Chesapeake Bay

The Chesapeake Bay is the largest estuary (186 mi [300 km] long) in the United States. The Bay was formed 1500 years ago by the retreat of glaciers and the subsequent sea level rise that inundated the lower Susquehanna River valley. The Bay has a drainage basin of 64,076 square miles (166,000 sq km) covering six states and running through Pennsylvania, Maryland, the District of Columbia, and Virginia before entering the Atlantic Ocean. While 150 rivers enter the Bay, a mere eight account for 90% of the freshwater input, with the Susquehanna alone contributing nearly half. Chesapeake Bay is a complex system, composed of numerous habitats and environmental gradients.

Chesapeake Bay's abundant natural resources attracted native Americans, first settling on its shores. The first European record of the Bay was in 1572 and the area surrounding Chesapeake Bay was rapidly colonized by Europeans. In many ways, the United States grew up around Chesapeake Bay. The colonists harvested the Bay's resources and used its waterways for transportation . Today 10 million people live in the Chesapeake Bay's drainage basin, and many of their activities affect the environmental quality of the Bay as did the activities of their ancestors.

The rivers emptying into the Bay were also used by the colonists to dispose of raw sewage. By the middle 1800s some of the rivers feeding the Bay were polluted: the Potomac was recorded as emitting a lingering stench. The first sewer was constructed in Washington, DC, and it pumped untreated waste into the Bay. It was recognized in 1893 that the diseases suffered by humans consuming shellfish from the Bay were directly related to the discharge of raw sewage into the Bay. Despite this recognition, efforts in 1897 by the mayor of Baltimore to oppose the construction of a sewage system that discharged sewage into the Bay in favor of a "land filtration technique" failed. Ultimately, a secondary treatment system discharging into the Bay was constructed. In the mid-1970s, a $27 million government-funded study of the Bay's condition concluded that the deteriorating quality of the Chesapeake Bay was a consequence of human impacts. But it was not until the early 1980s that an Environmental Protection Agency (EPA) report on the Chesapeake focused interest on saving the Bay, and $500 million was spent on cleanup and construction of sewage treatment plants.

While the Chesapeake Bay is used primarily as a transportation corridor, its natural resources rank a close second in importance to humans. The most commercially important fisheries in the Bay are the native American oyster (Crassostrea virginica ), blue crab (Callinectes sapidus ), American shad (Alosa sapidissima ), and striped bass (Marone saxatilis ). Fisherman first began to notice a decline in fish populations in the 1940s and 1950s, and since then abundances have declined even further. Since the turn of the century, the oyster catch has declined 70%, shad 85%, and striped bass 90%. In the late 1970s, the EPA began to study the declining oyster and striped bass populations and concluded that their decline was due to a combination of over-harvesting and pollution .

Work by the EPA and other federal and state agencies has identified six areas of environmental concern for the Bay: (1) excess nutrient input from both sewage treatment plants discharging into the Bay and runoff from agricultural land; (2) low oxygen levels as a result of increased biochemical oxygen demand , which increases dramatically with loading of organic material; (3) loss of submerged aquatic vegetation due to an increase in turbidity; (4) presence of chemical toxins ; (5) loss to development of wetlands surrounding the Bay that serve as nurseries for juvenile fish and shellfish and as buffers for runoff of nutrients and toxic chemicals ; and (6) increasing acidity of water (measured by pH ) in streams that feed the Bay. These streams are also nursery areas for larval fish that may be adversely affected by decreasing pH.

The increasing growth of phytoplankton—free-floating single-celled plants—in the Bay is generally considered to be a significant contributor to the decline in environmental quality of the Chesapeake Bay. The number of algal blooms has increased dramatically since the 1950s and is attributed to the high levels of the plant nutrients nitrogen and phosphorus that are discharged into the Bay. In the 1980s and 1990s, it was estimated that discharge from sewage treatment plants and agricultural runoff accounted for 65% of the nitrogen and 22% of the phosphorus found in the Bay. Acid rain , formed from discharges from industrial plants in Canada and the northeast United States, contributed 25% of the nitrogen found in the Bay. Excess nutrients encourage phytoplankton growth, and as the large number of phytoplankton die and settle to the bottom, their decomposition robs the water of oxygen needed by fish and other aquatic organisms. When oxygen levels fall too low, these organisms die or flee from the regions of low oxygen. Decomposition of dead organic matter further reduces the concentration of oxygen. During the late twentieth and early twenty-first centuries, Finfish and shellfish kills became increasingly common in the Bay.

Phytoplankton blooms and the increase in suspended sediments resulting from shoreline development and poor agricultural practices have increased turbidity and led to a decline in submerged aquatic vegetation (SAV) such as eelgrass . SAV is extremely important in the prevention of erosion of bottom sediment and as critical habitat for nursery grounds of commercially important fish and shellfish.

Chemicals introduced into the Bay from several sites may have contributed to the decline in the Bay's fish and bird populations. For example, in 1975, the pesticide Kepone was leaked or dumped into the James River, poisoning fish and shellfish. Harvests of some species are still restricted in the area of this spill. Chlorine biocides used in wastewater treatment plants and power plants , which discharge into the Bay, are known human carcinogens and can be toxic to aquatic organisms. Polycyclic aromatic hydrocarbons (PAH) have caused dermal lesions in fish populations in the Elizabeth River. PAHs also affect shellfish populations. In the 1990s, public concern focused on tributyl tin (TBT) that was used in anti-fouling paint on recreational and commercial boats. TBTs belong to a family of chemicals known as organotins, which are toxic to shellfish and crustaceans. The diversity of chemical pollutants found in the Bay is exemplified by the results of research that identified 100 inorganic and organic contaminants in striped bass caught in the Bay. As of 2002, research efforts were underway to determine the extent of the damage from toxins to natural resources.

Work by private and governmental agencies has started to reverse the declining environmental quality of the Chesapeake Bay. In 1983 Maryland, Virginia, Pennsylvania, the District of Columbia, the Chesapeake Bay Commission, and the EPA signed the Chesapeake Bay Agreement, which outlined procedures to correct many of the Bay's ecological problems, particularly those caused by nutrient enrichment. In 1987 the agreement was significantly expanded and required that the signatories adopt a strategy that would result in at least a 40% reduction in nitrogen and phosphorus entering the Bay by the year 2000. Since 1985, increasing compliance with discharge permits, prohibition of the sale of phosphate-based detergents , and the upgrading of wastewater plants has resulted in a 2% reduction in the discharge of nitrogen and a 39% reduction of phosphorous from point sources of pollution. Controls on agriculture and urban development have resulted in approximately 7% reductions in the amount of both nitrogen and phosphorus entering the Bay from nonpoint sources. The amount of toxins entering the Bay have also been reduced. Tributyl tin has been banned for use in anti-fouling paints on non-military vessels, pesticide runoff has been reduced by using alternate strategies for pest control, and since 1987, toxic emissions from industrial sources have declined more than 40%. At the same time, some of the Bay's critical habitats are recovering: 22,000 more acres of SAVs are now growing than in 1984, although the total amount of 60,000 acres is still a fraction of the estimated 600,000 acres the historical SAV distribution, man-made oyster reefs are being created to expand suitable habitat for oysters, and rivers are being cleared of obstacles such as dams and spillways to provide access to spawning areas by migratory fish.

Conflict between commercial and environmental interests have encumbered some of the restoration efforts. Research on the life-history of crabs and oysters shows that limiting the size of crabs that can be sold and the numbers of oysters that can be harvested will help these fisheries rebound, but regulations to limit crab and oyster catches have met with strong resistance from watermen who are struggling to survive economically in a declining fishery.

The planned introduction of a non-native Asian oyster (Crassostrea ariakensis ) by the Virginia Seafood Council, raised hopes that a new oyster fishery could be built around the harvest of this disease-resistant, fast-growing species. In May 2002, the United States Fish and Wildlife Service called for a moratorium on the introduction of the Asian oyster, until researchers could determine whether its introduction would endanger native species, or bring new and deadly disease organisms into Chesapeake Bay. A study by the National Academy of Sciences was commenced in 2001 with the goal of making information on these concerns available in summer of 2003.

As of 2002, portions of Chesapeake Bay and its tributaries were still listed as impaired waters under Section 303(d) of the Clean Water Act , but progress on arresting the decline of environmental quality of Chesapeake Bay and restoring some of its natural resources continued. In the Chesapeake 2000 Bay Agreement (C2K), Maryland, Pennsylvania, Virginia, and the District of Columbia, together with the Chesapeake Bay Commission and the Federal Government committed to "correct the nutrient- and sediment-related problems in the Chesapeake Bay and its tidal tributaries sufficiently to remove the Bay and the tidal portions of its tributaries from the list of impaired waters under the Clean Water Act." This consortium of stakeholders, jurisdictions, and federal agencies is evidence that citizens, government, and industry can work cooperatively. The Chesapeake Bay program is a national model for efforts to restore other degraded ecosystems.

[William G Ambrose Jr. and
Paul E Renaud and
Marie H. Bundy ]

RESOURCES

BOOKS

Brown, L. R. "Maintaining World Fisheries." In State of the World, edited by L. Starke. New York: Norton, 1985.

Majumdar, S., et al. Contaminant Problems and Management of Living Chesapeake Bay Resources. Easton, NJ: Typehouse of Easton, 1987.

PERIODICALS

D'Elia, C. "Nutrient Enrichment of the Chesapeake Bay." Environment 29 (1987): 6-11.

ORGANIZATIONS

Chesapeake Bay Foundation, Philip Merrill Environmental Center, 6 Herndon Avenue, Annapolis, MD 21403 410/268-8816, Email: http://www.cbf.org/about_cbf/contact_us.htm