An unparalleled scientific resource endangered.

N half a century ago, a unique resource for freshwater research was created. The Experimental Lakes Area (ELA) consists of 58 lakes and their drainage basins in Ontario, Canada. The ELA was designed to allow whole-lake manipulation experiments; in addition, unperturbed ELA lakes have been monitored for the past 44 years. There is no other facility in the world that allows for the study of physical, chemical, and biological processes in whole-lake ecosystems at this order of magnitude. Now, this facility is under the threat of closure in 2013. The planned closure of the ELA has inspired outspoken support from the scientific community (see: http://saveela.org/). It has also highlighted the importance of two central features of the ELA: ecosystem-scale experiments and long-term monitoring. These features have enabled the ELA to generate policy-relevant science that has had major impact on political decision-making in the environmental arena for nearly four decades. Two classic examples of policy-relevant science at ELA are the studies of the roles of nitrogen and phosphorus in lake eutrophication 1 and of the impacts of lake acidification on fish. The former study produced one of the truly iconic images in ecology (see Figure 1) and motivated legislative and regulatory measures to control phosphate inputs to inland and coastal waters. Results of the latter study motivated controls on smokestack emissions of sulfur dioxide across all of North America. More recently, the complete collapse of a fish population in response to exposure to artificial estrogen has been observed in a new experiment. An ongoing experiment on the whole-lake effects of nanosilver will be compromised if the closure proceeds as planned. Whole-lake experiments produce more than just striking aerial photographs. They allow researchers to capture the effects of complex interactions across trophic levels and provide direct evidence of pollutant impacts on lakes without questionable extrapolation from small bottles to the ecosystem. This provides the robust results that are needed to justify significant expenditures of public funds for pollution control and mitigation. Less well-known are the long-term records of physical, biological and chemical parameters that have been compiled for unperturbed ELA lakes. These consistent, long-term records are invaluable for the identification of environmental trends in an era of global climate change. As early as 1990, a signature of