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Overview: Status of Inland Waters

Freshwater systems—lakes, wetlands, rivers, and streams—have been critical to the establishment of civilizations throughout human history. From ancient times, civilizations have been built based on their proximity to water: ancient Mesopotamia thrived because of the ample water provided by the Tigris and Euphrates rivers; ancient Egypt grew up along the Nile; the Romans expended vast resources in building elaborate networks of aqueducts to supply water to their cities. Water bodies are essential to humans not only for drinking but also for transportation, agriculture, energy production, industry, and waste disposal.

Despite the reliance of societies on freshwater systems, only in this century has the importance of protecting the quality of these systems become widely recognized. In the United States, the passage of the Clean Water Act in 1972 reflected widespread awakening to the deteriorating status of the nation's surface waters. The Clean Water Act set a goal of restoring all U.S. lakes and rivers to a "fishable and swimmable" condition by July 1, 1983. A court decision in 1975 ruled that under the act, the federal government also was obliged to protect wetlands (Mitsch and Gosselink, 1993).

The Clean Water Act focused on reducing municipal and industrial wastewater discharges to water bodies, and the results have been significant. In the decade following the act's passage, sewage discharges to U.S. surface waters dropped by 46 percent and industrial discharges by 71 percent, even though the population grew by 11 percent (Frederick, 1991). Two decades later, 85 percent of sewage plants and 87 percent of industrial plants discharging to water bodies were in compliance with the act (Kealy et al., 1993). Nevertheless, according to the Environmental Protection Agency (EPA, 1994), 40 percent of U.S. surface waters remain too degraded



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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology 1 Overview: Status of Inland Waters Freshwater systems—lakes, wetlands, rivers, and streams—have been critical to the establishment of civilizations throughout human history. From ancient times, civilizations have been built based on their proximity to water: ancient Mesopotamia thrived because of the ample water provided by the Tigris and Euphrates rivers; ancient Egypt grew up along the Nile; the Romans expended vast resources in building elaborate networks of aqueducts to supply water to their cities. Water bodies are essential to humans not only for drinking but also for transportation, agriculture, energy production, industry, and waste disposal. Despite the reliance of societies on freshwater systems, only in this century has the importance of protecting the quality of these systems become widely recognized. In the United States, the passage of the Clean Water Act in 1972 reflected widespread awakening to the deteriorating status of the nation's surface waters. The Clean Water Act set a goal of restoring all U.S. lakes and rivers to a "fishable and swimmable" condition by July 1, 1983. A court decision in 1975 ruled that under the act, the federal government also was obliged to protect wetlands (Mitsch and Gosselink, 1993). The Clean Water Act focused on reducing municipal and industrial wastewater discharges to water bodies, and the results have been significant. In the decade following the act's passage, sewage discharges to U.S. surface waters dropped by 46 percent and industrial discharges by 71 percent, even though the population grew by 11 percent (Frederick, 1991). Two decades later, 85 percent of sewage plants and 87 percent of industrial plants discharging to water bodies were in compliance with the act (Kealy et al., 1993). Nevertheless, according to the Environmental Protection Agency (EPA, 1994), 40 percent of U.S. surface waters remain too degraded

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology for fishing and swimming. Contaminated runoff from expanding urban and agricultural areas, airborne pollutants, and hydrologic modifications such as drainage of wetlands are just a few of the many factors that continue to degrade U.S. surface waters despite reductions in sewage and industrial waste discharges. Determining which of these factors has the most significant influence on the quality of a water body requires knowledge about how the water body interacts with its watershed and airshed and how the various inputs affect its physical, chemical, and biological characteristics. One of the critical sciences required to understand these freshwater interactions is called limnology (from the Greek limne, meaning pool or marshy lake). As defined in this report and other recent reports on the field, limnology includes the study of lakes, reservoirs, rivers, and freshwater wetlands (Edmondson, 1994; Lewis, 1995; Lewis et al., 1995). It is a multidisciplinary science that draws from all the basic sciences relevant to understanding the physical, chemical, and biological behavior of freshwater bodies. There are numerous subspecialties of limnology based on the application of fundamental sciences such as physics, chemistry, geology, and biology; branches of physical science such as optics, fluid mechanics, and heat transfer; and branches of biological science such as microbiology, botany, ichthyology, invertebrate zoology, and ecology. Limnology integrates these other sciences in order to study inland waters as ecological systems (Edmondson, 1994; Lewis, 1995). In a recent essay entitled ''What Is Limnology?" limnologist W. T. Edmondson (1994) described limnology as the study of inland waters … as systems. It is a multidisciplinary field that involves all the sciences that can be brought to bear on the understanding of such waters: the physical, chemical, earth, and biological sciences, and mathematics. Limnology thus has two distinguishing features: it is an integrative (i.e., interdisciplinary) science, and it consists of many component subspecialties (i.e., it is multidisciplinary). The interdisciplinary, multidisciplinary nature of limnology provides a broad perspective that is critical in identifying the multiple sources of stress that may prevent a water body from serving its essential functions. Although advances in limnology can play a critical role in improving the quality of fresh surface waters, prominent limnologists have expressed concern that the field is in decline (Naiman et al., 1995). Some have cited lack of a national research budget devoted to limnology (Jumars, 1990), others have identified lack of adequate educational programs (Wetzel, 1991), and still others have suggested inadequate attention by academic limnologists to contemporary environmental problems (Kalff, 1991) as the reasons for this decline. In a recent assessment of the status of limnology,

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology members of the American Society of Limnology and Oceanography warned, "Limnology shows signs of fragmentation, loss of identity, and poor sense of direction, all of which are reducing its potential for solving problems that arise from the escalating demands that society is placing upon inland waters" (Lewis et al., 1995). Because of the increasing importance of interdisciplinary water science in addressing environmental problems, the National Research Council's Water Science and Technology Board appointed a committee of 13 experts in limnology and related fields to evaluate what changes are needed to strengthen education in limnology. This report presents the committee's findings. The committee included representatives of universities, government agencies, private consulting firms, and research laboratories; members had expertise in ecology, zoology, water chemistry, hydrology, and environmental engineering, as well as limnology. In preparing its recommendations, the committee surveyed major universities with aquatic science programs and sought input from professional societies that include limnologists among their membership. The committee also held a workshop with aquatic resource managers to help develop practical recommendations for improving education in limnology. Traditionally, many have perceived limnologists as scientists who study primarily the biological properties of lakes. In this report, the Committee on Inland Aquatic Ecosystems has defined limnology broadly to include the biology, physics, and chemistry of all inland waters, including rivers and wetlands as well as lakes. Some scientists who study streams and wetlands, including several committee members, identify themselves as limnologists as well as stream or wetland scientists, while others do not. Regardless of where one draws the line in defining limnologist, lakes, rivers, and wetlands are interconnected, and the sciences that study them are closely allied. This report is designed to broaden the understanding of limnology and to provide a foundation for developing educational programs in limnology that will better prepare the next generation to address the world's many water quality challenges. Administrators of university and government science programs, students of aquatic science, and aquatic resource managers in government agencies and the private sector can use the report to learn more about the history and current status of human efforts to understand lakes, rivers, and freshwater wetlands. For administrators and teachers of aquatic science, the report recommends ways to strengthen university limnology programs to produce a generation of well-educated citizens, aquatic resource managers, and researchers capable of understanding and alleviating the many sources of water quality degradation. This chapter highlights the status of inland waters and the role of limnologists in improving these waters. Chapter 2 provides a history

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology of limnology, including profiles of several prominent limnologists and scientists in related fields, and evaluates the strengths and weaknesses of present-day limnology. Chapter 3 describes key contemporary water problems that have been studied by limnologists and whose solution will require further limnological research. Chapter 4 analyzes the current system for teaching limnology in institutes of higher education and recommends ways to restructure the system to strengthen limnological training. Chapter 5 recommends strategies for linking education and research in limnology with aquatic resource management. Also included in this volume are eight background papers prepared by committee members to stimulate the discussions that led to the writing of this report. The papers do not represent the consensus views of the committee as a whole but instead reflect the range of perspectives from which problems in aquatic science education and research can be viewed. FRESH WATERS AT RISK The condition of some important water bodies, such as the Potomac River and Lake Erie (see Boxes 1-1 and 1-2) has improved significantly in the two decades since the passage of the Clean Water Act. Nevertheless, many North American fresh waters remain degraded or at high risk. According to EPA reports to Congress on the status of U.S. waters, 43 percent of rivers are too contaminated to provide drinking water if treated with conventional water purification technologies,1 40 percent of rivers are too degraded to support aquatic life fully, and 32 percent are too contaminated for swimming, based on state surveys of 18 percent of the nation's total river miles (EPA, 1994). Similarly, 31 percent of lakes are too contaminated for drinking even with conventional treatment, 40 percent are unable to fully support aquatic life, and 36 percent are unsuitable for swimming, based on surveys of 46 percent of total U.S. lake area. Based on these data, it is clear that the United States is still a long way from achieving the goals of the Clean Water Act. Continued degradation of surface waters causes substantial economic losses, some of the most significant of which are associated with lost fishing revenues, increased costs for treating drinking water, and lost recreational opportunities. The fishing restrictions and fish consumption advisories common in polluted water bodies jeopardize the multibillion-dollar fishing industry. Recreational freshwater anglers spent $19.4 billion on their sport in 1985; the commercial fishing industry generated $3.6 1    For the state surveys that provided the basis for this estimate, the EPA defined conventional drinking water treatment as coagulation and sedimentation followed by disinfection. This type of treatment is designed primarily to remove turbidity and microbiological contaminants.

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology BOX 1-1 POTOMAC RIVER IMPROVEMENTS One partial success story of the Clean Water Act is the Potomac River, a 462-km (287-mile) water course that begins in West Virginia and flows into the Chesapeake Bay. Pollution episodes in the Potomac date back as early as the 1840s, when sewers first conveyed human wastes to the river from Washington, D.C. According to Civil War–era reports, President Lincoln frequently left the White House to escape odors emanating from the Potomac (Uman, 1994). Pollution in the river continued to worsen until, in 1934, the federal government appropriated funds to build the Blue Plains sewage treatment plant to remove settleable solids before the sewage entered the river. The plant's capacity was soon exceeded, however. As a result, discharges of raw sewage became increasingly common, and the river continued to deteriorate. In 1969, participants at a Washington, D.C., conference called the Potomac River "a severe threat to anyone who comes in contact with it" (Adler and Finkelstein, 1993). By 1970, the pollutant loading to the river was higher than it had been in 1932 (Uman, 1994). Algal mats choked a 50-mile stretch of the river downstream from Washington in late summer. Fishing and swimming were prohibited. Following passage of the Clean Water Act, the government spent $1.6 billion to upgrade the Blue Plains plant and in 1980 spent an additional $500 million to add advanced treatment systems. Recreational boating is now possible on the river. Bottom vegetation and bass have returned after a long absence (Uman, 1994). Despite these notable improvements, swimming in and consuming fish from portions of the river remain health risks (Interstate Commission on the Potomac River Basin, 1994). Contaminants such as chlordane, polychlorinated biphenyls, and heavy metals remain. In addition, the river is subject to bacterial contamination from discharges of raw sewage when major storms overload Blue Plains and other local sewage treatment plants. Thus, although the quality of the Potomac has improved substantially, it still does not meet the "fishable and swimmable" goal of the Clean Water Act. billion in revenues (including freshwater and saltwater harvests) in 1990 (Adler and Finkelstein, 1993). According to the EPA (1994), 1,279 fish consumption advisories—warning consumers and fishermen to limit intake of certain fish because of contamination—were in effect in 47 states in 1993; contaminant levels in fish tissues can be more than a million times those in surrounding water because of the tendency of contaminants to concentrate in species at higher levels of the aquatic food web. The need to provide more advanced levels of treatment for degraded sources of drinking water also has significant costs. For example, New York City may eventually be required to filter its drinking water because

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology of degradation of the once-pristine upstate New York reservoirs where the water is stored. The estimated cost for filtration is $1.5 billion to $5 billion for construction plus $300 million per year for operation and maintenance (Adler and Finkelstein, 1993). Losses of recreational opportunities when water is contaminated have extremely high costs. A 1986 survey by the President's Commission on Americans Outdoors found that 59 percent of Americans over age 12 fish and 27 percent boat each year (Kealy et al., 1993). In 1991, Resources for the Future, an economic study institute in Washington, D.C., surveyed Americans about their willingness to pay for clean surface water. On average, respondents indicated that they would be willing to pay $106 per year for boatable water, an additional $80 per year for fishable water, and an additional $89 per year for swimmable water, for a total of $275 per year (Adler and Finkelstein, 1993). Based on these responses, Resources for the Future estimated the value of restoring nonboatable water to swimmable condition to be $29.2 billion per year in 1990 dollars, with a reasonable range of $24 billion to $43 billion. Worldwide, contamination of waterways places artificial limits on the supply of potable water. The time required to replenish the water supply of a contaminated lake can be a decade or more (Wetzel, 1983), and the time to cleanse contaminated sediments can be much longer. Consequently, the effects of water quality degradation can be long-lasting and in some cases permanent. Where water resources are scarce, such as in parts of the western United States and other arid areas of the world, contamination of water bodies can threaten the livelihood of surrounding populations. SOURCES OF STRESS ON INLAND WATERS Progress in cleaning up U.S. surface waters has been limited in part because the types of problems affecting these waters are more complex than anticipated by the authors of major water pollution control legislation. In particular, the Clean Water Act addressed primarily one form of pollution: it required treatment of "point-source" discharges from municipal sewage treatment plants and industries. Contemporary water problems arise from a multitude of other causes in addition to point sources. Key causes of problems in freshwater ecosystems, described in more detail in Chapter 3, include the following: Runoff of pollutants from agricultural and urban lands: The EPA (1994) estimates that agricultural runoff impairs 56 percent of the nation's lakes and reservoirs and 72 percent of the nation's rivers and streams. Urban runoff from storm sewers is a cause of impairment of 24 percent of lakes and reservoirs and 11 percent of rivers and streams, according to the EPA. Like point-source sewage discharges, agricultural and urban runoff

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology BOX 1-2 PARTIAL RECOVERY OF LAKE ERIE News reports in the 1960s spoke of the demise of Lake Erie, but the lake has recovered in significant ways since 1972—the year the Clean Water Act was passed and the United States and Canada signed the Great Lakes Water Quality Agreement to curtail pollutant discharges to the lake. In the first part of the twentieth century, the Great Lakes in general and Lake Erie in particular supported one of the world's most valuable commercial fisheries. Lake Erie was more productive than the other lakes, in part because its relative shallowness provided an ideal environment for many species of commercially valuable fish (Egerton, 1987). Beginning in the 1900s, the composition of Lake Erie's aquatic community began to shift from commercially valuable fish such as lake trout and sturgeon toward fish such as catfish and carp that have lower market values. Lake trout, once abundant, had disappeared by 1950 and sturgeon by 1965 (Egerton, 1987). Fisheries biologists attributed loss of these and other valuable species to pollution, loss of habitat, and overfishing (Egerton, 1987). Several major urban and industrial centers—Buffalo, Cleveland, Toledo, and Detroit—lie along Lake Erie or its major tributaries. Prior to the passage of the Clean Water Act and the signing of the Great Lakes Water Quality Agreement, discharges of untreated or inadequately treated sewage and industrial wastes from these industrial centers into the lake were widespread. One of the key results of waste discharges to the lake, limnologists discovered, was an overabundance of phosphorus. The excess phosphorus caused excessive growth of algae, which in turn led to the proliferation of bacteria that decompose algae, a decline in the oxygen content of lake bottom waters as the algae decomposed, and loss of the valuable commercial fish that require high oxygen concentrations. For example, the concentration of algae near Cleveland increased 12-fold between 1930 and 1960 (Eos, 1971). By 1953, scientists had discovered that important native organisms retrieved from portions of the bottom sediments were dead as a result of lack of oxygen and that the native species had been replaced by worms and midge larvae, which tolerate low-oxygen environments (Egerton, 1987). The Great Lakes Water Quality Agreement called for all municipal wastewater treatment plants discharging more than 3,800 m3 per day (1 million gallons per day) to decrease the phosphorus concentration in their effluents to less than 1 mg per liter. The agreement also called for limits on the phosphate content of detergents—a key source of this element—and for reductions in industrial discharges of phosphorus. Simultaneously, the Clean Water Act provided funding to construct and upgrade sewage treatment plants, allowing most municipalities in the area to achieve or exceed the goals for phosphorus reduction. Between 1968 and 1982, the annual phosphorus load to the lake dropped from 28,000 tonnes to 12,400 tonnes (Great Lakes Water Quality Control Board, 1985). As a result, the massive algal blooms that were prevalent in the 1960s have been eliminated, oxygen concentrations have increased in bottom waters, and the water has become clearer (Great Lakes Water Quality Control Board, 1985).

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology The partial recovery of Lake Erie is one of the major success stories of the Clean Water Act, but at the same time the lake's problems are not over. The lake continues to receive excess phosphorus from agricultural runoff, and recycling of phosphorus that has accumulated in the bottom sediments continues. Although states surrounding the Great Lakes report that the presence of excess phosphorus and other elemental nutrients is now a major concern along less than 3 percent of Great Lakes shoreline, the presence of toxic compounds such as polychlorinated biphenyls remains a concern and has resulted in advisories against consuming Lake Erie fish (EPA, 1994). Furthermore, invasions of exotic species such as zebra mussels threaten to disrupt the lake's food web and its production of game fish (see Chapter 3). can convey large quantities of nitrogen, phosphorus, and organic matter that stimulate excess growth of algae and oxygen-consuming bacteria. This process, known as cultural eutrophication, ultimately results in loss of water clarity, loss of oxygen in bottom waters, and a shift in the food web from valuable game fish to less desirable species. High concentrations of pesticides also may be present in agricultural runoff; fish kills are commonly reported to insurance companies or the EPA when major storms follow pesticide applications (National Research Council, 1992). Storm runoff from urban areas also can transport high concentrations of pollutants such as lawn chemicals, metals, automotive oil and grease, and bacteria from animal wastes. Both agricultural and urban runoff contain sediment that can carry adsorbed contaminants and smother fish habitats and spawning areas. Alteration of natural hydrology: Throughout history, but especially in the twentieth century, humans have manipulated water bodies and their surrounding watersheds to serve purposes such as providing power, supplying water for irrigation, and regulating water flows to allow farming and building on floodplains. As a result, half of the wetlands, which once helped to cleanse the water flowing into rivers and lakes, are now gone from the lower 48 states (see, for example, Box 1-3) (National Research Council, 1995). The more than 80,000 dams in the United States (Frederick, 1991) alter downstream flow patterns in ways that can jeopardize the survival of important fish species. For example, 19 major dams and 100 smaller power projects have been built along the Columbia River in Washington and Oregon since the 1930s; the resulting habitat modifications have contributed to the extinction of 106 stocks of Pacific salmon that once spawned in the river (McGinnis, 1994). The EPA (1994) estimates that hydrologic, habitat, and flow modifications prevent desired uses of 36 percent of U.S. lakes and reservoirs and 7 percent of rivers and streams. Atmospheric transport of pollutants: Atmospheric circulation can transport

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology BOX 1-3 DEGRADATION AND RESTORATION OF THE FLORIDA EVERGLADES The Everglades ecosystem is a unique subtropical wetland system located in southern Florida. The Everglades landscape contains a multitude of wetland types, including sawgrass marshes, sloughs, marl- and peat-based wet prairies, tree islands, pinelands, and, at its southernmost extreme, mangroves and the Florida Bay estuary (Davis and Ogden, 1994). Before major human influence, the Everglades landscape was even more diverse and included custard apple swamps, short-hydroperiod wet prairies, and cypress stands. During the last century, the area of the Everglades has decreased by half due to agricultural and urban encroachment (Davis and Ogden, 1994). In addition, natural Everglades hydrology has been altered severely, with coincident disruption of ecological processes, by construction of numerous levees, canals, and pump structures (Davis and Ogden, 1994). Addition of unnatural levels of nutrients from agricultural runoff has exacerbated the decline of Everglades ecological integrity. The Everglades became a major focus of attention for Florida in 1988, when the federal Department of Justice sued the state, its Department of Environmental Protection, and the South Florida Water Management District for allowing the Everglades to become degraded as a result of nutrient pollution from the 700,000 acres of farms that border it to the north. As a result, in 1994 the state legislature passed a law, the Everglades Forever Act, that requires restoration of the ecosystem. Under the act, agriculture will pay for about half of Everglades water quality cleanup (up to about $300 million), with the other half coming from state and federal sources. Although there is little disagreement that the Everglades have been altered regrettably during the last century, there is considerable discussion about what a restored system should look like. What vegetation patterns existed before human influence? Were patterns constant or constantly changing? What hydropattern and nutrient levels would be conducive to restoring the landscape? Because half of the Everglades area has been lost to agricultural and urban uses, should the restoration goal be to reproduce the original Everglades in half the space? Alternatively, should restoration efforts return the Everglades that remain to what that particular area was historically, without attempting to restore short-hydroperiod wetlands that existed on the edges of the original Everglades? In addition, given that Florida Bay historically received water from an area twice the size of its current watershed, can sufficient water be sent to the bay through half of the original Everglades without adversely affecting upstream hydropattern restoration efforts? Intensive research and engineering efforts have been initiated by state, federal, and private interests to address these questions.

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology pollutants such as heavy metals, pesticides, polychlorinated biphenyls, and sulfuric and nitric acids (the damaging components of acid rain) to even the most remote environments (Czuczwa et al., 1984). For example, fish in some subarctic and high-alpine lakes contain toxaphene at levels above health standards (Kidd et al., 1995). Subsistence fisheries for aboriginal people are threatened in many areas of the far North (Lockhart, 1995). Pollutants affecting these remote areas are transported by air from the United States and Eurasia (Barrie, 1986; Lockhart, 1995). The contaminants concentrate in fatty tissues of organisms high on the food chain, in some cases rendering top predators 100,000 to 10 million times more contaminated than the rainwater that delivers the contaminants (Schindler et al., 1995). Introduction of exotic species and loss of native species: Exotic species introduced to a water body either on purpose or accidentally can decimate native species and significantly alter the aquatic food web. For example, nonnative plants such as water hyacinth, hydrilla, and Eurasian watermilfoil have spread to thousands of acres of U.S. lakes. The uncontrolled growth of these plants, some of which were introduced by the aquarium industry and others because they were regarded as visually attractive, interferes with swimming, clogs canals and drainage outlets, and alters the aquatic food web (National Research Council, 1992). Zebra mussels, introduced to the Great Lakes in 1986 from ship ballast water, are threatening the survival of important commercial fish and native clams and mussels (Roberts, 1990). In the Boundary Waters Canoe Area wilderness in northeastern Minnesota, walleyes and smallmouth bass at one time were stocked in some lakes, where they have taken hold, sometimes to the detriment of native species (Friends of the Boundary Waters Wilderness, 1992). Scientists have made similar observations in western mountain lakes: 80 percent of alpine lakes in the western United States have been stocked with nonnative species (Bahls, 1992). In western Canada, 20 percent of lakes in the mountain national parks have been stocked (Donald, 1987). Research has shown that these exotic species have altered natural food webs dramatically (Lamontagne and Schindler, 1994; Leavitt et al., 1994; Paul and Schindler, in press). Because of these and other problems, eliminating point-source discharges of pollutants to water bodies, while necessary, is insufficient to prevent further degradation of damaged aquatic ecosystems. Researchers have attempted to estimate the net effect of reducing point-source discharges, with discouraging results. For example, EPA researchers simulated point-source releases of contaminants along the 630,000 miles of larger U.S. rivers and streams that receive 85 percent of total point-source discharges in the United States and modeled the effects of decreases in discharges of biological oxygen-demanding materials, total suspended

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology solids, and fecal coliform bacteria as mandated by the Clean Water Act (Kealy et al., 1993). The results were disturbing: just 2.2 percent of the rivers changed their use support status—meaning that nonswimmable waters became swimmable, nonfishable waters became fishable, and so on—as a result of additional point-source controls. These figures may be low because they do not reflect the substantial improvements in water quality that have occurred even where use of the water remains unchanged, nor do they indicate reductions in types of contaminants other than organic matter, fecal coliforms, and suspended solids. Nonetheless, they indicate that controlling point sources of contamination eliminates only a part of the water quality problem. In contrast, the researchers estimated that reducing the nonpoint-source load by half would achieve much more significant reductions—for example, increasing the percentage of swimmable waters from 33 percent to 47 percent. Other researchers have estimated that 99.9 percent of sediment and more than 80 percent of nitrogen and phosphorus enter waterways via nonpoint sources (Shaw and Raucher, 1993). RESTORING INLAND WATERS: THE ROLE OF LIMNOLOGY Limnologists have made substantial contributions toward understanding and partially correcting damage to freshwater ecosystems. Notable contributions by limnologists include the following (see Chapter 3 for more details): Understanding the effects of excess nutrients and organic matter: By the mid-twentieth century, limnologists were conducting research that eventually quantified how human discharges of excess nutrients (primarily nitrogen and phosphorus) and organic matter (such as that contained in sewage) cause water quality to deteriorate rapidly through growth of excess algae and loss of dissolved oxygen (Hasler, 1947; Sawyer, 1947; Vollenweider, 1968). This discovery eventually led to programs and laws to reduce nutrient and organic matter discharges, and as a result the quality of many important water bodies has improved significantly. Identifying damage resulting from acid rain: Limnologists have shown that acid rain—caused by fossil fuel combustion and metal smelting—can lead to complete loss of important species, such as trout, in affected water bodies (Schindler et al., 1985). Such discoveries have been important catalysts in national and global agreements to control acid rain. Contributing to wetland restoration: The world's wetlands have been subjected to extensive drainage and destruction, particularly for agriculture and forestry in developed countries (Kivinen, 1980). Limnologists are playing a key role in developing the science needed to restore and protect wetlands.

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology Interpreting past characteristics of damaged water bodies: By examining the plant and animal remains in and the chemistry of aquatic sediments, limnologists have constructed models of damaged aquatic ecosystems in their pristine state (Bradbury and Megard, 1972; Gorham and Sanger, 1976; Davis and Berge, 1980; Gorham and Janssens, 1992). Through this process, limnologists can help design strategies to restore or partially restore the damaged ecosystems. As the complexity of freshwater problems increases, the role of limnologists in addressing these problems will become more critical. Environmental engineers can design systems for reducing pollutant inputs to a water body; fisheries biologists can determine water quality changes needed to rescue a threatened species of fish; hydrologists can identify water flow patterns influencing the movement of contaminants. However, the full range of actions required to restore a water body can best be identified by interdisciplinary teams of scientists including limnologists with experience in integrating the many factors that influence aquatic ecosystems into a broad picture of the whole system. The limited gains achieved in water quality to date are a result of focusing too narrowly on reducing inputs to lakes, rivers, and wetlands from point sources at the exclusion of considering the many other factors that influence water quality. In order to ensure that academic institutions and other educational venues are up to the task of training the next generation of limnologists, changes will be needed in the infrastructure underlying limnology education and research, as described in this report. REFERENCES Adler, R. W., and J. J. Finkelstein. 1993. The economic value of clean water. Pp. 8-2–8-19 in Clean Water and the American Economy—Proceedings: Surface Water, Vol. 1. EPA 800-R-93-001a. Washington, D.C.: Environmental Protection Agency, Office of Water. Bahls, P. 1992. The status of fish populations and management of high mountain lakes in the western United States. Northwest Sci. 66:183–193. Barrie, L. A. 1986. Background pollution in the arctic air mass and its relevance to North American acid rain studies. Water Air Soil Pollut. 30:765–777. Bradbury, J. P., and R. O. Megard. 1972. Stratigraphic record of pollution in Shagawa Lake, northeastern Minnesota. Geol. Soc. Am. Bull. 83:2639–2648. Czuczwa, J. M., B. D. McVeety, and R. A. Hites. 1984. Polychlorinated dibenzo-p-dioxins and dibenzofurans in sediments from Siskiwit Lake, Isle Royale. Science 226:568–569. Davis, R. B., and F. Berge. 1980. Atmospheric deposition in Norway during the last 300 years as recorded in SNSF lake sediments. II. Diatom stratigraphy and inferred pH. Pp. 270–271 in Ecological Impact of Acid Precipitation, D. Drablös and A. Tolken, eds. Oslo-Å: SNSF Project. Davis, S. M., and J. C. Ogden, eds. 1994. Everglades: The Ecosystem and Its Restoration. Delray Beach, Fla.: St. Lucie Press. Donald, D. B. 1987. Assessment of the outcome of eight decades of trout stocking in the mountain national parks, Canada. N. Am. J. Fish. Manage. 7:545–553.

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology Edmondson, W. T. 1994. What is limnology? Pp. 547–553 in Limnology Now: A Paradigm of Planetary Problems, R. Margalef, ed. New York: Elsevier. Egerton, F. N. 1987. Pollution and Aquatic Life in Lake Erie: Early Scientific Studies. Environ. Rev. 11(3):189–205. Environmental Protection Agency (EPA). 1994. National Water Quality Inventory: 1992 Report to Congress. EPA 841-R-94-001. Washington, D.C.: EPA, Office of Water. Eos. 1971. U.S. and Canada Agree on Anti-Pollution Measures for Great Lakes. Eos 52(8):581–582. Frederick, K. D. 1991. Water resources: Increasing demand and scarce supplies. Pp. 23–80 in America's Renewable Resources: Historical Trends and Current Challenges, K. D. Frederick and R. A. Sedjo, eds. Washington, D.C.: Resources for the Future. Friends of the Boundary Waters Wilderness. 1992. Visitor Use in the Boundary Waters Canoe Area Wilderness. Minneapolis: Boundary Waters Wilderness Foundation . Gorham, E., and J. A. Janssens. 1992. The paleorecord of geochemistry and hydrology in northern peatlands and its relation to global change. Suo 43:9–19. Gorham, E., and J. E. Sanger. 1976. Fossilized pigments as stratigraphic indicators of cultural eutrophication in Shagawa Lake, northeastern Minnesota. Geol. Soc. Am. Bull. 87:1638–1642. Great Lakes Water Quality Control Board. 1985. 1985 Report on Great Lakes Water Quality. Detroit: International Joint Commission, Great Lakes Regional Office. Hasler, A. D. 1947. Eutrophication of lakes by domestic drainage. Ecology 28:383–395. Interstate Commission on the Potomac River Basin. 1994. Signs could spur improvements, groups say. Potomac Basin Rep. 50(7):5. Jumars, P.A. 1990. W(h)ither limnology? Limnol. and Oceanogr. 35(5):1216–1218. Kalff, J. 1991. On the teaching and funding of limnology. Limnol. Oceanogr. 36(7):1499–1501. Kealy, M. J., T. Bondelid, and B. Snyder. 1993. Clean water and recreational use support: Has the Clean Water Act made a difference? Pp. 3-2–3-18 in Clean Water and the American Economy—Proceedings: Surface Water, Vol. 1. EPA 800-R-93-001a. Washington, D.C.: Environmental Protection Agency, Office of Water. Kidd, K. A., D. W. Schindler, D. C. G. Muir, W. L. Lockhart, and R. H. Hesslein. 1995. High toxaphene concentrations in fish from a subarctic lake. Science 269:240–242. Kivinen, E. 1980. New statistics on the utilization of peatlands in different countries. Pp. 48–51 in Proceedings of the Sixth International Peat Congress, Duluth, Minn. Jyska, Finland: International Peat Society. Lamontagne, S., and D. W. Schindler. 1994. Historical status of fish populations in Canadian Rocky Mountain lakes inferred from sub-fossil Chaoborus (Diptera: Chasboridae) mandibles. Can. J. Fish. Aquat. Sci. 51:1376–1383. Leavitt, P. R., D. E. Schindler, A. J. Paul, A. K. Hardie, and D. W. Schindler. 1994. Fossil pigment records of phytoplankton in trout-stocked alpine lakes. Can. J. Fish. Aquat. Sci. 51(11):2411–2423. Lewis, W. M. 1995. Limnology, as seen by limnologists. Water Resour. Update. (Winter):4–8. Lewis, W. M., S. Chisholm, C. D'Elia, E. Fee, N. G. Hairston, J. Hobbie, G. E. Likens, S. Threlkeld, and R. Wetzel. 1995. Challenges for limnology in North America: An assessment of the discipline in the 1990s. Am. Soc. Limnol. Oceanogr. Bull. 4(2):1–20. Lockhart, W. L. 1995. Implications of chemical contaminants from aquatic animals in the Canadian Arctic: Some review comments. Sci. Tot. Environ. 160/161:631–641. McGinnis, M. V. 1994. The politics of restoring versus restocking salmon in the Columbia River. Restor. Ecol. 2(3):149–155. Mitsch, W. J., and J. G. Gosselink. 1993. Wetlands, 2nd ed. New York: Van Nostrand Reinhold. Naiman, R. J., J. M. Magnuson, D. M. McKnight, and J. A. Stanford, eds. 1995. The Freshwater Imperative: A Research Agenda. Washington, D.C.: Island Press. National Research Council (NRC). 1992. Restoration of Aquatic Ecosystems. Washington, D.C.: National Academy Press.

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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology National Research Council (NRC). 1995. Wetlands: Characteristics and Boundaries. Washington, D.C.: National Academy Press. Paul, A. J., and D. W. Schindler. In press. Regulation of rotifers by predatory calanoid copepods (subgenus: Hesperodiaptomus) in lakes of the Rocky Mountains. Can. J. Fish. Aquat. Sci. Roberts, L. 1990. Zebra mussel invasion threatens U.S. waters. Science 249:1370–1372. Sawyer, C. N. 1947. Fertilization of lakes by agricultural and urban drainage. J. N. Engl. Water Works Assoc. 61:109–127. Schindler, D. W., K. H. Mills, D. F. Malley, D. L. Findlay, J. A. Shearer, I. J. Davies, M. A. Turner, G. A. Linsey, and D. R. Cruikshank. 1985. Long-term ecosystem stress: The effects of years of experimental acidification on a small lake. Science 22:1395–1401. Schindler, D. W., K. A. Kidd, D. C. G. Muir, and W. L. Lockhart. 1995. The effects of ecosystem characteristics on contaminant distribution in northern freshwater lakes. Sci. Tot. Environ. 160/161:1–17. Shaw, W. D., and R. S. Raucher. 1993. Recreation and tourism benefits from water quality improvements: An economist's perspective. Pp. 3-19–3-33 in Clean Water and the American Economy—Proceedings: Surface Water, Vol. 1. EPA 800-R-93-001a. Washington, D.C.: Environmental Protection Agency, Office of Water. Uman, M. F. 1994. Blue Plains: Saga of a treatment plant. EPA Journal 20(1–2):20–21. Vollenweider, R. A. 1968. Scientific Fundamentals of the Eutrophication of Lakes and Flowing Waters, with Particular Reference to Nitrogen and Phosphorus as Factors in Eutrophication. Das/CSI/68.27. Paris: Organisation for Economic Cooperation and Development. Wetzel, R. G. 1983. Limnology, 2nd ed. Philadelphia: Saunders College Publishing. Wetzel, R.G. 1991. On the teaching of limnology: Need for a national initiative. Limnol. Oceanogr. 36(1):213–215.