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.
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