United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/620/R-94/005
March 1994
&EPA | Statistical Summary
EMAP-Estuaries
Virginian Province-1991
Environmental Monitoring and
Assessment Program
-------
EPA/620/R-94/005
March 1994
Statistical Summary
EMAP-Estuaries
Virginian Province - 1991
by
Steven C. Schimmel
Brian D. Melzian
U.S. Environmental Protection Agency
Environmental Research Laboratory
Narragansett, Rl 02882
Daniel E. Campbell
University of Rhode Island
Graduate School of Oceanography
Charles J. Strobe!
Sandra J. Benyi
Science Applications International Corporation
Jeffrey S. Rosen
Henry W. Buffum
Computer Sciences Corporation
Virginian Province Manager
Norman I. Rubinstein
Project Officer
Brian Melzian
United States Environmental Protection Agency
Environmental Research Laboratory
27 Tarzwell Drive
Narragansett, Rl 02882
Printed on Recycled Paper
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ABSTRACT
Annual monitoring of indicators of the ecological condition of bays and estuaries within the Virginian
Province (Cape Cod, MA to Cape Henry, VA) was conducted by the U.S. EPA's Environmental Monitoring and
Assessment Program (EMAP) during July, August, and September, 1991. Data were collected at 154 stations
within the Province. Indicators monitored included water quality (temperature, salinity, water clarity, and dissolved
oxygen concentration), sediment contamination, sediment toxicity, benthic community structure, fish community
structure, fish gross external pathology, and fish tissue contamination. Data are used to estimate the current status
of the ecological condition of Virginian Province estuarine resources, and provide a baseline for identifying future
trends. Cumulative distribution functions (CDFs) and bar charts are utilized to graphically display data. Estimates,
with 95% confidence intervals, are provided of the areal extent of degraded resources within the Province for those
indicators where "degradation" can be defined. Data are also presented by estuarine class: Large estuaries, small
estuarine systems, and large tidal rivers. Included, as an appendix, are sub-population estimates for Chesapeake
Bay and Long Island Sound.
KEY WORDS: EMAP; Environmental Monitoring and Assessment Program; Environmental Monitoring;
Virginian Province; Indicators (biology); Estuaries; Estuarine pollution.
Page ii Statistical Summary, EMAP-E Virginian Province - 1991
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DISCLAIMER
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 represents data from a single year of field operations of the Environmental Monitoring and Assessment
Program (EMAP). Because the probability-based scientific design used by the EMAP necessitates multiple years
of sampling, there may be significant levels of uncertainty associated with some of these data. This uncertainty
will decrease as the full power of the approach is realized by the collection of data over several years. Similarly,
temporal changes and trends cannot be reported, as these require multiple years of observation. Please note that
this report contains data from research studies in only one biogeographical region (Virginian Province) collected
in a short index period (July to September) during a single year (1991). Appropriate precautions should be exercised
when using this information for policy, regulatory or legislative purposes.
Statistical Summary, EMAP-E Virginian Province - 1991 Page iii
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PREFACE
Contractor support for the preparation of this document was supplied via contract number 68-C1-0005 to Science
Applications International Corporation and contract number 68-WO-0043 to Computer Sciences Corporation .
The appropriate citation for this report is:
Schimmcl, S.C., B.D. Melzian, D.E. Campbell, C.J. Strobel, SJ. Benyi, J.S. Rosen, and H.W Buffum. 1994. Statistical
Summary: EMAP-Estuaries Virginian Province -1991. U. S. Environmental Protection Agency, Office of
Research and Development, Environmental Research Laboratory, Narragansett, RI. EPA/620/R-94/.005
This report is ERL-N Contribution Number 1455.
Page Iv Statistical Summary, EMAP-E Virginian Province - 1991
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ACKNOWLEDGEMENTS
The work described in this document is the culmination of the efforts and dedication of dozens of individuals.
The authors would like to acknowledge the efforts of Warren Boothman, Sue Cielinski, Don Cobb, James Heltshe,
Melissa Hughes, Andrew Milliken, Elise Petrocelli, Rich Pruell, Dan Reifsteck, John Scott, Kevin Summers, and
Ray Valente for their invaluable assistance in the preparation of this document.
Researchers at EPA (Cincinnati and Narragansett), Cove Corporation, Science Applications International Corporation,
Texas A&M University, and Versar, Inc. contributed significantly to this effort through the analysis of samples.
In addition to those listed above, reviewers of this document included Richard Latimer, Norman Rubinstein,
Darryl Keith, Steven Ferraro, Jan Prager, Kevin Summers, Robert Diaz, and James Kushlan.
Most importantly, we would like to acknowledge the tremendous effort of all those involved in the 1991 field
effort. Despite sea sickness, 16-hour days, inclement weather, and even a hurricane, the six field crews successfully
completed, to the high standards set for the Program, the data collection phase. Without their dedication to the
Program this Statistical Summary would not be possible. The staff of the Field Operations Center in Narragansett,
RI also played a critical role in the success of the Program; managing the field effort, and tracking, checking,
and managing the tremendous volume of data received over a relatively short period of time.
Statistical Summary, EMAP-E Virginian Province - 1991 Page v
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CONTENTS ;
ABSTRACT .. ...... ., ii
KEY WORDS . . .. ., . .......... . . . ., • ii
DISCLAIMER .. . . iii
PREFACE ................... v .......... -.,,..,....>,,.., iv
ACKNOWLEDGEMENTS , ...,. ,,.,,.,,,,,,,,,,. ., ., . v
CONTENTS ................... . - , ...,,..,, ti
FIGURES . v , ., .„............,..,............,,,,.,.. ^ „,.„,,
TABLES ...................,.,,...,...•..,.,,,...,.,.*.,..,.,. , >. ,.,,
EXECUTIVE SUMMARY .......,,..,.>....,._...,,.,,.,. ,', ._,.,,_,.,.,_ 1
1 INTRODUCTION . . . . ..,....,. _, ,,_, ....... ., . 7
1.1 Objectives of 1991 Virginian Province Monitoring Activities . . . . . . . . . . . . . . .... . . . . 7
1.2 Data Limitations . .... .,. .,. . . . ... . . . -., 8
1.3 Purpose and Organization of this Report ,..>..,•. . .... . . .... ,. 8
2 OVERVIEW OF FIELD ACTIVITIES . 10
3 STATISTICAL SUMMARY OF INDICATOR RESULTS . . 16
3.1 Biotic Condition Indicators . . . . 17
3.1.1 Benthic Index 17
3.1.2 Number of Benthic Species 18
3.
3.
3.
3.
3.
.3 Benthic Infaunal Abundance . . . 20
.4 Number of Fish Species 20
.5 Total Finfish Abundance 24
.6 Fish Gross External Pathology . . . 24
.7 Fish Tissue Contaminants 24
3.2 Abiotic Exposure Indicators . . ,. 26
3.2.1 Dissolved Oxygen . . . . ..... 26
3.2.1.1 Bottom Dissolved Oxygen - Instantaneous . . . 26
3.2.1.2 Bottom Dissolved Oxygen - Continuous 26
3.2.1.3 Dissolved Oxygen Stratification 31
3.2.2 Sediment Toxicity 31
3.2.3 Sediment Contaminants 34
3.2.3.1 Polycyclic Aromatic Hydrocarbons 34
3.2.3.2 Polychlorinated Biphenyls 36
3.2.3.3 Chlorinated Pesticides , 38
3.2.3.4 Butyltins 41
Page vi Statistical Summary, EMAP-E Virginian Province - 1991
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CONTENTS (continued)
-ff
3.2.3.5 Total Organic Carbon [ 43
3.2.3.6 Acid Volatile Sulfides 44
3.2.3.7 Metals 46
3.2.4 Marine Debris 48
3.3 Habitat Indicators 49
3.3.1 Water Depth 50
3.3.2 Temperature 50
3.3.3 Salinity 51
3.3.4 PH 51
3.3.5 Stratification 51
3.3.6 Suspended Solids 53
3.3.7 Light Extinction 58
3.3.8 Silt-Clay Content 58
3.4 Integration of Estuarine Conditions 59
4 QUALITY ASSURANCE 61
4.1 Crew Training 61
4.2 Field Data and Sample Collection - Quality Control Checks 62
4.2.1 Water Quality Measurements 62
4.2.2 Benthic Indicators 62
4.2.3 Fish Indicators . . 63
4.2.4 Field Performance Reviews >, 63
4.3 Laboratory Testing and Analysis 64
4.3.1 Sediment Toxicity Testing 64
4.3.2 Grain Size Analysis 64
4.3.3 Benthic Infauna Analysis 64
4.4 Laboratory Certification and Chemical Analysis 65
4.5 Data Management 67
4.6 Reporting 69
5 SUMMARY OF FINDINGS 70
5.1 Virginian Province Fact Summary 70
5.2 Findings of the 1991 Sample Year 70
6 LITERATURE CITED 72
APPENDIX A - SAMPLING DESIGN, ECOLOGICAL INDICATORS, AND METHODS
APPENDIX B - CALCULATION OF THE BENTHIC INDEX
APPENDIX C - SUB-POPULATION ESTIMATES FOR CHESAPEAKE BAY AND LONG ISLAND
SOUND
APPENDIX D - LINEAR REGRESSIONS OF INDIVIDUAL METALS AGAINST ALUMINUM USED IN
THE DETERMINATION OF METALS ENRICHMENT OF SEDIMENTS OF THE
VIRGINIAN PROVINCE
Statistical Summary, EMAP-E Virginian Province - 1991 Page vii
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FIGURES
Figure 1. Percent area of the Virginian Province by estuarine class with a benthic index
value below zero in 1991 2
Figure 2. Cumulative distribution of fish abundance in numbers per standard trawl as a
percent of area in the Virginian Province, 1991 2
Figure 3. The percent of area in the large estuaries, small estuaries, and large tidal rivers
that had a low (0 to 2 mg/L), medium (2.1 to 5 mg/L), or high (>5 mg/L)
oxygen concentration in the bottom waters 3
Figure 4. Percent of area in the Virginian Province in 1991, by estuarine class, with low
amphipod survival (<80% of control) in sediment toxicity tests. . . . 3
Figure 5. Cumulative distribution of combined PAHs in sediments as percent of area in
the Virginian Province, 1991 3
Figure 6. Percent area of the Virginian Province with enriched concentrations of
individual metals in sediments in 1991 4
Figure 7. The percent of area of the Virginian Province by estuarine class where
anthropogenic debris was collected in fish trawls, 1991 4
Figure 8. Cumulative distribution of water depth as a percent of area in the Virginian
Province, 1991 5
Figure 9. The percent of area of estuarine classes classified as oligohaline (<5 ppt),
mesohaline (5 to 18 ppt), and polyhaline (>18 ppt) 5
Figure 10. The percent of the area by class that had a low (<1 AO,), medium (1 to 2 ACT,),
or high (>2 ACT,) degree of stratification 5
Figure 11. The percent of area by estuarine class where water clarity was poor, moderate,
or good 6
Figure 12. The percent of area in the large estuaries, small estuaries, and large tidal rivers
that had a low (<20), medium (20 to 80), or high (>80) percent silt-clay in the
sediments 6
Figure 2-1. Areas of responsibility of the EMAP-VP sampling teams 11
Figure 2-2. Team 1 Base Sampling Stations 12
Figure 2-3. Team 2 Base Sampling Stations 13
Figure 2-4. Team 3 Base Sampling Stations 14
Page viii
Statistical Summary, EMAP-E Virginian Province - 1991
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FIGURES (continued)
Figure 3-1. Example cumulative distribution of instantaneous bottom dissolved oxygen
concentrations as a percent of area in the Virginian Province 16
Figure 3-2. Cumulative distribution of benthic index values as a percent of area in the
Virginian Province, 1991 17
Figure 3-3. Percent area of the Virginian Province by estuarine class with a benthic index
value below zero in 1991 18
Figure 3-4. Cumulative distribution of the mean number of benthic species per grab as a
percent of area in the Virginian Province, 1991 18
Figure 3-5. Cumulative distribution functions of the number of benthic species by estuarine
class, (a) Large estuaries, (b) Small estuaries, (c) Large tidal rivers 1,9
Figure 3-6. Cumulative distribution of the number of benthic organisms per m2 as a percent
of area in the Virginian Province, 1991 20
Figure 3-7. Cumulative distribution functions of the number of benthic organisms per m2
by class, (a) Large estuaries, (b) Small estuaries, (c) Large tidal rivers 21
Figure 3-8. Cumulative distribution of the number of fish species per standard trawl as a
percent of area in the Virginian Province, 1991 22
Figure 3-9. Cumulative distribution functions of the number of fish species per trawl by
estuarine class, (a) Large estuaries, (b) Small estuaries, (c) Large tidal rivers 23
Figure 3-10. Cumulative distribution of fish abundance in numbers per standard trawl as a
percent of area in the Virginian Province, 1991 24
Figure 3-11. Cumulative distribution functions of fish abundance in numbers per standard
trawl by estuarine class, (a) Large estuaries, (b) Small estuaries, (c) Large
tidal rivers 25
Figure 3-12. Cumulative distribution of instantaneous bottom dissolved oxygen
concentration as a percent of area in the Virginian Province, 1991 29
Figure 3-13. The percent of area by class that had a low (< 2 mg/L), medium (2 to 5 mg/L),
or high (>5 mg/L) oxygen concentration in the bottom waters. 29
Figure 3-14. Cumulative distribution functions of bottom oxygen concentration by estuarine
class, (a) Large estuaries, (b) Small estuaries, (c) Large tidal rivers 30
Figure 3-15. Cumulative distribution of the minimum bottom oxygen concentration
measured over a 24-hour period as a percent of area in the Virginian Province,
1991. (Dashed lines are the 95% confidence intervals). 31
Statistical Summary, EMAP-E Virginian Province - 1991 Page ix
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FIGURES (continued)
Figure 3-16. Cumulative distribution of the dissolved oxygen concentration difference
between surface and bottom waters as a percent of area in the Virginian
Province, 1991 32
Figure 3-17. The percent of area in the large estuaries, small estuaries, and large tidal rivers
that had a low (<1 mg/L), medium (1 to 5 mg/L), or high (>5 mg/L) difference
in dissolved oxygen concentration between the surface and bottom waters 32
Figure 3-18. Cumulative distribution of mean survival of amphipods in 10-day laboratory
toxicity tests (expressed as percent of control survival) 33
Figure 3-19. Percent of area in the Virginian Province in 1991, by estuarine class, with low
amphipod survival (<80% of control) in sediment toxicity tests 33
Figure 3-20. Cumulative distribution of combined PAHs in sediments as percent of area in
the Virginian Province, 1991; a) linear scale, b) log scale ., 37
Figure 3-21. Cumulative distribution of the relative percentage of high molecular weight
PAHs in sediments as percent of area in the Virginian Province, 1991 38
Figure 3-22. Cumulative distribution of combined PCBs in sediments as percent of area in
the Virginian Province, 1991; a) linear scale, b) log scale 40
Figure 3-23. Cumulative distribution of p, p' -DDE in sediments as percent of area in the,,
Virginian Province, 1991 42
Figure 3-24. Cumulative distribution of alpha-chlordane in sediments as percent of area in
the Virginian Province, 1991 42
Figure 3-25. Cumulative distribution of tributyltin in sediments as percent of area in the
Virginian Province, 1991 43
Figure 3-26. The cumulative distribution of the percent total organic carbon in sediments as
a percent of area in the Virginian Province, 1991 44
Figure 3-27. Cumulative distribution functions of the percent total organic carbon in
sediments by estuarine class, (a) Large estuaries, (b) Small estuaries, (c)
Large tidal rivers . 45
Figure 3-28. The cumulative distribution of the acid volatile sulfide concentration in
sediments as a percent of area in the Virginian Province, 1991 46
Figure 3-29. Cumulative distribution functions of the acid volatile sulfide concentration in
sediments by estuarine class, (a) Large estuaries, (b) Small estuaries, (c)
Large tidal rivers 47
Page x Statistical Summary, EMAP-E Virginian Province - 1991
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FIGURES (continued)
Figure 3-30. ^Example linear regression (with upper 95% confidence intervals) of chromium
against aluminum ~. 49
Figure 3-31. Percent area of the Virginian Province with enriched concentrations of
individual metals in sediments in 1991 49
Figure 3-32. The percent of area of the Virginian Province by estuarine class where
anthropogenic debris was collected in fish trawls, 1991 50
Figure 3-33. Cumulative distribution of water depth as a percent of area in the Virginian
- " Province, 1991 50
Figure 3-34. Cumulative distribution of bottom temperature as a percent of area in the
Virginian Province, 1991 51
Figure 3-35. Cumulative distribution functions of bottom temperature by estuarine class, (a)
Large estuaries, (b) Small estuaries, (c) Large tidal rivers 52
Figure 3-36. The cumulative distribution of bottom salinity as a percent of area in the
Virginian Province, 1991 53
Figure 3-37. Cumulative distribution functions of bottom salinity by estuarine class, (a)
Large estuaries, (b) Small estuaries, (c) Large tidal rivers 54
Figure 3-38. The percent of area by estuarine class classified as oligohaline (<5 ppt),
mesohaline (5 to 18 ppt), and polyhaline (>18 ppt) 55
Figure 3-39. Cumulative distribution function of the stratified area in the Virginian Province
in 1991 based on the sigma-t (at) density difference between surface and
bottom waters 55
Figure 3-40. The percent of the area by estuarine class that had a low (<1), medium (1 to 2),
or high (>2) degree of stratification ( A CT,) 56
Figure 3-41. The cumulative distribution of total suspended solids concentration as a percent
of area in the Virginian Province, 1991 56
Figure 3-42. Cumulative distribution functions of total suspended solids concentration by
estuarine class, (a) Large estuaries, (b) Small estuaries, (c) Large tidal rivers 57
Figure 3-43. The cumulative distribution of light extinction coefficient as a percent of area
in the Virginian Province in 1991 58
Figure 3-44. The percent of area by estuarine class where water clarity was poor, moderate,
or good 59
Statistical Summary, EMAP-E Virginian Province - 1991 Page xi
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FIGURES (continued)
Figure 3-45. The cumulative distribution of the percentage of silt-clay in the sediments as a
percent of area in the Virginian Province, 1991 59
Figure 3-46. The percent of area by estuarine class with a low (<20), medium (20 to 80), or
high (>80) percent silt-clay in the sediments 60
Figure 3-47. Integration of estuarine conditions based on presence of bottom trash, water
clarity, and the benthic index 60
Page xii Statistical Summary, EMAP-E Virginian Province * 1991
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TABLES
Table 2-1,
Table 3-1.
Table 3-2.
Table 3-3.
Table 3-4.
Table 3-5.
Table 3-6.
Table 3-7.
Table 3-8.
Table 4-1.
Table 4-2.
Table 4-3.
Summary of collection and processing status of samples collected.
1991 EMAP Virginian Province target fish species summary: BSS stations
only
Summary of fish contaminant data collected in 1991
Draft Sediment Quality Criteria values for acenaphthene, phenanthrene,
fluoranthene, and dieldrin
Range and median PAH concentrations in sediments of the Virginian Province
Range and median PCB concentrations in sediments of the Virginian Province
Range and median chlorinated pesticide concentrations in sediments of the
Virginian Province
Range and median butyltin concentrations in sediments of the Virginian
Province.
Range and median metal concentrations in sediments of the Virginian Province
Results of recounts performed by the laboratory processing benthic infauna
samples
»
Results of certification analyses for sediment contamination performed by
EMSL-Cinn
Results of certification analyses for fish tissue contamination performed by
Texas A&M University. . . .'....
Table 5-1. Summary of the aerial extent of indicators relative to critical values.
15
22
27
34
35
39
41
43
48
65
66
68
71
Statistical Summary, EMAP-E Virginian Province - 1991
Page xiii
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EXECUTIVE SUMMARY
The Environmental Monitoring and Assessment
Program (EMAP) is a nationwide program initiated by
EPA's Office of Research and Development (ORD).
EMAP was developed in response to the demand for
information about the degree to which existing pollution
control programs and policies protect the nation's
ecological resources.
EMAP-Estuaries (EMAP-E) represents one portion of
EMAP's efforts in near-coastal environments. These
efforts are designed to provide a quantitative assessment
of the regional extent of coastal environmental problems
by measuring status and change in selected indicators of
ecological condition. Specific issues investigated include:
• hypoxia,
• sediment contamination,
• coastal eutrophication, and
• habitat loss.
In 1990, EMAP-E initiated a demonstration project
in the estuaries of the Virginian Province. The 1991 field
season represents the second year of sampling in the
Province, which includes the coastal region of the
Northeast United States from Cape Cod south to the mouth
of Chesapeake Bay. It is composed of 23,574 km2 of
estuarine resources including 11,469 km2 in Chesapeake
Bay and 3,344 km2 in Long Island Sound.
Estuarine resources in the Virginian Province were
stratified into classes by physical dimension for the
purposes of sampling and analysis. Large estuaries in the
Virginian Province were defined as those estuaries greater
than 260 km2 in surface area and with aspect ratios (i.e.,
length/average width) of less than 18. The areal extent
of large estuaries in the Province was 16,097 km2. Large
tidal rivers were defined as that portion of the river that
is tidally influenced (i.e., detectable tide > 2.5 cm), greater
than 260 km2, and with an aspect ratio of greater than 18.
Approximately 2,602 km2 were classified as tidal rivers.
The third class was the small estuaries and small tidal rivers
which were those systems whose surface areas fell between
2.6 km2 and 260 km2. This class represented 4,875 km2
of the Virginian Province.
Three field crews sampled 154 of the scheduled 155
sites in the Virginian Province during the seven-week sampling
period beginning on July 22, 1991. Of these, 102 were
"Base Sampling Sites" (BSS) which were the probability-based
sites selected according to the EMAP-E design for assessing
the condition of the estuarine resources of the Province
(see Appendix A). Only data collected at these sites were
used in the generation of this report.
Field crews collected data and samples for three categories
of "ecological indicators": Biotic condition, abiotic condition,
and habitat which are described in Appendix A.
The 1991 data reported in this document represent only
one year of sampling of a four-year cycle; i.e., the total
number of samples needed by EMAP to characterize the
Province are sampled over a four-year period (Holland,
1990). Therefore, the reader must use these data carefully,
and be aware that the proportion of degraded area calculated
for 1991 may differ somewhat from the regional assessment
to be generated following the completion of the four-year
cycle.
All EMAP-Virginian Province (EMAP-VP) data used
in the generation of this report were subjected to rigorous
quality assurance measures as described in the 1991 Quality
Assurance Project Plan (Valente and Schoenherr, 1991).
Biotic Condition Indicators
Biotic condition indicators are characteristics of the
environment that provide quantitative evidence of the status
Statistical Summary, EMAP-E Virginian Province - 1991
Page 1
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of ecological resources and biological integrity of a sample
site from which they are collected (Messer, 1990).
Ecosystems with a high degree of biotic integrity (i.e.,
healthy ecosystems) are composed of balanced populations
of indigenous benthic and water column organisms with
Species compositions, diversity, and functional organization
comparable to undisturbed habitats (Karr and Dudley,
1981; Karr^fl/., 1986).
A benthic index which uses measures of individual
health, functionality, and community condition to evaluate
the condition of the benthic assemblage was utilized in
the assessment of biological resources of the Virginian
Province. The index under development was determined
from the combined 1990/1991 data and is assumed to
represent a combination of ecological measurements that
best discriminates between good and poor ecological
conditions. The reader should be cautioned that this index
has not yet been validated with an independent dataset,
and therefore, should be used with caution.
A benthic index critical value of zero was determined
from the combined 1990/1991 Virginian Province dataset.
Fourteen (± 6) percent of the bottom area of the Virginian
Province sampled in 1991 had an index value of < 0,
indicating likely impacts on the benthic community (Figure
1). The lowest incidence was found in the large estuaries
(6 ± 7%), and the highest in small estuaries (32 ± 17%).
"Standard" fish trawls (trawling at a specified speed
for a specified time) were performed at each station to
collect information on the distribution and abundance of
fish. Because many factors influence fish abundance, poor
so -
40 -
30 -
20 -
10 -
AH
Large
Small
Tidal
Figure 1. Percent area of the Virginian Province by estuarine
class with a benthic Index value below 0 in 1991. (Error bars
represent 95% confidence intervals).
catch may not be an indication of degraded conditions,
but simply the natural habitat. Catches of <10 fish/trawl
(catch per unit effort) occurred at stations representing
approximately 31 ± 10% of the Province, and "high" catches
(>100 fish/trawl) were experience in approximately 18 ±
9% (Figure 2). Tidal rivers produced the greatest percent
area with "high" catches.
Percent of Area
120 i
100
80
60
40
20
0,
C
.Jr^
ip
100 200 300 400 500 600 700
Number of Fish per Trawl
Figure 2. Cumulative distribution of fish abundance in
numbers per standard trawl as a percent of area in the
Virginian Province, 1991. (Dashed lines are the 95%
confidence intervals).
The incidence of the gross external pathologies; growths,
lumps, ulcers, and fin erosion, among "target" species in
the Virginian Province in 1991 was 0.6%. Of the 2,513
fish examined, 16 were identified as having one or more
of these pathologies. These individuals were collected at
six of the 101 base stations sampled during the index period
(one additional station could not be sampled). It should
be noted that fewer than half of these pathologies were
verified by an expert pathologist.
Eighty-four composites of up to five individuals of
target species were analyzed for contaminants in muscle.
No sample exceeded FDA action limits (or, where FDA
action limits were not available, international limits) for
any of the organic analytes for which criteria were available
(see Table 3-2). Several metals (arsenic, chromium and
selenium) exceeded criteria values, with the highest incidence
of exceedences being measured for arsenic. Fourteen of
the 82 composite samples analyzed for metals (two samples
were lost) exceeded the mean of international criteria values
for As (2 ug/g wet weight).
Page 2
Statistical Summary, EMAP-E Virginian Province - 1991
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Abiotic Condition Indicators
Abiotic condition indicators historically have been the
mainstay of environmental monitoring programs, because
these indicators quantify the levels of stresses to which
organisms are exposed.
One potential stress to aquatic organisms is a low
concentration of dissolved oxygen (DO). Two and five
mg/L are values employed by EMAP to define severe and
moderate hypoxia, respectively. Approximately 18 ± 8%
of the sampled area of the Province lies in waters with
bottom DO concentrations less than or equal to 5 mg/L
(Figure 3). "Bottom" is defined as one meter above the
sediment-water interface. Approximately 5 ± 5% of the
sampled area exhibited bottom DO conditions <2 mg/L.
Dissolved oxygen conditions < 2 mg/1 were evident in 4
± 6,1 ± 2, and 15 ± 28% of the area of the large estuaries,
small estuaries, and large tidal rivers sampled within the
Province, respectively.
1201
100
i eoj
CD
Q.
60-
40-
20-
0
•
B2to5
0 >5
All
Large
Small
Tidal
Figure 3. The percent of area by class that had a low (< 2
mg/L), medium (2 to 5 mg/L), or high (>5 mg/L) oxygen
concentration in the bottom waters. (Error bars represent
95% confidence intervals).
In addition to measuring individual stressors (i.e.,
individual chemical analytes) sediment toxicity tests were
performed on sediments collected at each site to determine
if they were toxic to the tube-dwelling amphipod,
Ampelisca abdita. Sediments were classified as toxic if
amphipod survival in the test sediment was less than 80%
of that in the control sediment. Approximately 21 ± 10%
of the sampled area of the Virginian Province contained
sediments which were toxic to the amphipod during 10-day
exposures (Figure 4).
40 -,
30 -
I 20 -
10 -
0 -L
Large
Small
Tidal
Figure 4. Percent of area in the Virginian Province in 1991,
by estuarine class, with low amphipod survival (<80% of
control) in sediment toxicity tests. (Error bars represent 95%
confidence intervals).
Sediments collected at each station were analyzed for
both organic contaminants and metals. Because of the complex
nature of sediment geochemistry, the ecological impact
of elevated contaminant levels is not well understood.
Therefore, no attempt is made to estimate the overall aerial
extent of sediment contamination in the Virginian Province.
Figure 5 shows the distribution of the sum of measured
poly cyclic aromatic hydrocarbons (PAHs) in the Virginian
Province. The complete list of analytes included in this
summation can be found in Section 3. Approximately 94
± 6% of the Province has concentrations of PAHs below
4,000 ng/g dry weight, with a maximum measured concentration
at any station of 80,100 ng/g.
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\
) 1 2345678
Combined PAHs (ng/g dry wt x 10,000)
Figure 5. Cumulative distribution of combined PAHs in
sediments as percent of area in the Virginian Province, 1991.
(Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 3
-------
Draft EPA Sediment Quality Criteria (SQC) are
currently available for the PAHs acenaphthene,
phenanthrene, and fluoranthene; and the pesticide dieldrin.
Exceedences of the PAH criteria were measured at only
three stations within the Province (2 ± 5% of the area).
The station representing the largest area was located in
a shipping channel at the mouth of Chesapeake Bay in a
sandy environment. Sediments from this station did not
show any toxicity, and the benthic community was
indicative of a healthy environment. All evidence suggests
that this exceedence was an artifact, possibly due to a
"chip" of material dislodged from the smokestack of a
passing ship. Eliminating this station results in 0 ± 0%,
0.3 ± 5% (one station) and 0.4 ± 4% (two stations) of the
sampled area of the Province exceeding SQC for
acenaphthene, phenanthrene and fluoranthene, respectively.
No station sampled in 1991 exceeded the SQC for dieldrin.
The extent to which polluting activities have affected
concentrations of metals in sediments is complicated by
the natural variation of metals in sediments. Crustal
aluminum concentrations are generally many orders of
magnitude higher than anthropogenic inputs; therefore,
aluminum can be used to "normalize" for differing crustal
abundances of trace metals (see Appendix A for a
description of the normalization process). Figure 6
presents the results of this normalization. Approximately
41 ± 10% of the area of the Province showed enrichment
of sediments with at least one metal. Thirty five (± 14),
53 ± 22, and 51 ±23 percent of the large estuary, small
estuary, and large tidal river class areas sampled contained
sediments with metals concentrations exceeding predicted
background levels. This only shows the percent of the
Province with elevated concentrations of metals, and does
35
30
I 2S
•8 20
§ IS
10
S
0
AS As Cd Cr Cu Fe Hg Mn Ni Pb Sb Sa Sn Zn
Figure 6. Percent area of the Virginian Province with
enriched concentrations of individual metals in sediments in
1991. (Error bars represent 95% confidence intervals).
not indicate the magnitude of enrichment, i.e., this does
not imply concentrations are elevated to the point where
biological effects might be expected.
Presence of marine debris in fish trawls was .documented
by field crews as being encountered at stations representing
18 ± 8% of the Virginian Province area (Figure 7). The
small estuary class had the largest percent area (35 ± 17%)
where trash was found.
80-,
60-
0 40 -
•E
CD
Q_
20-
Al!
Large
Small
Tidal
Figure 7. The percent of area of the Virginian Province by
estuarine class where anthropogenic debris was collected in
fish trawls, 1991.
Habitat Characterization
Habitat indicators describe the natural physical and
chemical conditions of the sites sampled. These parameters
are important modifying factors controlling both abiotic
and biotic condition indicators.
Figure 8 shows the distribution of water depth in the
Virginian Province. The area shallower than 2 m is
underestimated because this was the minimum depth sampled.
Based on the sampling design where a single station
represents a statistical area (e.g., 70 km2 for large estuary
sites), 12% of the area of large estuaries of the Province
to be sampled in 1991 was unsampleable due to inadequate
water depth. Small systems were considered unsampleable
if the water depth did not exceed 2 m anywhere in the system.
Such systems account for approximately 1.5% of the area
of small systems in the Virginian Province. No large tidal
river stations were unsampleable due to water depth in
Page 4
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Depth (m)
Figure 8. Cumulative distribution of water depth as a
percent of area in the Virginian Province, 1991. (Dashed lines
are the 95% confidence intervals).
1991. Overall, 9% of the area of the Province to be
sampled in 1991 was deemed unsampleable due to water
depth.
Bottom water temperature in the Virginian Province
ranged from 16.2°C to 30.0°C during the summer sampling
season.
Figure 9 illustrates the distribution of oligohaline (<5
%o salinity), mesohaline (5-18%o), and polyhaline (>18%o)
water in the Virginian Province and by estuary class.
Vertical density differences (a function of both salinity
and temperature) in the waters of the Virginian Province
can be large enough to result in a reduction in mixing
between surface and bottom waters, potentially allowing
the bottom waters to become hypoxic. Degree of
100
80
< 60
20
1 Oligohaline
Mesohaline
Polyhaline
All
Large
Small
Tidal
Figure 9. The percent of area by estuarine class classified as
oligohaline (<5 ppt), mesohaline (5 to 18 ppt), and polyhaline
(>18 ppt). (Error bars represent 95% confidence intervals).
stratification in the Virginian Province was measured as
the delta (A) a,, which is the at (sigma-t density) difference
between surface and bottom waters. Approximately 76
± 10% of the Province area had a Aat of <1 unit; thus the
majority of the water in the Virginian Province was well-mixed
(Figure 10). Only 7 ± 7% of the Province area was strongly
stratified (Arjt >2).
120i
Large
Small
Tidal
Figure 10. The percent of the area by estuarine class that
had a low (<1), medium (1 to 2), or high (>2) degree of
stratification (A a,). (Error bars represent 95% confidence
intervals).
Water clarity was determined from light extinction
coefficients, which describe the attenuation of light as it
passes vertically through the water column. We are defining
low water quality as water in which a diver would not be
able to see his/her hand when held at arms length in front.
Moderate water clarity, in terms of human vision, is defined
as water in which a wader would not be able to see his/her
feet in waist deep water.
Water clarity was good in 80 ± 7% of the area of the
Virginian Province (Figure 11). Water of low clarity was
found in 8 ± 6% of the Province and an additional 12 ±
7% had water of moderate clarity.
The silt-clay (mud) content of sediments (the fraction
<63u, particle diameter) is an important factor determining
the composition of the biological community at a site; and
is therefore important in the assessment of the benthic
community. The distribution of mud (>80% silt-clay) vs
sand (<20% silt-clay) is illustrated in Figure 12.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 5
-------
100
s80
1 •
"B 60-
1 '
<£ 40-
.
20-
*
I
F?
i
:;.;
if
r
1
if-
J
1
A
JV;
^1
" i
t':.
•jij,"
' ;
|
All Large
!--
s*
y
n
n.
%&.
i
%%$,
m
P
i
!
i
s
*
II
H Low
S Moderate
0 Good
j
\
Small Tidal
Figure 11. The percent of area by estuarine class where
water clarity was poor, moderate, or good. (Error bars
represent 95% confidence intervals).
B 20 to 80
Large
Small
Tidal
Figure 12. The percent of area by estuarine class with a low
(<20), medium (20 to 80), or high (>80) percent silt-clay in the
sediments. (Error bars represent 95% confidence intervals).
Page 6
Statistical Summary, EMAP-E Virginian Province - 1991
-------
SECTION 1
INTRODUCTION
The Environmental Monitoring and Assessment
Program (EMAP) is a nationwide program initiated by
EPA's Office of Research and Development (ORD).
EMAP was developed in response to the need to imple-
ment a monitoring program that contributes to com-
parative ecological risk assessment and decisions related
to environmental protection and management. EMAP
is an integrated federal programs ORD is coordinating
the planning and implementation of EMAP with other
federal agencies including the Agricultural Research
Service (ARS), the Bureau of Land Management (BLM),
the U.S. Fish and Wildlife Service (FWS), the Forest
Service (FS), the U.S. Geological Survey (USGS), and
the National Oceanic and Atmospheric Administration
(NOAA). These other agencies and offices participate
in the collection and analysis of EMAP data and will
use it to guide their policy decisions as appropriate.
EMAP-Estuaries (EMAP-E) represents one portion
of EMAP's efforts in near-coastal environments. These
efforts are designed to provide a quantitative assessment
of the regional extent of coastal environmental problems
by measuring status and change in selected ecological
condition indicators to address specific issues including:
• hypqxia,
• sediment contamination,
• coastal eutrophication, and
• habitat loss.
In 1990, EMAP-E initiated a demonstration project
in the estuaries of the Virginian Province (i.e., estuaries,
bays and sounds between Cape Cod, MA and Cape
Henry, VA: Weisbergef. al., 1993). One of the objec-
tives of the Demonstration Project was to test the EMAP
design, logistical approach and various ecological
condition indicators. Based on the experience of the
1990 Demonstration Project, EMAP-E modified minor
aspects of the logistical plan for 1991.
1.1 Objectives of 1991 Virginian Province
Monitoring Activities
The specifics of the planning activities of the 1991
Virginian Province sampling effort are documented in
the 1991 Virginian Province Logistics Plan (Strobel and
Schimmel, 1991a), the 1991 Field Readiness Report (Strobel,
1991), and the 1991 Virginian Province Field Operations
and Safety Manual (Strobel and Schimmel, 1991b). Sampling
was conducted from 22 July through 8 September 1991,
spanning 154 sites (stations). Approximately 30 field
personnel and three extramural contracts were utilized.
The objectives of the 1991 Virginian Province monitoring
were to:
• implement, for the first time, the routine monitoring
of the Province using selected indicators from the
1990 Demonstration Project;
• incorporate EMAP-E design changes based on the
1990 experience;
• obtain data on Virginian Province-specific variability
in ecological parameters;
• develop and refine assessment procedures for the
ecological status of estuaries and apply these procedures
to establish the baseline conditions in the Virginian
Province; and
Statistical Summary, EMAP-E Virginian Province - 1991
Page 7
-------
• identify and resolVe remaining logistical problems
associated with sampling estuarine resources in the
Province within a 4-6 week sampling period.
As part of establishing baseline conditions in the
Virginian Province, several assessment questions relating
to ecological conditions were addressed. Among these
questions are:
• What proportion of the bottom waters of the
estuaries of the Virginian Province experience
hypoxia (/.*., dissolved oxygen concentrations <
2mg/L)?
• What proportion of the estuarine sediments of the
Virginian Province have a benthic community
structure indicative of polluted environments?
• What is the incidence of gross external pathologies
among target fish species in the Virginian
Province?
• What proportion of estuarine sediments in the
Virginian Province contain anthropogenic marine
debris?
• What proportion of estuarine sediments in the
Virginian Province contain elevated levels of
anthropogenic chemical contaminants?
1.2 Data Limitations
The 1991 data represent only one year of sampling
of a four year cycle; i.e., the total number of samples
needed to characterize the Province with the degree of
confidence required by EMAP are sampled over a four-
year period (Holland, 1990). Therefore, the reader must
use these data carefully, and be aware that single-year
results may differ from those reported following the
completion of the four-year cycle (i.e., 1990 - 1993).
EMAP is designed to provide data on a "provincial"
scale. This design creates an additional limitation for
those interested in smaller scale studies. For example,
each of the 144 small systems (i.e., Raritan Bay or the
Elizabeth River) is represented by a single station, the
location of which is randomly selected. The assumption
is made that this station is representative of an area of
the Province equal to the area of that system. In total,
these stations are expected to provide an accurate portrayal
of conditions in small systems across the Province; however,
the design, at its current scale, does not allow for the
study of conditions in individual small systems. The
reader should consult Appendix A and the Near Coastal
Program Plan (Holland, 1990) for additional information
on the statistical design.
Lastly, a benthic index is currently under development
to aid in the interpretation of benthic community data
(described in Appendix B). This index has been developed
using combined 1990/1991 data and cross-validated using
a test dataset. Additional validation^using independent
data is necessary, and will be conducted using 1992 and
1993 data as they become available. Therefore, the benthic
index that appears in the four-year assessment report
may differ from the one presented here, however, the
estimated percent area degraded is not expected to change
significantly.
1.3 Purpose and Organization of This Report
The purpose of this report is to provide estimates of
the ecological condition (and environmental exposures)
of the estuarine resources of the Virginian Province for
1991.
The Statistical Summaries that will be produced by
EMAP-E are meant to provide large quantities of information
without extensive interpretation of these data. Interpretive
reports are anticipated upon completion of each four-year
cycle or in specialized documents such as the Virginian
Province Demonstration Project Report (Weisberg et
al., 1993)
This report is organized into sections addressing the
objectives and results of the 1991 Virginian Province
survey. Section 1 describes the objectives of the Program
and limitations on the use of the data presented in this
report.
Section 2 briefly summarizes logistical results of field
sampling activities including station locations, percent
of samples successfully collected, etc.
Section 3 is the statistical summary of the data collected
during the 1991 survey.
Page 8
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Section 4 summarizes the quality assurance/quality
control results of the 1991 survey.
Section 5 summarizes the findings of the 1991 survey
in the Virginian Province.
Section 6 lists the references cited in this report.
Appendix A provides an overview of the sampling
design used for base-level monitoring as well as details
concerning special studies conducted to assess spatial
variability. This appendix also describes the selected
indicators used in the survey.
Appendix B presents the statistical methods used in
the calculation of the benthic index presented in Section
3.
Appendix C provides sub-population estimates for
Chesapeake Bay and Long Island Sound.
Appendix D presents the plots of the regressions of
individual metals concentrations in sediments against
aluminum concentrations used in the determination of
areal extent of metals enrichment.
Statistical Summary, EMAP-E Virginian Province - 1991 Page 9
-------
SECTION 2
OVERVIEW OF FIELD ACTIVITIES
The Virginian Province includes the coastal region
of the northeast United States from Cape Cod south to
the mouth of Chesapeake Bay. It is composed of
23,574 km2 of estuarine resources including 11,469 km2
in Chesapeake Bay and 3,344 km2 in Long Island
Sound.
The 1991 Virginian Province survey was conducted
during late July through early September, 1991. A
probability-based sampling design was used to sample
major estuarine resources proportionately (Overton et
at., 1991; Stevens et al., 1991). This design makes it
possible to estimate the proportion or amount of area
in the Virginian Province having defined environmental
conditions. A more detailed discussion of the sampling
design can be found in Appendix A.
One hundred and fifty four (154) of the scheduled
155 sites in the Virginian Province between Nantucket
Sound (MA) and Cape Henry (VA) were sampled during
the seven-week sampling period. Sample collection in
the Virginian Province focused on ecological indicators
(see Appendix A) during the index sampling period
(July 1 - September 30), when responses of estuarine
resources to anthropogenic and natural stresses are
anticipated to be most severe. The basic sampling
design provides a probability-based estimate of estuarine
status in the Virginian Province. Additional sites were
also sampled to collect information for specific
hypothesis testing and other specific study objectives
(Schimmel, 1990). This design resulted in five types
of sampling sites for the Virginian Province survey,
which are described in Appendix A.
Base Sampling Sites (BSS) are the probability-based
sites which form the core of the EMAP-E monitoring
design for all provinces, including the Virginian
Province. Data collected from these sites are the basis
of this statistical summary. There were 102 BSS to be
sampled during the 1991 index period, representing
approximately 1A of the total number of base sites that
will be sampled over the four-year cycle. Fifty three
special study sites were also scheduled for sampling.
The 155 stations were divided among three sampling
teams, each covering a specific area of responsibility
(Figure 2-1). Each team was comprised of two, four-
person alternating crews which sampled for six consecu-
tive days. During the six-day period, the crew was
assigned responsibility for sampling a cluster of stations.
The crew shift in which each cluster was to be sampled
was randomized to assure stations were not sampled
across the Province in a north-south series. Each BSS
station was normally visited twice during the 6-day period
to accommodate the deployment and retrieval of
continuous water quality monitoring instruments. Figures
2-2, 2-3, and 2-4 present maps of all the base sampling
sites (BSS) scheduled for sampling in the 1991 Virginian
Province survey.
The 1991 Virginian Province Survey was successful
in its attempt to collect large amounts of information
and samples over a relatively short time period. The
overall effectiveness of the 1991 sampling plan is
reflected in the high percentage of stations for which
usable data were obtained for the variety of parameters
measured (Table 2-1). While all but one station were
sampled as planned, not every site was sampled for every
parameter, and not every sample was successfully
processed. Overall, 9% of the area of the Province
originally scheduled for sampling in 1991 could not be
sampled due to inadequate water depth, or, in the case
of the one station mentioned above, logistical difficulties.
Page 10
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Narragansett,
SAMPLING TE
EdistonfNJ*
SAMPLING TEAM 2
SAMPLING TEAM 3
Figure 2-1. Areas of Responsibility of the EMAP-VP Sampling Teams.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 11
-------
5
CO
c
o
CO
en
c
To.
Page 12
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Figure 2-3. Team 2 Base Sampling Stations.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 13
-------
Figure 2-4. Team 3 Base Sampling Stations.
Page 14
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Table 2-1. Summary of collection and processing status of samples collected.
# Stations
Expected to
Sample Type be Sampled3
Water Quality (DO, Temp., Salinity)
BSS Only
All Station Classes
Light Attenuation Coefficient (CTD cast)
BSS Only
All Station Classes
Suspended Solids
BSS Only
All Station Classes
Hydrolab Deployment
BSS Only
All Station Classes
Sediment Chemistry
BSS Only
AM Station Classes
Sediment Toxicity
BSS Only
All Station Classes
Sediment Grain Size
BSS Only
All Station Classes
Benthic Infauna
BSS Only
All Station Classes
Fish Community Data (successful trawl)
BSS Only
All Station Classes
Anthropogenic Marine Debris
BSS Only
All Station Classes
102
155
102
155
102
155
102
114
102
1 55 r
102
155
102
155
102
155
102
114
102
114
# Stations Sampled
(% of Expected
Stations)
101
146
96
144
101
153
93
105
100
152
100
152
100
152
100
152
98
111
98
111
(99.0%)
(94.2%)
(94.1%)
(92.9%)
(99.0%)
(98.7%)
(91 .2%)
(92.1%)
(98.0%)
(98.1%)
(98.0%)
(98.1%)
(98.0%)
(98.1%)
(98.0%)
(98.1%)
(96.1%)
(97.4%)
(96.1%)
(97.4%)
Percent Stations -
With Data Passing
Final QCb
99.0%
94.2%
94.1%
92.9%
99.0%
98.1%
91 .2%
85.6%
97.1%
98.1%
86.3%°
87.8%°
95.1%
91.0%
98.0%
98.1%
96.1%
97.4%
96.1%
97.4%
Number of stations expected to be sampled excludes all stations determined to be too shallow to sample prior to the
start of field operations. Activities differed at different station classes resulting in the inconsistency in Expected
Station Numbers for "All Station Classes" between indicators. For example, trawling and Hydrolab deployments were
not conducted at Index Stations, resulting in a reduced number of stations expected to be sampled. Station classes
are described in Appendix A.
This value takes into account samples not collected, damaged or lost during shipping or processing, or failing to pass
final QC. The value for "BSS Only" represents the data utilized in the assessment of conditions within the Province.
Low percentage was due to poor survival of control organisms in both original and repeated tests. This is below the
completeness goal of 90%; however, this target is expected to be met over the four-year period.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 15
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SECTION 3
STATISTICAL SUMMARY OF INDICATOR RESULTS
The EMAP indicator strategy includes four types
of ecological indicators: Biotic condition, Abiotic
condition, Habitat, and Stressor. In this section, the
statistical results of the 1991 Virginian Province Survey
are described for each indicator with discussions catego-
rized by major indicator type. Stressor data are not
collected as part of the field effort; therefore, they are
not discussed in this report. The following discussion
is organized by indicator type into Biotic Condition,
Abiotic Condition, and Habitat sections. The indicators
will be briefly described, and in most cases the Cumu-
lative Distribution Function (CDF) will be shown to
delineate the frequency of occurrence of observations
within the Province. Bar graphs and other figures are
also presented, ^here appropriate, to delineate the
proportions of the Province or class resources degraded,
or falling above or below values of interest.
CDFs display the full distribution of the values ob-
served for an indicator plotted against the cumulative
percentage of area in the class or Province. They
provide information on both central tendency (e.g.,
median) and the range of values in one easily interpreted
graphical format (Holland, 1990). Figure 3-1 shows the
cumulative distribution function of instantaneous bottom
dissolved oxygen (DO) concentrations for the Virginian
Province.
The x-axis represents DO concentrations observed
in 1991 ranging from 0 to 10 mg/L. The y-axis
represents the cumulative percentage of estuarine area
within the Virginian Province. The dotted lines
represent the 95% confidence intervals for the CDF (see
Appendix A). The CDF provides the reader with a
powerful tool to evaluate the extent of conditions of any
indicator within the Province or class. For example,
the reader could be interested in the portion of area
within the Province that was characterized by a DO
100
80
<
- 60
u 40
20
2468
Dissolved Oxygen ( mg/L )
10
Rgure 3-1. Example CDF of instantaneous bottom dissolved oxygen
concentrations as a percent of area in the Virginian Province.
concentration of 2 mg/L or less, a potential biological
criteria. This concentration intersects with the cumulative
area in the Province at 5 ± 5%. The reader might also
be interested in a state regulatory criteria of 5 mg/L, and
the CDF shows that, based on the 1991 sampling, 18
±8% of the estuarine bottoms waters had DO concentra-
tions below these levels. From a positive viewpoint,
the reader may be interested in the amount of area above
7 mg/L (e.g., as a criterion for fish farming) and the CDF
shows that in 1991 approximately 25 ± 10% of the bottom
waters in the Province were observed to be at or above
7 mg/L DO, based on instantaneous daytime values.
Criteria values for the assessment of degraded versus
non-degraded areas are often subjective at best. Indeed,
many of the criteria values used in this document, though
based on reasonable scientific judgement, are debatable.
The CDF allows the user to select his/her own criterion
value and re-evaluate the proportion of area in the
Virginian Province which is considered degraded. The
Page 16
Statistical Summary, EMAP-E Virginian Province - 1991
-------
reader must remain aware that the data included in this
report represents only 1A of the data that will be used
to generate the four-year assessment.
Areas reported in the text are determined from the
data, not from the CDF, and may be slightly different
than the reader might obtain from interpreting the CDF.
Data points on the CDF are connected with a straight
line, resulting in an interpolated value if there is no area
associated with the "x" value of interest.
3.1 BIOTIC CONDITION INDICATORS
Biotic condition indicators are characteristics of the
environment that provide quantitative evidence of the
status of ecological resources and the biological integrity
of the sample site from which they are collected
(Messer, 1990). Ecosystems with a high degree of
biotic integrity (i.e., "healthy" ecosystems) are composed
of . balanced populations of indigenous benthic and
water column organisms with species compositions,
diversity, and functional organization comparable to
undisturbed habitats (Karr and Dudley, 1981; Karr et
al., 1986). Biotic condition indicators measured include
measures of both fish and benthic community structure.
3.1.1 Benthic Index
An index of benthic community condition was
developed following the 1990 Demonstration Project.
When applied to the 1991 benthic dataset, the original
index failed to validate, resulting in the need to develop
a new index. This new benthic index, which uses
measures of individual health, functionality, and
community condition to evaluate the condition of the
benthic assemblage, was utilized in the assessment of
biological resources of the Virginian Province. It was
determined from the combined 1990/1991 data and is
assumed to represent a combination of ecological
measurements that best discriminates between good and
poor ecological conditions. This index represents EMAP-
E's attempt to reduce many individual indicators into
a simple value that has a high level of discriminatory
power between good and poor environmental conditions.
The reader should be cautioned that this index has not
yet been validated with an independent dataset, and
therefore, should be used with caution.
It should be noted that applying the new index to
the 1990 dataset does not significantly affect the percent
area degraded reported in the 1990 Demonstration Project
Report (Weisberg et al., 1993). Details on the validation
attempt on the 1990 index and the calculation of the 1991
benthic index can be found in. Appendix B.
120 T
-1
0
2 3 4
Benthic Index
6
Figure 3-2. Cumulative distribution of benthic index values as a percent of area in the Virginian Province, 1991. (Dashed lines are
the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 17
-------
so -
40 -
30 -
20 -
AH
Large
Small
Tidal
Figure 3-3. Percent area of the Virginian Province by estuarine
class with a benthic index value below 0 in 1991. (Error bars
represent 95% confidence intervals).
Benthic organisms were used as an indicator because
previous studies have suggested that they are sensitive
to pollution exposure (Pearson and Rosenberg, 1978;
Boesch and Rosenberg, 1981). They also integrate
responses to exposure over relatively long periods of
time. One reason for their sensitivity to pollutant
exposure is that benthic organisms live in and on the
sediments, a medium that accumulates environmental
contaminants over time (Schubel and Carter, 1984;
Nixon et al., 1986). The sedentary nature of many
benthic invertebrates also may maximize their exposure
to pollutants.
A benthic index critical value of zero was determined
from the combined 1990/1991 Virginian Province dataset.
Fourteen (± 6) percent of the bottom area of the Virginian
Province sampled in 1991 had an index value of < 0,
indicating likely impacts on the benthic community
(Figure 3-2).
The percent area classified as degraded among the
three classes of estuaries are 6 ± 7 %, 32 ± 17 %, and
27 ± 14 % for large estuaries, small estuarine systems,
and large tidal rivers, respectively (Figure 3-3).
3.1.2 Number of Benthic Species
Number of benthic species has been used to
characterize the environmental condition of estuarine
habitats for specific salinity and grain size conditions.
The mean number of infaunal species per grab from three
replicate 440 cm2 grabs collected at each station resulted
in numbers of benthic species ranging from 0 to 54
(Figure 3-4), with the maximum number of species
encountered per station being 54,42, and 15 in the large
estuaries, small estuaries, and large tidal rivers respective-
ly (Figure 3-5). Because community composition is
120 T
10 20 30 40 50
Benthic Species (Mean # per Grab)
60
Figure 3-4. Cumulative distribution of the mean number of benthic species per grab as a percent of area in the Virginian Province,
1991. (Dashed lines are the 95% confidence intervals).
Page 18
Statistical Summary, EMAP-E Virginian Province - 1991
-------
a) Large Estuaries
b) Small Estuaries
c) Tidal Rivers
10 20 30 40 50
Benthic Species (Mean # per Grab)
60
Figure 3-5. Cumulative distribution functions of the number of benthic species by estuarine class: a) Large estuaries, b) Small
estuaries, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 19
-------
strongly influenced by factors other than environmental
"health" (i.e., salinity and grain size), we cannot infer
a low number of species necessarily represents an
impacted community. However, the CDFs presented
provide baseline information and can be a useful tool
in assessing future trends in community structure.
3.1.3 Benthic Infaunal Abundance
Abundant benthic organisms, particularly in com-
munities characterized by multiple species and feeding
types, suggest a productive estuarine environment.
Infaunal abundances ranged from 0 to over 114,000
organisms per square meter (Figure 3-6). Using <200
organisms per square meter (8.8 per grab) and <500
organisms per square meter (22 per grab) as indicators
of low and moderate abundances, respectively, 6 ± 5%
of the Virginian Province had low abundances, and an
additional 3 ± 6% had moderate abundances. Because
of natural variation in benthic populations and modify-
ing factors such as salinity and grain size, low abun-
dance, as defined above, does not necessarily imply
degraded communities, however, this information can
be useful in detecting trends.
Areas of low abundance were primarily associated
with the lower salinity waters of the small estuary and
large tidal river classes, in which 13 ± 13% and 15 ±
28% of the area, respectively, had benthic infaunal
abundances less than 200 organisms per square meter
(Figure 3-7). Approximately 2 ± 4% of the sampled
large estuary area showed low abundances. The highest
number of individuals (114,674 per m2) was found in
the large estuary class, with maximums of 62,970 and
12,530 found in the small estuary and large tidal river
classes, respectively.
3.1.4 Number of Fish Species
Zero to 15 species offish were collected from single
standardized, 10-min trawls performed at each base station
in the Virginian Province (Figure 3-8). A total of 69
species were collected in standard trawls throughout the
Province in 1991. Catch statistics for target species are
shown in Table 3-1.
Fish catch can be affected by many variables
including habitat; therefore, a critical value for the
number of species that must be caught in a net for the
area to be considered "healthy" is not available. We
can only report the incidence of high vs low catches.
Low catch does not imply that the area is degraded in
reference to this indicator. However, as described above
for benthic indicators, these data can be useful in
detecting future trends in fish community structure on
a provincial scale.
120 T
0 20000 40000 60000 80000 100000 120000
Total Benthic Abundance (#/m2)
Figure 3-6. Cumulative distribution of the number of benthic organisms per m2 as a percent of area in the Virginian Province, 1991.
(Dashed lines are the 95% confidence intervals).
Page 20
Statistical Summary, EMAP-E Virginian Province - 1991
-------
a) Large Estuaries
20000 40000 60000 80000 100000 120000
b) Small Estuaries
H
20000 40000 60000 80000 100000 120000
c) Tidal Rivers
20000 40000 60000 80000 100000 120000
Total Benthic Abundance (tt/m2)
Figure 3-7. Cumulative distribution functions of the number of benthic organisms per m2 by class: a) Large estuaries, b) Small
estuaries, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 21
-------
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Number of Fish Species per Trawl
FIguro 3-8. Cumulative distribution of the number of fish species per standard trawl as a percent of area in the Virginian Province,
1991. (Dashed lines are the 95% confidence intervals).
Table 3-1. Target Fish Species Summary. Only data from trie 102 Base Stations are included. The.total number
of Individuals caught at Base Stations was 6,563 fish.
Common
Name
Atlantic Croaker
Bluefish
Channel Catfish
Scup
Spot
Summer Flounder
Weakfish
White Catfish
White Perch
Winter Flounder
Scientific
Name
Micropogonias undulatus
Pomatomus saltatrix
Ictalurus punctatus
Stenotomus chrysops
Lelostomus xanthurus
Paralichthys dentatus
Cynoscion regalis
Ameiurus catus
Morone americana
Pleuronectes americanus
# Stations
Where Caught
35
8
15
27
44
32
25
8
22
9
Total Fish of
Species
Caught
1,025
13
286
742
925
92
813
44
540
129
Two or fewer species were caught in a standard
trawl in approximately 28 ± 10% of the Virginian
Province. Alternatively, at least five fish species were
collected throughout approximately 38 ± 11% of the
sampled area of the Province. No fish were collected
at 4 stations, representing 4 ± 5% of the area of the
Province. The areas producing no fish catch were located
primarily in large estuaries (Figure 3-9). Fish were
collected in all but one small estuary station (0.3 ± 0.6%
of the area) and at all stations in the large tidal river
class (Figure 3-9).
Page 22
Statistical Summary, EMAP-E Virginian Province - 1991
-------
120
a) Large Estuaries
2 3
8 9 10 11 12 13 14 15
b) Small Estuaries
120 T
8 9 10 11 12 13 14 15
c) Tidal Rivers
140
1 1 1 1 1 1 1 1 h-
2 3 4 5 6 7 8 9 10 11 12 13 14 15
Number of Fish Species per Trawl
Figure 3-9. Cumulative distribution functions of the number of fish species per trawl by estuarine class: a) Large estuaries,
b) Small estuaries,, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 23
-------
3.L5 Total Finfish Abundance
3.1.6 Fish Gross External Pathology
Abundant nektonic organisms, especially in
communities characterized by multiple species and
feeding types, suggest a stable and productive food web.
Finfish abundance in standard trawls ranged from 0 to
650 fish per trawl throughout the Province (Figure 3-
10). A total of 7,134 fish was collected in standard
trawls, of which approximately 70% were target species.
Figure 3-11 illustrates fish abundance by system
class. Total fish catch in the large tidal river class,
although greater in number, was more variable than the
other classes as evidenced by the wide confidence
intervals about the curve.
No striking differences occur by class except the
high percentage of area in large systems with low fish
catch (36 ± 14% with <10 fish collected per trawl), and
the high catch of over 100 fish per trawl in 33 ± 33%
of the area represented by large tidal river systems.
Small estuaries were characterized by moderate fish
catch (10 to 100 fish) in 60 ± 18% of the area. As with
the fish species indicator, only high versus low catches
can be reported with no inference made on the quality
of the area relative to this indicator.
Field crews examined the first 30 individuals of each
target fish species for evidence of external pathology.
As stated in Section 4, crews were generally conservative,
and many fish identified as having a pathology, in fact,
did not. The pathologies reported are growths, lumps,
ulcers, and fin erosion. Of the 2,513 fish examined, 16
(0.6%) were identified as having one or more of these
pathologies. These individuals were collected at six of
the 101 base stations sampled during the index period.
All but one of the individuals with a pathology was a
channel or white catfish, species which live and feed
on the bottom.
Of the four categories, five lumps, nine ulcers, and
three cases of fin erosion were reported (17 pathologies
identified on 16 fish).
3.7.7 Fish Tissue Contaminants
As part of the suite of fish indicators, field crews
collected up to five individuals of each target species
present at each station for chemical residue analysis.
Samples analyzed in the laboratory were composites of
these individuals by species. In the laboratory, the
individual fish were filleted and a composite sample
100 200 300 400 500
Number of Fish per Trawl
600
700
Figure 3-10. Cumulative distribution offish abundance in numbers per standard trawl as a percent of area in the Virginian Province;
1991. (Dashed lines are the 95% confidence intervals).
Page 24
Statistical Summary, EMAP-E Virginian Province - 1991
-------
a) Large Estuaries
100
200 300 400 500 600 700
b) Small Estuaries
100 200 300 400 500 600
700
c) Tidal Rivers
-i
100 200 300 400 500
Number of Fish per Trawl
600 700
Figure 3-11. Cumulative distribution functions of fish abundance in numbers per trawl by estuarine class: a) Large estuaries,
b) Small estuaries, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 25
-------
created from the muscle tissue. A total of 84 compos-
ites of 3-5 individuals per composite were analyzed for
the list of contaminants presented in Appendix A. No
sample exceeded FDA action limits (or, where FDA
action limits were not available, the mean of interna-
tional limits) for any of the organic analytes measured
Table 3-2). White perch generally contained the highest
levels of organic contaminants among the samples
analyzed. Several metals (arsenic, chromium and
selenium) exceeded criteria values (shown as bold type
in Table 3-2), with the highest incidence of exceedences
being measured for arsenic. Fourteen of the 82
composite samples analyzed for metals (two samples
were lost) exceeded the criteria value (2 ug/g wet
weight). Six of these were winter flounder, whereas
none of the summer flounder composites analyzed
contained levels above 2 ug/g. Four of the six winter
flounder collection sites were in mid-Long Island Sound,
one was in Nantucket Sound, and one in Peconic Bay.
Summer flounder samples were not collected at these
stations.
3.2 ABIOTIC CONDITION INDICATORS
Abiotic condition indicators provide information on
the potential exposure of organisms to environmental
stresses, and have historically been the mainstay of
environmental monitoring programs. Indicators of
exposure measured during the 1991 Virginian Province
Survey were dissolved oxygen concentration (instan-
taneous and 24-hr continuous), sediment toxicity
(Ampelisca abdita), sediment contaminants, and marine
debris.
3.2.1 Dissolved Oxygen
Dissolved oxygen (DO) is critically important to
aquatic systems because it is a fundamental requirement
of fish, shellfish and other aquatic biota. DO was
measured in two ways during the 1991 survey of the
Virginian Province: instantaneous point measurements,
and continuous measurements (from deployed instru-
ments) at base stations for a minimum of 24 hours.
"Bottom" relative to dissolved oxygen and other water
quality measurements is defined as one meter above the
sediment/water interface.
3.2.1.1 Bottom Dissolved Oxygen -Instantaneous
/
Data collected in 1991 indicate that approximately
18 ± 8% of the sampled area of the Province contains
bottom waters with a dissolved oxygen concentration
less than or equal to 5 mg/L (Figure 3-12). Approxi-
mately 5 ± 5% of the Province exhibited bottom DO
conditions <2 mg/L, defined by EMAP-E as severely
hypoxic.
Dissolved oxygen conditions <2 mg/L were evident
in'all classes of estuaries sampled within the Province
(Figures 3-13 and 3-14). Approximately 4 ± 6%, 1 ±
2%, and 15 ± 28% of the areas of large estuaries, small
estuaries, and large tidal rivers, respectively, contained
measured concentrations of bottom DO of < 2.0 mg/L.
An additional 13 ± 10%, 20 ± 13%, and 3 ± 28% of the
area of large estuaries, small estuaries, and large tidal
rivers, respectively, fell within the range of 2 to 5 mg/L
DO. .-,
The incidence of low dissolved oxygen in Chesapeake
Bay and Long Island Sound is an area of importance
to both scientists and managers; therefore, estimates for
these systems are included in Appendix C.-
3.2.1.2 Bottom Dissolved Oxygen - Continuous
In addition to single point measurements of DO at
a station at a specific time, continuous bottom measure-
ments of DO were made for a minimum of 24 hours using
a Hydrolab DataSonde 3 datalogger deployed one meter
off the bottom at base stations. Measurements were taken
every 15 minutes until the unit was retrieved. Continuous
DO measurements should provide a more complete picture
of the dissolved oxygen conditions at a station (i.e., by
monitoring the periods when benthic and water column
respiration is higher) than instantaneous measurements.
Minimum DO concentrations, as determined from the
full Hydrolab data set from each base station over the
entire Province, ranged from 0.0 to 8.3 mg/L (Figure
3-15). These data show that approximately 8 ± 7% of
the sampled area of the Province experienced DO concen-
trations as low as 2 mg/L over the 24 hour period of
deployment, compared to an estimate of 5 ± 5% for
instantaneous measurements.
Page 26
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Table 3-2. Results of chemical analysis of fish muscle tissue. Maximum concentration measured and percent
composite samples exceeding criteria values (in parentheses) are presented.
Analyte
Criteria
Value
Number of composites
organics/metals
Atlantic
Croaker
10/9
Bluefish
1/1
Channel
Catfish
5/5
Scup
11/10
Spot
20/20
Weakfish
8/8
White
Perch
18/18
Summer
& Winter
Flounder
•1 1/1 1
All
Species
54/82
Maximum concentration
(% exceeding criteria)
Organic Contaminants (ng/g wet weight)
Aldrin
Dieldrin
Heptachlor
Heptachlor
Epoxide
Hexachloro-
benzene
Lindane
Mi rex
Total
chlordanes3
Total DDTsb 5
Total PCBsc 2
Metals (pg/g wet
As
Cd
Cr
Cu
300
300
300
300
200
200
100
300
,000
,000
0.06
(0%)
5.05
(0%)
0.09
(0%)
0.88
(0%)
0.47
(0%)
0.85
(0%)
0.42
(0%)
7.01
(0%)
22.1
(0%)
90.3
(0%)
0.00
(0%)
3.42
(0%)
0.00
(0%)
0.12
(0%)
0.10
(0%)
0.00
(0%)
0.20
(0%)
9.69
(0%)
37.8
(0%)
91.5
(0%)
0.00
(0%)
10.5
(0%)
0.23
(0%)
4.89
(0%)
0.36
(0%)
1.53
(0%)
0.47
(0%)
59.2
(0%)
97.6
(0%)
317
(0%)
0.00
(0%)
4.37
(0%)
0.00
(0%)
0.09
(0%)
0.13
(0%)
0.76
(0%)
0.13
(0%)
3.26
(0%)
25.2
(0%)
150
(0%)
0.02
(0%)
8.43
(0%)
0.03
(0%)
0.45
(0%)
0.17
(0%)
1.27
(0%)
0.23
(0%)
5.77
(0%)
66.9
(0%)
117
(0%)
0.00
(0%)
2.85
(0%)
0.00
(0%)
0.29
(0%)
0.72
(0%)
0.52
(0%)
0.38
(0%)
3.90
(0%)
51.0
(0%)
204
(0%)
0.15
(0%)
52.8
(0%)
0.14
(0%)
5.29
(0%)
1.68
(0%)
1.48
(0%)
0.60
(0%)
102
(0%)
1,490
(0%)
1,150
(0%)
0.00
(0%)
1.09
(0%)
0.00
(0%)
0.10
(0%)
0.10
(0%)
0.53
(0%)
0.09
(0%)
3.37
(0%)
12.9
(0%)
72.1
(0%)
0.15
(0%)
52.8
(0%)
0.23
(0%)
5.29
(0%)
1.68
(0%)
1.53
(0%)
0.60
(0%)
102
(0%)
1,490
(0%)
1,150
(0%)
weight) .
2
0.5
1
15
2.25
(11%)
0.02
(0%)
0.25
(0%)
2.77
(0%)
0.15
(0%)
0.00
(0%)
0.00
(0%)
1.15
(0%)
0.09
(0%)
0.01
(0%)
0.10
(0%) .
1.95
(0%)
5.07 3.17
(30%) (20%)
0.01
(0%)
0.55
(0%)
2.26
(0%)
0.08
(0%)
0.32
(0%)
3.11
(0%)
0.68
(0%)
0.00
(0%)
1.95
(13%)
1.14
(0%)
0.45
(0%)
0.01
(0%)
1.22
(6%)
1.64
(0%)
**
5.52
(5,5%)
0.00
(0%)
0.33
(0%)
1.45
(0%)
5.52
(17%)
0.08
(0%)
1.95
(2%)
3.11
(0%)
(continued)
Statistical Summary,
EMAP-E
Virginian
Province
- 1991
Page 27
-------
Table 3-2 continued.
Maximum concentration
(% exceeding criteria)
Analyte
Pb
Hg
So
Zn
Criteria
Value
0.5
1
1
60
Atlantic
Croaker
0.04
(0%)
0.02
(0%)
0.78
(0%)
8.86
(0%)
Bluefish
0.00
(0%)
0.05
(0%)
0.32
(0%)
7.88
(0%)
Channel
Catfish
0.00
(0%)
0.04
(0%)
0.56
(0%)
6.44
(0%)
Scup
0.03
(0%)
0.07
(0%)
0.64
(0%)
9.85
(0%)
Spot
0.03
(0%)
0.03
(0%)
0.80
(0%)
11.7
(0%)
Weakfish
0.04
(0%)
0.07
(0%)
0.82
(0%)
37.7
(0%)
White
Perch
0.06
(0%)
0.26
(0%)
1.55
(17%)
12.7
(0%)
Summer
& Winter
Flounder
0.07
(0%)
0.03
(0%)
0.67
(0%)
10.5
(0%)
All
Species
0.07
(0%) .
0.26
(0%)
1.55
(4%)
37.7
(0%)
Criteria values from U.S. FDA (1982, 1984), or, where FDA values were not available, from Nauen (1983).
Represents only those species included in this table.
Up to five individuals from selected target species were composited to create the sample analyzed. Two samples for metals
analyzed were lost, resulting in fewer samples (82 compared to 84 for organics analyses).
"Total Chlordanes" Is the sum of alpha-chlordane, heptachlor, heptachlor epoxide, and trans-nonachlor.
•Total DOTS' is the sum of o'.p' DDE, p'.p1 DDE, o'.p1 ODD, p'.p1 ODD, o'.p' DDT, and p'.p1 DDT.
Concentrations reported for "Total PCBs" are the sum of measured congeners (PCBs 8,18, 28, 44, 52, 66,101,105,118,
128,138,153,170,180,187,195,206, and 209) and may not be directly comparable to the criteria values for Total PCBs.
All six winter flounder composites exceeded the criteria value for Arsenic, with the minimum concentration measured being
2.09 yg/g, and the median being 4.20 ug/g. None of the five summer flounder composites exceed the criteria value.
Page 28
Statistical Summary, EMAP-E Virginian Province - 1991
-------
3 4 5 6, 7
Dissolved Oxygen (mg/L)
8
10
Figure 3-12. Cumulative distribution of instantaneous bottom dissolved oxygen concentration as a percent of area in the Virginian
Province, 1991. (Dashed lines are the 95% confidence intervals).
120
2 to 5
All Large Small Tidal
Figure 3-13. The percent of area by class that had a low (< 2 mg/L), medium (2 to 5 mg/L), or high (>5 mg/L)
oxygen concentration in the bottom waters. (Error bars represent 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 29
-------
a) Large Estuaries
120 T
b) Smalt Estuaries
c) Tidal Rivers
140 -
120 -
-------
3456
Dissolved Oxygen (mg/L).
8
Figure 3-15. Cumulative distribution of the minimum bottom oxygen concentration measured over a 24-hour period as a percent of
area in the Virgjnfan Province, 1991. (Dashed lines are the 95% confidence intervals).
The percent area classified as degraded based on a
value of <2 mg/L in the Virginian Province calculated
from continuous and instantaneous DO measurements
do not differ significantly. Data collected during the
1990 Demonstration Project show that temporal
variability in DO concentration is less diurnal than in
other regions (i.e., the Gulf of Mexico), and that a much
longer time series is required to "better" classify a
station as degraded than a simple point measurement.
This, in addition to the logistics and additional cost
involved in the relatively short-term deployment of the
DataSondes, resulted in this measurement being
discontinued after 1991.
3.2.1.3 Dissolved Oxygen Stratification
The difference between surface and bottom DO
concentrations measured at base sampling stations is
illustrated in Figure 3-16. Differences between bottom
and surface DO were less than 1 mg/L in 67 ± 10% of
the area of the Province. Approximately 8 ± 6% of the
area of the Province showed differences greater than 5
mg/L. This agrees with the data presented on stratifica-
tion in Section 3.3.5 in which 76 ±10% of the Province
was found to be well-mixed and 7 ± 7% significantly
stratified.
Figure 3-17 illustrates DO differences by estuarine
class. All of the highly stratified area was found in the
large estuaries and large tidal rivers (8 ± 8% and 17 ±
32%, respectively, exceeding 5 mg/L), with the largest
A DO measured being 7.8 mg/L.
3.2.2 Sediment Toxicity
Sediment toxicity tests were performed on the
composite sample of surficial sediments collected from
each sampling site. Solid-phase sediment toxicity tests
(Swartz et al., 1985) with the tube-dwelling amphipod,
Ampelisca abdita, were conducted according to procedures
described in U.S. EPA/ACE (1991) and ASTM (1991).
Sediments were classified as toxic if amphipod survival
in the test sediment was less than 80% of that in the
control sediment and significantly different. Approxi-
mately 21 ± 10% of the sampled area of the Virginian
Province exhibited toxic sediments (Figure 3-18).
However, only 1 ± 10% of the area had sediments where
survival fell below 60% of control survival {i.e.,
sediments were very toxic). The estuarine class with
the largest proportion of toxic sediments was the large
estuarine class (24 ± 13%); with the small estuaries and
large tidal river classes exhibiting a lesser extent of
toxicity (19 ± 14% and 10 ± 7%, respectively: Figure
3-19). However, the confidence intervals around all these
Statistical Summary, EMAP-E Virginian Province - 1991
Page 31
-------
120 T
0
234567
Dissolved Oxygen Difference (mg/L)
Rgure 3-16. Cumulative distribution of the dissolved oxygen concentration difference between surface and bottom waters as a percent
of area In the Virginian Province, 1991. (Dashed lines are the 95% confidence intervals).
100i
1 to 5
>5
All Large Small Tidal
Figure 3-17. The percent of area by class that had a low, medium, or high difference in dissolved oxygen
concentration (mg/L) between the surface and bottom waters. (Error bars represent 95% confidence intervals).
Page 32
Statistical Summary, EMAP-E Virginian Province - 1991
-------
120 T
30 40 50 60 70 80 90
Mean Amphipod Survival (% of Control)
100
Figure 3-18. Cumulative distribution of mean survival of amphipods in 10-day laboratory toxicity tests (expressed as percent of control
survival). (Dashed lines are the 95% confidence intervals).
40
30 .
CO
2
•5 20
c
-------
values overlap, therefore, there may be no significant
differences among classes. The most toxic sediments
were found in the small estuarine class, where 5 ± 7%
of the area had sediments producing survival of less
than 60% of control.
SQC values for the four analytes measured are listed
in Table 3-3, along with the upper and lower bounds.
It is important to note that these values are still in draft
form and are subject to change as the documents proceed
through the peer review process.
3.2.3 Sediment Contaminants
A wide variety of contaminants have been released
to marine systems due to human activities. Some of
these compounds and elements have properties which
cause them to associate with particulate material. Many
of these chemicals are also persistent in the environ-
ment. Contaminants with this combination of properties
can accumulate to high concentrations in sediments and
may become available to aquatic organisms. The
analytes measured included selected polycyclic aromatic
hydrocarbons (PAHs), polychlorinated biphenyl (PCB)
congeners, chlorinated pesticides, butyltins and several
metals. Because of the complex nature of sediment
geochemistry, and additive, synergistic, and antagonistic
interactions among multiple pollutants, the ecological
impact of elevated contaminant levels is not well under-
stood. Therefore, definitive estimates of percent area
of the Province with overall contaminant concentrations
high enough to cause ecological impacts cannot be
provided. However, the data collected will form a
baseline for monitoring trends in sediment contamina-
tion and are extremely valuable in that respect.
EPA is currently in the process of establishing
Sediment Quality Criteria (SQC). Draft SQC are
presently available for four of the analytes EMAP-VP
is measuring: Acenaphthene, phenanthrene, fluoran-
thene, and dieldrin (U.S. EPA, 1993a-d). SQC are ex-
pressed as pg analyte/g organic carbon; therefore,
concentrations must first be normalized for the organic
carbon content of the sediment. Only those sediments
with organic carbon concentrations >0.2% can be
examined using this approach. Separate SQC values
have been established for freshwater and saltwater
sediments. Because criteria values are based on toxicity
data, the definition of saltwater vs freshwater is based
on the organisms present, not the salinity. Where both
fresh and saltwater organisms are present, the more
protective of the two values is applied.
Table 3-3. U.S. EPA draft Sediment Quality Criteria for
analytes measured. Freshwater (F), Saltwater
(S), and upper and lower confidence intervals are
included. All values are ug/g organic carbon.
Analyte
F/S
SQC
Upper
SQC
Lower
SQC
Acenaphthene
Phenanthrene
Fluoranthene
Dieldrin
F
S
F
S
F
S
130
230
180
240
510
650
280
500
390
510
1100
1400
62
110
85
110
240
300
F
S
11
20
24
44
5.2
9.5
3.2.3.1 Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are
ubiquitous in marine sediments (Laflamme and Hites,
1978). These compounds are widespread because of
the large number and variety of PAH sources which
include oil spills, natural oil seeps, forest fires, automo-
bile exhaust, domestic heating, power plants and other
combustion processes. With the exception of specific
oil releases, the majority of PAHs found in marine
sediments are believed to originate from combustion
processes (Windsor and Hites, 1979). PAH concentrations
tend to correlate with the degree of urbanization or
industrialization and, therefore, these compounds are
often considered to be indicators of anthropogenic
activity.
Range and median concentrations for PAHs measured
in 1991 are listed in Table 3-4. Combined PAH values
reported in this table reflect the summation of the
concentrations of all of the PAH compounds that were
Page 34
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Table 3-4. Range and median PAH concentrations in sediments of the Virginian Province, 1991.
Analyte (weight )
Concentration (ng/g dry weight)
MIN
MAX
Median
Median
Detection Limitb
Acenaphthene (L)
Acenaphthlylene (L)
Anthracene (H)
Benz(a)anthracene (H)
Benzo(b+k)fluoranthene (H)
Benzo(g,h,i)perylene (H)
Benz(a)pyrene (H)
Benz(e)pyrene (H)
Biphenyl (L)
Chrysene (H)
Dibenz(a,h)anthracene (H)
Fluoranthene (H)
Fluorene (L)
lndeno(1,2,3-c,d)pyrene (H)
Naphthalene (L)
1-methylnaphthalene (L)
2-methylnaphthalene (L)
2,6-dimethylnaphthalene (L)
2,3,5-trimethylnaphthalene (L)
Perylene (H)
Phenanthrene (H)
1-methylphenanthrene (H)
Pyrene (H)
Combined PAHs
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
2,960
186
6,510
10,000
11,300
3,780
6,040
3,950
240
9,770
342
22,900
3,180
4,080
488
386
459
399
518
2,020
25,500
2,100
24,600
141,000
ND
ND
ND
19.0
50.9
20.2
20.3
19.0
ND
27.3
ND
40.2
ND
22.5
16.7
ND
15.5
ND
ND
38.4
31.4
ND
46.2
484
9.98
9.98
9.98
9.95
9.98
9.97
9.99
9.99
9.95
9.96
9.98
9.95
9.95
9.98
9.98
9.95
9.95
9.95
9.94
9.98
9.98
9.95
9.98
na
Letter in parenthesis indicates high molecular weight compound (H) or low molecular weight compound (L).
For each "not detected" the laboratory supplied a detection limit. This value is the median of these values
for each analyte.
na = not applicable
ND = not detected
measured. This summation is not listed as "total" PAH
because only a select list of PAHs were measured and
many other PAH compounds could be found in these
sediments. Combined PAH concentrations for low level
samples are artificially low because analytes that were
not detected were assigned a value of zero for calcula-
tion of the Combined concentration. Combined PAH
concentrations (Table 3-4) showed a large range (ND -
141,000 ng/g) with a median concentration of 484 ng/g
in Virginian Province sediments. The station with the
highest concentration of PAHs was located near a
shipping channel at the mouth of Chesapeake Bay in
a sandy environment. Sediments from this station did
not show any toxicity, analytes other than PAHs were
not elevated, and the benthic community was not
indicative of a degraded environment. All evidence
Statistical Summary, EMAP-E Virginian Province - 1991
Page 35
-------
suggests that this exceedence was an artifact, possibly
due to a "chip" of material dislodged from the smoke-
stack of a passing ship. Eliminating this station results
in a maximum combined PAH concentration of 80,100
ng/g.
This large range of PAH concentrations can be seen
in the cumulative distribution of combined PAHs shown
in Figure 3-20a&b (note: data from the station discussed
above are not included in this figure). This figure
shows that the sediments of the vast majority of the area
of the Province contain low concentrations of PAHs;
for example, about 94 ± 6% of the sampled area of the
Province had a combined sediment PAH concentration
of less than 4,000 ng/g dry weight. This value has no
ecological significance; however, it does appear as an
inflection point in the CDF. Figure 3-20b is the CDF
plotted on a log scale to better illustrate the distribution
of concentrations at the lower end of the scale.
As discussed above, draft Sediment Quality Criteria
are available for three PAHs: Acenaphthene, phenan-
threne, and fluoranthene. The percent areas exceeding
SQC (see Table 3-3) in freshwater and saltwater
sediments combined shows that 2 ± 5% of the area of
the Virginian Province contains sediments exceeding
EPA criteria for each of these PAHs. These exceed-
ences were measured at only three stations within the
Province. The station representing the largest area was
the one discussed above. Eliminating this station results
in 0 ± 0%, 0.3 ± 5% (one station) and 0.4 ± 4% (two
stations) of the area of the Province exceeding SQC for
acenaphthene, phenanthrene and fluoranthene, respec-
tively. Both stations where exceedences were noted
were in small estuaries. Applying the more conservative
Lower SQC values in Table 3-3 does not change these
percentages. It is important to note that these estimates
were based on only those sediments with a total organic
carbon content of £0.2% (81 ± 9 % of the area of the
Province). For the purpose of this exercise, those
stations excluded were treated statistically as missing
values.
Petroleum and combustion-type PAH sources contain
very different PAH compound distributions. Because
of this, the distributions of PAHs in a sample can
provide information on the relative importance of petro-
leum versus combustion PAH sources (Lake et al.,
1979).
Petroleum products contain relatively large amounts
of lower molecular weight compounds relative to combus-
tion sources which are dominated by higher molecular
weight compounds.
The CDF of the relative percent of high molecular
weight compounds (sum high MW PAHs/sum of all PAHs
x 100: see Table 3-4 for a listing of "high molecular
weight PAHs) shown in Figure 3-21 indicates that the
majority of the Province area contains PAH distributions
dominated by higher molecular weight compounds. This
indicates that combustion processes are the dominant
sources of these compounds in the Province. The percent
high molecular weight PAH component (of total PAHs)
was less than 50% for only a single station which was
located in the large estuary class.
3.2.3.2 Polychlorinated Biphenyls
Environmental measurements of PCBs have been
conducted using a variety of techniques including their
measurement as industrial mixtures (e.g., Aroclors)
(Hutzinger, 1974), by level of chlorination (Gebhart et
al., 1985) and as individual congeners (Mullin, 1984;
Schantz et al., 1990). Each of these techniques have
both positive and negative aspects based on the specific
application for which the PCB data are needed. For this
study, PCBs were measured as a series of 18 selected
congeners (Table 3-5). These congeners were selected
to produce data consistent with the National Oceano-
graphic and Atmospheric Administration's, National Status
and Trends Program. The congeners included on this
list are some of the more abundant chlorobiphenyls found
in environmental samples as well as some (congeners
105 and 118) that are considered to have a high potential
for toxicity (McFarland and Clarke, 1989).
The PCB congeners measured are identified based
on the numbering convention proposed by Ballschmiter
and Zell (1980). Concentration ranges and median values
measured for the individual congeners are listed in Table
3-5. Also included in this table is a summation of the
measured congeners referred to as combined PCBs. This
term was used instead of "total" PCBs to differentiate
it from measurements of all of the PCBs in a sample.
Combined PCB concentrations for low level samples
are artificially low because congeners that were not
detected were assigned a value of zero for calculation
of the combined concentration. Combined PCB
Page 36
Statistical Summary, EMAP-E Virginian Province - 1991
-------
(a)
120
100
8 80
0>
60
40
20
0 4
1 23456
Combined PAHs (ng/g dry wt x 10,000)
10 100 1000 10000
Combined PAHs (ng/g dry wt)
100000
Figure 3-20. Cumulative distribution of combined PAHs in sediments as percent of area in the Virginian Province, 1991: a) linear
scale, b) logarithmic scale. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 37
-------
120
TO 20 30 40 50 60 70 80 90
High Molecular Weight PAHs (% of Combined PAHs)
100
Figure 3-21. Cumulative distribution of the relative percentage of high molecular weight PAHs in sediments as percent of area in
the Virginian Province, 1991. (Dashed lines are the 95% confidence intervals).
concentrations ranged from the detection limit to 1,020
ng/g dry weight with a median concentration of 3.52
ng/g. The cumulative distribution of combined PCBs
in the Virginian Province is shown in Figure 3-22a&b.
This plot shows that low concentrations of PCBs were
found in the majority of the area of the Province. PCBs
were not detected in 40 ± 11 % of the area of the
Province and approximately 95 ± 5% of the Province
contained sediments with PCB concentrations below 50
ng/g dry weight. This value has no ecological signifi-
cance; however, it does appear as an inflection point
in the CDF. Figure 3-22b is the CDF plotted on a log
scale to better illustrate the distribution of concentra-
tions at the lower end of the scale.
3.2.3.3 Chlorinated Pesticides
In addition to PCBs, several other chlorinated com-
pounds were also monitored in the sediments of the
Virginian Province (Table 3-6). Most of these chemi-
cals are banned in the United States although some are
still used in other countries. Several of the compounds
measured (e.g., DDEs, DDDs and heptachlor epoxide)
are environmental metabolites of the original pesticides
(Ernst, 1984) instead of the active ingredients of the
original pesticide formulations.
Six DDT-series compounds were measured. These
included the original insecticide, p,p'-DDT, and o,p'-DDT
which was a contaminant in p,p'-DDT formulations.
The four remaining compounds (p,p'-DDE, o,p'-DDE,
p,p'-DDD and o,p'-DDD) are metabolites or degradation
products of p,p'-DDT and o,p'-DDT, respectively. The
use of DDT is now banned in the United States. DDT-
series compounds were generally the most abundant of
the chlorinated pesticides measured in the Virginian
Province sediments (Table 3-6). The CDF of p,p'-DDE
is presented in Figure 3-23 as an example of the
distribution of DDT-series compounds seen in the
Virginian Province. As was previously seen for PAHs
and PCBs, the majority of the area of the Province con-
tains low p,p'-DDE levels (94 ± 6% of the area less than
4 ng/g). This value has no ecological significance;
however, it does appear as an inflection point in the CDF.
Chlordane is a pesticide that was widely used to con-
trol termites and other insects, but its use was severely
restricted in 1987. It was sold as a technical mixture
containing well over 100 chlorinated compounds (Dearth
and Hites, 1991), many of which are persistent in the
environment and have been found widely distributed
in marine sediments. Two of these compounds (alpha-
chlordane and trans-nonachlor) were measured in the
sediments of the Virginian Province (Table 3-6). The
maximum concentrations observed for these compounds
Page 38
Statistical Summary, EMAP-E Virginian Province - 1991
-------
were 7.32 and 3.83 ng/g dry weight for alpha-chlordane
and trans-nonachlor, respectively. Figure 3-24 shows
the cumulative distribution observed for alpha-chlordane
in sediments of the Virginian Province. This plot shows
that alpha-chlordane was not detected in 83 ± 8% of the
area of the Province. The remaining pesticides mea-
sured generally showed concentrations near the
analytical detection limits in most samples (Table 3-6).
The only cb'crinated pesticide measured by EMAP-VP
in sediments for which there is a draft Sediment Quality
Criteria for is dieldrin. Draft EPA criteria were not
exceeded at any station within the Virginian Province
in 1991. It is important to note that this estimate was
based on only those sediments with a total organic carbon
content of >0.29> (81 ±9% of the area of the Province).
For the purpose of this exercise, those stations excluded
were treated statistically as missing values.
Table 3-5.
Range and median PCB concentrations in sediments of the Virginian Province, 1991.
Analyte
MIN
Concentration (ng/g dry weight)
MAX
Median
Median
Detection Limit3
PCB8
PCB18
PCB28
PCB44
PCB52
PCB66
PCB101
PCB105
PCB118
PCB128
PCB138
PCB153
PCB170
PCB180
PCB187
PCB195
PCB206
PCB209
Combined PCBs
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
35.4
50.7
346
72.6
107
152
53.2
34.8
55.7
8.94
42.2
31.1
7.82
17.9
14.4
5.12
10.3
18.2
1,040
0.317
ND
0.33
ND
ND
0.431
0.393
0.259
0.422
ND
0.43
0.485
ND
ND
ND
ND
ND
ND
3.46
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
na
a For each "not detected" the laboratory supplied a detection limit. This value is the median of these values
for each analyte.
na = not applicable
ND = not detected
Statistical Summary, EMAP-E Virginian Province - 1991
Page 39
-------
120 T
100 :"--
£ 80
Z 60 I
0)
I 40|
20
0
0 100 200 300 400 500 600 700 800 900 1000 1100
Combined PCBs (ng/g dry wt)
(b)
120
100
£ 80 +
-------
Table 3-6. Range and median chlorinated pesticide concentrations in sediments of the Virginian Province,
1991.
Analyte
MIN
Concentration (ng/g dry weight)
MAX
Median
Median
Detection Limit3
o,p'-DDD
p,p'-DDD
o,p'-DDE
p,p'-DDE
o,p'-DDT
p,p'-DDT
Aldrin
Alpha-Chlordane
Dieldrin
Heptachlor
Heptachlor epoxide
Hexachlorobenzene
Lindane (gamma-BHC)
Mirex
Trans-Nonachlor
Total chlordanesb
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
13.1
32.9
12.9
30.8
12.7
33.3
1.82
7.32
4.56
3.19
0.96
3.21
0.46
0.62
3.83
10.4
ND
ND
ND
0.723
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
0.249
na
For each "not detected" the laboratory supplied a detection limit. This value is the median of these values
for each analyte.
b Total chlordanes is the sum of alpha-chlordane, heptachlor, heptachlor epoxide, and trans-nonachlor.
ND = not detected
3.2.3.4 Butyltins
Until its recent ban for most uses (Huggett et al.,
1992), tributlytin (TBT) was used in many boat anti-
fouling paint formulations. As a result of this usage,
TBT and its breakdown products, dibutyltin (DBT) and
monobutyltin (MET) have subsequently been detected
in many harbors (Seligman et al., 1989). The presence
of TBT in aquatic systems has generated considerable
concern because of the potent effects of this compound
on some species (Rexrode, 1987; Heard et al., 1989).
Tributlytin can be rapidly converted to DBT and MET
in the water column but may be relatively resistant to
degradation in marine sediments (Adelman etal., 1990).
The concentrations of butyltin compounds in this report
are reported as nanograms of the respective butyltin ion
per gram of dry sediment. Caution should be noted when
comparing TBT concentrations among studies because
of the different ways that it is reported (e.g., sometimes
reported as ng tin /g).
The maximum TBT concentration observed was 240
ng/g; DBT and MET levels were generally lower than
those of TBT (Table 3-7). Figure 3-25 shows the cumula-
tive distribution of TBT in sediments as a percent of
area in the Virginian Province. TBT was not detected
(detection limit of approximately 12 ng/g) in 72 ± 10%
of the area of the Province and 89 ± 8% of the area con-
tained sediments with TBT concentrations of less than
25 ng/g.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 41
-------
120 T
100
e 80 +
~ 60
0)
e
S. 40
20
10 15 20 25
p,p' - DDE (ng/g dry wt)
30
35
Figure 3-23. Cumulative distribution of p, p' -DDE in sediments as percent of area in the Virginian Province, 1991. (Dashed lines
are the 95% confidence intervals).
120
100 -
£ 80
~ 60
o>
o
S. 40
20 -
0 4
01 2345678
Alpha-Chlordane (ng/g dry wt)
Figure 3-24. Cumulative distribution of alpha-chlordane in sediments as percent of area in the Virginian Province, 1991. (Dashed
lines are the 95% confidence intervals).
Page 42
Statistical Summary, EMAP-E Virginian Province - 1991
-------
50 100 150 200
Tributyltin (ng TBT+ / g dry wt)
250
Figure 3-25. Cumulative distribution of tributyltin in sediments as percent of area in the Virginian Province, 1991. (Dashed lines are
the 95% confidence intervals).
Table 3-7. Range and median butyltin concentrations in sediments of the Virginian Province, 1991.
Concentration (ng ion /g dry weight)
Analyte
MIN
MAX
Median
Median
Detection Limit3
Monobutyltin (MBT3)
Dibutyltin (DBT2)
Tributyltin (TBT+)
ND
ND
ND
108
98.6
240
ND
ND
ND
17.6
9.74
12.1
For each "not detected" the laboratory supplied a detection limit. This value is the median of these values
for each analyte.
ND = not detected
3.2.3.5 Total Organic Carbon
Organic carbon as measured here in the sediments
includes all forms of carbon except carbonate. Organic
carbon accumulates in sediments of the marine environ-
ment as a function of the proximity and magnitude of
the various sources of organic matter and the physical,
and biological factors that influence erosion and
deposition. The presence of organic matter is an
important modifier of the physical and chemical condi-
tions in the benthic ecosystem and serves as the primary
source of food for the bottom fauna. As discussed earlier,
Statistical Summary, EMAP-E Virginian Province - 1991
Page 43
-------
organic carbon also plays a critical role in the geochem-
istry of organic contaminants in sediments.
The organic carbon content measured in sediments
of the Virginian Province ranged from 0.065 to 3.98%
by weight. The CDF of percent area as a function of
the total organic carbon present in the sediments for all
estuaries is shown in Figure 3-26. In 81 ± 9% of the
area sampled in 1991 the sediments contained >0.2%
TOC, concentrations allowing the use of existing
Sediment Quality Criteria for evaluating contaminant
effects. The pattern is largely determined by the large
estuaries (Figure 3-27) which account for the largest part
of the Province area.
3.2.3.6 Acid Volatile Sulfides
Acid volatile sulfides are defined as the fraction of
sulfide in the sediments that can be extracted with cold
hydrochloric acid. They exist in sediments mainly as
iron monosulfide complexes, and are important in
determining the biological availability of a number of
cationic metals, primarily zinc, lead, copper, nickel, and
cadmium. Acid volatile sulfides measured in sediments
of the Virginian Province ranged from 1.39 to 5,000
mg/kg dry weight sediment. The CDF of percent area
as a function of A VS concentration is shown in Figure
3-28.
In general, the AVS concentration in the sediment
increases with increasing silt-clay and organic content
of the sediments and decreasing dissolved oxygen.
However there are exceptions to this pattern. Oxidation
of the sediments by physical or biological activity may
result in lower than expected AVS readings for a given
organic and silt-clay content of the sediment. For
example, the physical mixing energy present in large
tidal rivers and the absence of low DO may have been
responsible for the observation that measured AVS
concentrations in those sediments did not exceed 279
mg/kg or 8.7 um/g (Figure 3-29).
Occasionally, a sample with high silt-clay and organic
carbon content would have a low AVS concentration
which could not readily be explained. These samples
may have been partially oxidized in the process of sample
collection, transport, and analysis. Sediments collected
for chemical analysis (including AVS) were a composite
of the surficial layer from multiple grabs. The sediments
were thoroughly mixed to produce this homogenate.
It is very likely that this mixing process resulted in the
oxidation of some of the AVS, reducing the measured
concentrations. Collection methodology was changed
in 1992 to eliminate this problem.
120
01234
Total Organic Carbon (% dry wt)
Figure 3-26. The cumulative distribution of the percent total organic carbon in sediments as a percent of area in the Virginian Province,
1991. (Dashed lines are the 95% confidence intervals).
Page 44
Statistical Summary, EMAP-E Virginian Province - 1991
-------
a) Large Estuaries
b) Small Estuaries
c) Tidal Rivers
01234
Total Organic Carbon (% dry wt)
Figure 3-27. Cumulative distribution functions of total organic carbon in sediments by estuarine class: a) Large estuaries,
b) Small estuaries, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 45
-------
120
1000 2000 3000 4000
Acid Volatile Su If ides (mg/kg)
5000
Figure 3-28. The cumulative distribution of the acid volatile sulfide concentration in sediments as a percent of area in the Virginian
Province, 1991. (Dashed lines are the 95% confidence intervals).
3.2.3.7 Metals
The median concentration and range of metals that
were measured in 1991 are listed in Table 3-8. Elemen-
tal concentrations in sediments are highly variable, due
not only to contaminant inputs, but to natural differences
in sediment types as well. Several approaches have
been used to normalize sediment metals concentrations
for variations due to sediment type differences. Three
major crustal elements; aluminum, iron and manganese
were measured in this program for possible use in nor-
malizing elemental concentrations among sediments.
Based on several recent studies, aluminum was selected
as the most appropriate element with which to normalize
contaminant metal concentrations. The normalization
process utilized is discussed in Appendix A. Determina-
tion of metal-aluminum relationships in background
sediments enables estimation of the extent of enrichment
of metals in sediments.
Figure 3-30 presents an example (chromium) of the
1991 sediment metals data for the Virginian Province.
The predicted metal-aluminum relationship (solid line)
is obtained from the regression, along with the upper
bound of the 95% confidence interval for predicted
values (dashed line). Values above the upper bound are
greater than expected (i.e., enriched) based on the alu-
minum concentration measured in the sediment. This
"excess" metal is derived from additional sources other
than crustal background sediment, presumably, although
not necessarily, from anthropogenic activity. Regressions
for the remaining metals are presented in Appendix D.
While some of the metals, e.g., Ni, Cr, Se, Sb and the
crustally-derived elements Fe and Mn, are not highly
enriched, (the highest measured concentrations are
generally less than 2-3 times higher than the upper bound
of predicted concentrations) most metals are clearly
enriched at many stations. Two metals, Hg and Ag, are
found at a number of stations in concentrations more
than 10-60 times higher than predicted from the metal
aluminum relationship. The highest concentrations of
other metals (Pb, Sn, Cu, As, Cd and Zn) are generally
2-10 times higher than predicted. Often a given station
exhibits substantial enrichment of more than one metal.
The aerial extent of enriched metals concentrations in
sediments can be estimated once stations with enriched
metals concentrations are identified (Figure 3-31). For
several metals, the proportion of the Province in which
metals concentrations are enriched is substantial, e.g.,
Ag, Sn and Hg.
Approximately 41 ± 10% of the area of the Province
showed enrichment of sediments with at least one metal.
Thirty five (± 14), 53 ± 22, and 51 ±23 percent of the
large estuary, small estuary, and large tidal river class
areas sampled contained sediments with metals concentra-
Page 46
Statistical Summary, EMAP-E Virginian Province - 1991
-------
a) Large Estuaries
120
4 An
TOO '
S 80
1 60
S. 40
20
n •
i^^"
' .•''
t
1 1 1 1 1 1 1 1 1 I r
1000
2000
3000
4000
5000
b) Small Estuaries
-I 1 j ,_
2000 3000 4000
5000
c) Tidal Rivers
1000 2000 3000 4000
Acid Volatile Sulfides (mg/kg)
5000
Figure 3-29. Cumulative distribution functions of the AVS concentration in sediments by estuarine class: a) Large estuaries,
b) Small estuaries, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 47
-------
Table 3-8. Range and median metal concentrations in sediments of the Virginian Province, 1991.
Analyte
MIN
Concentration (pg/g dry weight)
MAX
Median
Median
Detection Limit3
Major
Aluminum
Iron
Manganese
Jrace
1,760
653
,11.6
89,300
54,500
6,430
42,800
21,700
368
na
na
na
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Silver
Tin
Zinc
ND
0.773
ND
1.88
0.492
ND
ND
ND
ND
ND
ND
3.66
49.1
34.9
6.58
174
263
323
1.96
70.1
1.76
9.69
27.0
484
0.299
5.36
0.187
39.0
15.3
27.6
0.052
16.5
0.364
0.048
2.24
74.5
0.050
na
0.031
na
na
1.79
0.004
1.68
0.111
0.007
0.116
na
8 For each "not detected" the laboratory supplied a detection limit. This value is the median of these values
for each analyte.
na = not applicable
ND = not detected
tions exceeding predicted background levels. Although
a significant proportion of the Province contains
sediments with potentially enriched levels of metals, this
does not imply ecological impacts.
The results obtained from the regression analyses
determined in this study should be similar to those
obtained by other investigators. Results of these
comparisons are described in Appendix D.
3.2.4 Marine Debris
Anthropogenic debris is perhaps the most obvious
sign of human use and environmental degradation. The
presence of anthropogenic debris in the field of view
or the inconvenience caused when it fouls a boat propeller
or fishing line can diminish the recreational value of
the estuarine environment. "Trash" is most likely to
be found in large tidal rivers and small estuaries where
human settlement and recreational activities are most
intense.
Page 48
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Cr
180 i
160
140
120
100
80
60
40 •
20-
0
0
4
AL (%)
Figure 3-30. Example linear regression (with upper 95%confidence intervals) of chromium against aluminum.
35 -,
30 -
2 25
<
"5 20 -
•£
CD
§ 15
0_
10 -
5 -
0
Ag As Cd Cr Cu Fe Hg Mn Ni Pb Sb Se Sn Zn
Figure 3-31. Percent area of the Virginian Province with enriched concentrations of individual metals in sediments
in 1991. (Error bars represent 95% confidence intervals).
The debris collected in bottom trawls was examined
as an indicator of environmental degradation in the Vir-
ginian Province. Debris was found on the bottom of
approximately 18 ± 8% of the Virginian Province area
sampled in 1991 (Figure 3-32). The small estuary class
had the largest percent area (35 ± 17%) where trash was
found. Trash was found in 12 ± 9% of the area of the
large estuaries and 16 ± 38% of the area of large tidal
rivers.
3.3 Habitat Indicators
Habitat indicators describe the natural physical and
chemical conditions of the sites sampled in the 1991 Vir-
ginian Province study.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 49
-------
80-]
70-
60-
§ 50-
o 40-
1 30-
0.
20-
10-
0
All
Large
Small
Tidal
Figure 3-32. The percent of area of the Virginian Province by
esluarine class where anthropogenic debris was collected in
fish trawls, 1991.
system. Such systems account for approximately 1.5%
of the area of small systems in the Virginian Province.
Overall, 9% of the area of the Province was deemed
unsampleable in 1991 due to water depth.
3.3.2 Temperature
Bottom water temperature in the Virginian Province
ranged from 16.2°C to 30.0°C during the summer
sampling period. The cumulative distribution function
of bottom temperature is shown in Figure 3-34. The
overall pattern is dominated by the CDF of the large
estuary class which shows inflections at 26.5°C and 22°C
(Figure 3-35a), representing the bottom temperature
characteristic of Chesapeake Bay and Long Island Sound,
respectively. The lowest bottom temperatures measured
in the Province occurred in Block Island Sound.
3.3.1 Water Depth
The depth distribution in the Virginian Province
is shown in Figure 3-33. The area shallower than 2 m
is underestimated because this is the minimum depth
sampled. Based on the sampling design where a single
station represents a given area, 12% of the area of large
estuaries was unsampleable due to inadequate water
depth. Small estuaries were considered unsampleable
if the water depth did not exceed 2 m. anywhere in the
Bottom temperature in the small estuaries ranged
from 20.7°C to 29.5°C (Figure 3-35b). More enclosed
small estuaries had warmer temperatures than might be
expected for their latitude. Large tidal rivers had a steep
CDF (Figure 3-35c) and, as a result, they exhibited the
smallest temperature range (24.6°C to 30.0°C). The three
warmest stations in the Province were found in the upper
Potomac River, which is surrounded by the Washington
DC metropolitan area. Approximately 18 ±40% of the
area of the large tidal river class and 2 ± 4% of the
Province area had a bottom temperature above 29°C.
120 T
Depth (m)
Figure 3-33. Cumulative distribution of water depth as a percent of area in the Virginian Province, 1991. (Dashed lines are the
95% confidence intervals).
Page 50
Statistical Summary, EMAP-E Virginian Province - 1991
-------
120 T
16 18 20 22 24 26
Temperature (° C)
28
30
32
Figure 3-34. Cumulative distribution of bottom temperature as a percent of area in the Virginian Province,-1991. (Dashed lines
are the 95% confidence intervals).
3.3.3 Salinity
Salinity is determined by freshwater discharge and
seawater intrusion. Salinity in the broad sounds of the
northern Province is, in general, higher than salinity in
the coastal plain estuaries south of the Hudson River.
The CDF for bottom salinity (Figure 3-36) reflects the
different salinity characteristics of the large estuarine
systems. Chesapeake Bay accounts for the inflection
at 17%c while Long Island Sound is responsible for the
one at 28%o.
The CDF for small estuaries (Figure 3-37) is
dominated by small systems in the Chesapeake Bay
which account for most of the area between 12 and
20%o. The low salinity tail of the CDF is due to the
contribution of small river systems, whereas the high
salinity component is due to embayments supplied with
high salinity waters from the northern sounds. The range
of salinities was greatest in small estuaries (0 to 32 %o),
with the ranges for large estuaries and large tidal rivers
being 9 to 32 and 0 to 15 %o, respectively (Figure 3-37).
The 1991 data showed over 30 ± 12% of the large
tidal river area to be fresh water (salinity < 0.5%0).
Large tidal rivers contain the largest tidal fresh/oligo-
ha'line area (45 ± 19% < 5 %c) compared to 11 ± 10%
for small estuaries and 0% for the large estuaries (Figure
3-38).
3.3.4 pH
The negative log of the hydrogen ion concentration,
or pH, of estuarine and coastal waters, similar to salinity,
depends on the mixing of sea water and fresh water from
land drainage. Sea water is well-buffered with its pH
usually falling between 8.1 and 8.4. The pH of fresh
water runoff depends upon the characteristics of the land
drained and can be quite variable.
The measured pH of Virginian Province estuaries
ranged from 6.8 to 8.6, with 67 ± 11% of the Province
area between pH 7.7 and 8.2. The lowest pH values
occurred in large tidal rivers, upper Chesapeake Bay,
and in small estuaries associated with tidal rivers or other
fresh water inflows. High pH values were generally
associated with sea water inflow; however, some of the
highest pH values were found in the fresh water portions
of the Hudson and Potomac Rivers.
3.3.5 Stratification
Vertical density differences, or stratification, if large
enough, can result in a reduction of mixing between
surface and bottom waters, potentially allowing the
bottom waters to become hypoxic. Stratification may
also create conditions that enhance phytoplankton growth,
Statistical Summary, EMAP-E Virginian Province - 1991
Page 51
-------
120 T
a) Large Estuaries
b) Small Estuaries
20 22 24 26
140 T
c) Tidal Rivers
16 18 20 22 24 26
Temperature (° C)
28 30
32
Figure 3-35. Cumulative distribution functions of bottom temperature by estuarine class: a) Large estuaries, b) Small estuaries,
c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Page 52
Statistical Summary, EMAP-E Virginian Province -
-------
120 T
0
10
15 20
Salinity (%o)
25
30
35
Figure 3-36. The cumulative distribution of bottom salinity as a percent of area in the Virginian Province, 1991. (Dashed lines
are the 95% confidence intervals).
which might ultimately result in increased biomass
settling to the bottom contributing an additional
biological oxygen demand in the stratified environment.
Fresh water runoff can be an important factor in this
process because it both provides low density water to
maintain stratification and often carries high nutrient
concentrations which support plant growth. Stratifica-
tion may also be caused by warming of the surface
waters, especially where salinity is uniform. The
development of stratification depends not only on the
magnitude of the density difference between surface and
bottom waters, but also on the depth of those waters and
the physical energy available for mixing.
Stratification in the Virginian Province is shown as
a CDF of Aat, which is the 0, (sigma-t density) differ-
ence between surface and bottom waters (Figure 3-39).
Sigma-t is a density measurement commonly used in
oceanographic studies. It is a measurement of the
density a parcel of water with a given temperature and
salinity would have at the surface (i.e., atmospheric
pressure), and is presented as:
(density - 1) x 1000
The CDF for all estuaries shows that 76 ± 10% of
the Province area had a Aot of <1 kg/m3, with 52 ±11%
being <0.2; thus the majority of the water in the Virginian
Province was well-mixed. Only 7 + 7% of the Province
area was stratified (Aat >2). The bar chart for stratifica-
tion by class (Figure 3-40) show that small estuaries were
least stratified (0% with Aa, >2) and the best mixed (96
± 4% with Aot <1.0). Large estuaries had the greatest
range of Aat (0 to 6).
3.3.6 Suspended Solids
The amount of suspended matter in the water is
dependent on the physical and biological conditions at
the site. Both the concentration and composition (i.e.,
size distribution and organic vs inorganic origin) of
suspended material affects light extinction and water
clarity; and thus the productive and aesthetic qualities
of the water.
The data presented in this section represent surface
values only. Suspended solids concentrations in the
waters of the Virginian Province ranged from 3.2 to 78.1
mg/L in 1991 (Figure 3-41). The relative condition of
Virginian Province waters in large estuary, small estuary,
and large tidal river classes, are similar (Figure 3-42).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 53
-------
a) Large Estuaries
120 T
100
b) Small Estuaries
10 15
c) Tidal Rivers
140
120 •
« 100 -
£
5 80
I 60 -
<5
°- 40-
20
0
10
15 20
Salinity (%„)
25
30
35
Figure 3-37. Cumulative distribution functions of bottom salinity by estuarine class, (a) Large estuaries, (b) Small estuaries.
(c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Page 54
Statistical Summary, EMAP-E Virginian Province - 1991
-------
CO
CD
c
CO
2
CD
Q.
Oligohaline
Mesohaline
Polyhaline
20
Large
Small
Tidal
Figure 3-38. The percent of area by estuarine class classified as Oligohaline (<5 ppt), mesohaline (5 to 18
ppt), and polyhaline (>18 ppt). (Error bars represent 95% confidence intervals).
0
2 3
A0 (kg/m3)
4
Figure 3-39. Cumulative distribution function of the stratified area in the Virginian Province in 1991 based on the sigma-t
density difference between surface and bottom waters. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 55
-------
12Ch
too-
80-i
o
•£ 60H
1
ix 40-
20-
0
I
Qtot
1 to 2
2+
All Large Small Tidal
Figure 3-40. The percent of the area by estuarine class that had a low (<1), medium (1 to 2), or high (>2)
degree of stratification (A a, in kg/m3). (Error bars represent 95% confidence intervals).
120 T
10 20 30 40 50 60
Suspended Solids (mg/L)
70
80
Figure 3-41. The cumulative distribution of total suspended solids concentration as a percent of area in the Virginian Province,
1991. (Dashed lines are the 95% confidence intervals).
Page 56
Statistical Summary, EMAP-E Virginian Province - 1991
-------
a) Large Estuaries
120-•
100-
§80 +
S. 40-
20-
0
0
10 20 30 40 50 60 70 80
b) Small Estuaries
10 20 30 40 50 60 70 80
c) Tidal Rivers
20 30 40 50 60
Suspended Solids (mg/L)
70
80
Figure 3-42. Cumulative distribution functions of total suspended solids concentration by estuarine class: a) Large estuaries,
b) Small estuaries, c) Large tidal rivers. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 57
-------
3.3.7 Light Extinction
The light extinction coefficient is a measure of the
attenuation of sunlight in the sea. It is the natural
logarithm of the ratio of the intensity of light of
specified wavelength on a horizontal surface to the
intensity of the same wavelength light on a horizontal
surface I m deeper. The extinction coefficient of
photosynthetically active radiation (PAR) was calculated
from depth and PAR measurements made with the
SeaBird CTD. The extinction coefficient is an important
measure of the light available for photosynthesis and
of the aesthetic qualities of the water for human use.
We are defining low water clarity as water in which
a diver would not be able to see his/her hand when held
at arms length. This corresponds to an attenuation
coefficient £2.303 which is equivalent to the transmis-
sion of 10% of the light incident on the surface to a
depth of 1 m. Moderate water clarity corresponds to
an extinction coefficient of £1.387 which is equivalent
to the transmission of 25% of the light incident on the
water surface to a depth of 1 m. In terms of human
vision, a wader in water of moderate clarity would not
be able to see his/her feet in waist deep water.
Water clarity was good in 80 ± 7% of the sampled
area of the Virginian Province (Figure 3-43). Water of
low clarity was found in 8 ± 6% of the Province and
an additional 12 ± 7% of the Province had water of
moderate clarity. Thus, in 20 ± 7% of the waters in the
Virginian Province waders would not be able to see their
toes in waist deep water. Water of low clarity was found
in 4 ± 6% of the large estuarine area, 16 ± 15% of the
small estuarine area, and in 20 ± 37% of the large tidal
river area (Figure 3-44). These differences in water
clarity may be due to fundamental differences in the
dynamic properties of the classes as well as differences
in the intensity of human use. Large estuaries had the
greatest percent area of high water clarity (92 ± 8%)
and large tidal rivers the least (27 ±31%).
3.3.8 Percent Silt-Clay Content
The silt-clay (mud) content of sediments (the fraction
<63u) is an important factor determining the composition
of the biological community at a site; and is therefore,
important in the assessment of the benthic community.
Percent mud is also useful when examining sediment
chemistry data because the available surface area for
sorption of contaminants is partially a function of grain
size, with fine-grained sediments (i.e., mud) generally
being more susceptible to contamination than sands
exposed to the same overlying water.
All silt-clay results presented in this report are for
the surficial sediments (0-2 cm) collected as part of the
chemistry /toxicity homogenate.
120 T
01 2 345
Light Extinction Coefficient
Figure 3-43. The cumulative distribution of light extinction coefficient as a percent of area in the Virginian Province in 1991.
(Dashed lines are the 95% confidence intervals).
Page 58
Statistical Summary, EMAP-E Virginian Province - 1991
-------
110-
100-
90-
(8
£ BO-
'S 70-
I 60-
I 50-
40-
30-
20-
10-
0
12 Low
H Moderate
& Good
All
Large
Small Tidal
Figure 3-44. The percent of area by estuarine class where water
clarity was poor, moderate,,or good. (Error bars represent 95%
confidence intervals).
Sediment size distribution is primarily a result
of the different physical characteristics of the
separate system classes. For example, small
systems are often estuaries, bays, tidal creeks and
rivers with low flow rates, which result in high
deposition rates of fine-grained material. The
large area of sandy sediments found in the large
estuaries of the Virginian Province are most likely
the result of either the winnowing of sediments
or the transport of marine sands. The mouth of
the Chesapeake Bay is an example of the latter
where sands are carried in from the ocean (Hobbs
et al., 1992). Long Island Sound is an example
of a system where the coarser sediments at the
entrance are mainly a result of strong tidal
currents transporting away the fine fraction
(winnowing), leaving behind the coarser sands
and gravel (Akapati, 1974; Gordon, 1980).
The CDF, o'f silt-clay content for the Virginian
Province is shown in Figure 3-45. Forty-six (± 11)
percent of the area had sandy sediments (<20% silt-
clay), and 31 ± 9% of the area had muddy sediments
(>80% silt-clay). The sediment size distribution in large
estuaries was dominated by sands, whereas small
estuaries and large tidal rivers were dominated by muds
(Figure 3-46).
3.4 Integration of Estuarine Conditions
The condition of estuaries of the Virginian Province
can be estimated through the examination of multiple
indicators. As an example, we have integrated data on
stations that can be considered "degraded" based on water
clarity, the presence of anthropogenic trash caught in
fish trawls, and the benthic index. The summation of
these indicators was used as an indicator of the maximum
120 T
20
40 60
Silt / Clay (%)
100
Figure 3-45. The cumulative distribution of the percentage of silt-clay in the sediments as a percent of area in the Virginian
Province, 1991. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page 59
-------
80
g 60
I 40
<£
20
<20
20 to 80
>so
Alt
Large
Small
Tidal
Figure 3-46. The percent of area by estuarine class with a low (<20),
medium (20 to 80), or high (>80) percent silt-clay in the sediments.
(Error bars represent 95% confidence intervals).
extent of potential degradation. Figure 3-47 shows that,
in this example, 36% of the Province is potentially de-
graded in terms of its benthic biology and ability to
support desired human commercial or recreational uses.
Aesthetic value (water clarity and presence of trash) was
degraded in 25% of this area, whereas 14% of the area
may be degraded as a result of subnominal benthic
communities.
There was only a 3% overlap between areas
which were biologically degraded (low benthic
index values) and those that were aesthetically
degraded. Poor water clarity may dictate impair-
ment of some human uses, but it is probably not
a good indicator of ecological degradation;
therefore, the area of the Virginian Province that
is, in fact, degraded is probably much less than
indicated in this example.
This evaluation is intended solely as an
example of how these data may be used. To truly
estimate the percent area degraded, all response,
exposure indicators, and aesthetic indicators
should be included. Due to the current state of
understanding of sediment geochemistry and its
relationship with the biota, such ah exercise could
not be undertaken at this time.
1%
64%
15%
Poor do-ity
Poor dcrlty & Subnomind Benthos
Subnorrtnd Benthos
Trcsh & Subnornlnd Benthos
Trcsh Present
Acceptable Conation
Figure 3-47. Integration of estuarine conditions based on presence of bottom trash, water clarity, and the benthic index.
Page 60
Statistical Summary, EMAP-E Virginian Province - 1991
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SECTION 4
QUALITY ASSURANCE
The 1991 Virginian Province monitoring effort was
implemented using a quality assurance program to
ensure comparability of data with those collected in
other EMAP-E provinces, and to assure data quality
consistent with the goals of the Program. As described
in the Quality Assurance Project Plan (Valente and
Schoenherr, 1991), Measurement Quality Objectives
(MQOs) were established for data quality. Quality
control steps taken to assure that MQOs were met
included intensive training of field and laboratory
personnel, field performance reviews of sampling crews,
laboratory certification and audits.
4.1 CREW TRAINING
One of the most critical components of the EMAP-
VP QA Program was the thorough training of field
personnel. Training was divided into two distinct
courses: Crew chief training and crew training.
Crew chiefs underwent detailed training during the
first two weeks of June, 1991. Training was limited to
two weeks because all but one of six crew chiefs were
a returnee from the previous year. This training was
conducted at the U.S. EPA Environmental Research
Laboratory-Narragansett, RI (ERL-N) and focused
mainly on the sampling methods, with emphasis placed
on the electronic measurements and the computer
system. Crew chief training was conducted by SAIC
and CSC (Computer Sciences Corporation) personnel
with oversight by EPA ERL-N staff.
Crew training was held from 17 June to 19 July
1991. Both safety and sampling methods were impor-
tant components of training. Crew training was broken
into two phases: formal training which lasted for
approximately 2-l/2 weeks, and one week .(per crew) of
dry runs.
Dry runs consisted of four days in the field during
which crews operated as they would during the sampling
season. They were assigned four stations to monitor
for all parameters, including DataSonde deployment and
retrieval. Crews members stayed in motels, prepared
samples for shipment, entered data into the field
computer, and electronically transmitted all data to the
Field Operations Center (FOC) just as they would during
actual field operations. In addition, the Field Coordinator
or the QA Coordinator visited each crew during dry runs,
completing a performance review sheet to determine the
crew's overall grasp of the program. All crews were
deemed properly prepared to begin sampling activities
on 22 July, 1991.
Certification examinations for crew chiefs and field
crew members were administered at the end of each
course and proved to be very useful. As a result of
testing, two crew chiefs were identified as needing
additional training. This coaching was provided and
they were fully competent by the start of crew training.
The examination administered at the end of crew training
suggested some areas, such as contingencies for moving
stations, were not adequately covered, so additional time
was spent discussing these topics prior to dry runs.
Statistical Summary, EMAP-E Virginian .Province - 1991
Page 61
-------
4.2 FIELD DATA AND SAMPLE
COLLECTION - QUALITY
CONTROL CHECKS
Several measures were taken during the 1991 field
season to assure the quality of the data collected. These
consisted of QC checks, the collection of QC samples,
and performance reviews by senior Program personnel
(QA Coordinator or Field Coordinator).
4.2.1 Water Quality Measurements
Generally the first activity performed at each station
was to obtain a vertical profile of the water column for
key parameters. The instrument chosen for this
operation was the SeaBird SBE 25 SeaLogger CTD.
This instrument is generally regarded as a very sensitive,
accurate and reliable device. All CTDs were calibrated
according to manufacturers instructions at the EMAP-VP
calibration facility just before the field season began.
The procedures for calibration and checks are described
in the 1991 Quality Assurance Project Plan (Valente and
Schoenherr, 1991).
Field QC checks on the performance of the CTD
fell into two categories: daily and weekly. The daily
check consisted of taking duplicate bottom measure-
ments with a YSI Model 58 dissolved oxygen meter
(instrument air calibrated at each station), a refractome-
ter (salinity), and thermometer (temperature) at every
station. Acceptable differences are listed in Valente and
Schoenherr (1991). It is worth noting that the salinity
values produced by the CTD are expected to be much
more accurate than those from the refractometer, and
are more accurate than is required by EMAP. The
refractometer only provided a "gross" check to deter-
mine if there was an electrical problem with the CTD's
conductivity sensor; it provided no information about
gradual drift. If the instrument "failed" QC, the cast
was repeated. If it failed on the second attempt, the cast
was saved but flagged. Of the 134 casts for which
separate dissolved oxygen measurements were success-
fully obtained with the YSI meter, 98.5% "passed" QC,
showing differences of ^ 1 mg/L. Eighty six percent
of the bottom CTD DO values differed from the YSI
by 5 0.5 mg/L. All temperatures and salinities passed
QC.
In addition to the daily checks, a more thorough
weekly (once per 6-day shift) check was also performed.
First, a bucket of water was bubbled with air for at least
two hours to reach saturation for dissolved oxygen. The
YSI meter was air calibrated according to manufacturer's
instructions, and the dissolved oxygen concentration of
the water determined. At the same time multiple water
samples were drawn off for Winkler titration using a
,Hach digital titrator. The YSI value was compared to
the concentration determined by titration. Since the YSI
meter was calibrated prior to each use, this served as
a check on the validity of the air calibration method.
Following this check of the YSI meter, the CTD was
immersed in water and the DO, temperature, and salinity
compared with values obtained from the YSI, thermome-
ter, and refractometer respectively. The unit was brought
back on the deck and the pH probe immersed in a pH
10 standard for comparison (pH 10 was used instead of
pH 7 because the instrument defaults to a reading of 7
when malfunctioning). If the unit failed for any variable
it was returned to the Field Operations Center for
recalibration. A total of 27 checks were performed during
the field season, with all meeting the criteria for
acceptance, and only 3 of the 27 resulting in dissolved
oxygen differences of more than 0.5 mg/L.
In addition to the CTD cast, Hydrolab DataSonde
3 dataloggers were deployed at all Base Sampling Sites
to collect continuous dissolved oxygen data. Each unit
was calibrated and checked prior to deployment as
described in the 1991 Virginian Province Field Operations
and Safety Manual (Strobel and Schimmel, 1991b). Upon
retrieval an additional check was performed; immersing
the DataSonde in a bucket of water and comparing the
dissolved oxygen, salinity, and temperature values to
a YSI Model 58 DO meter, refractometer, and thermome-
ter respectively. Salinity and temperature passed QC
in all cases. Of the 105 successful retrievals, 98 (93%)
met the acceptability criteria for DO (1 mg/L). Seventy
nine percent showed differences of 0.5 mg/L or less.
Differences between the DO values were generally
attributed to fouling of the DataSonde 3's DO probe.
4.2.2 Benthic Indicators
As described in Section 3, several different benthic
samples were obtained at each station. Three samples
were processed for benthic community structure and
biomass determination. v
Page 62
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Crews were observed closely during field perfor-
mance reviews to ensure that standard protocols were
being followed for all benthic sampling. Laboratory QA
measures are described below in Section 4.3.
In addition to the infaunal samples, sediment was
collected for chemical analysis, toxicity testing, and
grain size determination. Additional QC samples were
collected for chemistry at one station per crew. A
second duplicate sample was removed from the
homogenate, and a "blank" bottle was left open
whenever the sample was exposed to the atmosphere.
The purpose of the blank was to determine if atmo-
spheric contamination was a significant problem.
Additional analytical measures are described in Section
4.4. Grain size and toxicity QA results are discussed
in Section 4.3.
4.2.3 Fish Indicators
The two fish indicators for which field data, as
opposed to samples, were collected were fish community
structure and gross external pathology. The QA Project
Plan (Valente and Schoenherr, 1991) called for QA
samples to be collected for both of these indicators.
To verify each crew's ability to correctly identify
fish species for the community structure indicator, the
first individual of each species collected by each crew
was shipped to ERL-N or Versar for verification by an
expert taxonomist.
Three types of errors were detected: misspelled or
incomplete species names (in the database), misidentifi-
cations, and fish that could not be identified in the field.
Errors falling into the first category were easily
detected, corrected in the database, and documented.
An example of this type of error can be found looking
at the "Atlantic tomcod". Records were received from
the field for "Atlantic tomcod", "tomcod", and "torn
cod" (two words). Each was listed by the computer as
separate species.
The second type of error was mis-identifications.
Of the 187 fish sent in for taxonomic verification, 14
were misidentified, representing 9 species. In all cases
the crew identified a closely-related species, such as
longspine porgy instead of scup, brown bullhead catfish
instead of the yellow bullhead, and lizardfish instead
of inshore lizardfish. An additional 14 individuals (5
species) were sent in as unknowns or partial unknowns
(e.g., herring uncl.).
The total of 28 incomplete identifications or
misidentifications represent 51 fish records in the database
(including other fish of the same species caught in the
same trawl). A total of 7,134 fish were collected in
standard trawls during the 1991 field season representing
69 species. The percentage of errors detected was
therefore less than one percent.
Crews examined all individuals of the 10 target
species collected for evidence of gross external
pathologies. To verify each crew's ability to properly
identify pathologies, fish identified as having an external
pathology by the field crews were shipped to ERL-N
for verification by the laboratory's pathologist. This
provided an estimate of the percentage of "false
positives". In addition, in order to develop an estimate
of the rate of "false negatives" (i.e., number of patholo-
gies missed, therefore never sent in for verification),
crews collected and shipped up to 25 individuals of each
target species (which they determined to be free from
external pathologies) caught at Indicator Testing and
Evaluation stations.
Results of laboratory examinations reveal that the
crews were generally conservative, classifying "border-
line" conditions as pathologies so the fish would be
examined by an expert rather than being discarded. Of
the 12 fish sent in for verification of a pathology (four
additional fish were not shipped), only five were verified
by the pathologist. Of the 183 "reference" fish shipped,
the pathologist determined that four did have a pathology,
but in all cases the pathology was some form of discolor-
ation which is difficult for a novice to determine. Fin
erosion was not included in these statistics as damage
was incurred due to the method of shipping fish
(packaged in mesh onion bags) prohibiting accurate
examinations by the laboratory staff.
4.2.4 Field Performance Reviews
In adition to the crew certification visits performed
during dry runs, each crew was visited by a senior EMAP
staff member during field operations. All aspects of
sampling, from boat operations to shipping, were observed
by the reviewer. Some of the activities included
Statistical Summary, EMAP-E Virginian Province - 1991
Page 63
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confirming the presence/ absence of external patholo-
gies, re-measuring fish and apparent RPD (Redox
Potential Discontinuity) depth, assuring that all
precautions were taken to avoid contamination of the
chemistry samples, assuring proper processing of benthic
infauna samples, observing data entry, and assuring that
all necessary safety precautions were observed. The
reviewer used a "field review check-off sheet" to
provide guidance during the review, and to document
the crew's performance. Both reviewers concluded that
the crews were sufficiently concerned with all QA
issues, and that the data generated were representative
of ambient conditions.
The only problem noted was the determination of
the depth of the apparent Redox Potential Discontinuity
(RPD). This measurement was determined to be too
subjective, variable, and difficult to accurately measure
based on a visual inspection of a clear plexiglass core
taken from a grab sample. Although reasonable
measurements could be made in muddy sands, the
majority of the sediments encountered by field crews
were fine grained muds where adhesion to the plexiglass
core creates too much smearing to allow for an accurate
measurement. Therefore, RPD data are not reported in
this document and will not be used in the assessment
of condition of the Province.
4.3 LABORATORY TESTING AND
ANALYSIS
Quality control requirements for laboratory testing
and sample analysis are covered in detail in the 1991
EMAP-VP QA Project Plan (Valente and Schoenherr,
1991) and the EMAP-E Laboratory Methods Manual
(U.S. EPA, 1991) and will not be reiterated here. All
laboratories were required to perform QA activities, and
the results of those activities will be discussed in this
report. Because of the complexity of chemical analyses,
QA results for those analyses are listed separately in
Section 4.4.
4.3.1 Sediment Toxicity Testing
AH sediment toxicity testing was performed at the
SAIC Environmental Testing Center (ETC) in
Narragansett, RI. Certification of the ETC occurred in
1990 and those results will not be discussed here, with
the exception of stating that the laboratory successfully
met EMAP requirements.
As per the QA Project Plan, the laboratory was
required to maintain a control chart for toxicity testing
using a reference toxicant. The ETC used SDS (sodium
dodecyl sulfate) as their reference material, running a
standard 48-hour water-only toxicity test with SDS
whenever EMAP samples were run. The control chart
shows that the LC50 for SDS ranged from 4.0 to 8.37
mg/L, with all values falling within two standard
deviations of the mean as required in the QA Plan. In
addition to maintaining a control chart and making it
available for review at any time, a QA audit of the facility
was performed in September, 1991. The results of the
audit showed the staff at the ETC to be cognizant of all
QA concerns, and that no remedial action was required.
Several tests failed to meet EMAP QA requirements
for control organism survival. Of the 19 tests run, three
exhibited control organism survival less than the required
85% (this was following repeating all tests that failed
on the first attempt). These tests were "flagged" in the
database and were not included in the data set utilized
to generate this statistical summary.
4.3.2 Grain Size Analysis
All "sediment grain size" and at least one "benthic
grain size" sample per station were analyzed for the
determination of percent silt/clay. Approximately 10%
of these analyses were performed in duplicate and the
Relative Percent Difference determined as per the EMAP-
E Laboratory Methods Manual (U.S. EPA, 1991). The
maximum allowable percent difference for the predomi-
nant fraction (silt/clay or sand) is 10%. The mean
difference for the samples analyzed was less than 1%,
with none exceeding 10% so no remedial action or
retesting was required.
4.3.3 Benthic Infauna Analysis
Two QA steps were required by the EMAP-VP 1991
QA Project Plan: 10% recounts and independent
verification of species identification. The recounts
(multiple types - see Table 4-1) and preliminary species
verification were performed by the laboratory performing
the analyses. All of these met the requirements
established in the QA Plan. Definitive verification of
species identification was performed by an independent
laboratory and the results afe described below.
Page 64
Statistical Summary, EMAP-E Virginian Province - 1991
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Table 4-1. Results of recounts performed by the laboratory processing benthic infauna samples. Approximately
10% of all samples were processed in duplicate.
Measurement
Benthic sorting
Species identification and enumeration
Biomass
Weighing blanks for biomass
Mean Error
4.5%
2.4%
0.13%
0.0001 g
Range of Error
0
0
0
0
- 20.5%
- 14%
- 1.6%
- 0.0023g
A total of 137 specimens collected from oligohaline
stations were sent to the Aquatic Resources Center in
Franklin, TN for independent taxonomic verification.
Eleven (8%) were mis-identified, representing 8 species.
The identification of an additional 15 specimens could
not be confirmed because of the condition of the
specimen (i.e., key taxonomic features missing or
destroyed, or male needed for identification and only
females sent).
The identification of many of these species is
difficult. Misidentified species were closely related
taxonomically to the "true" species. In general, the
report on species verification was "largely favorable"
indicating the analytical laboratory performed well.
Suggestions will be made regarding identification of
tubificid oligochaetes and molluscs prior to the next
season.
4.4 LABORATORY CERTIFICATION
AND CHEMICAL ANALYSIS
EMAP-E requires that analytical laboratories partici-
pate in an extensive certification process prior to the
analysis of any EMAP-E chemistry samples. This
certification is in addition to normal quality control
measures that are required during analysis to ensure
quality data (i.e., blanks, spikes, controls, duplicates,
etc.). Standard Reference Materials (SRMs) with known
or certified values for metals and organic compounds
were used by the Virginian Province laboratories
conducting analyses to confirm the accuracy and
precision of their analyses. Many of the SRMs used
extensively in the EMAP-E program are naturally-
occurring materials (e.g., marine sediments or oyster
tissue) in which the analytes of interest are present at
levels that are environmentally realistic, and for which
analyte concentrations are known with reasonable
certainty. The certification results for the laboratory
conducting the sediment analyses can be found in Table
4-2. Fish certification results are presented in Table 4-3.
The 1991 Virginian Province QA Project Plan
(Valente and Schoenherr, 1991) lists warning and control
limit criteria for the analysis of Certified (or Standard)
Reference Materials. The more conservative warning
limit for all organics is stated to be "Lab's value should
be within ± 25% of true value on average for all analytes;
not to exceed ± 30% of true value for more than 30%
of individual analytes for each batch". Both laboratories'
performance during certification resulted in permission
being granted for the analysis of samples to begin.
During sample analysis, the laboratory was required
to analyze a Laboratory Control Material (LCM) with
each batch of samples being analyzed. An LCM is
identical to an SRM with the exception that the true val-
ues need not be certified by an external agency (however,
in these cases the same SRMs used during certification
were used as the LCM). In addition to the LCM, dupli-
cate "matrix-spiked" samples were required for each
batch.
In addition to the analysis of the required QA data,
summary data have been reviewed by an environmental
chemist to verify that they are "reasonable" based on
past studies and known distributions of contaminants
in East Coast estuaries. This included examining the
ratios of individual congeners (i.e., PCBs); and PAH
and DDT analytes. Any data that were deemed
"questionable" were flagged for further study.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 65
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Table 4-2. Results of certification analysis for sediment contaminants performed by EMSL-Cinn. The Reference
Material for the organics certification was NIST SRM 1941. The SRM for inorganics was the National
Research Council of Canada BCSS-1 CRM. For organic analyses, only those analytes with certified
values at least 10x the detection limit are included.
Analyte
Inorganics (ug/g dry weight)
Al
As
Cd
Cr
Cu
Fa
Mn
Ni
Pb
Sb
So
Sn
Zn
Certified
Concentration
62700 ±21 73
11.1 ± 1.4
0.25 ± 0.04
123 ± 14
18.5 ±2.7
32900 ± 980
229 ± 15
55.3 ± 3.6
22.7 ± 3.4
0.59 ± 0.06
0.43 ± 0.06
1.85 ±0.20
119±12
Measured
Concentration
58,600
11.0
0.20
81.3
18.4
29,800
199
47.0
27.8
0.56
0.42
2.24
96.4
QraaoicsJPCBs/pesticides - na/a drv weiahti
PCB18
PCB28
PCB52
PCB66
PCB 101
PCB118
PCB 153
PCB 187
PCB 180
PCB 170
PCB 206
PCB 209
4,4' DDE
4,4' ODD
4,4' DDT
9.90 ± 0.251
16.1 ±0.41
10.4± 0.41
22.4 ± 0.71
22.0 ± 0.71
" 15.2±0.71
22.0±1.41
12.5±0.61
14.3±0.31
7.29 ± 0.261
4.81 ± 0.151
8.35 ± 0.21 1
9.71 ±0.171
10.3 ±0.11
1.11 ±0.051
2.82
12.8
11.6
20.4
15.1
16.2
14.5
7.50
13.2
4.95
3.11
6.49
8.43
8.24
1.47
(continued)
Page 66
Statistical Summary, EMAP-E Virginian Province - 1991
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Table 4-2 continued.
Analyte
Certified
Concentration
Measured
Concentration
Organics (PAHs - ng/g dry weight)
Phenanthrene 577 ± 59
Anthracene 202 ± 42
Fluoranthene 1220 ± 240
Pyrene 1080 ±200
Benz(a)anthracene 550 ± 79
Benzo (b & k) fluoranthene 1224 ±239
Benzo(a)pyrene 670 ±130
Perylene 422 ± 33
ldeno(1,2,3-cd)pyrene 569 ± 40
Benzo(g,h,i)perylene 516 ±83
Naphthalene 1322 ±141
2-MethylnaphthaIene 406 ± 361
1-Methylnaphthalene 229 ± 191
Biphenyl / 115±151
2,6-Dimethyjnaphthalene 198 ± 231
Fluorene 104±51
Benzo(e)pyrene 5731
Chrysene 4491
535
170
1100
1020
572
983
494
252
609
526
722
355
191
94
203
101
579
709
1 Value provided by NIST but not considered a "certified" value, meaning the values were determined via a
single method. Despite not being certified, these values are still considered accurate.
As stated earlier, at each sediment chemistry QA
station crews opened a "blank" bottle whenever the
sample was exposed to the atmosphere. The analytical
laboratory solvent rinsed this bottle and then analyzed
the solvent for contamination. Results showed no evi-
dence of contamination, which if present, could have
come from either the field or the laboratory.
4.5 DATA MANAGEMENT
•To expedite the process of data reporting, all field
data were entered into field computers and transmitted
electronically to the Information Management Center.
Upon receipt of the "hard copy" data sheets, a 100%
check was performed by the EMAP data librarian (i.e.,
every record in the computer was manually compared
to the data sheet). Following, corrections, a different
individual then performed a second 100% check. A third
check (20%) was then performed by a third person. By
the completion of this exercise we were confident that
the computer data base accurately reflected what the crew
reported.
The number of data errors detected can be classified
as "record" errors or "value" errors. A value refers to
a single observation recorded as part of a record. A
record refers to an entire set composed of "n" values,
such as a data sheet. Record errors generally refer to
duplicate or missing data sheets. Duplicate electronic
data sheets can result from the crew accidentally saving
the same page twice, but with different page numbers.
Value errors refer to missing or incorrect values recorded
on a data sheet.
Statistical Summary, EMAP-E Virginian Province - 1991
Page 67
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Table 4-3. Results of certification analysis for fish contaminants performed by Texas A&M University. The
Reference Material for the organics certification was NIST SRM 1974. The SRM for inorganics was
the NIST SRM 1566a.
Analyte
Inorganics (\ig/g dry weight)
Al
As
Cd
Cr
Cu
Fe
Ni
Pb
Se
Sn
Zn
Certified
Concentration
202.5
14.0
4.15
1.43
66.3
539
2.25
0.371
2.21
31
830
Measured
Concentration
181.0
13.1
4.02
1.49
63.6
533
2.25
0.36
2.20
2.22
807
Organfcs (PCBs/pesticldes - ng/g dry weight)
PCB18 24±91 20.9
PCS 28 62±31 85.2
PCS 44 65 ± 231 72.4
PCB52 98 ± 391 113.7
PCB66 110±51 98.7
PCB101 105 ±111 127.0
PCB 105 ' • 45 ± 31 46.9
PCB118 , 110±51 115.9
PCB 128 15±21 17.3
PCB 138 110 ±111 122.2
PCB 153 145 ±81 153.9
PCB 180 13±11 13.3
PCB 187 30±11 27.2
1 Value provided by NIST but not considered a "certified" value, meaning the values were determined via a
single method. Despite not being certified, these values are still considered accurate.
Page 68 Statistical Summary, EMAP-E Virginian Province - 1991
-------
Results of the checks described above showed a
value error rate of <3%. The rate of record errors was
approximately 10%, with most of these (76%) being
from the fish data set. The major problem with the field
computer system used in 1991 was the difficulty of
entering and editing fish data. This resulted in the
relatively large number of record errors (missing or
duplicate records). This component of the field system
was significantly modified for 1992 to reduce the error
rate.
The next step in data QA was data verification and
validation. Verification was another step in assuring
that the data were correct (e.g., assuring that each CTD
cast was associated with the correct station). Validation
was the process of checking to make sure all data were
reasonable (e.g., making sure that fish lengths were all
entered in mm, not cm). These processes were exten-
sive; therefore, only a few examples will be provided
here.
Part of the process of verifying CTD dissolved oxy-
gen profiles was to compare cast depth to water depth,
and the bottom DO value with the closest (in time)
Hydrolab DataSonde value. If they were significantly
different, the cast was flagged for additional investiga-
tion. Validation then consisted of an expert examining
every cast to assure the DO values were realistic and
that the profile appeared reasonable.
One of the steps in validation of the fish community
data set was to compare each fish length to the reported
size range for that species. Geographic distributions
were also examined to determine if the species had
previously been reported where EMAP crews found
them.
4.6 REPORTING
To ensure the data summaries presented in this docu-
ment accurately reflect the data, the analyses were
validated by duplication. Two separate analysts devel-
oped the cumulative distribution functions reported in
Section 3. The two analysts worked from the same data
base but developed the analysis programs separately for
two indicators. In both instances the resulting estimates
matched one another. Bar charts were checked in a
similar fashion. Such checks were deemed necessary
because of the complexity of the calculation of percent
area and 95% confidence intervals.
Statistical Summary, EMAP-E Virginian Province - 1991 Page 69
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SECTION 5
SUMMARY OF FINDINGS
Thousands of pieces of information on the condition
of cstuarine resources in the Virginian Province in 1991
were collected and analyzed. The major findings of the
1991 study year are highlighted in this section.
5.1 Virginian Province Fact Summary
• The Virginian Province includes the coastal
region of the Northeast United States from Cape
Cod south to the mouth of Chesapeake Bay.
It is composed of 23,574 km2 of estuarine
resources including 11,469 km2 in Chesapeake
Bay and 3,344 km2 in Long Island Sound.
• Estuarine resources in the Virginian Province
were stratified into classes for purposes of
sampling and analysis. The classes and their
areal extent are as follows: Large estuaries,
16,097 km2; small estuaries, 4,875 km2; and
tidal rivers, 2,602 km2.
• The large estuary class includes Chesapeake Bay
(main stem plus lower Potomac River), Delaware
Bay, Long Island Sound, Block Island Sound,
Buzzard's Bay, Narragansett Bay, and Nantucket
Sound.
• The tidal river class includes, the James,
Rappahanock, Potomac, Delaware, and Hudson
Rivers.
• The small estuary class includes 144 estuarine
systems of various types between 2.6 and 260
km2 in area of which 29 were sampled in 1991.
5.2 Findings of the 1991 Sample Year
All but 1 of the 155 scheduled stations were
successfully sampled. The majority of the data collected
at these stations met the quality control standards set
by the Program.
The incidence of gross external fish pathologies was
0.6% (16 occurrences among 2,513 fish examined) based
on field observations. However, fewer than half of the
pathologies identified by field' crews were confirmed
by a qualified pathologist.
Table 5-1 summarizes the data presented in Section
3 for selected Biotic Condition, Abiotic Condition, and
Habitat indicators.
Page 70
Statistical Summary, EMAP-E Virginian Province - 1991
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Table 5-1. Percent area of the Virginian Province (with 95% confidence intervals) above or below values "of
interest for biotic and abiotic condition indicators.
Percent area
Estuarine Condition
Benthic Index
<0
Total Benthic Abundance
<200 / mz
Instantaneous Bottom DO
<2 mg/l
<5 mg/l
Province
14
6
5
18
±6
±5
±5
±8
Large
Estuary
6 ±7
2 ±4
4±6
17± 10
Large
Tidal
River
27 ± 14
15 ±28
15 ±28
18 ±28
Small
Estuary
32 ± 17
13 ± 13
1 ±2
21 ± 13
Sediment Toxicity
(% control survival)
<80%
21 ± 10
Marine Debris
presence 18 ± 8
Enriched metals
any metal
above background 41 ± 10
Salinity
Polyhaline (>18 %<>) 63 ± 10
Mesohaline (5 to 18 %<>) 30 ± 10
Oligohaline (< 5 %0) 7 ± 3
24 ± 13
12±9
35 ± 14
79 ± 11
21 ± 11
0±0
10 ±7
16 ±38
51 ±23
0±0
55 ± 34
45 ± 18
19 ± 14
35 ± 17
53 ±22
42 ± 16
47 ± 16
11 ±11
Statistical Summary, EMAP-E Virginian Province - 1991
Page 71
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SECTION 6
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Statistical Summary, EMAP-E Virginian Province - 1991 ' Page 77
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APPENDIX A
SAMPLING DESIGN, ECOLOGICAL INDICATORS,
AND METHODS
A.I Region and Estuarine Classification
EMAP-E monitoring is conducted on regional and
national scales. Standardized methods are employed,
and the entire Virginian Province is sampled simulta-
neously within a defined "index" time period (July 1 -
September 30) to ensure comparability of data within
and among sampling years. EMAP-E identified
boundaries for 12 estuarine regions (Holland, 1990)
based on biogeographic provinces defined previously
by NOAA and the U.S. Fish and Wildlife Service using
major climatic zones and prevailing major ocean
currents (Terrell, 1979) (Figure A-l). The 1990
Virginian Province Demonstration Project and the 1991
survey included the estuarine resources located along
the irregular coastline of the mid-Atlantic coast between
Cape Cod, MA and Cape Henry, VA, including but not
limited to: Buzzards Bay, Narragansett Bay, Long Island
Sound, New York/New Jersey Harbors, Delaware Bay,
and Chesapeake Bay. Five major rivers within the
Province were monitored: the Hudson, the Delaware,
the Rappahannock, the Potomac, and the James.
A review of the literature identified potential
classification variables that reduced within-class
variability. These variables included physical attributes
(salinity, sediment type, depth), and extent of pollutant
loadings. The use of salinity, sediment type, and
pollutant loadings as classification variables (i.e., a
priori strata) would result in the definition of classes
for which areal extents could vary dramatically from
year-to-year or even over the index sampling period of
EMAP-E. This stratification process requires
establishment of a sampling frame prior to sampling;
thus misclassification of sample sites within a class should
be minimized. Stratification by sediment type, depth,
or salinity was considered to be difficult because detailed
maps of sediment and water column characteristics were
not available.or are often unreliable for much of the Virginian
Province. These attributes were not used.
A simple classification scheme based on the physical
dimensions of an estuary was used to develop three classes -
- large estuaries, large tidal rivers, and small estuaries/small
tidal rivers. Large estuaries in the Virginian Province
were defined as those estuaries greater than 260 km2 in
surface area and with aspect ratios (i.e., length/average
width) of less than 18. Large tidal rivers were defined
as that portion of the river that is tidally influenced (i.e.,
detectable tide > 2.5 cm), greater than 260 km2, and with
an aspect ratio of greater than 18. Small estuaries and
small tidal rivers were designated as those systems whose
surface areas fell between 2.6 km2 and 260 km2. These
designations excluded estuarine water bodies less than
2.6 km2 in surface area. These resources were included
in the sampling frame by making them a part of the class
occupied by their adjacent water body, but were not sampled
separately.
Application of the classification scheme based upon
geometric dimensions (criteria unlikely to change in reasonable
time frames) to the Virginian Province estuarine resources
resulted in the identification of 12 large estuaries; 5 large
tidal rivers; and 144 small estuaries / small tidal rivers.
Statistical Summary, EMAP-E Virginian Province - 1991
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Columbian
Virginian
Acadian
Carolinian
West Indian
Figure A-1. EMAP-Estuaries biogeographical provinces.
A.2 Sampling Design
Sample collection in the Virginian Province focused
on ecological indicators (see Section A.6) during the
index sampling period (July 1 - September 30), the
period when many estuarine responses to anthropogenic
and natural stresses are anticipated to be most severe.
The proposed sampling design combines the strengths
of systematic and random sampling with an
understanding of estuarine ecosystems in order to
provide a probability-based estimate of estuarine status
in the Virginian Province. In addition, some special-
study sites were sampled to collect information for spe-
cific hypothesis testing and other specific study
objectives. This resulted in sampling five types of
sampling sites (stations) for the Virginian Province
survey.
• Base Sampling Sites CBSS") are the probability-based
sites which form the core of the EMAP-E
monitoring design for all provinces, including the
Virginian Province. Data collected from these sites
are the basis of this preliminary status assessment.
There were 102 BSS to be sampled during the 1991
index period. This represents approximately 1A of
the total number of base sites that will be s.ampled
over the four-year cycle.
Index Sites dNDI were a continuation of a special
study initiated in 1990. They are associated with
the base sampling sites in small estuarine systems
and are located in depositional environments where
there is a high probability of sediment contamination
or low dissolved oxygen conditions. A total of 29
IND sites were to be monitored in 1991.
Long-term Trend Sites (LTD were a select number
of 1990 BSS that were revisited in 1991. They will
be sampled each year to investigate the within-station
annual variability. Eleven (11) LTT sites were monitored
in 1991.
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Statistical Summary, EMAP-E Virginian Province - 1991
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Long-term Trends Spatial Transect (LTS) sites
were located along a transect originating at an LTT
station. Twelve (12) LTS sites were associated with
four transects in 1991 and were all located in the
Chesapeake Bay. Three LTS sites were placed along
each transect at 0.25,0.5, and 1.0 statute miles from
the associated LTT station to evaluate the spatial
variability within a sampling cell.
Indicator Testing and Evaluation CITE) sites were
initiated in the 1990 Demonstration Project to
determine the reliability, sensitivity, and replicability
of indicator responses for discriminating between
sites with "known" environmental conditions. These
sites were selected on the basis of historical
information concerning dissolved oxygen
concentration and sediment contamination. These
sites were used to develop indices and test the
discriminatory power of specific indicators. In 1991,
six ITE stations were chosen representing our
preliminary estimate of degraded, non-degraded or
intermediate conditions in the Province. Five of
these six stations were filled using existing 1991
BSS sites; one was added as a non-random site and
was not used in this assessment. These sites are
used to evaluate the performance of "research"
indicators. In 1991 the sole research indicators were
fish histopathology and redox potential discontinuity
(RPD).
A.3 Indicators
EMAP monitoring focuses on indicators of
biological response to stress, and uses measures of
exposure to stress or contamination as a means for
interpreting that response. Traditionally, estuarine
monitoring has focused on measures of exposure (e.g.,
concentrations of contaminants in sediments) and
attempted to infer ecological impacts based on
laboratory bioassays. The advantage of the ecologically-
based approach emphasized in EMAP is that it can be
applied to situations where multiple stressors exist, and
where natural processes cannot be modeled easily. This
is certainly the case in estuarine systems, which are
subject to an array of anthropogenic inputs and exhibit
a great biotic diversity and complex physical, chemical,
and biological interactions.
The implementation plan for the Virginian Province
(Schimmel, 1990) listed three general indicator categories
for the Demonstration Project: core, developmental and
research. These same categories were employed in 1991,
although two research indicators were not continued (water
column toxicity and relative abundance of and tissue
contaminants in large bivalves). Table A-l lists the indicators
retained in the 1991 field survey.
Table A-1. Ecological indicators used in the 1991 Virginian
Province Survey.
Core
Developmental
Research
Indicator
Benthic Species Composition & Biomass
Habitat Indicators
(Salinity, pH, Temperature.Water
Depth, % Silt-Clay)
Sediment Contaminants
Sediment Toxicity
Dissolved Oxygen Concentration
Gross Pathology of Fish
Contaminants is Fish Tissue
Marine Debris
Fish Community Composition & Lengths
Water Clarity
Histopathology of Fish
Apparent RPD
A.4 Field Planning
The success of this complex survey depended upon
detailed and complete initial planning. Since 1991 was
the second year of sampling in the Virginian Province,
many of the documents generated for the 1990 Demonstration
Project (with mostly minor modification) served as the
basis for protocols, Standard Operating Procedures (SOPs),
and various planning documents. With minor exceptions,
most of the capital equipment purchased for 1990 was
used in 1991. Most contract mechanisms used for field
and laboratory analysis activities in 1990 were again
used in the succeeding year.
A.4.1 Reconnaissance
An important aspect of planning for the Virginian
Province survey was the conduct of desk and field
reconnaissance of the Province prior to execution of the
Statistical Summary, EMAP-E Virginian Province - 1991
Page A - 3
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survey. The purpose of the reconnaissance was to
acquire information that would facilitate the
development of logistics plans for field implementation.
The first phase of reconnaissance consisted of
plotting all of the 169 stations selected for the Virginian
Province by EMAP-E on nautical charts. During this
desk exercise, six (6) stations were dropped from the
list since they were either in a large estuary class and
found to be located on land, or were in a small system
that was too shallow throughout to sample. Fifteen (15)
sites were located in small estuaries in water less than
2 meters in depth (i.e., the depth needed to deploy
Hydrolab meters) and were relocated within the same
small estuary. Based on these desk reconnaissance
results, a logistics plan (Strobel and Schimmel, 199la)
was developed to sample the remaining 163 sites over
a six-week period during July-September 1991, pending
the field reconnaissance results.
After the 1991 stations were chosen, an EMAP-E
design meeting was held in Columbia, MD to review
some of the 1990 results. This meeting produced
several changes in the 1991 program. These changes
resulted in an overall decrease in station number from
163 to 162.
During field reconnaissance, the crews checked the
coordinates, water depth, and access to sites identified
as questionable during desk reconnaissance. Seven sites
could not be sampled in the field due to insufficient
depth. This reduction of seven stations left a total of
155 stations to be sampled in the 1991 field collection
effort (the "expected" stations). The logistics plans
were modified to reflect these reductions.
In addition to the confirmation of acceptable station
conditions, evaluations were made of appropriate boat
ramp facilities, motel-and restaurant accommodations,
Federal Express offices, and dry ice suppliers. Most
of the crew chiefs participating in the 1991 survey also
participated in the 1990 effort and were, therefore,
familiar with many of the sites and the availability of
many of these facilities. Therefore, only limited field
reconnaissance was required.
A.4.2 Reference Documents
Before training and sampling could be initiated, several
reference documents were compiled to guide training,
ensure data quality, standardize field and laboratory methods,
and provide logistical support to the field teams. These
documents include:
• Field Operations and Safety Manual (Strobel and
Schimmel, 1991b),
• Quality Assurance Project Plan for the Virginian
Province (Valente and Schoenherr, 1991),
• Virginian Province Implementation Plan (Schimmel,
1990),
• Virginian Province Logistics Plan - (Strobel and
Schimmel, 199 la),
• EMAP-NC Laboratory Methods
Manual (U.S. EPA, 1991),
• 1991 Virginian Province Field
Readiness Report (Strobel, 1991).
A.5 Training
Formal training was held at the Environmental Research
Laboratory, Narragansett, RI and at the University of
Rhode Island Graduate School of Oceanography from
May 20 to June 19, 1991. The training was separated
into three portions — Crew Chief Training (late May),
Crew Training (June 17-July 3), and Field Certification
(July 8-17). A total of 28 participants were trained to
conduct sampling in accordance with EMAP protocols.
These protocols included vessel navigation, site location,
indicator sampling, sample processing, sample shipment,
quality control, and logistics. Verification of the crews'
understanding of the field protocols was determined by
the use of final field certification exercises. These exercises
consisted of "typical EMAP-VP" 2-day scenarios comprised
of site location, sample collection, sample jar coding,
data sheet completion, sample processing and shipping,
and electronic data entry and transfer. The crews were
required to conduct all components of the sampling activities
at each station and were evaluated by senior EMAP-E
personnel on their abilities to perform over 100 field
and laboratory functions.
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Statistical Summary, EMAP-E Virginian Province - 1991
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All crews were successfully certified. In addition
to detailed training on collection methods, shipping
procedures, etc., a comprehensive series of first aid and
general safety at sea courses were provided to all crew
members. These included: cardio-pulmonary resus-
citation, general first aid, trauma treatment, use of
survival suits, fire extinguishing procedures, etc. Proof
of swimming skills was also required of each crew
member.
A.6 Indicator Sampling Methods
The EMAP indicator strategy involves four types
of ecological indicators (Hunsaker and Carpenter, 1990;
Knapp et al. 1990): Biotic condition, abiotic condition,
habitat, and stressor. Biotic condition indicators are
ecological characteristics that integrate the responses
of living resources to specific or multiple pollutants and
other stresses, and are used by EMAP to assess overall
estuarine condition. Abiotic condition indicators quanti-
fy pollutant exposure and habitat degradation and are
used mainly to identify associations between stresses
on the environment and degradation in biotic condition
indicators. Habitat indicators provide basic information
about the natural environmental gradients. Stressor
indicators are used to quantify pollution inputs or
stresses and identify the probable sources of pollution
exposure. Tables A-2 and A-3 list individual indicators.
Table A-2. Ecological indicators categorized as biotic
condition, abiotic condition, and habitat indicators.
Table A-3. Subcomponents of ecological indicators.
Indicator Type
Biotic Condition
Abiotic Condition
Habitat
Indicator
Benthic Community Composition
Benthic Abundance
Benthic Biomass
Fish Community Composition
Fish Lengths
Pathology in Fish
Sediment Contaminants
Sediment Toxicity
Dissolved Oxygen Concentrations
Contaminants in Fish Tissue
Marine Debris
Water Clarity
RPD Depth
Salinity
Temperature
Percent Silt-Clay
PH
Water Depth
Primary Indicator Subcomponents
Benthos
Fish
Total abundance
Species composition
Species diversity
Abundance by species
Percentage by taxonomic group
Biomass
Biomass by taxonomic group
Total abundance
Species composition
Species diversity
Abundance by species
Percentage by taxonomic group
Mean length by species
Gross Pathology Type of disorder
Dissolved Instantaneous at sampling
Oxygen Continuous for 24-hr (15-min intervals)
Sediment Toxicity Ampelisca abdita 10-day test
Sediment 23 polycyclic aromatic hydrocarbons
Contaminants 15 metals
15 pesticides
18 PCB congeners
Butyltins
Sediment Percent silt-clay
Characters Acid Volatile Sulfides (AVS)
Total organic carbon (TOC)
Tissue 13 metals
Contaminants 16 pesticides
20 PCB congeners
Descriptions of the methods used for individual indicators
have been taken from the Near Coastal Program Plan
(Holland, 1990), the Virginian Province Implementation
Plan (Schimmel, 1990), the Virginian Province Field
Operations and Safety Manual (Strobel and Schimmel,
1991b), and the Near Coastal Laboratory Methods Manual
(U.S. EPA, 1991).
A.6.1 Biotic Condition Indicators
A.6.1.1 Benthos
Benthic invertebrate assemblages are composed of
diverse taxa with a variety of reproductive modes, feeding
guilds, life history characteristics, and physiological tolerances
to environmental conditions (Warwick, 1980; Bilyard,
1987). As a result, benthic populations respond to changes
in conditions, both natural and anthropogenic, in a variety
Statistical Summary, EMAP-E Virginian Province - 1991
Page A - 5
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of ways (Pearson and Rosenberg, 1978; Rhoads et al,
1978; Boesch and Rosenberg, 1981). Responses of
some benthic organisms indicate changes in water
quality while others indicate changes in sediment
quality. Most benthic organisms have limited mobility.
They are not as able to avoid exposure to pollution
stress as many other estuarine organisms (e.g., fish).
Benthic communities have proven to be a reasonable
and effective indicator of the extent and magnitude of
pollution impacts in estuarine environments (Bilyard,
1987; Holland, er al. 1988 and 1989).
Benthic samples for evaluation of species
composition, abundance, and biomass were collected
at all sampling sites. Samples were collected with a
Young-modified van Veen grab that samples a surface
area of 440 cm2. Three (3) grabs were collected at each
base, index, or long-term site. A small core (60 cc) was
taken from each grab for sediment characterization. The
remaining sample was sieved through a 0.5 mm screen
using a backwash technique that minimized damage to
soft-bodied animals. Samples were preserved in 10%
formalin-rose bengal solution and stored for at least 30
days prior to processing to assure proper fixation.
In the laboratory, macrobenthos were transferred
from formalin to an ethanol solution and sorted,
identified to lowest practical taxonomic level, and
counted. Biomass was measured for key taxa and all
other taxa were grouped according to taxonomic type
(e.g., polychaetes, amphipods, decapods). Shell-free
dry weight was determined using an analytical balance
with an accuracy of 0.1 mg after drying at 60°C. Large
bivalves were shucked prior to determining biomass.
Smaller shells were removed by acidification using a
10% HC1 solution.
A.6.1.2 Fish
There are several advantages to using fish as a
potential indicator of estuarine condition. Because of
their dominant position at the upper end of the estuarine
food web, fish responses integrate many short-term and
small-scale environmental perturbations. Fish are
known to respond to most environmental problems of
concern in estuaries, including eutrophication, habitat
modification, and pathogenic or toxic contamination.
Fish were collected by trawling with a 15 m, high-rise
otter trawl with a 2.5-cm mesh cod end. The net was
towed for 10 minutes against the tide (if significant tidal
current existed) between 0.5 and 1.5 m/s (1-3 knots).
All fish caught in the trawl were identified to species
and counted; up to 30 fish of a species from each collection
were measured to the nearest millimeter.
A maximum of five (5) individuals per target species
were retained from each base station trawl for tissue analysis.
The specimens were labeled, frozen on dry ice, packaged
and shipped to the laboratory where they were stored
frozen for subsequent tissue contaminant analysis. In
the laboratory, muscle tissue samples were composited
by species (by station) and analyzed for the compounds
listed in Table A-4.
Individual target species collected in standard trawls
were inspected for gross external pathological disorders
at all stations where fish were collected. This inspection
included checking body surface and fins for skin discoloration,
raised scales, white or black spots, ulcers, fin erosion,
lumps or growths and condition of the eyes. Specimens
with observed gross pathologies were preserved in Dietrich's
solution for subsequent laboratory verification and histological
examination. At indicator testing sites, all specimens
exhibiting gross pathologies, and up to 25 pathology-free
specimens of each target species, were preserved for quality
control checks of field observations. These fish also
received histopathological examinations related to liver
lesions, spleen macrophage aggregates, and gill or kidney
disfunction (research indicator).
A.6.2 Abiotic Condition Indicators
A.6.2.1 Sediment Collection Procedures
Sediments were collected using the same Young-modified
van Veen grab used for benthic invertebrate sampling.
The top 2 cm of 6-10 grabs were placed in a teflon mixing
bowl and homogenized. Care was taken to avoid collecting
sediment adjacent to the edges of the collection device.
After approximately 2,000 cc of sediment were collected
and completely homogenized, the sediment was distributed
among containers for sediment characterization, sediment
chemistry, and sediment toxicity testing.
Page A - 6
Statistical Summary, EMAP-E Virginian Province - 1991
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Table A-4. 1991 EMAP Virginian Province: Fish Tissue Chemistry Analytes
Analyte Code
Definition
AG
AL
AS
CD
CR
CU
FE
HG
MN
Nl
PB
SE
SN
ZN
PCB8
PCB18
PCB28
PCB44
PCB52
PCB66
PCB101
PCB105
PCB110/77
PCB118
PCB126
PCB128
PCB138
PCB153
PCB170
PCB180
PCB187
PCB195
PCB206
PCB209
OPDDE
PPDDE
OPDDD
PPDDD
OPDDT
PPDDT
ENDRIN
ALDRIN
ALPHACHL
TNONCHL
DIELDRIN
HEPTACHL
HEPTAEPO
LINDANE
MIREX
Silver Concentration in ug/g Dry Weight
Aluminum Concentration in ug/g Dry Weight
Arsenic Concentration in ug/g Dry Weight
Cadmium Concentration in ug/g Dry Weight
Chromium Concentration in ug/g Dry Weight
Copper Concentration in ug/g Dry Weight
Iron Concentration in ug/g Dry Weight
Mercury Concentration in ug/g Dry Weight
Manganese Concentration in ug/g Dry Weight
Nickel Concentration in ug/g Dry Weight
Lead Concentration in ug/g Dry Weight
Selenium Concentration in ug/g Dry Weight
Tin Concentration in ug/g Dry Weight
Zinc Concentration in ug/g Dry Weight
2,4'-dichlorobiphenyl in ng/gram
2,2',5-trichlorobiphenyl in ng/gram
2,4,4'-trichlorobiphenyl in ng/gram
2,2',3,5'-tetrachlorobiphenyl in ng/gram
2,2',5,5'-tetrachlorobiphenyl in ng/gram
2,3',4,4'-tetrachlorobiphenyl in ng/gram
3,3',4,4',5-pentachlorobiphenyl in ng/gram
2,2',4,4',5-pentachlorobiphenyl in ng/gram
2,2',4,5,5'-pentachlorobiphenyl4- 3,3',4,4'-tetrachlorobiphenyl in ng/gram
2,3,3',4,4'-pentachlorobiphenyl in ng/gram
2,3',4,4',5-pentachlorobiphenyl in ng/gram
2,2',3,3',4,4!-hexachlorobiphenyl in ng/gram
2,2',3,4,4',51-hexachlorobiphenyl in ng/gram
2,2',4,4',5,5'-hexachlorobipheny! in ng/gram
2,2',3,3',4,4',5-heptachlorobiphenyl in ng/gram
2,2',3,4,4',5,5'-heptachlorobiphenyl in ng/gram
2,2',3,4',5,5',6-heptachlorobiphenyl in ng/gram
2,2l,3,3',4',4',5,6-octachlorobiphenyl in ng/gram
2)2',3,3',4,4',5,5',6-nonachlorobiphenyl in ng/gram
Decachlorobiphenyl in ng/gram
2,4'-DDE DDT and metabolites in ng/gram
4,4'-DDE DDT and metabolites in ng/gram
2,4'-DDD DDT and metabolites in ng/gram
4,4'-DDD DDT and metabolites in ng/gram
2,4'-DDT DDT and metabolites in ng/gram
2,4'-DDT DDT and metabolites in ng/gram
Endrin in ng/gram
Aldrin in ng/gram
Alpha-Chlordane in ng/gram
Trans-Nonachlor in ng/gram
Dieldrin in ng/gram
Heptachlor in ng/gram
Heptachlor epoxide in ng/gram
Lindane (gamma-BHC) in ng/gram
Mirex in ng/gram
Statistical Summary, EMAP-E Virginian Province - 1991
Page A - 7
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A.6.2.2 Sediment Characterization
The physical characteristics of estuarine sediments
(e.g., grain size) and certain chemical aspects of
sediments (e.g., acid volatile sulfide [AVS] content, total
organic carbon [TOC] content) influence the distribution
of benthic fauna and the accumulation of contaminants
in sediments (Rhoads, 1974; Plumb, 1981; DiToro et
aLt 1991). Sediment silt-clay content was determined
to help interpret biotic condition indicator data and
sediment contaminant concentrations. AVS and TOC
were collected not only as interpretive aids but also as
potential covariates for toxic contaminant concentra-
tions.
Subsamples from each benthic grab and
contaminant/ toxicity homogenate were retained for
grain size determination. A subsample for AVS content
was removed from the homogenate. Samples were
shipped, on ice, to their respective processing
laboratory. Samples for the determination of silt/clay
content were sieved using a 63um mesh sieve. Both
the aliquot of the filtrate and the fraction retained on
the sieve were dried in an oven at 60°C and weighed
to calculate the proportion of silt/clay in the sample.
TOC and AVS concentrations were determined for
each site. TOC (from the chemistry sample) was
determined by drying a minimum of 5 g wet weight of
sediment for 48 hours. Weighed subsamples were
ground to fine consistency and acidified to remove
sources of inorganic carbon (e.g., shell fragments). The
acidified sample was ignited in a furnace at
approximately 950°C and the carbon dioxide evoked was
measured with an infrared gas analyzer. These peaks
were converted to total organic carbon.
The concentration of AVS was determined by the
measurement of amorphous or moderately crystalline
monosulfides. These substances are important in
controlling the bioavailability of metals in anoxic
sediments. If the molar ratio of metal to AVS exceeds
one, then the metal is potentially bioavailable (DiToro
etal., 1990).
The collection methods employed in the 1991
Survey permitted the potential release of sulfides when
the materials where processed on-board the sampling
vessel and in subsequent shipping. The sample was
collected from a homogenized composite (i.e., allowing
maximal exposure to oxygen) and shipped on ice to the
analytical laboratory. As a result, the accuracy of the
AVS measurements could be in doubt although the precision
may remain reliable as all samples were treated similarly.
Modifications to the collection methods have been determined
for the 1992 sampling to prevent a recurrence of these
problems.
A.6.2.3 Sediment Contaminants
Metals, organic chemicals, and fine-grained sediments
entering estuaries from freshwater inflows, point sources
of pollution, and various non-point sources including
atmospheric deposition, generally are retained within
estuaries and accumulate in the sediments (Turekian;'
1977; Forstner and Wittmann, 1981; Schubel and Carter,
1984; Nixon et al, 1986; Hinga, 1988). Samples were
collected from a homogenate created during sampling
by combining the top 2 cm of sediment from 6-10 sediment
grabs. The sediment was placed in clean glass jars with
teflon liners or polypropylene containers (for organics
and metals analyses, respectively), shipped on ice, and
stored frozen in the laboratory prior to analysis for organic
contaminants. Sediments were analyzed for the NO A A
Status and Trends suite of contaminants (Table A-5).
A.6.2.4 Sediment Toxicity
Sediment toxicity testing is the most direct measure
available for determining the toxicity of contaminants
in sediments to indigenous biota. It improves upon direct
measurement of sediment contaminants because many
contaminants are tightly bound to sediment particles or
are chemically complexed and, therefore, are not biologically
available (U.S. EPA, 1989). Sediment toxicity testing,
however, cannot be used to replace direct measurement
of the concentrations of contaminants in sediment because
such measurements are an important part of interpreting
the results of toxicity tests.
Toxicity tests were performed of the composite sediment
samples from each station. Tests were conducted using
the standard 10-day acute test method (Swartz et al.,
1985; ASTM 1991) and the tube-dwelling amphipod Ampelisca
abdita.
Page A - 8
Statistical Summary, EMAP-E Virginian Province - 1991
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Table A-5. 1991 EMAP Virginian Province: Sediment Chemistry Analytes
Analyte Code
Definition
TOC
AG
AL
AS
CD
CR
CU
FE
HG
MN
Nl
PB
SB
SE
SN
ZN
PCB8
PCB18
PCB28
PCB44
PCB52
PCB66
PCB101
PCB105
PCB118
PCB128
PCB138
PCB153
PCB170
PCB180
PCB187
PCB195
PCB206
PCB209
MBT
DBT
TBT
OPDDE
PPDDE
OPDDD
PPDDD
OPDDT
PPDDT
Total Organic Carbon Concentration in pg/g Dry Weight
Silver Concentration in pg/g Dry Weight
Aluminum Concentration in pg/g Dry Weight
Arsenic Concentration in pg/g Dry Weight
Cadmium Concentration in pg/g Dry Weight
Chromium Concentration in ug/g Dry Weight
Copper Concentration in ug/g Dry Weight
Iron Concentration in ug/g Dry Weight
Mercury Concentration in ug/g Dry Weight
Manganese Concentration in pg/g Dry Weight
Nickel Concentration in pg/g Dry Weight
Lead Concentration in pg/g Dry Weight
Antimony Concentration in pg/g Dry Weight
Selenium Concentration in pg/g Dry Weight
Tin Concentration in pg/g Dry Weight
Zinc Concentration in pg/g Dry Weight
2,4'-dichlorobiphenyl in ng/gram
2,2',5-trichlorobiphenyl in ng/gram
2,4,4'-trichlorobiphenyl in ng/gram
2,21,3,5'-tetrachlorobiphenyl in ng/gram
2,2',5,5'-tetrachlorobiphenyl in ng/gram
2,3',4,4'-tetrachlorobiphenyl in ng/gram
3,3',4,4',5-pentachlorobiphenyl in ng/gram
2,2',4,4',5-pentachlorobiphenyl in ng/gram
2,3,3',4,4'-pentachlorobiphenyl in ng/gram
2,2',3,3l,4,4'-hexachlorobiphenyl in ng/gram
2,2',3)4,4',5'-hexachloroblphenyl in ng/gram
2I2',4,41,5,5'-hexachlorobiphenyl in ng/gram
2,2',3,3',4,4',5-heptachlorobiphenyl in ng/gram
2,2',3,4,4',5,5'-heptachlorobiphenyl in ng/gram
2,2',3,4',5,5',6-heptachlorobiphenyl in ng/gram
2,2',3,3',4,4',5,6-octachlorobiphenyl in ng/gram
2,2',3,3',4,41,5,5',6-nonachlorobiphenyl in ng/gram
Decachlorobiphenyl in ng/gram
Mono-butyl Tin in ng/gram
Di-butyl Tin in ng/gram
Tri-butyl Tin in ng/gram
2,4'-DDE DDT and metabolites in ng/gram
4,4'-DDE DDT and metabolites in ng/gram
2,4'-DDD DDT and metabolites in ng/gram
4,4'-DDD DDT and metabolites in ng/gram
2,4'-DDT DDT and metabolites in ng/gram
2,4'-DDT DDT and .metabolites in ng/gram
(Continued)
Statistical Summary, EMAP-E Virginian Province - 1991
Page A - 9
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Table A-5 (continued).
Analyto Code
Definition
ALDRIN
ALPHACHL
TNONCHL
DIELDRIN
HEPTACHL
HEPTAEPO
HEXACHL
LINDANE
MIREX
NAPH
MENAP2
MENAP1
BIPHENYL
DIMETH
ACENTHY
ACENTHE
TRIMETH
FLUORENE
PHENANTH
ANTHRA
MEPHEN1
FLUORANT
PYRENE
BENANTH
CHRYSENE
BENZOBFL
BENZOKFL
BENAPY
BENEPY
PERYLENE
INDENO
DIBENZ
BENZOP
SAND_PC
SICL_PC
Aldrin in ng/gram
Alpha-Chlordane in ng/gram
Trans-Nonachlor in ng/gram
Dieldrin in ng/gram
Heptachlor in ng/gram
Heptachlor epoxide in ng/gram
Hexachlorobenzene in ng/gram
Lindane (gamma-BHC) in ng/gram
Mirex in ng/gram
Naphthalene in ng/gram
2-methylnaphthaiene in ng/gram
1-methylnaphthalene in ng/gram
Biphenyl in ng/gram
2,6-dimethylnaphthalene in ng/gram
Acenaphthlylene in ng/gram
Acenaphthene in ng/gram
2,3,5-trimethyinaphthalene in ng/gram
Fiuorene in ng/gram
Phenanthrene in ng/gram
Anthracene in ng/gram
1-methylphenanthrene in ng/gram
Fiuoranthene in ng/gram
Pyrene in ng/gram
Benz(a)anthracene in ng/gram
Chrysene in ng/gram
Benzo(b)fluoranthene in ng/gram
Benzo(k)fluoranthene in ng/gram
Benzo(a)pyrene in ng/gram
Benzo(e)pyrene in ng/gram
Perylene in ng/gram
ldeno(1,2,3-c,d)pyrene in ng/gram
Dibenz(a,h)anthracene in ng/gram
Benzo(g,h,i)perylene in ng/gram
Sand Content (%)
Silt-Clay Content (%)
A.6.2.5 Dissolved Oxygen
Dissolved oxygen (DO) is a fundamental
requirement for maintenance of populations of benthos,
fish, shellfish, and other estuarine biota. DO
concentrations are affected by environmental stresses,
such as point and non-point discharges of nutrients or
oxygen-demanding materials (e.g., particulates,
dissolved organic matter). In addition, stresses that
occur in conjunction with low DO concentrations may
be even more detrimental to biota (e.g., exposure to
hydrogen sulfide, decreased resistance to disease and
contaminants). DO levels are highly variable over time,
fluctuating widely due to tidal action, wind stress, and
biological activity (Kemp and Boynton, 1980; Welsh
andEller, 1991).
Dissolved oxygen was sampled in three ways during
the 1991 Virginian Province survey: 1) instantaneous
water column profiles using a SeaBird model SEE 25
CTD, (2) point in time bottom oxygen conditions with
a YSI (model 58) oxygen meter and the SeaBird CTD,
Page A - 10
Statistical Summary, EMAP-E Virginian Province - 1991
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and 3) continuous 24-72 hr measurements of bottom
concentrations using a Hydrolab DataSonde 3 data
logging array. The first two measurements were taken
at all sites, and the continuous measurements were taken
at base stations (ESS) only.
The Hydrolab DataSonde 3 data logger deployed
at each Base site for 24-72 hours collected continuous
DO data at 15-min intervals. The DataSonde 3 also
collected salinity, temperature, water depth, and pH
data. The instruments were calibrated prior to every
deployment, and were checked on-board ship
immediately prior to deployment by comparison to the
YSI oxygen meter, and following retrieval. These
instruments were deployed approximately 1 m from the
bottom. The stored data were downloaded to a
computer and the unit was serviced and recalibrated for
subsequent deployment at another site.
A.6.3 Habitat Indicators
Habitat indicators provide basic information about
the natural environmental setting. Habitat indicator data
included in this report include water depth, salinity,
temperature, pH, water clarity, and sediment silt/clay
content.
All water quality measurements were made using
the Seabird model SEE 25 CTD (described earlier).
This unit was equipped with prdbes to measure salinity,
temperature, depth, pH, DO, light transmission,
fluorescence, and PAR. All CTD data were downloaded
to a computer in the field for review and storage.
Measurements of water clarity are incorporated into
the CTD casts that were performed at each station.
Included in the CTD instrumentation package are a
SeaTech transmissometer and a Biospherical PAR
(Photosynthetically Active Radiation) sensor. As the
CTD is lowered through the water column, transmis-
sivity and PAR data are continually logged. The main
concern in obtaining these measurements is that the
lenses on the Jransmissometer are cleaned before each
use.
Surficial water samples were collected at all stations
for determination of Total Suspended Solids (TSS).
Samples were refrigerated, returned to the laboratory,
filtered through a glass-fiber filter, dried and weighed.
Sediment silt/clay content was measured on samples
taken from the surficial sediment (top two cm) homogenate
from which chemistry and toxicity samples were also
removed.
The kinds and amounts of floating and submerged
(i.e., collected in trawls) marine debris were noted at
all stations. Debris was categorized as paper, plastics,
metal, glass, wood, and other wastes. Only debris of
anthropogenic origin was included. Wastes that were
comprised of composited materials (e.g., metal, wood,
and plastic) were categorized based on their dominant
component.
A.7 Data Collection and Sample Tracking
Each field crew was supplied with two portable computers
and appropriate software to facilitate electronic recording
of the data, data transfer, and sample tracking. All samples,
shipments, and equipment were labelled with bar-coded
labels to facilitate sample tracking and reduce transcription
errors. Field computers were equipped with bar code
readers to record sample identification numbers. Receiving
laboratories were also equipped with bar code readers
to facilitate the receiving process and to rapidly convey
information concerning lost or damaged shipments.
Copies of all data entered into the field computer
were stored on the hard disk and copied to diskettes.
Information on the hard disk was transferred daily via
commercial carrier phone lines to the Information Management
Center at ERL-Narragansett (RI).
Backup diskettes and hard-copy data sheets were
shipped weekly to the Center.
All transferred data were examined within 24-48 hours
of collection by EMAP-E personnel. Errors were brought
to the attention of the field crews for correction and
resampling, if required. All electronic data were checked
against paper data forms for verification. Further information
on the details of the Near Coastal data management systems
are presented in Rosen et al. (1990).
Statistical Summary, EMAP-E Virginian Province - 1991
Page A - 11
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A.8 Analytical Methods For Statistical
Summary
Three types of analyses were conducted for this
report: 1) direct descriptions of measured indicators, 2)
development of modified or adjusted indicators (e.g.,
metal contaminants in sediments), and 3) development
of indices based on directly measured indicators. These
analyses are documented in a Virginian Province 1990
Demonstration Report (Weisberg et al., 1993).
A.8.1 Cumulative Distribution Functions
(CDFs)
All ecological indicators collected during the 1991
Virginian Province survey were characterized using
Cumulative Distribution Functions (CDFs). These
functions describe the full distribution of indicators in
relation to their areal extent within the Province. All
observations are weighted based upon surface area
associated with each sampling site. The area associated
with each sampling unit in large estuaries was equal to
the hexagonal spaces created by the EMAP grid (70
km2). For tidal river and small estuary classes, the area
associated with each sampling segment was determined
using the ARC/INFO data model which produces areal
and perimeter estimates. For the tidal river class
ARC/INFO version 5.0 (ESRI) was used to delineate
the extent of each segment on a 1:100,000 digital line
graph. The total areas associated with the three classes
is: large estuaries - 16,097 km2; large tidal rivers - 2,602
km2; and small estuaries - 4,875 km2.
To generate estimates across classes (strata), weights
for stations within each class were adjusted so that the
total of the weights for that class was equal to the total
area represented by the stations within that class. This
adjustment primarily affects the small estuary class
because this resource is sub-sampled from the list of all
possible systems. Only 29 of the 144 small estuarine
class systems were sampled in 1991 representing 18%
of the total surface area of the small estuary/ small tidal
river class.
A.5.2 Adjustment To Known Covariates
In several cases, variability in observed indicators
might reflect relationships to known habitat or control
variables. Examples of these relationships are: variation
in estuarine biota resulting from sampling throughout
the salinity gradient; variation in sediment toxicity tests
with different mortalities associated with the controls;
and variation in sediment metals observed at a site resulting
from variations in the amount of natural crustal materials
at the site. In all these cases, the observed data must
be adjusted in order to construct CDFs or to compare
observations from different locations.
A.8.2.1 Adjustment for Natural Habitat Gradients
Estuarine biota are largely controlled by their
environmental settings, both natural and anthropogenic.
Natural gradients, particularly in salinity and silt-clay
content, are common in estuaries. Many estuarine organisms
may represent overlapping discrete distributions along
these gradients; Thus, normalization of ecological measures
over habitat gradients is a common tool used to interpret
information when such normalization is necessary.
Many ecological variables are significantly correlated
with natural gradients (i.e., salinity, silt-clay content,
water depth). However, these correlations often explain
very little of the total variation observed in that variable.
The 1990 EMAP-E effort in the Virginian Province (Weisberg
et. al., 1993) suggested that benthic distributions (e.g.,
number of species, percentage community composition,
biomass) needed to be adjusted for salinity gradients
before inclusion in the "Benthic Index" (see Appendix
B) because these gradients explained greater than 25%
of the total variation in these benthic indicators. Similar
analyses using the 1990 Virginian Province data showed
that while many other benthic and fish indicators were
significantly correlated to habitat gradients; none of these
correlations accounted for more than 15% of the total
variability. As a result, only the expected number of
benthic species used in the benthic index was adjusted
for salinity:
A.8.2.2 Adjustment for Experimental Controls
Estimates of the area in the Virginian Province containing
toxic sediments were based on the results of toxicity
tests using the amphipod, Ampelisca abdita. For this
summary, a relative measure of toxicity was created to
facilitate comparisons between sites over a series of bioassays.
This adjustment is necessary because control mortalities
Page A - 12
Statistical Summary, EMAP-E Virginian Province - 1991
-------
vary among test series. Sediments were determined to
be toxic if: the survival of the test organism in test
sediments was les,s than or equal to 80% of the survival
observed in clean, control sediments; if the survivals
in test and control sediments were significantly different
(p < 0.05); and if survival in control sediments was >
85%. This results in an adjustment to the observed
survival rates in test sediments that accounts for
variability due to differences in the controls for
individual bioassays. These criteria are consistent with
those established in U.S. EPA/ACE (1991).
A.8.2.3 Adjustment for Natural Crustal
Properties
The extent to which anthropogenic activities have
affected concentrations of metals in sediments is
complicated by the natural variation of concentrations
due to differing particle size distributions in sediments.
Because of surface adsorptive and complexation
processes, fine-grained sediments will naturally have
higher trace metal concentrations than coarse sediments.
In some studies, e.g., the National Status and Trends
program, reported concentrations are adjusted for this
variation by normalizing the concentrations by the fine-
grained fraction determined separately. As an alterative
to actual size-fractionation measurements, a number of
authors (Windom et al, 1989; and Schropp et al., 1990)
have determined relationships between sediment
concentrations of trace metals and other elements
indicative of fine-grained crustally-derived material,
e.g., aluminum, iron and manganese. The most
commonly used of these indicator elements is aluminum,
due to its large natural abundance, freedom from
common anthropogenic contaminant sources and
significant correlation with both the fine-grained fraction
and trace metal concentrations in clean, un-impacted
sediments. The correlation between aluminum and trace
metals in fine-grained sedimentary material has a
geochemical basis related to the composition of crustal
material from which the fine particles are derived and
the natural adsorption and complexation processes
occurring during "weathering" of the crustal material.
Once background sediment metal-aluminum
relationships have been determined, concentrations of
metals expected from background material can be
subtracted from total metal concentrations, allowing
residual, presumably anthropogenic, contributions to be
assessed.
Background metal-aluminum relationships are derived
by linear regression of sediment concentrations of each
element against aluminum concentrations in the same
sediment. Some investigators have used log-transformed
metals concentrations in the regression analyses. Such
transformations do not improve correlation of the metals-
aluminum concentrations of this data set. Furthermore,
linear regressions provide direct correlation with the physical
mixing and geochemical factors noted above which affect
the overall concentration of metals in sediments. This
correlation is lost when the concentrations are transformed.
Consequently, no data transformations were performed
prior to regression analysis.
Use of linear regression to determine metal-aluminum
relationships in background sedimentary material can
only be successful if the sediments do not include contributions
from sources other than natural background sediments.
The data sets used in this study were statistically screened
to eliminate samples which might contain additional source
materials. This was accomplished by performing linear
regressions of concentrations of aluminum against each
metal. The residuals (the differences between the measured
concentrations and those predicted from the regression)
were then tested for normal distribution. If the residuals
were found not to be normally distributed, samples which
had studentized residual values greater than 2 were eliminated
from the data set. Regression of the reduced data set
was repeated and the residuals tested again for normal
distribution. This process was repeated for each metal
until residuals from the regressions were all normally
distributed, at which point the remaining samples were
assumed to represent natural, background sediments.
The regression relationships derived for the background
sediments were then applied to the original data set. Samples
with trace metal concentrations exceeding the upper 95%
confidence limit for that metal's regression against aluminum
were designated as enriched. It should be noted that no
assessment was made as to the magnitude of enriched;
metal concentrations might be only slightly above the
95%confidence limit or might exceed the limit by factors
of 10-100. The categorization "enriched" was applied
to any sediment with a metal concentration higher than
that expected from the background sediment aluminum
metal relationship at the 95% confidence level.
Statistical Summary, EMAP-E Virginian Province - 1991
Page A - 13
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A.9 Procedures for the Calculation of
Confidence Intervals
The approximate 95% confidence intervals for the
Province were calculated based on the assumption that
the CDF estimates were distributed normally. The
confidence intervals were obtained by adding and
subtracting 1.96 times the estimated standard error
(square root of the variance) to the estimated CDF
value.
For small estuarine systems, estimates of CDFs and
associated variances were computed based on a random
selection of small systems within the Province, with
replicate samples taken from a subset of the selected
systems (Cochran, 1977). The resulting CDF estimate
is:
**-
where,
where,
GDP estimate for value x
m, » number of samples at small system i
Af * area of small system i
f 1 if response is less than x
*V \0 otherwise
n « number of small systems sampled
Since replicate samples were only obtained at a
subset of the sampled small estuarine systems, the
formula for the estimated variance taken from Cochran
(1977 eq. 11.30) was modified to produce the following
estimate of the approximate mean squared error (MSB)
of the CDF estimate:
_ number small systems with
replicate samples
. _ the total area of small systems in
the Province (4,875 km2)
N = number small systems in Province (144)
Estimates of CDFs for large tidal rivers were obtained
by applying Horvitz-Thompson estimation (Cochran,
1977) with selection probabilities being inversely related
to station area. Estimates of CDFs were:
p -if*.
*
where,
it,.
= Estimate CDF at value x
. 11 if response is less than x
' \ 0 otherwise
_ inclusion probability for station i
"' ~ (I/area)
A = total area of sampled tidal rivers
n = number of stations sampled
To achieve unbiased estimates of variance, joint event
probabilities( TC^) must be non-zero. For large tidal river
sampling, many joint event probabilities are zero and
other joint event probabilities are unknown; therefore,
an approximate variance estimate for the CDF estimates
was obtained by applying the Yates-Grundy estimate
of variance (Cochran, 1977) and using approximate joint
event probabilities (Stevens et al., 1991):
n
n-1
n*t-i mt
Page A - 14
Statistical Summary, EMAP-E Virginian Province - 1991
-------
where,
_ probability that sites i and j ate
1V selected for sampling
and
= 2(it-l)itinJ.
" 2n-it|.-it.
Estimates of CDFs for large systems (PLx) were also
obtained by applying Horvitz-Thompson estimation with
selection probabilities being inversely related to station
area. Areas for all base stations were assumed to be
70 km2. Formulae for the CDF estimates and
corresponding variances are analogous tp those
presented for large tidal rivers.
Estimates of CDFs for a particular geographic
system within the Province (e.g., Chesapeake Bay) were
obtained by applying the above procedures to the small
estuarine systems, tidal rivers, and large estuaries
sampled within that geographic system. Estimates of
the CDFs for the entire Province or'fo.r a geographic
system within the Province were computed as weighted
averages of the relevant station class CDFs:
where,
Ws = Relative area of small systems
WT = Relative area of tidal livers
WL = Relative area of large estuaries
In applying these procedures, variance estimation
was based on the assumption of a fixed sample size
within each resource class. For large tidal rivers and
large estuaries, the sample size is a random element
depending on the position of the sampling grid. This
variance component has not been incorporated into the
estimation of variances of CDFs.
Statistical Summary, EMAP-E Virginian Province - 1991 Page A - 15
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APPENDIX B
CALCULATION OF THE BENTHIC INDEX
B.I BACKGROUND
Biotic condition indicators are characteristics of the
environment that provide quantitative evidence of the
status of ecological resources and biological integrity
of the site from which they are drawn (Messer, 1990).
Ecosystems with a high degree of biotic integrity (i.e.,
healthy ecosystems) are composed of balanced
populations of indigenous organisms with species
compositions, diversity, and functional organization
comparable to natural habitats (Karr and Dudley, 1981;
Karr et al., 198$). Biotic condition indicators could
include measurements of the kinds and abundances of
biota present, the health of individual organisms, and
the sustainability of critical ecological processes. They
are the .empirical data collected by EMAP-E that are
integrated into indices that track the status and trends
in ecological integrity.
One category of biotic condition indicators which
was measured during the 1991 Virginian Province effort
was the benthic indicators. Results are presented for
numbers of species, total abundance, and an integrated
"Benthic Index".
Benthic invertebrates are the major trophic link
between primary producers and higher trophic levels,
including fish, shellfish, birds and other wildlife
(Carriker, 1967; Rhoads, 1974). They are a particularly
important source of food for juvenile fish and crabs
(Chao and Musick, 1977; Bell and Coull, 1978; Holland
et al., 1989). Estuarine benthos also have important
roles in ecological processes that affect water quality
and productivity. For example, the feeding and
burrowing activities of macrobenthos affect sediment
depositional patterns and chemical transformations
(Carriker, 1967; Rhoads, 1974; Kemp and Boynton,
1981). Benthic feeding activities can remove large amounts
of particulate materials from shallow estuaries, which
may improve water clarity (Cloern, 1982; Officer et al.,
1982; Holland et al., 1989).
A benthic index was developed using the Virginian
Province 1990 Demonstration Project data. The procedures
used to develop the Benthic Index in 1990 are documented
in the EMAP-Estuaries Virginian Province 1990 Demonstration
Project Report (Weisberg et. al., 1993). This index is
based on 5 parameters extracted from the raw Benthic
Infaunal data base for each EMAP base station.
The "discriminate score" was calculated using transformed
and normalized scores according to the equation below:
Discriminate score =
0.01053 * percent Expected
species {mean number}
+ 0.81692* Number of
Amphipods
+ 0.57697 * Average weight
for each polychaete
+ 0.46526 * Number of
Capitellid worms
+ 0.67136 * Percent of total
abundance which are
bivalves
A "critical" value of 3.4 was determined as the delimiter
between degraded conditions (BI < 3.4) and non-degraded
conditions (BI > 3.4).
Statistical Summary, EMAP-E Virginian Province - 1991
Page B- 1
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The "Expected number of species" at each station
was calculated based on a habitat gradient established
in 1990. This gradient indicated that the number of
species found at a station is related to the salinity of the
bottom waters at the station. Given similar anthropo-
genic influences at two stations, the number of species
found would be strongly influenced by the salinity of
the bottom waters. In order to normalize the expected
number of species to the salinity habitat gradient, the
baseline (or expected number of species) was established
by fitting a polynomial regression of the 90th percentile
of a 3 part per thousand (salinity) moving average of
species richness versus salinity (Weisberg et al., 1993).
Table B-1. Results of benthic index validation exercise. Numbers
represent the number,of stations in that cell of the matrix. Bl =
benthic index score.
Bl>3.4
(Reference)
B\< 3.4
(Degraded)
Reference
Stations
39 (85%)
7 (15%)
Degraded
Stations
6 (46%)
7 (54%)
46
13
45
14
59
B.2 VALIDATION OF THE 1990
BENTHIC INDEX
The process of validation involved testing the 1990
benthic index with an independent data set to ensure that
the multivariate solution was not specific to the original
test data set used in 1990. Using the same criteria
applied in 1990 to define "degraded" and "undegraded"
(/.e., reference) stations, an independent data set was
established from the 1991 database. This test data set
consisted of 13 stations classified as degraded based on
high sediment contaminant concentrations (combined
with toxicity) and/or low near-bottom dissolved oxygen
levels, and 46 stations classified as reference based on
low sediment contaminant levels and the absence of
toxicity and low dissolved oxygen conditions.
Of the 46 stations from 1991 classified as
"reference", the 1990 benthic index correctly classified
39 (85%) and misclassified 7 (15%) (Table B-1). Of
the 13 stations from 1991 classified as "degraded", the
1990 faenthic index correctly classified 7 (54%) and
misclassified 6 (46%). For these degraded stations, the
rate of correct classification was much higher for low
dissolved oxygen stations versus stations with
contaminated sediments. The relatively high overall rate
of misclassification, particularly for degraded stations,
was deemed unacceptable, and a decision was made to
reconstruct a new benthic index using the Combined
1990 and 1991 data sets.
B.3 RECONSTRUCTION OF THE
BENTHIC INDEX USING 1990-91
DATA
Reconstruction of the benthic index using the combined
1990 and 1991 data followed the same basic steps described
in the 1990 Demonstration Project Report (Weisberg
et. al. 1993). Results and discussion are presented in
the following sections.
Step 1: Develop a test data set
The following criteria (from 1990) were used to select
stations for reconstructing the benthic index:
DEGRADED STATIONS:
1.) Stations exhibiting sediment toxicity (i.e., % survival
less than 75 and significantly different from controls)
and having one or more contaminants exceeding Long
and Morgan (1990) ER-M values.
OR
2.) Stations exhibiting DO below 0.3 mg/L at any time,
or 10% of continuous measurements less than 1 mg/L,
or 20% less than 2 mg/L, or less than 2 mg/L for
24 consecutive hours.
REFERENCE STATIONS:
1.) Stations where no contaminant exceeded the ER-M
value, no sediment toxicity was observed (i.e., %
survival greater than 75% and not significantly different
Page B- 2
Statistical Summary, EMAP-E Virginian Province - 1991
-------
from controls), and for which bottom DO was never
less than 1 mg/L, 90% of the continuous DO
measurements were greater 3 mg/L and 75% of the
DO measurements were greater than 4 mg/L.
(NOTE: because of this criteria, only those 1991
stations having continuous DO records were
considered as potential reference stations).
Once an initial set of stations was identified using
this set of criteria, the list was reviewed carefully to
eliminate any reference sites located in areas potentially
subject to physical disturbance, such as dredged
shipping channels. Four sites were eliminated through
this process. The final test data set, combining 1990
and 1991 data, consisted of 31 degraded stations and
53 reference stations (Tables B-2 and B-3). Both the
degraded and reference stations encompassed a wide
range of habitats, including all major salinity zones and
sediment types that occur in the Virginian Province.
Step 2: Identify candidate benthic measures
As in 1990, benthic abundance, biomass, and species
composition data were used to define 28 descriptors of
the major ecological attributes of the benthic
assemblages occurring at each sample site (Table B-4).
In constrast to 1990, data for epifauna (organisms that
live on hard surfaces such as shells) were included in
the 1991 computations in an attempt to determine
whether any of the resultant metrics could discriminate
reliably between reference and degraded conditions.
Estuaries are characterized by large natural
variations in certain physiochemical conditions (e.g.,
salinity, sediment grain size) known to be major factors
controlling the diversity and abundance of resident biota.
Such factors must be identified and controlled for before
the responses of candidate benthic measures to pollution
exposure can be characterized accurately. Pearson
correlation coefficients were calculated to determine
relationships between the individual metrics listed in
Table B-4 and various physical habitat variables
including sediment silt-clay content, salinity, water
depth, latitude, and sediment total organic carbon (TOC)
concentration. These relationships were determined
using data from the reference stations only to avoid the
potentially confounding effects of stressors (e.g.,
contaminants and low dissolved oxygen) known to occur
at the degraded sites.
Many of the candidate benthic measures were significantly
(p<0.05) correlated with at least one of the habitat factors
measured (Table B-5). However, only five of the correlations
accounted for a significant proportion of the total variation,
defined here as more than 25%. Four of these five were
measures of species richness (both total number of infaunal
species per event and mean number of infaunal species
per grab), which were both positively correlated with
bottom salinity and negatively correlated with TOC.
The fifth correlation was a positive one between the mean
abundance of equilibrium species and bottom salinity.
Relationships between the rest of the candidate measures
and the other habitat factors (i.e., latitude, silt-clay content
of sediments, and water depth) occurred less frequently
and did not account for as much of the total variation
as relationships with salinity and TOC (Table B-5).
A three dimensional plot of the mean number of benthic
infaunal species per grab versus salinity and TOC was
generated, and a quadratic response surface model was
fit to predict the "expected" number of infaunal species:
Expected number of species =
8.25 + (0.000387 (TOC))
- (1.9x10-*)(TOC))2)
+ (0.784 (salinity)) - (0.00125 (salinity)2)
- (0.00002031 (TOC) (salinity)).
The "expected" number of species calculated
from this relationship (r2 = 0.61) is presumed to
represent the baseline (i.e., reference) response
of benthos to estuarine gradients in salinity and
TOC in the absence of known stressors (e.g., chemical
contaminants and low dissolved oxygen conditions).
An adjusted measure of species richness was then
determined for each station by calculating the percent
deviation in the mean number of infaunal species
per grab from this baseline condition. This adjusted
measurement was termed the percent expected
number of species:
number of species present
expected number of species
x 100
Statistical Summary, EMAP-E Virginian Province - 1991
Page B-3
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Table B-2. List of degraded stations from 1990 or 1991 used in reconstructing the benthic index.
Habitat Class
Low salinity
(<5ppl)
Brackish
(5-18 ppl)
Esluarine
(>18ppt}
Degraded Stations
Low Dissolved Oxygen
Stress
None
Chesapeake Bay (OB2)
38°59'12' 76'21'29~
Chesapeake Bay (065)
38*33'27" 76'24'05'
Potomac River (180)
3S'04'13' 76'27'53'
Potomac River (182)
38'13'06' 76'47'08'
Breton Bay (306)
38°13'41" 76'41'48'
Breton Bay (312)
38'15'22' 76'39'39'
Chesapeake Bay (325)
38'37'29' 76'27'52'
Chesapeake Bay (282)
37'39>02' 76°12W
Chesapeake Bay (056)
38'08'40" 76'14'OS"
Chesapeake Bay (080)
38'53'23' 76°24'04"
Contaminant Stress
Houstatonic River (169)
4ri7'12' 73°04'19'
Delaware River (223) •
39°45'00" 75'29W
Susquehanna River (351)
39°34'41' 76°05'29'
Delaware River (365)
40°06'04" 74°50'11'
Colgate Cove (082)
39'15'12' 76"33'06"
-Arthur Kill (094)
40°37'18" 74°12'12'
Raritan Bay (260)
40°42'17" 74°06'59"
Raritan River (369)
40°30'40" 74°18W
Kill Van Kull (373)
40'38'52' 74°04'29"
Flushing Bay (375)
40°46W 73'51'19"
Flushing Bay (377)
40"47'31' 73'51'41"
East River (378)
40'47'3r 73°55'54'
Taunton River (419)
41'42'38' 7r09'49"
Taunton River (421)
4r46'00' 71°07'23'
Low Dissolved Oxygen and
Contaminant Stress
Anacostia River (088)
38°52'11" 76°59'51'
Bear Creek (081)
39°14'36" 76°29'29"
Patapsco River (134)
39°14'47' 76'33'25"
Passaic River (103)
40°45W 74'09'54'
Elizabeth River (086)
36°49'S5' 76°17'38"
Blackrock Harbor (098)
41° 09'35- 73*1 2'37'
New Bedford Harbor (099)
41°38'33" 70°54'42'
-
Page B- 4
Statistical Summary, EMAP-E Virginian Province - 1991
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Table B-3. List of reference stations from 1990 and 1991 used to reconstruct the benthic index.
Data from both 1990 and 1991 were used for LIT stations 188 and 150.
Habitat Class
Low Salinity
(18ppt)
_
Reference Stations
Hudson River (101)
41°23'00" 73'57'23"
Rappahannock River (192)
37'57'54- 76°52'30'
Elk River (254)
39°28'47" 75'56'30"
James River (269)
37°09'48' 76°37'43"
Chesapeake Bay (058)
39°07'45' 76°16'53"
Chesapeake Bay (339)
39°03'14" 76°25'16"
St. Clements Bay (314)
38°16'53' 76°42'39'
Rappahannock River (288)
37°49'53" 76°44'49"
Barnegat Bay (256)
39'56'36' 74°06'07'
Tangier Sound (285)
37°48'53' 75°55'25"
Delaware Bay (342)
39°09'30" 74°56'16"
Back River (266)
37°05'53" 76°20'00"
Chesapeake Bay (283)
37°39'59" 76°00'26"
Chesapeake Bay (270)
37°13'16" 76°15'19'
Chincoteague Bay (305)
38°13'24' 75°13'02'
Great Bay (349)
39'30'13" 74°23'05'
Delaware Bay (338)
39°00'40' 75'01'34'
Delaware Bay (033)
39'12'36' 7S'12'43'
Potomac River (188)
38°44'12* 77"02'00"
Delaware River (358)
39°50'05" 75'21'03'
James River (273)
37°14'26" 76°57'18"
Wye River (336)
38°54'22' 76°10'15"
Fishing Bay (317)
38°18'55" 76°01'11'
Little Choptank River (322)
38°31'10' 76°16'07"
Tangier Sound (041)
38°01'41" 75°54'06"
Chesapeake Bay (291)
37°55'53" 76°15'22'
Chesapeake Bay (265)
37°05'20" 76'07'54'
Long Island Sound (386)
41°05'26" 73°05'04"
Jamaica Bay (371)
40°36'57' 73'53'15"
Long Island Sound (388)
41°06'30' 72°38'43"
Rehobeth Bay (328)
38°40'29" 75'07'OS'
Indian River Bay (150)
38'35'36' 75°06'42'
Niantic River (405)
4r20'35' 72°10'45"
Napeague Bay (159)
41°03'42" 72°00'06'
Delaware Bay (335)
38'51'50' 75°06'50"
Block Island Sound (390)
41'07'53' 71'59'08'
Hudson River (424)
42°08'00" 73°54'26"
Potomac River (333)
38°51'32" 77°02'03"
Potomac River (326)
38°37'30' 77°09'43"
Honga River (316)
38°18'13' 76°11'0r
Chesapeake Bay (057)
37°26'04' 76°14'07'
Chesapeake Bay (307)
38°13'41' 76°05'18"
Delaware Bay (344)
39°16'41" 75°16'28'
Narragansett Bay (070)
41°38'29" 7ri8'01"
Nantucket Sound (402)
41°18'58' 70°07'05"
Westport River (413)
41°31'49' 71°05W
Vineyard Sound (407)
4r26'46" 70°40'43"
Buzzards Bay (406)
41'26'30m 70°54'00"
Nantucket Sound (408)
. 41 °27'01- 70°27'25-
Buzzards Bay (414)
41°35'02' 70'47'48'
Nantucket Harbor (404)
41°20'00" 70°01W
Statistical Summary, EMAP-E Virginian Province - 1991
Page B- 5
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Table B-4. Candidate benthic measures used to formulate the benthic index. T-tests were used to test
equality of the means for each metric for degraded versus reference (nondegraded) sites.
Candidate metrics
Measures of Biodiversity
Shonnon-We/ner fndex
Proportion of expected # of species
Measures of Community Condition
Total benthic biomass per station
Mean biomass per grab
Total intaunal abundance for station
Mean Intaunal abundance per grab
Total tl of intaunal species/station
Mean H of Inlaunal species/grab
Total tl of epilaunal species/station
Mean epifaunal abundance per grab
Mean # of epifaunal species/grab
Measures of Individual Health
Bhmass/abundance ratio
Weight per Individual polychaete
Weight per Individual mollusc
Weight per individual bivalve
Measures of Functional Groups
Suspension feeding species abundance
Deposit feeding species abundance
Omnivore /predator species abundance
Opportunistic species abundance
Equilibrium species abundance
Measures of Taxonomlc Composition
Amphipod abundance
Bivalve abundance
Gastropod abundance
Molluscan abundance
Polychaete abundance
Copitellld polychaete abundance
Spionid polychaete abundance
Tubilicid otigochaete abundance.
t-test
(p-value)
< 0.00 1
< 0.00!
0.87
0.87
0.48
0.48
< 0.001
< 0.001
< 0.001
0.07
< 0.00!
0.04
0.84
0.10
0.06
0.55
0.37
< 0.001
0.06
0.001
0.87
0.32
< 0.00 1
0.43
0.22
0.34
0.28
0.34
Direction
(+ = greater mean value at
reference sites)
I
+
+
+
+
Page B- 6
Statistical Summary, EMAP-E Virginian Province - 1991
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Table B-5. Summary of correlation between habitat indicators and the candidate benthic measures.
Habitat Indicator
Salinity (ppt)
Latitude
Silt-clay Content
Water Depth
Total organic carbon
Number of Significant
Correlations
16
4
8
8
10
Number of
Correlations with
r2 > 0.10
15
2
7
4
8
Number of
Correlations with
r2 > 0.25
3
0
0
0
2
Step 3: Identify combinations of candidate benthic
measures that discriminate between degraded
and nondegraded areas
A series,^of discriminant analyses were run in
succession to identify the benthic measures from Table
B-4 which best discriminated between the degraded and
nondegraded stations in the test data set. In some
instances, the variable selection process included an
initial t-test (assuming unequal variances) to eliminate
any variables not having significantly different means
(t-test at p < 0.2) at degraded versus nondegraded
stations (Table B-4). In other instances, the t-test was
not performed, and all variables were used in a stepwise
discriminant analysis. In addition, discriminant analyses
were performed using both untransformed and selected
transformed variables (e.g., log]0 transformed species
abundance variables), as we'll as both unadjusted and
adjusted measures of species richness (adjusted for the
effects of salinity and TOC).
The results of the various discriminant analyses are
summarized in Table B-6. Three variables were
included in the model generated by the first stepwise
discriminant analysis (Index 1): 1) mean abundance of
opportunistic species, 2) biomass/abundance ratio for
all species collected at a site, and 3) the mean number
of infaunal species. This combination of measures
correctly classified 84% of the degraded sites and 85%
of the nondegraded reference sites (Table B-6), using
the cross-validation procedure of the discriminant
analysis. The canonical r2, which approximates the total
variance explained by this analysis, was 0.40.
Certain variables were eliminated as a result of performing
the t-test prior to running the first stepwise discriminant
analysis. When the same analysis was run without first
performing a t-test, two additional measures were selected
(Index 2): 1) weight of individual polychaetes, and 2)
mean abundance of capitellids. This combination of measures
resulted in a slightly better canonical r2 (0.44), but the
rate of correct classification for degraded stations decreased
to 77% (two fewer stations correctly classified) while
the rate for reference stations remained unchanged.
In the third discriminant analysis, salinity and TOC-
adjusted measures of species richness (percent of the
expected mean number of species) were used in place
of the unadjusted values. Five measures were selected
in this model (Index 3): 1) Shannon-Weiner diversity
index, 2) mean abundance of spionids, 3) mean abundance
of equilibrium species, 4) mean abundance of tubificids,
and 5) mean weight of individual bivalves. This model
correctly classified 61% of the degraded stations and
89% of the reference stations, with a canonical r2 of 0.43.
The failure of the adjusted species richness measure
(TOC/salinity adjustement) to appear in indices 1 and
2, indicates that it was less effective at discriminating
between degraded and reference conditions than the unadjusted
measure. To verify this, the percent of expected mean
number of species was forced into Index 1 in place of
the unadjusted mean number of infaunal species. This
resulted in a lower rate of correct classification for degraded
stations (74%) and a marginally improved rate of classification
for reference stations (87%) compared to the original
Index 1. The canonical r2 for this model was 0.42. The
Statistical Summary, EMAP-E Virginian Province - 1991
Page B- 7
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to
oo
Table B-6. Results of discriminant analyses conducted to combine candidate benthic measures into an index.
Analysis
Index 1
• t-test on raw variables
• step-wise discriminant analysis
• no variables forced
Index 2
• no t-test
• raw variables
• step-wise discriminant analysis
• no variables forced
Index 3
• species richness adjusted for salinity/TOC
• unadjusted species richness variables
removed
• no t-test
• step-wise discriminant analysis
• no variables forced
• raw variables used
Index 4
• no t-test
• Iog10 transform all species abundance
variables except total infaunal abundance
• step-wise discriminant analysis
• no variables forced
Index 5
• log,0 transform all variables
» no t-test
• step-wise discriminant analysis
• no variables forced
Selected Measures
• Mean abundance of opportunistic species
• Biomass/abundance ratio, all species
• Mean number of infaunal species
• Mean abundance of opportunistic species
• Biomass/abundance ratio, all species
• Mean number of infaunal species
• Weight of individual polychaetes
• Mean abundance of capitellids
• Shannon-Weiner diversity index
• Mean abundance of spionids
• Mean abundance of equilibrium species
• Mean abundance of tubificids
• Mean weight of individual bivalves
• Mean amphipod abundance
• Mean abundance of equilibrium species
• Mean weight of individual polychaetes
• Total infaunal abundance
• Mean abundance of opportunistic species
• Mean abundance of amphipods
• Mean abundance of tubificids
• Mean weight of individual bivalves
• Mean weight of individual molluscs
• Mean number of infaunal species
Cross-validation
Efficiency
Percent of Degrad-
ed Sites Correctly
Classified
84%
77%
61%
77%
67%
Percent of Refer-
ence Sites
Correctly Classified
85%
85%
89%
91%
92%
Canonical RJ
0,40
0.44
0.43
0.59
0.53
I
.on
I
3
D
i
-------
net result of using the adjusted species richness measure
in place of the unadjusted one was to misclassify an
additional degraded site and correctly classify one
additional reference site, with an almost negligible
increase in the canonical r2.
During the development of the benthic index in
1990, a log]0 (value + 1) transformation was applied to
some of the measures to make their distributions normal
and variances homogenous. Although transforming
individual variables to achieve normality does not imply
that the multivariate distribution used in discriminant
analysis will be "multivariate normal", the Iog10 (value
+ 1) transformation was applied, with one exception,
to all species abundance data prior to the analysis for
Index 4 (Table B-6). Due to an oversight, the log
transformation was not applied to the total infaunal
abundance measure. Four measures were selected in
this model (Index 4): 1) mean amphipod abundance, 2)
mean abundance of equilibrium species, 3) mean weight
of individual polychaetes, and 4) total infaunal
abundance. This model correctly classified 77% of the
degraded stations and 91% of the reference stations,
with a canonical r2 of 0.59.
The model used in Index 4 explained significantly
more of the total variation than any other model (i.e.,
highest canonical r2), and it correctly classified three
more reference stations, but two fewer degraded stations,
compared to Index 1. When the mistake discussed
above was corrected and all abundance variables were
log-transformed, the resultant model included the
following variables: 1) Shannon-Weiner diversity index,
2) mean abundance of amphipods, 3) mean abundance
of opportunistic species, 4) total infaunal abundance,
5) mean weight of individual bivalves, and 6) mean
abundance of gastropods. This "corrected" model
correctly classified 74% of degraded stations and 87%
of reference stations, with a canonical r2 of 0.50.
For Index 5 (Table B-6), all of the candidate
variables were log,0 (value + 1) transformed and the
following were selected: 1) mean abundance of
opportunistic species, 2) mean abundance of amphipods,
3) mean abundance of tubificids, 4) mean weight of
individual bivalves, 5) mean weight of individual
molluscs, and 6) mean number of infaunal species. This
model correctly classified 67% of degraded stations and
92% of the reference stations, with a canonical r2 of
0.53.
Step 4: Validating the model
Five potential indices were examined in step 3. The Virginian
Province benthic data from the 1992 sampling season,
which represents an independent data set, will be used
in the future to provide a true validation of each of these
indices, In the absence of this independent validation,
the discriminant analysis cross-validation procedure was
used to determine the rates of correct classification presented
in Table B-6. In this process one individual station is
removed from the test dataset, the indices recalculated,
and the station removed from the test dataset reclassified
according to the new index. This process is repeated
for each station in the original test dataset. The overall
rate of correct classification, based on the cross-validation
procedure, were 85%, 82%, 79%, 86% and 83% for the
five candidate benthic indices, respectively.
Step 5: Scaling the index
The final step in developing the benthic index was
to select one of the indices based on the calibration and
validation information, calculate canonical discriminant
scores for all sample sites, and adjust the scores to result
in a critical value of zero. Although all five candidate
indices were cross-validated at an acceptable level (i.e.,
about 80% overall correct classification), the first alternative
(Index 1 in Table B-6) was used to assess the status of
benthic resources of the Virginian Province for the combined
1990-91 data set. The discriminant function for this index
was:
Discriminant Score =
-0.68 * Mean abundance of opportunistic species
+ 0.36 * Biomass/abundance ratio for all species
+ 1.14* Mean number infaunal species per grab.
When applied to all 392 sites sampled in the Virginian
Province in 1990 and 1991, the range in canonical discriminant
scores for this index was -7.78 to +6.33, with a critical
value for discriminating between degraded and reference
sites of-0.5 (calculated as the point giving the optimal
correct classification efficiency for both reference and
degraded sites). A value of 0.5 was then added to all
scores to result in a critical value of zero, i.e., a negative
score indicated degraded conditions. An offset was selected
in place of a scaling factor (i.e., scaling from 0 to 10),
Statistical Summary, EMAP-E Virginian Province - 1991
Page B- 9
-------
because a scaling factor requires recalculation every year
resulting in a new critical value each year. An offset
is not affected by the range of values, therefore, the
critical value will remain constant between years.
B.4 DISCUSSION OF THE BENTHIC INDEX
Although only five candidate indices were presented
in Table B-6, it is important to note that many variations
of these indices were examined in an attempt to find
the best model. These efforts revealed that for the
1990-91 data set, optimization of the model represented
a "trade-off among three competing factors: 1)
classification efficiency, 2) statistical robustness (as
expressed by the canonical r2), and 3)
complexity/ecological relevance. Essentially, it was
found that increases in the canonical r2, which reflect
increased ability of the model to explain variation, were
accompanied by concomitant decreases in classification
efficiency and increases in the complexity of the model.
Complexity is defined here to be a direct function of
the number of variables used, with models based on
fewer variables being more desirable because
presumably they are easier to comprehend and
appreciate. The concept of "ecological relevance" also
is important in this context, in that the variables chosen
for the index should conform at least to some degree
with currently accepted scientific knowledge about the
response of benthic communities to stress. A quick
check on whether a discriminant function is plausible
is to examine the signs of the coefficients. The sign
on a coefficient should make sense in ecological terms,
i.e., we would expect to find a greater number of species
at a reference station than at a degraded site, therefore,
we would expect a "+" coefficient.
Although Index 4 had the best overall rate of correct
classification, it correctly classified fewer degraded
stations than Index 1 and is more difficult to justify in
ecological terms. Although it had the lowest canonical
r2 value, Index 1 had the second best overall
classification efficiency and the highest rate of correct
classification for degraded stations. This index also is
the least complex of all the candidate indices, and was
appealing from an "ecological relevance" standpoint in
that it is comprised of one measure of individual health
(biomass/abundance ratio), one measure of functionality
(abundance of opportunists), and one measure of
community condition (mean number of infaunal species).
The signs of the discriminant coefficients are also ecologically
interpretable for Index 1. Higher values for mean number
of infaunal species and the biomass/abundance ratio can
be defended as being associated with healthy conditions
(positive coefficient), and an increase in the abundance
of opportunistic organisms at degraded sites (negative
coefficient) is consistent with ecological theory.
Compared to Index 1, the second, third and fifth indices
had better canonical r2 values and better rates of classification
for reference stations. This suggests that they were better
able to explain the variation present at the reference sites.
However, all three indices had slightly worse classification
efficiencies for the degraded stations and were more complex.
Therefore, Index 1 was selected as the best index.
Page B - 10
Statistical Summary, EMAP-E Virginian Province - 1991
-------
APPENDIX C
SUB-POPULATION ESTIMATES FOR CHESAPEAKE BAY
AND LONG ISLAND SOUND
The two largest systems within the Virginian
Province are Chesapeake Bay (11,469 km2) and Long
Island Sound (3,344 km2). Combined these two systems
represent 63% of the surface area of the entire Province.
Because of their size, and therefore the number of
sampling locations in each, estimates of ecological
condition of these systems are possible using the EMAP
design. However, the level of uncertainty will remain
higher than for estimates for the Province as a whole
or individual classes.
This appendix provides the tools for generating these
estimates, i.e., data for these two systems are
summarized using CDFs and bar charts. Each system
is defined as including all adjacent tributaries and small
systems. For example, the data set for Chesapeake Bay
includes the Potomac, James, and Rappahannock Rivers,
and all the small systems connecting to the mainstem
of the Bay. Since the Long Island Sound data set
contains no large tidal rivers and fewer small systems
than Chesapeake Bay, this may account for some of the
differences observed between these two systems. Fifty
one stations are included in the Chesapeake Bay data
set and 14 in the Long Island Sound data set.
C.I Biotic Condition Indicators
C.I.I Benthic Index
CDFs for the benthic index are illustrated in Figure
C-l. Approximately 16 ± 10% of the sampled area of
Chesapeake Bay produced a benthic index value below
zero, and the corresponding area of Long Island Sound
was 14 ± 21%.
C.I.2 Number of Benthic Species
The mean number of species collected per grab at
each station, as percent area in these systems, is illustrated
in Figure C-2. The distribution and maximum (42 and
44 species) values are similar for Chesapeake Bay and
Long Island Sound, respectively.
C.I.3 Total Benthic Infauna Abundance
Figure C-3 shows the distribution of total number
of benthic individuals per m2 measured in Chesapeake
Bay and Long Island Sound. The maximum number
of individuals collected at a station was higher in the
Sound than in the Bay (13,992 and 8,561, respectively).
C.I.4 Number of Fish Species
The number of fish species collected per standard
trawl is shown in Figure C-4. Between 0 and 7 species
the distributions are similar, however the maximum number
if individuals caught at a station was approximately double
in Chesapeake Bay what it was in Long Island Sound
(15 and 7, respectively).
C.I.5 Total Finflsh Abundance
The total number offish captured per standard trawl
(catch per unit effort) was greater at Chesapeake Bay
stations than Long Island Sound stations (Figure C-5).
The maximum catch in the Bay was 650 individuals,
whereas, no more than 69 were collected at any station
in Long Island Sound. This is presumably due to habitat
and cannot be related to man's impact.
Statistical Summary, EMAP-E Virginian Province - 1991
Page C-l
-------
Chesapeake Bay
3 4
Benthic Index
Long Island Sound
015345678
Efehthic Index
Figure Ci-1, Cumulative distribution functions of berithic index as a pWcent of area of
Chesapeake Bay arid Long Island Sound, 1991. (Dashed lines are the 95% confidence intervals).
Page C - 2
Statistical Summary, EMAP'^E Virginian Province - 1991
-------
Chesapeake Bay
10
15 20 25 30 35
Benthic Species (Mean # per Grab)
40
45
50
120 T
Long Island Sound
10 20 30
Benthic Species (Mean # per Grab)
40
50
Figure C-2. Cumulative distribution functions of the mean number of benthic invertebrate species
collected per grab as a percent of area of Chesapeake Bay and Long Island Sound, 1991.
(Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 3
-------
Chesapeake Bay
1000 2000 3000 4000 5000 6000
Total Benthic Abundance (#/rrf)
7000 8000 9000
120 T
Long Island Sound
2000
4000
6000
8000
10000
12000
14000
Figure C-3. Cumulative distribution functions of the number of benthic invertebrates collected per
m* as a percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the
95% confidence intervals).
Page C- 4
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Chesapeake Bay
6 8 10
Number of Fish Species per Trawl
12
14
16
120 T
Long Island Sound
6 8 10
Number of Fish Species per Trawl
12
14
16
Figure C-4. Cumulative distribution functions of the number offish species collected in standard
trawls as a percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines, are
the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 5
-------
Chesapeake Bay
100 200 300 400 500
Number of Pish per Trawl
600
700
Long Island Sound
100 200 300 400 500
Number of Fish per Trawl
600
700
Figure C-5. Cumulative distribution functions of the number of fish caught per standard trawl as
a percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95% .
confidence intervals).
Page C - 6
Statistical Summary, EMAP-E Virginian Province - 1991
-------
C.I.6 Fish Gross External Pathology
C.2 Abiotic Condition Indicators
All target species were examined for evidence of
gross external pathologies. The rate of pathologies in
Chesapeake Bay and Long Island Sound were similar,
however, only 159 fish were collected and examined
in Long Island Sound compared to 1,265 in Chesapeake
Bay (Table C-l).
C.I. 7 Fish Tissue Contamination
As discussed in Section 3, no composite samples
analyzed contained organic contaminants in excess of
stated action limits. Of the 41 composites analyzed
from Chesapeake Bay, 10% exceeded the mean
international action limit of 2 ug/g wet weight for
arsenic. All four composites were spot and atlantic
croaker. In Long Island Sound, 44% of the nine
composites exceeded the arsenic limit, and all six
composites were winter flounder.
C.2.1 Instantaneous Dissolved Oxygen
Concentration
CDFs for bottom dissolved oxygen concentration
in Chesapeake Bay and Long Island Sound are shown
in Figure C-6. The percent of sampled area of Chesapeake
Bay with severely hypoxic water (DO <2 mg/1) was similar
that of Long Island Sound (7 ± 9% and 10 db 20%,
respectively). Approximately 44 ± 32% of the Sound
was marginal, with DO values less than 5 mg/L (compared
to 20 ± 13% for the Bay).
Table C-1. Incidence of gross external pathology for Chesapeake Bay and Long Island Sound observed by
field crews among target fish species in 1991.
Lumps
Growths
Ulcers
Fin Rot
Total
Chesapeake Bay
Frequency
Total # Fish Examined
Percent Incidence
Number Stations
Represented
1
1,265
0.08%
0
1,265
0%
9
1,265
0.71%
2
1,265
0.16%
1,265
0.87%
Long Island Sound
Frequency 0
Total # Fish Examined 159
Percent Incidence 0%
Number Stations
Represented
0 01 1
159 159 159 159
0% 0% 0.63% 0.63%
1
one fish was found with two pathologies, therefore 12 pathologies were identified on 11 fish.
Statistical Summary, EMAP-E Virginian Province - 1991
Page C- 7
-------
Chesapeake Bay
3456
Dissolved Oxygen (mg/L)
Long Island Sound
120-
100-
80 -•
60 •
& 40 +
20 ••
0123456789
Dissolved Oxygen (mg/L)
Figure C-6. Cumulative distribution functions of bottom dissolved oxygen concentration as a
percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95%
confidence intervals).
Page C - 8
Statistical Summary, EMAP-E Virginian Province - 1991
-------
C.2.2 Dissolved Oxygen Stratification
C.2.6 Marine Debris
The difference in measured DO concentrations at
the bottom compared with surface measurements taken
at those same stations are illustrated in Figure C-7. No
significant differences are shown by these graphs.
C.2.3 Sediment Toxicity
Sediments were classified as toxic if amphipod
survival in the test sediment was less than 80% of that
in the control sediment, and significantly different.
Approximately 20 ± 13% and 23 ± 30% of the area of
Chesapeake Bay and Long Island Sound respectively
exhibited toxic sediments (Figure C-8).
C.2.4 Sediment Contaminants - Organics
Draft EPA Sediment Quality Criteria (SQC)~ exist
for four compounds for which EMAP is monitoring:
Acenaphthene, phenanthrene, fluoranthene, and dieldrin.
One station at the mouth of Chesapeake Bay exceeded
the SQC for all three PAHs; however, as discussed in
Section 3, this is believed to be due to contamination
of the sample. No other station in Chesapeake Bay or
Long Island Sound exceeded any of the SQCs.
CDFs for combined PAHs are presented in Figure
C-9. Although the maximum concentration measured
was higher in Long Island Sound than Chesapeake Bay
(22,700 and 4,091 ng/g dry weight, respectively), the
distributions are similar with 96 ± 6% of the sampled
area of Long Island Sound containing concentrations
less than 4,000 ng/g compared to 94 ± 11% for
Chesapeake Bay.
C.2.5 Sediment Contaminants - Metals
Table C-2 lists minimum, maximum, and median
bulk sediment concentrations of metals measured in
Chesapeake Bay and Long Island Sound in 1991.
Median values for all metals were higher in Long Island
Sound than in Chesapeake Bay.
The incidence of trash collected in trawls is illustrated
in Figure C-10. The incidence for both systems was
low: trash was found in 15 ± 13% and 1 ± 1% of the
area of Chesapeake Bay and Long Island Sound, respectively.
The differences between the two systems may be due
to the larger number of small estuary and tidal river stations
included within the Chesapeake Bay system.
C.3 Habitat Indicators
C.3.1 Light Extinction (Water Clarity)
Water clarity, as defined by human vision, showed
definite differences between Chesapeake Bay and Long
Island Sound. All of the water of Long Island Sound
was classified as "good" relative to clarity based on EMAP
sampling (Figure C-l 1). Approximately 26 ± 11% of
the water of Chesapeake Bay was classified as poor or
marginal (lightextinction coefficient^ 1.387), meaning
that a wader could not see his/her toes in waste deep
water.
C.3.2 Water Depth
Cumulative distribution functions for water depth
in Chesapeake Bay and Long Island Sound are presented
in Figure C-12. The Bay is generally much shallower
than Long Island Sound. The maximum depths measured
in the two systems in 1991 were 22 and 30 m, respectively.
The area shallower than 2 m is underestimated because
this is the minimum depth sampled, and, because of the
statistical design, unsampleable areas were distributed
across the CDF as missing^values.
C.3.3 Temperature
The CDFs for bottom water temperature in Chesapeake
Bay and Long Island Sound show the Sound to generally
contain lower temperature bottom waters than Chesapeake
Bay (Figure C-l3). This is most likely a function of
both water depth and latitude.
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 9
-------
Chesapeake Bay
345
Dissolved Oxygen Difference (mg/L)
Long Island Sound
012345
Dissolved Oxygen Difference (mg/L)
Figure C-7. Cumulative distribution functions of the DO difference between surface and bottom
waters as a percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are
the 95% confidence intervals).
Page C - 10
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Chesapeake Bay
40
50 60 70 80
Mean Amphipod Survival (% of Control)
90
100
120 T
30
Long Island Sound
40
50 60 70 . 80
Mean Amphipod Survival (% of Control)
100
Figure C-8. Cumulative distribution functions of amphipod survival (% of control) in 10-day
toxicity tests as a percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed
lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 11
-------
Chesapeake Bay
10 15
Combined PAHs (ng/g dry wt x 1000)
20
25
Long Island Sound
10 15
Combined PAHs (ng/g dry wt x 1000)
20
25
Figure C-9. Cumulative distribution functions of combined PAH concentrations as a percent of
area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95% confidence
intervals).
Page C - 12
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Table C-2. Range and median metal concentrations in sediments Chesapeake Bay and Long Island Sound, 1991. Concentrations
are as ug/g dry weight.
Analyte
Major
Aluminum
Iron
Manganese
Trace
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Silver
Tin
Zinc
Major
Aluminum
Iron
Manganese
Trace
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Silver
Tin
Zinc
MIN
1,760
653 .
11.6
ND
0.773
ND
1.88
0.89
ND
ND
ND
ND
ND
ND
3.66
26,600
8,160
266
0.054
1.21
0.038
9.40
3.10
11.0
0.016
4.63
ND
ND
0.362
22.8
MAX
Chesapeake Bay
89,300
54,500
6,430
1.04
21.1
0.78
105
47.7
274
0.19
50.1
1.76
0.52
6.16
266
Long Island Sound
65,300
40,300
783
1.40
9.43
6.58
174
263
230
1.96
46.2
1.41
9.69
27.0
321
Median
47,700
26,300
364
0.262
5.34
0.188
42.7
17.5
25.1
0.037
22.8
0.434
0.047
2.15
73.9
50,500
29,900
593
0.448
4.90
0.226
76.4
57.5
45.5
0.130
24.0
0.441
0.463
5.69
145
ND = Not Detected
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 13
-------
251
ChesapeakeBay
Long Island Sound
Figure C-10. The incidence of anthropogenic debris in fish trawls as a percent of area of
Chesapeake Bay and Long Island Sound, 1991. (Error bars represent the 95% confidence
intervals).
100 -,
Low
Moderate
Good
Chesapeake Bay
Long Island Sound
Figure C-11. Percent area of Chesapeake Bay and Long Island Sound with water clarity
classified as low, moderate, or good based on light extinction coefficients. (Error bars represent
95% confidence intervals).
Page C - 14
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Chesapeake Bay
15
Depth (m)
Long Island Sound
10
15
Depth (m)
Figure C-12. Cumulative distribution functions of water depth as a percent of area aof
Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95% confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 15
-------
Chesapeake Bay
120 •
100 ••
| 80
1 60-
£ 40 ••
20 •
-t-
-t-
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Temperature (°C)
Long Island Sound
15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
Temperature (°C)
Figure C-13. Cumulative distribution functions of bottom water temperature as a percent of area
of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95% confidence
intervals).
Page C - 16
Statistical Summary, EMAP-E Virginian Province - 1991
-------
C.3.4 Salinity
As described in Section 3, the CDF of salinity in
the Virginian Province for 1991 is bimodal, with the
major inflections (at 17 and 28 %o) being accounted for
by Chesapeake Bay and Long Island Sound respectively.
The combined CDFs for these systems (Figure C-14)
illustrate their different salinity patterns.
Long Island Sound contains predominantly
polyhaline waters (95 ± 5% of the area sample), with
a low salinity tail which is accounted for by one station
in the Connecticut River (a small estuary). Chesapeake
Bay, because of the inclusion of three major tidal rivers
as well as the Susquehanna River, contains a significant
area of oligohaline and mesohaline water (64 ± 17% of
the area sampled).
C.3.5 Stratification
Stratification is shown as CDFs of Aat, which is the
at (sigma-t density) difference between surface and
bottom waters (Figure C-15).
The greatest stratification in the Province occurred
in the lower portion of the Chesapeake Bay.
Chesapeake Bay had both the highest area of well-mixed
water (CTt < 1), and the highest area of significantly
stratified water (0t>2). Most of Long Island Sound fell
between at's of 1 and 2.
C.3.6 Percent Silt-Clay Content
The CDFs of silt-clay content for Chesapeake Bay
and Long Island Sound are similar with approximately
the same percent area of mud and sand in each system
(Fig. C-16).
The large area of sandy sediments found in the
mouth of the Bay is likely due to sands being carried
in from the ocean (Hobbs etal., 1992). In Long Island
Sound coarser sediments at the mouth are mainly a
result of strong tidal currents transporting away the fine
fraction (winnowing), leaving behind the coarser sands
and gravel (Akapati, 1974; Gordon, 1980).
Statistical Summary, EMAP-E Virginian Province - 1991 Page C - 17
-------
Chesapeake Bay
10
15 20
Salinity (%o)
25
Long Island Sound
120-
100--
I 8°"
| 60-
(£40-
20 ••
10
15 20
Salinity (%o)
35
Figure C-14- Cumulative distribution functions of bottom water salinity as a percent of area of
Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95% confidence intervals).
Page C - 18
Statistical Summary, EMAP-E Virginian Province * 1991
-------
Chesapeake Bay
ACT (kg/m3)
Long Island Sound
Figure C-15. Cumulative distribution functions of surface to bottom sigma-t density difference as
a percent of area of Chesapeake Bay and Long Island Sound, 1991. (Dashed lines are the 95%
confidence intervals).
Statistical Summary, EMAP-E Virginian Province - 1991
Page C - 19
-------
Chesapeake Bay
20.
30
40. 501 6O
Silt/Clay (%}
80.
90
100:
120 T
Long Isfand Sound
20
30
40 50 60
Sill/ Clay (%)
70
80
90
100
Figure C-16. Cumulative distribution functions of sediment silt/clay content as a percent of area
of Chesapeake Bay and Long Island .Sound, 1.991. (Dashed lines are the 95% confidence
interval).
Page C - 20
Statistical Summary, EMAP-E Virginian Province - 1991
-------
APPENDIX D
LINEAR REGRESSIONS OF INDIVIDUAL METALS
AGAINST ALUMINUM USED IN THE DETERMINATION
OF METALS ENRICHMENT OF SEDIMENTS OF THE
VIRGINIAN PROVINCE
As discussed in Section 3.2.3.7, concentrations of
individual metals were normalized against the crustal
element aluminum in an attempt to provide a basis for
estimating the areal extent of enrichment of these metals
in Virginian Province sediments. The method utilized
is described in Appendix A (Section A.8.2.3). For each
metal, a regression and an upper 95% confidence
interval was determined and plotted (Figures D-l to D-
14). Stations with concentrations falling above the
upper 95% confidence interval were classified as
enriched for that metal. Regression parameters (slope,
intercept, and correlation coefficient) are listed in Table
D-l.
The results obtained from the regression analyses
should be similar to those obtained by other investi-
gators using the same approach. For most of the metals
analyzed in the Virginian Province 1991 samples, the
results agree exceptionally well with those of Hanson
et al. (1993) (Table D-l). Correlations between metals
and aluminum in 1991 Virginian Province sediments,
as measured by the r2 values obtained, are comparable
to those determined from Atlantic and Gulf of Mexico
estuarine and coastal sediments collected between 1984
and 1987 by Hanson et al. (1993). For eight of the 13
elements analyzed (Hg, Ag, As, Cr, Ni, Sn, Mn and Fe),
slopes of the regression lines agree within 50%, while
those obtained for other metals (Cu, Cd, Pb, Zn and Se)
are 2-3 times higher than found by Hanson et al. (1993).
In addition, Hanson found statistically significant non-
zero intercepts for Ag, Cd, Cr and Pb, indicating sig-
nificant concentrations of the metals in the silica end-
member of the mixing model, or the widespread in-
troduction of metals to all samples within the region samples,
e.g., atmospheric deposition of lead. In contrast, none
of the intercepts determined from the metal-aluminum
regressions in this work are statistically significant.
Agreement between this work and the results of Windom
et al. (1989) is not as good, but in that study, fewer metals
were determined and samples were collected from more
limited geographical regions.
Statistical Summary, EMAP-E Virginian Province - 1991
Page D - 1
-------
12
10 -
8 •
Ag 6 •
4 •
2 -
.
•
•
• *
02468
AL (%)
Figure D-1. Linear regression of silver against aluminum (dashed line is the upper 95% confidence
Interval). Metal concentrations are as ug/g dry weight.
As
35
30 H
25
20 •
15-
10
5
0
AL (%)
Figure D-2. Linear regression of arsenic against aluminum (dashed line is the upper 95% confidence
Interval). Metal concentrations are as ug/g dry weight.
Page D-2
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Cd
7
6 i
5
4
I
3
2 •
1
AL (%)
Figure D-3. Linear regression of cadmium against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Cr
180 -
160 -
140 -
120 -
100 -
80 -
60 -
40 -
20
0
02468
AL (%)
Figure D-4. Linear regression of chromium against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Statistical Summary, EMAP-E Virginian Province - 1991
Page D - 3
-------
300 i
250
200
Cu150 •
100 •
Figure D-5. Linear regression of copper against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
60000 i
50000
40000
Fe 30000
20000
10000 ^
0
02468
AL (%)
Figure D-6. Linear regression of iron against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Page D - 4
Statistical Summary, EMAP-E Virginian Province - 1991
-------
Hg1
Figure D-7. Linear regression of mercury against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Mn
7000 n
6000
5000 ^
4000
3000 •
2000
1000 -
0
Figure D-8. Linear regression of manganese against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Statistical Summary, EMAP-E Virginian Province - 1991
Page D - 5
-------
80
60
N140
20
02468
AL (%)
Figure D-9. Linear regression of nickel against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Pb
350
300
250
200 H
150
100-
50 •
0
6
8
024
AL (%)
Figure D-10. Linear regression of lead against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Page D - 6
Statistical Summary, EMAP-E Virginian Province - 1991
-------
50
45
40
35
30
Sb25 •
20
15
10
5
0 •
(
„_.... ^....- ^.. -«.~- - „.., - .^.*tj -r-;
) 24'6 8
AL(%)
Figure D-11. Linear regression of antimony against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Se1
4
AL (%)
6
Figure D-12. Linear regression of selenium against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Statistical Summary, EMAP-E Virginian Province - 1991
Page D - 7
-------
30
25 •
20 •
Sn15
10
5 i
AL (%)
Figure D-13. Linear regression of tin against aluminum (dashed line is the upper 95% confidence
Interval). Metal concentrations are as ug/g dry weight.
Zn
500
400
300 -I
200
100 -
0
02468
AL (%)
Figure D-14. Linear regression of zinc against aluminum (dashed line is the upper 95% confidence
interval). Metal concentrations are as ug/g dry weight.
Page D - 8
Statistical Summary, EMAP-E Virginian Province - 1991
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Table D-1. Comparison of metal-aluminum regression parameters obtained from 1991 Virginian Province sediment
data and values reported in the scientific literature (m = slope, b = intercept, r2 = correlation coefficient).
Element
Ag
As
Cd
Cr
Cu
Fe
Hg
Mn
Ni
Pb
References
EMAP Va. Prov. - 1991
Hanson et al., 1993
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989 *
EMAP Va. Prov. - 1991
Hanson et al., 1993
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989 T
EMAP Va. Prov.- 1991
Hanson et al., 1993
Windom et al., 1989 *
Windom et al., 1989 T
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989 *
Windom et al., 1989 T
EMAP Va. Prov. - 1991
Hanson et al., 1993
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989 *
Windom era/., 1989 T
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989*
Windom et al., 1989 *
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989 *
Windom et al., 1989 *
Regression parameters
m
0.0097
0,0085
1.15
1.52
7.50
0.0436
0.0180
10.57
8.13
9.50
5.44
1.98
1.8
2.5
5788
4950
4700
4800
0.0113
0.0113
93.9
90.1
55
46
4.99
3.31
4.4
2.9
5.90
2.99
3.50
3.20
b
0.0101
0.0252
1.12
0.05
-0.70
0.0062
0.0517
-1.38
9.76
4.00
-3.36
-0.23
-1.4
2.2
-1307
-612
-800
700
0.0057
-0.0084
29.3
21.6
57
27
-2.62
-1.15
-3.0
2.0
2.39
3.40
1.50
2.30
r2
0.1939
0.128
0.4706
0.606
0.77
0.4527
0.137
0.6661
0.635
0.81
0.5391
0.780
0.64
0.61
0.8879
0.818
0.91
0.88
0.5017
0.204
0.6102
0.244
0.61
0.50
0.7736
0.633
0.53
0.68
0.7274
0.76
0.62
0.69
(continued)
Statistical Summary, EMAP-E Virginian Province - 1991
Page D - 9
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Table D-1 (continued).
Element References
Sb
Se
Sn
Zn
EMAP Va. Prov. - 1991
EMAP Va. Prov. - 1991
Hanson et al., 1993
EMAP Va. Prov. -1991
Hanson et al., 1993
EMAP Va. Prov. - 1991
Hanson et al., 1993
Windom et al., 1989*
Windom et al., 1989 *
m
0.1008
0.0922
0.048
0.5064
0.367
21.9
11.7
12
12
Regression parameters
b
-0.0011
-0.0012
0.002
-0.0212
0.292
-9.60
0.9
-8
1
r2
0.3213
0.4538
0.282
0.7677
0.437
0.7294
0.720
0.70
0.83
(*) s Data for Georgia and South Carolina coastal sediments
(T) « Data for Florida coastal sediments
Page D - 10
Statistical Summary, EMAP-E Virginian Province - 1991
U.S. GOVERNMENT PRINTING OFFICE: 1994 - 550-001/80368
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