U.S. Geological Survey Circular 1220 Online Version 1.0 The U.S. Geological Survey and the Chesapeake Bay -- The Role of Science in Environmental Restoration
The circular is presented in two versions: a PDF FILE [9.9 MB] and a TEXT FILE with no graphics. If you are connected to the Web through a modem, you should be aware that it may take some time to download the PDF file. If you have Adobe Acrobat Reader installed on your computer, you may view and/or print the PDF version of this report. If you do not have Acrobat Reader, you may download it here for free:			The Chesapeake Bay is the Nation's largest estuary and historically has supported one of the most productive fisheries in the world. The 64,000-square-mile watershed of the bay provides vital habitat for migratory birds using the Atlantic Flyway. In addition to supporting aquatic communities and wildlife, the bay's watershed serves the economic and recreational needs of 15 million people. The fertile soils of the watershed support significant agricultural production. The agricultural products and other goods produced in the watershed are shipped through ports on the bay, such as Baltimore, Md., and Norfolk, Va., to the world. Unfortunately, the commercial, economic, and recreational value of the bay and its watershed has been degraded by poor water quality, loss of habitat, and overharvesting of living resources. Forests that filtered pollutants from the bay and its rivers have been cut down and replaced with cities, suburbs, and farms. Manmade pollutants, loss of vital habitat such as wetlands and underwater plants, and overharvesting of fish and shellfish have substantially reduced the abundance and diversity of living resources. One of the biggest threats to the bay's water quality and the life that depends on it, ironically, is the bay's overabundance of nutrients. As human population has grown in the watershed, with an accompanying growth in agriculture, an overabundance of nutrients has entered the bay. Excess nutrients have stimulated algal blooms; as the blooms decompose, they use up dissolved oxygen and cause large areas of low dissolved oxygen in the bay. The low dissolved oxygen has killed many of the bottom-dwelling animals, such as oysters, in the bay. The algal blooms, along with sediment eroding from the land, also block sunlight needed by underwater grasses. Without sunlight, the bay grasses die, removing important habitat for fish and shellfish and food for waterbirds. The bay was listed as an "impaired water body'" in 1999 under the Clean Water Act. Improvements to water-quality conditions in the bay must be met by 2010, or regulatory approaches to achieve these standards will be implemented.