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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology (1996)

Chapter: 2 Limnology, the Science of Inland Waters: Evolution and Current Status

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Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 29
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Page 30
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Page 31
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 32
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 33
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Page 34
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Page 35
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 36
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 37
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 38
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 39
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 40
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 41
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 42
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 43
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 44
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 45
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 46
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 47
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 48
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 49
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 50
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 51
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 52
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 53
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 54
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 55
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 56
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 57
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 58
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 59
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 60
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 61
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 62
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
×
Page 63
Suggested Citation:"2 Limnology, the Science of Inland Waters: Evolution and Current Status." National Research Council. 1996. Freshwater Ecosystems: Revitalizing Educational Programs in Limnology. Washington, DC: The National Academies Press. doi: 10.17226/5146.
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Page 64

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LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 24 STATUS 2 Limnology, the Science of Inland Waters: Evolution and Current Status The origins of limnology date back many centuries to a time when scientists were called natural philosophers and science was explored by a few, usually wealthy, individuals. For example, Gorham (1953) traced the development of wetland ecology and some of its fundamental premises to studies of British natural philosophers going back to the fifteenth and sixteenth centuries. Similarly, Hutchinson (1967) traced studies on lakes at least as far back as a fifteenth century study on the ponds of a European abbey. However, the evolution of limnology into a modern science depended on the development of concepts and tools in biology, chemistry, and physics that were not available until the late nineteenth century. Although modern limnology encompasses the study of all inland waters, its development is particularly identified with the study of lakes. Much of the conceptual framework around which the science was built was derived from studies on lakes, and most of the early limnologists were lake scientists. A notable exception was Stephen Forbes, a principal architect of the framework for limnology who was trained as a fish biologist and spent most of his career working on rivers and streams in Illinois, a state with relatively few natural lakes. It is understandable why early limnologists focused on lakes. As systems with easily recognizable boundaries and long residence times for water and substances in it, they are more obvious subjects for systematic scientific analysis than are the open, flowing waters of streams and spatially less defined wetlands. Nonetheless, it must be noted that the historical treatment usually accorded to limnology is colored by the fact that it generally is written by lake scientists,

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 25 STATUS even though scientific studies on flowing waters and wetlands in some cases predate studies on lakes. Even today, many aquatic scientists in North America associate the word limnology with the study of lakes (and reservoirs). To the extent that there is any general awareness of the word limnology, this perception applies to the public as well. There are historical reasons for this situation, but it has caused difficulties in coalescing the various branches of limnology into a more coordinated and organized science. This chapter traces the history of the study of lakes, reservoirs, rivers, and wetlands. It includes biographical sketches of some of the individuals (limnologists as well as other scientists) who have contributed to the understanding of inland aquatic ecosystems and significantly influenced the field of limnology. The chapter concludes with an analysis of the current status of limnology with special reference to professional and educational issues in the United States. EARLY HISTORY The beginnings of limnology as a modern science usually are traced to the work of a few late nineteenth century biologists who focused on lake studies. The founders of lacustrine limnology defined the scope and nature of the field in a way that survives remarkably intact to the present day; they viewed the subject broadly and integratively. Francois Forel (see Box 2-1) was the first scientist to use the term limnology in a publication. His three-volume treatise on Lake Geneva (bordered by Switzerland and France), published over the period 1892 to 1904, is considered the first book on limnology, and it was encyclopedic in scope. Its 14 chapters define the main supporting fields of modern lake limnology (Edmondson, 1994) and reinforce the idea that lake limnology is the application of all relevant basic sciences to the analysis of lakes as fundamental units of study. The integrative nature of limnology was stressed even before Forel coined the term limnology. In a prescient article published in 1887, Stephen Forbes (Box 2-2) described lakes as ''microcosms," or little worlds. Although the term "ecosystem" was not introduced for another half century (Tansley, 1935), Forbes defined an approach that presaged this concept. He proposed that lake studies should focus on many of the processes that today define the field of ecosystem ecology: mineral cycling, production and decomposition of organic matter, food web interactions and their impacts on the structure of biological communities, and the effects of physical conditions on biological communities. Forbes viewed these topics as essential to understanding lakes as functioning, integrated systems. The notion of lakes as microcosms (or integrated ecosystems) has pervaded their study ever since Forbes' time, even though the concept has

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 26 STATUS BOX 2-1 FRANCOIS ALPHONSE FOREL (1841–1912) Francois A. Forel invented the word limnology. The science would have been called "limnography," to match its sister science oceanography, had it not been for the priority of reserving the term "limnograph" for a device used to measure water height in lakes. Forel was born in Morzes on the shore of Lake Geneva (known to the Swiss as Lac Leman). When he was 13, his father introduced him to "… the art of observing and questioning nature,'' according to a monograph that he later wrote about Lake Geneva (Forel, 1882, 1895, 1904). After graduating from the Academie de Geneve, Forbes completed a medical degree at Würzburg and taught there for three years. In 1870, he joined the faculty of the Academie de Lausanne, where he taught anatomy and physiology and started a lifelong study of Lake Geneva. One of Forel's earliest observations connected the physical, chemical, and biological properties of Lake Geneva. While looking to see if waves had left ripple marks on the bottom along the shore, he noticed a wriggling nematode in a sample of mud. This "poor worm" piqued his curiosity and led him to invent a bottom dredge with which he discovered that the depths of the lake were not a desert but were occupied by a specialized fauna rich in species and individuals. His studies resulted in a long series of influential papers on benthic fauna, their environmental conditions, and their significance to the fish population; the papers were consistent with modern concepts of ecosystem ecology. He followed with comparative work on other Swiss lakes. In physical limnology, much of Forel's attention focused on water oscillations that create standing wave patterns, known to limnologists as seiches. In addition to obtaining massive data on Lake Geneva itself, he studied movements of water in small, tilted model lake basins, thus anticipating by many years a kind of experimental limnology. From these studies he developed generalizations about the relations between the dimensions of lakes and the periodicity of their seiches. He also conducted pioneering work in other aspects of physical limnology, devising a color scale and studying light penetration with photographic paper, and considered external influences on the lake, particularly the relation of the water supply to glaciers. Henri LeBlanc (1912) listed Forel's publications in categories: limnology (126 titles), glaciology (66), seismology (12), meteorology (19), natural history (28), archaeology (12), history (10), and biographies (15). The massive Lake Geneva monograph Le Leman: Monographie Limnologique was published in three volumes in 1882, 1895, and 1904, with a total of 14 chapters. A small textbook appeared in 1901. He continued to work until a few months before his death in 1912, producing about 35 percent of his publications after the appearance of the last volume of the monograph in 1904.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 27 STATUS BOX 2-2 STEPHEN ALFRED FORBES (1844–1930) … [A] little world within itself—a microcosm within which all the elemental forces are at work and the play of life goes on in full but on so small a scale as to bring it easily within the mental grasp. This is how Stephen Forbes described the ecological dynamics of a lake in his often-cited 1887 paper "The Lake as a Microcosm." In this early essay, Forbes described the now familiar concept of the interdependence of living organisms and environmental factors. Owing much to Forbes' influence, the field of limnology developed a strong ecological perspective by the close of the nineteenth century. Born in 1844 in Silver Creek, Illinois, Forbes was raised on a farm with five siblings. At age 17, he joined the Union cavalry and served four years during the Civil War, including four months as a prisoner of war. After the war, he studied medicine, but within three years he turned to natural history. He attended Illinois State Normal University for a brief time but continued natural history studies on his own. In 1872, Forbes became curator of the Museum of the State Natural History Society in Normal, Illinois; in 1877, he transformed this institution into the Illinois State Laboratory of Natural History. In 1884, he moved with the laboratory and museum to Urbana, became a professor at the University of Illinois, and completed a Ph.D. from Indiana University. He was chief of the Illinois State Natural History Survey until his death in 1930. The limnological contributions of Forbes were diverse. He was among the first to study North American inland lakes (other than the Great Lakes). His studies of several lakes in the Rocky Mountains, published in 1893, represented for a number of years the sole biological information on lakes in the western United States. Forbes was an early and notable contributor to limnology of running waters as well; under his direction, the Illinois State Laboratory of Natural History established a floating laboratory on the Illinois River and conducted an extensive, half-century-long study of the river. In "The Lake as a Microcosm," Forbes fostered the idea that the organisms and dynamics of a water body are isolated from and independent of the landscape. Although today this concept has been supplemented by current understandings about the influence of the catchment basin and airshed, Forbes' cogent view contributed a significant organizing model. The notion of the lake as a microcosm (that is, an isolated, simplified, and understandable system) provided impetus and encouragement for scientists to study lakes from an "ecosystem" standpoint (even though the term ecosystem was not introduced until 1935). The lake as microcosm persists as a vital concept in limnology today. It has inspired studies at all scales, from whole lake to plastic pool and small aquarium, as limnologists have endeavored to understand the components, functions, and interactions of aquatic systems.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 28 STATUS BOX 2-3 EDWARD A. BIRGE (1851–1950), CHANCEY JUDAY (1871–1944), AND THE WISCONSIN SCHOOL OF LIMNOLOGY Birge and Juday are usually included among the founders of limnology. Their research contributed substantially to the basic understanding of a broad range of physical, chemical, and biological characteristics of lakes. They also assisted the development of the field through their roles in initiating a strong educational program and communications networks linking professional limnologists. Several books provide details of their lives (Sellery, 1956; Frey, 1963; Beckel, 1987). The contributions of Birge and Juday represent a microcosm of the interdisciplinary links that have been essential for progress in limnology. Both began their work with classic zoological studies on the taxonomy and distribution of a major component of lake planktonic communities, the cladocerans. They soon found, however, that little could be understood about the distribution of these animals in lakes without evaluating a range of physical and chemical properties. This led to investigations of water column thermal structure, distribution of dissolved gases, and light penetration, along with the mechanisms controlling these features. Several fundamental aspects of lakes that now comprise a basic component of most modern investigations derive from these efforts (Mortimer, 1956; Frey, 1963). The multidisciplinary effort needed to investigate lake properties led Birge and Juday to involve chemists, physicists, geologists, and other biologists in their research, and they interacted with other scientists in the developing field of limnology around the world. Initially, their work focused on individual lakes in southern Wisconsin. Later, they expanded their efforts at the Trout Lake Limnological Station in northern Wisconsin to compare and evaluate controlling features across a wide range of lake types. Their assessments of the interactions among physical, chemical, and biological processes in lakes helped to develop limnology as an ecosystem science. Substantial portions of the data Birge and Juday collected during their later years never were published, and these archived data remain a useful source of information for present-day limnologists. Edward A. Birge obtained A.B. and A.M. degrees from Williams College in Massachusetts and a Ph.D. from Harvard. He began his career at the University of Wisconsin in 1875 and remained there for the rest of his life. During his career, he assumed a variety of administrative positions, including president of the university. He also directed the Wisconsin Geological and Natural History Survey, through which he fostered the collection of extensive limnological data. Despite his administrative responsibilities, he maintained his interest in aquatic research, continuing to work at the Trout Lake Station even at the age of 85. Robert Pennak, who completed his graduate work at Wisconsin and now is emeritus professor at the University of Colorado, relates a story of how Birge admonished him, after a Model A car they were using had been turned on its side by slippery road conditions," … dammit Pennak, put it back on its wheels, the survey must go on!" (Beckel, 1987). Chancey Juday arrived at Wisconsin in 1900 as a biologist for the Geological and Natural History Survey. He received A.B. and A.M. degrees from Indiana

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 29 STATUS University, where he was introduced to aquatic studies during a summer research program, and he was hired to work with Birge at a time when administrative duties were limiting Birge's research efforts. Juday continued at the Geological Survey during his career and served on the faculty of the University of Wisconsin and as director of the Trout Lake Limnological Station. He supervised the graduate training of 13 Ph.D.s, several of whom have made substantial contributions to limnology. Juday was instrumental in establishing the American Society of Limnology and Oceanography and was its first president. One of Juday's last Ph.D. students, Arthur D. Hasler, was hired by the University of Wisconsin to continue limnological activities. Hasler himself became a major figure in limnology, contributing substantially to the development of limnology as an experimental science (in contrast to its origins as an observational science). During his career at the University of Wisconsin (1940–1975), Hasler supervised the training of numerous M.S. and Ph.D. limnologists, including several who have attained international status in limnology and ecology. been broadened and refined as twentieth century science has become more sophisticated (see the background paper "Organizing Paradigms for the Study of Inland Aquatic Ecosystems" at the end of this report). Today, limnological studies focus on lakes as "mirror images of the landscape around them" (A.D. Hasler, quoted in Beckel, 1987)—in other words, as open systems that receive inputs of water, solar energy, and chemical substances from terrestrial and atmospheric sources. Limnology began to take its place as a recognized field for research and scholarly activities near the turn of the century. The first limnological research institute in Germany was founded at Plön in 1891; it still is one of the major centers for limnological research (Overbeck, 1989). Edward Birge and his colleague Chancey Juday (see Box 2-3), usually regarded as the founders of academic limnology in North America, began their limnological studies at about the same time. Both spent their careers at the University of Wisconsin in Madison, and they began a rich limnological tradition that continues at that university to the present (Mortimer, 1956; Frey, 1963; Beckel, 1987; Kitchell, 1992). Birge was a zoologist and was attracted to lake studies during his student days in the 1870s in the context of the life cycles of microscopic animals (zooplankton). Juday also was trained as a biologist and was hired by Birge in 1897 to help conduct lake surveys. Birge and Juday soon branched into the physics and chemistry of lakes as they realized that the dynamics of plankton could not be understood without knowledge of these subjects. Their studies on temperature stratification and dissolved gases provided limnologists with information needed to understand virtually all biological cycles in lakes. Birge and Juday sought collaboration with physicists and chemists to study

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 30 STATUS lake phenomena beyond their own field of expertise. Together, these scientists developed many new techniques to measure physical properties and processes and many chemical characteristics of lakes. REGIONAL AND DESCRIPTIVE ERA Limnology continued to develop as a field of study and expand its geographic base during the first half of the twentieth century. Limnologists of the 1920s and 1930s founded many field stations, used them to collect a wealth of information on individual lakes, and synthesized this information at the regional scale. As practiced during these decades, limnology was essentially an observational science: knowledge gained was largely from sample collection and analysis of the resulting data rather than from Edward Birge and Chancey Juday with plankton trap on Lake Mendota in Madison, Wisconsin, circa 1917. SOURCE: State Historical Society of Wisconsin, Visual and Sound Archives.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 31 STATUS controlled experiments. This regional/descriptive approach reflected the pervading notion of lakes as microcosms in that studies on individual lakes usually were multidisciplinary: physical, chemical, and biological measurements were included in most studies, reflecting at least implicitly the idea that lakes are complex organized systems. Efforts at the regional scale during this period also focused on classifying lakes into major types based on a multidimensional set of descriptors. For example, the scheme that classifies lakes according to trophic state (meaning general nutritional status) was developed by August Thienemann and Einar Naumann (see Box 2-4) in the 1920s. According to this scheme, an array of indicators—including a physical measure (transparency), chemical concentrations (of nutrients), and biological characteristics (species types and abundance and primary production)—was used to classify lakes according to their overall nutritional status and productivity. These and other classification efforts provided an impetus for integration and synthesis, leading to generalizations about lakes as ecosystems. In 1922, the international limnology society, Societas Internationalis Limnologiae (SIL), known in English as the International Association for Theoretical and Applied Limnology, was founded in Germany under the aegis of Thienemann and Naumann. Limnologists in the United States were organized as the Committee on Aquaculture in 1925 and as the Limnological Society of America in 1936. From a starting base of 221 members in 1936, the American society grew to include 4,000 scientists today. It joined with oceanographers to become the American Society of Limnology and Oceanography in 1948; its journal, Limnology and Oceanography, one of the premier research periodicals on lake limnology in the world, was launched in 1955. MIDCENTURY EXPANSION Most major universities in North America and Europe had hired limnology professors by the middle of the twentieth century. In almost all cases, these faculty were in departments of biological science (including zoology and botany as well as biology), and the field developed a distinct biological focus. With few exceptions, limnology programs in universities were staffed by one faculty member, and the success of the program rose or fell with the intellectual ability and initiative of that individual. In contrast, natural sciences that are related more directly to resource utilization and economic production (such as forestry, soil science, and fisheries and wildlife) typically developed academic programs with larger and more diverse faculties. Thus, their long-term success was less dependent on that of a single individual. G. Evelyn Hutchinson, who spent most of his career at Yale University, was a dominant figure in North American limnology during the middle

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 32 STATUS BOX 2-4 AUGUST THIENEMANN (1882–1960) AND EINAR NAUMANN (1891–1934) August Thienemann dominated the development of comparative limnology in Europe for much of the first half of this century. With strong zoological interests, Thienemann conducted detailed analyses of numerous lakes of different geomorphological, chemical, and biotic characteristics. By induction from these analyses, he synthesized common functional relationships in lake typology that were essential to the young discipline and stimulated extensive further studies throughout the world. Born in 1882 in Thüringen, Germany, Thienemann began his studies in 1901, primarily in botany and later in zoology and philosophy, at the Universities of Greifswald, Innsbruck, and Heidelberg. He initiated extensive research programs while holding positions in zoology at the Universities of Greifswald and Münster. Between 1910 and 1914, he conducted studies on the volcanic Eifel Maar lakes, which provided the basis for his organization of lakes in terms of bottom-dwelling invertebrate communities and their relationships to chemical conditions, in particular the oxygen content, of bottom waters of lakes. In 1917, Thienemann, then associate professor of hydrobiology at the University of Kiel, became director of the Hydrobiologische Anstalt der Kaiser-Wilhelm- Gesellschaft in Plön, which up to that time had been operated as a private biological station since its founding by another pioneering limnologist, Otto Zacharias, in 1891. Under Thienemann's leadership, the hydrobiological station became one of the foremost limnological research and advanced educational institutions of Europe. That foundation of limnological excellence has continued to the present as the Max-Planck- Institut für Limnologie—among the leading experimental limnological research facilities of the world. Thienemann conducted pioneering studies in many places and on many topics. For example, he led limnological expeditions to remote tropical areas such as Java. He developed ecosystem concepts in the 1920s that influenced subsequent conceptual developments by Hutchinson and Lindeman (see Boxes 2-5 and 2-6). A tireless student of limnology, he authored nearly 500 publications and 25 books. Thienemann collaborated in the early 1920s on lake typology and regional limnology with the Swedish limnologist Einar Naumann, who was an assistant professor of botany and later the first professor of limnology at the University of Lund, Sweden. Naumann's research on phytoplankton distribution and sediment formation in relation to nutrient conditions in lakes complemented the zoological interests of Thienemann. Despite highly disparate viewpoints, the two men developed a general system of classifying lakes that persists to this day. In 1921, Naumann and Thienemann founded the International Association of Theoretical and Applied Limnology (Societas Internationalis Limnologiae), drafted its statutes, and organized the first international congress of limnology in 1922. Their leadership guided this organization during its early development; it subsequently has evolved into a global association that provides its more than 3,000 members in 80 countries opportunities to exchange limnological information.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 33 STATUS third of the century and a leader in the development of ecology in general (see Box 2-5). A man of wide-ranging interests and enormous intellect and insight, he brought a theoretical approach to aquatic ecology to complement its empirical underpinnings (Lewis et al., 1995). He attracted outstanding students to his program, many of whom developed prominent academic programs and had influential careers of their own. Some of Hutchinson's students eventually developed entirely new subdisciplines within ecology (see Box 2-6). BOX 2-5 G. EVELYN HUTCHINSON (1903–1991) In 1979, G. Evelyn Hutchinson joined the eminent select, such as Einstein, Edison, and Max Planck, by being awarded the Franklin Medal "for developing the scientific basis of ecology." The most voluminous scientific contributions of Hutchinson were in the biogeochemistry of lake ecosystems and included a monumental treatise on limnology (in four volumes) that demonstrated his remarkable abilities to interpret and synthesize disparate information into meaningful concepts. These scientific foundations in biogeochemistry (and population dynamics) led to major contributions in evolutionary ecology. His development of the ecological concept of multidimensional niches is a most fundamental scientific contribution. Several of his former students have led the subsequent development of ecology as a discipline. He was generous in sharing his conceptual advances with colleagues, such as in his work with Raymond Lindeman on trophic food web relationships (see Box 2-6). Hutchinson's propensity for natural history was nurtured in Cambridge, England, in a stimulating intellectual environment. After undergraduate studies at Cambridge University and brief research positions at the Stazione Zoologica in Naples and the University of Witwatersrand in South Africa, Hutchinson accepted an instructorship in zoology at Yale University in 1928. He spent the remainder of his career at Yale, continuing years of high productivity after his official retirement in 1971. In addition to teaching in natural history, ecology, limnology, and biogeochemistry, he developed a research program of enormous breadth. He made seminal contributions to knowledge of processes in lake bottom waters and sediments, oxygen deficits, benthic invertebrates, paleolimnology, and biogeochemical cycling, especially of phosphorus. He was a pioneer in the development of innovative experimental techniques, using radioisotopes of phosphorus in lakes as early as the 1940s and bioassays of nutrient effects on phytoplankton population dynamics as early as 1941. Hutchinson had penetrating understanding of many fields of science. He contributed significantly to geochemistry, oceanography, anthropology, paleontology, sociology, and behavioral sciences, as well as to his primary research areas in biogeochemistry and limnology. He received numerous national and international awards in science, and as the foremost ecologist and limnologist of the twentieth century, he left a substantial legacy in his scientific writings and the students he trained.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 34 STATUS BOX 2-6 RAYMOND L. LINDEMAN (1915–1942) AND H. T. ODUM (1924–): EXAMPLES OF THE INTELLECTUAL LEGACY OF G. E. HUTCHINSON Raymond Lindeman was a young aquatic ecologist who developed an important concept for synthesizing ecological principles based on energy flow through food chains. His trophic-dynamic concept, published posthumously in 1942, emphasized the importance of short-term nutritional functioning to an understanding of long-term changes in the dynamics of lake communities. Drawing from conceptual works of the plant ecologist Tansley and the limnologists Thienemann and Hutchinson, Lindeman showed how organic and inorganic cycles of nutrients are integrated. His theoretical model of nutrient cycling, expressed in terms of energy flow, allowed evaluations of biological and ecological efficiencies of energy transfer over long periods. Lindeman did his graduate studies in zoology at the University of Minnesota under Samuel Eddy and W. S. Cooper. His doctoral research involved a detailed evaluation of trophic (food web) structure in Cedar Bog Lake and provided support for the general tenets of trophic-dynamic concepts. In 1941, Lindeman began postdoctoral studies at Yale University with G. E. Hutchinson. Many of Lindeman's trophic-dynamic ideas were melded into conceptual and mathematical treatments from Hutchinson's then-unpublished writings. The combined efforts of these two scientists led to many major conceptual breakthroughs. Hutchinson also assisted with the publication of Lindeman's synthesis paper (Lindeman, 1942), which was rejected at first because of its theoretical nature. Trophic dynamics and ecosystem concepts are so embedded in modern ecology that it is difficult to comprehend how revolutionary his theoretical model was at the time. The paper provided much of the intellectual framework on which subsequent development of ecosystem ecology was based. Lindeman died prematurely in 1942 at age 27. Howard Thomas Odum, known as H. T. or Tom, is a major figure of modern aquatic ecology whose influence extends beyond the confines of traditional ecology. His innovations spurred the development of several new disciplines—in particular, systems ecology, ecological economics, and ecological engineering—that relate ecology to other sciences in analyzing major environmental problems. Odum was born in Durham, North Carolina, the son of Howard W. Odum, a renowned sociologist at the University of North Carolina. He received an A.B. in zoology in 1947 from that institution and a Ph.D. in 1951 under G. E. Hutchinson at Yale University. His career was spent at several academic institutions, including the University of Florida, where he is now professor emeritus. His work on the energetics of Silver Springs, Florida (Odum, 1957), is a landmark whose impact on flowing water ecosystems is analogous to the impacts of Lindeman's trophic-dynamic work on lakes. He advanced experimental ecology through work on mesocosms and by refining the diurnal oxygen method for measuring primary production. He directed several large- scale experiments in a tropical rain forest in Puerto Rico (Odum and Pigeon, 1970) that were classic examples in forest ecology and the assessment of how radionuclides

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 35 STATUS affect ecological processes. During the past 25 years, his work in aquatic ecology has focused on experimental wetland ecology, including the use of wetlands as natural treatment systems for wastewaters. Odum has authored or coauthored several books that have significantly influenced ecology and related fields. He contributed to the classic ecology text written by his brother, Eugene Odum, also a major figure in ecology in the second half of this century. H. T. Odum's first book, Environment Power and Society (1970), presented a computer language and modeling technique to describe energy flow through ecosystems. The language and modeling approach became the tool of a group of followers who modeled energy flows associated with the movement of commodities in both natural ecosystems and human-dominated systems. This work led to the concept of "embodied energy," since termed "emergy," which accounts for the direct and indirect energy flows (those from "free environmental services" and those supplied by the economy) required to produce a substance. In turn, this led to efforts to conduct economic analyses in terms of energy units. Odum coined the term ecological engineering in 1962, and he has contributed much to its development as a field distinct from but related to environmental engineering (Mitsch, 1994). He continues to promote the development of university curricula to produce ecological engineers (Odum, 1994). Odum has received many awards, including the Mercer Award of the Ecological Society of America; the AIBS (American Institute of Biological Science) Distinguished Service Award; the Prize of the Institut de la Vie, Paris; and the Crafoord Prize of the Swedish Academy of Sciences. The last two prizes were shared by the two distinguished brothers, H. T. and Eugene. Experimental Limnology Experimental lake limnology has involved at least three types of manipulations: (1) stress-response experiments, in which a lake (or a basin in a lake) is treated with a chemical or biological stressor (such as excess nutrients, acid, or a top predator) and the responses of the lake system are studied; (2) hydrologic, physical, chemical, and/or biological manipulations aimed at lake remediation or rehabilitation; and (3) tracer additions to measure rates of physical processes, such as use of radiotracers to follow water movement and noble gases to monitor air-water-gas exchange. Most lake manipulations of the first type employ the modern, expanded concept of the lake as a microcosm in that their aim is to apply a stress to an ecosystem and observe the changes that it causes in various properties of the ecosystem. (Preferably, these properties are measured for a given number of years before the stress is applied, and the experiment continues for several years and includes a recovery phase following the removal of the stress.) Limnologists conducting these experiments typically have studied a wide range of responses—from changes in chemical concentrations

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 36 STATUS to changes in individual organisms, populations, communities, and ecosystem- level processes (Schindler et al., 1992; Brezonik et al., 1993). Raymond Lindeman, year and photographer unknown. SOURCE: Eville Gorham, University of Minnesota. The idea that whole lakes can serve as subjects for experimental manipulation developed slowly, beginning in the late 1930s and 1940s. Juday was the first to conduct an experiment on a whole lake. During the mid-1930s, he added various fertilizers to a small pond in northern Wisconsin to study their effects on plankton production and fish populations (Juday and Schloemer, 1938). Einsele (1941) performed a similar experiment on a small lake in northern Germany a few years later. Neither of these manipulations had much immediate impact on the development of experimental limnology, perhaps because of the disruptive influence of World War II on natural science. Whole- lake experiments by Arthur Hasler and his group at the University of Wisconsin in the 1950s and 1960s were more influential in establishing the usefulness of this approach (see the background paper ''Organizing Paradigms for the Study of Inland Aquatic Ecosystems" at the end of this report). Experimental limnology did not play a prominent role in lake science until the late 1960s and 1970s, probably because of the lack of funding to support such complicated and expensive initiatives. Widespread concern about excessive nutrient enrichment (eutrophication) of lakes led to government research programs in industrialized countries during the 1960s,

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 37 STATUS and these programs facilitated wider use of experimental approaches in lake limnology. Even so, large-scale experiments (such as whole-lake manipulations) have been relatively few in number because of their comparatively high cost, the long time (at least several years) required to complete them, and the limited availability of lakes that can be dedicated to such purposes. Consequently, experimental approaches at smaller scales using enclosures of one to a few meters in diameter—often called mesocosms, limnocorrals, limnoenclosures, or limnotubes—that are installed in the lake have become popular in Europe and North America. This intermediate scale has enabled limnologists to complete a great variety of experiments, under conditions that can be controlled and replicated, on systems more similar in complexity to whole-lakes than one can achieve in laboratory-scale systems. Nonetheless, mesocosms cannot duplicate the complicated ecosystems of whole- lakes and are especially inadequate to study populations of large fish over long periods. Because manipulations of whole aquatic ecosystems generally cannot be duplicated, limnologists have focused considerable effort over the past decade on developing sophisticated statistical methods and other techniques to evaluate data from such unreplicated experiments (Carpenter et al., 1989; Rasmussen et al., 1993). Of special importance is the gathering of adequate baseline data prior to manipulation. Paleolimnological techniques (described later in this chapter) also can help to carry such baseline information backward in time. Despite the difficulties involved in conducting and interpreting whole-lake experiments, a strong consensus has developed among limnologists that observing responses to manipulations made at the whole-system level is a highly useful technique. Whole-lake experiments conducted over the past 30 years have been important both in advancing the understanding of fundamental limnological processes and in providing critical evidence for the management or solution of major pollution issues such as eutrophication and acidification. Their strengths for both purposes lie in their ability to test hypotheses and to provide a "platform" for related laboratory or field experiments at a range of scales. Paleolimnology During the middle of this century, the field of paleolimnology (see Box 2-7) developed into one of the key subdisciplines of limnology. Paleolimnology, closely related to paleoecology and paleoclimatology, has its origin in early nineteenth century botanical and chemical studies on peat cores and late nineteenth century geological studies on lithified sediments of ancient lake beds. By the early 1920s, limnologists had begun to collect sediment cores from lakes and to interpret stratigraphic data on plant and animal fossils as a record of the lake's history. Nipkow (1920) was

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 38 STATUS A whole-lake experiment to investigate the causes of eutrophication. SOURCE: David Schindler, University of Alberta. the first to observe and explain the existence of thinly laminated sediments. He showed that laminae result, in some lakes, from an annual depositional cycle in which photosynthesis during warm months causes precipitation of calcium carbonate, which settles and forms a thin light layer on the sediments. Deposition of organic matter during the rest of the year forms a dark layer on top of the calcium carbonate; other mechanisms also

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 39 STATUS BOX 2-7 PALEOLIMNOLOGY: THE LIMNOLOGIST'S ARCHAEOLOGY Lake and wetland sediments contain detailed archaeological records of how natural events and human activities have affected the overlying ecosystems—records revealed through "paleolimnology." Paleolimnology is in many ways analogous to the reconstruction of past civilizations by examining their stratified remains, a well-known technique in archaeology. Paleolimnological data are important in providing baselines against which to assess the damage done by activities such as land clearance, drainage, water pollution, and air pollution. They are also useful in assessing the rate of recovery from such damage when the cause has been mitigated or brought to an end. Lake sediments and wetland peat deposits form a selective trap for a variety of plant and animal remains and elements, such as carbon, phosphorus, sulfur, iron, and manganese that are stored at varying concentrations depending on the activities that were occurring at the time the sediment layer was formed. Changes in the sedimentary profile inevitably record a good deal of lake and peatland history as well as the history of the surrounding catchment. Following are three examples of paleolimnological studies: 1. At Shagawa Lake in northeastern Minnesota, paleolimnology has been used to trace the history of human development along the lakeshore (Bradbury and Megard, 1972; Bradbury and Waddington, 1973; Gorham and Sanger, 1976). Analyses of a 1- meter sediment core taken in 6.5 meters of water reveal striking changes in the flora, fauna, and chemistry of the lake following human settlement in its catchment, which began in the late 1880s. Settlement is clearly marked in the sediments by rapidly increasing concentrations of hematite grains from the dewatering of iron mines, which led to the founding of the town of Ely on the southern shore of the lake. The town's population grew to about 6,000 people in 1930, after which it decreased somewhat as mining declined; decreases in hematite grains in the sediments follow the decrease in mining activity. Settlement is also marked by a rise in the concentration of ragweed pollen that is typical of land clearance and the replacement of forest s by agricultural fields. Also reflecting human activities in the catchment are marked shifts in the depth profiles of different types of siliceous diatom shells (frustules) in the sediments. The cause of these changes was severe nutrient enrichment due to discharge of the town's sewage directly into the lake. Most notably, Stephanodiscus minutus, Fragilaria crotenensis, and F. capucina, all characteristic of lakes in more fertile regions, increased greatly in abundance after settlement, while Cyclotella comta and several other species characteristic of the absence of pollution and lower nutrient concentrations declined and disappeared. 2. Paleolimnologists have used the Red Lake Peatland in northwestern Minnesota to develop tools for documenting the occurrence of acid rain and global warming (Gorham and Janssens, 1992; Janssens et al., 1992). The peat deposit contains a diverse array of fossil mosses whose environmental tolerances can be inferred from those of modern mosses at other sites in order to reconstruct pH and water table changes in the bog over time. Figure 2-1 shows profiles for two cores from a particular bog "island" in the Red Lake Peatland,

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 40 STATUS one (RLP8112) from its center and the other (RLP8104) from its periphery. The site at the center of the island (RLP8112) began to accumulate peat with a pH close to 7 about 3,300 years ago. About 1,100 years later the fen began to be invaded by Sphagnum mosses, which in less than three centuries transformed it into an acid bog with a pH close to 4. This change was accompanied by a lowering of the water table relative to the peat surface. The site at the margin of the present bog (RLP8104) exhibits very different depth profiles: drier, acid bog conditions alternated with wetter, near-neutral conditions, presumably as a result of island expansion and contraction in response to differing degrees of ground water upwelling. The utility of such depth-time profiles as baselines for assessing the effects of human disturbance lies in the boundaries they set. For example, if acid deposition were to lower the pH of the bog surface substantially, we should expect to see the development of moss assemblages characteristic of much more acid conditions and distinctly different from any of the assemblages observed in these peat cores over the past three millennia. Similarly, if global warming were to lower the bog water table significantly, we should expect to see moss assemblages characteristic of drier conditions and quite different from those observed at any time since peat began to accumulate. 3. By analyzing the pH preferences of individual species of diatoms and chrysophytes, paleolimnologists can calculate the past pH of a lake from the composition of diatom and/or chrysophyte remains at various dated strata in the lake's sediments (e.g., Smol et al., 1984a,b; Charles et al., 1989; Cumming and Smol, 1993; Cumming et al., 1994). The pH preferences for these species are evaluated by examining their remains in surface sediments from numerous lakes spanning a broad range of pH, and transfer functions are derived from modern data by multivariate statistical methods for extrapolating the data to past periods. Using such techniques, Cumming et al. (1994) showed that of 20 acid-sensitive lakes examined in Adirondack Park, approximately 80 percent have acidified since preindustrial times. This information refutes the contention of some that lakes in the Adirondacks are naturally acidic. Lakes that became acidic around 1900 generally were smaller, higher-elevation lakes with lower preindustrial pH values than the lakes that did not acidify or acidified more recently. Post-1970 pH trends in the lakes have been small and variable, suggesting that the lakes have been unresponsive to post-1970 declines in sulfate deposition. can produce annual laminae in some lakes. These annual laminae allow limnologists to count back in time and to date individual strata of a sediment core. By studying plant and animal microfossil remains (such as pollen, diatom shells, and remains of zooplankton bodies) in laminae and by knowing the environmental tolerances of modern assemblages of the organisms being fossilized, paleolimnologists can reconstruct historical conditions in a lake and/ or its drainage basin (see Box 2-7). Relatively few lakes deposit clearly laminated sediments, however,

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 41 STATUS FIGURE 2-1 Depth-time profiles from the Red Lake Peatland. The profiles show the changes in pH and the height of the peat surface above the mean water table (HMWT) over the past 3,300 years in two peat cores, designated RLP8112 and RLP8104. SOURCE: Reprinted, with permission, from Gorham and Janssens (1992). © 1992 by Suo. and consequently the application of paleolimnology was limited until radioisotope dating methods were developed in the 1950s and 1960s. The tools of paleolimnology include "radiochronometers," which use radioisotopes such as carbon-14 and lead-210 to date the time a sediment stratum was deposited; pollen, which indicates what types of terrestrial vegetation were present; various plant and animal fossil remains, including cell fragments and molecules such as plant pigments, which provide further clues about vegetation and aquatic life; and organic pollutants and trace elements, whose biogeochemical cycles have been influenced by human activity. Over the past 30 years, analyses of the layers in long sediment cores from lakes and wetlands have provided information about regional variations in past climatic conditions and watershed vegetation patterns, from which paleoecologists have sought to answer questions about the causes of environmental change. Paleolimnological studies on more recently deposited lake sediments have provided evidence for the timing and causes of lake pollution, including information about the

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 42 STATUS effects of excess nutrient inputs to lakes and about atmospheric transport of various pollutants. Sediment core being taken through a frozen lake for a paleolimnological analysis. SOURCE: Thomas M. Frost, University of Wisconsin, Trout Lake Station. RECENT HISTORY Since the early 1960s, limnology in North America has been characterized by four related trends:

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 43 STATUS 1. increasing emphasis on research related to the effects of pollution on aquatic resources and on ways to restore and manage these resources; 2. increasing diversity in the disciplinary backgrounds of limnologists; 3. increasing variety in the types of lakes studied; and 4. increasing focus on other types of inland aquatic ecosystems (streams, wetlands, and reservoirs), broadening the field of limnology from its traditional focus on natural lakes. Research Driven by Pollution Concerns Public concern about declining water quality and impaired ecological conditions in many aquatic resources caused by various human activities has resulted in greatly increased public expenditures for limnological studies in North America since the 1960s. Much of this funding has been associated with two major pollution problems: eutrophication and acid deposition, both of which generated large government-sponsored research programs for approximately 15-year periods (early 1960s to mid-1970s for eutrophication; late 1970s to early 1990s for acid deposition). A substantial portion of this research support was supplied by mission-oriented agencies such as the Environmental Protection Agency rather than by basic science agencies such as the National Science Foundation. These large programs, although criticized by some scientists as inefficient (Roberts, 1987), resulted in significant practical advances. They defined the nature and extent of the problems, quantified sources of pollution, developed relationships for determining the responses of water bodies to various levels of pollution, and identified a variety of control and restoration measures. Beyond these practical results, the research supported or otherwise stimulated by these initiatives produced many conceptual advances and much new fundamental information about limnological processes, as well as advances or refinements in field and laboratory techniques. For example, eutrophication-related research led to improved understanding of aquatic food web interactions and to conceptual advances regarding the factors that control material and energy flows through aquatic food chains and webs. Similarly, research stimulated by concerns about lake acidification led to greatly improved understanding of the chemical and microbial processes affecting alkalinity and acid-base balances in dilute lake waters, new information about the biogeochemical cycling of sulfur in such systems, and advances in the understanding of mineral weathering rates. Acidification research also helped foster the development of techniques to understand the natural variability of ecosystems as a benchmark against which to measure the effects of human-caused stress. Both problems led to substantial advances in the ability to describe lake ecosystem processes mathematically and to develop predictive models of these systems. Finally, both led to improved understanding

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 44 STATUS of the role of sediment-water interactions in the cycling of elements in lakes and in the control of water column conditions. Diversification of Disciplines Participating in Limnological Research The focus of limnology on chemical pollutants over the past quarter century helped to attract greater numbers of scientists from disciplines other than biology into the field. For example, environmental aquatic chemistry, a field that has developed its own identity primarily since the early 1960s, has close ties with limnology; many water chemists work essentially as chemical limnologists and focus their expertise on developing a more complete understanding of the behavior of natural chemicals, such as nutrients and acids, and synthetic chemicals, such as pesticides and various chlorinated compounds, in inland aquatic ecosystems. Similarly, other physical scientists and environmental and hydraulic engineers brought their analytical skills and mathematical modeling techniques into limnology as a result of the opportunities provided by government research programs on eutrophication and acid rain. In most academic situations, individuals from these other disciplines have maintained their disciplinary identity and are not directly associated with traditional limnology programs in departments of biological science. Scientists who carry out studies related to limnology today operate from departments as diverse as civil engineering, fisheries and wildlife, botany, zoology, ecology, environmental science, forestry, geology, and geography. For example, in a survey conducted for this report, 42 of 69 universities housed professors who teach limnology-related courses in biology departments and 32 housed them in civil and environmental engineering departments, but these schools also listed 21 other types of departments in which limnologists and related aquatic scientists teach and do research (see Table 2-1). Some scientists in civil engineering, fisheries, environmental science, and other departments listed in Table 2-1 call themselves limnologists, whereas others study components of aquatic ecosystems but do not necessarily identify with the field of limnology. Although the interdisciplinary nature of limnology is one of its important assets, it has created difficulties in organizing and sustaining the infrastructure needed to conduct the science. Most universities have no single "home" for limnologists, and limnological studies are scattered among several departments at major research universities. Typically, the individual programs are small and focus on only one or a few aspects of limnology. Levels of departmental support vary depending on the perceived importance of those aspects to the parent discipline of the department.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 45 STATUS TABLE 2-1 Departments Housing Faculty Working in Limnology and Related Aquatic Sciences Department Number of Schools Agriculture/soil science 6 Biology 42 Botany 12 Chemistry 3 Civil/environmental engineering 32 Ecology 6 Entomology 9 Environmental science/studies 10 Fisheries 17 Forestry 10 Geography 3 Geology/geophysics/geoscience 18 Hydrology 4 Landscape architecture 1 Life science 2 Marine science and limnology 1 Natural resources 9 Oceanography 3 Public health 2 Rangeland management 3 Urban and regional planning 1 Zoology 15 Zoology and limnology 1 SOURCE: This table was complied from surveys of 69 universities belonging to the Universities Council on Water Resources and/or housing a U.S. Geological Survey Water Resources Research Institute (see Appendix A). Limnology Beyond Small Temperate Lakes The third major limnological trend of the past quarter century is a diversification of the types of aquatic systems to which limnologists have directed their attention. Most lake limnologists through the first part of the century focused on relatively small lakes in temperate latitudes—reflecting the latitudes of the industrialized countries where limnology developed. Limnologists have always liked to travel and study lakes in exotic places. As long ago as 1910, Juday traveled to Central America and sampled lakes in Guatemala and El Salvador (Juday, 1915). Thienemann conducted limnological studies in Indonesia in 1928 (Thienemann, 1931), and European limnologists have had long-term research programs in various tropical regions for many decades. Nevertheless, the number and intensity of such tropical studies were quite limited until the development of high-speed, low-cost air travel made the world seem smaller and more

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 46 STATUS interconnected. North American limnologists now have significant research programs in tropical latitudes (such as the Rift Valley lakes in equatorial Africa), the high Arctic, and even in Antarctica. In recent decades, lake research also has expanded to include the large, multipurpose reservoirs that have been constructed in regions of the United States (such as the mid-Atlantic states and arid West) where natural lakes are rare. The differences between reservoirs and natural lakes generally are a matter of degree rather than kind, and the same organizing principles and research techniques apply to both. Nonetheless, reservoirs often present special management problems. For example, the relationships between nutrient concentrations and chlorophyll levels are significantly different in lakes and reservoirs because the latter systems generally have much higher levels of inorganic turbidity (which limits light penetration and primary production) than do natural lakes. Consequently, nutrient loading criteria developed for lakes (to prevent or limit eutrophication problems) may not be directly applicable to reservoirs. Lake research in North America during the past few decades has also expanded to the Great Lakes. In spite of their vast economic and ecological importance, limnological studies on these lakes were extremely limited before about 1960, but concern about pollution and declining water quality in the lakes stimulated Canadian and U.S. monitoring and research programs. Several government agencies and universities in both countries have significant research programs on the limnology of the Great Lakes. Relative to their size and importance, these lakes are still understudied, at least in part because of the high costs and large research infrastructure required for studying them. In some ways, Great Lakes limnological research has more in common with oceanographic research, and it is no accident that the major U.S. funding agency for university research on the Great Lakes, the Sea Grant program, is primarily a marine research program. Stream Limnology Over the past two to three decades, stream science has developed the integrative approach characteristic of limnological studies on lakes. Until relatively recently, the physical, chemical, and biological components of stream limnology were independent subdisciplines that were associated more with parent basic science disciplines than with a discipline called stream limnology (see Box 2-8). For example, physical studies on water flow in streams were associated with the fields of hydrology and hydraulics, typically taught in engineering and geoscience departments. Similarly, the origin and development of stream channels and drainage networks is a topic in the field of geomorphology, which is a subdiscipline of geography and geology. Until recently, chemical studies on flowing

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 47 STATUS BOX 2-8 RUTH PATRICK (1907–) Ruth Patrick was a pioneer in predicting ecosystem risk well before these words were commonly used. She began her innovative studies of stream pollution in 1948 as curator of limnology at the Academy of Natural Sciences in Philadelphia. At that time, most pollution assessments were carried out by sanitary engineers (now called environmental engineers). The prevailing view was that if river water met certain chemical and physical conditions, particularly related to dissolved oxygen and pH, there was little need to examine the biota. Patrick was one of the first to consider how pollutants might affect the organisms that inhabit streams. Patrick spent much time persuading water pollution professionals in engineering that biological information was useful in determining ecosystem conditions. Most biologists were not especially interested in environmental pollution in those days—a fact now hard to comprehend—and the assessment and prediction of ecological risk went by default to those involved with water supply and wastewater treatment (predominantly sanitary engineers). In a pioneering survey of the Conestoga River basin in Pennsylvania, Patrick demonstrated that aquatic community structure was changed dramatically not only by pollution from human sewage but also by industrial pollution. Moreover, she demonstrated that there was a pattern in how aquatic communities respond to pollution that transcends the particular organisms present in any given stream. She tested her theories about the structure of aquatic communities in pristine environments during an expedition to the Amazon, which she led in 1955. Patrick stands out not only for her important scientific findings but also for her contributions to the way science is carried out. She was a scientist when women scientists were exceedingly uncommon, a leader in developing the scientific team approach to problem solving when ''lone-wolf" scientific specialists were dominant, a pioneer in the systems approach of looking at entire drainage basins, and perhaps most important, living proof that theoretical and applied science not only can coexist but are commonly synergistic. Acknowledgment of her many contributions was a long time in coming, but at age 63, Patrick began to receive wide recognition for her work. She was elected to the National Academy of Sciences in 1970 and received the prestigious Tyler Ecology Award in 1975. She also has received awards from the Botanical Society of America, Ecological Society of America, American Water Resources Association, American Academy of Arts and Sciences, and Society of Environmental Toxicology and Chemistry. She has received honorary degrees from two dozen schools and in 1972 was appointed to the board of directors of E. I. du Pont de Nemours and Company— the first woman board member. Patrick was born in Topeka, Kansas, in 1907. She developed an interest in microbiology at a young age when her father, an attorney, let her look through his microscope. She received a B.S. from Coker College in 1929 and a Ph.D. in botany in 1934 from the University of Virginia. In 1939, after a brief term at Temple University, she joined the Academy of Natural Sciences, where today she is Francis Boyer Chair of Limnology and senior curator. SOURCE: Adapted with permission from the dedication in Cairns et al. (1992).

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 48 STATUS waters were done primarily by geochemists, environmental engineers, and lake scientists interested in quantifying fluxes of minerals and pollutants from watersheds or into standing bodies of water (lakes and the oceans), and there was little interest in studying the chemical processes of streams and rivers themselves. Historically, stream science has been identified most strongly with stream biology and stream ecology. Stream biologists often are identified primarily with other parent disciplines such as public health microbiology, fisheries biology, and aquatic entomology. Stream biology was mostly descriptive through the first half of the twentieth century and focused on the distribution and taxonomy of stream organisms. The development of stream ecology or stream limnology as a discipline analogous to lake limnology grew out of initiatives that began in the 1950s and 1960s. Hynes' 1970 book The Ecology of Running Waters is usually regarded as the first book on stream ecology (see Box 2-9). The use of benthic invertebrates as indicator organisms for organic pollution and the division of streams into zones of pollution and recovery based on the presence of indicator species or groups of organisms have been major driving forces in stream biology since the early twentieth century; the first stream classification system based on the benthic organism species composition was the European "Saprobien" system of Kolkwitz and Marsson (1908, 1909). This paradigm stimulated much research on the structure of stream communities through the middle of this century. It can be considered a precursor of broader and more recent classification schemes and indices of biological integrity and biodiversity, which are currently popular subjects for research in stream ecology (see the background paper "Bringing Biology Back into Water Quality Assessments" at the end of this report). Stream scientists have developed several organizing principles in recent decades to integrate the separate physical, chemical, and biological disciplines that contribute to studies of streams as ecosystems. The River Continuum Concept (RCC) (Vannote et al., 1980) is the most important of these. The RCC describes river systems as a continuously integrated series of physical changes that cause adjustments in the associated biota (Cummins et al., 1995). Geomorphological and hydrological characteristics of rivers provide a fundamental physical template that changes in a predictable fashion from the headwaters to the river mouth. Biological communities develop in adaptation to the fundamental physical template. The concept thus has a watershed orientation and focuses on terrestrial and aquatic interactions. Since its development, the RCC has been modified in many ways to accommodate a broad range of factors, such as climate, geology, tributary effects, and local geomorphology, that influence streams. In addition, several organizing concepts developed as alternatives to the RCC have

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 49 STATUS been subsumed into a broader RCC. Examples include the nutrient spiraling concept (Newbold et al., 1981), in which the down-gradient flow of streams causes nutrient cycles to be open rather than closed, and the patch dynamics concept (Pringle et al., 1988), which is based on the idea that disturbance and variations in time are primary determinants of BOX 2-9 H. B. NOEL HYNES (1917–) Noel Hynes has been a major force in the development of the subdiscipline of limnology dealing with the study of flowing water ecosystems. His treatise The Ecology of Running Waters, published in 1970, summarized the knowledge of the field to that time on an international level and served as a foundation for modern stream ecology. An earlier book, The Biology of Polluted Waters, published in 1960, strongly influenced the development of biological assessments of water quality in streams. Hynes was born in Devizes, England. His formal training was in zoology and entomology; he earned B.Sc., Ph.D., and D.Sc. degrees from the University of London. Assignments as an entomologist during World War II took him to various locations in Africa, where he remained until 1946. Returning to England, he taught at the University of Liverpool until 1964. In 1964, he was awarded a professorship in biology at the University of Waterloo, Canada, where he remained until his retirement. Hynes specialized in the taxonomy and biology of freshwater Plecoptera and Amphipoda (invertebrate organisms that live in bottom sediments); their wide occurrence in flowing waters led him early to study stream ecology. His broad interests led to influential contributions in community ecology, trophic dynamics, and secondary production, and he was among the first to identify the importance of imported organic matter (allochthonous detritus) and the hyporheic zone (the interface between surface and ground water) in streams. His essay "The Stream and Its Valley," originally delivered to the International Association of Theoretical and Applied Limnology upon receipt of the association's prestigious Baldi Award, presaged the modern focus on watershed science in stream ecology. In 1984, Hynes received the Hilary Jolly Award from the Australian Limnological Society and, in 1988, was the recipient of the first Award of Excellence in Benthic Science from the North American Benthological Society. In all, Hynes has published more than 150 research articles, mainly on stream ecology. Hynes' career spanned the transition period between the eras of descriptive and experimental science in limnology, and his work reflected the best of both. His skill as a seasoned natural historian was superbly balanced against his brilliance and intuition as a scientist, and he often pointed out that much good science was still to be done with only a few simple devices, a keen eye, and a sharp mind. An astute critic and articulate spokesman, his painstaking reviews, polished presentations, and enthusiastic audience participation improved numerous journal articles and enlivened many scientific meetings.

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 50 STATUS community organization in streams. An outgrowth of the patch dynamics concept is the flood-pulse model (Junk et al., 1989), developed to describe biological communities in rivers that regularly overtop their banks and inundate the floodplain (Cummins et al., 1995) (see the background paper "Organizing Paradigms for the Study of Inland Aquatic Ecosystems" at the end of this report for further information on the RRC and its variants). The RCC is a very broad framework for describing flowing water ecosystems. It is sufficiently robust that it can accommodate many other organizing concepts to account for various physical factors or processes. Consequently, the RCC, like the microcosm concept for lakes, is likely to continue to be modified and expanded rather than abandoned or supplanted. Of course, there are many other organizing concepts for stream limnology. Many of them, such as the idea that streams can be used as experimental units, are similar to the organizing concepts for lake limnology (see the background paper "Organizing Paradigms for the Study of Inland Aquatic Ecosystems" for further examples). The concept of the watershed or catchment as the basic unit in stream hydrology dates back at least to the 1920s, and the watershed perspective has been used both in organizing hydrologic concepts and in data collection. More recently, the watershed concept has been used in an ecosystem context as a unifying theme to link both aquatic and terrestrial scientists (e.g., Likens and Bormann, 1974), and it was an organizing paradigm for the U.S. effort in the International Biological Program of the 1970s. Limnologists increasingly recognize that streams, lakes, and wetlands must be considered as interconnected systems in the context of their watersheds and airsheds. Wetland Ecology Integrated studies using the techniques of modern science to examine wetlands as ecosystems are primarily a phenomenon of the past 25 years (Mitsch and Gosselink, 1993), but the basic concepts on which wetland ecology is based can be traced back at least as far as the mid-sixteenth century (Gorham, 1953). Natural philosophers in the sixteenth and seventeenth centuries described and classified wetlands with names similar to those used today, and they related these classes to basic hydrologic conditions. The idea of wetland development and succession dates back to an account on Irish bogs published in 1685, and some fundamental ideas about the chemistry of bogs were developed in the late eighteenth and early nineteenth centuries. Nonetheless, most of these pioneering studies were overlooked by twentieth century botanists and ecologists as they developed similar concepts (Gorham, 1953). Throughout most of the nineteenth and twentieth centuries, wetlands were commonly regarded as wastelands or nuisances to be "reclaimed"

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 51 STATUS by draining or dredging, and this attitude hindered the development of wetland science (if for no other reason than financial—"wastelands" are unlikely to attract funds for research studies). The usefulness of wetlands in regulating hydrologic processes (see Box 2-10), such as floods, and in providing ecological benefits, such as buffering adjacent lakes and streams from impacts of upland human activity and serving as habitat for wildlife, has been widely recognized only in the past 25 years or so. With this recognition and the simultaneous understanding that human activities are causing wetlands to disappear at alarming rates came an impetus to study them, and the field of wetland ecology received a major stimulus. As scientific and public appreciation for wetland ecosystems has grown, there ironically also has been a trend to view them as useful in serving society's needs as natural analogues or extensions of engineered systems. Thus, a common view has developed that wetlands can be used as natural treatment systems. Research programs have been developed in association with academic institutions and water management agencies to study the effectiveness of wetlands in removing nutrients and other contaminants from domestic waste effluent or in purifying stormwater runoff before it reaches lakes and streams. Both natural and constructed wetlands now are being used for such purposes on a wide scale within the United States. For some proponents of this approach, the quality and ecological integrity of the wetland itself appear to be less important than its ability to perform the desired function. Nonetheless, studies done to support this approach have advanced the previously meager understanding of the ways in which wetland ecosystems function and have provided some basis for preserving wetlands that otherwise might be destroyed by drainage and urban or agricultural development. Many of the organizing and integrating principles on which wetland limnology is based are similar to those for lake and stream limnology, and a few scientists have combined interests in lakes and wetlands (see Box 2-11). However, some organizing concepts are linked primarily to wetlands. For example, wetlands can be considered as seres and ecotones—gradient ecosystems linking terrestrial and open-water aquatic systems and products of delicate, evolving interactions of hydrology and vegetation that produce unique, patterned landforms. Wetlands also are unique repositories of organic carbon (peat) and play an important role in the cycling of trace gases, including those implicated in global climate change (carbon dioxide and methane). Consequently, wetlands have become important ecosystems to study with regard to the global carbon cycle and global warming processes. CURRENT STATUS During the past few decades, limnological research has led to impressive conceptual and practical advances on all types of inland aquatic

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 52 STATUS BOX 2-10 KONSTANTIN E. IVANOV (1912–1994) Konstantin Ivanov led the investigation of peatland (mire) hydrology in the Soviet Union for several decades after World War II. This was a time when the field was little studied outside that country despite the primary importance of hydrology for peatland development. His pioneering studies received due attention outside the Soviet Union only after translation of his book Water Movement in Mirelands (Vodoobmen v bolotnyk landshaftakh) in 1981 by Arthur Thompson and H.A.P. Ingram. Ivanov was born in St. Petersburg and educated in hydraulic engineering. During World War II, he was called on to investigate the physical properties of ice and peat because they were important for military operations in the northern part of Russia. In 1944, Ivanov organized the first swamp station to study peatland hydrology. In 1948, Ivanov returned to Leningrad to head the State Hydrological Institute's Department of Peatland Hydrology, from which he directed permanent stations in peatland areas and led expeditions to other such areas. In 1949, he began to lecture at the University of Leningrad on peatland hydrology and other topics and was made professor in 1957. In 1963, he was appointed deputy scientific director at the State Hydrological Institute. In 1969, he joined the faculty of geography in the University of Leningrad and became full- time head of the Department of Land Hydrology. Ivanov was elected vice-president of the International Association of Hydrological Sciences and headed the Hydrological Commission of the Russian Geographic Society. Ivanov's early investigations of water storage in and runoff from peatlands led him to collaborate with Vladimir V. Romanov in developing an earlier concept of V. D. Lpatin that peatlands can be divided fundamentally into two layers: an upper acrotelm that is aerated at least part of the time and in which most biological activity takes place lying above a deeper catotelm that is permanently waterlogged, anaerobic, and relatively inactive biologically. He went on to unite studies of vegetation, climate, topography, water supply, water chemistry, and pattern of development into a scheme of peatland classification that spanned the complete range of peatland scales from small mossy hummocks and hollows on individual peatlands to large-scale geographical units such as the water divides between major river systems. He also used aerial photography, in conjunction with detailed examination of representative peatlands that provided "ground-truth," to predict the hydrologic properties of peatlands from regional climatic data. His work provided the basis for investigating the stability of peatland landscapes, which depends strongly on the balance between water supply and water loss. SOURCE: This sketch is derived from a more detailed biography in Ivanov (1981).

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 53 STATUS 1 BOX 2-11 WILLIAM HAROLD PEARSALL (1891–1964) William Harold Pearsall was a botanist of many talents who carried out important studies in limnology, wetland ecology, and algal physiology. He also was a pioneer landscape ecologist long before the term was invented. He is fondly remembered by colleagues and students as a veritable fountain of ideas that he shared generously— along with endless stories—with all who came into contact with him, particularly on the hills of northern Britain, where he was most at home. Pearsall was educated at the University of Manchester. After serving in World War I he joined the faculty of the University of Leeds, where he became a reader in botany. In 1938, he was appointed professor of botany at the University of Sheffield, and from 1944 until retirement, he was Quain Professor of Botany at University College, London. He was elected a fellow of the Royal Society in 1940 and received the Gold Medal of the Linnaean Society of London in 1963. Among his many service activities, he was a founder of the British Freshwater Biological Association, its honorary director from 1931 to 1937, and chairman of its council from 1954 onward. His influence on the staff was immense, and his frequent visits to the laboratories in the Lake District were greatly appreciated. He also was a charter member of the British Nature Conservancy and served as editor of the Journal of Ecology and the Annals of Botany. Pearsall's research began with his father, a well-known amateur botanist. Together they began, in 1913, to study the depth distribution of aquatic macrophytes of the English lakes in relation to light penetration. After the war, they extended their studies to phytoplankton. At the same time, Pearsall mapped the vegetation of Esthwaite North Fen, which he repeated 40 years later to show considerable changes. This research led to a series of papers outlining the development of the English Lakes, their sediments, and their planktonic and macrophytic vegetation. A seminal study of redox potentials in soils, sediments, and peats in relation to waterlogging, organic content, and the forms of nitrogen and iron provided the basis for a landmark presidential address that he delivered to the British Ecological Society in 1947. Pearsall's years of studying the hill country of northern Britain culminated in his 1947 book Mountains and Moorlands, a masterly account of soils and vegetation that shows his insight into the broad patterns of landscape development. At the same time, his aesthetic appreciation of that landscape was manifested in a delightful series of water colors. As John Lund has written, "One of his most wonderful characteristics was that it was out of disagreements that some of the most fruitful researches of his colleagues were likely to come, much to his delight. Their regard for him grew all the time, irrespective of whether they agreed with his ideas or not. Moreover, his hypotheses were by no means always incorrect; they might equally be too novel for people to appreciate…." 1 This biographical sketch owes much to an obituary by J. W. G. Lund (1965) and an account by A. R. Clapham (1971).

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 54 STATUS ecosystems. Chapter 3 describes many of these advances in more detail and explains the roles of limnologists, along with aquatic scientists in related discipline, in assessing and developing solutions for contemporary problems related to the degradation of inland waters. Many advances in limnology were made by academic limnologists and other scientists working in departments not traditionally focusing on limnology (such as civil and environmental engineering, environmental science, and earth sciences); others were made by interdisciplinary research teams associated with government agencies and with contract research and consulting firms. Thus, limnological research has spread beyond its traditional base of operations in academic departments of biological science. Activity in limnology in recent decades is reflected by the vitality of its professional societies and scholarly journals. Within the past 15 years, three new North American societies have formed, each resulting from the expanding activities in a particular aspect of limnology and its related aquatic sciences: 1. The North American Benthological Society (NABS) expanded from an older regional organization (the Midwest Benthological Society) in 1974, emphasizing stream ecology and processes occurring at the interface between water and land. 2. The North American Lake Management Society (NALMS) was established in 1980 as an outgrowth of expanding interest in restoring and rehabilitating lakes and reservoirs degraded by human activity. 3. The Society of Wetland Scientists (SWS) was founded in 1980 to promote research for understanding and managing wetlands. Memberships in the above three societies plus the two older limnological societies, the American Society of Limnology and Oceanography (ASLO) and the International Association for Great Lakes Research (IAGLR), total more than 12,000 (see Appendix B). Many limnologists also belong to SIL and to discipline-based societies. The aquatic section of the Ecological Society of America, for example, has more than 1,000 members (although many of these individuals also belong to one or more of the five primary limnological societies listed above). The scholarly and technical journals published by the limnological societies continue to grow in circulation and pages published annually (see Table 2-2), and several new journals that focus on different aspects of limnology (for example, Lake and Reservoir Management, Ecological Engineering, and Wetlands) have appeared within the past two decades. Moreover, annual meetings of the societies attract growing numbers of presentations and attendees. For example, the number of presentations at the annual meeting of NABS increased from 234 to 409 between 1984 and 1994, while the number of papers at the annual SWS meeting increased

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 55 STATUS from 51 to 306. It is apparent from this growth in presentations and publications that activity in limnology is continuing to increase. TABLE 2-2 Recent Publication Trends for Limnological Journals Journala Year L&O CJFAS JGLR JNABSb LRMc W Circulation 1984 5,215 2,000 na 943 na 460 1989 4,763 1,900 na 1,179 na 1,930 1994 5,171 1,675 na 1,441 na 3,848 Pages 1984 1,358 1,862 466 325 390 220 published 1989 1,766 2,437 728 375 242 327 1994 2,025 3,187 800 617 352 320d Publication 1984 6 12 4 4 1 1 frequency (issues per year) 1989 8 13 4 4 2 3 1994 8 13 4 4 3 4 Number of 1984 na 416 na 65 na 19 papers submitted 1989 na 421 na 73 na 37 1994 316e 474 na 96 na 80 NOTE: na = information unavailable. a Journal abbreviation and responsible society: L&O: Limnology and Oceanography, American Society of Limnology and Oceanography; CJFAS: Canadian Journal of Fisheries and Aquatic Science, National Research Council of Canada; JGLR: Journal of Great Lakes Research, International Association for Great Lakes Research; JNABS: Journal of the North American Benthological Society, North American Benthological Society; LRM: Lake and Reservoir Management, North American Lake Management Society; W: Wetlands, Society of Wetland Scientists. b First set of numbers for this journal represents 1986, the journal's first year of publication. c First set of numbers for this journal represents 1985, the journal's first year of publication. d Page size increased by approximately 70 percent. e This number is for 1993; no earlier statistics are available. Limnology courses continue to be offered at most major research universities. For example, 59 of 69 universities surveyed for this report indicated that they offer an introductory limnology course for undergraduates (see Appendix A). Furthermore, introductory limnology courses at major universities generally have stable or increasing enrollments; 55 of 57 universities responding to a survey question about student interest in limnology reported that interest is increasing or holding steady (see Appendix A). Graduate training in limnology is available at many of these institutions, even though only a few universities have distinct degrees or programs called limnology. In addition, during the past decade or so an increasing number of colleges and non-Ph.D.-granting universities (such as the University of Wisconsin, Stevens Point, described in Chapter 4) have developed M.S.-level programs related to limnology or aquatic science. Several new textbooks on stream and wetland limnology have been published, as have new editions of popular limnology books that focus on

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 56 STATUS lakes (e.g., Mitsch and Gosselink, 1993; Horne and Goldman, 1994; Allan, 1995). However, not all is well in limnology. Indeed, some of the positive characteristics of limnology at the close of the twentieth century can also be interpreted as indicators of underlying problems. For example, the formation of new societies is symptomatic of increased fragmentation, as well as an unwillingness on the part of the original society (ASLO) to embrace fully some of the newer aspects of the field, in particular applied limnology, resource management-oriented activities, and wetland ecology. In general, problems in the conduct of modern limnology can be grouped into six major areas: 1. inadequacy or instability of research support, especially in certain areas (such as physical and chemical limnology and wetland ecology); 2. loss of some prominent academic positions, especially in biological limnology; 3. growing fragmentation in academic programs (an ironic situation for an inherently interdisciplinary field); 4. inadequate educational programs, both at the general education level and at the professional level; 5. growing professional separation among various kinds of limnologists; and 6. poor public understanding of limnology and failure to identify it as a field that can contribute to the solution of aquatic problems important to human society. Limnologists have not been reluctant to express concerns about the viability of their field. Discussions on these issues have appeared in limnological journals over the past decade, most notably in Limnology and Oceanography (e.g., Jumars, 1990; Kalff, 1991; Wetzel, 1991). These discussions have led to several studies dedicated to critical self-examination and to the development of recommendations to overcome perceived deficiencies and problems. Major self-analyses include (1) the Freshwater Imperative (Naiman et al., 1995), a broad initiative of a diverse group of aquatic scientists to address research needs in limnology, develop plans for government- supported interdisciplinary research programs on freshwater ecosystems, and otherwise promote the professional development of the field; and (2) ASLO's self-assessment of the field (Lewis et al., 1995), which contains a broad range of recommendations to reinvigorate the field and reverse the trend toward fragmentation among its component disciplines and subject areas. As discussed in this chapter, much of the recent research support for limnology has been tied to targeted research programs in mission-oriented agencies focused on practical pollution problems. Although there is much to be gained from the focus that such programs provide, their funding

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 57 STATUS levels rise and decline over a relatively small number of years as public and congressional interest waxes and wanes or as scientists develop solutions to problems. This approach simply is not adequate to support the basic scientific research and consistent training of new generations of scientists needed if limnology is to play a role in supporting wise and sustainable management of inland aquatic ecosystems. Some contend that the lack of a central federal program for limnology has led to a lack of research funding opportunities in limnology and has contributed to a decline of this field in academia (Jumars, 1990). Others disagree with this pessimistic attitude and point to the many advances in understanding and practical accomplishments achieved by limnologists in recent decades. To a certain extent, these diverging opinions reflect basic philosophical differences (is the ''limnological cup" half full or half empty?) that can never be resolved completely. Nonetheless, it is likely that few regard current mechanisms for funding limnological research as optimal. Within the National Science Foundation (NSF), there is no program that deals specifically with limnology in its broad definition. Instead, support for limnological research is subsumed in a variety of programs, including NSF's Divisions of Atmospheric Sciences, Earth Sciences, Environmental Biology, Integrative Biology and Neuroscience, International Programs, Ocean Sciences, and Polar Programs (Firth and Wyngaard, 1993). In contrast, NSF has a specific division (Ocean Sciences) devoted to the study of oceanography, which is bolstered by a similar funding program administered by the Office of Naval Research (Jumars, 1990). Most of the support for limnological research in NSF comes from the Division of Environmental Biology. As a result, support for research in chemical and physical limnology is not emphasized, and opportunities for support of interdisciplinary and long-term research have been limited. For example, 90 percent of NSF's grants on subjects directly or indirectly related to limnology in 1991 included work with a biological component, but only 25 percent supported studies with a chemical component and only 2 percent supported studies with a physical focus (Firth and Wyngaard, 1993). One encouraging sign of change to promote interdisciplinary research on aquatic ecosystems within NSF is its new "Water and Watersheds" initiative. A joint effort between the NSF and the Environmental Protection Agency (EPA), this program targeted $10 million in competitively awarded funds in fiscal year 1995 to university-based aquatic research. In terms of generating proposals, the first competition announced in February 1995 was overwhelmingly successful: more than 650 proposals were submitted for review. Financial limitations meant that only about 30 proposals (roughly 5 percent) received funding. Nonetheless, the large response to the call for proposals suggests that the program addresses a major, unmet research need. The Water and Watersheds research initiative

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 58 STATUS was funded primarily by the EPA (roughly 70 percent) in 1995, and the program does not yet have a permanent home in the NSF administrative structure. Consequently, it is premature to conclude that this program will provide a long-term source of funds for interdisciplinary research in limnology, but developing a permanent program to fund such research should be a priority. Over the past decade or two, limnological programs have been eliminated or significantly downsized at some leading research universities as prominent faculty limnologists retired. Notable examples include G. E. Hutchinson of Yale University (Box 2-5); D. G. Frey of Indiana University, highly regarded for his examination of biological remains in sediments to chronicle past histories of lake conditions; and W. T. Edmondson of the University of Washington, noted for his pioneering studies of eutrophication in Lake Washington (see Chapter 4). Although Frey retired and was not replaced, Indiana University still offers a limnology course through its Department of Public and Environmental Affairs, but Yale no longer offers courses or employs faculty in limnology. The University of Washington offered a course in limnology for more than 30 years through the Department of Zoology, but when Edmondson's retirement was followed by cuts in state funding, the frequency of the course was reduced, and it was taught by visiting professors for several years (in 1996, the university again hired a limnologist to serve on its faculty). On a national basis, it is fair to say that some faculty positions have been lost because of declining financial resources in some universities, but in other cases, positions vacated by limnologists have been converted to other subject areas, usually some aspect of subcellular biology, which reflects a trend in many academic biology programs away from organismal and higher-level biology and toward subcellular and molecular scales. The loss of highly visible academic positions in biological limnology probably is the single most important factor contributing to the perception among academic limnologists that all is not well within their profession, but in some respects the concern about lost positions may not be well founded. As limnological positions have been los tin traditional biology departments, others have been added in departments and colleges of environmental science and engineering, fisheries science, natural resources, and other resource-oriented programs. It is possible that larger numbers of faculty are involved in teaching and research across the broad field of limnology at research universities in the 1990s than ever before. However, they are dispersed more widely across departments and colleges than they were in earlier decades, when limnology was a narrower and simpler field that focused on temperate lakes. In summary, the elimination or deemphasis of limnology in the biology departments of major research universities has left a leadership vacuum in limnology, at least at many institutions, as well as a vacuum in the training of biologists

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 59 STATUS with skills in basic systematics and the organismal biology of aquatic ecosystems. Overall, the dispersion of limnology into so many different academic programs in universities has led to severe fragmentation of the field. Few universities are producing limnologists with truly interdisciplinary backgrounds, an ecosystem perspective, and an ability to integrate across the sciences and major categories of aquatic ecosystems. In addition, most universities do not provide adequate course offerings in limnology at the general education level. The fragmentation of limnologists during their education continues at the professional level. There is no limnological society or organization that represents the field and its practitioners as a whole. Although most, if not all, of the traditional journals publish occasional articles on streams and wetlands, their focus generally is on lake science. There is no journal that covers both the fundamental and applied aspects of limnology and all major categories of water bodies within the domain of limnology. Lake, stream, and wetland limnologists and fisheries scientists largely go their separate ways when joining professional societies, attending conferences, and publishing scientific papers. Although the Ecological Society of America includes theoretical and applied ecologists in its membership and has a special applied ecology section, fundamental and more practical, management-oriented aspects of limnological science are covered by separate societies (ASLO and NALMS). Both aspects of limnology have much to gain from closer interactions. Limnologists involved in research on the Great Lakes also have their own society and journal, a situation that is particularly ironic given that ASLO combines limnologists and oceanographers. As noted earlier, Great Lakes research combines elements of both limnology and oceanography (the latter particularly in terms of the scale of research vessels and equipment needed to conduct the research). The American Fisheries Society combines interests in fundamental science (fish physiology and genetics) with fisheries management, and it formulates and publicizes positions on the application of science to resource management issues. Nonetheless, fisheries science is not well integrated into limnology at the professional level (or for that matter in academic programs), in spite of the fact that fish are obviously integral components of aquatic food webs. Although limnology is a diverse field, it is no more so than many other fields that have managed to bring their varied elements under the umbrella of one professional society that provides a sense of identity and public visibility to the field. Civil engineering, for example, sometimes is referred to as a "holding company" rather than a discipline because of the breadth and diversity of activities in which civil engineers are engaged. Nonetheless, one society, the American Society of Civil Engineers, represents the entire field. Similar situations prevail in chemistry, where the American Chemical Society includes theoretical and applied chemists working in

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 60 STATUS fields as diverse as quantum mechanics and polymer science, and in microbiology, where the American Society for Microbiology publishes six subdisciplinary journals dealing with a broad range of fundamental and applied studies. The fragmentation of limnology at the educational and professional levels has left the field with an identity crisis. Limnology is poorly understood by scientists and the general public. Even many aquatic scientists do not realize their ties to the general field of limnology or (in some cases) their effective involvement in limnological research. This problem of visibility tends to relegate limnologists and their science to secondary positions in public policy debates and decisions about aquatic resource management—situations in which their expertise is highly relevant. Root causes of the problems described in preceding paragraphs are numerous and include factors that are internal to the field of limnology and external factors over which limnologists have had little control. Professional fragmentation—exemplified by the lack of a single society and single journal that represents all major areas of the field—would seem to be a problem of limnologists' own making. In part, it reflects an unwillingness by the older limnological societies and journals to diversify themselves and fully embrace some of the newer trends, such as the emphasis on restoration- and management- oriented activities that spawned the formation of organizations such as NALMS and SWS. Clearly, limnologists have it within their own power to overcome this professional fragmentation, and indeed only they can do so. Causes of educational fragmentation are complicated and more difficult to assign. In large part, they reflect the long developmental history of academic disciplines and department structures within universities that have been defined for many decades by a primary orientation toward the basic science disciplines. Limnology, defined by the objects it studies (inland aquatic ecosystems), is inherently multidisciplinary and interdisciplinary, and components of the field have developed in many departments. The problems of academic limnology are a mirror of the problems of water science as a whole in higher education: water science is an interest within many fields, but it is not the primary focus of any of the traditional departments or disciplines. Moreover, "turf" problems inhibit any existing department from assuming too strong a leadership role over the entire field. At the same time, there probably is little enthusiasm among university administrators (deans and department heads) in this time of declining financial resources for reorganizations that would remove limnologically oriented faculty from existing programs and place them in new administrative units. It is interesting to note that the fragmentation typically found in water resource science and limnological programs in academic institutions does not hold for natural resource subjects that traditionally have been linked

LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 61 STATUS directly to production-oriented economic activities. For example, soil science is an inherently multidisciplinary and interdisciplinary subject, but it has achieved departmental status in many land-grant universities. A similar situation exists in the field of forestry. No one considers it unusual or improper to have microbiologists, chemists, and physicists in the same department of soil science; it should not be so difficult to convince university faculty and administrators that broad-based departments or schools of aquatic science are both feasible and desirable. Other recent critical examinations of limnology have dealt with the broad array of deficiencies and problems that face the field (e.g., Lewis et al., 1995) and with the development of a research prospectus and recommendations for better funding support (e.g., Naiman et al., 1995). Consequently, this report focuses on educational issues in limnology. In this context, the committee that wrote the report examined both the training of professional limnologists at all levels (B.S. to Ph.D.) and the provision of limnological information in the general education of college students and the public. Although the major emphasis of this report is education, the problems of limnology cannot be solved in academia alone. Also needed are improved links between those who conduct research in limnology and those who manage water resources. The professional societies in limnology have a critical role to play in helping to develop these links and in serving as advocates for the discipline of limnology as a whole. REFERENCES Allan, J. D. 1995. Stream Ecology: Structure and Function of Running Waters. New York: Chapman Hall. Beckel, A. L. 1987. Breaking New Waters. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters, special issue. Madison, Wisc.: Wisconsin Academy of Sciences, Arts, and Letters. Bradbury, J. P., and R. O. Megard. 1972. Stratigraphic record of pollution in Shagawa lake, northeastern Minnesota. Geol. Soc. Am. Bull. 83:2639–2648. Bradbury, J. P., and J. C. B. Waddington. 1973. The impact of European settlement on Shagawa Lake, northeastern Minnesota. Pp. 289–307 in Quaternary Plant Ecology, H. J. B. Birks and R. G. West, eds. Oxford, England: Blackwell. Brezonik, P. L., J. G. Eaton, T. M. Frost, P. J. Garrison, T. K. Kratz, C. E. Mach, J. H. McCormick, J. A. Perry, W. A. Rose, C. J. Sampson, B. C. L. Shelley, W. A. Swenson, and K. E. Webster. 1993. Experimental acidification of Little Rock Lake, Wisconsin: Chemical and biological changes over the pH range 6.1 to 4.7. Can. J. Fish. Aquat. Sci. 50:1101–1121. Cairns, J., Jr., B. R. Niederlehner, and D. R. Orvos, eds. 1992. Predicting Ecosystem Risk. Princeton, N.J.: Princeton Scientific Publishing. Carpenter, S. R., T. M. Frost, D. Heisey, and T. K. Kratz. 1989. Randomized intervention analysis and the interpretation of whole-ecosystem experiments. Ecology 70:1142–1152. Charles, D. F., R. W. Battarbee, I. Renberg, H. Van Dam, and J. P. Smol. 1989. Paleoecological

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LIMNOLOGY, THE SCIENCE OF INLAND WATERS: EVOLUTION AND CURRENT 63 STATUS systems. Pp. 110–127 in Proceedings of the International Large River Symposium. D. P. Dodge, ed. Can. Spec. Publ. Fish. Aquat. Sci. 106. Kalff, J. 1991. On the teaching and funding of limnology. Limnol. Oceanogr. 36:1499–1501. Kitchell, J. F., ed. 1992. Food Web Management: A Case Study of Lake Mendota. New York: Springer-Verlag. Kolkwitz, R., and M. Marsson. 1908. Ökologie der pflanzlichen Saprobien. Ber. Deut. Botan. Ges. 26a:505–519. Kolkwitz, R., and M. Marsson. 1909. Ökologie der tierischen Saprobien. Int. Rev. Ges. Hydrobiol. Hydrol. 2:126–152. LeBlanc, H. 1912. Le Professeur Dr. Francois Alphonse Forel, 1841–1912. Actes Soc. Helv. Sci. Nat. 95:109–148. Lewis, W. M., S. Chisholm, C. D'Elia, E. Fee, N. G. Hairston, J. Hobbie, G. E. Likens, S. Threlkeld, and R. G. Wetzel. 1995. Challenges for limnology in North America: An assessment of the discipline in the 1990s. ASLO Bull. 4(2):1–20. Likens, G. E., and F. H. Bormann. 1974. Linkages between terrestrial and aquatic ecosystems. BioScience 24:447–456. Lindeman, R. L. 1942. The trophic-dynamic aspect of ecology. Ecology 23:399–418. Lund, J. W. G. 1965. Prof. W. H. Pearsall, F.R.S. Nature 205:21. Mitsch, W. J. 1994. Energy flow in a pulsing system: Howard T. Odum. Ecol. Eng. 3:77–105. Mitsch, W., and J. G. Gosselink. 1993. Wetlands, 2nd ed. New York: Van Nostrand Reinhold. Mortimer, C. H. 1956. E. A. Birge, an explorer of lakes. Pp. 165–206 in E. A. Birge, a Memoir, G. C. Sellery, ed. Madison: University of Wisconsin Press. 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. Newbold, J. D., J. W. Elwood, R. V. O'Neill, and W. Van Winkle. 1981. Measuring nutrient spiraling in streams. Can. J. Fish. Aquat. Sci. 38:860–863. Nipkow, F. 1920. Vorläufige Mitteilungen über Untersuchungen des Schlammabsatzes im Zür. Rev. Hydrol. 1:100–122. Odum, H. T. 1957. Trophic structure and productivity of Silver Springs, Florida . Ecol. Monogr. 27:55–112. Odum, H. T. 1970. Environment Power and Society. New York: Wiley-Interscience. Odum, H. T. 1994. Ecological engineering: The necessary use of ecological self-design. Ecol. Engr. 3:115–118. Odum, H. T., and R. F. Pigeon, eds. 1970. A Tropical Rain Forest. Oak Ridge, Tenn.: U.S. Atomic Energy Commission. Overbeck, J. 1989. Plön—History of limnology, foundation of SIL and development of a limnological institute. Pp. 61–65 in Limnology in the Federal Republic of Germany, W. Lampert and K. O. Rothhaupt, eds. Kiel, Germany: International Association for Theoretical and Applied Limnology. Pringle, C. M., R. J. Naiman, G. Bretschko, J. R. Karr, M. W. Oswood, J. R. Webster, R. L. Welcomme, and M.J. Winterbourn. 1988. Patch dynamics in lotic systems: The stream as a mosaic. J. N. Am. Benthol. Soc. 7:503–524. Rasmussen, P. W., D. M. Heisey, E. V. Nordheim, and T. M. Frost. 1993. Time-series intervention analysis: Unreplicated large-scale experiments. Pp. 138–158 in Design and Analysis of Ecological Experiments, S. M. Scheiner and J. Gurevitch, eds. New York: Chapman and Hall. Roberts, L. 1987. Federal report on acid rain draws criticism. Science 237:1404–1406. Schindler, D. W., T. M. Frost, K. H. Mills, P. S. Chang. I. J. Davies, L. Findlay, D. F. Malley, J. A. Shearer, M. A. Turner, P. J. Garrison, C. J. Watras, K. E. Webster, J. M. Gunn, P. L. Brezonik, and W. A. Swenson, 1992. Comparisons between experimentally- and atmospherically-acidified lakes during stress and recovery. Proc. R. Soc. Edinburgh 97B:193– 226.

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To fulfill its commitment to clean water, the United States depends on limnology, a multidisciplinary science that seeks to understand the behavior of freshwater bodies by integrating aspects of all basic sciences—from chemistry and fluid mechanics to botany, ichthyology, and microbiology. Now, prominent limnologists are concerned about this important field, citing the lack of adequate educational programs and other issues.

Freshwater Ecosystems responds with recommendations for strengthening the field and ensuring the readiness of the next generation of practitioners. Highlighted with case studies, this book explores limnology's place in the university structure and the need for curriculum reform, with concrete suggestions for curricula and field research at the undergraduate, graduate, and postdoctoral levels. The volume examines the wide-ranging career opportunities for limnologists and recommends strategies for integrating limnology more fully into water resource decision management.

Freshwater Ecosystems tells the story of limnology and its most prominent practitioners and examines the current strengths and weaknesses of the field. The committee discusses how limnology can contribute to appropriate policies for industrial waste, wetlands destruction, the release of greenhouse gases, extensive damming of rivers, the zebra mussel and other "invasions" of species—the broad spectrum of problems that threaten the nation's freshwater supply. Freshwater Ecosystems provides the foundation for improving a field whose importance will continue to increase as human populations grow and place even greater demands on freshwater resources. This volume will be of value to administrators of university and government science programs, faculty and students in aquatic science, aquatic resource managers, and clean-water advocates—and it is readily accessible to the concerned individual.

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