 19791. From a strictly scientific viewpoint, the exercise encouraged thought about nutrient budgets and helped to integrate studies of lakes with their wa- tersheds. Equally important, the scientific studies helped to elaborate the quantitative links between nutrients and productivity. Many limnologists of the early twentieth century had been trained in the shadow of Forbes's (1925) philosophical essay "The Lake as a Microcosm" and had confined their investigations within lakeshore boundaries. Forbes himself took a much broader view of lakes and their watersheds than the title suggests, but most limnologists at the time began and ended their studies at the shoreline. Edmondson, however, had visited Wisconsin as a graduate student while C. N. Sawyer was laboring to construct the first budgets of fertilization for the lakes at Madison (Sawyer, 19471. The perspective he gained was holistic and comprehensive. The new view might better be termed "the lake in an ecosystem." Groundbreaking ceremonies for the new project were held in July 1961. Meanwhile, the lake deteriorated according to predictions. On July 3, 1962, the Seattle Post-lntelligencer reported "Lake Washington Brown- That's Algae, Not Mud and It'll Be There For the Next 10 Years." Visibility in lake water had declined from 4 m in 1950 to less than l m by 1962. The first diversions were slated for the next year, and, on the basis of the timetable for later diversions, Edmondson estimated that the lake would revert to its condition of 1949 by about 5 years after completion of the project. By October 5, 1963, the Post-Intelligencer had dubbed Lake Washington "Lake Stinko," with nuisance conditions at their peak just before effluent diversion. The rest of the public record is a series of congratulatory editorials and progress reports in city and suburban newspapers. One by one, waste treatment plants around the lake had their effluent diverted. The first diversion was in 1963, and the last was in 1968. The trend of deterioration stopped in 1964; conditions that summer were no worse than in 1963. By 1965, it was apparent that water transparency, algal abundance, and phos- phate concentrations were improving. On November 19, 1965, Edmond- son predicted in his address to Sigma Xi, the scientific research society, that the lake would return to its pre-19SOs condition within 6 years and that it would be possible to see the bottom as deep as 6 m. In the previous summer, he had made the same prediction to K. Wuhrmann, a skeptical

308 SELECTED CASE STUDIES colleague from Zurich. At meetings of the International Association for Theoretical and Applied Limnology, Wuhrmann had argued that sediment release of phosphorus would extend the recovery for decades. The sci- entists disagreed about one of the principal hypotheses that Edmondson had used for his quantitative predictions. Phosphorus arrives at the sediments in the form of detrital material that decomposes more slowly than it becomes buried. Thus, the water only a few millimeters below the surface would contain great reservoirs of phos- phate ions that owed their presence to the rich conditions of eutrophication. If the ions diffused through porous and unconsolidated sediment back into the water, they could renew productivity from that "internal" source. Edmondson reasoned that the oxidation-reduction potential of surficial sediments guaranteed that iron would exist in its ferric (+3) oxidized form. In that state, it could form insoluble ferric-hydroxyl-phosphates of indeterminate stoichiometry, and the sediments would become an "iron trap" for the phosphorus. This was what Mortimer had shown in micro- cosm experiments with mud from the English Lake District. Rates of decomposition in Lake Washington were not high enough to exhaust the oxygen content of the deep water during stratification each summer. As long as the large hypolimnion remained oxic, redox potentials would favor ferric iron, and the "iron trap" could halt the upward diffusive flux of phosphate. Wuhrmann doubted that principles governing ion speciation and fluxes inside model tanks could be freely extrapolated to whole lakes. Their friendly wager that summer and Wuhrmann's delivery of one bottle of Scotch during the 1971 congress in Leningrad highlight the intellectual excitement and new understanding that the Lake Washington experiment afforded to professional limnologists. Edmondson's professional publications during the period reported the progress of physical, chemical, and biological changes in the lake (Ed- mondson, 1961, 1966, 1968, 1969a,b, 1970, 1972a,b). Transparency and algal abundance responded very quickly to the nutrient diversions. Species composition proved somewhat more intransigent. Even though biomass was reduced, Oscillatoria persisted into the early 1970s, making occa- sional appearances each summer. Finally, it too was gone. Trophic equi- librium in response to altered nutrient loading was complete in 1975 (Edmondson, 1977a,b; Edmondson and Lehman, 19811. Concentrations of phosphorus were reduced nearly to equilibrium and were similar from year to year. Chlorophyll concentrations and algal biomass were dramat- ically reduced, in parallel with the nutrient changes. Transparency had increased, and all filamentous blue-green algae, including Oscillatoria, had been eliminated. The experiment was complete, and the scientific community had learned

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 309 new lessons about dynamic processes in lakes. The general public enjoyed its own measure of international praise, as witness articles in Harpers (Clark, 1967), Smithsonian (Chasan, 1971), and Audubon (Kenworthy, 19711. Metro became one of the few noncities to win an "All-American City" award. The public record ends here, but new sources of scientific curiosity grew from continuing investigations. After the few years of constancy, water transparency suddenly increased to a point never before recorded in the lake. Visibility was 12 m at times. Accompanying the change was a further, drastic reduction in algal abundance. This time, there had been little or no change in watershed relations; the limnological conditions were changing despite relatively constant nutrient loading. What had changed were the herbivores (Edmondson and Litt, 19821. Throughout the doctoral studies of Comita and throughout the episode of enrichment and diversion, Lake Washington had been dominated by co- pepods, a group of microscopic crustacean plankton. The changing nutrient supply to the lake exerted controls on the biota from the base of the food chain, because nutrients are essential for plant growth. By the late 1970s, however, Lake Washington was at times dominated by cladocerans, par- ticularly by members of the genus Daphnia. Controls on algal abundance had shifted to much higher in the food chain. The cladocerans are able to reproduce faster than the copepods, and their success reduced the algae by sheer numbers and grazing pressure. Why had the zooplankton community changed? Daphnia had not dom- inated the lake even in 1933. Did it have anything to do with changes set in motion by the enrichment episode? The answers to this new puzzle are being debated now, because similar shifts have been recorded in Lake Tahoe, in Lake Michigan, and in ponds of central Europe. It is known that the answer lies in deciphering the balance of forces that affect birth and death rates among the potentially dominant populations. The success of predatory invertebrates and planktivorous fish is involved in present hypotheses. Edmondson and Litt (1982) proposed that the changes might be traced to the decline of an important predator on Daphnia. Selective predation is known to be a major force in determining species composition in zooplankton communities (Hrbacek, 1962; Hrbacek et al., 19611. Neo- mysis mercedis, which was very abundant during the l950s and early 1960s, suddenly declined in the mid-1960s with the rise of the longfin smelt Spirinchus thaleichthys. Neomysis strongly selects Daphnia over other planktonic crustaceans (Murtaugh, 1981), and Spirinchus feeds largely on Neomysis (Eggers et al., 19781. Released from this predation, Daphnia nonetheless took 10 years to dominate the lake plankton. Delays inherent in life histories or colonization times were insufficient to explain the gap.

310 SELECTED CASE STUDIES The reason for the delay seems to have been the continued presence of Oscillatoria. Long individual trichomes of O. rubescens and a few other filamentous species clog the feeding mechanism of Daphnia and force the animal to eject entire boll of food and to engage in elaborate grooming behavior (Infante and Abella, 1985~. Copepods like Diaptomus do not seem to exhibit similar evidence of interference and can thrive in the presence of the trichomes, possibly because of hydromechanical differ- ences in food capture. Thus, it was not until manipulations of the nutrient base excluded Oscillatoria from the lake that Daphnia could assert its dominance among the zooplankton. Changes at many trophic levels are thus relevant to the scientific side of the case study of Lake Washington. They illustrate the ease with which the solving of environmental "problems" can blend with ecological in- vestigation. Retrospective analyses of the public record make a good lesson in civics, but thoughtful progress in science is cheated if investigations do not uncover new challenges and point to new paths of inquiry, as does the study of Lake Washington and its biological community. REFERENCES Algae increase noted in Lake Washington. Seattle Times. August 11, 1955. Anderson, G. C. 1954. A Limnological Study of the Seasonal Variation of Phytoplankton Populations. Ph.D. thesis, University of Washington, Seattle. Chapra, S. C., and K. H. Reckhow. 1983. Engineering Approaches for Lake Management. Vol. 2. Mechanistic Modeling. Ann Arbor Sciences, Ann Arbor, Mich. Chasan, D. J. 1971. The Seattle area wouldn't allow the death of its lake. Smithsonian 2(4):6-13. Clark, E. 1967. How Seattle is beating water pollution: Metro's project. Harpers 234:91- 95 (June). Comita, G. W. 1953. A Limnological Study of Planktonic Copepod Populations. Ph.D. thesis, University of Washington, Seattle. Comita, G. W., and G. C. Anderson. 1959. The seasonal development of a population of Diaptomus ashlandi Marsh, and related phytoplankton cycles in Lake Washington. Lim- nol. Oceanogr. 4:37-52. Edmondson announces pollution may ruin lake. University of Washington Daily. October 13, 1955. Edmondson, W. T. 1961. Changes in Lake Washington following an increase in the nutrient income. Verh. Int. Verein. Limnol. 14:167-175. Edmondson, W. T. 1966. Changes in the oxygen deficit of Lake Washington. Verh. Int. Verein. Limnol. 16: 153-158. Edmondson, W. T. 1968. Water-quality management and lake eutrophication: The Lake Washington case. Pp. 139-178 in T. H. Campbell and R. O. Sylvester, eds. Water Resources Management and Public Policy. University of Washington Press, Seattle. Edmondson, W. T. 1969a. Cultural eutrophication with special reference to Lake Wash- ington. Mitt. Int. Verein. Limnol. 17:19-32.

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 311 Edmondson, W. T. 1969b. Eutrophication in North America. Pp. 124-149 in Eutrophication: Causes, Consequences, Correctives. Proceedings of a Symposium. National Academy of Sciences, Washington, D.C. Edmondson, W. T. 1970. Phosphorus, nitrogen and algae in Lake Washington after di- version of sewage. Science 169:690-691. Edmondson, W. T. 1972a. The present condition of Lake Washington. Verh. Int. Verein. Limnol. 18:284-291. Edmondson, W. T. 1972b. Nutrients and phytoplankton in Lake Washington. Am. Soc. Limnol. Oceanogr. Spec. Symp. 1:172-193. Edmondson, W. T. 1977a. Recovery of Lake Washington from eutrophication. Pp. 102- 109 in J. Cairns, Jr., K. L. Dickson, and E. E. Herricks, eds. Recovery and Restoration of Damaged Ecosystems. University Press of Virginia, Charlottesville. Edmondson, W. T. 1977b. Trophic Equilibrium of Lake Washington. EPA-600/3-77-087. Environmental Research Laboratory, U.S. Environmental Protection Agency, Corvallis, Oreg. Edmondson, W. T. 1979. Lake Washington and the predictability of limnological events. Arch. Hydrobiol. Beih. 13:234-241. Edmondson, W. T., and J. T. Lehman. 1981. The effect of changes in the nutrient income on the condition of Lake Washington. Limnol. Oceanogr. 26:1-29. Edmondson, W. T., and A. H. Litt. 1982. Daphnia in Lake Washington. Limnol. Oceanogr. 27:272-293. Edmondson, W. T., G. C. Anderson, and D. R. Peterson. 1956. Artificial eutrophication of Lake Washington. Limnol. Oceanogr. 1:47-53. Eggers, D. M., et al. 1978. The Lake Washington ecosystem: The perspective from the fish community production and forage base. J. Fish. Res. Bd. Can. 35:1553-1571. Forbes, S. A. 1925. The lake as a microcosm. [Reprinted.] Bull. Ill. Nat. Hist. Surv. 15:537-550. Hasler, A. D. 1947. Eutrophication of lakes by domestic drainage. Ecology 28:383-395. Hrbacek, I. 1962. Species composition and the amount of the zooplankton in relation to the fish stock. Rozpr. Cesk. Akad. Ved. Rada Mat. Prir. Ved. 10:1-116. Hrbacek, J., M. Dvorakova, M. Korinek, and L. Prochazkova. 1961. Demonstration of the effect of fish stock on the species composition of zooplankton and the intensity of metabolism of the whole plankton association. Verh. Int. Verein. Limnol. 14:192-195. Infante, A., and S. E. B. Abella. 1985. Inhibition of Daphnia by Oscillatoria in Lake Washington. Limnol. Oceanogr. 30:1046-1052. Kenworthy, E. W. 1971. How Seattle cleaned up. Audubon 73:105-106. Lake's play use periled by pollution. Seattle Times. July 11, 1955. Lake Stinko. Seattle Post-Intelligencer. October 5, 1963. Lake Washington brown That's algae, not mud.... Seattle Post-Intelligencer. July 3, 1962. Lesson of Switzerland lakes brought home to Seattle area. Seattle Times. April 18, 1956. Metro area citizens should be proud of achievement. Seattle Times. September 19, 1965. Mortimer, C. H. 1941. The exchange of dissolved substances between mud and water in lakes. Parts l and 2. J. Ecol. 29:280-329.  Mortimer, C. H. 1942. The exchange of dissolved substances between mud and water in lakes. Parts 3 and 4. J. Ecol. 30:147-201. Murtaugh, P. A. 1981. Selective predation by Neomysis mercedis in Lake Washington. Limnol. Oceanogr. 26:445-453. Ohle, W. 1934. Chemische und physikalische Untersuchungen norddeutscher Seen. Arch. Hydrobiol. 26:386-464, 584-658.

312 SELECTED CASE STUDIES Peterson, D. R. 1955. An Investigation of Pollution Effects in Lake Washington (1952- 1953). Washington Pollution Control Commission Tech. Bull. 18, Seattle, Wash. Piontelli, R., and V. Tonolli. 1964. Residence time of lake water in relation to enrichment, with special reference to Lago Maggiore. Mem. Ist. Ital. Idrobiol. 17:247-266. [in Italian] Reckhow, K. H. 1979. Empirical lake models for phosphorus: Development, applications, limitations and uncertainty. Pp. 193-221 in D. Scavia and A. Robertson, eds. Perspectives on Lake Ecosystem Modeling. Ann Arbor Sciences, Ann Arbor, Mich. Sawyer, C. N. 1947. Fertilization of lakes by agricultural and urban drainage. J. N. Engl. Water Works Assoc . 61: 109- 127. Scheffer, V. B., and R. J. Robinson. 1939. A limnological study of Lake Washington. Ecol. Monogr. 9:95-143. Sylvester, R. O., W. T. Edmondson, and R. H. Bogan. 1956. A new critical phase of the Lake Washington pollution problem. Trend in Engineering 8(2):8-14. Vollenweider, R. A. 1969. Moglichkeiten und Grenzen elementarer Modelle der Stoffbilanz von Seen. Arch. Hydrobiol. 66:1-36. Vollenweider, R. A. 1975. Input-output models with special reference to the phosphorus loading concept in limnology. Schweiz. Z. Hydrol. 37:53-84. Vollenweider, R. A. 1976. Advances for defining critical loading levels for phosphorus in lake eutrophication. Mem. Ist. Ital. Idrobiol. 33:53-83. Committee Comment Several features of environmental problem-solving are illustrated by the Lake Washington example. The project itself was regarded as an exper- iment, and scientists were able to test their hypotheses during the study. Analogs existed in the scientific literature, so investigators were able to reason partly from first principles and partly by reference to other ex- amples. At one point, Edmondson read through an article by A. D. Hasler (1947) that reviewed the history of cultural eutrophication in Europe and North America. He underlined "Oscillatoria" each time the word ap- peared in the text and discovered that the organism was a nearly ubiquitous indicator of eutrophication. Similarly, the relationship between Neomysis and Daphnia was suggested in part by experiences in Lake Tahoe when Mysis relicta was introduced as a forage food for fish (Richards et al., 1975). To understand the course of events in Lake Washington, one must draw on most of the sources of knowledge identified here. The initial events were treated as an experiment in lake fertilization that could improve our understanding of the ways that nutrient inputs control the biological char- acter of lakes. Changes in the plankton community after the enrichment experiment required analyses of biological events at the population and community levels. Plankton community structure was seen to be governed by a variety of species interactions, including predation and interference. Superficially, the lake appeared to exhibit alternative stable states with

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 313 regard to plankton composition. In fact, the transition from one state to another was a logical consequence of changing fields of predators and algae. Most important, the scientists were able to identify a few factors and processes that were acting with special force among the myriad present. Edmondson and Litt (1982) wrote: "We assume that the processes con- trolling the population are simultaneously affected by many factors and that changing any one can affect the population. At some times, one factor may dominate the others quantitatively." Scientific judgment was needed to identify the stoichiometries and relations among nutrient income, hy- drology, and algal production. Similar reasoning helped to establish the likely causes for species alterations. No amount of descriptive field study alone would establish causality firmly enough to permit quantitative man- agement decisions. Judgments had to be made about how algal production would respond to alterations in nutrient supplies and about the importance of nutrient returns from the sediments. That required knowledge of more than the biota alone. It was necessary to regard the organisms as being integrated with their physical and chemical surroundings. Spatial relations and the vertical differentiation that arises from thermal stratification were important, too. Lake Washington is a warm, mono- mictic lake; therefore, it circulates all winter long. Winter is also the time of greatest fluvial discharge, and on the average one-third of the lake's volume is renewed each year. Most of the water drains from the Cascade Range and is very low in dissolved salts or nutrients of any kind. Each winter, the lake is thus diluted by water of low nutrient content. Ed- mondson could argue securely that, if fertilizing discharges from munic- ipalities ceased, the accumulated nutrients and algal biomass could be flushed from the basin within a few years. Because Lake Washington possessed a large hypolimnion with more than adequate reserves of oxygen to last through summer stratification, most of the phosphorus locked in the sediments would stay there. Furthermore, in the case of Lake Washington, scientific judgment backed by logic and data was separated from emotional statements. The decision to raise public funds and divert the effluent was political, not scientific; indeed, sound and important discoveries probably would have accom- panied a study of continued deterioration of the lake. The case of Lake Washington is exemplary, not because the forecasts were so accurate, but because events were documented and reported in comprehensible fashion. The documents reveal a remarkable synergism of scientific and public awareness about an environmental issue. The retrospective account makes the scientific issues sound perhaps more cut and dried than they were at the time. It might seem that the only suspense

314 SELECTED CASE STUDIES was related to the public's willingness to spend money to improve water quality. In the 1960s, however, debates about the causes of lake eutrophication were common, and the debates eventually spawned an inquiry by the National Research Council (19691. The Research Council's report directed attention to phosphorus, but the evidence came in part from results seen in Lake Washington. Vocal scientific lobbies had argued that carbon and nitrogen could be limiting elements in many aquatic habitats and that phosphorus control would therefore be insufficient to halt eutrophication. Many of the conflicting opinions were published in the proceedings of a special symposium of the American Society of Limnology and Ocean- ography (Likens, 19721. It was in the early stages of this debate that the Lake Washington experiment was conceived and executed. Despite the obvious success in curbing pollution of the lake, the ex- periment could not by itself prove that phosphorus was the culprit, even though predictions had been based on that assumption. The action of removing waste treatment effluent from a lake lacks the rigor of a con- ventional laboratory experiment, in that many factors are manipulated simultaneously. Opponents could argue that improvement arose because some unmeasured trace metal or unknown growth factor was removed with the effluent and that phosphorus control elsewhere might be costly and irrelevant. Indeed, many investigators had discovered that, when lake phytoplankton was enclosed in bottles and subjected to single-nutrient additions, carbon, nitrogen, or trace metals could often stimulate their metabolism and growth (Likens, 19724. This very type of observation is the basis of present views about nitrogen limitation in the oceans (Ryther and Dunstan, 1971~. The principal difference between bottle bioassays and Lake Washington, however, lies not in methodological detail, but in the scale of the manip- ulation. In the case of Lake Washington, an entire ecosystem was ma- nipulated. At lake-wide scales, exchange processes at air-water and sediment- water interfaces become important, and responses can be followed over long periods. Lake Washington became one of the pioneer "whole-lake" experiments. Within a few years, Canadian limnologists had established an Experimental Lakes Area in northwestern Ontario (Johnson and Val- lentyne, 1971) and were setting out to test nutrient controls of eutrophi- cation more rigorously than could ever be possible in Lake Washington. Experimental lakes were purposely fertilized with nitrogen, phosphorus, and carbon, singly and in combinations. The results showed beyond doubt that phosphorus was the master controlling nutrient, as far as eutrophi- cation was concerned (Schindler, 19771. When lakes were fertilized with

CONTROL OF EUTROPHICATION IN LAKE WASHINGTON 315 phosphate alone, algal growth reached bloom proportions, because inor- ganic carbon entered the lake water from the atmosphere and continuously replaced the carbon used by the algae during photosynthesis. Similarly, species composition in these lakes became more strongly represented by nitrogen-fixing blue-green algae (cyanobacteria), which formed the ulti- mate reservoir for the nutrient. Phosphorus, however, has no gaseous atmospheric phase, so its rate of supply to a lake basin sets an absolute limit on standing crops. With only bottle bioassays or small-scale exper- iments of short duration, the ultimate consequences of a manipulation could not be forecast. Bottles are closed to gas exchange with the at- mosphere, and the experiments are too brief to permit species assemblages to change. In short, no study short of a whole-lake manipulation could have provided an adequate analogy to this experiment. That is why the lessons from Lake Zurich and the lakes in Madison, Wisconsin, were so valuable in the early, predictive stages of the project. As a historical footnote, the success story of Lake Washington might have heartened those in Switzerland who were trying to clean up Lake Zurich. Cultural eutrophication in Lake Zurich had been accelerating since 1896 (Thomas, 19694. Three-stage waste treatment plants around the lake with chemical precipitation processes for the removal of the phosphate were introduced. The first started operating in 1967; since then, all Zurich treatment plants have had precipitation installations to eliminate phosphate (Dietlicher, 1974~. The improvements coincided with reductions in phos- phate concentrations in the lake and improvements in water quality. References Dietlicher, K. 1974. The Water Quality of the Lakes of Zurich and "Walensee." Zurich Waterworks, Zurich, Switz. Edmondson, W. T., and A. H. Litt. 1982. Daphnia in Lake Washington. Limnol. Oceanogr. 27:272-293. Hasler, A. D. 1947. Eutrophication of lakes by domestic drainage. Ecology 28:383-395. Johnson, W. E., and J. R. Vallentyne. 1971. Rationale, background, and development of experimental lake studies in northwestern Ontario. J. Fish Res. Bd. Can. 28:123-128. Likens, G. E., ed. 1972. Nutrients and eutrophication: The limiting nutrients controversy. Am. Soc. Limnol. Oceanogr. Spec. Symp. 1:1-328. National Research Council. 1969. Eutrophication: Causes, Consequences, Correctives. Proceedings of a Symposium. National Academy of Sciences, Washington, D.C. Richards, R. C., C. R. Goldman, T. C. Frantz, and R. Wickwire. 1975. Where have all the Daphnia gone? The decline of a major cladoceran in Lake Tahoe, California-Nevada. Verb. Int. Verein. Limnol. 19:835-842.

316 SELECTED CASE STUDIES Ryther, J. H., and W. M. Dunstan. 1971. Nitrogen, phosphorus, and eutrophication in the coastal marine environment. Science 171:1008-1013. Schindler, D. W. 1977. Evolution of phosphorus limitation in lakes. Science 195:260-262. Thomas, E. A. 1969. Kulturbeeinflusste chemische und biologische Veranderungen des Zurichsees im Verlaufe von 70 Jahren. Mitt. Int. Verein. Limnol. 17:226-239.

This volume explores how the scientific tools of ecology can be used more effectively in dealing with a variety of complex environmental problems. Part I discusses the usefulness of such ecological knowledge as population dynamics and interactions, community ecology, life histories, and the impact of various materials and energy sources on the environment. Part II contains 13 original and instructive case studies pertaining to the biological side of environmental problems, which Nature described as "carefully chosen and extremely interesting."

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How Lake Washington got cleaned up at the expense of area tribes

If you find yourself at Lake Washington this summer, breathe deeply.

Matthew Klingle, author of "Emerald City: An Environmental History of Seattle," says you wouldn't have wanted to do that 60 years ago, when the lake was chronically polluted with sewage.

He told Ann Dornfeld from KUOW's Race and Equity Team how Lake Washington got cleaned up — at the expense of a river sacred to local tribes.

Klingle: It was commonly called "Lake Stinko" at the time. From a distance, Lake Washington wouldn't appear that different if, say, you were flying over in an early Boeing aircraft. But if you were to step on the shores of Lake Washington in, say, 1956, 1957, particularly during the summer months when the algae growth was at its highest, you would see a something not unlike a stinking, fetid backyard pool choked with algae and smelling in the sun.

Related: How the plane that won WWII polluted the Duwamish River

Dornfeld: After a sewer system was created throughout the city of Seattle and the region, that sewage got dumped into places like the Duwamish River. What effect did that have on that river?

Klingle: Well the thing to keep in mind about the transference of the sewage to the Duwamish is that the immediate and proximate problem that Seattle and King County faced — with the ire of suburban residents living around the lake, the concern of scientists, the worries of public officials — was how you were going to revive a lake that was the centerpiece of the burgeoning suburban communities surrounding it. So, not surprisingly, the engineers, the planners of [the sewer system] found the easiest way to remove the sewage was to follow the old original watershed: Lake Washington used to drain into the Duwamish before the dredging of the Ship Canal.

So one of the challenges is that you're moving the sewage from the now connected home sewer systems — the residential waste — but you're also carrying with it the industrial waste. The Washington Pollution Control Commission throughout the 1950s and 1960s was very much concerned about the mounting pollution burden in the Duwamish River. But the engineering solutions at the time as such made the Duwamish, in some ways, the natural place to put that sewage.

Related: Photos of pollution in Duwamish River

Dornfeld: That's despite the fact that you had a lot of Native Americans and immigrants who relied on fishing in the Duwamish for their own dinner tables, if not for commercial reasons at that time.

Klingle: And from the very beginning of European-American resettlement and contact, these waterways, these shorelines all become, in a sense, contested battlegrounds over who gets to determine who controls the resources. Who gets to determine where people live and how to use the environment in particular ways. It also coincides at the very moment when Native peoples were beginning to fight for their rights as enumerated in the treaties of the 1850s to fish in the usual and accustomed places: To be entitled to one-half of the catch, as the original treaty said.

And so it was this convergence of addressing a very real environmental problem in the pollution of Lake Washington, building a regional sewer system, and thinking on a regional level about how to combat an environmental problem like pollution, coming into confluence, if you will, with rising Native concern over sovereignty and self-determination, wanting to exercise their treaty rights and wanting to fight for the right to capture those fish. It made for, among many other places throughout Puget Sound, dramatic conflict that eventually yielded the 1974 U.S. v. Washington, commonly known as the Boldt Decision, that effectively upheld the treaties and began to establish the federally-recognized Native peoples around Washington state as co-managers of the region's fisheries.

This transcript has been lightly edited for clarity.

Ann is a reporter on KUOW's Investigations Team. Previously, she covered education stories for KUOW for a decade, with a focus on investigations into racial and socioeconomic inequities.

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Revisiting the Lake Washington sediment record: what sediment coring studies can tell us about long-term water quality trends

By Curtis DeGasperi, King County Water and Land Resources Division and Will Hobbs, Washington State Department of Ecology

We monitor water quality over time to identify trends and relate them to changes due to human activity. However, water quality monitoring data often don’t go back far enough in time because monitoring doesn’t typically begin before potential human impacts are identified. Furthermore, trends caused by natural variability in these relatively short records can be mistaken for human-caused trends. Lake sediments provide a layered history that integrates the changes in inputs from the water and airsheds that can be consulted at any time using a consistent set of methods [For example, see this June 2022 WATERLINE article ]. We conducted a sediment coring pilot study in Lake Washington to assess the potential utility of this approach in evaluating water quality trends and detecting human-caused changes.

Fig. 1. Location in Lake Washington where the sediment core was collected in 2020 (credit: Google Earth).

Lake Washington, located between Seattle and Bellevue, is the second-largest natural lake in the State of Washington. It is also perhaps one of the most famous case studies of lake eutrophication and subsequent recovery following the diversion of treated wastewater inputs in the 1960s. The lake has been the subject of numerous sediment coring studies focused on the lake’s response to eutrophication and contaminant inputs.

We collected a sediment core from Lake Washington in 2020 (Figure 1). We collected the sediment from 1-cm sections of the core from the surface (0-1 cm) to the bottom of the core (39-40 cm), which represented present conditions (surface sediment) to conditions prior to significant forest clearing and human development of the lake basin (<1860) (Figure 2). The questions we wanted to answer were:  

Fig. 2. Photo of 40-cm sediment core collected from Lake Washington in 2020 and the approximate age of the sediment.

What can the collection and analysis of an age-dated sediment core from Lake Washington tell us about long-term trends in nutrients, algae (including blue-green algae or cyanobacteria), and cyanotoxins?

What can the collection and analysis of an age-dated sediment core from Lake Washington tell us about long-term trends and recovery rates due to historical trace metal and synthetic organic inputs?

To answer these questions we measured sediment phosphorus, nitrogen, organic carbon, stable isotopes of carbon and nitrogen, cyanotoxins (microcystins), and fossil algae and cyanobacteria pigments. We also measured metals (aluminum, arsenic, cadmium, chromium, copper, iron, lead, nickel, manganese, mercury, and zinc) and polychlorinated biphenyls (PCBs).  

Because there has been a long history of similar studies of Lake Washington sediments, we could compare our results to those reported in earlier studies. In general, the results were very similar across studies, indicating the reproducibility and reliability of these methods for tracking water quality trends. Overall, this pilot study demonstrated the utility of collecting and analyzing a core using consistent methods. The result was a time series of relevant environmental variables spanning more than 150 years.

Some significant findings included:

Eutrophication

• Sediment phosphorus and fossil pigments tracked the observed water quality response of Lake Washington to the period of eutrophication and subsequent secondary wastewater diversion completed in 1968 (Figure 3).
• We observed relatively low algal toxin production levels with a relatively small but measurable increase in toxin production during the eutrophication period.

Fig. 3. Panel A shows the observed Lake Washington summer average (June-September) lake surface water total phosphorus concentrations (µg/L) through 2021 [University of Washington data courtesy of Daniel Schindler]. Panel B shows the algae and cyanobacteria (blue-green algae) pigment concentrations in the dated sediment core collected in 2020. The vertical dashed lines represent the breaks between zones determined by hierarchical cluster and broken stick analysis of the sediment pigment data – the area between them shows the period of peak wastewater input and recovery.

• Cadmium, chromium, lead, mercury, and nickel inputs peaked near the middle to the early second half of the 20th century. Inputs of these metals have steadily decreased since their respective peaks.
• Copper and zinc inputs increased through the 20th century until about 1950. Copper inputs appear to have remained steady and zinc inputs have continued to increase since 1950.
• There was a distinct peak in sediment arsenic levels dated to the 1950s. However, there was a secondary arsenic peak in recently deposited surface sediments (0-2cm) that was also observed in the surface sediments of earlier cores from Lake Washington
• We observed a rapid increase in sediment PCB concentrations until the 1970s that closely coincided with U.S. PCB production and environmental releases beginning in the 1940s. The sediment concentrations decreased rapidly after the phase-out of U.S. PCB production and its final ban in the 1970s.

A more comprehensive discussion of this work can be found in a recent King County report called Lake Washington 2020 Sediment Coring Study .  

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Peer-reviewed

Research Article

Shifting Regimes and Changing Interactions in the Lake Washington, U.S.A., Plankton Community from 1962–1994

* E-mail: [email protected]

Affiliation University of Washington Tacoma, Puget Sound Institute, Tacoma, Washington, United States of America

Current address: Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America

Affiliations National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, Santa Barbara, California, United States of America, The Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada

Affiliation Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America

Current address: School of the Environment, Washington State University, Pullman, Washington, United States of America

Affiliation Channel Islands National Marine Sanctuary, National Ocean Service, National Oceanic and Atmospheric Administration, Santa Barbara, California, United States of America

Affiliation Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America

Current address: Center for Environmental Research, Education and Outreach, Washington State University, Pullman, Washington, United States of America

Affiliation National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, Santa Barbara, California, United States of America

• Tessa B. Francis, 
• Elizabeth M. Wolkovich, 
• Mark D. Scheuerell, 
• Stephen L. Katz, 
• Elizabeth E. Holmes, 
• Stephanie E. Hampton

• Published: October 22, 2014
• https://doi.org/10.1371/journal.pone.0110363
• Reader Comments

Understanding how changing climate, nutrient regimes, and invasive species shift food web structure is critically important in ecology. Most analytical approaches, however, assume static species interactions and environmental effects across time. Therefore, we applied multivariate autoregressive (MAR) models in a moving window context to test for shifting plankton community interactions and effects of environmental variables on plankton abundance in Lake Washington, U.S.A. from 1962–1994, following reduced nutrient loading in the 1960s and the rise of Daphnia in the 1970s. The moving-window MAR (mwMAR) approach showed shifts in the strengths of interactions between Daphnia , a dominant grazer, and other plankton taxa between a high nutrient, Oscillatoria -dominated regime and a low nutrient, Daphnia -dominated regime. The approach also highlighted the inhibiting influence of the cyanobacterium Oscillatoria on other plankton taxa in the community. Overall community stability was lowest during the period of elevated nutrient loading and Oscillatoria dominance. Despite recent warming of the lake, we found no evidence that anomalous temperatures impacted plankton abundance. Our results suggest mwMAR modeling is a useful approach that can be applied across diverse ecosystems, when questions involve shifting relationships within food webs, and among species and abiotic drivers.

Citation: Francis TB, Wolkovich EM, Scheuerell MD, Katz SL, Holmes EE, Hampton SE (2014) Shifting Regimes and Changing Interactions in the Lake Washington, U.S.A., Plankton Community from 1962–1994. PLoS ONE 9(10): e110363. https://doi.org/10.1371/journal.pone.0110363

Editor: Elliott Lee Hazen, UC Santa Cruz Department of Ecology and Evolutionary Biology, United States of America

Received: March 25, 2014; Accepted: September 18, 2014; Published: October 22, 2014

This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the Supporting Information files.

Funding: This research was initiated while TBF held a National Research Council Research Associateship Award at NOAA's Northwest Fisheries Science Center, and conducted in part while TBF was employed by the Puget Sound Institute, funded by the Environmental Protection Agency (Grant #PC-00J303-01). This work was conducted in part while EMW was a postdoctoral associate at the National Center for Ecological Analysis and Synthesis, a Center funded by the National Science Foundation (Grant #EF-0553768), the University of California, Santa Barbara, and the State of California, and in part while she was a National Science Foundation Postdoctoral Research Fellow in Biology (DBI-0905806), and also while she was supported by the NSERC CREATE training program in biodiversity research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

One of the most important challenges facing ecologists is specifying how global change will affect community stability and the production of associated critical ecosystem services. Community stability is mediated by species interactions, which are sensitive to changing environmental conditions [1] , [2] , and therefore estimating the effects of environmental drivers on food web dynamics is critical for understanding how anthropogenic forces have altered ecosystems and for anticipating further change [3] , [4] . Analyzing food web dynamics is complicated in part because the communities we observe are likely not in “equilibrium” as we might have once expected [5] . There is increasing evidence that the structure of communities and the nature of species' responses to each other and to their environments are not static, but rather shift over time. In particular, anthropogenic pressures may be pushing communities further from equilibrium [6] , with communities exhibiting a variety of non-equilibrium dynamics from smooth trends to abrupt step changes [7] . Changes in abiotic conditions of ecosystems can directly and indirectly affect food web structure [8] . Thus, food web models must account for diverse temporal changes in community dynamics. In some systems, while we may have a good understanding of average species interactions or effects of the environment on food web dynamics over key time periods, we may still lack important information about whether and how such dynamics changed over time in response to large shifts in the ecosystem.

Lake Washington, U.S.A., is an example of an aquatic ecosystem that experienced a series of well-described dramatic changes in its environmental conditions and plankton community in the mid-20 th Century. This time period included a regime shift from one of high nutrient loading from sewage inputs to one of increased water clarity, as well as temperature and species abundance changes [9] – [11] . The lake also experienced shifting regimes in terms of plankton community dominance. During the era of high sewage inputs, the lake experienced extensive nuisance algal blooms, especially of the cyanobacterium, Oscillatoria rubescens . Following sewage diversion, water clarity increased substantially [12] ; subsequently, the influential grazer Daphnia established in the lake [11] and Oscillatoria effectively disappeared from the record. In more recent years, warming temperatures have caused phenological changes in phytoplankton and zooplankton [10] , [13] , [14] . What is unclear is how these changes in the plankton community and abiotic conditions affected interactions within the food web concomitant with the changing environment. Such shifts in plankton community interactions – such as weakening of grazer effects on phytoplankton, or increased competition among grazing zooplankton guilds – would have consequences for higher trophic levels in lakes, as plankton provides an important component of the energetic support for some lacustrine fish [15] , including in Lake Washington [16] . Moreover, plankton community structure and indirect effects of herbivore-plant interactions can influence fundamental lake characteristics such as light, temperature and water clarity [17] , [18] . In this paper, we introduce an extension of a well-used static food web model – a multivariate autoregressive (MAR) model [19] – [21] – to study Lake Washington's dynamically changing food web and ecosystem.

Over the last several decades, multivariate time-series methods have been used to estimate the strength and pattern of species interactions and the effect of abiotic drivers on communities [20] , [22] . MAR models provide a locally linear approximation of non-linear stochastic multispecies processes. They have been particularly useful in aquatic ecosystems and for understanding plankton dynamics in part because of the tight coupling between plankton and their environment. MAR models have also become useful in broader aquatic food web analyses [23] , [24] , as they can incorporate multiple trophic levels and environmental drivers.

Prior implementations of MAR models have assumed that the interactions in the study system were unchanging over the time period encompassed by the data. This approach maximized the performance of parameter estimation given the properties of monitoring data, but only estimated the average interaction strengths over a time series. In contrast, if food web dynamics shift in response to changing drivers [25] , then a better analytical approach would accommodate and capture this non-stationarity in modeling the food web. A suite of statistical methods can be applied to ecological time series to examine non-stationarity – such as shifts in abiotic conditions or periodicities – through time. Methods such as wavelets [26] , [27] , single-spectrum [28] and breakpoint analyses have been used in climatology and paleoclimatology, and have also recently been applied to ecological data [29] , [30] . Such methods allow ecologists to see how abundances may be shifting [30] or how interactions among species may change over time in simple lab systems [29] , but they do not provide a cohesive ecosystem approach to examining how integrated abiotic and biotic forces may change through time. In particular, food web responses to changes in the strength or nature of abiotic drivers would be predicted to cause cascading shifts in the interactions among many members of a food web, and may also feed back to how community members respond to other environmental drivers. Examining such a suite of interactions and drivers, however, would require a model that analyzes all the variables at once, and that allows estimation of such shifts through time.

A running or moving window approach is another tool that has long been used in other disciplines, such as finance, to examine non-stationarity in time series. In this approach, consecutive and overlapping subsets of time series – or windows – are analyzed individually to detect changes through time in a historical record [31] , [32] . This approach has recently been used with univariate autoregressive models to develop leading indicators of regime change [33] – [35] . Here we offer an extension of the MAR model, which we term “moving-window MAR” (mwMAR), and we use it to examine a case of shifting species interactions and environmental effects on species through time. Our approach blends the community focus of the MAR model with the moving window approach of detecting historical changes in time-series data. We describe the mwMAR model and then apply the model to long-term monitoring data from Lake Washington, U.S.A., to show how interactions among dominant taxa of the plankton community shifted following sewage diversion. Because food webs show sensitivity to changes in their abiotic environment [6] – [8] , we hypothesize that changes in the nutrient status, clarity, and dominant plankton taxa of the lake would cascade throughout the plankton food web, resulting in shifts in the direction and strength of community interactions, which would in turn affect community stability.

Materials and Methods

Model configuration.

We estimated interaction strengths among phytoplankton and zooplankton guilds, environmental effects on phytoplankton and zooplankton abundance, plankton intrinsic growth rates, and plankton community stability in Lake Washington from 1962–1994 using multivariate autoregressive (MAR) models. MAR models are stochastic models describing changes in species abundance through time as a function of species interactions and environmental influences, while accounting for temporal autocorrelation in species abundances [20] , [36] , [37] . MAR models can also be used to estimate various metrics of community stability, such as return time to a stationary state following an ecosystem perturbation, or the distance away from a stationary state that an ecosystem can be pushed by a perturbation. Previous work has used MAR models to describe environmental effects on, and interactions among, lake phytoplankton and zooplankton [20] , [22] , [38] , [39] , effects of climate regime shifts on interactions among marine plankton [40] , causes of estuarine fish declines [24] , and effects of fishing on marine food webs [23] . Extended descriptions of MAR approaches to time-series data have been given previously [19] , [20] , [37] , so we provide only a brief review of the model structure here.

We also used MAR models to estimate community stability. Specifically, we estimated the rate at which the system returns to its stationary distribution following a disturbance by the maximum eigenvalue of the B matrix (that maximum eigenvalue is henceforth referred to as lambda, λ). Systems with values of λ closer to 0 are considered to be more stable because they tend to return to equilibrium conditions faster than systems with values of λ farther from 0 [21] .

MAR models estimate mean intrinsic growth rates (captured by the A vector), community interactions (captured by the B matrix), environmental effects (captured by the C matrix), and community stability (captured by λ) across a given time series [20] . Here we use MAR models to quantify changes in interactions through time, by modeling community interactions for overlapping subsets of a time series, or moving “windows” of time, thereby estimating trends in MAR parameters. For a p × n matrix X of time series observations consisting of successive p ×1 vectors X 1 , X 2 ,…, X n , and a moving window of size W < n , we estimated MAR parameters within n - W -1 successive windows. These windows contained data from X 2 : X W +1 , X 3 : X W +2 ,…, X n - W +1 :X n . Note that the time series starts at t  = 2 to allow for the lag-1 effect in Eq. 1. The output of the mwMAR analysis is a new time series of estimated MAR parameters.

Lake Washington data and analysis

To investigate changes in interactions among zooplankton and phytoplankton guilds and the effects of environmental covariates in Lake Washington through time, we implemented the mwMAR approach using monthly plankton and environmental data from Lake Washington (Washington, U.S.A.) spanning 1962 to 1994 (396 timesteps; see Figure S1 for plankton time series). Our 33-year time series begins in the year of maximum sewage input (1962) when the lake experienced extensive nuisance algal blooms, especially of the cyanobacterium, Oscillatoria rubescens . Sewage diversion began the following year (1963), and was completed in 1968. Water clarity increased substantially by 1971 [12] and continued to improve through 1976, when the influential grazer Daphnia established in the lake [11] and Oscillatoria abundance decreased dramatically. Despite low abundances at times, and periods when they were not observe in samples, neither Daphnia nor Oscillatoria ever technically went extinct in Lake Washington. Before they begun to be observed at high abundances in 1973, Daphnia were observed every year but one (1971). Likewise, after their period of dominance ended in 1980, Oscillatoria continued (and continue) to appear in plankton samples, appearing in all but 3 years between 1980–1994.

The lake has additionally undergone significant warming throughout the historical record [10] , which has altered the timing of zooplankton abundance cycles [14] , [41] . Recent work, however, suggests species and nutrient (phosphorus) shifts related to the sewage effluent have had a stronger influence on the lake than shifts associated with warming [42] . These well-documented shifts in environmental drivers and plankton dynamics make Lake Washington an ideal ecosystem for evaluating the mwMAR model's sensitivity to non-stationary process. Indeed, the dominant environmental drivers and species interactions in Lake Washington are well-studied via observational [9] , [12] , experimental [43] , [44] and traditional MAR approaches [39] , [45] , offering the necessary background to build informed community and environmental interaction matrices ( B and C matrices, respectively).

For our analyses we aggregated physical, chemical and plankton community data, which were collected at various intervals, into monthly means. Previous analyses of the Lake Washington plankton community interactions identified a simplified food web containing species that demonstrated strong roles in structuring the community [39] , [45] . We targeted the most strongly-interacting taxa of this simplified food web with the present analysis, to determine how the dominant interactions changed through time. While weak species interactions can be important in structuring food webs, we chose to focus on the dominant taxa and interactions as a first test of this new method. These taxa were pooled into four taxonomic groups: diatoms and green algae – “DG,” both palatable food for grazing zooplankton; Oscillatoria – known to suppress Daphnia [44] ; Daphnia; and non-daphnid and non-cladoceran crustaceans – “NDC,” comprised of non-daphnid cladocerans, Cyclops , and Diaptomus . Group abundance data were log-transformed to better capture non-linearities [20] . A more complete description of the data is available in Hampton et al. [39] , and the raw data are available in Appendix S1 .

We included as covariates in the mwMAR model surface temperature and total phosphorus, because they were previously identified as the strongest environmental drivers of plankton abundance in the lake [39] , [45] . However, rather than simply use temperature as a covariate by itself, we instead used the data to estimate (1) a mean monthly signal indicative of long-term seasonal forcing, and (2) monthly deviations from the mean to capture short-term anomalies (e.g., a particularly warm July) or long-term trends (e.g., an overall increase). To ease comparison of effect sizes across all environmental covariates, we standardized all covariate data to a mean of 0 and a standard deviation of 1.

For our environmental covariate matrix ( C ) we included a priori only biologically meaningful interactions based on established environmental relationships: we assumed total phosphorus could not directly affect Daphnia or other zooplankton taxa. We expected shifts in mwMAR coefficients to lag behind known dates of change in the biotic community, sewage diversion and water clarity because our moving window size (7 years) is much larger than the timescale of most known changes. We graphically present all data at the end year of the moving window; thus, in our figures, results based on data from 1963–1970 would appear on the x-axis at year 1970.

Sensitivity analysis

The accuracy and precision of parameter estimates by the mwMAR model, as with other statistical methods, are sensitive to and affected by multiple factors, including food web configuration (i.e., the number of interacting species and covariates), window size, the variance structure of the process errors, and outliers in the data (see Appendix S2 for discussion and additional model validation). We conducted several sensitivity analyses to ensure such factors were not influencing the mwMAR model estimates. For example, the Lake Washington dataset is of high quality, and our outlier inspection showed no influence of outliers on the final results. In addition, because there is a tradeoff between precision of parameter estimates and accuracy of those estimates that is defined by window size, we conducted tests using simulated time series based on the Lake Washington food web configuration, to determine the appropriate window size for analysis of the Lake Washington dataset. In those simulations, the parameter estimation accuracy decreased sharply at window sizes smaller than 75 time steps (see Figure S1 ), and therefore we use a window size of 84 (the next factor of 12 larger than 75, given the monthly time step in the Lake Washington data). We also conducted simulations to determine what bias, if any, exist in parameter estimates during periods when a system is undergoing transition between states, for example between a eutrophic and clear-water state as was the case with Lake Washington. Last, to ensure that the mwMAR model was capable of capturing shifts in species interactions and environmental conditions outside of the Lake Washington case study, we fit mwMAR models to simulated time series with known interactions (see Appendix S2 ).

Statistical programming

MAR and mwMAR modeling was done in MATLAB (2007, The MathWorks), using the open-source program LAMBDA ( [46] ; freely available from http://conserver.iugo-cafe.org/user/e2holmes/LAMBDA ) with additional programming by the authors. The coefficients of the A , B and C matrices were estimated using conditional least squares (CLS), and confidence intervals around each coefficient were established using 2,000 bootstrapped data sets. Each bootstrapped data set was generated by creating random E matrices and fitting the rest of the parameters using CLS (see [21] for details).

The mwMAR approach revealed changes in interaction strengths in the Lake Washington plankton community between 1962 and 1994 ( Figures 1 – 5 ; Figures S2 – S3 ). For example, there were changes in the effects of Oscillatoria on Daphnia and diatoms and green algae (DG) coincident with the community composition shift during which Oscillatoria abundance decreased and Daphnia appeared ( Figure 1 , Table 1 ). In the period following the first appearance of Daphnia in Lake Washington, the effect of Oscillatoria on Daphnia became increasingly negative and was strongest in 1976 ( Figure 1A ). Following the decrease in Oscillatoria abundance, the negative effect of Oscillatoria on Daphnia weakened, and there was no significant effect of Oscillatoria on Daphnia from late in 1982 until the end of the time series. There was no effect of Daphnia on Oscillatoria ( Figure 1B ) until after the decline in Oscillatoria and increase in Daphnia. By 1980, the interaction coefficient became negative, weakened in the late 1980s, and returned to neutral after 1990. Oscillatoria also had a negative effect on DG in the beginning of the time series, and this effect disappeared by the mid-1970s ( Figure 1C ).

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

Effects of Oscillatoria on Daphnia (A); Daphnia on Oscillatoria (B); and Oscillatoria on diatoms/green algae, DG, (C) estimated by a mwMAR model using an 84-timestep window (indicated by solid red horizontal line shown in A). The mwMAR-estimated effect of Oscillatoria on NDC was non-significant. Estimates are shown with 95% upper and lower CIs. Grey dotted lines indicate a neutral interaction; solid black lines indicate the average interaction across the full time series, as estimated by a traditional MAR model. The raw time-series data are given in (D), with years of significant known changes shown in shaded vertical bars. All results are presented at the end year of the moving window.

https://doi.org/10.1371/journal.pone.0110363.g001

Effects of Daphnia on diatoms and green algae, DG, (A) and non-daphnid cladocerans and non-cladoceran crustaceans, NDC, (B) through time as estimated by a mwMAR model with an 84-timestep window (indicated by solid red horizontal line in A). Estimates are shown with 95% upper and lower CIs. Grey dotted lines indicate coefficient values of 0; solid black lines indicate the average interaction across the full time series, as estimated by a traditional MAR model. The raw time-series data are given in (C), with years of influential known changes shown in shaded vertical bars. All results are presented at the end year of the moving window.

https://doi.org/10.1371/journal.pone.0110363.g002

Coefficients are estimated by a mwMAR model with an 84-timestep window (indicated by solid red horizontal line in A). Estimates are shown with 95% upper and lower CIs. DG  =  diatoms and green algae; NDC  =  non-daphnid cladocerans and non-cladoceran crustaceans. Grey dotted lines indicate coefficient values of 0; solid black lines indicate the average effect across the full time series, as estimated by a traditional MAR model. All results are presented at the end year of the moving window.

https://doi.org/10.1371/journal.pone.0110363.g003

Growth rates are estimated by a mwMAR model with an 84-timestep window (indicated by solid red horizontal line in A). Estimates are shown with 95% upper and lower CIs. Grey dotted lines indicate coefficient values of 0; solid black lines indicate the average rate across the full time series, as estimated by a traditional MAR model. DG  =  diatoms and green algae; NDC  =  non-daphnid cladocerans and non-cladoceran crustaceans. All results are presented at the end year of the moving window.

https://doi.org/10.1371/journal.pone.0110363.g004

Stability is given by λ, the maximum eigenvalue of the community interaction matrix, as estimated by a mwMAR model using an 84-timestep window (indicated by solid red horizontal line). Estimates are shown with 95% upper and lower CIs. The grey dotted line indicates coefficient value of 0; the solid black line indicates the average stability across the full time series, as estimated by a traditional MAR model. Results are presented at the end year of the moving window.

https://doi.org/10.1371/journal.pone.0110363.g005

https://doi.org/10.1371/journal.pone.0110363.t001

The effects of Daphnia on other plankton groups in Lake Washington also varied through time ( Figure 2 ). Daphnia had a negative effect on its main food source, DG, starting in the early 1980s, and the effect strengthened until the mid-1980s ( Figure 2A ). The effect remained negative, though slightly weaker, until the end of the time series. The effect of Daphnia on other zooplankton (NDC) also varied through time ( Figure 2B ). Similar to the Daphnia -DG interaction, after Daphnia established in Lake Washington, the effect of Daphnia on NDC became increasingly negative, reached its peak in the mid-1980s, then remained negative but weakened to the end of the time series.

Density dependence also varied through time for all plankton groups. Density dependence in DG decreased (i.e., the diagonal B matrix coefficient associated with DG increased) until after Daphnia established in the lake, after which density dependence increased ( Figure 3A ). Density dependence in the grazer group NDC increased steadily from the early 1970s until the late 1980s, after which it weakened until the end of the time series ( Figure 3B ). Daphnia density dependence increased from the time it established in Lake Washington until the end of the time series ( Figure 3C ). Oscillatoria density dependence weakened until its decline in abundance in the late 1970s, at which point it increased and held more or less steady from the early 1980s until the end of the time series ( Figure 3D ).

The MAR model also estimates density-independent intrinsic population growth (the A vector), and while many of the confidence intervals surrounding the A estimates overlapped zero for a portion of the time series, there were consistent trends in the estimates among different plankton groups ( Figure 4 ). For all four plankton groups, there were three distinct periods of intrinsic growth rate estimates: (1) before regular appearances of Daphnia in Lake Washington (pre-summer 1973); (2) between when Daphnia began to make regular appearances, and when Daphnia established in the lake and Oscillatoria declined dramatically (summer 1973 – spring 1976); and (3) after the rise of Daphnia and decline of Oscillatoria (summer 1976 onward). During the first period, there was high variability and negative trends in all A estimates. During the second period, the DG growth rate was mostly constant ( Figure 4A ), both grazer groups growth rates increased (though some CIs overlapped 0; Figure 4B, C ), and the Oscillatoria growth rate decreased ( Figure 4D ). During the final period, from the mid-1970s to the end of the time series, the growth rates of most groups were constant, except for an increase in the DG growth rate. Both Oscillatoria and NDC had growth rates equal to zero during this period.

Stability (λ) decreased sharply from the beginning of the time series, and the system was least stable (i.e., λ was at its maximum value) in the early 1970s ( Figure 5 ). Following this nadir, community stability increased and reached maximum stability (i.e., the lowest λ value) at the end of the time series. Following bootstrapping, mean temperature had significant effects on all plankton groups. In contrast, very few effects of temperature anomalies or total phosphorus on plankton groups in Lake Washington were retained in the final mwMAR model ( Table 1 ; Figure S3 ).

We assessed the fit of the best mwMAR model to the Lake Washington data, and found that fewer than 1% of correlations between model residuals and data were significant. We also tested the model assumption of normally-distributed errors by applying the Shapiro-Wilk test [47] to the residuals of the MAR fit to each data window ( E , from Equation 1), with a Bonferroni-corrected alpha [48] to account for multiple null hypotheses. We rejected the null hypothesis of normally distributed errors in 65/312 windows for Daphnia , and in 217/312 windows for Oscillatoria (and in 0 windows for DG and NDC; Figure S4). These data windows for which the null hypothesis was rejected corresponded to periods in the time series when the abundance of each species was zero, i.e., the long one-sided tails in the data.

Shifting plankton dynamics in Lake Washington

We hypothesized that the mwMAR would show shifts in the interactions among the major taxa corresponding roughly with known periods of change in Lake Washington (e.g., years of and around 1968–1971, and 1976). For example, it has long been hypothesized that the highly-abundant Oscillatoria , owing to its low palatability, inhibited Daphnia before Daphnia 's increase in Lake Washington in 1976 [11] , during the period of time when the two species overlapped but Oscillatoria abundance was decreasing. These dynamics have been demonstrated experimentally [44] , but our results are the first to corroborate this hypothesis using historical data. During the period of time between the peak in water quality (1971) and the dramatic increase in Daphnia abundance (1976) – the period of overlap between Oscillatoria and Daphnia and hypothesized inhibition of Daphnia by Oscillatoria – we found an increasingly negative effect of Oscillatoria on Daphnia . Once the mwMAR window included only dates following the large increase in Daphnia (i.e., 1976 and later), there was no detectable effect of Oscillatoria on Daphnia . The long, filamentous shape of Oscillatoria generally makes it inedible for Daphnia , which is one likely source of the negative per-capita effect estimated here during their period of overlap.

Oscillatoria also had a negative effect on diatoms and edible green algae, the main food source for Daphnia and other grazers in the lake. High intrinsic growth rates in edible phytoplankton estimated at the start of the time series decreased during the period when Oscillatoria was dominant. At the same time, density dependence in diatoms and green algae also decreased, suggesting inhibition in growth, possibly resulting from competition for limiting nutrients, or physical shading or toxic effects of excretions by Oscillatoria . Such inhibition of algae by Oscillatoria has also been demonstrated experimentally [44] . This apparent inhibition of phytoplankton by Oscillatoria rapidly decreased following an abrupt transition in the mid-1970s when the negative effect of Oscillatoria on DG decreased and disappeared ( Figure 1 ). Coincident with these dynamics, the effect of Oscillatoria on Daphnia also weakened and the intrinsic growth rate of Daphnia increased from its minimum in 1972 to its peak in 1976 ( Figure 4C ). After 1976, Daphnia 's intrinsic growth rate decreased and density dependence increased ( Figure 3C ) as the Daphnia population increased in abundance. In addition, while the result was not significant (95% CIs overlapped zero), DG may have had a bottom-up positive effect on Daphnia after being freed from inhibition by Oscillatoria , in the latter half of the time series ( Figure S2 ). Taken together, these results corroborate the hypothesis that the establishment of Daphnia following the improvement of water quality in Lake Washington was impeded directly and indirectly by the cyanobacterium Oscillatoria .

Grazers are known to inhibit cyanobacteria under some environmental conditions [49] , and our analysis found a negative effect of Daphnia on Oscillatoria coincident with Oscillatoria 's decrease in abundance. In general, the frequency of cyanobacteria blooms is associated with the relationships between grazers and edible phytoplankton, such that when grazers and edible phytoplankton dynamics are stable (i.e., abundances do not undergo large, intrinsic oscillations), cyanobacteria are controlled by grazers [49] . These dynamics are often associated with phosphorus inputs to a lake. We observed a similar pattern in Lake Washington. As phosphorus inputs decreased, the grazing effect of Daphnia on edible phytoplankton increased concomitant with the inhibiting effect of Daphnia on Oscillatoria ( Figures 1 and 2 ).

MAR coefficients have been shown previously to reflect changes in community dominance, when an increase in the abundance of one species or group coincides with a decrease in another [40] , and therefore the negative effect of Daphnia on Oscillatoria may represent shifting dominance between the two taxa. The transition from Oscillatoria to Daphnia dominance was reflected in interactions among other plankton groups in the community. As the negative effect of Oscillatoria on Daphnia declined in the mid-1970s through to the early 1980s, and as Daphnia increased in abundance, Daphnia had stronger impacts on their main food source (DG) and competitors (NDC; Figure 2 ). At the same time, the strength of density-dependence ( Figure 3 ) and density-independent growth rates increased for the grazing zooplankton groups ( Figure 4 ), suggesting the release of the grazer community from inhibition by Oscillatoria . No previous work has shown an effect of Oscillatoria on other grazer groups beyond Daphnia , but the increase in population growth rates ( A matrix elements) of the NDC group following Oscillatoria 's decline suggests a possible negative interaction.

The negative effects of Daphnia on their food and competitors weakened towards the end of the time series, apart from an intensified grazing effect of Daphnia on DG at the very end. One potential explanation for the weakened grazing effect at the end of the time series relates indirectly to the warming of the lake during this time. Between 1962 and 2002, the lake surface temperature increased by 1.4°C during the stratified months, and associated with this warming was an advance in the spring phytoplankton bloom by 19 days [10] . Most of the warming and spring bloom advance occurred in the period 1962-1994. The weakening of the effect of total Daphnia on the phytoplankton group during that period, in the present analysis, could be a reflection of shifts in species-specific phenology and grazing characteristics [14] , [41] .

The results presented here highlight opportunities to learn more from time series data about how species interactions shift with changes in the environment across ecosystem types, and how those changing food web dynamics are liable to affect community stability and resilience to further disturbance. Ecosystem-based approaches to management often include a focus on food web dynamics, but quantifying changes in species interactions, and how those changes map onto the environmental template, proves difficult. Linking shifts in species interactions to specific environmental drivers opens opportunities to focus efforts aimed at retaining resilience as ecosystems undergo rapid change.

Community stability and environmental covariates

The Lake Washington system has undergone major shifts in chemistry and ecology that are reflected in community stability. The peak of instability occurred in April 1973, (a window that included data from May 1966 – April 1973; Figure 5 ). Values of λ greater than 1 indicate an unstable system [21] , and here λ exceeded 1 for windows ending in November 1970 – November 1974, representing the period of time between December 1963 – November 1974, inclusive. This is the time period that included major ecosystem shifts: high nutrient levels, sewage diversion, and nutrient reduction; high Oscillatoria abundance followed by its decline; and the first rare appearances of Daphnia . By the time of Oscillatoria 's disappearance, maximum water clarity, and establishment of Daphnia in 1976, the community stability was increasing, and continued to increase until the end of the time series. Thus, the period of time the lake was undergoing the most substantial and dramatic shifts throughout the ecosystem, and before Daphnia gained a foothold, was the least stable period in the community as well.

We observed effects of monthly mean temperature on the abundance of all plankton guilds ( Figure S3 ), which agrees with previous MAR analyses [39] , [45] , and with the MAR model estimated here from the whole Lake Washington time series ( Table S1 ). Previous work has suggested that Lake Washington plankton phenology also responds to lake warming [10] , [50] , and that the relationships between temperature and plankton taxa are evidence of the potential influence of a warming lake on food web dynamics [39] . However, we found no significant effects of deviations from the long-term seasonal temperature patterns, suggesting that lake-warming effects are not detectable in the abundance of these plankton guilds.

Caveats and considerations

Our results suggest moving-window MAR models may be useful in systems with sufficient time-series data for understanding shifting abiotic and biotic dynamics. As with all statistical methods, however, practitioners must consider possible caveats and issues in advance of and throughout analyses. The data and ecosystem considerations applicable to prior MAR model applications also extend to our moving-window approach. Users must have sufficient time-series data for valid parameter estimation, which varies depending on the time scale of interactions in the system and frequency of observations. The moving-window MAR model imposes the further consideration of having sufficient time-series data for multiple windows and surrounding the event(s) of interest. Importantly, bias in model estimates shrinks as the ratio between window size and system transition period increases, and users are cautioned to interpret model estimates during system transitions with consideration of such bias. However, the window could be configured for different purposes: made smaller to detect changes before they occur, or sized to optimize detection of a change in a particular state variable.

Applications of this method will benefit from a priori knowledge of ecological interactions and drivers in the modeled system to build a robust MAR model. In our analysis of the Lake Washington plankton community, we simplified the plankton community based on previous work that highlighted the strongest food web interactions and key environmental covariates [39] . However, Hampton et al. [39] also pointed out the importance of other plankton taxa in driving the dynamics of the dominant species in Lake Washington, such as Cryptomonas , picoplankton and non-colonial rotifers. Therefore, it is possible that additional food web dynamics contribute to the interaction coefficients observed here, which could be highlighted by future analyses. Furthermore, if the model failed to include an influential environmental driver of Lake Washington plankton dynamics, the model results might be erroneously interpreted: if one plankton guild responds negatively to an unmeasured environmental variable, and another guild responds positively, this might incorrectly be interpreted as a negative interaction between the two guilds. In the Lake Washington case, years of experimental work and field observations have identified environmental variables that are robust driving signals. In addition, preliminary, exploratory MAR model runs were performed to screen a broad suite of potential drivers on plankton time series data. The analyses here rely heavily on those two approaches to validation, and potential users are advised to similarly behave as ecological detectives.

Additionally, as with prior MAR approaches, users must invest time in simulation modeling that allows them to test how the approach is likely to work with data similar to theirs. Simulation of data from a model with similar parameters to the study ecosystem helps identify the appropriate moving window size and, thus, estimate the precision associated with future predictions of system change. Because much of the MAR approach is based on iterative fitting approaches, creating and testing simulation data sets from known parameter values with similar lengths, covariate and taxa numbers, and variance, is critical to interpreting knowledge gained from MAR models. For the moving-window approach, users should carefully examine the effect of window size on their simulation datasets (see Appendix S2 for an example analysis using simulated datasets). A priori knowledge or hypotheses related to the resolution of data and interactions as well as the strength and timing of the predicted shift should be considered during the process of simulation modeling. Comparison of the mwMAR output with whole time-series MAR estimates is useful in assessing when the broad confidence intervals estimated with the mwMAR model are potentially masking significant interactions.

Conclusions

Ecologists have recently gained an appreciation for the need to develop methods based on the underlying hypothesis that many systems are rarely, if ever, stationary. Here we present a method that allows researchers and managers alike to examine long-term monitoring data and develop a dynamic record of shifting interactions and drivers. By calculating indirect and direct effects over time, and their changes, mwMAR allows researchers to understand how species invasions and extinctions, shifts in temperature and nutrient loadings, and other anthropogenic perturbations may cascade and feedback through food webs and ecosystems.

Supporting Information

Lake Washington plankton densities from 1962–1994. Monthly means of densities for aggregated plankton groups used in mwMAR analyses. NDC  =  non-daphnid cladocerans; DG  =  diatoms and green algae.

https://doi.org/10.1371/journal.pone.0110363.s001

Time series of all community interactions. Interaction coefficients estimated for the Lake Washington time series with a mwMAR model, using an 84-month window. Figures show per-capita effects of plankton guilds in columns on plankton guilds in rows. Diagonal figures represent self-effects, or density-dependent effects on abundance.

https://doi.org/10.1371/journal.pone.0110363.s002

Time series of environmental covariate effects. Interaction coefficients estimated for the Lake Washington time series with a mwMAR model, using an 84-month window. Figures show the effects of covariates in columns on plankton guilds in rows.

https://doi.org/10.1371/journal.pone.0110363.s003

Quantile-quantile plots of residuals for the Daphnia and Oscillatoria time series. Shown are theoretical versus observed distributions of mwMAR model residuals for all windows where the Shapiro-Wilk test statistic was below the alpha value required to reject the null hypothesis of normally-distributed errors (61/1248 for Daphnia , 175/1248 for Oscillatoria , 0 for DG and 0 for NDC).

https://doi.org/10.1371/journal.pone.0110363.s004

Community and covariate matrix coefficients estimated by a MAR model for the full Lake Washington time series.

https://doi.org/10.1371/journal.pone.0110363.s005

Appendix S1.

Lake Washington plankton and covariate data, 1962–1994.

https://doi.org/10.1371/journal.pone.0110363.s006

Appendix S2.

Moving-window MAR Model Testing. Validation of the moving window MAR model approach, including accuracy of parameter estimation and estimation of bias during system transition.

https://doi.org/10.1371/journal.pone.0110363.s007

Acknowledgments

Many thanks to J. Regetz for assistance with coding. We thank D.E. Schindler for generous access to the Lake Washington data, the numerous people who have contributed to the data set, including A. Litt and S. Abella, and the organizations that have financially supported it, including the Mellon Foundation. The manuscript was improved by comments from D.E. Schindler, E.J. Ward and two anonymous reviewers.

Author Contributions

Analyzed the data: TF EW MS SK. Contributed reagents/materials/analysis tools: TF EW MS SK EH. Wrote the paper: TF EW MS SK EH SH.

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A Study in Pollution Control: How Seattle Cleaned Up Its Water

By E. W. Kenworthy Special to The New York Times

• Sept. 18, 1970

SEATTLE—A few weeks ago, a Seattle newspaper carried brief ‘article under the head line: “Flow of Raw Sewage In to Elliot Bay Ends.”

The gist of the item was that the last two sources of raw sewage on the bay, an arm of Puget Sound that forms much of downtown Seattle's water front, had been connected with a centralized metropolitan sewerage system.

The event, long anticipated here, attracted little attention among the nearly 400,000 users of the vast network of inter ceptor lines and treatment plants. But for people inter ested in pollution control, it was good news and it was im portant news.

For the forging of the last link in the sewerage system marks the culmination of 10‐year, $145‐million program that is a case study in how community willing to pay the price can clear up its water.

The ambitious program, car ried out by an organization formally named the Municipal ity of Metropolitan Seattle but known localy as “Metro” for short, is regarded by environ mentalists as exemplary in many ways.

Metro went to work long be fore saving the environment became a popular issue. It has succeeded in harnessing to gether the divergent interests and efforts of 18 separate met ropolitan governmental units. And it has been paid for al most entirely by local bond issues.

The White House Council on Environmental Quality, in its first annual report, cited Seat tle's Metro project as one bf the two outstanding anti‐pollu tion success stories in the na tion. The other was the clean ing tin of San Diego Bay.

Greater Seattle is 80 per cent surrounded by water, and its pollution problem was com pounded by geography and political structure. On the west lies Puget Sound. To the east is the freshwater Lake Wash ington, 20 miles long and two to four miles wide, bordered by many incorporated towns. The outlet for Lake Washing ton is the Duwamish River, which empties into Elliott Bay.

This was the situation in 1958 when Metro was formed to deal with the sewage prob lem.

On the Seattle waterfront and the Duwamish, there were four primary treatment plants. (A primary plant settles out solids and removes about 35 per cent of the organic matter.) But there were also 46 “out falls” dumping 70 million gal lons of raw sewage a day into Puget Sound.

The deep sound, with its tidal flow, might have been able to handle this if the out falls had been located off‐shore in deep water with defuser at tachments. But they were close to shore.

The result, according to Charles V. Gibbs, executive di rector of Metro, “was not only a terrible esthetic prob lem but a terrible bacterio logical problem as well.” The raw, stinking discharge floated around the docks and shore line. Almost all beaches were closed as unsafe.

Around Lake Washington, where suburbia had prolifer ated since World War H, there were 10 secondary sewage plants discharging 20 million, gallons of treated effluent into the lake each day from 23 cities and sewer districts. (A secondary plant removes 85 to 90 per cent of organic matter.)

The problem in Lake Wash ington was not bacteria; it was nutrients — phosphorous and nitrogen compounds in the effluent that stimulated the growth of algae.

When the algae died and de composed, oxygen in the water was depleted. The result was a cloudy lake, foul‐smelling and full of scum. The transparen cy of the lake—measured by the depth to which a white, eight‐inch disc is visible below the surface—decreased from 12 feet in 1950 to about two and one‐half feet in 1958. Many of the beaches on the lake were closed. Salmon suf fered as the dissolved oxygen became exhausted in the deep water.

Dr. W. T. Edmonson, a zo ologist at the University of Washington who began to study the pollution of Lake Washington back in 1952, de scribed the irony of the situa tion in the late ‘fifties. Noting that 10 treatment plants had been constructed since 1941 to deal with the “intolerable” con tamination from raw sewage, he wrote that “the situation had been changed from one in which the lake was con taminated with organic wastes to one in which it was being fertilized with inorganic ‘plant food.’ “

It was the studies of Dr. Edmondson and others by Dr. Robert O. Sylvester, a pro fessor of civil engineering at the University of Washington, that provided the spur for the creation of Metro. The princi pal civic force involved was the Municipal League of Port land. And the principal leader was James R. Ellis, who in 1953 was 32 years old, just three years out of law school and deputy prosecuting at torney for King's County, which includes Seattle and its environs.

In 1953, at the urging of Mr. Ellis, the Municipal League set up a Metropolitan Prob lems Committee, which spent two years digging into the problem of sewage pollution.

It was obvious to the com mittee that the problem could be solved only if a system was developed to serve the entire drainage basin. But such a system not only presented complicated design problems; it also raised jurisdictional problems on financing. Exist ing plants, some of them be ing financed by bond issues, would have to be abandoned. The suburban cities would have to be recompensed.

In 1956, the Municipal League recommended that the Mayor of Seattle appoint a citizens’ committee to prepare a report and draft legislation to create a metropolitan au thority to deal with areawide problems. The Mayor did so and named Mr. Ellis as chair man. The same year the state, county and city com bined to hire Brown & Caldwell, a sanitary engineering firm, to prepare an area sewage plan.

The citizens’ committee was ambitious. It wrote legisla tion permitting the formation of a “Metro” that would deal not only with sewage dis posal but also with transporta tion and comprehensive land use planning.

The state legislature passed the bill in April, 1957. But the actual establishment of Metro required a majority vote in both Seattle and the county. In March, 1958 the voters of Seattle approved it, but it was defeated in the outlying county and thereby killed.

The citizens’ committee thereupon redrafted the legisla tion to limit Metro's authority to sewage disposal, and city and county voters approved it in September, 1958.

Two Bond Issues Passed

As one of its first acts, the 21 members of Metro's de cision‐making body adopted the plan prepared by Brown & Caldwell. It provided for re tention of one small existing primary treatment plant on Puget Sound, and the construc tion of four large new plants —three primary plants on the sound and one secondary plant on the Duwamish. A total of 110 miles of interceptor lines and 19 pumping plants would channel the sewage to the treatment plants. All 10 plants on Lake Washington would be abandoned, and no more ef fluent would go into the lake. All raw sewage discharges into the sound would be halted.

The original plan called for a bond issue of $125‐million, but extension of the system to some suburbs not originally in cluded has required a supple mentary $20‐millionbond issue.

The bonds were to have been paid by additional sewer charges of $2.50 a month for each residential connection, with a proportionately higher charge for commercial and in dustrial connections. How ever, by careful planning, the residential fee was reduced to $2 a month before construction began in 1961 and has been kept at that figure.

Because it was begun long before passage of the Clean Waters Restoration Act of 1966, which provided Federal grants of up to 55 per cent of the cost of a sewage project, the Metro system has received less than 6 per cent of its financing from the Federal Government.

The system is now in full operation. The beaches on the sound and on Lake Washington are now open. In Lake Wash ington, phosphorous, which was 70 parts per billion in 1963, has fallen to 29 parts per billion, and summertime transparency has increased to nine feet. There has been a 90 per cent reduction in the oxygen demand of the effluent released into the Duwamish River, and salmon can now migrate to their spawning grounds.

“Without achieving a miracle or a utopia,” Mr. Ellis said, “Metro has nevertheless brought its civic activists some satisfying rewards. It has dem onstrated the great potential, of local Initiative in the Fed eral‐state‐local framework.”

Lake Annecy Story

Une œuvre collective exemplaire, lake washington story, lake washington is ten thousand kilometres and halfway around the world from lake annecy...., yet the stories of how these lakes were saved from pollution bear an astonishing resemblance., they are two twin pillars of the modern environmental movement, the first significant, successful, comprehensive environmental campaigns in history ¹.

Lake Annecy and Lake Washington are both are sizeable lakes in scenic mountain settings, home to a thriving  town and surrounded by an ever expanding lakeside community.

They both experienced the damage caused when sewage produced by this increasing urban population entered the lake and unbalanced a biological equilibrium evolved over millenia.  These were the first two lakes in the world where the problem of eutrophication was successfully identified and managed. In both cases this was the result not of government intervention from on high but of local grassroots action inspired by the vision of a handful of well-informed, courageous and dedicated concerned citizens.  In both cases an unprecedented political arrangement had to be made to get all the lakeside communities working together to solve the problem and in both cases the solution involved the largest and most expensive environmental investment made to date in their respective countries. And in both cases the results of their action were outstandingly successful, so that generations to come are able to  appreciate the fruits of their labours.

The story of Lake Washington, unlike that of Lake Annecy, is well documented in English. Chapter One begins with the story as set out on the website of King County, the local authority now responsible for managing the lake, as well as carrying out a wide range of services for a community of over 2 million citizens.  (By contract SILA, the authority which manages Lake Annecy, serves a community of around 250,000 and is focused solely on managing the lake).   Chapter Two is an outline of the story  from the point of view of one scientist  J. T. Lehman.   Chapter Three continues with J. T. Lehman, and his case study of the story.   Chapter Four introduces the most detailed account of the story, a fine book entitled  "The Uses of Ecology" written by W. T. Edmondson the scientist who played the key role in providing reliable information to the campaign to save the lake.   Chapter Five is the inside story of the creation of Metro, the innovative political association of local authorities put together to solve the pollution problem.  Metro is the direct equivalent of SILA in France, and their stories have many similarities, and some intriguing differences.  Chapter Six is an article from the local newspaper, the Seattle Times, just a few years ago, celebrating the work of Jim Ellis, one of the key figures in the campaign to save Lake Washington. Finally Chapter Seven brings us up to date with Lake Washington today, and gives an insight into the extensive work being done every year to continue the work set in motion all those years ago.

¹First significant, successful, comprehensive, environmental campaigns

This is a bold assertion, not least coming from an author who is neither an environmentalist, nor limnnologist, nor historian, nor journalist. It is based on the following reasoning.

These environmental campaigns were significant not only for the amount of money they cost (in each case the most expensive environmental investment to date in their respective countries) but also because of the size of the populations they served and the innovation in political organisation required to effect the work, namely the creation of Metro and SILA. The success of the campaigns has been not only acclaimed for the last fifty years by the local communities fortunate enough to have benefited from them, but also cited in scientific literature throughout the world as the problem of eutrophication has gradually become understood to be one of the major threats to global freshwater resources. These campaigns were comprehensive in that they addressed each of the five fundamental aspects of environmental action: they secured the sustainability of the lakes as a source of fresh drinking water, they reduced pollution of the local environment, they ensured the health and safety of those who used the lake for recreation, they protected the beauty of the natural environment and they secured and improved access to this beauty for the population at large. And these were environmental campaigns where local citizens raised the alarm and pressed for action, because the issue of lake pollution from sewage discharge was largely unknown at the time and so not within the sphere of routine government decision making about infrastructural investment.

By contrast the construction of just about any major urban sewage system could be classified as an environmental investment, and great works such as those of Haussmann and Belgrand in Paris would be good examples. And there are interesting histories preceding our story to be written about citizens' campaigns waged to compel reluctant local administrations to build what was necessary. For instance, "on at least two occasions in the late 1700s, Paris refused to build an updated water system that scientists had studied. Women were actually carrying water from the river Seine to their residences in buckets. Voltaire wrote about it, saying that they "will not begrudge money for a Comic Opera, but will complain about building aqueducts worthy of Augustus". Louis Pasteur himself lost three children to typhoid." ( Wikipedia )  But installing such sewage systems addressed just one environmental issue (crucial though it was): health and safety of citizens. And for centuries the need for them had not been a subject of scientific uncertainty. The question was not if, but when, to install them.

Introduction

Chapter One:        From the King County website

Chapter Two:      Battle to Save Lake Washington - an outline by J T Lehman

Chapter Three:   Lake Washington Case Study - J T Lehman

Chapter Four:    The Uses of Ecology, Lake Washington and beyond, by W T Edmondson

Chapter Five:    The Story of Metro, by Bob Lane

Chapter Six:       Will the next Jim Ellis please step forward? by Thanh Tan

Chapter Seven: Lake Washington today, back to King County website

Also, by contrast, there have been a number of significant environmental campaigns preceding our story which have contributed to laying the foundation of the modern environmental movement. Not least was John Muir's campaign in the US to establish Yosemite as a nature reserve protecting large tracts of beautiful landscape from the depredations of urban development or industrial exploitation. "In 1889, Muir took Robert Underwood Johnson, editor of Century Magazine, to Tuolumne Meadows so he could see how sheep were damaging the land. Muir convinced Johnson that the area could only be saved if it was incorporated into a national park. Johnson’s publication of Muir’s exposés sparked a bill in the U.S. Congress that proposed creating a new federally administered park surrounding the old Yosemite Grant. Yosemite National Park became a reality in 1890." ( US National Park Service ) John Muir was a remarkable individual who led a grassroots campaign and won over converts by celebrating the spiritual effects of the beauty of natural landscapes long before Dr. Servettaz spoke and wrote his praise for lake Annecy. However, his campaign addressed just one environmental issue (crucial though it was): protecting the beauty of the natural environment from industrial encroachment.

John Muir also founded the Sierra Club. "Founded by legendary conservationist John Muir in 1892, the Sierra Club is now the nation's largest and most influential grassroots environmental organization - with more than two million members and supporters. Our successes range from protecting millions of acres of wilderness to helping pass the Clean Air Act, Clean Water Act, and Endangered Species Act. More recently, we've made history by leading the charge to move away from the dirty fossil fuels that cause climate disruption and toward a clean energy economy." ( Sierra Club website ).   And it was from the Sierra Club, in the late 1960s amidst demonstrations in the US against the testing and development of nuclear weapons, that founders of two of the world's largest environmental campaigning organisations came, Friends of the Earth and Greenpeace.   "Friends of the Earth was founded in 1969 as an anti-nuclear group by Robert O Anderson who contributed $200,000 in personal funds and David Brower, Donald Aitken and Jerry Mander after Brower's split with the Sierra Club." ( Wikipedia ). Greenpeace was founded by, amongst many others, former members of Sierra Club. "The U.S. announced they would detonate a bomb five times more powerful than the first one. Among the opposers were Jim Bohlen, a veteran who had served in the U.S. Navy, and Irving Stowe and Dorothy Stowe, who had recently become Quakers. As members of the Sierra Club Canada, they were frustrated by the lack of action by the organization." ( Wikipedia ) These three organisations have led significant environmental campaigns around a wide range of issues, but these take place many years after our story.

John Muir's example further inspired the establishment of another environmental campaigning organisation in America, the Wilderness Society. "The Wilderness Society was incorporated on January 21, 1935 by a group of eight men who would later become some of the 20th Century's most prominent conservationists including Aldo Leopold: noted wildlife ecologist and later author of A Sand County Almanac. The Wilderness Act, considered one of America's bedrock conservation laws, was written by The Wilderness Society's former Executive Director Howard Zahniser. Passed by Congress in 1964, the Wilderness Act created the National Wilderness Preservation System, which now protects nearly 110 million acres of designated wilderness areas throughout the United States. One of The Wilderness Society’s specialties is creating coalitions consisting of environmental groups, as well as representatives of sportsmen, ranchers, scientists, business owners, and others. It states that it bases its work in science and economic analysis, often enabling conservationists to strengthen the case for land protection by documenting potential scientific and economic dividends. The Wilderness Society played a major role in passage of the following bills:

Wilderness Act (1964)

Wild and Scenic Rivers Act (1968)

National Trails System Act (1968)

National Forest Management Act (1976)

Alaska National Interest Lands Conservation Act (1980)

Tongass Timber Reform Act (1990)

California Desert Protection Act (1994)

National Wildlife Refuge System Improvement Act (1997)

The Public Lands Omnibus Act (2009), which added wilderness areas in nine states to the wilderness system. " ( Wikipedia )

The work of the Wilderness Society has much in common with the campaigns at Lake Washington and Lake Annecy. Both worked to protect the unspoilt beauty of the natural world. Both served as paradigms of enlightened civic action involving developing a broad base of support amongst the public and using science both to inform,  educate and convince members of the public. And both have led to significant practical improvement in the environment. However, as with their mentor John Muir, the first campaigns of the Wilderness Society were around the sole issue (crucial though it is) of protecting areas of natural beauty and the ensuing legislative successes of the Wilderness Society listed above came after the Lake Annecy and Lake Washington campaigns.

Interestingly, "the father of Earth Day, Gaylord Nelson is a former Wilderness Society board member and counselor. ( Wilderness Society website ) "He served three consecutive terms as a senator from 1963 to 1981. In 1963 he convinced President John F. Kennedy to take a national speaking tour to discuss conservation issues. Senator Nelson founded Earth Day, which began as a teach-in about environmental issues on April 22, 1970." ( Wikipedia ). Also around the time of the founding of Friends of the Earth and Greenpeace, "in 1969 at a UNESCO Conference in San Francisco, peace activist John McConnell proposed a day to honor the Earth and the concept of peace, to first be celebrated on March 21, 1970, the first day of spring in the northern hemisphere. This day of nature's equipoise was later sanctioned in a proclamation written by McConnell and signed by Secretary General U Thant at the United Nations. A month later a separate Earth Day was founded by United States Senator Gaylord Nelson. Nelson was later awarded the Presidential Medal of Freedom award in recognition of his work. While this April 22 Earth Day was focused on the United States, an organization launched by Denis Hayes, who was the original national coordinator in 1970, took it international in 1990 and organized events in 141 nations. Numerous communities celebrate Earth Week, an entire week of activities focused on the environmental issues that the world faces.  The first Earth Day celebrations took place in two thousand colleges and universities, roughly ten thousand primary and secondary schools, and hundreds of communities across the United States. More importantly, it "brought 20 million Americans out into the spring sunshine for peaceful demonstrations in favor of environmental reform." It now is observed in 192 countries, and coordinated by the nonprofit Earth Day Network, chaired by the first Earth Day 1970 organizer Denis Hayes, according to whom Earth Day is now "the largest secular holiday in the world, celebrated by more than a billion people every year." ( Wikipedia )    Earth Day, like Lakes Washington and Annecy,  began as an effort to educate the public about environmental issues, but it took place more than a decade after the lake campaigns.

Another celebrated campaign which preceded our story was "a notable act of wilful trespass by ramblers, undertaken at Kinder Scout, in the Peak District of Derbyshire, England, on 24 April 1932, to highlight the fact that walkers in England and Wales were denied access to areas of open country. The mass trespass marked the beginning of a media campaign by The Ramblers' Association, culminating  in the Countryside and Rights of Way Act 2000, which legislates rights to walk on mapped access land. According to the Kinder Trespass website, this act of civil disobedience was one of the most successful in British history." ( Wikipedia ). But again, this campaign addressed just one issue (crucial though it was): securing access to areas of natural beauty.

And finally, the first ever environmental campaign, according to the historian Harriet Ritvo in her book " The Dawn of Green ", was that at Thirlmere in England in the late nineteenth century. Manchester’s ambitious civic leaders decided to turn Thirlmire lake into a reservoir to supply drinking water to the city’s rapidly growing population. This involved a complex engineering project requiring the construction of a 50 mile pipeline. In opposition, a campaign arose led by an assortment of Lake District citizens, academics, artists and intellectuals from across the country, invoking an unprecedented claim - that the beauty of Lake Thirlmere belonged to all citizens of England, not just local landowners, and should not be damaged for the benefit of one particular town. The campaign was a failure and the reservoir project went ahead successfully, although after significant delay and additional expense. The parallels with our story are many. Thirlmere was a campaign to safeguard a lake, set in beautiful, mountainous landscape; it involved a large-scale engineering project; it concerned the pressing need to secure clean drinking water supplies to a growing population; and it used the argument that the beauty of nature should be preserved for all to enjoy, including future generations. But the differences are even more striking. The stories of Lakes Washington and Annecy turn out to be in direct contrast to that of Lake Thirlmere. These lake campaigns were not to prevent a large engineering project from taking place and damaging the environment but on the contrary to undertake such a project to protect the environment. The initiative to take action to secure the supply of clean drinking water came not from a big municipal local authority but from local citizens. The campaigns were entirely locally organised and not reliant on support from a diverse group of activists from across America or France. And last, and certainly not least, the campaigns were demonstrably successful. Rather than being the dismal cautionary tale to all environmentalists portrayed in Ritvo’s account of Thirlmere, they are fine examples of successful environmental campaigns to he held up as an inspiration to others.  It is in this context that it is asserted that Lake Washington and Lake Annecy represent the first significant, successful, comprehensive environmental campaigns in history.

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• Case Studies

On this page:

Arkansas River, CO

Willimantic river, ct, little floyd river, ia, long creek, me, presumpscot river, me, groundhouse river, mn, bogue homo, ms, little scioto river, oh, touchet river, wa, lake washington, wa, clear fork watershed, wv, elk hills, ca (terrestrial), upper arkansas river, co (terrestrial), birds of prey (terrestrial).

These fourteen (14) case studies illustrate how assessors have developed and interpreted evidence to determine causes of biological impairments. They provide examples of how to organize an assessment report, analyze data, and present results. Most of the cases assess rivers and streams, but a few assess terrestrial ecosystems.

The process for identifying causes of biological impairments continues to improve. As a result you will note differences among the case studies. In some examples, comments have been inserted by the U.S. EPA editor or the authors. These comments are not meant to indicate errors in the analyses. Rather, they suggest alternative approaches that users may apply in future assessments.

The full list of case studies are listed in the box to the right. The dots displayed in the map below show the approximate locations of where these case studies occurred.

Many of the following links exit the EPA web site

This case study used several evidence lines to show that metal exposure impaired benthic macroinvertebrates.

Effect : Altered benthic invertebrate assemblage Sources : Mining wastes Probable causes : Mixed metals Report : Arkansas River Case Study: Using Strength of Evidence Analysis. p. 4-11 in U.S. EPA (2000) Stressor Identification Guidance Document . U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025. Guidance, presentations, other : Clements WH (1994) Benthic invertebrate community responses to heavy metals in the Upper Arkansas River Basin, Colorado. Journal of the North American Benthological Society 13:30-44. Clements WH, Kiffney PM (1994) Integrated laboratory and field approach for assessing impacts of heavy metals at the Arkansas River, Colorado. Environmental Toxicology and Chemistry 13:397-404. Clements WH, Carlisle DM, Lazorchak JM, Johnson PC (2000) Heavy metals structure benthic communities in Colorado mountain streams. Ecological Applications 10:626-638. Kiffney PM, Clements WH (1994) Structural responses of benthic macroinvertebrate communities from different stream orders to zinc. Environmental Toxicology and Chemistry 13:389-395. Kiffney PM, Clements WH (1994) Effects of heavy metals on a macroinvertebrate assemblage from a Rocky Mountain stream in experimental microcosms. Journal of the North American Benthological Society 13:511-523. Nelson SM, Roline RA (1996) Recovery of a stream macroinvertebrate community from mine drainage disturbance. Hydrobiologia 339:73-84.

A screening assessment from a one-day workshop led to additional sampling. This sampling discovered an illicit toxic source, remediation of which led to improved aquatic life. This experience led the State to develop a causal assessment program. In turn, this program led the State to address impervious surface effects on stream condition.

Effect : Altered benthic invertebrate assemblage Sources : Impervious surfaces, upstream impoundments, concrete channels, waste water treatment facility, industrial outfalls Probable causes : Primarily a toxic effluent; secondarily sediment, altered food resources, increased temperature Report : Bellucci C, Hoffman G, Cormier S (2009) An Iterative Approach for Identifying the Causes of Reduced Benthic Macroinvertebrate Diversity in the Willimantic River, Connecticut . U.S. Environmental Protection Agency, Cincinnati, OH. EPA/600/R-08/144. TMDL : CTDEP (2001) Total Maximum Daily Load Analysis for the Upper Willimantic River (PDF) (16 pp, 382 K, About PDF ) . Connecticut Department of Environmental Protection, Stafford CT.

This case study illustrates the difficulties of assigning specific cause to biological impairment. Challenges included data collected in different ways, small discrimination between acceptable and impaired streams, and the presence of multiple stressors. This case study demonstrates several strategic techniques to address these challenges.

Effect : Altered fish and benthic invertebrate assemblages and a fish kill Sources : Row crop agriculture, hog production, wastewater treatment facility Probable causes : Primarily substrate alteration; secondarily nutrient enrichment and episodic toxic ammonia concentrations Manuscript : Haake DM, Wilton T, Krier K, Stewart AJ, Cormier SM (2010) Causal assessment of biological impairment in the Little Floyd River, Iowa, USA. Human and Ecological Risk Assessment 16(1):116-148. Report : Haake D, Wilton T, Krier K, Isenhart T, Paul J, Stewart A, Cormier S (2008) Stressor Identification in an Agricultural Watershed: Little Floyd River, Iowa .  U.S. Environmental Protection Agency, Cincinnati, OH. EPA/600/R 08/131. TMDL : IA DNR (2005) Total Maximum Daily Load For Sediment and Dissolved Oxygen, Little Floyd River, Sioux and O’Brien Counties, Iowa (PDF)   (32 pp, 378 K, About PDF ) . Iowa Department of Natural Resources, TMDL & Water Quality Assessment Section.

This detailed assessment illustrates the complexity of urban systems affected by many causes.

Effect : Altered benthic invertebrate assemblage, extirpated brook trout fishery Sources : Commercial and industrial area, airport, dairy Probable causes : Decreased dissolved oxygen, altered flow regime, decreased large woody debris, increased temperature and increased toxicity due to ionic strength Report : U.S. EPA (2007) Causal Analysis of Biological Impairment in Long Creek, a Sandy-Bottomed Stream in Coastal Southern Maine (Final Report) . U.S. Environmental Protection Agency, Washington DC. EPA/600/R-06/065F.

This is one of first two Stressor Identification case studies. The study was performed prior to development of the SI Guidance, and it informed guidance development. The weight of evidence was heavily influenced by the lack of co-occurrence of the effect with other candidate causes and by manipulations at a pulp mill on the Androscoggin River. Reductions in total suspended solids at the pulp mill led to recovery.

Effect : Altered benthic invertebrate assemblage Sources : Impoundment, paper and pulp mill Probable cause : Total suspended solids with floc Report : Presumpscot River, Maine. Ch. 6 in U.S. EPA (2000) Stressor Identification Guidance Document . U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025. TMDL : U.S. EPA (1998) New England’s Review of the Presumpscott River TMDL Memo (PDF)   (12 pp, 14.1.Mb, About PDF ) . [Last accessed 02/03/10] Guidance, presentations, other : Presumpscot River Plan Steering Committee (2002) Cumulative Impacts to Environmental Conditions on the Presumpscot River and its Shorelands (PDF)  (DRAFT – As distributed at the June 2002 Public Meetings) (102 pp, 1.3 Mb, About PDF ) . [Last accessed 02/02/10]

This screening assessment was done during a two-and-a-half day workshop. Findings were used to mount a more extensive watershed-scale assessment with additional data collection. Results of the screening assessment were confirmed and additional causes were characterized. The State adopted the Stressor Identification process and developed their own guidance and training materials.

Effect : Altered benthic invertebrate assemblage Sources : Waste water treatment facility, agriculture Probable causes : Sediment, nutrients Report : Lane C, Cormier S (2004) Screening Level Causal Analysis and Assessment of an Impaired Reach of the Groundhouse River, Minnesota. U.S. Environmental Protection Agency, Cincinnati OH. TMDL : Minnesota Pollution Control Agency (2009) Groundhouse River Total Maximum Daily Loads for Fecal Coliform and Biota (Sediment) Impairments (PDF)   (377 pp, 9.3 Mb, About PDF ) .  [Last accessed 01/31/10]  Guidance, presentations, other :  Minnesota Pollution Control Agency (2009) Brown's Creek Impaired Biota TMDL - Stressor Identification  (229  pp, 1.9Mb, About PDF ) .[Last accessed 03/31/12]

This assessment was one of the first cases undertaken by the State. It resulted in the State's streamlined stressor identification process. The State performed more than 700 court-ordered causal assessments for total maximum daily load (TMDL) development. A standard candidate cause list and screening levels developed at the program's beginning increased assessment speeds.

Effect : Altered benthic invertebrate assemblage Sources : Forestry, agriculture, reservoir Probable causes : Primarily dissolved oxygen and altered food resources Report : Hicks M, Whittington K, Thomas J, Kurtz J, Stewart A, Suter GW II, Cormier S (2010) Causal Assessment of Biological Impairment in the Bogue Homo River, Mississippi Using the U.S. EPA's Stressor Identification Methodology . U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R-08/143. TMDL : MDEQ (2005) Phase 1: Total Maximum Daily Load Biological Impairment Due to Organic Enrichment/Low Dissolved Oxygen and Nutrients: The Bogue Homo River, Pascagoula Basin, Jones County, Mississippi (PDF)   (44 pp, 681 K, About PDF ) . Mississippi Department of Environmental Quality, Office of Pollution Control, Jackson MS. Guidance, presentations, other : MDEQ (2004) Draft Stressor Identification for the Bogue Homo River, Forrest and Perry Counties, Mississippi. Mississippi Department of Environmental Quality, Office of Pollution Control, Jackson MS.

This is one of the first two Stressor Identification case studies. In addition to the original case, alternate formats for organizing data are presented in CADDIS.

Effects : Altered fish and benthic invertebrate assemblages Sources : Channelized stream, creosote plant and treatment facility, industrial waste site, waste water treatment facilities Probable causes : Altered habitat, PAHs, metal and ammonia toxicity in different segments Manuscripts : Norton SB, Cormier SM, Suter GW II, Subramanian B, Lin ELC, Altfater D, Counts B (2002) Determining probable causes of ecological impairment in the Little Scioto River, Ohio, USA. Part 1: Listing candidate causes and analyzing evidence. Environmental Toxicology and Chemistry 21(6):1112-1124. Cormier SM, Norton SB, Suter GW II, Altfater D, Counts B (2002) Determining the causes of impairments in the Little Scioto River, Ohio. Part 2: Characterization of causes. Environmental Toxicology and Chemistry 21(6):1125-1137. Report : Little Scioto River, Ohio. Ch. 7 in U.S. EPA (2000) Stressor Identification Guidance Document . U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025. Guidance, presentations, other : Ohio EPA (2008) Biological and Water Quality Study of the Little Scioto River (PDF) (59 pp, 1.04Mb, About PDF ). Ohio Environmental Protection Agency, Columbus OH. [Last accessed 02/02/10]

This screening causal assessment was a novel application of the Stressor Identification process for several reasons. It involved a long river stretch, in an arid watershed of the northwestern U.S. It also marked the first use of endangered salmonids as a Stressor Identification endpoint. Specific alteration of the invertebrate assemblage aided analysis.

Effect : Altered benthic invertebrate assemblages and extirpation of salmonids Sources : Wheat and irrigated agriculture, impoundments, logging, cattle raising Probable causes : Primarily water temperature and sedimentation; secondarily toxics, low dissolved oxygen, alkaline pH, reduced detritus, reduced flow and reduced habitat complexity Manuscript : Wiseman CD, LeMoine M, Cormier S (2010) Assessment of probable causes of reduced aquatic life in the Touchet River, Washington, USA. Human and Ecological Risk Assessment 16(1):87-115. Report : Wiseman CD, LeMoine M, Plotnikoff R, Diamond J, Stewart A, Cormier S (2009) Identification of Most Probable Stressors to Aquatic Life in the Touchet River, Washington . U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R 08/145. TMDL : Washington Department of Ecology. Walla Walla River Basin TMDL Water Quality Improvement Report (2007) and the Walla Walla Watershed TMDL Water Quality Implementation Plan (2008) with links to stressor-specific TMDLs. [Last accessed 05/27/18]  Guidance, presentations, other : Adams K (2010) Guidance for Stressor Identification of Biologically Impaired Aquatic Resources in Washington State . Washington State Department of Ecology, Olympia WA. Publication No. 10-03-036.

This is a brief synopsis of a historically important causal assessment of a eutrophic system. Evidence of world-wide consistency of association established general causality. Modeling was important in establishing specific causality.

Effect : Cyanobacteria blooms Sources : Waste water inputs Probable causes : Phosphorus Report : Lake Washington Case Study. p. 4-13 in U.S. EPA (2000) Stressor Identification Guidance Document .  U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025. Guidance, presentations, other : Summarized from Lehman JT (1986) Control of eutrophication in Lake Washington: Case Study. pp. 301-316 in Ecological Knowledge and Environmental Problem-Solving: Concepts and Case Studies. National Academy Press, Washington DC.

This case addresses a moderately sized drainage with several tributaries. Stressor-response relationships derived from field data prior to the assessment provided the primary evidence.

Effect : Altered benthic invertebrate assemblage Sources : Mining, logging, agriculture, and residential development. Probable causes : Sulfate/conductivity, organic and nutrient enrichment, acid mine drainage, residual metals (particularly aluminum) at moderately acidic pH, excess sediment, and multiple stressors Report : Gerritsen J, Zheng L, Burton J, Boschen C, Wilkes S, Ludwig J, Cormier S (2010) Inferring Causes of Biological Impairment in the Clear Fork Watershed, West Virginia . U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Cincinnati OH. EPA/600/R-08/146. TMDL : WVDEP (2006) Appendix 1. Clear Fork (PDF)   (14 pp, 372 K, About PDF ) in Total Maximum Daily Loads for Selected Streams in the Coal River Watershed, West Virginia. Prepared by Water Resources and TMDL Center, Tetra Tech, Inc., Charleston WV. Guidance, presentations, other : WVDEP (1997) An Ecological Assessment of the Coal River Watershed. West Virginia Department of Environmental Protection, Division of Water Resources, Watershed Assessment Program. Report number - 5050009 – 1997, pp. 93.

This case study deals with a contaminated terrestrial site and an endangered wildlife population. This study illustrates the importance of spatial and temporal scales of causes and effects. Based on mathematical modeling to link causes with population changes, it reverses a prior assessment’s findings.

Effect : Decline in abundance of the endangered San Joaquin Kit Fox Sources : Petroleum drilling, wastes, vehicles and drought Probable causes : Predation and accidents Report : U.S. EPA (2008) Analysis of the Causes of a Decline in the San Joaquin Kit Fox Population on the Elk Hills, Naval Petroleum Reserve #1, California . U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R-08/130.

This case study applied Stressor Identification to a highly mineralized area of the Colorado Rocky Mountains. Evaluated impairments were reduced vegetation, plant growth and species richness in meadows irrigated with Upper Arkansas River water. This study demonstrates aspects of the assessment process that may differ between aquatic and terrestrial systems.

Effect : Reduced plant growth and plant species richness Sources : Mining, smelting, agriculture Probable causes : Extrinsic metal with decreased pH (floodplain); extrinsic metal (irrigated meadows) Report : Kravitz M (2011) Stressor Identification (SI) at Contaminated Sites: Upper Arkansas River, Colorado . U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R-08/029.

This synopsis explains that the link between DDT and peregrine falcon decline was not initially recognized. The connection was made by re-examining the impairment description. Eventually it was recognized that the specific effect was reproductive failure due to eggshell thinning.

Effect : Decline of birds of prey Probable causes : DDT/DDE Report : Revisiting the Impairment in the Case of DDT. p. 5-2 in U.S. EPA (2000) Stressor Identification Guidance Document . U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025. Guidance, presentations, other : Blus LJ, Henny CF (1997) Field studies on pesticides and birds: unexpected and unique relations. Ecological Applications 7:1125-1132.  Grier JW (1982) Ban of DDT and subsequent recovery of reproduction in bald eagles. Science 218:1232-1234.

• CADDIS Home
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• Volume 2: Sources, Stressors and Responses
• Analytical Examples
• Worksheet Examples
• State Examples
• Volume 4: Data Analysis
• Volume 5: Causal Databases

Daniel B. Botkin

Solving environmental problems by understanding how nature works

An Environmental Success Story: Saving Mono Lake

July 3, 2012 By Daniel Botkin Leave a Comment

Mono Lake, salty and alkaline and California’s second-largest lake, became the center of controversy in the 1970s. It supported the world’s second-largest breeding colony of California gulls and was habitat to other bird species. Mono Lake was also beautiful, a large open body of water in desert landscape below the east slope of the Sierra Nevada, its shores lined in place with tufa towers, an unusual and curious geological feature. The streams that flowed into it were famous for some of the best recreational fishing in the U.S.

Since the 1940s, the city of Los Angeles had diverted all the stream water that had previously flowed into the lake. By the 1980s that water, the best quality the city had access to, provided 17% of Los Angeles’s water supply. But as a result of the stream water diversion, the lake level was dropping and the salinity and alkalinity of the lake increasing.

Mono lake's unusual chemistry supported a huge annual production of brine flies and brine shrimp, providing food for the more than 1.3 million birds that stopped at the lake to molt and feed during migration or to nest and breed. Many people feared that as the lake’s salinity and alkalinity increased, these would exceed the tolerance of the shrimp and flies, destroying the food base of the birds. The fear extended to concern that the lake would eventually dry to the point that all life in it would die, including the algae that were food for the shrimp and fly. The lowering lake level also caused several islands used by California gulls as nesting and breeding sites to become bridged to the mainland. Coyotes crossed the bridges, preying on gull chicks and disrupting breeding. Reproductive success plummeted. Even after the lake level rose during wet years and made the sites islands again, the gulls seemed reluctant to reoccupy them for several years.

For all these reasons, bumper stickers saying “Save Mono Lake,” became common and an environmental group, the Mono Lake Committee, led an effort to stop the water diversion to Los Angeles. The city in turn claimed that the lake’s life would not die, because the lake received ground water and direct rainwater that would keep it at a sustainable level.

Direct environmentalist action failed to stop the water diversions, so in the 1980s the Mono Lake Committee lobbied the California legislature, which passed a bill funding a scientific study to determine whether the lake would dry out to the point that the invertebrates and algae in the lake would become die out and the migrating and nesting birds would no longer be able to use the lake. I was asked by the State Department of Fish and Game to direct that scientific study, and formed a small scientific committee of scientists, interested in the lake, but who had no stated political bias about the water diversion issue. In addition to myself, members included: the famous geochemist Wallace S. Broecker, hydrologist Lorne G. Everett, limnologist Joseph Shapiro, and ecologist John A. Wiens, who was an expert on birds and their environments.

Our approach differed that of most large scientific analyses of major environmental problems. Typically, a large committee of well-known scientists would have a few meetings to discuss the problem and then write a report based on existing information. It was the scientific-consensus approach.

Our scientific committee, in contrast, was small enough to have direct discussions (that is arguments), met for longer periods, and maintained frequent communication among its members. It also had funds to support work by scientists already doing research at Mono Lake. But the work it funded first was not to be new research, but the integration and summarization of existing research. Surprisingly, such integration and summarization had not been done. The committee also retained sufficient funds to support some new research if that became necessary, which it did.

The key to whether the lake would continue to support brine flies, brine shrimp, and various species of algae was whether it would dry out to the point where it became so salty and alkaline that none of these species could complete their life cycles. Existing studies showed what levels of salinity and alkalinity would be lethal, but two things were missing to determine whether and when this would happen: a mathematical model was necessary to forecast the rate of water evaporation from the lake, and the total volume of water in the lake had to be known. Without these two kinds of analysis, the argument between the environmentalists and the city of Los Angeles could have gone on indefinitely with no way to resolve it.

To determine the water volume of the lake, we needed a map of the lake’s basin. But, surprisingly, nobody had ever done such a map. We hired an oceanographic mapping company to make that map, and consulted with a scientist who  developed a computer model of  rates of evaporation from the lake .

Ironically, more than a century earlier, Henry David Thoreau had run into the same problem. When he lived at Walden Pond, he complained that “There have been many stories about the bottom, or rather no bottom, of this pond, which certainly had no foundation for themselves. It is remarkable how long men will believe in the bottomlessness of a pond without taking the trouble to sound it,” Thoreau wrote during his sojourn there. “Many have believed that Walden reached quite through to the other side of the globe,” he continued.

Thoreau took a simple and direct approach to determining the depth of the pond: He measured it. He had the skill to do this because he worked now and again as a surveyor. "As I was desirous to recover the long lost bottom of Walden Pond,” he wrote, “I surveyed it carefully, before the ice broke up early in '46 with compass and chain and sounding line. I fathomed it easily with a cod-line and a stone weighing about a pound and a half, and could tell accurately when the stone left the bottom, by having to pull so much harder before the water got underneath to help me.” With the evaporation forecasting model and the volume of water in Mono Lake known, we were able to calculate how small the lake needed to be to kill off its life. This could be measured as the surface’s elevation above sea level, and we could calculate when this level was likely to be reached.

This study had two more unusual qualities to this study. First, rather than having our group of scientific experts tell the state and its citizens what to do, we presented options that, in our democracy, could be selected by the public or their representatives. We had learned from our study that the lake told a story of three crucial levels, which we showed as options to the public: the highest lake level that retained all the benefits of the lake; a lower level that kept the aquatic species going but sacrificed a fair amount of bird nesting habitat and scenic qualities; and a third level, which would cause the death of all the lake’s life. That level was just 28 feet below the then current level, and we forecast that it could be reached by this year---2012.

The second unusual quality of the study was that, in our description of the three options, we accepted that the climate was always changing, and that the lake and its surroundings experienced droughts and periods of high rainfall. We had information about the seriousness of the 50-year drought — the worst drought in recorded history--- that occurred on average at least once in 50 years. We explained to the public that to prevent the lake from falling below any of the crucial levels — whichever was chosen — the lake had to be managed to maintain in an average rainfall year a much higher level. This meant that when the 50-year drought happened, the lake would decline to, but not below, that crucial level.

Our report was taken up by the courts. Before our study, the courts had decided that unless any environmental damage could be demonstrated, the city of Los Angeles could continue to withdraw 100% of the stream flow that used to go into the lake. With our study in hand, the courts reversed that decision, and told the city that it could divert none of that water until the lake reached the highest of the three crucial levels. After several years of negotiations, the city gave up all rights to the waters that had fed Mono Lake.

In my years of trying to help solve environmental problems, this was one of the few successes. I attributed much of the success to the unusual methods we applied throughout the project. Interestingly, our study was made public in 1988. Today, 24 years later, the lake has still not reached that legally required level.

In sum, it is possible to find solutions to complex environmental problems when scientific analysis is applied appropriately. The unusual features of the Mono Lake study suggest several ways that success can be attained.

If you are interested in finding out more about Mono Lake and this study, you can refer to: Botkin, D. B. , 2001, No Man’s Garden: Thoreau and a New Vision for Civilization and Nature , Island Press. (Soon to appear as an ebook in all ebook formats)

Botkin, D.B., W.S.Broecker, L. G. Everett, J. Shapiro, and J. A. Wiens, 1988, The Future of Mono Lake , California Water Resources Center, University of California, Riverside, Report #68.

Botkin, D. B. And J. A. Wiens, 1988, “Mono Lake: Solving an Environmental Dilemma,” The World and I , Washington Times Corp. Vol. 3 No. 5: 198-205.  (copies of which can be obtained from D. B. Botkin)

Wiens, J. A., D. T. Pattern, D. B. Botkin, 1993, Assessing Ecological Impact Assessment: Lessons from Mono Lake, California, Ecological Applications 3(4): 595-609.

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