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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology The Role of Major Research Centers in the Study of Inland Aquatic Ecosystems Thomas M. Frost Trout Lake Station Center for Limnology University of Wisconsin–Madison Boulder Junction, Wisconsin Elizabeth Reid Blood J. W. Jones Ecological Research Center Newton, Georgia SUMMARY Major research centers have made substantial contributions to the basic understanding of inland aquatic ecosystems. Such centers function by providing access to important natural ecosystems and by fostering interdisciplinary investigations of a wide range of environmental phenomena. This paper provides seven representative examples of aquatic research centers and summarizes their contributions. INTRODUCTION Much of the present understanding of inland aquatic ecosystems can be traced to contributions from major research centers. The success of research centers can be linked to a few of their key features. Many of these centers provide or facilitate access to sites with one or a group of important aquatic habitats. Such centers often provide logistical support for the routine collection of fundamental information on habitats, providing long-term records on system condition. Other types of centers function primarily by fostering interactions among a group of researchers rather than by providing access to a particular location. Perhaps most important, collaborations at many of these different centers frequently lead to interactions between investigators with different disciplinary perspectives often
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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology not combined in smaller-scale investigations of aquatic ecosystems. A few research sites also have a capability for large-scale or multiple experimental manipulations. Finally, several research centers have shown how basic science and management perspectives can be combined. EXAMPLES OF CONTRIBUTIONS FROM RESEARCH CENTERS A wide variety of research centers have made important contributions to the basic understanding of aquatic ecosystems. Examples, discussed below, are Hubbard Brook Experimental Forest, Experimental Lakes Area, University of Wisconsin–Madison, Woods Hole Marine Biological Laboratory, Lake Washington, Coweeta Experimental Forest, and H. J. Andrews Experimental Forest. Hubbard Brook Ecosystem Study The Hubbard Brook Experimental Forest (HBEF) is a striking example of the contributions that can be made by a research center. The HBEF was established by the U.S. Forest Service in 1955 to investigate the management of watersheds in New England. The research program at the forest, developed largely through the efforts of G. E. Likens and F. H. Bormann, has made substantial contributions to the general understanding of both aquatic and terrestrial ecosystems (e.g., Likens et al., 1977; Bormann and Likens, 1979; Likens, 1985a). Work has focused on processes occurring in the forests and streams in the area and on Mirror Lake near the base of HBEF. Fundamental techniques for assessing ecosystem nutrient cycling were developed by combining the perspectives of hydrologists and biogeochemists (Likens et al., 1977). Insights gained into nutrient cycling at HBEF through whole-watershed clear-cutting experiments and other harvesting programs illustrate the usefulness of ecosystem-scale manipulations (Likens et al., 1977). Detection of the acid deposition phenomenon in North America through precipitation records collected over an extended period has demonstrated the importance of long-term monitoring (Likens et al., 1972, 1984). Research has helped to delineate the role of streams in processing nutrients and organic matter (Fisher and Likens, 1973; Meyer and Likens, 1979). Documented responses to varied timber harvesting techniques at Hubbard Brook have also illustrated the ways in which research with a fundamentally basic science perspective can shed important light on the impact of land-use practices (e.g., Bormann and Likens, 1985; Likens, 1985b). More recently, the Hubbard Brook Experimental Forest has been incorporated as a site within the National Science Foundation's Long-Term Ecological Research (LTER) program, facilitating the continued evaluation of aquatic and terrestrial ecosystem processes at the site (Franklin et al., 1990).
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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology Experimental Lakes Area The Experimental Lakes Area (ELA), located in the lake district of northwestern Ontario, provides a second prime example of the wealth of information that can arise from a research center. ELA was originally established in the early 1960s by the Canadian government under the leadership of W. E. Johnson and J. R. Vallentyne to investigate problems associated with eutrophication (Johnson and Vallentyne, 1971). Research there has since been expanded, under the leadership of D. W. Schindler, to combine a whole-system experimental perspective with long-term monitoring to provide a basic understanding of aquatic ecosystems (e.g., Schindler, 1973, 1987, 1988). Some of the first projects at ELA provided important support for management programs to combat eutrophication by confirming the importance of phosphorus as a limiting nutrient in most inland aquatic ecosystems (Schindler, 1974). Subsequent work expanded the focus of the site to consider the effects of acid deposition (Schindler et al., 1985) and other contaminants (Schindler, 1987). Insights gained into the microbial factors mitigating the effects of lake acidification illustrate the importance of combining different disciplinary perspectives in understanding aquatic ecosystem processes (Schindler et al., 1986). The breakdown of sulfate ions under anaerobic conditions with an accompanying removal of acid ions was shown to provide a substantially greater resistance to the effects of sulfuric acid in deposition than had been expected (Cook et al., 1986). In a parallel study, bacterially mediated transitions among different forms of nitrogen were also shown to be strongly influenced by pH in some lakes (Rudd et al., 1988). More recently, long-term data collected on unmanipulated lakes at ELA have provided evidence for climatic warming trends in boreal lakes (Schindler et al., 1990), illustrating some of the potential effects of the climatic changes predicted by several global circulation models and the general importance of extended monitoring of inland aquatic systems. Wisconsin The University of Wisconsin–Madison is perhaps one the best examples of long-continuing efforts at a research center focused on inland aquatic ecosystems (Beckel, 1987). E. A. Birge initiated his lake studies there in 1875, beginning with a focus on lakes near the university campus in Madison (Frey, 1963). For more than 60 years, C. Juday was his collaborator on most of these efforts. Expanding on their work around Madison, they were attracted by the potential for comparative studies in the extensive lake district in the Northern Highland of Wisconsin. They established a field station on Trout Lake in 1925 and organized regular summer
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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology research by a large group of collaborators. Their research continued until the early 1940s. Following a hiatus, A. D. Hasler led a second major period of research with an emphasis on experimental studies (Hasler, 1964). This research, involving several large-scale experiments, was conducted around Madison and in the Northern Highland area. Particularly important was the neutralization of a naturally acidic lake by using a now classic design in which the basin was divided into similar manipulated and unmanipulated sections (Hasler, 1964). Researchers involved in several more recent whole-ecosystem manipulations trace their inspiration to these early large-scale experiments by Hasler and his coworkers (e.g., Likens, 1985c; Schindler, 1988; Carpenter and Kitchell, 1994). Research in Wisconsin continues with major ongoing efforts in the Madison area, primarily on Lake Mendota, and in the Northern Highland. By evaluating current conditions relative to the range of conditions in the past, recent work on Mendota has illustrated the utility of long-term data in understanding system processes (Brock, 1985; Kitchell, 1992). This work also provides another example of the potential gains when nontraditional fields are combined in research projects, in this case fisheries biology and limnology (Vanni et al., 1990). Substantial shifts in the lake's water clarity were ultimately attributable to an unusual die-off of one of its dominant fish. Lake Mendota has also been the site of a major joint collaboration between lake managers and basic scientists (Kitchell, 1992). Other efforts in Wisconsin include a substantial expansion of projects at the Trout Lake Station in the Northern Highland. The station has served as the staging facility for one of the sites in the Long-Term Ecological Research program (Magnuson et al., 1984) and for a whole-lake acidification experiment (Brezonik et al., 1993). LTER work here has provided another example of the utility of combining disciplines, in this case ground water geology and limnology, by demonstrating how a relatively small portion of the lake's hydrologic inputs could play a critical role in its overall nutrient budget because of the high concentration of minerals in ground water (Hurley et al., 1985). Regional evaluations of long-term records illustrate how variability, often perceived as an impediment to system understanding, can provide useful insights into the processes controlling system features (Kratz et al., 1987). Related projects have further demonstrated how evaluating patterns in data collected during the same period from sets of lakes within a region can indicate how different system properties are controlled by forces that operate on fundamentally different spatial scales (Kratz et al., 1991). Additional northern work has continued, using a large-scale experimental approach to evaluate the effects of lake acidification (Brezonik et al., 1993) and the role of food web structure on basic lake processes (Carpenter and Kitchell, 1993). The latter project has been conducted at
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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology the original site of some of the early whole-lake manipulations with the support of the University of Notre Dame's Environmental Research Center on the Michigan-Wisconsin border. Ecosystem Center at Woods Hole The Ecosystem Center at Woods Hole Marine Biological Laboratory provides an example of a center that supports a multidisciplinary group of investigators working at different field sites. Under the leadership of J. Hobbie and B. Peterson, the group has used a combination of large-scale manipulations and long-term monitoring to examine the basic limnology of Arctic tundra ponds (Hobbie, 1980). This group has demonstrated that the addition of phosphorus can convert an Arctic river from a heterotrophic to an autotrophic ecosystem (Peterson et al., 1985). Their work has shown the importance of tundra lakes and streams as conduits for the transfer of major quantities of carbon dioxide to the atmosphere (Kling et al., 1991) and helped to develop the use of stable isotope techniques for examining food webs (Peterson and Fry, 1987). Research in other locations has documented the importance of sulfur cycling in the transfer of energy in coastal salt marshes (Howarth and Teal, 1979). The center's more recent efforts have also led to the establishment of an Arctic site within the LTER network (Franklin et al., 1990) and of a near-shore site within the National Science Foundation's Land-Margin Ecosystems program. Lake Washington Another example of a different type of research center is Lake Washington near Seattle, Washington. Population development in the Seattle area led to an increased loading of nutrients into Lake Washington through the 1950s with a concomitant deterioration of water quality. A program was then established, with substantial guidance from W. T. Edmondson, to divert sewage from the lake. Edmondson and a group of researchers at the University of Washington then documented Lake Washington's responses to these management efforts (Edmondson, 1972), providing strong evidence for the usefulness of sewage nutrient control as a management practice at a critical stage in the eutrophication controversy. Analyses by Edmondson's group documented the positive effects of the sewage diversion program, provided basic understanding of the nature of the eutrophication process, and demonstrated a classic example of the potential of sound management practices for inland aquatic ecosystems. Their monitoring of Lake Washington continued following the initial responses to sewage diversion, revealing another substantial and surprising change in water transparency. From 1976 onward, the lake exhibited higher levels of water clarity than had been recorded at any earlier stage in its history.
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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology These levels were linked with the emergence of previously inconspicuous Daphnia species (Edmondson and Litt, 1982) and provide evidence of how changes in a lake's food web can have a strong influence on its water clarity. Edmondson (1991) reviews the details of the Lake Washington story and illustrates the sometimes complex interplay between basic science and lake management issues. This program illustrates how a single leader with long-term support for research can do a very effective job of fostering fundamental ecosystem understanding. It also illustrates the precarious nature of such programs; since Edmondson's retirement in the mid-1980s, the University of Washington has chosen not to continue its important history of limnological research and has hired no replacement for him. Coweeta Experimental Forest Like the program at HBEF, research at Coweeta Experimental Forest illustrates how a research center can generate important general information about both aquatic and terrestrial ecosystem processes (Swank and Crossley, 1988). In addition to providing fundamental information on the control of forest type over the amount of water exiting a watershed, work at Coweeta has documented how forest conditions influence the amount of organic materials transported by streams (Wallace et al., 1982; Tate and Meyer, 1983). Other research has shown how watershed conditions affect the basic chemistry and biology of streams (Webster and Patten, 1979; Meyer and Tate, 1983) and how the organisms occurring within streams influence the processing of organic matter (Meyer et al., 1988; Perlmutter and Meyer, 1991). The removal of all aquatic insects produced substantial changes in the transport of materials by streams, demonstrating the importance of insects in fundamental stream processes and further illustrating the usefulness of a large-scale experimental approach (Cuffney et al., 1984). H. J. Andrews Experimental Forest One of the major synthetic perspectives in river ecology, the River Continuum Concept, concerns how the proportions of fundamental ecosystem processes change systematically with distance downstream from headwaters to the ocean. This model can be traced in part to interactions arising at the H. J. Andrews Experimental Forest (HJAEF) along with the Stroud Water Research Center (Vannote et al., 1980). Multidisciplinary perspectives at HJAEF have helped develop an understanding of how geomorphology exerts a fundamental influence on basic ecosystem processes (Swanson et al., 1988). Additionally, work at HJAEF has indicated how coarse woody debris can influence stream processes, such as the rates at which water is transported, the decomposition of organic materials, and
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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology the rates of biogeochemical processes (Harmon et al., 1986). Other research has shown how processes in the riparian zone surrounding a stream have a wide range of effects that can best be understood from an ecosystem perspective (Gregory et al., 1991). Finally, research at HJAEF also demonstrated how forest management practices can have critical influences on stream function, including the usefulness of these habitats for the breeding success of fishes (Gregory et al., 1987). CURRENT STATUS AND FUTURE POSSIBILITIES FOR RESEARCH CENTERS Most of the centers described in this paper continue to remain quite active, and many are currently associated with the National Science Foundation Long-Term Ecological Research program. This program also includes additional sites that emphasize lake studies, such as one focused on the Dry Valley Lakes in Antarctica; several stream study programs (Meyer et al., 1993); and a coastal site, the Virginia Coast Reserve. The extensive contributions from research centers make a strong case for a program that will further the establishment and continuation of such centers. New centers should be based on several basic principles: (1) a broad multidisciplinary foundation; (2) the collection of long-term baseline data on a number of systems within an area; (3) an opportunity to conduct large-scale, whole-ecosystem manipulations; and (4) a solid infrastructure to facilitate data collection and experimental work on a variety of scales. New centers should be planned with a recognition of geographic and system limitations on the present set of research sites. For example, the historic sites are quite limited geographically and do not effectively represent water bodies in the southern part of the continent, nor do they provide sufficient baseline data on reservoirs. Research centers should be encouraged to develop interactions among major research sites and opportunities for graduate student training, including programs for short- and long-term visiting scientists and semester-long programs for graduate students that involve visits to a series of research centers. A good model is the highly successful Organization for Tropical Studies Tropical Ecology program, which has fostered a range of research throughout tropical ecosystems. Overall, the contributions from research centers are quite substantial. They have played a critical role in developing the fundamental understanding of inland aquatic ecosystems. The opportunities for research at these centers should be continued and expanded. REFERENCES Beckel, A. L. 1987. Breaking New Waters: A Century of Limnology at the University of Wisconsin. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters . Special Issue. Madison: Wisconsian Academy of Sciences, Arts, and Letters.
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