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Chapter XV: Lake Erie Eutrophication Controlled
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the three goals of the phosphorus control program of the 1978 Great Lakes Water Quality Agreement (GLWQA) for Lake Erie were, as noted: substantial reduction in the levels of algal biomass to below that of a nuisance condition; elimination of nuisance growths of algae in bays and other areas where they occurred; and restoration of year-round aerobic conditions in the bottom waters of the central basin. As the waters of Lake Erie, the smallest and most shallow of the Great Lakes, are more quickly turned over than those of the other lakes, limnologists expected that it would show the most rapid response to a comprehensive phosphorus control program like the one in its final phase of implementation as the 1990s began. However, they also recognized that the response time would likely be extended due to the appreciable regeneration of phosphorus from bottom sediments during periods of anoxia. Under the phosphorus reduction programs, Lake Erie began to show signs of improvement from the late 1970s, and, by the mid-1990s, the first of the above goals of the 1978 agreement had been realized and the second and third more or less met. An unprecedented and expensive cooperative effort of the United States and Canada, involving thousands of individual contributions by government officials, scientists, engineers, farmers, and members of the public, had Lake Erie Eutrophication Controlled 260 C H A P T E R X V brought eutrophication in Lake Erie under control some three decades after its unexpected emergence. By 1980, Charles E. Herdendorf and Laura A. Fay of the Ohio State University ’s Center for Lake Erie Area Research had already found a “general improvement” in the quality of Lake Erie’s open waters.1 Two years later, in September 1982, Herdendorf reported that changes that had begun to occur in the late 1970s were continuing: “nutrient loading is declining, phosphorus concentrations in the lake are dropping .l.l. ‘clean water’ forms of plankton and benthos are showing modest signs of recovery and fish populations are rebounding.”2 Although the improvements were small ones, a trend was “beginning to mount and it [was] becoming obvious to scientists, fishermen and shoreline dwellers alike that Lake Erie [was] recovering .” Also in 1982, the International Joint Commission (IJC) reported that the phosphorus control efforts in the lower Great Lakes Basin appeared to have at least arrested the discouraging trends that had been apparent in the late 1960s and early 1970s.3 Four years later, it announced “a reduction, indeed a reversal in some areas, of eutrophication.” Nuisance algal blooms were “no longer common occurrences.”4 In late 1987, the IJC’s Water Quality Board reported that “there have been significant reductions in phosphorus to all the Great Lakes, and cultural eutrophication problems have been largely resolved.”5 Lakes Superior and Huron remained oligotrophic, and Lakes Michigan, Erie, and Ontario had been restored to an oligo/mesotrophic state. The IJC hailed this result as “a major accomplishment .”6 In their joint review, in 1989, of phosphorus control measures , the United States and Canada commented: “Although Lake Erie has not fully recovered from eutrophication problems, there is ample evidence of improving conditions; the absence of algal scums and mats, and the growth of recreational activities reflect substantial improvements.”7 By that year, phosphorus loadings to the lower lakes were approaching the target loadings, and phosphorus concentrations in the open waters of the lakes agreed closely with projected ones (derived from models), confirming “the appropriateness and effectiveness of the original point source phosphorus control strategy.”8 In 1990, the governments of Canada and Ontario jointly observed that Lake Erie Eutrophication Controlled 261 [54.221.159.188] Project MUSE (2024-03-19 06:04 GMT) “Although phosphorus control measures were expensive to implement, they have been highly successful.”9 The following year, the thirty-fourth Conference on Great Lakes Research included a symposium on “Evidence for the Restoration of the Lake Erie Ecosystem.”10 The evidence strongly supported the widely held perception that environmental conditions in Lake Erie were tending toward a more desirable state. The western and central basins were becoming less eutrophic and more mesotrophic. Point and nonpoint source loadings of phosphorus had been greatly reduced, ambient phosphorus concentrations were at or near targeted levels, and some improvement in the depletion rate of dissolved oxygen in the central basin’s hypolimnion had been observed. The biotic community, both benthic and pelagic, had also been tending toward one more closely associated...