Introduction—Acidic Deposition and Aquatic Ecosystems: Regional Case Studies

Abstract

Acidic deposition and its effects on aquatic ecosystems have been major scientific and public policy issues in the United States since the early 1970s. The high level of concern arises primarily from the potential for wide-scale and long-term changes in water chemistry and the resulting loss of aquatic biota, especially fish. Considerable research has been performed and hundreds of scientific papers and several major books and reports have been written on the subject. We now have a good understanding of the nature and extent of at least wet acidic deposition, and we know that current low pH values for wetfall are caused primarily by sulfur and nitrogen oxide emissions from combustion of fossil fuels. From numerous surveys and studies, including the U.S. Environmental Protection Agency’s (EPA) National Surface Water Survey (NSWS), we have learned much about the current status of low-alkalinity surface waters in many regions of the country, and the extent to which water chemistry has been affected by acidic deposition. However, the many and diverse studies completed by state and federal agencies, universities, and other organizations and individuals have not been thoroughly analyzed and integrated on a regional or national scale.