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Condition of the Mid-Atlantic Estuaries
1998. U.S. Environmental Protection Agency, Office of Research and Development, Washington, D.C. 20460 EPA/600/R-98/147
Overview
Estuaries are transitional zones where salt water from the sea mixes with fresh water flowing off the land. They provide habitat for many birds, mammals, fish and other aquatic life. Therefore, estuaries are important assets that humans use in a wide variety of ways. This report focuses on the current condition of the Mid- Atlantic estuaries from the early- to mid-1990s, and how and why the estuaries have changed over the years. The Mid-Atlantic estuaries included in this report are: the Delaware Estuary, the Chesapeake Bay, and the Delmarva coastal bays. The water quality conditions of the Mid-Atlantic coastal waters are also discussed.
Condition of the Mid-Atlantic Estuaries was prepared by scientists from EPA 's Office of Research and Development, National Health and Environmental Effects Research Laboratory, Narragansett, Rhode Island, in collaboration with individuals from EPA Regions II and III and numerous other EPA offices; the states of Maryland, Virginia, and Delaware; the National Oceanic and Atmospheric Administration; the U.S. Geological Survey; and the U.S. Fish and Wildlife Service. It represents the synthesis of information published in a variety of independent scientific reports or contained in established scientific databases. Numerous research studies have been prepared by Federal and state programs and by academic researchers for individual states or watersheds; however, a comprehensive report including water quality, sediment contamination, habitat change, and the condition of living resources had never been done on a regional scale. Data from across all Federal and state programs have been used and comparisons of one estuary to another (and in the case of water quality, the coastal waters) within the Region have been made. The report not only identifies specific geographic problem areas, but estimates the percentage of estuaries that are in good condition, are in moderate condition, or are degraded based on various water quality parameters.
Environmental Challenge
Estuaries in the Mid-Atlantic Region are being adversely affected by human activities. They need active management if environmental quality is to be sustained. The states, in conjunction with EPA through the Chesapeake Bay Program and the National Estuary Programs, have instituted successful environmental management programs to address these environmental challenges, but this work must be continued and expanded if the goals established for the future are to be met. The Mid-Atlantic Region has experienced some of the most rapid population growth, industrial growth, and intensive agriculture in the country. From 1950 to 1990, the population has grown from 13 to 21 million. By 2020 an estimated 25 million people will be living in the estuarine watershed of the Mid-Atlantic Region. This growing population will require land for homes, transportation, shops, jobs, and recreation. Urban land currently comprises 5% of the region's watershed and is close to the estuarine shoreline. As watersheds become more developed, the amount of impervious surface area increases, the amount of pollutants carried in the storm-water increases, and the amount of wastewater and solid waste requiring disposal increases. Additionally, increased population puts increased pressure on the living resources.
Major Findings
- The Chesapeake Bay is the estuary most deficient in oxygen in the region. Impacts to the Bay are associated with nutrient over-enrichment and the lack of oxygen. Excessive nutrients during the 1970s and 1980s contributed to prolonged algae blooms, which decrease oxygen and clarity of the water. This resulted in massive losses of submerged aquatic vegetation (SAV), which is critical habitat for animal life in the bay spawning fish, crabs, etc. Nutrient levels are declining in response to improved wastewater management practices, implementation of best management practices on agricultural lands (nitrogen), and bans on certain types of detergents (phosphorus). The reduction in nutrients has resulted in partial recovery of the SAV beds. There has been more success in controlling point sources than controlling non-point sources of nutrients.
- The Delaware Estuary is impacted by the lack of water clarity and toxic contaminants associated with urbanization and industrialization. Its waters exhibit some of the highest concentrations of nutrients measured anywhere in the world, although harmful phytoplankton blooms are held in check by other factors including low water clarity. The Delaware Estuary also has one of the highest levels of chemical contaminants in fish and shellfish in the nation. Portions of the estuary have bans or advisories on consumption of finfish due to elevated polychlorinated biphenyl (PCB) concentrations. Chlordane levels that exceed the U.S. Food and Drug Administration action level have also been reported.
- The Delmarva coastal bays are the least degraded systems in the Mid-Atlantic Region, but are threatened by encroaching urbanization. These bays are moderately enriched by nutrients, particularly in Delaware, largely from agricultural sources. Eutrophication is increasingly noticeable in the dead- end canals along shorelines in the Delmarva coastal bays. SAV has historically been absent from the Delaware coastal bays due to high natural turbidity. The composition of shore zone fish species in the Delaware coastal bays indicates impacted environmental conditions. In contrast, the fish species in Maryland's coastal bays suggest a healthy habitat; researchers have, however, observed evidence of early stages of degradation in the northern areas.
- The coastal waters currently exhibit low levels of nutrients and chlorophyll. However, evidence suggests that these levels may be rising, indicating the potential for future environmental problems.
- Oyster harvests have declined from a high of 133 million pounds in 1880 to today's annual catch of about one million pounds. Disease, specifically Dermo and MSX, appears to be one of the major causes of the recent drastic decline in the oyster populations in the Chesapeake Bay and the Delaware Estuary, with over-harvesting and pollution also playing major roles in the Chesapeake Bay. Although no immediate solution to the problem is known, researchers currently are working on the concept of introducing disease-resistant strains of oysters to the Mid-Atlantic.
- The most important shellfish industry in the Mid-Atlantic Region is now the blue crab. However, the significantly increased fishing pressure on this already heavily exploited resource is beginning to take its toll. To avoid a serious impact, both Maryland and Virginia have placed restrictions on crabbing in Chesapeake Bay waters.
- Massive fish kills of menhaden in upper Chesapeake Bay in the late 1980s were attributed to a bacterial infection combined with high water temperature. These specific conditions have not been repeated in the 1990s. However, fish kills in this area of Chesapeake Bay attributed to disease and low dissolved oxygen due to a combination of over-enrichment and large numbers of fish entering small bays have continued into the 1990s. During the summer of 1997, a number of fish kills occurred in several small tributaries of Chesapeake Bay and the coastal bays. It was determined that these kills were caused by the toxic dinoflagellate Pfiesteria. Pfiesteria is not a disease, but an organism that is part plant and part animal, and occurs naturally from the Gulf of Mexico to the Delaware Estuary. A large number of research projects are currently underway to better understand this organism.
Obtaining the Report
To order copies of Condition of the Mid-Atlantic Estuaries, publication no. EPA 600-R-98-147, call EPA Region III's Community Based Assessment Team at 410-573-2749 (after January 1999, 410-305-2749).