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Overview of the U.S. Geological Survey Chesapeake Bay Ecosystem Program

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The ecosystem of the Chesapeake Bay (fig. 1) has been adversely affected by a combination of nutrient enrichment, toxic substances, sediment, and overharvesting of shellfish and finfish. Excessive nutrient inputs have caused eutrophication and periods of hypoxia (dissolved-oxygen concentrations lower than 1.0 milligram per liter), which in turn have killed and stressed living resources in many areas of the bay. The algal blooms from high nutrient inputs and sediment loads also decrease water clarity, which is largely responsible for the decline of submerged aquatic vegetation (SAV). Submerged aquatic vegetation, one of the most important components of the ecosystem, provides critical habitat for shellfish and finfish and food for waterfowl. Finally, fish health is threatened by toxic dinoflagullates which may be related to adjacent land-use practices.

In 1987, the Chesapeake Bay Program (CBP), a multiagency restoration effort, established a goal to reduce controllable nutrient loads into the estuary 40 percent by the year 2000. The goal was based on the results of a computer model, that indicated a 40-percent reduction in nutrient loads would eliminate hypoxia in the mainstem of the bay. The nutrient-load reduction is expected to decrease the severity of algal blooms in the tributaries and encourage the regrowth of SAV. However, resource managers are concerned that the bay and watershed will respond more slowly to the nutrient-reduction measures than was previously anticipated. Therefore, scientific information on lag times between nutrient inputs and water-quality and living-resource response, is needed to assess the effectiveness of nutrient-reduction strategies. Analysis of long-term biological, chemical, and hydrogeologic records integrated with new collected information can help managers gain a perspective on the bounds of inherent variability of the ecosystem and its effect on restoration goals. The U.S. Geological Survey (USGS), through its Ecosystem Program, collects and interprets scientific information to help resource managers determine the success of management strategies and the response of the ecosystem to nutrient reduction.

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Figure 1
Location of Chesapeake Bay watershed and major river basins.
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Program Objectives

The primary objectives of the USGS Chesapeake Bay Ecosystem Program are to: (1) Determine the response of water quality and selected living resources of the bay watershed and estuary to changes in nutrient and sediment inputs and climatic variability over several temporal scales. The time scales are: the recent past (1-15 years), which encompasses the timeframe for many management actions; the last five decades, which is the timeframe for increased nutrient inputs; and the last four centuries, which is the timeframe needed to assess the impact of population increase.

(2) Further define and evaluate the natural and anthropogenic controls on the response in water quality and selected living resources to changes in nutrient and sediment sources and climatic variability.

(3) Provide resource managers with the management implications of the scientific findings and develop investigative tools so they may evaluate the effectiveness of different nutrient-reduction strategies.

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Study Design

The USGS Chesapeake Bay Ecosystem Program, which began in May 1996, is a 5-year effort to provide relevant information on nutrient and sediment conditions and response times and the factors affecting nutrient and sediment dynamics and selected living resources for the re-evaluation of the nutrient-reduction strategy in 1997 and the final assessment in the year 2000. Existing nutrient and sediment data for the entire watershed will be utilized to document and further understand conditions in the watershed. Detailed investigations are designed to clarify the principal factors affecting nutrient and sediment transport and their relation to the changes in the sources of these constituents in selected hydrogeomorphic regions (HGMR’s) of the watershed (fig. 2). HGMR’s are areas of unique physiography and rock type that may have characteristic water-quality and biological response to natural variability and changes in nutrient inputs. USGS will relate surface and subsurface characteristics to water quality and living-resource response over several temporal scales through studies in selected watersheds, and river and estuary reaches within HGMR’s.

Through the Ecosystem Program, USGS brings together a team of investigators from relevant complementary disciplines. The investigators coordinate with members of more than 12 programs within the USGS, and scientists and resource managers within the Chesapeake Bay Program.

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Figure 2
Chesapeake Bay basin with major hydrogeomorphic regions.
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Major Elements of the USGS Chesapeake Bay Ecosystem Program

Element 1: Collect, compile, and manage cartographic and associated data sets.

Cartographic, geographic, and associated data are needed to document and evaluate environmental conditions that most affect nutrient and sediment occurrence and selected living resources in the Chesapeake Bay watershed and estuary.

Highlights of Efforts

The Ecosystem Program prepares or enhances detailed spatial coverages of the bay watershed for land characteristics (topography, hydrography, drainage divides, physiography, land cover, and soil), subsurface characteristics (geology and lithochemistry), and estuarine characteristics (bathymetry and shoreline changes). A new satellite-image mosaic of the watershed has been prepared using data developed by ongoing efforts of the USGS and other agency programs. Additionally, a temporal land-use change study is designed to show the influence that agricultural, urban, and forest land-use change over the past 200 years has had on nutrient and sediment input into the Patuxent River Basin and on water quality and living resources. Information on nutrient inputs is being compiled as part of this effort. Data-management tools will be developed to provide access to and interpret the information compiled and generated under the Program. Within USGS, the Program is working with the National Mapping Division to obtain detailed characteristics of more localized areas through production of Digital Orthophoto Quadrangles.

Element 2: Further define the factors that affect the sources, sinks, transport, and residence time of nutrients and sediments in major areas that drain into the Chesapeake Bay and their relation to the estuary.

The river basins in the watershed have been identified as the major source of nutrients and sediments to the estuary. The success of the nutrient- and sediment-reduction practices implemented in the watershed will depend on an improved understanding of the factors affecting input and transport of nutrients and sediments.

Highlights of Efforts

The Ecosystem Program will provide information about the occurrence, trends, and transport of nutrients and sediments in the watershed and update an existing USGS data base. Initial information on nutrient and sediment budgets will be compiled from existing studies. Information on nutrient and sediment retention and transport will be collected by conducting field efforts in selected watersheds in different HGMR’s and the Susquehanna River reservoir system. Statistical analysis and regression modeling will be used to assess the relation of water-quality response to nutrient inputs and surface and subsurface characteristics of the watershed. The Ecosystem Program will be coordinating with several other USGS efforts including the River Input project, the National Water-Quality Assessment (NAWQA) Program, the National Research Program (NRP), and District offices to obtain and interpret data on nutrient occurrence, trends, and loads.

Element 3: Quantify the nutrient load entering the Chesapeake Bay from ground water and identify the effect of residence time of nutrients in the ground-water system on water-quality response in the rivers and the bay.

Assessment of the residence time of nutrients in the ground-water system helps managers to understand the lag time between nutrient-reduction actions and water-quality response. A better understanding of the factors controlling nutrient movement and concentration will help resource managers more effectively target the placement of nutrient-reduction measures.

Highlights of Efforts

The Ecosystem Program will document the quantity of ground water and associated nitrogen loads entering the bay and the residence time of nitrogen in the ground-water system. Hydrograph-separation techniques will be used to determine the amount of ground-water discharge to rivers entering the bay. Water samples have been collected from springs and wells to document ground-water ages and chemistry. These data and information on subsurface characteristics will be used to better understand the factors affecting traveltime and nutrient concentration in the different HGMR’s. Statistical analysis will be conducted to determine the strongest influences on nutrient movement and concentration. Studies in more localized areas will be conducted to confirm the results of the statistical analysis. Within USGS, information on discharge of ground water to the bay will be collected through coordination of the USGS Delmarva study unit of the NAWQA Program and evaluation of geologic properties through a coordinated effort with the Cooperative Geologic Mapping Program.

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Element 4: Improve the understanding of the hydrologic, geologic, and water-quality factors affecting selected living resources and their associated habitat in the rivers, tidal tributaries, and estuary.

Understanding the response of living resources and associated habitat to water-quality improvements is one of the primary objectives of the nutrient-reduction goal and tributary strategies. In the tidal system, SAV is expected to respond favorably to improved water clarity and quality. Additionally, understanding the link between land use, nutrients, and fish health is needed in the bay system.

Highlights of Efforts

The Ecosystem Program will document the response of SAV in areas of selected tidal rivers where the habitat requirements for SAV have been meet, but SAV has not yet returned to the system. At selected sites in the tidal portion of the Potomac River, USGS will transplant SAV to evaluate the factors affecting its response and use this information to update SAV habitat requirements. Data collected in the nontidal portion of the watershed will be used to study the occurrence and change of algal and other selected biological communities due to changes in water quality and other environmental conditions. Within USGS, the Biological Resources Division will also be participating in study efforts to identify the causes of fish lesions and kills and their relation to land use, nutrients, and fish health.

Element 5: Study the history and evolution of the Chesapeake Bay ecosystem and its response to changes in sedimentation, salinity, and nutrient loading during the past several decades and centuries.

Investigating the depositional history of the bay will help describe the condition of the bay’s ecosystem prior to human development and improve our knowledge of present conditions. Understanding the influence of climatic cycles on freshwater flow, fluctuations in the bay’s hydrology, nutrients, dissolved oxygen, salinity, sedimentation rates, and biodiversity will help determine the extremes of natural fluctuations and their relation to restoration goals.

Highlights of Efforts

The Ecosystem Program is part of a multiagency effort to carry out an integrated coring, sedimentological, environmental, and ecological investigation of the bay’s ecosystem. The USGS will examine the response of biological resources to natural and anthropogenic changes at several time scales, including the last five decades, when nutrient inputs have greatly increased into the bay and the past four centuries, when populations increased. Sediment cores collected from the bay show historical trends in habitats, nutrients, salinity, and sedimentation from age dates, paleoecological proxies (pollen, diatoms, ostracods, foraminiferal ecology), sedimentary geochemical indicators, and chemical analyses of major nutrients. The USGS compares these biological and chemical data to historical records on rainfall, river inflow to the bay, land-use changes, and nutrient inputs to evaluate the causes of changes in the sediment cores. Coordination within the USGS includes working with the Climate Change and Marine and Coastal Geology Programs.

Element 6: Information Dissemination and Outreach. There is a continuing need to translate scientific information into usable results to better manage and restore the bay and its watershed. The USGS is working closely with the Communications Subcommittee of the Bay Program and the Alliance for the Chesapeake Bay to relay our scientific results to State and local government resource managers in the bay watershed, program managers in the USGS and the Department of the Interior, scientists, the media, and the general public. The USGS disseminates information through a series of mechanisms including a Home Page on the World Wide Web, fact sheets and reports, press releases and media events, pilot projects with Tributary Strategy Teams, and presentations to agencies and scientists at selected meetings and conferences.

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Figure 3
Organizational Chart
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USGS Partnerships

The Ecosystem Program has active partnerships with other agencies and research institutions involved in the Chesapeake Bay restoration effort. Collaboration with other agencies includes having USGS representatives on all the major subcommittees and related workgroups in the CBP (fig. 3).

Selected partnerships under Element 1 include evaluation of land-use characteristics being coordinated through the Multi-Resolution Land Characterization (MRLC) effort with the U. S. Environmental Protection Agency (EPA), National Oceanic and Atmospheric Agency (NOAA), and National Aeronautics and Space Agency. The land-use change study in the Patuxent River Basin is being conducted with the University of Maryland at Baltimore County. Nutrient-input data are being obtained from the agencies involved with the Nutrient and Modeling Subcommittees of the Bay Program. Data-access and compatibility issues are being addressed with the agencies of the CBP.

The analysis of nutrient trends under Element 2 is being performed in partnership with the agencies involved in the Monitoring Subcommittee including the Susquehanna River Basin Commission, the Maryland Department of Natural Resources (MD DNR) and the Virginia Department of Environmental Quality. Field investigations to better understand ground- and surface-water interactions will use the data and contribute to existing studies being conducted by the MD DNR, Virginia Department of Environmental Quality, Smithsonian Research Institute, and other Federal and State agencies and research groups.

Investigators under Element 3 are working with the State Geological Surveys in the bay watershed to produce a lithogeochemical map, which will aid in understanding the factors affecting nitrogen movement in the subsurface.

For Element 4, the USGS is an active partner with the Potomac River Integrated Study Team (Interstate Commission on the Potomac River Basin and other agencies) to study SAV in the Potomac River and the SAV workgroup of the Bay Program. At the SAV transplant sites, the USGS will be working with the Alliance for the Chesapeake Bay to collect water-quality data. Finally, the Program will coordinate with the MD DNR, EPA and NOAA to find the causes of fish lesions and kills in the bay. USGS investigators share and report their findings to the CBP Living Resources Subcommittee.

Under Element 5, USGS is working with the Maryland Geological Survey and the University of Maryland to collect and analyze cores in the mid and northern bay. In the southern part of the Bay work is conducted in collaboration with the Virginia Institute of Marine Science. Results will be shared with other institutions working on the long-term history of the bay including Johns Hopkins University and agencies represented on the CBP Living Resources Subcommittee.

The USGS is an active partner with the CBP Communications Subcommittee to disseminate information under Element 6 of the Ecosystem Program. Additionally, the USGS will be working with the Alliance for the Chesapeake Bay to develop products for resource managers and the general public.

For further information, contact:

U.S. Geological Survey Chesapeake Bay Coordinator

8987 Yellow Brick Road
Baltimore, MD 21237

Web Page address:

Scott Phillips and Bill Caughron


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