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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.
