Lake Erie Rehabilitated: Controlling Cultural Eutrophication 1960s-1990s

Chapter I: Cultural Eutrophication: An International Problem

the cultural eutrophication of lakes emerged as a serious international environmental problem during the 1960s. It was promptly investigated by, among others, the Organization for Economic Co-operation and Development, international symposia of scientists and engineers, and agencies of the United States federal government. The increased concentration of phosphorus in lake water, contributed to significantly by the recently introduced synthetic detergents, was soon recognized as being in many instances the cause of the problem. Within the Organization for Economic Co-operation and Development (OECD), created in 1961, the Committee for Research Co-operation was responsible for providing information required in administering a number of public sectors of responsibility. One sector involved the national management of water as a resource, and the committee was actively concerned with water pollution problems from its creation, also in 1961.1 On February 16–17, 1966, it convened a group of experts at OECD headquarters in Paris to consider problems caused by eutrophication in Europe’s inland waters. The experts recommended that a comprehensive survey of the existing literature on eutrophication be made. Subsequently, the CommitCultural Eutrophication: An International Problem 14 C H A P T E R I tee for Research Co-operation commissioned Richard A. Vollenweider of the Italian Institute of Hydrobiology in Pallanza to “gather together and study the existing literature on eutrophication and to report particularly on the current status of work concerned with the part played by phosphorus and nitrogen in the process of eutrophication.”2 Vollenweider’s report was issued on September 17, 1968, and widely circulated.3 In preparing his report, Vollenweider had consulted thousands of publications dealing with all aspects of eutrophication. He found that whereas little had been published on the subject prior to 1940, eutrophication had since become a problem of increasing urgency in the more highly developed countries. More or less serious cases of eutrophication had been observed in lakes, reservoirs, and flowing waters in Germany, Switzerland, Austria, Italy, France, Belgium, Holland, Denmark, Norway, Sweden, Finland , United Kingdom, United States, Canada, Japan, USSR, Poland, Czechoslovakia, and South Africa.4 The serious damage sustained by many lakes had detracted from their scenic beauty, recreational potential, and general economic value. Vollenweider paid particular attention to quantitative studies and their conclusions,5 and as his survey progressed he became convinced that it would be essential to have three subjects thoroughly investigated on an international cooperative basis. These were the maximum permissible phosphorus and nitrogen loadings in relation to associated morphological, hydrological , and bioclimatological factors; the exact quantitative aspects of nutrient sources; and the roles of trace elements and organic factors. Regarding the first two subjects, Vollenweider considered precise knowledge a prerequisite to any meaningful discussions of the need for and effectiveness of tertiary sewage treatment for the removal of nutrients. Nitrogen and phosphorus appeared to Vollenweider, and to the Committee for Research Co-operation, to be the most important of the nutrients responsible for eutrophication. Existing evidence suggested that, in regard to its trophic level, a body of water was in danger when (1) its springtime concentration of assimilable phosphorus and inorganic nitrogen compounds exceeded 10 mg/m3 (milligrams per cubic meter) and 200–300 mg/m3 respectively, and/or (2) the specific loading per unit area of lake reached 0.2–0.5 g P/m2 (grams of phosphorus per square meter) Cultural Eutrophication: An International Problem 15 per year and 5–10 g N/m2 per year. These yardsticks could not, however, be applied universally, as the trophic conditions in each location were complex , involving also other nutrients as well as morphometric, hydrological, optical, and climatic factors. With a view to providing practical guidance in combating eutrophication , Vollenweider sought to classify oligotrophic and eutrophic lakes according to their specific nitrogen and phosphorus loadings and to define numerically the transition from one class to the other. He regarded the following conditions as typical of incipient eutrophication: 1...A quantitative increase in the biomass, as observed either in the macrophytes [large plants] and periphytic [attached] algae near the shore, or in the planktonic algae of the pelagic [open lake] regions.l.l.l. 2...Qualitative and quantitative changes in the littoral [nearshore], benthic [lake bottom], and planktonic fauna, and in the fish population.l.l.l. 3....l.l. decreasing transparency and changing colour of the waters, the development of oxygen maxima or minima within the metalimnic [intermediate ] layers, and the overall decline in...