United States Office of Research and EPA 600-R-98-147

Environmental Protection Development November 1998

Agency Washington, DC 20460 www.epa.gov

Condition of the

Mid-Atlantic Estuaries
Watershed of the Mid-Atlantic estuaries
Chesapeake Bay, Delaware Estuary, and Delmarva coastal estuaries are vital Mid-Atlantic resources. They provide

habitat for many kinds of animals and plants, including commercially valuable fish and shellfish, and are enjoyed each

year by millions of recreational boaters, fishermen, and other visitors. For many years, the U.S. Environmental Protection Agency (EPA) has led efforts to protect and restore these estuaries by implementing such laws as the Clean

Water Act and by participating in projects like the Chesapeake Bay Program.

Are these protective measures having an impact? What is the current condition of our natural resources? How

widespread are ecological problems and what are their probable causes? To answer these questions, and to identify

the most effective protection measures for the future, we need to regularly take stock of our natural resources. EPA

is now pursuing these goals by preparing a series of State-of-the-Region Reports for the Mid-Atlantic, of which this

report is the first. These peer-reviewed reports aim to gather and evaluate the best available scientific information and

knowledge about the ecological resources of the region. Future reports will address the condition of our streams,

forests, and other resources.

This report breaks new ground in employing the latest scientific tools and by drawing upon carefully designed sampling

plans that provide broad coverage of all of these estuaries. It also demonstrates the value of forging close scientific

collaboration among federal and state agencies and other organizations. We hope this report will help you understand

more about the estuaries and encourage further efforts to protect these natural treasures.

W. Michael McCabe Henry L. Longest II

Regional Administrator Acting Assistant Administrator

Region III Office of Research and Development

i
This report, Condition of the Mid-Atlantic Estuaries, was prepared by staff from the Atlantic Ecology Division

(AED), National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S.

Environmental Protection Agency, Narragansett, Rhode Island. The staff included John F. Paul, Technical Leader,

Brian Melzian, Technical Coordinator, Barbara S. Brown, Branch Chief, and team members Charles Strobel, John

Kiddon, James Latimer, Daniel Campbell, and Donald Cobb. The report was prepared with the collaboration of individuals from Delaware Department of Natural Resources and Environmental Control, Maryland Department of

Natural Resources, Virginia Department of Environmental Quality, National Oceanic and Atmospheric Administration,

U.S. Geological Survey, U.S. Fish and Wildlife Service, EPA Regions II and III, AED Community-Based Assessment

Team in Annapolis (special thanks to Tom DeMoss, Pat Gant and Ron Landy), Kevin Summers and others from EPA/

ORD Gulf Ecology Division, EPA/ORD Western Ecology Division, Chesapeake Research Consortium, and EPA

Office of Policy, Planning, and Evaluation. Geographic information systems support was provided by Jane Copeland,

Randy Comeleo, and George Morrison, OAO Corporation. We would like to thank William Nelson, Gerald Pesch,

Richard Pruell, Steven Schimmel, Darryl Keith, and Walter Galloway of EPA/AED; Robert Diaz; and Kenneth

Tenore; as well as a large number of other reviewers from government and academia for their valuable reviews of this

document. This report represents the synthesis of information published in a variety of scientific reports or contained

in established scientific databases. We collected no new data specifically for the production of this report. We thank

the many researchers involved in the original collection and reporting of these data.

Because of the vast number of different research projects producing the data used in this report, no attempt was made

to verify the quality of these data. It was assumed that if the data were published or were stored in established

databases that they had been verified. However, any data that appeared unusual or questionable were checked with

the originator of those data. The spatial displays presented in this report were not prepared to meet EPA spatial

locational guidelines; the displays were prepared from disparate datasets and represent a best attempt at approximating

locations.

This report has been reviewed and approved for publication by the U.S. Environmental Protection Agency. Approval

does not signify that the contents necessarily reflect the views and/or policies of the EPA. Mention of trade names,

products, or services does not convey, and should not be interpreted as conveying, official EPA approval, endorsement,

or recommendation.

This report is contribution USEPA-NHEERL-NAR-1822 of the Atlantic Ecology Division of the EPA National

Health and Environmental Effects Research Laboratory.

ii
toxic contaminants associated with urbanization and

industrialization of the Delaware River. The Delaware

Estuary has some of the nations highest levels of

chemical contaminants in fish and shellfish. Fishing

bans or advisories on the consumption of finfish are

posted for parts of the estuary because of elevated

PCB concentrations. Concentrations of Chlordane in

fish exceeding the FDA action level have been reported

in the upper estuary.

Chesapeake Bay continues to be affected by low

dissolved oxygen and is the most hypoxic estuary in the

region. Low dissolved oxygen levels are associated with

Estuaries are transitional zones where salt water from

the sea mixes with fresh water flowing off the land.

Estuaries in the Mid-Atlantic Region provide habitats for

many birds, mammals, fish, and other aquatic life. They

also are important assets that humans use in a wide

variety of ways. This report focuses on the current

condition of the Mid-Atlantic estuaries (circa early to

mid 1990s) and, where information is available, how the

estuaries have changed over the years and why.

The pervasive issues across the Mid-Atlantic Region

include the oyster harvest and disease in shellfish.

Shellfish, particularly the American oyster, traditionally

have been one of the major living resources harvested

in the Mid-Atlantic states. Oyster harvests have

declined from a high of 133 million pounds in 1880 to

todays 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

oyster populations in Chesapeake Bay and the Delaware Estuary, with over-harvesting and pollution also

playing a major role in 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.

With the decline of the oyster industry, the most important shellfish industry in the Mid-Atlantic Region is now

the blue crab. However, the significantly increased

fishing pressure on the already heavily exploited population is beginning to take its toll. To avoid a serious

impact, both Maryland and Virginia have placed restrictions on crabbing in Chesapeake Bay waters.

The Delaware Estuary is characterized by an historical

lack of submerged aquatic vegetation (SAV), due

predominantly to naturally-occurring low water clarity.

It is also one of the most nutrient enriched estuaries in

the world, although harmful phytoplankton blooms are

held in check by other factors, including low water

clarity. The estuary also is highly impacted by lingering

Photo by: U.S. Fish and Wildlife Service

iii
nutrient overenrichment and eutrophication. In 1987, the

Chesapeake Bay Agreement stipulated a 40% reduction

in nutrient loading by the year 2000. Nutrient levels in

Chesapeake Bay 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). However, there has been more success in controlling point sources than nonpoint sources of nutrients.

Historically, high nutrient concentrations have contributed

to prolonged phytoplankton blooms in the Bay. Blooms

during the 1970s and 1980s significantly reduced water

clarity and, as a result, contributed to the massive loss of

SAV that occurred during that time period. This critical

habitat has since partially recovered.

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, particularly in Delaware, largely from agricultural sources. Eutrophication is increasingly noticeable in

the dead-end canals along developed shorelines in the

Delmarva coastal bays. SAV historically has been absent

Executive Summary

from the Delaware portion of the coastal bays because of

high natural turbidity in these systems. Species composition of shore zone fish in the Delaware coastal bays

indicates impacted environmental conditions. In contrast,

Maryland coastal bays species composition suggests a

healthy habitat; however, researchers have observed

evidence of early stages of degradation in northern areas.

Coastal waters presently exhibit low levels of nutrients

and chlorophyll. However, evidence suggests that these

levels may be rising, indicating the potential for future

environmental problems.

Estuaries of the Mid-Atlantic Region are being adversely affected by mans activities. Therefore 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.

Photo by: U.S. Fish and

Wildlife Service

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Greetings from the U.S. Environmental Protection Agency ..........................i

Acknowledgements ..........................................................................................ii

Executive Summary....................................................................................... iii

INTRODUCTION ................................................................................................... 1

Most of the Mid-Atlantic Regions population is concentrated along the coast, and that places a great deal of

pressure on the protected areas where freshwater from rivers mix with seawaterour estuaries.

DESCRIPTION OF THE ESTUARINE RESOURCE ...................................................... 3

The Mid-Atlantic Region contains a significant portion of the United States estuaries. The physical characteristics of

these estuaries are important factors in understanding their ecological condition.

WATER QUALITY ................................................................................................. 9

Many areas in the Mid-Atlantic Region are overfed by nutrients such as nitrogen and phosphorus.

Increased levels of nutrients from activities such as land clearing, fertilizer application and runoff, and sewage

discharges can lead to excessive vegetation, algal blooms, and low levels of dissolved oxygen.

Nutrients.................................................................................................................................................... 9

Phytoplankton .......................................................................................................................................... 11

Dissolved Oxygen .................................................................................................................................... 12

SEDIMENT CONTAMINATION .............................................................................. 15

Chemical contaminants from a variety of point and nonpoint sources enter our estuaries and accumulate in

the sediments, adversely affecting bottom-dwelling organisms and the fish and shellfish that feed on them.

vi
HABITAT CHANGE............................................................................................... 17

Developmental pressures have resulted in substantial habitat change in the Mid-Atlantic. Coastal Wetlands have

been destroyed for residential and commercial development. The submerged aquatic vegetation, which provides

food, shelter and nursery grounds for many species of shellfish, finfish, and other organisms, has decreased as

human population has increased.

Coastal Wetlands ..................................................................................................................................... 17

Submerged Aquatic Vegetation ................................................................................................................. 18

CONDITION OF LIVING RESOURCES .................................................................... 19

Fish and other aquatic life are often the first affected by the substances deposited in our waterways. Since they are

also consumed by people, the condition of our living resources is a significant public health concern.

Benthic Condition ..................................................................................................................................... 19

Shellfish Harvest....................................................................................................................................... 21

Shellfish Closures ..................................................................................................................................... 23

Fish Stock Assessment............................................................................................................................. 25

Contaminants in Fish and Shellfish............................................................................................................. 28

Incidence of Disease ................................................................................................................................ 29

Waterfowl ................................................................................................................................................ 31

Threatened and Endangered Species ........................................................................................................ 33

SUMMARY ......................................................................................................... 36

SOURCES OF INFORMATION................................................................................ 40

GLOSSARY ......................................................................................................... 44

TECHNICAL APPENDIX: Criteria Used for Presenting Indicator Data............ 48

vii

Contents
A broad-scale view of the Mid-Atlantic Region1 of our

country reveals that local ecological resources such as

water supplies and wildlife do not exist as isolated groups

but are interconnected across long distances. The health of

blue crabs in Virginia or waterfowl in Delaware can be

affected by conditions dozens or even hundreds of miles

away. Therefore, studying and protecting ecological resources must take a similarly broad view. EPA is working to

implement just such an approach through its Office of

Research and Development and the Region III Office,

which is based in Philadelphia and encompasses the District

of Columbia and the states of Delaware, Maryland, Pennsylvania, Virginia, and West Virginia.

In this report, the first in a series of State of the Region

reports, we present information on estuaries in EPA Region

III, which includes Chesapeake Bay, the Delaware Estuary,

and the coastal bays on the Atlantic coast in the states of

Delaware, Maryland, and Virginia (Delmarva Peninsula).

To properly assess the ecological condition of Region

IIIs estuaries, one must look at more than just the water

bodies themselves. The entire watershed must be

studied, meaning all the land that drains into these

estuaries. For this reason, this report uses information

extending beyond the political bounds of EPA regions,

treating the estuaries as ecological units rather than

political entities.

Information in this report will be presented primarily as

percent of the estuarine area in some desired or undesired

condition, rather than the actual area (square miles). This

will allow easier comparison between subregions. For

example, questions like Is more of Chesapeake Bay in an

undesired condition than the Delaware Estuary? will be

addressed. If area estimates were compared, Chesapeake

Bay would dominate almost all comparisons because of its

size (81% of the estuarine surface area in the region). The

actual areas can be compared by multiplying percent area

by the areas given in the next chapter.

What are estuaries?

Estuaries are transitional zones where salt water from the

sea mixes with fresh water flowing off the land. For this

report we will use the term estuaries to include waters that

extend from the coast of the Atlantic Ocean (or boundaries that extend across the mouths of the Delaware

Estuary and Chesapeake Bay) upstream to the fresh

waters that drain to the ocean as far as the influence of

the tide is detectable. For rivers like the Susquehanna, this

tidal influence is limited to the first dam encountered as

one goes upstream. For others, such as the Delaware and

Potomac Rivers, the tidal influence can extend many miles

upstream to the fall line. The salinity of estuaries can

range from full strength sea water to brackish to fresh

water. When we discuss the condition of estuaries, we

mean the condition of the waters that span this full range

of salinities.

1

Terms in the glossary are highlighted at first usage.

Photo by: Chesapeake Bay Program

1
Why are estuaries important?

Estuaries are valuable in many ways. They provide

important habitat for thousands of species of plants and

animals. As spawning, nursery, and feeding grounds,

they are invaluable to fish and shellfish. These waters

provide corridors for anadromous fish that migrate

upstream to spawn.

Estuaries support many kinds of natural habitats, including

wetlands. Wetland habitats are used by shorebirds,

migratory waterfowl, fish, invertebrates, reptiles, and

mammals. They are the home to many threatened or

endangered species. Wetlands also improve water

quality by filtering out pollutants and sediment, and serve

as buffers that protect upland areas from flooding. They

also stabilize shorelines and stream banks from erosion.

In addition to their biological and habitat value, estuaries

provide for many diverse human uses. They supply water

for municipalities, industry, and agriculture; support

commercial and sport fisheries; and support tourism and

recreation. They also are important locations for manufacturing and shipping. Finally, estuaries are valued for

their aesthetic qualities.

How are estuaries threatened?

Estuaries are threatened because of the numerous ways

that humans use them and the land area that drains into

them. As a result, they exhibit a multitude of environmental problems. The most common problems

degraded natural habitats, declining plant and animal

populations, diminishing fish and shellfish harvests, and

impaired water qualityare clearly observable in parts

of the estuaries in the Mid-Atlantic Region. Growth of

human populations in the estuarine watersheds, combined

with the spread of industrial and agricultural technologies

that are potentially harmful to ecological systems and

place greater demands on natural resources, has adversely affected our valuable estuarine ecological

systems. Most of the problems observed in estuaries are

related to land use practices and are closely linked to

human population density. The northeast corridor

extending from Washington to Boston, of which the MidAtlantic is part, is one of the most densely populated

areas of our country.

What dynamics occur

in estuaries?

This report is an accounting of our estuarine resources at

the present, which are, in part, the legacy of our past

actions. Our description of these resources is a snapshot of estuarine conditions in the Mid-Atlantic Region

based upon currently available information. However, we

know that ecological systems adapt and evolve with time

under the influence of external factors, that also change

through time. This dynamic aspect of ecological systems

is not the subject of this report. Nevertheless, it is the

context within which this report is presented, and the

present ecological conditions are the basis upon which

management decisions about the future will be made.

Estuaries in the Mid-Atlantic Region are expansive and

dynamic systems, consisting of physical and chemical

environments, and living creatures. The fresher and

saltier waters in estuaries are constantly intermingling

with the rivers, ocean waters, the shoreline, and the air,

all of which are changing with the tides and seasons.

These natural mixing bowls of physical, chemical, and

biological interactions, combined with the myriad of

human uses, challenge our ability to understand and

manage these great natural resources. We have attempted in this report, to summarize our current

understanding of how well estuaries as

a whole are doing in the Mid-Atlantic

Region.

Introduction

Estuaries are home to a wide variety of wildlife.

Photo by: U.S. Fish and Wildlife Service

2
A discussion of the characteristics of estuaries in the MidAtlantic Region provides a useful starting point. The

estuarine waters in the Mid-Atlantic Region encompass

approximately 5,467 mi2

 of surface area. These estuarine

waters contain a significant amount of the estuarine area in

the United States; Chesapeake Bay is the single largest

estuary in North America. The estuarine areas for the

major natural subregions discussed in this report are 4,431

mi2

 for Chesapeake Bay, 795 mi2 for the Delaware Estuary, and 237 mi2

 for the Delmarva

coastal bays.

What land areas do the

estuaries drain?

The estuaries of the Mid-Atlantic Region drain

78,859 mi2

 of land area, with 65,712 mi2 of these

watersheds residing within the EPA Region III

state boundaries. Chesapeake Bay drains a

watershed of 64,325 mi2

, the Delaware Estuary

drains 13,533 mi2

, and the Delmarva coastal bays

drain 1,003 mi2

. About 43,710 mi2 of western

Region III in the mid-Appalachian area do not

drain to the Atlantic Ocean. This land area

primarily drains to the Ohio and Tennessee

Rivers and Lake Erie. Runoff from these land

areas does not directly affect the Mid-Atlantic

Estuaries; however, transport by the atmosphere from these land areas can influence the

estuarine drainage areas. Approximately 10,629

mi2

 in southern Virginia drain to the AlbemarlePamlico estuarine system in North Carolina. This

land area also does not directly affect the MidAtlantic estuarine waters.

How are the estuarine

watersheds used?

The use of land within watersheds is a basic factor in

understanding the ecological condition of the Mid-Atlantic

estuaries. A pictorial representation of the land cover is

shown in Figure 1. This figure displays the major land

Figure 1. Land cover for estuarine

watersheds in the Mid-Atlantic

region.

Source: Vogelmann, 1997

3
cover categories (urban, forests, agriculture, wetlands, and

lakes and streams) as classified by the U.S. Geological

Survey. Figure 2 summarizes these land cover categories

for the region and subregions. Note that the Delaware

Estuary watershed is the most urbanized and that the land

cover distribution in the Delmarva coastal bays is distinctly

different from the rest of the region.

For the region, forest is the dominant land cover category,

comprising 61% of the watershed area. Forests are

important because trees filter sediment and nutrients

from runoff, and their roots stabilize the shoreline and

reduce erosion. They also shade the water, reducing

summer water temperatures. Many of the Mid-Atlantic

forests are in areas distant from estuarine shores. In

some parts of the region, forests are

rapidly being replaced by agricultural

and urban lands.

Agricultural land comprises two

groupingspasture and cropland.

Pasture land consists of grassy areas

for raising and feeding livestock.

Cropland is cultivated to provide

various food products. Approximately

one-third of the land in the region is

agricultural.

Urban land (5% of the watershed)

generally is close to the estuarine

shoreline (see Figure 1). Urban land

provides space for homes, roads, and

places of employment, and increases

the amount of impervious surface

area (for example, pavement) and

storm water runoff. As a watershed

becomes more developed, the amount

of pollutants carried in the storm water increases, as does

the amount of wastewater and solid waste requiring

disposal. The storm water flows in urban and developing

areas also cause habitat damage and destruction. It is

expected that the amount of urban land will continue to

increase across the region.

What does the population

distribution look like?

Population growth is the single most important factor

underlying various impacts on Mid-Atlantic estuaries.

The population has grown from 13 million residents in

1950 to 21 million in 1990 (Figure 3). By 2020 an

estimated 25 million people will be living in the estuarine

watershed of the Mid-Atlantic Region. Growing

Figure 2. Land cover categories in the Mid-Atlantic Region

estuarine watersheds.

Source: Vogelmann, 1997

Description of the Estuarine Resource

Figure 3. Human population estimates for the

Mid-Atlantic estuarine watershed.

Source: Culliton et al., 1990

Nearly three out of every ten acres in the

Mid-Atlantic watershed is currently being used

for agriculture.

Photo by: Chesapeake Bay Program

4
population requires land for homes, transportation,

shops, jobs, and recreation. Forests and other land of

environmental significance often are converted to meet

these needs. In addition to changes in land use, population growth results in high flows from wastewater

treatment plants. The volume of discharge by wastewater treatment plants has increased with the general

population trend. Nevertheless, efforts to protect

estuaries, such as improving wastewater treatment,

maintaining buffer zones around estuaries, and controlling pollutant runoff, can offset or even reverse some of

the impacts of growing populations.

What characterizes estuaries in

the Mid-Atlantic Region?

A schematic description of a typical estuary is shown in

Figure 4. The depth of the water is a basic parameter

that influences the type of plants and animals that can

inhabit the estuary. Shell fisheries usually are limited to

relatively shallow areas. Plants rooted in the bottom

sediments also require shallow depths. Large migratory

fish typically require deeper water for their excursions.

Large draft vessels are restricted to deeper portions of

estuaries or to dredged channels. Water depth also

influences circulation in the estuary, which in turn

determines the distribution of nutrients and pollutants.

Vertical stratification, or layering of waters of different

density, occurs in an estuary when colder, saltier water

underlies warmer and fresher water. This condition can

be sustained only in deeper waters because wind and

tidal motions usually are sufficient to keep shallow

water from stratifying. Stratification, which occurs in

the mainstem of Chesapeake Bay and lower portions of

the major tidal tributaries, isolates the deep layer of

water from the atmosphere. As dissolved oxygen in

this deep layer is depleted by decaying organic material

(dead algae that sink after peak production), stratification does not permit replenishment of the dissolved

oxygen from the atmosphere. This leads to the extremely low oxygen levels observed in these deeper

waters. A description of dissolved oxygen conditions

across the region is presented in the next chapter.

Salinity, temperature, and depth are the primary factors

that affect the physical behavior of estuarine waters.

Warmer, lighter freshwater flows seaward over a layer

of saltier and denser water flowing in from the ocean.

This stratification varies within any season depending on

the rainfall and air temperature. Stratification usually

intensifies in the spring as the amount of freshwater

increases due to melting snow and frequent rain.

Stratification is maintained through the summer due to

Description of the Estuarine Resource

Figure 4. Schematic diagram of physical, chemical, and biological processes interacting in estuaries.

Source: Redrawn from USEPA, 1987

5
warming of surface waters and intense rainfall. Maximum reductions of dissolved oxygen in estuarine bottom

waters occur during the late summer (see section on

Dissolved Oxygen). In autumn, fresher surface

waters cool faster than deeper waters and sink. Vertical

mixing of the water layers occurs rapidly. This mixing

moves nutrients up from the bottom sediments, making

them available to phytoplankton and other organisms

inhabiting the upper water levels. This turn-over also

distributes much-needed dissolved oxygen to deeper

waters. During the winter, water temperature and salinity

are relatively constant from surface to bottom.

The degree of water column stratification is determined

by the difference in density between surface and bottom

water, and categorized by low, moderate, and high

stratification. Summer data on stratification are depicted

in Figure 5. Most estuarine waters in the Mid-Atlantic

Region exhibit little or no stratification. However, deeper

portions of Chesapeake Bay do become highly stratified.

The Delaware Estuary has areas of moderate stratification, while Delmarva coastal bays typically are not

stratified due to their shallow depths.

The average depth of estuaries in the Mid-Atlantic

Region is 20 ft, with a maximum of 175 ft in the

mainstem of the Chesapeake Bay. The average depth

in Chesapeake Bay is 20 ft, 19 ft in the Delaware

Estuary, and 5 ft in Delmarva coastal bays. The

maximum depth in the Delaware Estuary is 148 ft in a

shipping lane, while in Delmarva coastal bays it is

approximately 115 ft at the Indian River Inlet.

Temperature dramatically changes the rate of chemical

and biological activity within estuarine waters. Because

the estuaries in the Mid-Atlantic Region are relatively

shallow, their capacity to store heat over the year is

relatively small. As a result, water temperature fluctuates throughout the year, ranging from 320 to 840

 F.

These water temperature changes influence when plants

and animals feed, reproduce, move locally, or migrate.

The density of water is dependent on temperature, as

well as salinity. In spring, as the air temperature rises,

the surface waters of the estuaries warm and become

stratified over the colder, heavier deeper waters. Air

motion, particularly during storms, can vertically mix

water. However, in deeper portions of Chesapeake Bay

and the Delaware Estuary, this mixing is restricted to the

upper portion of the water column.

Salinity is a measure of the total salt content in water.

The common measurement unit of salinity is concentration, usually expressed as parts per thousand (ppt)the

Description of the Estuarine Resource

Figure 5. Summer water column stratification

in Mid-Atlantic estuarine waters as observed in 1990-

93. Categories are low (green), moderate (yellow),

and high (red) stratification and are defined in the

technical appendix.

Sources: Strobel et al., 1995; Paul et al., 1997

Photo by: U.S. Fish and Wildlife Service

6
number of grams of dissolved salts in 1,000 grams of

water. Salinity measurements in estuarine waters range

from less than 0.5 ppt in fresh water to 5 ppt in brackish

water to 33 ppt in coastal ocean water. Because fresh

water contains fewer salts, it is lighter (less

dense) than sea water, and tends to remain

at the surface in a stratified estuary.

Salinity distribution in the Mid-Atlantic

estuarine waters during the summer is

summarized by three salinity categories:

salinity less than 5 ppt (oligohaline waters),

between 5 and 18 ppt (mesohaline waters),

and greater than 18 ppt (polyhaline/euhaline

waters). Bottom water salinity data for the

summer is depicted in Figure 6. Oligohaline

waters represent a small fraction of the

estuarine area of the region. Mesohaline

waters are dominant in Chesapeake Bay, while the

Delaware Estuary and Delmarva coastal bays are

mostly polyhaline waters.

Sediments are the materials deposited on the bottom of

the estuary. They are comprised of sand, silt, and clay.

The silt-clay (mud) content of sediments (less than 63

microns or 0.0025 inches particle diameter) is an

important factor determining the composition of the

biological community that inhabits the bottom sediments

in estuaries. Although sediments are a natural part of

estuarine ecosystems, accumulation of excessive

amounts of sediments is undesirable. Accumulated

sediments can fill in ports and waterways. Sediments

suspended in the water column cause the water to

become cloudy, or turbid, decreasing light available for

plant growth and animal feeding. Further, as suspended sediments settle to the bottom, the sediments

can smother bottom-dwelling plants and animals.

Sediments also can carry pollutants. Smaller or finegrained sediment particles (silts and clays) have a

relatively large surface area. Many pollutant molecules

easily adsorb, or attach, to small particles. As a result,

fine-grained sediments can adsorb metals, nutrients, oil,

pesticides, and other potentially toxic substances.

Thus, areas of fine-grained sediments can contain high

concentrations of sediment-bound pollutants.

Description of the Estuarine Resource

Figure 6. Summer salinity distribution in

Mid-Atlantic bottom estuarine waters as observed

in 1990-93. Categories are oligohaline (green),

mesohaline (yellow), and polyhaline/euhaline (red).

Sources: Strobel et al., 1995; Paul et al., 1997

An example of a plume of water, heavily

laden with suspended sediments,

entering an estuary.

Photo by: Chesapeake Bay Program

7
Description of the Estuarine Resource

Estuarine sediments are summarized by three categories: sediment with silt-clay content less than 20%

(sand), silt-clay content between 20% and 80% (mix),

and silt-clay content greater than 80% (muds). Sand is

the primary sediment category found across estuaries in

the region. The Delaware Estuary is dominated by

sandy sediments, while Chesapeake Bay and the

Delmarva coastal bays have a relatively uniform split

across the categories. However, the estuaries tend to

be sandier near their openings to the coastal ocean.

Clear waters are valued by society and contribute to the

maintenance of healthy, productive biological communiFigure 7. Summer water column clarity in

Mid-Atlantic estuarine waters as observed in 1990-93.

Water clarity categories are poor (red), fair (yellow),

and good (green) and are defined in text and technical

appendix.

Sources: Strobel et al., 1995; Paul et al., 1997

ties. Submerged aquatic vegetation, discussed in a later

section, is sensitive to water clarity. Water clarity in

estuaries is influenced by biological processes (for

example, phytoplankton blooms); inputs of sediment and

detritus from streams, rivers, and nonpoint source runoff;

and resuspension of bottom sediments during intense

water movement, such as storms.

The clarity of estuarine water is determined by how far

light can penetrate into the water. We define poor water

clarity as water in which a diver would not be able to see

his hand when held at arms length. Fair water clarity

corresponds to a wader not being able to see his feet in

waist deep water. Most estuarine waters in

the Mid-Atlantic Region have good water

clarity (Figure 7). The degree of water clarity

problems across the major subregions is

related to the depths of the systems. Chesapeake Bay, being the deepest, has the overall

highest water clarity. The shallow Delmarva

coastal bays have the lowest. It should be

recognized that not all water clarity problems

are due to mans intervention. Wind mixing in

shallow water resuspends sediments and

decreases water clarity.

This overview of estuarine resource characteristics in the Mid-Atlantic Region sets the

context for describing the state of the estuaries.

For example, many factors underlie the changes

in fish abundance, sizes, and species composition in estuaries. Among these factors are

turbidity (water clarity) from resuspension of

sediments, surface runoff, and phytoplankton

growth; salinity; depth; and temperature.

Susceptibility of fish to poor water quality is, in

part, determined by estuarine characteristics.

The next chapters provide our snapshot of the

state of the estuarine environment in the MidAtlantic Region. They summarize what we

know about a set of indicators, or measures, of

estuarine condition for water and sediment

quality, habitat change, condition of living

resources, and aesthetic quality. Each indicator

is briefly discussed relative to its importance for

understanding estuarine condition, then summarized as to current condition using data from the

early to mid 1990s. The final chapter in this

report is our attempt to bring together the

current conditions into an overall evaluation of

estuarine condition.

8
Nutrients

All plants and animals need small amounts of nutrients,

such as nitrogen and phosphorus, to grow and reproduce. However, an excess of nutrients can lead to

eutrophication, a condition in which prolonged blooms

of algae rob light and oxygen from other organisms

while turning waterways green and foul smelling. The

concentrations of dissolved nutrients measured during

the summertime are shown in Figure 8. The highly

urbanized Delaware Estuary exhibits some of the largest

concentrations of nutrients measured anywhere in the

Figure 8. Concentrations of dissolved inorganic nitrogen and phosphorus measured during the summer

months in surface waters. Nutrient levels are higher than optimum in most of the rivers and upper bays.

The categories are defined and discussed further in the technical appendix.

Sources: Chesapeake Bay Program; Delaware Estuary Program; Bohlen and Boynton, 1996; Chaillou et al., 1996

9
world. Nutrient levels are high in the upper bay and

most tributaries of Chesapeake Bay, more so for

nitrogen than phosphorus. The northern coastal bays

are more enriched than the southern bays, reflecting the

population and development trends in coastal Delaware

and Maryland. Nutrient levels in the coastal waters are

relatively low.

Nutrient overenrichment does not automatically lead to

eutrophication. Other factors such as water clarity and

salinity also play a role (refer to the technical appendix

for more information). In the following section on

phytoplankton, we examine a surprising illustration of this

complex phenomena.

Nutrients can originate at either point sources (highly

localized spots such as sewage treatment plants and

industries) or nonpoint sources (more diffuse regions

such as leaking septic systems, farmlands, lawns, and the

atmosphere). A loading rate is the quantity of nutrients

delivered by humans each year to each acre of estuary.

This is a measure of the intensity of a nutrient source.

Figure 9 compares the point and nonpoint loading rates of

nitrogen and phosphorus in the major estuaries.

It is clear from Figure 9 that the Delaware Estuary

suffers the greatest loads. In part, this reflects the fact

that this region is highly urbanized, but the loads also are

high because of comparatively large contributions by point

sources. Fortunately, point sources are relatively easy to

identify and control; therefore reductions in the high loads

to the Delaware Estuary are possible. Elsewhere,

remediation programs must focus on controlling the more

diffuse nonpoint sources such as runoff from city streets

and farms and deposition from the atmosphere.

Figure 10 shows the quantities of point-source nutrients

delivered to Chesapeake Bay since 1950. Cities and

towns contribute far more nutrients to the bay than do

industries. Phosphorus releases declined steadily since

1970 when the Clean Water Act became law and a

phosphate detergent ban was implemented. Control of

nitrogen discharges is more difficult, but progress is

evident following the upgrading of sewage treatment

plants.

Figure 9. Nutrient loading (quantity of

nutrients per acre per year) for the Mid-Atlantic

estuaries in the early 1990s. Loads to the Delaware

Estuary are high. Point sources are relatively wellcontrolled, except in the Delaware Estuary.

Sources: Chesapeake Bay Program; Bohlen and Boynton, 1996;

Pennock et al., 1994; Cerco et al., 1994

Figure 10. Trends in the quantities of nutrients

delivered to Chesapeake Bay from point sources

since 1950. Recently, the nutrient loads have

been decreasing. Municipal sources are much

greater than industrial sources.

Sources: Chesapeake Bay Program

Water Quality

10
In summary, large portions of the regions estuaries are

nutrient over-enriched, especially in tributaries and near

urban centers. Efforts to reduce nutrient levels must

focus on controlling nonpoint sources in all watersheds

and point sources in the Delaware Estuary. Encouragingly, long-term trends are showing signs of improvement in response to environmental protection programs.

Phytoplankton

Phytoplankton blooms

Like plants everywhere, estuarine plants convert

sunlight and nutrients through photosynthesis into food.

Although bay grasses and macroalgae are common in

some shallow sites, phytoplankton (tiny floating algae)

are by far the most common plants in Mid-Atlantic

estuaries. Paradoxically, these phytoplankton communities are unnoticeable most of the year because they

are eaten as quickly as they grow. However, phytoplankton can bloom profusely for a few days or

weeks when growth conditions are optimal. These

blooms are part of the normal cycle in healthy estuaries (see sidebar). However, if extra nutrients are

continuously available, as is often the case in estuaries

near urban areas and farms, the blooms can persist

longer, sometimes for the entire summer. Such unbalanced plant growth caused by excess nutrients is called

eutrophication.

Prolonged phytoplankton blooms in eutrophic estuaries

are detrimental for several reasons. Dense growths of

the algae cloud the water and rob light from sensitive

beds of submerged aquatic vegetation (SAV), which are

underwater grassy regions that are critical habitats for

many other estuarine organisms. The massive losses of

SAV in Chesapeake Bay during the 1960s were attributed to such persistent blooms. Blooms upset the

ecological balance of estuaries by altering normal food

webs and encouraging the spread of exotic or toxic plants

at the expense of native species. Moreover, the dying

blooms generate unpleasant odors and consume dissolved

oxygen that would otherwise support the respiration of

fish and bottom-dwelling organisms, forcing these

organisms to move away or die.

To estimate phytoplankton abundance in estuaries,

biologists measure the concentration of chlorophyll

suspended in water. Chlorophyll is the green pigment

present in all plants. Figure 11 compares summer

chlorophyll levels throughout the Mid-Atlantic Region

estuaries. A rating of good designates healthy crops

of algae, while poor indicates the likely occurrence of

blooms persistent enough to harm sensitive SAV beds.

Figure 11 shows that the largest levels of chlorophyll are

found in the tributaries and upper regions of Chesapeake Bay. The coastal bays are moderately eutrophic,

with particularly high levels of phytoplankton measured

in several tributaries and man-made canals. Generally,

Phytoplankton Blooms

As with all plants, phytoplankton need light and

nutrients to grow and reproduce. However, neither

component is available year-round in Mid-Atlantic

estuaries. Sunlight is limited during the winter, and

nutrients normally are in short supply during the

summer and fall. A large spring bloom occurs

when the increasing sun angle delivers enough light

for the dormant algae to begin using the abundant

nutrients available from the well-mixed wintertime

waters. Smaller blooms occur throughout the

summer when storms mix the water, bringing

nutrients from the bottom into the sunlit surface

waters where the phytoplankton reside. In a healthy

system, the blooms are short-lived because nutrients

quickly become depleted, and the population of

zooplankton (microscopic plant-eating animals)

explodes to graze the phytoplankton crop.

Crustaceans, insects, and small fish then eat the

zooplankton, and larger fish eat these organisms,

etc. The estuary is fed and the murky waters clear

until the next bloom. However, this balanced cycle

is disrupted if extra nutrients are available.

Phytoplankton (and in some places the macroalga,

Ulva) then bloom continuously, clogging the

estuaries with uneaten and decaying plant material.

Phytoplankton bloom in an estuary. If the

bloom is persistent, the green algal mats can

block light to other plants and deprive animals of

oxygen. Area shown is about 5' x 6'.

Photo by: U.S. Chesapeake Bay Program

Water Quality

11
these chlorophyll patterns closely follow the patterns of

nutrient availability seen in Figure 8. In contrast however, the lower Delaware Estuary shows little indication

of eutrophication despite the very high levels of nutrients

found there (see sidebar). The coastal waters show

low levels of chlorophyll, as is normal for these coastal

regions.

Historically, eutrophication has decreased remarkably in

parts of Chesapeake Bay. For instance, chlorophyll concentrations in the upper and middle Potomac Rivers are now

about one fifth the levels evident in the 1970s and 1980s

when foul-smelling mats of algae bloomed in response to

high nutrient concentrations. Presently, blooms occur in the

Chesapeake and coastal bays after periods of intense

rainfall, probably in response to nutrients in runoff from

farms and city streets. In the coastal bays, eutrophication is

increasingly noticeable in the Indian and St. Martins Rivers

and in canals along developed shorelines.

Where are all the phytoplankton?

Surprisingly, the Delaware Estuary shows relatively

low levels of chlorophyll despite the very abundant

quantities of nutrients available in the bay. Why are

summertime algal blooms infrequent? In part, the

answer involves the fact that the bay is muddy.

Because the Delaware basin is broad and shallow, the

sediments are easily stirred by the winds and tides.

Erosion from farms deposits additional sediment loads.

The resulting low light levels in the water keep

potentially harmful blooms in check. Ironically,

managers are now concerned that improved land

management practices might clear the water enough

to permit eutrophication in the bay.

Figure 11. Chlorophyll concentrations

(a measure of algal abundance) measured

during the summer season in surface waters.

The chlorophyll patterns mirror nutrient

distributions, except in the Delaware Estuary.

Categories are defined in the technical

appendix.

Sources: Chesapeake Bay Program; Delaware Bay Estuary

Program; Bohlen and Boynton, 1966; Chaillou et al., 1996

Despite recent improvements, most tributaries

still are threatened by eutrophication. Chlorophyll-rich regions (bloom areas) generally

mirror patterns of nutrient over-enrichment,

except in the Delaware Estuary where murky

water inhibits persistent algal blooms. In most

cases, decreasing the sources of nutrients is a

viable solution to eutrophication.

Dissolved Oxygen

Dissolved oxygen (DO) is a fundamental

requirement for the maintenance of balanced

populations of fish, shellfish, and other aquatic

biota. The nature and extent of an organisms

response to hypoxia (low dissolved oxygen

concentrations) depend on several factors,

including the concentration of oxygen in the

water, the duration of the organisms exposure

to reduced oxygen, and the age and physiological condition of the organism. Most estuarine

animals can tolerate short exposures to

reduced dissolved oxygen concentrations

without apparent adverse effects. Prolonged

exposures to moderate hypoxia, defined as DO

below 5 milligrams of oxygen per liter of water

(mg/L, or parts per million), may result in

altered behavior, reduced growth, adverse

Water Quality

12
reproductive effects, and possible mortality to sensitive

species and juveniles. Some aquatic animals may

avoid low dissolved oxygen waters. This behavior may

result in increased predation and decreased access to

preferred feeding areas or spawning habitat. In

addition, aquatic populations exposed to low dissolved

oxygen concentrations may be more susceptible to

adverse effects from other stresses, such as disease

and toxic substances. Severe hypoxia (DO below 2

mg/L) results in death to most aquatic animals, especially during summer months when metabolic rates are

high.

As discussed in the prior section on Nutrients,

nitrogen and phosphorus fuel the growth of phytoplankton (see Figure 12). The nutrients enter the

estuarine waters primarily through wastewater discharges, agricultural and urban runoff, and atmospheric deposition. Decomposition of dead algae

consumes oxygen, which reduces the dissolved oxygen

available to support aquatic life. Algal growth increases with light and temperature, and decomposition

also speeds up with elevated temperatures. Vertical

stratification in estuarine waters (warmer, fresher water

over colder, saltier water) during the late spring to

summer period restricts reoxygenation of bottom

waters. The amount of oxygen that can remain dissolved in water is reduced as temperatures increase.

Therefore, natural processes that occur in estuarine

waters set the stage for maximum reductions of dissolved oxygen in bottom waters during the late summer.

The summer distribution of DO within one meter of the

bottom across the Mid-Atlantic estuarine area is shown

in Figure 13. Dissolved oxygen conditions are summarized by three categories: good, with DO greater than 5

mg/L (green); moderate hypoxia, with DO between 2

and 5 mg/L (yellow); and severe hypoxia, with DO less

than 2 mg/L (red). During the summer, 17% of the

estuarine bottom waters are moderately hypoxic, and

8% are severely hypoxic. Chesapeake Bay exhibits the

most hypoxia, with 21% of its area between 2 and 5 mg/

L, and 10% below 2 mg/L. These areas in Chesapeake

Bay are located in the middle portion of the Bay, the

lower portion of the Potomac River, and the Patuxent,

Patapsco, Chester, Rappahannock, and York Rivers.

Many of these areas are stratified and are continuously

depleted of DO during the summer months rather than

experiencing a cyclic condition where low dissolved

oxygen occurs only late at night, when photosynthesis is

not replenishing the oxygen. Because the data depicted

in Figure 13 were derived from daylight hours observaFactors Affecting Dissolved

Oxygen Levels

The amount of oxygen available to estuarine organisms is affected by salinity and temperature. Cold

water can hold more dissolved oxygen than warmer

water, and fresh water holds more than salt water.

The concentration of dissolved oxygen varies with

location and time of day. Oxygen is transferred from

the atmosphere into the surface waters by diffusion

and the aerating action of wind. It is also added as a

by-product of photosynthesis. Floating and rooted

aquatic plants and phytoplankton release oxygen as

part of photosynthesis. Because this process requires

light, production of oxygen is limited to shallow water

areas, usually less than 6 feet deep. Surface water is

nearly saturated with oxygen most of the year, while

deep bottom water ranges from saturation to anoxia

(no oxygen present).

Figure 12. Physical, chemical, and biological

processes affecting dissolved oxygen (DO) in estuarine waters that can result in hypoxia (low DO).

Source: Redrawn from USEPA, 1992

Water Quality

13
tions, the extent of depleted DO conditions in the

Delmarva coastal bays may not be properly characterized. Strongly associated with decreasing levels of

dissolved oxygen is the poor condition of

bottom-dwelling organisms. While other environmental

Figure 13. Distribution of summer-time dissolved oxygen within one meter of bottom sediments across estuarine

waters in the Mid-Atlantic Region. Categories are defined in the technical appendix. Data were derived from daylight

observations and do not necessarily reflect night time depressions that may occur in some areas. Map depicts spatial

distribution derived from multiple sources of information. Bar graph shows percent areas derived from EPA EMAP

1990-93 data.

Dissolved Oxygen Conditions

Graph Sources: Strobel et al., 1995; Paul et al., 1997

Map Sources: Chaillou et al., 1996; CBP, 1997; USEPA,

1995; Magnien et al., 1993; Strobel et al., 1995; Paul

et al., 1997

Water Quality

stresses also appear to affect bottom organisms, low

levels of dissolved oxygen most often co-occur with

poor conditions of bottom-dwelling animals in estuarine

waters of the Mid-Atlantic Region.

14
Potentially toxic substances reach estuaries from

industrial and municipal effluents, storm water runoff,

and atmospheric deposition. Many types of contaminants pose a potential threat to estuarine waters. These

contaminants include trace metals (chromium, copper,

lead, mercury, silver, arsenic, zinc) and organic compounds such as PAHs (polycyclic aromatic hydrocarbons), PCBs (polychlorinated biphenyls), and pesticides such as DDT, Chlordane, and atrazine. Most of

these contaminants bind to particles suspended in the

water and settle to the bottom; therefore, their concentrations in sediments typically are much higher than in

the overlying waters. Measuring toxic substances in

estuarine sediments is an efficient method of determining contamination levels in estuaries and identifying

areas that may require further evaluation.

Contaminated sediments and their potential toxicity to

aquatic life are considered by the public as a major

threat to estuaries. Contaminated sediments often are

considered an indicator of poor estuarine condition even

if the sediments are not presently toxic to estuarine

plants and animals. The concentration in the sediment

at which a contaminant becomes toxic depends on the

species and life stages of the organisms present, as well

as the physical and chemical characteristics of the

sediments and overlying waters. Due to the difficulties in

determining toxic concentrations of trace metals, PAHs,

PCBs, and pesticides, no state or federal regulatory criteria

or standards exist to determine acceptable sediment

concentrations of all these substances.

Sediment contaminant distribution across estuaries of the

Mid-Atlantic Region is shown in Figure 14. Sediment

contamination is categorized as sediments which pose no

risk to aquatic life (green), minimal risk to aquatic life

(yellow), and potential risk to aquatic life (red). Approximately 53% of the Mid-Atlantic estuarine sediments have

sediment contaminant levels considered to pose no risk to

Potentially Toxic Contaminants

Trace metals naturally occur in the earths crust.

Their presence in estuarine sediments does not

necessarily indicate contamination from human

activities. Many of these metals are essential to

organisms, in minute quantities, but if present in

sufficiently high quantities they can become toxic.

PAHs are organic compounds, like PCBs and many

pesticides. They are released to the environment

primarily through burning fossil fuels. Spills of

petroleum compounds, including leaking oil from cars,

also may cause environmental contamination.

Due to the widespread use of fossil fuels and the

large number of vehicles, PAHs are now ubiquitous

in the environment.

Contaminated sediments present a danger to the

organisms living in or near them and to the consumers

of these organisms.

Photo by: U.S. Fish and Wildlife Service

15
aquatic life. Only 6% of the sediments contain contaminant

levels considered to pose a potential risk to aquatic life.

These sediments are focused around the major industrial

areas in the region, such as Baltimore and Philadelphia.

The sources of toxic substances include point sources

(industrial and wastewater treatment plant discharges)

and nonpoint sources including urban stormwater runoff

(from streets, parking lots, and grassy areas), atmospheric deposition (directly on the water surface and on

the land that eventually enters the estuary), and agricultural runoff. Urban stormwater runoff and point sources

are the major sources for metals entering the estuarine

Graph Sources: Strobel et al., 1995; Paul et al., 1997

Map Sources: Chaillou et al., 1996; Costa and Sauer, 1994;

USEPA, 1995; Strobel et al., 1995; Paul et al., 1997

Sediment Contamination

Figure 14. Distribution of sediment contamination across Mid-Atlantic estuaries expressed as risks to

aquatic life. Categories are defined in the technical appendix. Map resolution is not in sufficient detail to indicate

that the Anacostia River, a tributary to the Potomac River in Washington, D.C., has been identified as having

potential risk from sediment contamination. Map depicts spatial distribution derived from multiple sources of

information. Bar graph shows percent area derived from EPA EMAP 1990-93 data.

waters of the Mid-Atlantic Region. The major sources

for PAHs and PCBs are urban stormwater runoff and

atmospheric deposition. Pesticide loadings to estuarine

waters primarily are from agricultural runoff and

atmospheric deposition. Recent studies by the National

Oceanic and Atmospheric Administrations (NOAA)

National Status and Trends Program indicate that

sediment contaminant levels in the

Mid-Atlantic Region generally

have been decreasing over the

last decade.

16
Coastal Wetlands

Wetlands were once considered to be little more than the

bothersome breeding grounds of mosquitoes and foul

smelling gases. We now realize they are extraordinarily

productive habitats that offer protective shelter and

abundant food to juvenile fish, shellfish, migrating waterfowl, and thousands of other species, many of which

are threatened or endangered. Coastal wetlands also

buffer the coastline from severe storms and intercept

nutrients and sediments that would otherwise interfere

with the sensitive nutrient and light requirements of

estuarine organisms.

Ecologists estimate that more than half of the regions

original coastal wetlands have been lost because of

human activities dating from pre-colonial times. Presently, about two thirds of the coastal wetlands are salt

marshes colonized by salt-tolerant grasses and bushes.

Much of the balance are tidal mud flats, areas that are

exposed at low tide and are densely packed with shellfish,

invertebrates, crabs, and other organisms. The remainder

are freshwater marshes, forests, and shrublands.

Figure 15 presents information about recent changes in

Chesapeake Bay salt marshes. From 1956 to 1989, about

6% of the regions wetlands were drained or filled to

accommodate human needs. The practices responsible

for most of these losses include pond construction,

channelization for mosquito control, urban and rural

development, and dredging for marinas. Conversion to

agricultural lands, along with natural processes such as

rising sea level and coastal subsidence, have contributed

to wetland destruction as well. More recently, the loss

rate has slowed in response to strict state and federal

conservation plans and slowed development. Agricultural

practices account for an increased portion of current

losses. Similar trends are evident in Delaware Bay and

the Delmarva coastal bays.

The near-term goal for the Mid-Atlantic Region is no net

wetland loss. This strategy implies that the remaining

wetlands will survive as robust habitats able to provide

shelter, food, and recreation for many organisms,

including humans.

Figure 15. Trends in the acreage of salt marsh in the

Chesapeake Bay region and the causes of loss over two

recent time periods. Recently, the losses have stabilized,

largely due to slowed development.

Source: Tiner et al., 1994

17
Submerged Aquatic Vegetation

The swaying meadows of bay grasses found in the

shallow waters of the Chesapeake and coastal bays are

called submerged aquatic vegetation or SAV. Bay

grasses such as eelgrass and widgeon grass provide

critical food, shelter, and nursery grounds for many

species of waterfowl, shellfish, finfish, and other organisms. In one study, biologists found that SAV beds

supported 30 times more young blue crabs than areas

without grasses. The grasses also stabilize the shifting

sediments and inject life-sustaining oxygen into the water.

Unfortunately, this important resource is very sensitive to

pollution. SAV is equivalent to the miners canary,

warning of poor conditions in the bays.

More than many other plants, bay grasses need plenty

of sunlight to grow. High levels of nutrients are

detrimental because they can stimulate extended

blooms of phytoplankton that block light to the SAV.

Sunlight is further attenuated by runoff from farms and

construction sites and by sediments suspended by

storms and tides. SAV originally colonized over

600,000 acres of the Chesapeake and coastal bays.

Only a tenth of that domain remains today.

The reasons for these historical losses are quite

different in the three estuary systems. The losses in

Chesapeake Bay are blamed on phytoplankton blooms

and nutrient over-enrichment, while the decline in the

coastal bays is attributed to an excess of suspended

sediments, in part associated with boating and construction. Eelgrass blight also decimated eelgrass beds

throughout the Mid-Atlantic region in the 1930s. In

contrast, Delaware Estuary probably never had

extensive SAV beds because the water in this shallow

bay is kept naturally murky by tides and storms. Clearly,

restoration strategies for the estuaries must be tailored

to the unique conditions of each bay. Figure 16 shows

encouraging signs of SAV recovery. The colonized

areas have doubled since the mid 1980s in the Chesapeake Bay and Maryland coastal bays. Presently, SAV

beds are nearly absent from the Delaware Estuary and

the Delaware coastal bays.

Wetland and SAV habitats are essential to the survival

of all estuarine life. However, both resources are very

sensitive to disruptions caused by humans. Loss of salt

marshes has mostly been stabilized

and the challenge now is to keep the

remaining marshes healthy. SAV

beds are slowly but steadily returning

to their former ranges, largely in

response to improved water quality.

Habitat Change

Figure 16. Recent changes in the coverage of

SAV in the Chesapeake and Maryland coastal bays.

An interim goal in the Chesapeake region is to

restore sea grasses to all areas where they were

observed prior to 1970 (about 114,000 acres) and to

enhance bed densities.

Sources: Chesapeake Bay Program; Bohlen and Boynton, 1996

18

Submerged aquatic vegetation

Photo by: Robert Orth
respond to human impacts in specific ways. A knowledge of these patterns helps us understand benthic

conditions in relation to the factors acting on the bottom

community.

Figure 17 displays the distribution of benthic community

condition across the Mid-Atlantic Region. Impacted

benthic condition refers to benthic communities determined to be in a degraded state. However, areas with

impacted benthic condition may not be related directly to

human effects because both anthropogenic and natural

disturbances can cause effects.

The Delmarva coastal bays have impacted benthic

communities in approximately one-fourth of their area.

The Indian River is the most impacted; three-fourths of

its area exhibit impacted benthic communities.

Chincoteague Bay is the least impacted, with approxiBenthic Condition

Bottom dwelling animals or benthos are linked with other

estuarine animals and plants through a network of

interactions that preserves the health of the estuarine

ecosystem. For example, benthic filter feeders promote

a healthy ecosystem by filtering algae and sediment from

the water, which helps maintain water clarity. That in

turn promotes good plant growth required for a productive bottom community. Benthic organisms are a

critical component of the estuarine food web, supporting

many commercially important species of fish and

shellfish.

Benthic organisms inhabit the bottom sediments where

contaminants tend to accumulate and where the bottom

waters are subject to low dissolved oxygen or fast

currents. Many remain in one spot on the bottom or

move relatively short distances over their life time.

Therefore, the condition of the benthic community often

is a good indicator of the condition of the local estuarine

environment. Benthic communities have been shown to

Benthic Condition Index

The change in salinity from fresh water to the sea

is the dominant factor determining the variety of

benthic animals. Therefore, an index of benthic

condition uses information on the variety of

animals we expect to find at different salinities.

This gives us an expectation for the condition of a

healthy benthic community. Large-scale patterns

of change in salinity are expected to cause large

changes in the expected variety of species.

However, if salinity remains the same and the

number of species found in the benthic community

is very different from that expected based on the

salinity, we can be fairly certain that some other

factor is causing this change. These departures

can be caused by natural or human factors. The

circumstances surrounding each case must be

examined to determine what factors or combinations of factors are responsible.

19

Illustration of a typical mud bottom benthic

community.
mately 10% of the area exhibiting impacted benthic

communities. Many of these impacted areas are

associated with nutrient overenrichment.

About one-fourth of the Delaware Estuary has impacted benthic communities. The highest density of

impact occurs in the Delaware River. Poor benthic

conditions in the Delaware River are associated with

levels of chemical contamination that commonly affect

estuarine organisms. Some areas exhibiting impact in

lower Delaware Bay occur where fast currents scour

the bottom, while other areas appear to be affected by

excess phytoplankton production due to nutrient

overenrichment, resulting in increased levels of organic

carbon in the sediments.

Approximately one-fourth of the area of Chesapeake

Bay contains bottom sediment habitats with poor benthic

communities. A large portion of this area (middle

mainstem and lower Potomac and Rappahannock

Rivers) is impacted by low dissolved oxygen conditions.

Toxic contaminants are responsible for impacts in

industrialized locations around the Bay. Small systems

near Baltimore, Norfolk, and Washington, D.C. are

areas where chemical contamination has affected the

benthic communities. Localized areas of eutrophication

also occur in some small embayments and estuaries and

along some river reaches (e.g., Pocomoke and upper

Potomac Rivers). Natural stressors, such as highly

variable salinity regimes, cause impacts in a few areas in

Chesapeake Bay (e.g., Elk River).

Condition of Living Resources

Graph Source: Strobel et al., 1995; Paul et al., 1997

Map Source: Chaillou et al., 1996; USEPA, 1995; Strobel et

al., 1995; Paul et al., 1997

Figure 17. Distribution of benthic community condition across estuarine waters in the Mid-Atlantic Region.

Categories are defined in the technical appendix. Map depicts spatial distribution derived from multiple sources of

information. Bar graph shows percent area derived from EPA EMAP 1990-93 data.

20
Overall, approximately one-fourth of the estuarine waters

of the Mid-Atlantic Region exhibit impacted benthic

communities. Many occur close to urban centers.

Benthic communities dominated by species that are

adapted to high sediment carbon concentrations occur in

the Delaware Estuary, the Delmarva coastal bays, and in

some small estuarine systems in Chesapeake Bay. The

most prominent cause of impacted benthic communities in

the Mid-Atlantic estuaries is low dissolved oxygen

concentrations in the bottom waters. This problem is

largely confined to Chesapeake Bay. Similar types of

stressors on the benthic communities (e.g., low dissolved

oxygen, chemical contamination, eutrophication, high

velocity currents, dredging, and trawling) occur in each of

the Mid-Atlantic estuaries; however, the relative importance and magnitude of the effects caused by each

stressor are different across the estuaries.

Shellfish Harvest

The annual oyster harvest for Mid-Atlantic estuaries has

been as high as 133 million pounds (in 1880, Figure 18).

Todays annual catch of about one million pounds is only a

small fraction of past harvests. Most of the bottom of the

Virginia portion of Chesapeake Bay is classified as

potential oyster ground. These areas did support populations of oysters in the past; however, today the only

productive ground left in lower Chesapeake Bay is the

middle portion of the James River, Virginia.

As will be discussed in a later section, disease, specifically Dermo and MSX, appears to be one of the major

causes of the recent drastic decline in oyster populations

in the Chesapeake and Delaware Bays. Over-harvesting and pollution also play major roles in Chesapeake

Bay. The impact of these diseases extends beyond their

direct effects on native populations of oysters. The

oyster is a filter feeder, meaning it pumps water

through its gills for both respiration and feeding. As it

pumps this water, the gills filter out particulates, including

phytoplankton, from the water. It has been estimated that

the pre-1870 population of oysters in Chesapeake Bay

could filter the entire water column of the

Bay in a few days. This suggests they

played a major role in clarifying the water

of the Bay, allowing more light to reach

the bottom where SAV grows. Because

of the drastic decline in the number of

oysters in Chesapeake Bay, it now takes

about 11 months for this filtering to occur.

The loss of this filtering capacity can

profoundly effect the ecosystem and may

have contributed to the decline in SAV.

Although no immediate solution to the

problem is known, researchers are

working on the concept of introducing

disease-resistant strains of oysters to MidAtlantic estuaries (see Incidence of

Disease section).

With the decline of the oyster industry,

the most important shellfish industry in

the Mid-Atlantic Region is now the blue

crab (Callinectes sapidus) fishery. As

oysters have disappeared from the

waters of major Mid-Atlantic estuaries,

many oyster fishermen have switched to

The American Oyster

Shellfish, specifically the American oyster,

Crassostrea virginica, have traditionally been one

of the major living resources harvested in the MidAtlantic states. Today oysters are the most

seriously threatened. The oyster has played an

important role in both the economics of the area

and the ecology of the estuaries. Oysters prefer

shallow water with a hard substrate and are

tolerant of salinities ranging from approximately 5

ppt to over 30 ppt, meaning they are well suited to

much of Chesapeake Bay, the Delaware Estuary,

and the Delmarva coastal bays.

Condition of Living Resources

Figure 18. Annual oyster harvest for Mid-Atlantic estuaries. Gaps in

the late 1880s and early 1900s do not represent zeros, but rather

missing data.

Sources: NOAA/NMFS; Chesapeake Bay Program; Haskin Shellfish Lab; Lyles, 1967a,b

21
fishing for blue crab. This has significantly increased

the fishing pressure on a population that already was

heavily exploited (approximately 75% of the adult crabs

of Chesapeake Bay are harvested yearly). Over the

past 40 years there has been a five-fold increase in the

Virginia Chesapeake Bay blue crab fishing effort. An

increase also has been seen in the Delaware Estuary.

New Jersey issued permits for 3,001 crab pots for the

Delaware Estuary in 1969. By 1993, that number had

risen to 40,688 pots.

Annual harvest of the blue crab has been variable over

the past decades (Figure 19). This variability likely is due

to natural environmental factors compounded by fishing

pressures. Environmental conditions play an important

role in the condition of crab stocks. The low catch

experienced in 1977 and again in 1981 in the Delaware

Estuary has been attributed to unusually severe winters in

which ice conditions resulted in high mortality among

over-wintering crabs. Another major factor is the speed

and direction of surface currents during spawning season.

Females typically travel down bay into the higher

salinity waters to release eggs. The larvae are photopositive, meaning they are attracted to light and, therefore,

reside in the surface waters. Wind-generated currents

may carry the larvae back into the bay, resulting in increased populations. Different wind patterns may carry

the larvae out to sea, causing lower catches in subsequent

years. Another important factor contributing to the

decline in crab populations is the loss of habitat, specifically beds of submerged aquatic vegetation that provide

shelter for juvenile crabs. As discussed in an earlier

section, there has been considerable loss of SAV in MidAtlantic estuaries.

Although the blue crab catch in Chesapeake Bay and the

Delaware Estuary remains about average, the catch per

unit effort (number of crabs caught per pot per day) has

decreased. Some scientists believe the harvest is being

kept up by increasing effort, notstable populations. Over

the past several years the blue crab

harvest in the coastal bays has been

minimal, predominantly due to disease,

which has significantly reduced blue

crab populations in these estuaries.

Scientists are concerned that consecutive years of poor environmental

conditions combined with heavy fishing

pressures could result in such a serious

impact on blue crab populations that it

would be difficult to recover. To avoid

such a situation, both Virginia and

Maryland have placed restrictions on

crabbing in Chesapeake Bay waters.

New Jersey and Delaware also have

taken steps to protect the fishery in the

Delaware Estuary, limiting the number

of commercial licenses issued and

placing restrictions on the collection of

egg-bearing female crabs.

Condition of Living Resources

Figure 19. Annual blue crab harvest for Mid-Atlantic estuaries.

Sources: NOAA/NMFS; Chesapeake Bay Program; Lyles, 1967a,b

22

Blue crabs harvested from Mid-Atlantic estuaries

Photo by: Chesapeake Bay Program
Shellfish Closures

Each state monitors their estuarine waters for coliform

bacteria and closes those waters to shellfishing when

the concentration reaches a critical level. In addition,

some areas can be closed for administrative reasons

such as the absence of a monitoring program and/or the

potential for contamination. For example, the low salinity

areas of upper Chesapeake Bay are not very productive

shellfish grounds; therefore, it is not cost-effective to

monitor these waters for coliform bacteria and, hence,

they are closed to shellfishing. Also, several coastal bays

are closed to shellfishing because of the potential for

contamination from a variety of sources.

Shellfishing is prohibited in 3% of the

3,660,000 acres classified as potentially productive shellfish ground.

Shellfishing is restricted (shellfish can

be harvested but must be brought to

another location to depurate prior to

consumption) in an additional 179,000

acres (5% of the area). Approximately

67,000 acres (2%) are conditionally

closed, such as after rainfall events that

may wash contaminants into the

estuary. The breakdown by major

estuary is shown in Figure 20. Figure 21 shows the

locations of closures. Considering the degree of urbanization in the Mid-Atlantic Region, it is encouraging that

the relative acreage of closed waters is low, and it has

decreased from 18% in 1985 and 1990 to 10% in 1995.

Of the total acreage in Chesapeake Bay that is harvestlimited (conditional, restricted, or prohibited), the most

common sources of contamination are marinas, urban

runoff, upstream sources carried down the tributaries, or

unidentified sources (Figure 21). This figure also illustrates the relative magnitude of the effects of the major

sources on harvest-limited acreage. Any given system

may be impacted by more than a single source, complicating remediation efforts. The major contributors in the

Delaware Estuary are sewage treatment plants and

leaking septic systems. Because of the wide diversity of

land uses on the Delmarva Peninsula, there are no

dominant sources of contamination.

Filter Feeding

Bivalve shellfish are filter feeders, meaning

they pump water through their gills for both

respiration and feeding. As they pump this

water, the gills filter out particulates, removing

suspended material from the water. Because

shellfish are such effective filters of the water,

they tend to accumulate whatever pollutants

are in the water. This can result in the closing

of an area to shellfishing due to their contamination. Most frequently, this is due to bacterial

contamination from a multitude of possible

sources.

Figure 20. Shellfish closures in

Mid-Atlantic estuaries expressed

as a percent of acreage classified

as productive grounds. (See text

for definitions)

Source: NOAA, 1997

Condition of Living Resources

23

Oyster harvest in the Chesapeake Bay

Photo by: Chesapeake Bay Program
Figure 21. Shellfish closure areas (in red) and bar graphs showing relative importance of major sources

of contamination. Many closure areas are too small to show up on this map.

Sources: State closure records; NOAA, 1997

Condition of Living Resources

24
Fish Stock Assessment

Fish generally occupy higher trophic levels in the

marine environment, and their abundance, distribution,

and condition are considered indicators of ecosystem

health. Many factors cause changes in fish abundance

and species composition. Among them are nutrient

concentrations, turbidity from suspended sediment,

phytoplankton abundance, salinity, current velocity,

overfishing, wetland loss, weather and oceanic conditions, and predator abundances. Fish are mobile and

able to detect and react to changing environmental

conditions. Tolerant fish remain in degraded coastal

systems, whereas more sensitive species move to more

habitable regions or simply succumb to the stress.

Abundant juvenile fish and diversity in species indicate

that a system provides sufficient habitat to support

reproduction and growth. Juvenile fish are sensitive to

anthropogenic stresses and, therefore, their abundance

may indicate how much contamination exists in a

system. Because higher trophic levels in estuarine

systems require a rich diversity of intact ecosystem

functions to survive, grow, and reproduce, fish abundance and species richness can be a broad and useful

indicator of estuarine health.

The Mid-Atlantic Region is a diverse area containing

many different types of habitat suitable for fish. This

variety of habitats, along with the complexity of fish

community interactions and the migratory nature of

many species makes it extremely difficult to assess the

overall condition of the fish community in an estuary.

In addition, different types of indices are used to assess

trends in different fish populations. Because of these

problems, this section focuses on specific, commercially

important species rather than the fish community as a

whole. Generally, fish monitoring in the region is based

on a combination of trawl sampling and seine surveys.

In addition, commercial fish landings data are available

and were used for this report.

Striped Bass (Morone saxatilis)

The striped bass (or rock fish) is an important commercial and game fish for the Mid-Atlantic Region. It is an

anadromous fish that uses freshwater environments

such as the upper Chesapeake Bay and the Hudson,

Roanoke, and Delaware Rivers for spawning. Adult

striped bass use feeding areas in the Delaware Estuary,

Chesapeake Bay, and along the Atlantic Coast northward to Maine. Striped bass were plentiful before the

industrial revolution, and population reductions were

apparent by the early 1900s. This species has undergone significant scrutiny since the decline of stocks in

the 1930s. Factors involved in these declines include

both overfishing and pollution. Moreover, habitat

degradation and losses from stress such as low dissolved oxygen in bottom waters of coastal embayments

have been associated with the lowered populations.

Researchers have attributed recovery throughout the

Condition of Living Resources

Summary of Fish Trends Data

 The striped bass fishery in Chesapeake Bay

and the Delaware Estuary is considered to be

recovering.

 American shad populations are improving

region-wide.

 The white perch population is stable but low in

Chesapeake Bay.

 Summer flounder populations are stable or

perhaps declining in the Delaware Estuary.

 Summer flounder populations are improving in

the Maryland coastal bays.

 Drum species populations are variable in the

Delaware Estuary.

 Shore-zone species composition suggest

degraded conditions in the Delaware coastal

bays.

 Shore-zone species compositions suggest

generally healthy conditions with slight

indications of degradation in the northern

coastal bays of Maryland.

25

Striped Bass

Photo by: U.S. Fish and Wildlife Service
1980s to improved water quality as well as reduced fishing

pressure. Water quality improvements were primarily due

to upgraded sewage treatment. Overfishing was halted

by protective management practices implemented by the

states, including a fishing moratorium from 1985-1990 in

Chesapeake Bay and the Delaware Estuary.

Since that time, population levels have improved

(Figure 22). Because of the improved conditions,

the Atlantic States Marine Fisheries Commission

declared the fish stock restored, and fishing

restrictions on the striped bass have been liberalized (but still exist). The 1996 data in the Chesapeake Bay show a record juvenile population

index in both Virginia and Maryland, exceeding the

previous record set in 1993.

American Shad (Alosa sapidissima)

The situation for the American shad is quite

different from that of the striped bass. Another

anadromous fish, the American shad migrates

annually into freshwater areas of the Delaware

Estuary and Chesapeake Bay. Since its high

mark in the late 1800s, a precipitous drop in

commercial landings has been seen in both

systems due to excessive harvesting, pollution,

and construction of dams and other waterway

obstructions causing loss of spawning grounds

(Figure 23). Over the past few years,

region-wide abundances have improved dramatically as a result of federal, state, and

interstate efforts to reduce fishing pressure,

increase spawning ground accessibility, and

improve water quality by improving wastewater

treatment (Figure 23 insert). However, this

species remains under strict management.

White Perch (Morone americana)

The white perch, an important commercial and

sport fish in the Delaware Estuary and Chesapeake Bay, has shown a relatively stable

population over the past 100 years. In Chesapeake Bay, fluctuations in the Maryland juvenile

index were greatest in the late 1960s through

the 1970s and decreased throughout the 1980s.

The index jumped markedly in 1993 to its

highest levelmore than four times the average

over the survey period. Thus, some consider

the white perch to be an under-used resource.

Several factors are considered important in its

ability to maintain a stable population, including

its fecundity, early maturation, expansive

spawning and nursery grounds, and tolerance of

poor water quality.

Summer Flounder (Paralichthys dentatus)

The summer flounder is a popular sport and commercial

fish in the Mid-Atlantic Region. It ranges from Canada

Condition of Living Resources

Figure 23. American shad landings in Chesapeake Bay

showing decreased commercial landings since the late 1800s.

Gaps in the late 1800s and early 1900s do not represent zeros,

but rather missing data. 1993-94 data are preliminary.

Recent data on the abudance of adult fish in the upper

Chesapeake Bay (insert) show improvement of stocks.

Source: NOAA; Chesapeake Bay Office; Chesapeake Bay Program 1997.

Figure 22. Normalized indices for juvenile striped bass indicating

recent improvements to juvenile fish stocks. For the Delaware River

it represents the seine index; for Chesapeake Bay it represents the

juvenile index for VA and MD. Numerical comparisons between

systems cannot be made due to the differences in the indices.

Source: NOAA; Chesapeake Bay Office; Dove and Nyman, 1995.

26
have been studied to evaluate changes in species composition in response to changes in environmental stress. In

the Delaware coastal bays, significant physical, chemical,

and habitat changes have occurred over the last 60 years,

including increased levels of chlorophyll, suspended solids,

nutrients, and salinity. These changes have resulted in

shifts in species composition. For example, in the White

Creek area of the Delaware Estuary, species have

shifted from juvenile menhaden, tidewater silversides, and

bay anchovy to killifish and mummichog. Overall,

pollution-tolerant species such as cyprinodontids (e.g.,

killifish) are becoming more dominant as sensitive species

decrease (Figure 24). These changes are consistent with

the hypothesis that more sensitive fish have left the areas

and more tolerant species have taken their place. In the

Maryland coastal bays, fish community diversity has

remained relatively stable; however, in some northern

areas, pollution tolerant species have increased in abundance. Future environmental alterations could result in a

more significant shift, as has occurred in the Delaware

coastal bays.

Figure 24. Schematic depiction of the changes

in the Delaware and Maryland coastal bays shallow

water fish species over the past 20-30 years. Note

changes from sensitive species to more tolerant

species in the Delaware coastal bays compared

to the stability in the species composition in the

Maryland coastal bays.

Source: Chaillou et al., 1996

to Florida and is a migratory resident of coastal estuaries

during the summer, moving offshore to the continental

shelf in the winter. The summer flounder is heavily

exploited and has been managed by federal and state

regulations during the 1990s. Despite high fishing pressure,

the summer flounder persists in the Delaware Estuary. In

the Maryland coastal bays, summer flounder showed a

peak in abundance in the early to mid-1980s followed by a

decrease in the late 1980s. A gradual improvement in the

population during the 1990s has been documented.

Drum species

Many species within the drum family are important

recreational and commercial fish and significant contributors to the food web due to their abundance and range.

In the Delaware Estuary and Maryland coastal bays, four

species of drum are significantspot (Leiostomus

xanthurus), black drum (Pogonias cromis), Atlantic

croaker (Micropogonias undulatus), and weakfish

(Cynoscion regalis). Significant historical variations in

young-of-the-year abundances and annual commercial

landings of spot, black drum, and Atlantic croaker are

thought to be due to many factors. These include

summer wind regimes, winter temperature, environmental

variations in spawning grounds, and effects of juvenile

predators such as jellyfish. The most recent data for

Atlantic croaker and weakfish show improved recruitment. For example, above average recruitment for

Atlantic croaker in the Maryland coastal bays was

observed from 1993 to 1995; however, it was still much

lower than the recruitment observed in 1974. The

Delaware Estuary showed nearly a 10-fold increase in

1992 compared with the 1980s. Finally, the 1995 trawl

catch for weakfish was the second largest catch between

1972 to 1995.

Shore-Zone Species

Historical data on shore-zone species (those that inhabit

shore-zone habitats and shallow water environments)

Condition of Living Resources

27

Illustration of Summer Flounder
Contaminants in Fish and

Shellfish

Chemical contaminants may enter a marine organism in

several waysdirect uptake from contaminated water,

consumption of contaminated sediment, or consumption

of previously contaminated organisms. Once an

organism is contaminated, it tends to retain

(bioaccumulate) these chemicals unless there is an

effective cleansing mechanism. Chemical concentrations may increase with subsequent feedings. An

organism higher on the food chain may inherit the

levels of chemicals present in the organisms lower in the

chain. This process, known as biomagnification, leads

to an increase of chemical contaminants, perhaps to

toxic levels. All organisms that consume contaminated

organisms, including humans, may be at risk of suffering

some toxic effect. The accumulation of these contaminants also may result in increased susceptibility to disease

or effects on growth or reproduction. It should be noted

that some chemical contaminants are not bioaccumulated

or biomagnified.

Contaminant levels in fish and shellfish from the Delaware Estuary, Chesapeake Bay, and the Delmarva

coastal bays vary widely. Some of the lowest fish or

shellfish contaminant levels in the nation have been

found in the Mid-Atlantic Region. At the same time,

fish or shellfish from other sites in the region have

tissue residues that are among the highest in the nation.

Many contaminants generally are at or below the

national average, and the levels in both fish and shellfish

appear to be declining. Generally, tissue residues are

higher in samples from the Delaware Estuary than in

samples from Chesapeake Bay, while levels in the upper

Chesapeake are higher than in the lower Chesapeake

Bay. The ban on the use of certain chemicals (e.g.,

Chlordane, Kepone, PCBs, DDT) apparently has led to

gradual, though significant, declines in the concentrations

of these chemicals in fish and shellfish. In some cases

(e.g., Kepone in the lower James River) tissue residues

have dropped below action or advisory levels,

resulting in the lifting or downgrading of bans on

consumption. Concentrations of a few heavy

metals in fish and shellfish may, however, be

increasing in some localized areas. Samples taken

from urban watersheds (e.g., Patapsco River near

Baltimore Harbor, the Potomac River near Washington, D.C., the James and Elizabeth Rivers near

Norfolk) generally have elevated concentrations of

multiple contaminants, typical of anthropogenic input.

Contaminant Levels in Fish

Although concentrations of many contaminants

are low or not detected in fish in the Mid-Atlantic

Region, several hot spots exist. Fish consumption bans or advisories exist in many of these

areas (Figure 25). In Delaware, bans or advisories on consumption of fish due to elevated PCB

concentrations are in effect for the tidal portions

of the Red Clay, Christina, Brandywine, and

Delaware Rivers, as well as Little Mill Creek,

White Clay Creek, and Delaware Bay. Chlordane

levels that exceed the FDA action level have been

reported in the upper Delaware Estuary. High

Chlordane concentrations have resulted in consumption advisories for several fish species in the

Figure 25. Fish consumption bans or advisories in effect for Delaware Estuary, Chesapeake Bay, and Delmarva coastal bays.

Sources: DNREC, 1994, 1996; Chesapeake Bay Program,

1993; Delaware Estuary Program, 1996

28

Condition of Living Resources
Condition of Living Resources

29

Back River and Baltimore Harbor, Maryland. Chlordane and PCB levels in the Anacostia and Potomac

Rivers in the District of Columbia have prompted

advisories, while kepone levels, although decreasing,

have resulted in an advisory on the consumption of fish

from the lower James River in Virginia.

Contaminant Levels in Shellfish

Tissue residue data from shellfish collected throughout

the region are difficult to characterize. Some of the

lowest tissue residues measured in shellfish in nationwide studies have been found in the Delaware Estuary,

Chesapeake Bay, and the Delmarva coastal bays.

Other contaminant levels are among the highest recorded. Figure 26 compares shellfish tissue residues

from the region to national averages. Silver concentrations in oysters from the region range from the lowest

nationwide to within the highest 12 percent nationwide.

Copper, cadmium, and zinc levels in bivalves are among

the highest measured in the nation, including the highest

measurements for zinc and cadmium. Mercury tissue

residues from Chesapeake Bay are low, accounting for

many of the lowest levels in the nation. Some of the

lowest chromium tissue residues were found in the MidAtlantic estuaries, but four locations had high levels.

Similarly, lead levels ranged from very low to one site

with a high concentration. DDT and related compounds, Chlordane and related compounds, and PCB

concentrations tended to be higher than the national

average at most of the sampled sites in the Mid-Atlantic

Region, with multiple sites rated high. PAH concentrations in the region also range from the lowest in the

nation to one site classified as high. In general, more of

the contaminants were classified as having high concentrations in the Delaware Estuary than in Chesapeake

Bay and the coastal bays. The extremes in the concentrations probably indicate the presence of hot spots

associated with urban activities surrounded by more

pristine conditions.

Relatively few areas in the region have bans or advisories on the consumption of shellfish. In Virginia, high

levels of PAHs and their metabolic breakdown products

have led to bans on the consumption and collection of

oysters and crabs in the Elizabeth River and Little

Creek. Similarly, shellfish collection and consumption is

prohibited in the Lafayette River. PCB levels in blue

crabs have resulted in consumption advisories for

portions of the Delaware Estuary. In general, however,

shellfish contaminant levels are relatively low throughout

the Region.

Figure 26. Shellfish tissue residues compared to national

averages. High indicates concentrations that are

significantly above the national average; low means

significantly below the national average. This illustrates

the range of concentrations encountered in the Region.

Source: NOAA, 1994

Incidence of Disease

Probably the most disturbing sign of pollution to the angler

is catching a fish with some form of external abnormality.

However, to the untrained observer, this is a poor indicator of degraded water quality. What the angler believes is

fin rot or an open ulcer might actually be an injury.

Athough the cause of an abnormality may not be chemical contamination, a high incidence of such conditions

would indicate an environmental problem.

EPAs Environmental Monitoring and Assessment

Program (EMAP) conducted an examination of fish for

external abnormalities in its 1990-1993 survey of the

Mid-Atlantic estuaries. A total of 13,467 fish from 177
stations (138 in the Chesapeake system, 32 in the

Delaware Estuary, and seven in the Delmarva coastal

bays) were examined by trained personnel. Only 41

fish, or three per thousand (0.3%) examined, were

afflicted with fin erosion, ulcers, growths, or abnormal

lumps (Figure 27). The majority of these fish were of

bottom-dwelling species such as channel or white

catfish, or brown bullhead. No affected fish were

collected in the Delmarva coastal bays. At 13 of the 20

stations where fish with a pathological condition were

found, only a single fish with an abnormal condition was

collected per station. The station with the highest

incidence was located in Marylands Back River. The

low incidence of pathologies found in the Mid-Atlantic is

comparable to the overall incidence determined for the

east coast from Cape Cod, Massachusetts, to the mouth

of the Chesapeake. The incidence rate is only slightly

higher than the 0.2% determined for the South-Atlantic

coast. It is considerably lower than the 1% determined

by EMAP for the estuaries of the Gulf of Mexico.

Although over fishing and environmental factors may

have contributed to the depletion of oyster stocks,

disease generally is recognized as the major cause of

the decline over the past few decades. The two main

diseases affecting oysters are Dermo and MSX, caused

by the protozoan parasites Perkinsus marinus and

Haplosporidium nelsoni, respectively. Dermo was

discovered affecting oysters in Chesapeake Bay waters

in the 1950s and the Delaware Estuary in 1990. Although Dermo was first introduced to the Delaware

Estuary in the 1950s with imports of seed oysters from

the Chesapeake, it failed to become established at that

time. MSX was first observed in Chesapeake Bay in

1959 and in the Delaware Estuary in 1957. These two

diseases have decimated the oyster populations of both

estuaries. Both parasites are most active in waters with

salinities between 15 ppt and 30 ppt, which is why the

most productive oyster beds today are in lower salinity

areas, such as the middle James River. Most of the

waters of the Mid-Atlantic estuaries fall within this midsalinity range (Figure 6), resulting in an extremely widespread problem. The spatial extent of these diseases

has varied over the past decades with climatic conditions

(e.g., amount of rainfall and summer temperatures). The

mid-1980s were unusually dry and warm years in the

Mid-Atlantic states, which resulted in the intrusion of

more saline waters further up into the estuaries than

usual. This intrusion introduced the diseases to oyster

beds throughout the bays and resulted in mass mortalities.

More than 75% of all oysters in Chesapeake Bay were

killed, and the stock has not recovered. Both diseases

are present in the Delmarva coastal bays, but are not as

virulent in the higher salinity seawater. Although some

oysters in the Delmarva coastal bays have been affected,

large-scale kills like those in the Chesapeake Bay and the

Delaware Estuary have not occurred. However, significant reductions in oyster populations have occurred in

other coastal systems.

One question frequently asked is why have the oysters

become infected. One popular theory is that stress from

pollution reduced the oysters resistence to disease.

Researchers have shown that pollutant stress increases

the oysters susceptibility to disease. Although there is no

known way to combat the disease directly, researchers

are currently studying the feasibility of introducing

disease-resistant strains of oyster or other species of

oysters to local waters to reclaim the fishery. It is

important to note that these diseases pose no known

human health threat, either through contact with seawater or the ingestion of contaminated shellfish.

Another highly visible indicator of environmental

degradation is the incidence of fish kills. Fish kills can

result from a number of both natural and anthropogenic

Figure 27. Incidence of pathological condition in

fish of Mid-Atlantic estuaries.

Source: U.S. EPA, EMAP Database (1990-1993)

Disease Issues

There are three major disease issues of ecological and economic importance in the Mid-Atlantic

estuaries: pathological conditions in fish, oyster

disease, and fish kills due to bacterial infection.

The incidence of pathological conditions in fish

and fish kills due to disease is low in Mid-Atlantic

estuaries. Unfortunately, the prevalence of

oyster disease is high and has nearly destroyed

the oyster fishery.

Condition of Living Resources

30
Condition of Living Resources

31

causes. The majority of fish kills are probably a result

of low dissolved oxygen (hypoxia) in the water due to

high water temperatures, over-enrichment (eutrophication), or simply the movement of too many fish into an

embayment (the fish use up the oxygen as they breath).

Other potential causes of fish kills include fishing bycatch, chemical pollution, toxic algae, and disease. The

massive kills of millions of menhaden in upper Chesapeake Bay in the late 1980s was attributed to a Streptococcus infection combined with high water temperatures (resulting in hypoxia). We have not seen such

conditions in the 1990s. NOAA reported that the

highest number of fish kills in the Mid-Atlantic Region in

the 1980s occurred in Marylands Anne Arundel and

Baltimore Counties. Most of these fish kills were

attributed to disease and low dissolved oxygen due to a

combination of over-enrichment and large numbers of

fish entering relatively small embayments. This trend

has continued into the 1990s with the same portion of

Chesapeake Bay exhibiting the highest incidence of fish

mortalities. However, disease has played a less important role.

During the summer of 1997, a number of fish kills

occurred in several of the small tributaries of Chesapeake Bay and some of the coastal bays. The causative agent for these kills was determined to be the toxic

dinoflagellate Pfiesteria piscicida or Pfiesteria-like

organisms. This complex organism can reside as a cyst

in the sediments of estuaries or as a non-toxic dinoflagellate. These cysts can turn into toxin-producing

cells when conditions are right (warm water, high

nutrient loads, moderate salinity, poor flushing) and they

Pfiesteria

 Pfiesteria is not a disease but a dinoflagellate.

 Dinoflagellates are unusual organisms, part

plant and part animal.

 Dinoflagellates are a normal component of the

marine ecosystem.

 Pfiesteria has 24 different life stages, including

bottom-dwelling cysts and toxic stages.

 Most outbreaks occur in warm water and at a

salinity of about 15 ppt.

 The organism 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.

detect large numbers of fish. These cells release a

powerful neurotoxin that stuns the fish. Fish then

develop sores and begin to die. These kills can last a

few hours or several days. Usually by the time the kill

has been noticed, the organism has reverted back to

cysts and has settled back into the sediment. Within a

day or so, the toxin in the water has degraded, leaving

no signs of the organism.

Waterfowl

Another important living resource of Mid-Atlantic

estuaries is waterfowl (e.g., ducks, geese, swans) and

other birds associated with the water (e.g., herons,

egrets, osprey, eagles). Birds not only play a major

ecological role in these systems, but also provide a

recreational opportunity for hunters, photographers, and

bird watchers. Many species are highly dependent upon

wetlands and submerged aquatic vegetation for their

survival, and alterations to these environments affect the

populations of resident and migratory birds. Today,

habitat alteration is probably the major factor controlling

local bird populations. We stress local because many

of the species found in the estuaries of the Mid-Atlantic

are migratory, meaning they spend only a part of the

year in this area. As such, their overall abundance may

be determined by environmental factors where these

birds summer and breed, such as the Prairie Pothole

wetlands of the north-central United States and plains of

Canada. This makes the bird story a particularly

complicated one. For example, green-winged teal

(Anas crecca) are at their highest levels since the

1950s, not because of conditions in the Mid-Atlantic, but

because conditions in the Prairie Pothole region have

Fish exhibiting sores caused by Pfiesteria.

Photo by: Maryland Department of Natural Resources
been favorable over the past several years. Significant

rain has resulted in the emergence of many ponds that

had dried up during 30 years of drought.

One interesting ecological story playing out in

Chesapeake Bay is the competition between the

black duck (Anas rubripes) and the mallard (Anas

platyrhynchos). Whereas mallard populations are on

the rise, black ducks are decreasing (Figure 28). This is

largely due to habitat loss and the release of mallards to

the Bay. Valuable black duck habitat is lost as wetlands

are eroded and land is developed for human use. Black

ducks tend to stay away from people, and will abandon

wetlands in close proximity to human development.

Mallards, on the other hand, are more adaptable to the

presence of people and are more likely to be found in

developed areas. Also, over the past several decades

mallards have been released to the Bay to increase

populations for hunting. The effect of this on the black

duck population is unknown, but both species are in

competition for the same resources. Further complicating this story is the fact that these two species can interbreed, resulting in hybrids. The picture is different for

the coastal bays (Figure 28) and the Delaware Estuary,

where black ducks outnumber mallards and both

populations are stable.

Another species of migratory waterfowl that is now a

resident of Mid-Atlantic waters is the Canada goose

(Branta canadensis). Although geese have always

wintered in the Mid-Atlantic, they did not become

permanent residents until the early 1900s when some

were brought to Chesapeake Bay from the Great Basin

population to be used as live decoys. This practice

ended in the 1920s, but the birds remained and bred,

with some taking up residence in the Delaware Estuary

as well. The largest populations of resident geese are

Figure 28 . Trends for mallards and black ducks in

Chesapeake Bay (heavy lines) and the Delmarva

coastal bays (thin lines). The Delaware Estuary has

been excluded for the purpose of clarity. The graph

shows the mid-winter survey count, not an actual

population count.

Sources: U.S. Fish and Wildlife Service, Mid-Winter Migratory

Bird Survey

Mallard Ducks

Photo by: U.S. Fish and Wildlife Service

Black Duck

Photo by: Wayne Munns

Condition of Living Resources

32
Condition of Living Resources

33

Figure 29. Trends for Canada geese in Chesapeake

Bay and the Delmarva Coastal Bays. The Delaware

Estuary has been excluded for the purpose of clarity,

but the trend is similar to that of the coastal bays. The

graph shows the mid-winter survey count, not an

actual population count.

Sources: U.S. Fish and Wildlife Service, Mid-Winter Migratory

Bird Survey

found on the western side of Chesapeake Bay. Because this area is more densely populated by man, most

of the hunting occurs on the more remote eastern shore.

Most of the geese along the eastern shore are migrants,

and because of overharvesting and weather patterns to

the north, the population of migrant geese has declined

sharply. However, these populations are beginning to

recover (Figure 29). Therefore, despite an overall

abundance of Canada geese in the Chesapeake Bay

basin, hunting has been restricted to early September to

ensure that only resident geese are taken and to allow

migrant populations to recover.

Other species of waterbirds with increasing populations

include the diving ducks (canvasbacks have reached the

restoration goal for Chesapeake Bay) and the great blue

heron (a colonial nesting bird). Figure 30 shows the

trend in the mid-winter survey count for all waterfowl in

Chesapeake Bay and the Delmarva coastal bays. It

shows how variable counts can be from year to year.

This variability can be due to a number of conditions,

both natural and man-induced. Although there has been

no significant overall trend for waterfowl as a group,

some species have increased while others have decreased. Scientists are concerned that local populations

of some species have not increased over the past few

years. Wet conditions in the Prairie Pothole region of

the country has led to a significant increase in the

overall national population of many migratory species.

A similar increase has not followed in the Mid-Atlantic

because the birds are favoring other wintering sites,

such as along the Gulf Coast. One popular theory

among scientists is that the increase in human activity

along Mid-Atlantic coast, coupled with the loss of SAV

and wetlands, is making this region less attractive to

many species of migratory waterfowl. One question

being asked is what will happen to the Mid-Atlantic

migratory waterfowl populations if prolonged drought

conditions return to the Prairie Potholes.

Threatened and Endangered

Species

Species of plants or animals can become threatened or

endangered due to habitat loss, unregulated killing or

collection, pollution, disease, predation, or competition

with other species. Although a species may become

Figure 30. Overall trend for all waterfowl in

Chesapeake Bay and the Delmarva coastal bays.

The graph shows the mid-winter survey count, not an

actual population count.

Sources: U.S. Fish and Wildlife Service, Mid-Winter Migratory

Bird Survey

Canada Geese

Photo by: U.S. Fish and Wildlife Service
extinct for natural reasons such as being out-competed by another species, over the past century the rate

at which species are becoming endangered has significantly increased due to mans activities. In many areas

of the United States, rapid growth in population, industry,

and agriculture has led to significant stresses on a range

of native species of plants and animals. Recognizing the

impacts of these stressors, Congress took action in 1973

by passing the Endangered Species Act, making the

conservation of endangered and threatened species and

the ecosystems that sustain them a National priority and

instituting public policy to work for their recovery.

The Mid-Atlantic Region has experienced some of the

most rapid population growth, industrial development,

and intensive agriculture in the country. Not surprisingly, many organisms relying on the estuaries of the

Mid-Atlantic have suffered. Over 50 species of plants

and animals are listed as threatened or endangered in

the Mid-Atlantic states. Although most are not associated directly with estuaries, several are. These include

the bald eagle, peregrine falcon, piping plover, several

species of sea turtles, and shortnose sturgeon. New

Jersey, Delaware, Maryland, and Virginia have made

formal declarations to protect threatened and endangered species. For example, it is in the best interest of

the state to preserve and enhance the diversity and

abundance of nongame fish and wildlife and to protect

the habitat and natural areas harboring rare and vanishing species of fish, wildlife, plants, and areas of unusual

scientific significance or unusual importance to the

survival of Delawares native fish, wildlife and plants in

their natural environments. These efforts have

reversed the process of extinction for most of the

species we associate with the estuaries (Figure 31).

Continued efforts to protect these sensitive organisms

hopefully will result in their populations reaching levels

sufficient to ensure their continued existence.

PROFILES OF SELECTED

ENDANGERED SPECIES

Bald eagle (Haliaeetus leucocephalus)

This species formerly nested throughout North

America. Population declines were attributed to habitat

loss, illegal shooting, and the effects of DDT on reproductive success. The eagle has benefited from increased regulation of pesticides, nest site protection,

aggressive habitat management, and reintroductions.

Many states have successfully reestablished nesting

populations by translocating young birds from areas with

healthy populations to suitable, unoccupied habitat.

Public awareness campaigns and vigorous law enforcement have helped reduce illegal shooting of eagles.

Bald eagle numbers in the lower 48 states have increased from approximately 417 nesting pairs in 1963 to

Figure 31. Trends in selected threatened

and endangered species in the Mid-Atlantic

estuaries. Up arrow indicates improving trend,

question mark indicates trend is uncertain. None

of the major estuarine threatened or endangered

species currently are declining.

Source: U.S. FWS Endangered Species Database

Bald Eagle

Photo by: U.S. Fish and Wildlife Service

Condition of Living Resources

34
35

more than 4,000 pairs in 1993. In addition, there are an

estimated 5,000 to 6,000 juvenile bald eagles in the

lower 48 states. As a result of the significant progress

toward recovery, the species has been reclassified from

endangered to threatened in the lower 48 States. The

bald eagle is an example of

success in the recovery of an

endangered species and is the

result of more than twenty years

of national effort to change the

trend in population decline. A

wide range of actions were taken

to conserve and restore habitat

and control pesticide contamination problems.

Kemps ridley turtle

(Lepidochelys kempii)

There are only seven living

species of sea turtles in the world

and the Kemps ridley is under the

greatest threat of extinction.

Virtually the entire world population nests annually in a single

locality on a beach near Rancho

Nuevo, Mexico. When this nesting site was first

discovered in 1947, the adult female population was

estimated to be greater than 40,000 but has decreased

to approximately 490 based on recent estimates.

Juvenile turtles are thought to be carried north via

passive transport in the Gulf Stream, where they feed

Kemps ridley turtle

Photo by: U.S. Fish and Wildlife Service

Shortnose Sturgeon

Photo by: U.S. Fish and Wildlife Service

Condition of Condition of Living Resourcess

Shortnose sturgeon

(Acipenser brevirostrum)

The shortnose sturgeon is the smallest of the three

sturgeon species in eastern North America. It is an

anadromous fish that spawns in coastal rivers of eastern

North America from Canada to Florida. The

sturgeon is a fairly large fish (maximum known

length of 56 inches), is long-lived (maximum

known age is 67 years), and was commercially

important until the 1950s. They prefer the

nearshore marine, estuarine, and brackish

habitats of large river systems. Shortnose

sturgeons, unlike other anadromous species in

the region such as shad or salmon, do not

appear to make long distance offshore migrations. Principle stressors that have resulted in

the severe population decline of the shortnose

sturgeon are pollution, incidental overfishing in

shad gillnets, construction of dams, and habitat

alterations from discharges, dredging, or

disposal of material into rivers.
Estuaries are transitional zones where salt water from

the sea mixes with fresh water flowing off the land.

Estuaries in the Mid-Atlantic Region provide habitats for

many birds, mammals, fish, and other aquatic life. They

also are important assets that humans use in a wide

variety of ways.

From the information presented in the prior chapters, the

complexity and value of the estuarine resources of the

Mid-Atlantic Region (circa early to mid 1990s) is apparent. Estuaries are natural mixing bowls for physical,

chemical, and biological interactions; and they are threatened by a myriad of human uses. This complexity

challenges our ability to understand and manage these

great natural resources.

In this report, we have summarized our current understanding of how well estuaries, as a whole, are doing in the MidAtlantic Region by presenting information on individual

indicators. These individual measures tell us the condition

of the Mid-Atlantic estuaries within the context of that

particular indicator. A synopsis of our findings follows.

 Nutrient concentrations are relatively high in many of

the rivers and smaller bays in the Mid-Atlantic estuaries. High nutrient levels are not harmful in themselves;

however, overenrichment can cause prolonged phytoplankton blooms that can disrupt estuarine processes.

Nonpoint sources such as leaking septic systems, runoff

from farms and construction sites, and deposition from

the atmosphere are the most common sources of

excess nutrients. However, municipal and industrial

point sources also contribute large nutrient loads,

especially to the Delaware Estuary. Although the

Delaware Estuary is one of the most enriched estuaries

in the world, harmful phytoplankton blooms are held in

check by other factors such as poor water clarity

attributed to both natural and human processes. Nutrient loads in Chesapeake Bay are declining, largely in

response to improved control of point sources (for

example, the upgrading of sewage treatment plants)

and bans on certain types of phosphorus detergents.

The Delmarva coastal bays are moderately enriched,

particularly in Delaware. Coastal waters presently

exhibit low nutrient levels, but there is evidence that

these levels are increasing. Future progress must focus

on controlling nonpoint nutrient sources.

 Prolonged phytoplankton blooms can disrupt the

growth of submerged aquatic vegetation and promote

hypoxia and anoxia in stagnant estuarine waters. High

concentrations of chlorophyll during the summer

indicate that eutrophication is a problem in the tributaries and upper reaches of Chesapeake Bay and the

coastal bays of Delaware and northern Maryland. At

present, extended blooms in the Delaware Estuary are

uncommon despite high nutrient loadings because

phytoplankton growth is limited by the naturally high

turbidity in this estuary. The widespread eutrophication

that was common in the upper Chesapeake Bay during

the 1960s and 1970s has been successfully reduced, in

large part by improved nutrient management practices.

Eutrophication is increasingly noticeable in the dead end

canals along developed shorelines in the Delmarva

coastal bays. Chlorophyll levels presently are low in

off-shore waters, but there is evidence that levels may

be increasing.

 Dissolved oxygen (DO) is a fundamental requirement for estuarine organisms. During the critical late

summer time period, 17% of the estuarine bottom

waters of the region exhibit moderate hypoxia (DO

between 2 and 5 mg/L) and 8% exhibit severe hypoxia

(DO less than 2 mg/L). Chesapeake Bay is the most

hypoxic estuary, largely due to natural processes (water

column stratification) made worse by nutrient enrichment and eutrophication. The Delaware Estuary and

the Delmarva coastal bays have small areas of hypoxia. Low dissolved oxygen does not appear to be of

concern in coastal waters. Poor condition of bottomdwelling organisms is strongly associated with decreased DO levels.

 Sediment contamination with trace metals, PAHs,

PCBs, and pesticides, and the associated potential

toxicity of these sediments, are considered by the public

to be a major threat to estuaries in the Mid-Atlantic

Region. More than half of the estuarine sediments in the

region have contaminant levels considered to be acceptable. Less than 10% of the sediments contain contaminant levels considered to pose a potential risk of effects

to aquatic organisms. Most of the contaminated areas

are adjacent to historical urban, industrial, and agricultural

sources. In general, sediment contaminant levels in the

region have been decreasing over the last decade.

36
Summary

37

 The historical loss of coastal wetlands in the

Mid-Atlantic estuaries has largely been stabilized by

state and federal conservation plans, even though there

is a continuing loss of wetlands in upland areas. The

challenge now is to ensure that the wetlands are

healthy despite severe anthropogenic stresses. The

precipitous loss of submerged aquatic vegetation

(SAV) in Chesapeake Bay during the 1970s also has

been checked. SAV beds are returning to Chesapeake

and Chincoteague Bays in response to diminished

eutrophication associated with improved nutrient

management practices. SAV historically has been

absent from the Delaware Estuary and the Delaware

portion of the Delmarva coastal bays because of high

natural turbidity in these estuaries.

 Impacted benthic communities can be found in all of

the major estuarine systems of the Mid-Atlantic, but

are most prevalent near urban centers such as Philadelphia, Baltimore, Washington, and Norfolk; and in areas

suffering from low dissolved oxygen. The most

prominent association of impacted benthic communities

in Mid-Atlantic estuaries is with low dissolved oxygen

concentrations in bottom waters. This condition is

located primarily in Chesapeake Bay.

 Harvest of the American oyster (Crassotrea

virginica) traditionally has been one of the major

Mid-Atlantic industries but it is now one of the most

seriously threatened. The decline in the oyster industry

has been precipitous, declining from an annual catch of

133 million pounds in 1880 to about one million pounds

today. The primary causes for the recent demise of the

oyster fishery are the oyster diseases Dermo and MSX,

with overfishing and pollution contributing. Scientists

currently are investigating the feasibility and ecological

consequences of introducing disease-resistant strains of

oysters to Mid-Atlantic estuaries to reestablish the

fishery.

 Another important component of the shellfish industry

in the Mid-Atlantic region is the blue crab

(Callinectes sapidus). Annual harvest of blue crabs

has been variable over the past decades, especially for

the Delaware Estuary. This variability likely is due

predominantly to natural environmental factors compounded by fishing pressures. Although the annual

catch of crabs has not decreased significantly, the

catch per unit effort has. The current harvest is being

kept up by increased effort, not neccessarily stable

populations. Scientists are concerned because the

increased fishing pressure would make it difficult for

crab populations to recover if they were impacted by

severe environmental conditions such as occurred in

the Delaware Estuary in 1977 and 1981 (unusually

severe winters).

 Each state monitors their estuarine waters for coliform

bacteria and closes those waters to shellfishing when

the concentration reaches a critical level. Shellfishing is

prohibited or restricted in approximately 10% of the

3,660,000 acres of potentially productive shellfish

ground in the Mid-Atlantic estuaries. These closings

can be attributed to contamination from a variety of

sources, including sewage treatment plants, leaking

septic systems, marinas, industry, wildlife, boating and

runoff. The closings also may be administrative in

nature (e.g., inadequate monitoring to ensure the

waters are safe). Considering the degree of urbanization in the area, it is encouraging that only a relatively

small percentage of the area is closed to shellfishing.

In addition, improvements in wastewater treatment

have led to a decrease in closed acreage, from 18% in

1985 to 10% in 1995.

 Fish abundance, distribution, and condition are considered indicators of ecosystem health because fish

integrate effects of environmental stress over space

and time. The Mid-Atlantic Region contains many

habitat types, making region-wide judgements about

fish populations difficult. In addition, market forces and

environmental fluctuations obscure causes of fish

population declines. Nevertheless, scientists have

documented improvements for some species. For

example, striped bass and American shad populations

are improving after significant historical declines. This

is due to reductions in fishing pressure from restrictions

that have been, or still are, in effect. Scientists also

attribute the observed recovery to improved water

quality. Species composition of shore zone fish in the

Delaware coastal bays indicate impacted environmental

conditions. In contrast, Maryland coastal bays species

composition suggests a healthy habitat; however,

researchers have observed evidence of initial degradation in northern areas.

 Fish and shellfish contaminant levels throughout

the region appear to be decreasing over time due to

bans and restrictions on the use of such chemicals as

PCBs, DDT, and Kepone and stricter limits on point

source discharges. The contaminant concentrations in

fish and shellfish generally are at or below the national

averages; however, much higher levels may be present

in organisms collected near urbanized areas, such as

Baltimore Harbor. Generally, contaminant levels in

fish and shellfish are higher in the Delaware Estuary

than in Chesapeake Bay or the Delmarva coastal

bays, perhaps reflecting the degree of urbanization in

the estuarine watersheds.

 EPAs Environmental Monitoring and Assessment

Program included a pathological examination of

13,467 fish from 177 stations in the Mid-Atlantic
estuaries. Only three per thousand examined were

afflicted with external pathological abnormalities,

indicating a low incidence of such abnormalities. This is

considerably lower than the 10 per thousand determined

by EMAP for the estuaries of the Gulf of Mexico.

 In general, Mid-Atlantic waterfowl populations are in

relatively good condition. The major factors affecting

these birds are local habitat alteration associated with

human development and environmental conditions in

other areas along the birds migratory path. Of some

concern is the fact that favorable environmental conditions over the past few years in other parts of the

country where migratory birds nest during the summer

have resulted in increased populations of those birds, but

that increase is not being seen in the Mid-Atlantic.

Many of those birds are favoring other wintering sites,

such as along the Gulf of Mexico. One possible explanation is habitat loss in the highly developed Mid-Atlantic.

 The Mid-Atlantic Region has experienced some of the

most rapid population growth, industrial development,

and intensive agriculture in the country. Many organisms relying on the estuaries of the Mid-Atlantic have

suffered. In the states surrounding the estuaries of the

Mid-Atlantic, numerous species of plants and animals are

listed as threatened or endangered and virtually every

county has at least one listed species. It is encouraging

that the threatened and endangered species directly

associated with the estuaries are improving.

Table 1 is an environmental report card for the estuaries of the Mid-Atlantic Region. For the entire region and

each of the major systems, we assigned a color representing the condition of individual indicators. These colors

represent our best judgment summarization of the

information presented in this report. Where multiple

colors are shown, our best estimate is that condition

ranges between the two categories. Problem areas are

determined by individual indicator values. The table does

not imply that problem areas are always man-induced.

The pervasive issues across the Mid-Atlantic Region

include shellfish harvest for oysters and disease in

shellfish. Shellfish, particularly the American oyster,

traditionally have been one of the major living resources

harvested in the Mid-Atlantic states. Oyster harvests

have declined from a high of 133 million pounds in 1880 to

todays 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 oyster

populations in Chesapeake Bay and the Delaware

Estuary, with over-harvesting and pollution also playing a

major role in 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.

With the decline of the oyster industry, the most important

shellfish industry in the Mid-Atlantic Region is now the

blue crab. However, the significantly increased fishing

pressure on the already heavily exploited population is

beginning to take its toll. To avoid a serious impact, both

Maryland and Virginia have placed restrictions on

crabbing in Chesapeake Bay waters.

The Delaware Estuary is characterized by an historical

lack of submerged aquatic vegetation (SAV), due predominantly to naturally-occurring low water clarity. It is

also one of the most nutrient enriched estuaries in the

world, although harmful phytoplankton blooms are held in

check by other factors, including low water clarity. The

estuary also is highly impacted by lingering toxic contaminants associated with urbanization and industrialization of

the Delaware River. The Delaware Estuary has some of

the nations highest levels of chemical contaminants in

fish and shellfish. Fishing bans or advisories on the

consumption of finfish are posted for portions of the

estuary because of elevated PCB concentrations.

Concentrations of Chlordane in fish exceeding the FDA

action level have been reported in the upper estuary.

Chesapeake Bay continues to be affected by low

dissolved oxygen and is the most hypoxic estuary in the

region. Low dissolved oxygen levels are associated with

nutrient overenrichment and eutrophication. In 1987, the

Chesapeake Bay Agreement stipulated a 40% reduction

in nutrient loading by the year 2000. Nutrient levels in

Chesapeake Bay 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). However, there has been more success in controlling point sources than nonpoint sources of nutrients.

Historically, high nutrient concentrations have contributed

to prolonged phytoplankton blooms in the Bay. Blooms

occurring during the 1970s and 1980s significantly

reduced water clarity and, as a result, contributed to the

massive loss of SAV that occurred during that time

period. This critical habitat has since partially recovered.

The Delmarva coastal bays are the least degraded

systems in the Mid-Atlantic Region but are threatened by

encroaching urbanization. The coastal bays are moderately enriched, particularly in Delaware, largely from

agricultural sources. Eutrophication is increasingly

noticeable in the dead end canals along developed

shorelines in the Delmarva coastal bays. SAV historically

has been absent from the Delaware portion of the coastal

bays because of high natural turbidity in these systems.

Species composition of shore zone fish in the Delaware

coastal bays indicates impacted environmental conditions.

In contrast, Maryland coastal bays species composition

suggests a healthy habitat; however, researchers have

Summary

38
39

observed evidence of early stages of degradation in

northern areas.

Coastal waters presently exhibit low levels of nutrients

and chlorophyll. However, evidence suggests that these

levels may be rising, indicating the potential for future

environmental problems.

The mix of colors in Table 1 indicates that the estuaries

of the Mid-Atlantic Region are being impacted. ThereTable 1. Summary of ecological conditions across the Mid-Atlantic estuaries. Colors represent the best estimate of

condition based upon information presented in this reportgreen for good condition, yellow for a moderate problem,

and red for a problem. A lack of color indicates that inadequate information was available. Where multiple colors are

shown, our best estimate is that condition ranges between the two categories. Problem areas are determined by

individual indicator values. The table does not imply that problem areas are always man-induced.

Summary

fore, they are at risk and in need of active management

to restore and maintain environmental quality and

sustainable resources. The states, in conjunction with

the Chesapeake Bay Program and the National Estuary

Programs, have instituted environmental

management programs to address

these concerns. We now are seeing

the positive results of these environmental programs.
The following sources of information were used in the

preparation of this report or may be of interest to the

reader.

PUBLICATIONS

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figures. October 10, 1996 draft.

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Investigation of Marylands Atlantic Ocean and

Coastal Bays Finfish Stocks. Maryland Department

of Natural Resources, Tidewater Administration, Tawes

State Office Building.

Cerco, C.F., B. Bunch, M.A. Cialone and H. Wang.

1994. Hydrodynamics and Eutrophication: Model

Study of Indian River and Rehoboth Bay, Delaware.

USACE. Technical Report EL - 94-5.

Chaillou, J.C., S.B. Weisberg, F.W. Kutz, T.E. DeMoss,

L. Mangiaracina, R. Magnien, R. Eskin, J. Maxted, K.

Price, and J.K. Summers. 1996. Assessment of the

Ecological Condition of the Delaware and Maryland

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Protection Agency, Office of Research and Development, Washington, D.C.

Chesapeake Bay Program. 1992. Submerged

Aquatic Vegetation Habitat Requirements and

Restoration Targets: A Technical Synthesis. CBP/

TRS 83/92. 186 pages plus appendices.

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Finfish/Shellfish Tissue Contamination Critical Issue

Forum Proceedings. CBP/TRS 97/93.

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in Chesapeake Bay, 1984-1992. CBP/TRS/115/94.

63 pages.

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Basinwide Toxics Reduction Strategy Reevaluation

Report. CBP/TRS 117/94. 192 pages plus appendices.

Chesapeake Bay Program. 1995. Trends in the

Distribution, Abundance, and Habitat Quality of

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and its Tidal Tributaries: 1971-1991. CBP/TRS 137/

95. 158 pages plus appendices.

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Indicators: Measuring Our Progress. 83 pages.

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Bay Program. http://chesapeakebay.net/bayprogram/

measure/indicatr/indover.htm

Costa, H.J. and T.C. Sauer. 1994. Distributions of

Chemical Contaminants and Acute Toxicity in

Delaware Estuary Sediments. DELEP Report # 94-

08, Report prepared for Delaware Estuary Program by

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Culliton, T.J., M.A. Warren, T.R. Goodspeed, D.G.

Remer, C.M. Blackwell, and J.J. McDonough, III.

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Series. National Oceanic and Atmospheric Administration,

National Ocean Service, Ocean Assessments Division,

Strategic Assessment Branch, Rockville, MD.

Delaware Inland Bays Estuary Program. 1992. Characterization of the Inland Bays Estuary. Weston Consultants.

Delaware DNREC. 1994. Delaware DNREC News.

Vol. 24, No. 169. Doc. # 40-01/94/06/07. Delaware

Department of Natural Resources and Environmental

Control, Dover, DE.

Delaware DNREC. 1996. Delaware DNREC News.

Vol. 26, No. 75. Doc. # 40-01/96/04/19. Delaware

Department of Natural Resources and Environmental

Control, Dover, DE.

Delaware Estuary Program. 1996. The Delaware

Estuary. Discover its Secrets. A Management Plan

for the Delaware Estuary. Comprehensive Conservation and Management Plan for the Delaware Estuary,

Delaware Estuary Program.

Dove, L.E. and R.M. Nyman, Eds. 1995. Living

Resources of the Delaware Estuary. The Delaware

Estuary Program. 530 pages plus appendices.

40
Sources of Information

41

Field, D.W., A.J. Reyer, P.V. Genovese, and B.D.

Shearer. 1991. Coastal Wetlands of the United States.

National Oceanic and Atmospheric Administration,

Rockville, MD. 59 pages.

Frithsen, J. B., K. Killam, and M. Young. 1991. An

Assessment of Key Biological Resources in the

Delaware River Estuary. Delaware Estuary Program

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DATABASES AND

ORGANIZATIONS

Chesapeake Bay Program

Delaware Department of Natural Resources &

Environmental Control

a) Division of Water Resources

(shellfish information)

b) Watershed Assessment Branch

(contaminants in fish and shellfish)

Haskin Shellfish Laboratory, Rutgers University,

Bivalve, NJ

Maryland Department of Natural Resources

Maryland Department of the Environment

NOAA, Chesapeake Bay Office, Fisheries Statistics

Database

NOAA, National Marine Fisheries Service, Fishery

Statistics Division

U.S. Fish and Wildlife Service

a) Mid-Winter Migratory Bird Survey, Annapolis, MD

office (waterfowl information)

b) Endangered Species Home Page

http://www.fws.gov/~r9endspp/endspp.html

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EPA, Atlantic Ecology Division, Narragansett, RI.

Virginia Department of Health, Division of Shellfish

Sanitation

Virginia Marine Resources Commission

Sources of Information

EROS Data Center, Sioux Falls, South Dakota.

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R. Allen. 1996. Temporal trends in abundance of

fish in the tidal Delaware River. Estuaries 19(3):

723-729.

Weisberg, S.B., J.A. Ranasinghe, L.C. Schaffner, R.J.

Diaz, D.D. Dauer, and J.B. Frithsen. 1997. An Estuarine Benthic Index of Biotic Integrity (B-IBI) for

Chesapeake Bay. Estuaries, 20(1):149-158.
Advisory Level: Chemical concentration in fish or

shellfish above which consumption of the fish would

pose a human health risk. Levels may be determined by

various federal or state agencies and may lead to

advisories such as restricted consumption or consumption bans. Typical chemicals for which advisories exist

include PCBs, chlordane, and dioxin.

Algae: Simple rootless plants that grow in bodies of

water (e.g., estuaries) at rates in relative proportion to

the amounts of nutrients (e.g., nitrogen and phosphorus)

available in the water.

Anadromous Fish: Fish that spend their adult lives in

the sea but swim upriver into fresh water to spawn

(e.g., striped bass, American shad).

Anoxic (anoxia): A condition where very little or no

oxygen is present in the water body.

Anthropogenic: Originating from man, not naturally

occurring.

Atmospheric Deposition: The flux (flow) of chemicals

and materials from the atmosphere to the earths

surface. Depending on the chemical or material, dry

deposition (e.g., by particles) can be less than, equal to,

or greater than wet deposition (e.g., precipitation).

Benthos: Plants or animals that live in or on the bottom

of an aquatic environment such as an estuary.

Bioaccumulation (bioaccumulate): The uptake and

storage of chemicals (e.g., DDTs, PCBs) from the

environment by animals and plants. Uptake can occur

through feeding or direct absorption from water or

sediments.

Biomagnification: The progressive increase in the

concentration of chemical contaminants (e.g., DDTs,

PCBs, methyl mercury) from the bottom (e.g., phytoplankton, benthic animals) to the top of the food web

(e.g., striped bass).

Brackish: Having a salinity between that of fresh and

sea water.

Catch per unit effort (CPUE): A term used in fisheries

science to standardize catch information. For example,

the CPUE for blue crab harvest might be described as the

number of crabs caught per crab pot per day.

Chlorophyll: A group of green pigments found in most

plants, including phytoplankton, which they use for

photosynthesis. The individual pigment generally

measured is chlorophyll a. For the sake of clarity we

use chlorophyll throughout this document; however,

we are specifically referring to chlorophyll a.

Coliform bacteria: A group of bacteria primarily found

in human and animal intestines and wastes. These

bacteria are widely used as indicator organisms to show

the presence of such wastes in water and the possible

presence of pathogenic (disease-producing) bacteria.

Escherichia coli (E. coli) is one of the fecal coliform

bacteria widely used for this purpose.

Community: The assemblage of populations of plants

and animals that interact with each other and their

environment. The community is shaped by populations

and their geographic range, the types of areas they

inhabit, species diversity, species interactions, and the

flow of energy and nutrients through the community.

Contamination: The impairment of water, sediments,

plants, or animals by chemicals or bacteria to such a

degree that it creates a hazard to public and environmental health through poisoning, bioconcentration

(bioaccumulation), or the spread of disease.

Continental Shelf: A gently sloping submarine plane of

varying width between the shoreline of a continent and

the continental slope, a steep slope which extends into

the oceanic abyss.

Crustacean: Any of various predominantly aquatic

arthropods of the class Crustacea, including lobsters,

crabs, shrimps, and barnacles, having segmented bodies,

a chitinous exoskeleton, and paired, jointed limbs

(appendages).

DDT: A group of colorless chemicals used as insecticides. DDTs are toxic to man and animals when

swallowed or absorbed through the skin.

Delmarva Peninsula: The land separating Chesapeake Bay from the Atlantic Ocean. The Delmarva

Peninsula falls within the states of Delaware, Maryland,

and Virginia, from which it gets its name - Delmarva.

44
Glossary

45

Depurate: To cleanse. For example, shellfish contaminated with coliform bacteria can be placed in clean

seawater to depurate. Clean water flowing through the

organism will remove the bacteria over a period of time.

Note that this process does not apply to all contaminants

(e.g., chlorinated pesticides).

Dermo: Oyster disease caused by the protozoan

parasite, Perkinsus marinus.

Detritus: Non-living organic matter (e.g., dead organisms or leaves) in water.

Dissolved Oxygen: Oxygen that is dissolved in water

and therefore available for plants (phytoplankton),

shellfish, fish, and other animals to use. If the amount

of oxygen is too low, aquatic plants and animals may

die. Wastewater and naturally occurring organic matter

contain oxygen-demanding substances that, when

decomposing, consume dissolved oxygen.

Ecosystem: A natural unit formed by the interaction of

a community of plants and animals with their environment (physical and biological).

Effluent: The discharge to a body of water from

a defined or point source, generally consisting of a

mixture of waste and water from industrial or municipal

facilities.

EMAP: Environmental Monitoring and Assessment

Program - an EPA Office of Research and Development research program.

Endangered: A species that is in immediate danger of

becoming extinct and needs protection to survive.

Estuary (estuaries): Regions of interaction between

rivers and near-shore ocean waters, where tidal action

and river flow mix fresh and salt water. Such areas

include bays, mouths of rivers, salt marshes, and

lagoons. These brackish water ecosystems shelter and

feed marine life, birds, and wildlife.

Eutrophic: Highly productive condition, generally the

result of nutrient enrichment in the water column that

may cause algae (e.g., phytoplankton) to bloom.

Eutrophication: A condition in an aquatic ecosystem

where high nutrient concentrations stimulate blooms of

algae (e.g., phytoplankton). Algal decomposition may

lower dissolved oxygen concentrations. Although

eutrophication is a natural process in the aging of lakes

and some estuaries, it can be accelerated by both point

and nonpoint sources of nutrients.

Extinct: A species of plant or animal that is no longer

living.

Fall Line: A break in the flow of all rivers as they

flow from the Appalachian plateau to the Atlantic

coastal plain. This region is characterized by the

transition of steep, rapidly flowing streams to wider,

slower rivers. Large cities are frequently located at the

fall line since this represents the upward limit of navigation from the sea.

Fecundity: Fish reproduction potential. Fecundity is

usually measured by the number of eggs a female

produces.

Filter Feeder: Animals (e.g., clams and oysters) that

feed by filtering out of the water column small food

items such as detritus, phytoplankton, and zooplankton.

Filter feeders also are known as suspension feeders.

Fish Consumption Advisory: An advisory issued by

state government agencies and used to reduce human

health risks associated with exposure to chemical

contaminants (e.g., PCBs, DDTs, mercury) found in

fish and shellfish. Advisories may recommend bans and

restricted consumption of specific species in specific

geographical areas of an estuary.

Food Web: An assemblage of organisms in an ecosystem, including plants, herbivores, and carnivores, which

shows the relationship of who eats whom.

Habitat: The place where a population or community

(e.g., micro-organisms, plants, animals) lives and its

surroundings, both living and non-living.

Hot Spot: A problem area or location where pollution,

especially a chemical concentration, is very high.

Generally located near urbanized areas or point-source

discharges.

Hybrid: The offspring of two animals or plants of

different races, breeds, varieties, species or genera.

Hypoxia: A condition where very low concentrations

of dissolved oxygen are in the water column.

Invertebrates: Animals that lack a spinal column or

backbone, including molluscs (e.g., clams and oysters),

crustaceans (e.g., crabs and shrimp), insects, starfish,

jellyfish, sponges, and many types of worms that live in

the benthos.

Land Cover: Anything that exists on, and is visible

from above, the earths surface. Examples include

vegetation, exposed or barren land, water, snow, and

ice.

Land Use: The way land is developed and used in

terms of the kinds of anthropogenic activities that occur

(e.g., agriculture, residential areas, industrial areas).
Larvae (larva): Early form of an animal that is unlike

its parent and must metamorphose before assuming

adult characteristics.

Macroalgae: Non-rooted aquatic plant. Commonly

referred to as seaweed.

Marsh: A wetland where the dominant vegetation is

non-woody plants, such as salt grasses and sedges, as

opposed to a swamp, where the dominant vegetation

consists of woody plants such as trees and shrubs.

Mid-Atlantic Estuaries: In this document, they are

defined as Delaware Bay and its tributaries, Chesapeake Bay and its tributaries, and the coastal bays of

the Delmarva Peninsula.

Mid-Atlantic Region: For the purpose of this report

this is defined as the watershed of the Chesapeake Bay,

Delaware Estuary, and the Delmarva coastal bays. It

includes all or portions of Virginia, West Virginia,

Maryland, Delaware, Pennsylvania, New Jersey, and

New York.

MSX: An oyster disease caused by the protozoan

parasite, Haplosporidium nelsoni.

Nonpoint Source: Refers to pollution that enters water

from dispersed and uncontrolled sources, such as

surface runoff, rather than through pipes.

Nutrients: Essential chemicals (e.g., nitrogen and

phosphorus) needed by plants for growth. Excessive

amounts of nutrients can lead to degradation of water

quality by promoting excessive growth, accumulation,

and subsequent decay of plants, especially algae

(phytoplankton).

Pathological condition: Abnormal anatomic or

physiological condition.

Pesticides: A general term used to describe chemical

substances that are used to destroy or control insect or

plant pests. Many of these substances are manufactured and do not occur naturally in the environment.

Others are natural toxins that are extracted from plants

and animals. Chlordane, DDT, and Kepone are examples of pesticides.

Polychlorinated Biphenyls (PCBs): A group of

closely related and manufactured chemicals made up of

carbon, hydrogen, and chlorine. PCBs can persist for a

long time in the environment and they can bioaccmulate

and biomagnify in aquatic food webs. PCBs are

suspected of causing cancer in humans. They are an

example of an organic contaminant.

Phytoplankton: Small, often single-celled plants that

live suspended in bodies of water (e.g., estuaries).

Phytoplankton Bloom: A sharp increase in the

population of phytoplankton, as often occurs in the

spring, summer, or fall in different areas of an estuary.

Point Source: Refers to a source of pollutants from a

single point of conveyance, such as a pipe. For example, the discharge from a sewage treatment plant or

factory is a point source.

Polycyclic Aromatic Hydrocarbons (PAHs): A class

of chemical compounds composed of fused six-carbon

rings. PAHs are commonly found in petroleum oils

(e.g., gasoline and fuel oils) and are emitted from

various combustion processes (e.g., automobile exhausts, electric companies).

ppm: Parts per million; equivalent to microgram per

gram (lg/g) or milligrams per liter (mg/L).

ppt: Parts per thousand (used as a measurement of

salinity).

Recruitment: Entry of fish into a fishery either through

the attainment of a size large enough to be taken by a

fishery or from an external source (e.g., fish entering an

estuary from the ocean). Recruitment also can refer to

fish reaching sexual maturity for non-exploitable species.

Salinity: A measurement of the amount of salt in

water. Generally reported as parts per thousand (i.e.,

grams of salt per 1,000 grams of water) and abbreviated

as ppt or . Salinity also is reported as practical

salinity units and abbreviated as psu.

Salt Marsh: Class of wetlands consisting of salttolerant grasses and other plants that are periodically

exposed to salt water flooding.

Sediment: Mud, sand, silt, clay, shell debris, and other

particles that settle on the bottom of rivers, lakes,

estuaries, and oceans.

Seine Survey: A fish capturing procedure where fish

are enclosed and drawn to shore using a large net with

sinkers on one edge and floats on the other.

Shellfish: An aquatic animal, such as a mollusc (e.g.,

clams, oysters, and snails) or crustacean (e.g., crabs

and shrimp), having a shell or shell-like external skeleton

(exoskeleton).

Spatial Extent: As used in this document, the total area

(water and land) where a condition (e.g., shellfish

diseases) or populations of plants and animals are found.

Spawning: Sexual reproduction in fish.

Species: A group of individuals similar in certain

46

Glossary
47

morphological and physiological characteristics that are

capable of interbreeding and are reproductively isolated

from all other such groups.

Stratification: The formation, accumulation, or deposition of materials in layers, such as layers of fresh water

overlying higher salinity water (salt water) in estuaries.

Submerged Aquatic Vegetation (SAV): Rooted

vegetation that grows under water in shallow areas of

estuaries where light can penetrate to the bottom

sediments.

Substrate: A surface on which a plant or animal grows

or is attached.

Suspended Sediments: Particles of soil, sediment,

living material, or detritus suspended in the water

column.

Threatened: A species that is likely to become endangered if not protected.

Tidal Mud Flat: The unvegetated shore exposed to air

during low tide.

Tissue Residues: Chemical contaminants present in

fish or shellfish and usually concentrated in the tissues

(e.g., muscle, liver) as opposed to the bones or shell.

Toxic Substances (or material): Chemical compounds

that are poisonous, carcinogenic, or otherwise directly

harmful to plants and animals.

Trace Metals: Metals such as silver, copper, lead,

cadmium, zinc, and mercury that normally occur in

water and sediments at concentrations less than one

part per million (ppm).

Tributary (Tributaries): A body of water flowing into

a larger body of water. For example, the Potomac

River is a tributary of Chesapeake Bay.

Trophic level: A grouping of organisms that uses the

next lower grouping of organisms as a food source.

Used to describe where on the food web (see definition

of Food Web in this glossary) organisms feed. For

example herbivores feed on plants, and carnivores feed

on herbivores.

Turbidity: The clouding of a naturally clear liquid due

to suspended solids. Because turbidity reduces the

amount of light penetrating the water column, high

turbidity levels may be harmful to aquatic life (e.g.,

SAV).

Virulent: Extremely poisonous or venomous. Regarding a disease, virulent is defined as the ability to rapidly

overcome bodily defensive mechanisms.

Water Clarity: Measurement of how far you can see

through the water. The greater the water clarity, the

further you can see through the water.

Water Column: The water between the surface and

bottom of a river, lake, estuary, or ocean.

Watershed: The entire area of land whose runoff of

water, sediments, and dissolved materials (e.g., nutrients, contaminants) drain into a river, lake, estuary, or

ocean.

Wetlands: An ecosystem type, generally occurring

between upland and deepwater areas, that provides

many important functions, including fish and wildlife

habitat, flood protection, erosion control, water quality

maintenance, and recreational opportunities.

Young-of-the-Year: Fish produced in the current

years spawn. Fish less than 1 year old.

Zooplankton: Small, sometimes microscopic animals

that float in the water. They feed on detritus, phytoplankton, and other zooplankton. They are eaten by

fish, shellfish, whales, and other zooplankton.

Glossary
Criteria used for presenting

indicator data

Stratification

Sigma-t is a measure used in physical oceanography to

describe water density. It is a measurement of the

density that a parcel of water with a given temperature

and salinity would have at the surface (i.e., at atmospheric pressure), and is expressed as (density - 1) *

1000 (Strobel et al., 1995). The degree of water

column stratification is determined from the difference

in sigma-t between surface and bottom waters. The

three categories used to summarize stratification are

low (sigma-t difference less than 1), moderate (sigma-t

difference between 1 and 2), and high (sigma-t difference greater than 2) stratification.

Water Clarity

The clarity of estuarine water is determined by a

measure of the attenuation of sunlight through the water

column. It is measured by an attenuation coefficient,

which is the natural logarithm of the ratio of the intensity of light of a specified wavelength on a horizontal

surface to the intensity of the same wavelength light on a

horizontal surface 1 m deeper in the water (Strobel et al.,

1995). We define poor water clarity as an attenuation

coefficient greater than 2.30, which is equivalent to the

transmission of 10% of the light incident on the water

surface to a depth of 1 m. Fair water clarity is defined

for an attenuation coefficient between 1.39 and 2.30,

which is equivalent to the transmission of 25% of the light

incident on the water surface to a depth of 1 m. Good

water clarity refers to an attenuation coefficient of less

than 1.39.

Nutrients

The nutrient levels of Figure 8 show the concentrations

of dissolved inorganic phosphate (DIP) and dissolved

inorganic nitrogen (DIN, calculated as the combined

values of dissolved inorganic nitrate and ammonium

ions). These values were measured in surface waters

during the summer months. The conditions for Chesapeake Bay reflect data collected annually from 1985

through 1995, while the Delaware Estuary data were

collected in 1986 and 1987, and the coastal bays data

were measured in 1993.

The classification scale for DIN is: good, < 0.15 mg N/L

(ppm); fair, 0.15 - 0.45 ppm; and poor, > 0.45 ppm. For

DIP, the scale is: good, < 0.02 mg P/L (ppm); fair, 0.02

- 0.06 ppm; and poor, > 0.06 ppm. For mesohaline

waters (medium saltiness, defined as salinities from 5-18

ppt), the criterion for good DIP levels is <0.01 ppm.

To be conservative with respect to statistical confidence, a region is classified using the upper limit of its

90% confidence interval. For example, the average

DIP and standard deviation in Assawoman Bay is 0.090

± 0.033 ppm. Thus 90% of all DIP values measured in

this bay are 0.156 ppm or less (calculated as the mean

plus two standard deviations). Therefore, Assawoman

Bay is designated as fair based on this conservative

upper limit for DIP.

The boundary between good and fair nutrient categories

are the values set by the Chesapeake Bay Program as

the criteria necessary to promote continued survival of

submerged aquatic vegetation (SAV) in Chesapeake

Bay (Chesapeake Bay Program, 1992). The boundary

between fair and poor is three times the lower criteria,

comparable to the various criteria used in different

studies. Caution is advised in drawing conclusions

based on these classification limits for several reasons.

First, the SAV-related criteria were developed specifically for use in Chesapeake Bay and their applicability

in other estuaries is uncertain and currently is under

investigation. Also, the relationships between nutrient

enrichment and eutrophication are complex and involve

more details than were discussed in the text. For

example, excess phosphorus promotes eutrophication in

the less salty tributaries, while nitrogen encourages

blooms in saltier open waters. Therefore, while the

poor DIN conditions in the upper Chesapeake Bay

and the Delaware Estuary are indications of high

nutrient concentrations, they do not necessarily imply

high potential for eutrophication. Furthermore, in some

places such as the Delaware Estuary, blooms are

inhibited by muddy waters despite high levels of nutrients. In summary, Figure 8 is an accurate comparison of

nutrient concentrations in the Mid-Atlantic Region

48
Technical Appendix

49

estuaries. However, the interpretation of nutrient

enrichment with respect to eutrophication should be

performed carefully and is an area of active research.

Phytoplankton

Chlorophyll a is a measure of the green pigment in

phytoplankton. Concentrations of chlorophyll a in

surface waters measured during the summer months is

used to represent phytoplankton levels. The conditions

for Chesapeake Bay reflect data collected annually from

1985 through 1995, the Delaware Estuary data were

collected in 1986 and 1987, and the coastal bays data

were measured in 1993. The scale for the criteria is:

good, < 15 mg/L; fair, 15-30 mg/L; poor, > 30 mg/L. To

be conservative with respect to statistical confidence, a

region is classified according to the upper limit of its 90%

confidence interval (see note regarding nutrients for

further explanation). The boundary between good and

fair nutrient categories are the values set by the Chesapeake Bay Program as the criteria necessary to promote

continued survival of submerged aquatic vegetation

(SAV) in Chesapeake Bay. The boundary between fair

and poor is comparable to the various criteria used in

different studies.

Dissolved Oxygen

Dissolved oxygen (DO) is a fundamental requirement

for the maintenance of balanced indigenous populations

of fish, shellfish, and other aquatic biota. Most estuarine

populations can tolerate short exposures to low dissolved oxygen concentrations. However, prolonged

exposures to less that 60% oxygen saturation may result

in altered behavior, reduced growth, adverse reproductive effects, and mortality. Exposure to less than 30%

saturation (~ 2 mg/L for seawater at summer temperatures) for one to four days causes mortality to most biota,

especially during summer months, when metabolic rates

are high. Stresses that can occur in conjunction with low

dissolved oxygen (e.g., exposure to hydrogen sulfide or

ammonia) may cause as much, if not more, harm to

aquatic biota than exposure to low dissolved oxygen

concentration alone. In addition, aquatic populations

exposed to low dissolved oxygen concentration may be

more susceptible to adverse effects of other stressors

(e.g., disease, toxic substances).

The biologically important value is species-dependent,

and the regulatory values vary among states in the

Region. For comparison purposes in this report, thresholds of 2 and 5 mg/L are used for DO measured in the

bottom waters. A concentration of approximately 2 mg/

L often is used as a threshold for oxygen concentrations

thought to be extremely stressful to most estuarine

biota. A threshold concentration of 5 mg/L is used by

many states to set water quality standards. The U.S.

EPA, as of this writing, has not established DO water

quality criteria for estuarine and marine waters, but is in

the process of developing the database from which

criteria will be developed. Data available for preparation of Figure 13 were from daylight observations.

Region-wide estimates of possible night time depression

of DO were not available.

Sediment Contamination

Informal guidelines for interpreting sediment contamination based on many field and laboratory studies have

been developed. These guidelines attempt to relate

observed chemical concentrations to concentrations

known to either cause biological effects in laboratory

spiked-sediments or spiked-water experiments, or be

associated with biological effects in field studies.

Examples of these approaches are the Puget Sound

(Malek, 1992) apparent effects thresholds (AETs); State

of Washington (Phillips, et al., 1988) screening level

concentrations (SLCs); Long and Morgans (1990), as

updated in Long et al. (1995), effects range median

(ER-M) and effects range low (ER-L) concentrations;

and refinements to Long and Morgan by MacDonald

(1994) for potential effects level (PEL) and threshold

effects level (TEL). These approaches benefit from the

weight of evidence afforded by large data sets associating sediment contaminant concentrations with biological

effect, but suffer from a failure to incorporate the effects

of multiple chemicals in complex mixtures, as the chemicals exist in the environment.

While these approaches have shortcomings, they are the

best overall benchmarks available for assessing sediment contamination for a wide variety of contaminants.

The Long and Morgan ER-Ls and ER-Ms and

MacDonalds TELs and PELs are used in this report to

summarize sediment contamination in estuaries of the

Mid-Atlantic Region. The no risk category represents

areas with no contaminants in excess of ER-L or TEL

values. The minimal risk category represents areas

with contaminants in excess of threshold ER-L/TEL

values but below higher probable-effect ER-M/PEL

values. The potential risk category represents areas

with contaminants in excess of probable-effect ER-M/

PEL values. It should be noted that this categorization

does not account for the potential role of sub-lethal

effects of contamination, such as susceptibility to

disease or impairment in growth and reproduction.
Benthic Condition

The numbers of animals of each species observed at a

location has been a basic measure used by benthic

ecologists to describe the condition of the benthic

community. More recently, estuarine scientists have

been conducting research on ways to combine individual

pieces of information about benthic communities into a

single measure that tracks the condition of benthic

communities, similar to how the Dow Jones average is

used to track the condition of the stock market. Two

examples of this approach for the Mid-Atlantic Region

are the Chesapeake Bay benthic restoration goal index

(RGI) and the EPA Environmental Monitoring and

Assessment Program (EMAP) benthic index (BI). We

have used information from the Chesapeake Bay and

EMAP approaches to characterize the condition of

benthic communities in the Mid-Atlantic Region.

The RGI was developed by examining benthic communities from areas relatively free of pollution and comparing them with those in areas more affected by pollution

(Weisberg et al., 1997). A score is assigned based

upon attributes of the benthic community, such as

number of species, total number and mass of organisms,

presence of organisms in deeper layers of the sediment,

and relative abundance of species that are tolerant of

pollution. The scores for each of the attributes are

averaged to give an overall rating of the communitys

condition, then aggregated to the following three categories meets goals, impacted, and severely impacted

(USEPA, 1995).

The EMAP BI is an attempt to reduce many individual

measures of the benthic community into a single number

that has a high level of discriminatory power between

good and poor environmental conditions (Strobel et al.,

1995; Paul et al., 1997). Independent measures of

environmental conditions, such as dissolved oxygen

concentrations and sediment contamination levels, are

used to select stations that are in good or poor condition

for development of the BI. Parameters in the BI include

a measure of species diversity and measures of pollution

intolerant organisms. A positive BI indicates good

conditions, while a negative value indicates impacted

benthic community. Severely impacted represents the

10% worst areas as observed by EMAP during 1990-93

(Delaware Estuary Program, 1996).

Fish/Shellfish Advisories

Fish or shellfish consumption advisories are issued by

state government agencies to protect human health by

reducing the health risks associated with eating fish or

shellfish contaminated with chemical pollutants. Advisories are recommendations to limit consumption of

certain fish or shellfish taken from contaminated areas.

These advisories are issued when the levels of chemical

pollutants present in the fish or shellfish exceed an

action level. Although states use different methods for

calculating the action levels, the common threads are

that they are based on the presence of high concentrations of pollutants in the fish or shellfish, and that they

are meant to protect human health. Two basic approaches to deriving action levels are: 1) using the U.S.

Food and Drug Administration (FDA) action levels; and

2) conducting a risk assessment that factors in such

things as typical meal size, frequency of consumption of

fish or shellfish, average body weight of consumer,

pollutant concentration in the fish or shellfish, and risk of

causing cancer. Due to these differences in the calculation of action levels by different states, the fish or

shellfish contaminant concentrations in one states

advisory area may not be the same as another states,

but in both areas the concentrations would be high

enough to cause concern about possible human health

risk. Therefore, fish or shellfish advisories are used in

this report to highlight areas of concern rather than to

compare contaminant levels in fish and shellfish.

50

Technical Appendix
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