of energy, materials, and information with an emphasis on interconnections, dynamics, and exchanges with the external environment. Organisms are linked through the exchange of energy according to the laws of thermodynamics and materials through biogeochemical cycles. A dynamic equilibrium prevails with changes occurring through evolution and succession.
There is a greater awareness in the water resource management community that the piecemeal approaches of the past are insufficient. The new ecosystem assessment bandwagon is in some respects a "let's be smart about it" approach, where the relevant knowledge is applied and critical missing information is obtained. Obviously, greater knowledge and understanding of aquatic ecosystems will contribute to the success of these efforts and of this ecosystem-based approach.
A simple example of a remediation effort for an acid mine drainage stream in the Rocky Mountains illustrates how the questions identified above are relevant to addressing important water resource and environmental issues. In the 1800s and early part of this century, there was a mining boom in the Rocky Mountains, and this boom spurred the development of the western states. Many of these mines are now abandoned, but their legacy includes an almost uncountable number of acidic, metal-enriched water discharges into mountain streams, with elevated metal concentrations in larger rivers. The ecological consequences of the acid mine drainage are not subtle. In the headwater streams, the streambed is typically covered with hydrous iron oxides, known as yellowboy; in the larger rivers, fish populations have high body burdens of metals, which limit their survival. In the Arkansas River, which drains the Lake County mining district in the Colorado Rockies, trout do not survive beyond four years because of accumulated metals in their tissues.
In many of these areas, there are public and legal incentives to clean up such sites. For example, in the summer of 1994, 268 members of Volunteers of Colorado came to the Pennsylvania mine site on Peru Creek in Colorado to help restore the creek by shoveling manure into two large plastic-lined pits. These pits will become artificial wetlands to treat the mine effluent. The pits are located adjacent to a liming facility that was built in the 1980s and proved to be a failure. Such treatments are being tried in many areas to ameliorate both coal and metal mining wastes. Although the volunteers at Peru Creek were enthusiastic and hopeful, from a scientific perspective can we be sure that this approach will work in either the short or the long term?
Many of the issues, challenges, and unanswered questions raised in the preceding section come into play in a more specific way in this example