United States
Environmental Protection
Agency
Office of Water
(WH-556F)
EPA 842-S-92-005
June 1992
Final Revision to Initial
Report on Results of
Studies Conducted in
the Vicinity of 106-Mile
Deepwater Municipal
Sludge Site
U
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FINAL
REVISION TO INITIAL REPORT
RESULTS OF STUDIES CONDUCTED
IN THE VICINITY OF 106-MILE DEEPWATER
MUNICIPAL SLUDGE SITE
May 3, 1988
U.S. ENVIRONMENTAL PROTECTION AGENCY
Region II
New York, New York
and
Office of Marine and Estuarine Protection
Washington, DC
Prepared Under Contract No. 68-03-3319
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TABLE OF CONTENTS
Page
1, INTRODUCTION 1
2. SUMMARY OF STUDIES 6
3. HYPOTHESES WITHIN TIERS OF MONITORING PROGRAM . . 14
3.1 TIER 2: NEARFIELD FATE AND SHORT-TERM EFFECTS ........ 14
3.2 TIER 3: FARFIELD FATE IS
3.3 TIER 4: LONG-TERM EFFECTS . . 17
4. STUDY RESULTS APPLICABLE TO MONITORING PROGRAM ..... 19
4.1 PHYSICAL OCEANOGRAPHY ..... 19
4.1.1 Pycnocline Depth 21
4.1.2 Currents 24
4.2 MARINE CHEMISTRY 36
4.2.1 Metals 37
4.2.2 Organic* ' 39
4.2.3 Dissolved Oxygen and pH ...... 41
4.3 MARINE BIOLOGY 42
4.3.1 Plankton Communities . 43
4.3.2 Commercial, Prey, and Endangered Species 44
4.3.3 Btnthic Communities 45
4.3.4 Pathogens 47
5. LITERATURE CITED 48
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LIST OF FIGURES
£§!§
Figure 1. Implenientation of the 106-Mile Site Monitoring Program
Involves a Tiered Approach to Address Assessuent of
Permit Compliance and Potential Impacts . . 2
Figure 2. Areal Coverage of Studies Conducted in the Vicinity
of the 106-Mile Site (Shaded Area) ...
Figure 3. Schematic Representation of Season*! Variations in
Pyenoeline Depth at the 106-Mile Site. Three Ctses
Are Illustrated: the Permanent Pycnoclinej the Seasonal
Pycnocline; and a Pycnocline Caused by a Surface Layer
of Shelf Mater . . ................... 25
Figure 4. Conceptual Model of the Circulation in the Slope Water
Region, as Presented by Csanady and Hamilton (1988) ... 28
Figure 5. Trajectories of Subsurface Drifters Launched in the Gulf
Stream Offshore North Carolina (near 35% 7S°W)t from
Bower, O'Gara and Rossby (1985) ...... . . ..... 35
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LIST OF TABLES
Table 1. Impact Categories In Ocean Dumping Regulations and
Predictions for Potential Impacts of Sludge Dumping
at the 106-Mile Site . . .
Table 2. Background Summary of Studies Conducted Within the
Vicinity of the 106-Mile Site
Table 3. Summary of the Technical Objectives of Studies Conducted
in the Vicinity of the 106-Mile Site ....
Table 4. Data Issues Contained in the Null Hypotheses Associated
with the Assessment of Potential Impacts
Page
4
7
9
20
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1. INTRODUCTION
The United States Environmental Protection Agency (EPA), under the
Marine Protection, Research, and Sanctuaries Act of 1972 (MPRSA, PL 92-532),
is responsible for regulating disposal of wastes, including sewage sludges,
in ocean waters. Under MPRSA, EPA has published ocean dumping regulations
(40 CFR Parts 92-532), which require EPA to develop and maintain monitoring
programs for designated ocean disposal sites.
EPA has developed a monitoring plan ( EPA , 1992a) for the 106-Mile
Deepwater Municipal Sludge Site (106-Mile Site), located beyond the
continental shelf off the New York/New Jersey coast. The objective of the
monitoring program is to ensure that regulatory requirements are met. Data
generated through the monitoring program will be used by EPA to make
decisions about site redesignation or dedesignationj continuation,
termination, or modification of permits; and continuation, termination, or
modification of the monitoring program itself. The plan for implementing
the monitoring program ( EPA > 1992a) is summarized in Figure 1.
The monitoring strategy focuses on two areas of concern: assessment of
compliance with permit conditions and assessment of potential impacts of
sludge disposal on resources or other aspects of the marine environment. The
approach used to address assessment of permit compliance and potential
impacts uses a series of monitoring tiers. Each tier represents a series of
null hypotheses, or questions, to be tested through monitoring activities.
The tiered approach organizes the null hypotheses into a hierarchy, whereby
data collected in each tier form the basis for the design and extent of
monitoring activities in the next tier. Such an approach ensures that only
information needed for making decisions will be obtained (leller and Wastler,
1987).
The purpose of this report, which is an updated revision of a previous
report ( EPA , 1986), is to review studies conducted in the vicinity of
the 106-Mile Site. Those study results that pertain to or can be used to
test the null hypotheses directed at the assessment of potential impacts
(Tiers 2, 3, 4) will be summarized. Some of the information provided by the
studies reviewed for this report can be used to establish baseline
conditions within the vicinity of the site. Although not used in the
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Implementation of
Monitoring Program
Assessment of
Permit Compliance
Assessment of
Potential Impacts
TIER 1
Waste Characteristics and
Disposal Operations
TIER 2
Nearfield Fate and
Short-Term Effects
TIER 3
Parfield Fate
TIER 4
Long-Term Effects
FIGURE 1. IMPLEMENTATION OF THE 106-MILE SITE MONITORING PROGRAM INVOLVES A TIERED APPROACH
TO ADDRESS ASSESSMENT OP PERMIT COMPLIANCE AND POTENTIAL IMPACTS.
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assessment of permit compliance, baseline conditions provide a frame of
reference against which to compare the results of monitoring activities
directed at the assessment of potential impacts (Tiers 2, 3» and 4).
The objectives of the monitoring tiers that address assessment of
potential impacts are founded in the ocean dumping regulations, which specify
the impact categories listed in Table 1. The monitoring plan ( EPA ,
1992a) describes the regulatory basis for the monitoring program and how the
site and sludge characteristics have been used to predict potential impacts
(Table 1) for each impact category resulting from sludge disposal. The
predicted potential impacts have, in turn, been used to formulate the null
hypotheses that have been organized into tiers (Figure 1) for testing through
monitoring activities.
Because the emphasis in this report is on study results that provide
information that can be used in the assessment of potential impacts, this
report has been organized into sections corresponding to the monitoring
tiers associated with assessment of potential impacts. Brief summaries of
the studies reviewed for this report are presented in Section 2.
Section 3 lists the null hypotheses associated with Tier 2 (Nearfield
Fate and Short-Term Effects), Tier 3 (Farfield Fate), and Tier 4 (Long-Term
Effects) of the monitoring program. In addition to the null hypotheses,
Section 3 includes the scientific issues relevant to each hypothesis, or the
type of information needed to test each null hypothesis.
Summaries of study results are included in Section 4. Only those
results that relate directly to the scientific issues of the null hypotheses
are discussed. Because the null hypotheses contain issues that fall into
three general scientific areas, Section 4 is organized into subsections for
physical oceanography, marine chemistry, and marine biology.
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TABLE 1. IMPACT CATEGORIES IDENTIFIED IN OCEAN OWING REGULATIONS AND PREDICTIONS FOR
POTENTIAL IMPACTS OF SLUDGE DURING AT TOE 106-MILE SITE.
Impact Categories
Predicted Potential Iifjacts
Impingement of sludge onto
shorelines
Movement of sludge into marine
sanctuaries or shell fishery or
fishery areas
Effects of sludge on commercial
fisheries
Accumulation of sludge constituents
in biota
Progressive changes in water quality
P-l: Sewage sludges dumped at the 106-Mile Site
will probably not impact any shoreline in
detectable quantities.
P-2; Marine sanctuaries and shellfishery areas will
probably not be impacted by shoreward movements of
sludge.
P-3: Sewage sludge may be transported to the
continental slope and shelf where fishery
activities exist.
JMj Tht impact of sludge dumping on commercial
fisheries, expressed as direct decrease in fish
stocks or decrease in eggs or larvae, will probably
not be detected, and the use of any area for
fishing will not be reduced.
P-5: Bioaccumulation of low levels of contaminants
associated with sewage sludge from the 106-Mile
Site will occur, from time to time, at the site or
directly adjacent to the site, by migrating fishes
or invertebrates, but may be difficult to
distinguish from other potential sources.
P-6: Bioaccumulation of low levels of contaminants
by resident continental shelf/slope fishes or
invertebrates may occur, depending on direction and
extent of transport of sludge to these areas, but
may be difficult to distinguish from
bioaccumulation from other potential sources.
P-7t Sewage sludge movement and transport beyond
the site boundaries may result in significant
impact on the water quality beyond the site.
P-8: Sludge constituents may be found in
significant quantities within the site at all times
and may persist beyond 4 hours after disposal.
Chronic effects on marine biota are possible.
P-9; Though certain sludge constituents may be
detectable well outside the site, their levels are
not expected to have significant effects on marine
biota.
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TABLE 1. (continued)
Impact Categories
Predicted Potential Impacts
Progressive changes in sediment
composition
Impacts on pollution-sensitive
species
Impacts on endangered species
Progressive changes in biological
communities
P-10: Sludge particles may settle outside the
disposal site boundaries. However, this settling
will occur over a very large and as yet undefined
area. The resultant changes in sediment
composition, the destruction of habitat, and/or the
accumulation of sludge constituents in surficial
sediments will probably be nil to minimal.
P-ll: The disposal of sewage sludge probably will
not cause long-term impacts on pollution-sensitive
species or life-cycle stages in the water column or
the sediments of the 106-Mile Site region. Effects
may be detectable, but local and short-lived.
P-12: The sea-surface microliyer in the disposal
site and in an undefined area adjacent to the site,
as well as the sensitive life stages of marine
biota within may be affected by the surface-active
consonants and nonpolar pollutant compounds present
in sludges.
P-13: Endangered species of mammals or reptiles
will probably not be impacted by sewage sludge
disposal at the 106-Mile Site.
P-14: Due to nutrient enrichment in the upper water
column, there may be a localized increase in
primary productivity related to individual sewage
plumes.
P-15: There will probably be no long-term or large-
scale impact on the plankton community as a result
of sludge disposal at the 106-Mile Site.
P-16; Because ol the expected absence of sewage
sludge particles in the demersal or benthic
environment, no effects on the benthic or demersal
community structures are likely.
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2. SUMMARY OF STUDIES
Much information on physical characteristics and baseline chemical and
biological conditions at the 106-Mile Site is available from studies
conducted during the past decade. This information was used to develop the
framework of the 106-Mile Site monitoring plan. It also represents a
valuable resource that can be used to test the various hypotheses of the
monitoring plan. The purpose of the initial version of this report, the
Studies Document, ( EPA , 1986) was to summarize the pertinent results of
these major studies, but because the final project results were not available
at that time, the Studies Document presented only an overview of individual
project objectives and a summary of the field measurements. This report
presents an update of the scientific results from the major studies that were
identified in the initial Studies Document. Some additional studies have
also been reviewed for this report because they provide information that is
relevant to the issues at the 106-Mile Site.
In this section, the sampling design and scientific objectives of each
of the reviewed studies are briefly summarized, with supporting information
provided in Table 2. Each study has been numbered to facilitate simple
reference in the text; locations of measurements for each study are shown in
Figure 2. Table 3 summarizes important types of data obtained from each
study. The data topics included in Table 3 have been specifically selected
because they correspond to scientific issues raised by the null hypotheses,
which are discussed in Section 3.
Study 1: Mid-Atlantic Slope and Rise Physical Oceanography Study
(MASAR). This study, funded by the U.S. Department of the Interior (DOI),
Minerals Management Service (MMS), was conducted by Science Applications
International Corporation (SAIC) between September 1983 and September 1986.
The study area (see Figure 2) was bounded by the shelf break to the west, the
outer continental rise area to the east, 36°N to the south, and 40°N to the
north. Current measurements, hydrographic measurements, and remote sensing
data were used to evaluate potential impacts of petroleum exploration on the
continental shelf, slope, and rise. The program was designed with the
following objectives:
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TABLE 2. BACKGROUND SUMMARY OF STUDIES CONDUCTED WITHIN THE VICINITY OF THE
106-HILE SITE.
Study
Sponsor
Prine
Contractor
Date of
Measurement
1. Mid-Atlantic Slopi and DOI, MMS
Rise Physical Oceanography
Study (MASAR)
2. Shelf Edge Exchange DOE
Processts Program (SEEP)
SAIC
BNL, L-DGO,
UHOI, Yale
9/83 - 9/86
1982 - 1992
3A. Study of Biological DOI, MMS
Processes on the U.S. Mid-
Atlantic Slope and Rise
3B. Analysis of Trace DOI, MMS
Metals in Bottom Sediments
on the U.S. Mid-Atlantic
Slope and Rise
4A. Study of Biological DOI, MMS
Processes on the U.S.
North Atlantic Slope and
Rise
4B. Analysis of Trace DOI, MMS
Metals in Bottm Sediments
on the U.S. North Atlantic
Slope and Rise
5. four Studies of EPA
Baseline* Conditions at
the 106-Mile Site
6. Study of Baseline EPA
Conditions at the North
Atlantic Incineration Site
7. Current Meter EPA
Measurements at the 106-
Mile Site in Support of
Municipal Waste Disposal
8. Analysis of Circulation NOAA
Characteristics in the
Vicinity of Deepwater
Dumpsite 106
Battelle
USGS
Battelle
uses
5A. JRB
SB. Battelle
5C. Battelle
50, BattelU
Battelle
3/84 - 7/86
3/84 - 7/86
11/84 - 4/87
11/84 - 4/87
5A. 7-8/84
5B. 8/85
5C. 2/86
5D. 8-9/86
11/85
Battelle, SAIC 9/86 - 4/87
EG&G
1968 - 1981
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FIGURE 2. AREAL COVERAGE OF STUDIES CONDUCTED IN THE VICINITY OF THE
,« SITE (SHADED AREA). STUDIES ARE IDENTIFIED BY NUMBER IN
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TABLE 3. SUMMARY OF THE TECHNICAL OBJECTIVES OF STUDIES CONDUCTED IN THE
VICINITY OF THE 106-MILE SITE.
Studies
Objectives 1 2 3A 38 4A 4B 5A 58 5C 50 6 7 8
Physical Oceanography
Pycnocline Depth x x
Currents x x
Participates x x x x
Marine Chemistry
Metals x x x x x x x
Organics x x x x x x x
Dissolved Oxygen x x x x x x
pH Levels x x x
Bioaccumulation x x X
Marine Biology
Plankton Communities x x x x
Endangered Species x x x x x x
Benthic Communities x x
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Determine general seasonal ocean circulation features,
Quantify and describe ocean circulation processes that produce
variability.
Determine the degree to which continental slope and rise
circulation features influence the physical oceanography of the
adjacent Mid-Atlantic continental shelf.
Results of MASAR have been presented in a final program report (Science
Applications International Corporation, 1987). Further analysis of the
MASAR results with a model of the circulation in the slope water region has
been presented by Csanady and Hamilton (1988).
Study 2: Shelf Edge Exchange Processes Program (SEEP). This program,
funded by the U.S. Department of Energy, is an ongoing, multidisciplinary
study conducted by Brookhaven National Laboratory (BNL), Lamont-Doherty
Geological Observatory (L-DGQ), Woods Hole Oceanographic Institution (WHQI),
and Yale University. The program is designed as a multiphase study along the
U.S. east coast from south of Nantucket Shoals to Cape Hatteras. The first
phase (SEEP-I) consisted of a 1-year (1983-1984) physical, chemical, and
biological measurement program across the outer continental shelf and upper
slope south of New England (see Figure 2). Although each component of this
multidisciplinary program has specific scientific objectives, the primary
theme of the study is to define the processes that govern the distribution
and fate of "energy-related pollutants" that might be introduced into the
marine environment of the coastal United States. (Department of Energy,
1982). Measurements were specifically directed at resolving the fate of
fine-grained particles from the continental shelf.
Scientific results of SEEP-I will be presented in a series of articles
to appear in a special issue of Continental Shelf Research during the next
few months. To facilitate review of the SEEP-I results prior to publication,
the editor of Continental Shelf Research kindly made draft copies of selected
articles available to Battelle.
SEEP-II, a companion monitoring program to SEEP-I, is being conducted in
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the middle-Atlantic region (37° to 38°N), but these results will not be
available for at least 2 years.
Study 3At Study of Biological Processes on the U.S. Mid-Atlantic Slope
and Rise; Study 3B? Analysis of Trace Metals in Bottom Sediments in Support
of Deepwater Biological Processes Studies on the U.S. Mid-Atlantic Slope and
Rise. Study 3A was conducted by Battelle, in conjunction with WHOI and
L-DGQ, for the U.S. DOI, MMS. The analysis of trace metals in sediments
(Study 3B), performed by the U.S. Geological Survey (USGS), was supported
under a separate interagency agreement. The studies were developed as a
multidisciplinary monitoring program that focused on two deepwater
exploratory drilling sites. Six sampling surveys were conducted between
March 1984 and July 1986. The primary objectives of the monitoring program
were the following:
Characterize predrilling biological, geological, and chemical
properties of benthic environments at 14 stations in the general
vicinity of two exploratory drilling sites.
* Monitor potential changes in these properties with time, and to
determine whether the changes are caused by drilling-related
activities, or whether they are the result of other phenomena
including natural temporal or spatial variation.
Determine the distribution and fate of discharged drilling-
related materials that have accumulated above background levels.
Estimate recovery rates of deep-sea benthic communities
potentially impacted by drilling-related activities,
Results of the monitoring program have been reported by Maciolek et al.
(1987a) and Bothner et al. (1987a).
Study 4A: Study of Biological Processes on the U.S. North Atlantic
Slope and Rise; Study 4Bt Analysis of Trace Metals in Bottom Sediments in
Support of Deepwater Biological Processes Studies on the U.S. Worth Atlantic
Continental Slope and Rise. Studies 4A and 4B were developed as a companion
program to the U.S. Mid-Atlantic Slope and Rise program (Studies 3A and 3B),
The program was conducted by Battelle, in conjunction with WHOI and L-DGO.
Analyses of metals in sediments by the USGS was supported under a separate
interagency agreement. The multidisciplinary program, which included six
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seasonal surveys between November 1984 and April 1987, had the following
objectives:
Characterize predrilling biological, geological, and chemical
properties of benthic environments at a limited number of stations
within areas of potential oil and gas development on the North
Atlantic Slope and Rise.
Monitor potential changes in those properties with time to
determine the extent of natural temporal and spatial variation.
Determine the background distribution of materials (such as trace
metals and hydrocarbons) that may accumulate at elevated levels due
to future drilling operations.
Results of these studies have been presented by Maciolek et al. (1987b)
and Bothner et al. (1987b).
Study 5: Studies of Baseline Conditions at the 106-Mile Site. Study 5
actually refers to a series of four baseline surveys of the 106-Mile Site
funded by EPA. The July/August 1984 survey (Study 5A) was conducted for EPA
by JRB Associates; the August 1985 (Study 5B), February 1986 (Study 5C), and
August/September 1986 (Study 5D) surveys were conducted for EPA by Battelle.
Although the four surveys were conducted as separate studies, they all shared
a common objective: to obtain information concerning baseline conditions at
the 106-Mile Site. Results for each individual study have been presented in
several reports ( EPA , 1986; EPA , 1987a; EPA , 1988a).
Study 6: Study of Baseline Conditions at the North Atlantic
Incineration Site. This EPA-funded study was conducted by Battelle in
November 1985 as part of the ocean incineration program. The primary
objectives of the study were to field-test sampling equipment and analytical
methods for use during the monitoring of a research burn and to collect
baseline data for water, air, and biota at the site. Results of the
analysis of samples collected during the study have been reported by EPA
(1987b).
Study 7: Current Meter Measurements at the 106-Mile Site in Support of
Municipal Haste Disposal. This EPA-funded study was conducted by SAIC under
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sybcontract to Battelle. From September 1986 to April 1987, two current
meter moorings were deployed on the 2500-m isobath northeast and southwest of
the 106-Mile Site (Figure 2) . The moorings were designed to monitor the
current and temperature structure of the upper layers of the ocean in the
vicinity of the 106-Mile Site. The primary objective of the study was to
assess the effects of various current regimes on sludge disposal. Results of
the study have been reported by EPA (1992
Study 8t Analysis of Circulation Characteristics in the Vicinity of
Deepwater Dumpsite 106. This study was performed by EG&G for the National
Oceanic and Atmospheric Administration (NOAA), The scope of the study
consisted of a review and analysis of more than 300 months of current meter
data collected between 1968 and 1981. The primary objective was to describe
the long-term mean circulation patterns in the continental slope region along
the U.S. east coast. Investigators have reported on the general pattern of
slope circulation based on monthly averaged data (National Oceanic and
Atmospheric Administration, 1985).
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3. HYPOTHESES WITHIN TIERS OF MONITORING PROGRAM
This section presents the null hypotheses associated with the monitoring
prograi tiers introduced in Section 1. Because this report focuses on
studies that may provide baseline information to be used in the assessment of
potential impacts of sludge disposal, this section addresses only those null
hypotheses within the following monitoring tiers:
Tier 2: Nearfield Fate and Short-Term Effects
Tier 3: Farfield Fate
* Tier 4j Long-Term Effects
The null hypotheses within Tier 1 (Waste Characteristics and Disposal
Operations), which are related to assessment of permit compliance, are not
addressable by any of the studies under consideration. Thus, the Tier 1 null
hypotheses are not discussed in this report.
In addition to presenting null hypotheses, this section lists types of
measurements or information that must be obtained in order to test each
hypothesis. For example, Ho6, which is stated in Section 3.1, concerns the
settling of sludge particles in relation to the pycnocline. In order to test
H06, information is needed about the depth of the pycnocline, the settling
rates of sludge particles, the background levels of particles in the
vicinity of the 106-Mile Site, and regional current characteristics. Thus,
the types of measurements relevant to H
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those occurring within 24 hours. Knowing the behavior and movement of sludge
immediately following disposal is necessary to test assumptions, regarding
dispersion and dilution, that are used in permit-issuance decisions. Knowing
the short-term effects of sludge disposal is necessary to test the assumption
that permit compliance is sufficiently protective of the marine environment.
The Tier 2 null hypotheses are as follows:
NEARFIELD FATE
H06: Sludge particles do not settle in significant quantities to the
seasonal pycnocline (50 w) in the summer or to the SO-* depth at
any tine, within the site boundaries or in the area adjacent to the
site.
Relevant information:
Pycnocline depth
Sludge settling rates
Background particulate levels
Currents
H07: The concentration of sludge constituents within the site does not
exceed the limiting permissible concentration (LPC) or water
quality criteria (HQC) 4 hours after disposal and is not
detectable in the site 1 day after disposal.
Relevant information:
Metals concentrations within the site
Concentrations of organic compounds within the site
Ho8: The concentration of sludge constituents at the site boundary or in
the area adjacent to the site does not exceed the LPC or WQC at
any time and is not detectable 1 day after disposal.
Relevant information:
Metals concentrations outside the site
Concentrations of organic compounds outside the site
Ho9: The disposal of sludge does not cause a significant depletion in
the dissolved oxygen content of the water column nor a significant
change in the pH of the seawater in the area.
Relevant information:
Oxygen concentrations in the area
pH levels in the area
SHORT-TERM EFFECTS
HQ10: No significant biological effects in the water column are
measurable within the site within 1 day after disposal.
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Relevant information:
Biological conditions within the site
H011: Ho increase in primary productivity or any changes in planktonlc
biomass or species composition will occur.
Relevant information;
Primary productivity
Planktonic bionass
H012: No evidence of short-tern bioaccunulation of sludge constituents by
commercially important species found at or adjacent to the site or
in important prey species found it or adjacent to the site will be
found within 1 day after disposal.
Relevant information:
Commercially important species
Important prey species
Bioaccumulation of metals
Bioaccumulation of organic compounds
H013: Sludge constituents do not accumulate in the surface nicrolayer in
the vicinity of the site.
Relevant information:
Surface microlayer concentrations of sludge
constituents
3.2 TIER 3; FARFIELD FATE
Before any estimation of long-term effects resulting from sludge
disposal at the 106-Mile Site can be made, it is necessary to determine where
the sludge goes, the area of the seafloor that may be influenced by sludge
particles, and the cumulative concentrations that may be expected in the
water column and sediments after many years of disposal. The null hypotheses
within Tier 3 relate to where the sludge goes over the long term.
Null hypotheses concerning farfield fate address impact issues that
pertain to potential movement toward and subsequent impact to shorelines
(predicted potential impact P-l, refer to Table 1), to marine sanctuaries and
fisheries (P-2), and to the continental shelf/slope (P-3). The Tier 3 null
hypotheses also address information necessary in deciding whether studies
should be conducted under Tier 4 to determine whether there is a potential
for long-term impacts from sludge disposal, and if so, where those studies
should be conducted. The Tier 3 null hypotheses are as follows:
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H014: Sludge constituents do not settle beneath the pycnocltne outside
the disposal site.
Relevant information;
Pycnocline depth outside the site
Sludge settling rates
Currents
Metals concentrations outside the site
Concentrations of organic compounds outside the site
H015: Ocean currents do not transport sludge to any adjacent shoreline,
beach, Marine sanctuary, fishery, or shell fishery.
Relevant information,*
Onshore currents via the slope circulation,
warm-core eddies, or other processes.
HolSj Sludge recirculation through the site is not significant.
Relevant information:
The hypothesized slope sea gyre or
recirculation via warm-core eddies that
revisit the site
Hol7: Sludge particles do not settle to the sea floor in the vicinity of
the site or in the region predicted as a possible settling region
based on laboratory settling measurements and current trajectory
analysis.
Relevant information:
Sludge settling rates
Currents
Metals concentrations in sediments
Concentrations of organic compounds in sediments
3.3 TIER 4t LONG-TERM EFFECTS
The objective of Tier 4 is to assess whether there are long-term impacts
of sludge disposal at the 106-Mile Site. Long-term effects may occur within
or outside the site. An example of long-teri effects within the site would
be a progressive decline in water quality, although such an effect is not
predicted. Long-term effects outside the site, such as bioaccumulation of
sludge constituents, would only be expected if sludge is regularly
transported 1n a given direction (determined through studies of farfield
fate).
Because the null hypotheses within Tier 4 are related to long-term
effects, the studies results summarized in Section 4 are not sufficient to
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test the Tier 4 hypotheses. However, baseline data provided by some of the
studies may be used as a reference against which to compare data obtained
through monitoring activities. The Tier 4 null hypotheses are as follows;
H018: Sludge constituents have no significant long-ten effect on the
distribution of endangered species in the vicinity of the site.
Relevant information:
Endangered species distributions
H019: Sludge constituents do not accumulate in the tissues of
commercially important species resident in shelf/slope areas
adjacent to the site.
Relevant information;
Commercially important species
Bioaccymulation of sludge constituents
Ho20: Benthic community structure does not change significantly due to
sludge disposal.
Relevant information;
Benthic community structure
Ho21: Sludge disposal has no effect on the sensitive eggs and larval
stages of indigenous animals.
Relevant information:
Indigenous animals (i.e., important commercial,
important prey, endangered, and benthic species)
Effects of sludge constituents on eggs and larvae of
indigenous animals
H022: Sludge disposal has no measurable long-term impact on offshore
plankton communities.
Relevant information:
Plankton communities
Ho23: Pathogen levels will not increase in the water column or in the
biota.
Relevant information:
Pathogen levels
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4. STUDY RESULTS APPLICABLE TO MOHITORINS PROGRAM
This section focuses on those study results that are applicable to the
null hypotheses that form the framework of the monitoring program. Table 4
lists the data issues associated with each hypothesis (refer to Section 3).
The information needed to address the null hypotheses used in the assessment
of potential impacts can be divided into the following general categories:
* Physical oceanography
* Marine chemistry
* Marine biology
This section is organized according to the three general categories of
relevant information, rather than by hypothesis, because many of the data
issues are contained in several hypotheses (see Table 4). In this manner,
results that may be applicable to several hypotheses may be related to the
information common to those hypotheses, rather than repeated for each of the
hypotheses.
4.1 PHYSICAL OCEANOGRAPHY
The null hypotheses directed at the assessment of nearfield (Tier 2) and
farfield.(Tier 3) fate require, as input, information on the physical
oceanographic processes and conditions at the 106-Mile Site and surrounding
regions. Although there exist a myriad of processes that ultimately affect
the dynamics of this region, only those that will have a significant effect
upon the vertical and horizontal transport of sludge dumped at the site will
be addressed in the present review of studies results. Table 4 illustrates
that there are two scientific issues/processes within the category of
physical oceanography that are expected to have a major effect on the
behavior of sludge dumped at the 106-Mile
Pycnocline depth
* Currents
19
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TABLE 4. DATA ISSUES CONTAINED IN THE NULL HYPOTHESES ASSOCIATED WITH THE
ASSESSMENT OF POTENTIAL IMPACTS.
Hypotheses
Issues 6 7 8 9 10 11 12 13 14 15 16 17 18 19 21 22 23
Physical Oceanography
Pycnocline Depth x x x
Currents x x x x x
Marine Chemistry
Metals xx x x x x
Organic Compounds x x x x x x
Dissolved Oxygen x
pH Levels x
Hanne Biology
Plankton Communities x
Primary Productivity x x
Planktonic Biomass x x
Commercial Species x x x x
Important Prey Species x x x
Endangered Species x x x
Benthic Communities x x x
Pathogens x
20
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Pycnocline depth 1s known to play a major role in the settling
(vertical transport) of sludge, whereas, currents govern the dispersion and
advection (horizontal transport) of sludge, both in the nearfield and the
farfield. In the following subsections, a summary of recent (and site-
specific) results is presented for each oceanographic process: pycnocline
depth (subsection 4.1.1) and currents (subsection 4.1.2). Results are
presented by individual study; synthesis of all study results for a specific
process was beyond the scope of this review project. The individual results
illustrate that much is known about the physical processes that will
ultimately affect the transport of sludge dumped at the 106-Mile Site. It is
also important to note that these processes will not be affected by the
sludge, in contrast to local chemical and biological characteristics which
may be significantly altered by sludge disposal. The knowledge of physical
processes that has been gained from the past studies is, thus, directly
applicable to the conditions that will be encountered during sludge disposal,
whereas chemical and biological measurements from past surveys represent
only baseline data from which to make short-term (Tier 2 and 3) and long-term
(Tier 4) assessments of the effects of sludge disposal at the site.
4,1.1 focnocline Depth
The term pycnocline refers to a layer in the water column where vertical
gradients of density are strong relative to the remainder of the water
column. With regard to ocean dumping of seawage sludge, the pycnocline is an
important factor affecting sludge behavior because 1t represents a potential
barrier to vertical mixing and settling of sludge particles. In extreme
cases where the pycnolcine is very intense, particles may be prohibited from
settling through the pycnocline and accumulation will be significant at this
depth. In practice, however, particle settling is difficult to predict as it
is highly dependent upon particle characteristics (e.g., size, density)
pycnocline intensity, and seawater viscosity.
The depth of the pycnocline off the U.S. east coast varies according to
three principal factors*. (1) location, (2) season, and (3) resident water
mass and/or oceanographic feature. At any given site, there is a smoothly
varying seasonal cycle to pycnocline depth; this cycle is a difect result of
21
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solar radiation. In simmer, a near-surface seasonal pycnoeline separates the
warm surface waters from the underlying, relatively cool, dense water that
comprised the upper water column during the prior winter and spring* As the
overlying atmosphere cools in autumn, and increased winds and waves cause
intense vertical mixing in the near-surface layers, the seasonal pycnoeline
is eroded from the surface and a relatively cool, surface mixed layer is
formed. The depth of this winter mixed layer varies greatly from year to
year, in relation to the number and intensity of the storms passing over the
region. This winter mixed layer often extends to depths of 100 m or greater,
such that the base of the mixed layer coincides with the top of the permanent
pycnocline. Thus, the depth of the pycnoeline in summer refers to the depth
of the seasonal pycnocline, whereas in winter when the seasonal (summer)
pycnocline is absent, pycnocline depth refers to the depth of the permanent
pycnocline.
MASAR and SEEP (Studies 1 and 2)
To determine the seasonal variability of pycnocline depth in a
particular region such as the 106-Mile Site, it is necessary to analyze a
large number of vertical density (temperature and salinity) profiles from
each season, and preferably, from a number of years to address interannual
variability. A large number of hydrographic profiles were made across the
continental shelf and slope during the MASAR and SEEP programs (see Figure
2), but because pycnocline depth was not one of the principal analysis
topics, the density profile results are not presented in a form that allows
simple interpretation of seasonal variability in pycnocline depth.
The MASAR hydrographic program consisted of eight cruises, with one
cruise per season in both 1984 and 1985. These data would yield a fair
representation of the seasonal cycle within 2 consecutive years, but two
observations from each season do not represent a good statistical sample of
pycnocline depth for all years. Similarly, the relatively small number of
hydrographic surveys made during SEEP would not yield a good statistical
representation of seasonal and interannual variations in pycnocline depth
because of the limited sampling program.
22
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Analyses of Historic Data
An accurate, statistical determination of pycnocline depth and its
seasonal variability at the 106-Mile Site can only be derived from a
numerical analysis of many years of hydrographic profile results, such as
the data archives maintained by the National Oceanographie Data Center
(NODC). For example, a less extensive yet informative analysis of historical
hydrographic data from the 106-Mile Site has been presented by Warsh (1975)
in NOAA Dumpsite Evaluation Report 75-1. Warsh has presented monthly
averaged temperature and salinity profiles from which seasonal variations in
pycnocline depth can tasily be interpreted. Figure 3 presents the seasonal
cycle of pycnocline depth as derived from the results presented by Warsh
(1975). In this figure, the permanent pycnocline exhibits considerable depth
variability ranging from a maximum of 200 m in April to a minimum of 100 m
throughout the remainder of the year. The upper boundary of the seasonal
(summer) pycnocline is, in contrast, very shallow (10 to 30 ro) and present
only from May through October* This figure illustrates that although the
permanent pycnocline exists throughout the year, the seasonal pycnocline will
be the limiting factor in the initial mixing and vertical penetration of
sludge dumped at the 106-Mile Site during summer. A more comprehensive
numerical analysis of historic NODC hydrographic data will be required to
refine these statistical estimates of pycnocline depth and its seasons!
variability. Spatial variations in pycnocHne depth can also be investigated
in conjunction with the temporal analyses of pycnocline depth.
Hearfteld Monitoring Studies
In addition to seasonal variations, pycnocline depths can also be
affected by the passage of anomalous water masses and/or oceanographic
features. At the 106-Mile Site, warm-core eddies of Gulf Stream origin and
displaced parcels of shelf water can have major impacts on the vertical
profile of density in the upper water column. For example, under Sustained
northerly wind conditions, shelf water has been observed as far offshore as
the 106-Mile Site, and when this occurs, large vertical density gradients can
arise at the interface between the shelf and slope water masses. Such an
23
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event was observed during the Winter 1988 nearfield monitoring survey of the
106-Mile Site ( EPA , 1988b)': a 40-m thick layer of relatively fresh shelf
water lay above the resident slope water creating a temporary pycnocline that
was much shallower than the permanent pycnocline. This "shelfwater"
pycnocline would greatly reduce the vertical penetration of sludge dumped at
the 106-Mile Site during winter conditions. This hypothetical (yet
previously observed) case is superimposed on the seasonal cycle of pycnocline
depth presented in Figure 3.
Similar temporary (3- to 15-day), nonseasonal variations in pycnocline
depth can also be caused by the passage of warm-core eddies. The waters
within these eddies are less dense than typical slope waters, and
consequently, vertical density profiles on the edge of these eddies may
exhibit near-surface pycnoclines that are much shallower than ambient
pycnoclines. This occurrence is especially true during winter when the
surface temperatures within the eddies are much greater than surface
temperatures of the ambient slope water. In summer, surface temperatures
within the eddies are similar to those of the surrounding waters, and
pycnocline depths may not be affected as much as during winter.
Nevertheless, warm-core eddies must be viewed as an important physical
mechanism for large, short-term changes in pycnocline depth at the 106-Mile
Site. Additional data analyses will be required to quantify their potential
effects during all seasons,
4.1.2 Currents
Information on currents at the 106-Mile Site is required for two primary
purposes: (1) to determine the rates at which sludge is transported out of
the site after discharge (nearfield fate studies), and (2) to predict the
pathways and rates of farfield transport. The likelihood of sludge
recirculation through the site is also a major topic of interest.
Results from a variety of recent current measurement programs and
numerical modeling studies have greatly increased the knowledge of currents
and circulation along the U.S. east coast and in the vicinity of the 106-Mile
Site. These results are summarized below according to individual research
programs! however, it is informative to first provide a brief introduction to
24
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M
MONTH
J J A
100-S
Wl
I
h-
0_
LU
Q
Seasonal
Pycnocline
Permanent
Pycnociine
150
200
250
FIGURE 3. SCHEMATIC REPRESENTATION OF SEASONAL VARIATIONS IN PYCNOCLINE
DEPTH AT THE 106-MILE SITE. THREE CASES ARE ILLUSTRATED: THE
PERMANENT PYCNOCLINEf THE SEASONAL PYCNOCLINE: AND A PYCNOCLINE
CAUSED BY A SURFACE LAYER OF SHELF HATER.
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the four major oceanographic processes that govern the currents of the
regiont the slopewater circulation, warm-core Gulf Stream eddies, mesoscale
and subiesoscale eddies that frequent the shelf/slope front, and events
where shelf water reaches as far offshore as the 106-Mile Site. Specific
issues concerning sludge transport for each of these current regimes include
the following:
Slopewater Circulation
Do the weak, southwestward currents within the slope water
represent the "normal" current pattern such that farfield transport
of sludge will almost always be directed toward the southwest?
During the slopewater current regime, is sludge transported onto
the continental shelf or toward major fisheries or sanctuaries?
* Can sludge be recirculated through the site by the hypothesized
slopewater gyre?
* Will sludge contained within the slope water ultimately be injected
into the Gulf Stream and transported northeastward away from the
site?
Warm-Core Gulf Stream Eddies
* Can eddies transport sludge from the 106-Mile Site onto the
continental shelf or into important fishery areas?
* Do strong eddy-induced currents increase nearfield sludge dilution?
* Will sludge dumped within an eddy remain trapped inside the eddy
for a period of months?
* Do individual eddies revisit the 106-Mile Site and thus represent a
mechanism for sludge recirculation through the site?
Mesoscale Eddies at the Shelf/SIope Front
* Do the mesoscale and submesoscalt eddies that are found at the edge
of the continental shelf represent an important mechanism for the
transport of slope water through the shelf/slope front and onto the
continental shelf?
26
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Shelfwater Events
Does the shelfwater/slopewater front move offshore as far as the
106-Mile Site?
Will sludge discharged within a shelfwater event at the site be
transported back onto the shelf?
Project results that help to answer these technical questions/issues are
summarized below.
MASAR (Study 1)
Using the extensive hydrographic and moored current meter data sets
generated by the MASAR program, and historic data from previous measurement
programs in the region, Csanady and Hamilton (1988) have developed a
conceptual model of the circulation within the slope sea, the region that
lies between the Gulf Stream and the continental shelf (Figure 4). The
prominent western component of this slope sea gyre is expected to vary in
size and intensity, as a result of with changes in the large-scale wind
forcing, the location of the Gulf Stream, and variations in the inflow of
Labrador Sea water from the northeast. The 106-Mile Site is situated in the
strongest part of the southwestward-f lowing inshore arm of the anticlockwise
(cyclonic) slope sea gyre. This result is consistent with the predominantly
southwestward ("10 cm/s) mean currents that were observed near the 106-Mile
Site during MASAR and other studies.
This conceptualized model of the circulation within the slope sea
(Figure 4) is intended to represent the "mean" circulation in the absence of
eddies spawned from the Gulf Stream and the she If /slope front. The MASAR
results suggest that this elliptical circulation is present on the slope
roughly 85 percent of the time; eddies and other short-lived, small-scale
processes are present at the site for the remainder of the time (roughly 15%
on an annual basis). Currents associated with these "transient" (2- to 20-
day) events can be 5 to 15 times greater than the typical southwestward
slopewater flow, and current directions can vary by 180° over periods of a
day or less during these events.
27
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50°-
45°-
Slope Sea Gyre
Shelf Edge
70'
60'
50°
FIGURE 4. CONCEPTUAL MODEL OF THE CIRCULATION IN THE SLOPE HATER REGION, AS
PRESENTED BY CSANADY AND HAMILTON (1988).
28
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These and other significant MASAR results that pertain to the currents
and circulation at the 106-Mile Site are summarized below:
* In the absence of eddies and other transient features, currents at
the site are primarily directed toward the southwest, with mean
speeds that vary from 20 cm/s above 250 m to about i cm/s near
1000 m. This southwestward flow is consistent with existing
theories of a cyclonic slope sea gyre whose inshore, southwestward
flow coincides with the location of the 106-Mile Site.
* The strength of the slope sea gyre may have a seasonal dependence,
with strong flow during winter and apparent stagnation during
summer.
* The position of the Gulf Stream has an indirect, yet significant
effect on the strength of the southwestward flow of slope water in
the vicinity of the 106-Mile Site. When the axis of the Gulf
Stream is displaced northward of its mean position, the slope sea
gyre is constricted and southwestward currents at the site are
intensified.
* Analyses of satellite thermal imagery suggest that water from the
106-Mile Site often travels southwestward, to a point near Cape
Hatteras, where the slope water is constricted between the
continental shelf and the Gulf Stream. At this location, slope
water is believed to be advected toward the northeast along the
northern side of the Gulf Stream, thus creating the southern arm of
the cyclonic slope sea gyre.
* During the passage of warm-core Gulf Stream eddies, current speeds
above 100 m can exceed 1 m/s, whereas maximum speeds at 1000 ra are
on the order of 30 cm/s. Current directions during the passage of
eddies may vary greatly over a period of a few days.
In the absence of large perturbations such as warm-core eddies,
currents may be spatially coherent over horizontal scales of 100 to
200 km. During eddy events, currents lack spatial coherence beyond
a few tens of kilometers.
Submesoscale (30 to 50 km diameter) eddies are a common feature at
the edge of the continental shelf. These eddies represent a
significant mechanism for driving intrusions of slope water onto
the shelf. Cross-frontal transfer of water (and potentially,
sludge) is more likely during summer than winter, on account of
seasonal variations in horizontal temperature and density
gradients.
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SEEP (Study 21
The primary focus of phase 1 of the multidisciplinary Shelf Edge
Exchange Program (SEEP-I) was to determine the fate of fine-grained particles
in the continental shelf water column south of New England. The dynamics in
the adjacent slopewater region was also a topic of investigation because of
its supposed effect upon the sedimentation of particles onto the slope.
Commensurate with these objectives, the majority of the SEEP-I moored current
measurements were made on the outer shelf and upper slope region south of New
England (near 71°W). Although SEEP-I generated a relatively large number of
year-long records of currents, temperature, and turbidity throughout the
water column inshore of the 500-m isobath, only one current record was
obtained from the upper 250 m of the wat.er column offshore of the 500-m
isobath. Thus, with regard to the currents and circulation at the 106-Mile
Site, the SEEP-I results are useful for resolving the dynamics at the
shelf/siope front, but they contribute little to our knowledge of the current
variability further offshore, in the vicinity of the 106-Mile Site.
The SEEP-I results that pertain to currents and exchange of water
masses at the shelf/slope front are summarized below. These results have
been presented in the following articles: Walsh et al. (1988); Houghton et
al. (1988); Aikman et al. (1988)j and Flagg (1988).
At the shelf break south of Hew England, the SEEP-I results
confirmed a net offshore flow in the surface layer (0 to 40 m) as
well as in the bottom (~30 m thick) Ekman layer. Onshore flow was
observed at mid-depth.
Hind-induced upwelling within the slope sea is weak, such that only
20 percent of the slope water eventually enters the shelfwater
region.
Mean currents are westward (alongshore) on both the shelf and
slope, but current speeds are significantly greater on the shelf
than further offshore.
There is a clear minimum in kinetic energy (current speed) on the
mid-slope compared to sites further inshore and offshore. This
minimum would support the hypothesis of increased particle
settling on the mid-slope and eventual down-slope transport of
particles within the bottom nepheloid layer.
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Horizontal exchange of water (and temperature) through the
shelf/slope front exhibits a strong seasonal dependence. In winter,
the front is characterized by a sharp temperature gradient that
fluctuates over distances of 10-20 km on time scales of 4 to 20
days. Cross-frontal exchange exhibits high short-term variance in
winter, but zero net transfer. In summer, shelf and slope waters
become connected along isopycnal surfaces, with the result of
significant onshore mass ana heat flux across the shelf/slope
front.
Internal waves generated at the shelf/slope front can produce a
significant bottom mixed layer that can result in significant
cross-frontal exchange of shelf and slope waters, and suspended
particulate mttter,
During the passage of a warm-core Gulf Stream eddy along the slope,
the eddy-induced onshore heat flux was large, and 3 times greater
than the offshore flux, but its effect was not detected on the
continental shelf.
EPA Current Measurements at the 106-Mile Site (Study 7)
Under contract to EPA, Battelie and SAIC conducted a 7-month moored
current measurement program to monitor the current structure in the upper
1000 m of the water column in the vicinity of the 106-Mile Site. The
measurements were intended to provide more site-specific current information,
with increased vertical resolution, than that resulting from the MASAR
program. Current meters were situated at depths of 50, 100, 250, and IQOO m
on each of the two moorings bracketing the 106-Mile Site. Although only two
current records were obtained from depths above 250 m during this measurement
program, a number of interesting results arose from this 7-month (September
through April) program. The results pertinent to the issue of sludge
disposal at the 106-Mile Site are summarized below:
* During the 7-month deployment period, currents were highly variable
due to a wide variety of physical processes including a large
warm-core Gulf Stream eddy, two smaller warm eddies, cool
filaments of shelf water extruded from the shelf by the eddies,
warm parcels of water extending from Gulf Stream meanders, moderate
southwestward flow of the slope sea gyre, and strong inertial
currents associated with intense winter storms.
* Some of these processes had not been detected during previous
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current measurement programs in the vicinity of the 106-Mile Site
(e.g., MASAR) because of the lack of sampling above 100 m.
For the duration of the 7-month records the mean current speed was
6,5 cm/s directed toward the southwest (along the isobaths); the
mean current was remarkably uniform with depths between 50 and 1000
m.
During the passage of the warm-core Gulf Stream eddy, mean currents
in the upper 250 m of the water column were on the order of 15 cm/s
and directed toward the northeast. The mean current speed at 1000
m during this event was 5 cm/s toward the southwest.
Southwestward currents during the EPA measurement program were
roughly half the speed of currents observed during the MASAR
program. The intensification of the slope sea gyre during MASAR
was a result of a prolonged northward displacement of the Gulf
Stream.
Intense current oscillations having amplitudes of 30 cm/s were
observed during the passage of the warm-core Gulf Stream eddy.
These intense current "jet" structures have been previously
observed at the outer edges of eddies (Joyce and Stalcup, 1984).
Spectral analysis of the current records illustrates that warm-core
eddies are responsible for the major portion of current
variability, at periods greater than 10 days. Inertial currents
dominate the high frequency current variability, with lesser
contribution from the M2 semidiurnal tidal constituent.
Along-shore currents at the two mooring sites were not coherent
over the ?5-km mooring spacing, presumably because of the current
variability imparted by the eddies. For low frequencies, onshore
currents were highly coherent yet 180° out of phase at the two
mooring sites.
Analysis of Historical Current Records (Study 8)
This study represents the most comprehensive numerical analysis of the
large number of moored current measurements that were made along the
continental slope region of the U.S. east coast (between 69* and 73°W) during
the period from 1968 through 1981. This Eulerian database consisted of 150
separate records constituting roughly 300 months of current data. A major
result of this extensive analysis of historic current data is that, to a
first approximation, it is reasonable to use the long-tern statistics
gathered from a wide array of station locations along the U.S. east coast to
32
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describe the basic features of the slope circulation in the vicinity of the
106-Mile Site. On this basis, the following results can be applied to the
current regime at the 106-Mile Site:
Monthly averaged current data reveal an isobath-parallel flow
toward the west or southwest in the slopewater region. This mean
current system extends throughout the water column and across the
width of the slope water region from the shelf break to at least
150 km offshore.
* Monthly mean currents are strongest above 200 mt with speeds
ranging up to 50 cm/s and averages in excess of 10 cm/s.
Variations in current speeds and directions are also greatest near
the surface.
* Warm-core Gulf Stream eddies reprtsent the major source of current
variability within the slopewater region. Current speeds in
excess of 1 m/s may persist for periods of several days during
these events.
Although current speeds decrease consistently with depth over the
water column, there does not appear to be a consistent pattern to
the depth dependence of current direction. This variability of the
vertical current structure is significant because it implies that
shear dispersion is an effective mechanism for the dispersion of
sludge dumped at the 106-Mile Site.
* Mean residence time of water within an area corresponding to the
106-Mile Site is expected to be less than a few days. Periods of
weak currents (e.g., <5 cm/s) are observed on an infrequent basis
(~10%) and generally do not persist for periods of more than 2
days.
* Periods of shoreward currents are infrequent, with an incidence of
roughly 15 percent. The speed of these currents would be
sufficient to carry sludge from the 106-Mile Site to the edge of
the continental shelf within a period of several days.
* Short-term recirculation events, which would return sludge to the
106-Mile Site within periods of a few weeks or less, are rare.
The long-term fate of sludge dumped at the 106-Mile Site appears to
be entrainment by the Gulf Stream within a period of roughly 1
month, with little likelihood of subsequent large-scale
recirculation to the slopewater region.
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PHfter Trajectory Studies
Over the past 10 years, Or. Thomas Rossby at the University of Rhode
Island has conducted a variety of lagrangian drifter studies to investigate
the mid-depth circulation within the Gulf Stream and throughout the western
North Atlantic. The initial studies used neutrally buoyant SOFAR (sound
fixing and ranging) floats that transmitted low-frequency sound signals to
allow tracking via submerged, coastal, acoustic receivers. Since 1984,
Rossby has used RAFOS (the inverse of SOFAR) floats to further investigate
the dynamics within the Gulf Stream. RAFOS floats listen to moored sound
sources, which is opposite to SOFAR floats, which are transmitters. RAFOS
floats also have the added advantage that they actively follow isopycnal
(constant density) surfaces, which yields a better three-dimensional
trajectory of water parcels.
Bower et al. (1986) have presented a summary of RAFOS data from the
vicinity of the Gulf Stream which were compiled during 1984 and 1985. Figure
5 presents a "spaghetti diagram" of float trajectories that were acquired
from floats deployed in the Gulf Stream offshore Cape Hatteras (near 35°N).
The majority of these trajectories followed the core of the Gulf Stream
toward the northeast, but three floats exited the stream near 38°N, 72°W and
entered the slope water near the 106-Mile Site. These floats moved northward
until they reached the continental slope (~2QOQ-ra isobath in Figure 5), then
began to move southwestward along the isobaths in agreement with typical
slope water flow. Curiously, these floats turned southward to reenter the
Gulf Stream about 2 weeks after having entered the slope water. Although
these few trajectories do not provide a statistical representation of float
trajectories in the vicinity of the 106-Mile Site, these results illustrate
that sludge dumped at the 106-Mile Site may, on occasion, enter the Gulf
Stream relatively soon after disposal. In this scenario, sludge would be
transported rapidly toward the northeast with little possibility of
recirculation through the site.
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SSW
CO
Ul
4 ON
35N
76H
70N
6SH
40N
3SN
BOH
S6H
FIGURE 5. TRAJECTORIES OF SUBSURFACE DRIFTERS LAUNCHED IN THE GULF STREAM
OFFSHORE NORTH CAROLINA (NEAR 35% 75°W), FROM BOWER. O'GARA AND
ROSSBY (1985).
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4.2 MARINE CHEMISTRY
The null hypotheses directed at the assessment of nearfield and farfield
fate raise the following information issues that come under the general
category of marine chemistry;
* Metils
* Organics
* Dissolved oxygen
* pH levels
Analyses for metals and organic compounds are an integral part of the
106-Mile Site monitoring plan. As implied by references to LPC and HQC in
H07 and Ho8, bioaccumulation of sludge constituents in Hol2 and H019,
settling of sludge particles to the sea floor in Hol7, and surface microlayer
accumulation in Hol3, measureients of concentrations of dissolved metals and
organic compounds are needed to determine the fate of sludge constituents.
Dissolved oxygen concentrations and pH, referenced in H09, address impacts to
the water column in the immediate vicinity of disposal activity.
Data available from the studies reviewed for this report are not
sufficient to test the applicable null hypotheses. However, these studies,
particularly the baseline surveys (Studies 5 and 6), provide important
baseline data for comparison with the results of future monitoring
activities.
Because none of the studies reviewed for this report specifically
sampled the surface microlayer, there are no baseline data available to
address the issue, raised in Ho20, of accumulation of sludge constituents in
the surface microlayer.
The issue of bioaccumulation of sludge constituents in the tissues of
commercially important/important prey species is raised in Hol2 and H018.
Although bioaccuinulation is monitored to provide an indication of change in
biological conditions, the topic is included in this subsection because
bioaccuiulation studies involve chemical measurements. Although Studies 3A
36
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and 4A, included analyses of benthic fauna! tissues, none of the studies
specifically targeted tissue analyses of commercial and prey species. Thus,
there are insufficient baseline data against which to compare the results of
future chemical analyses of these species.
Because it is beyond the scope of this report to present the chemical
data generated in the studies reviewed, this section will describe the types
of data available (e.g., metals in sediments, surface water) and reference
reports where data are presented. Wherever possible, this section will
summarize study conclusions.
4.2.1 Metals
Analyses of metals were conducted in many of the studies reviewed for
this report (Table 3). For purposes of obtaining baseline data for testing
monitoring hypotheses, the matrices of interest are the surface microlayer
(H013), the water column (H07 and H08), the tissues of commercially important
and prey species (H012 and Hol9), and sediments (H017). Because none of the
studies reviewed included microlayer sampling, data are not available for
metals concentrations in this matrix.
Studies 3A and_4A
The studies of biological processes on the Mid- and North Atlantic slope
and rise included analyses of metals in brittle stars (Ophiomusium lymani),
sea urchins (Echinus affinis). and red crabs (Geryon quinquidens). which are
fished commercially in some areas (Maciolek et a!., I987a; Maciolek et aU,
1987b). The metals analyzed in the whole body tissue samples (A1, Ba, Cd,
Cr, Cu, Fe, Mn, Ni, Pb, V, Zn, and Hg) were near detection limits with the
exception of aluminum, iron, and zinc. The authors reported that the higher
levels of aluminum, iron, and zinc may have been associated with ingested
sediment.
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Studies 36 and 4B
Studies 31 and 4B provide results from the analyses of trace metals in
bottom sediments from the Mid- and North Atlantic slope and rise (Bothner et
a!., 1987a; Bothner et al., 1987b). Twelve metals (AT, Ba, Cd, Cr, Cu, Fe,
Hg, Mn, Ni, Pb, V, and Zn) were analyzed in sediments collected over a 2-year
period. Metal concentrations in samplts from the Mid- and North Atlantic
slope and rise were lower than those reported for world average shales,
indicating no major contamination. In sediments from some stations adjacent
to drilling rigs, barium, a major element in drilling mud, exhibited a small
increase (< 32 percent) in concentration over the study period , An
enrichment of lead was detected in surface sediments relative to deeper
sediments. This enrichment was presumed to result from the onshore
combustion of leaded fuels.
Baseline Surveys (Studies 5A, 5C. 5D)
As part of the August 1984 survey of the 106-Mile Site (Study 5A),
filtered seawater and seawater particulates were analyzed for silver, iron,
Itad, and zinc ( EPA , 1987a). Only line was detected in the filtered
stawater samples, although the accuracy of the results is questionable
because of the high concentrations of line in the field blanks. Zinc and
iron were the only metals detected in seawater particulates, with the Hudson
Canyon station having higher metals concentrations than the other areas.
Sediments were analyzed for iron, mercury, lead, and zincj measurable
concentrations were reported for all sediment samples.
The February 1986 survey to the 106-Mile Site (Study 5C) included
analyses of metals in unfiltered seawater (i.e., including particulates) and
in sediments ( EPA , 1987a). For stawater samples, copper, lead, mercury,
silver, and zinc were not detected above the field blank levels. Cadmium was
only detected below the thermocline. Chromium concentrations were slightly
higher in the slope water than on the shelf. Iron concentrations were
significantly higher at the shelf station than at the shelf break or on the
slope. Most trace metal concentrations were more than a thousand times lower
than IPA's WQC for seawater. Sediments were analyzed for silver, cadmium,
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chromium, copper, iron, mercury, lead, and zinc. Concentrations were
generally lower than those reported from the 1984 survey for comparable
metals. However, the authors suggested that the variability was most likely
due to differences in analytical technique.
The August 1986 survey to the 106-Mile Site (Study 5D) included analyses
of unfiltered seawater samples for silver, cadmium, chromium, copper, iron,
lead, and 2inc ( EPA , 1986). Silver and lead were not detected in any of
the samples. The reported concentrations for cadmium, chromium, iron, and
zinc were higher than generally accepted values for the area. Copper
concentrations were consistent with previously reported values.
In summary the studies reviewed herein provide some baseline data for
concentrations of metals in the water column and in sediments. Because many
metals were not found in samples above detection limits, additional data and
lower detection limits are needed to establish actual baseline
concentrations. The studies do not provide data on metals concentrations in
the surface microlayer nor in the tissues of prey and commercially important
species, with the exception of red crabs, indicating a need for baseline data
of this type.
4.2.2 Organic Compounds
Analyses of organic compounds were performed in many of the studies in
the vicinity of the 106-Mile Site (Table 3). As with metals, the matrices
of interest for relating results to the null hypotheses are the surface
microlayer (Hol3), the water column (H07 and Ho8), the tissues of
commercially important and prey species (H012 and H019), and sediments
(H017).
Studies 3A and 4A
Some sediments and tissues from the Mid- and North Atlantic slope and
rise were analyzed for organic constituents as part of Studies 3A and 4A
(Maciolek et al.( 1987a; Maciolek et al., 1987b). Total hydrocarbon
concentrations in sediments ranged between 2.9 and 27.1 pg/g dry weight at
North Atlantic stations and between 2.9 and 52.9 pg/g dry weight at Mid-
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Atlantic stations (see Figure 2). Concentrations of polynuclear aromatic
hydrocarbons (PAH) in general covaried with total hydrocarbon concentrations,
ranging between 10 and 364 ng/g dry weight at North Atlantic stations and
between 66 and 11S7 ng/g dry weight at Mid-Atlantic stations. The
concentrations at the Mid-Atlantic stations appeared similar to, but higher
than, concentrations found in earlier studies in the same geographic area.
Sediments from both studies were also analyzed for total organic carbon,
hydrogen, and nitrogen. In general, sediments from the Mid-Atlantic stations
contained higher levels of organic carbon, hydrogen, and nitrogen.
Tissues of brittle stars (Ophiomusium lymani) and red crabs (Geryon
quinquidens) from North Atlantic stations contained very low hydrocarbon
concentrations. Total hydrocarbon concentrations in brittle stars ranged
between 29.S and 54.6 ^9/g wet weight whereas concentrations in red crabs
ranged between 5.5 and 11.8 pg/g wet weight. Hydrocarbon concentrations in
brittle stars and sea urchins (Echinus affinis) froi Mid-Atlantic stations
ranged between 27.4 and 163.1 /ig/g wet weight.
Baseline Surveys (Studies 5A. SB. 5C. 5D. and 6)
Sediment samples were collected for analyses of organic compounds during
the August 1984 (Study 5A) and August 1985 (Study 5B) surveys to the 106-Mile
Site ( EPA , 198?a). With the exception of 4,4'-DDT, which was detected
in trace* amounts along a southwest transect through the 106-Mile Site, no
organic pollutants were detected in any sediments.
Filtered seawater and seawater particulates were collected for organics
analyses during the February 1986 (Study 5C) survey to the 106-Mile Site
(Battelle, 1987c). Samples were analyzed for PAH, polychlorinated biphenyls
(PCB), pesticides, and coprostanol. With the exception of aldrin, a
pesticide found in the slope samples, and coprostanol in the shelf sample, no
pollutants of interest were found in seawater particulate samples. PCB were
not detected in any of the samples in either the particulate or filtrate
phase. Filtered seawater samples did contain some analytes in concentrations
above method detection limits. Naphthalenes, phenanthrenes, and
dibenzothiophenes were only found in shelf waters. A pesticide, a-BHC, was
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found In both shelf and slope waters. Heptachlor and aldrin were also found
in several samples.
Filtered seawater and seawater particulate samples were collected for
organics analyses during the August 1986 (Study 50) survey to the 106-Mile
Site ( EPA , 1992b). Filtered seawater samples were analyzed for PAH;
particulate samples were analyzed for PCB, pesticides, and coprostanol.
Seawater samples from all stations at both sampling depths (surface and
subpycnocline) contained naphthalene and alkylated naphthalenes. The only
other PAH detected, Ci-phenanthrene, was detected in some seawater samples.
Mo PCB or coprostanol were detected in any particulate samples. Some
pesticides U-BHC, £-BHC, f-BHC, S-BHC, 4,4>-DDE, 4,4'-DDT, and heptachlor)
were detected in some particulatt samples.
The November 1985 (Study 6) baseline survey of the North Atlantic
Incineration Site included sampling of filtered seawater and seawater
particulates. Results were reported for analyses of PCB, PAH, pesticides,
chlorobenzenes, polychlorinated dibenzo-p-dioxins (PCDD), and
polychlorinated dibenzofurans (PCDF}( EPA , 1987b), In all cases but two,
no PCDD nor PCOF were detected in seawater samples* Measurable PCB were
detected in only one seawater sample. Chlorobenzenes were not detected in
any seawater samples. Low levels of PAH were detected in seawater samples
from all but one station; no PAH were detected in any particulate samples.
Low levels of pesticides were detected in seawater and particulate samples
from two out of the five stations sampled.
In summary the data generated in the studies reviewed herein provide
much baseline data for organics in seawater, particulates, and sediments.
The studies do not provide baseline data for the surface microlayer or, with
the exception of red crabs, the tissues of commercially important and prey
species.
4.2.3 Dissolved Oxygen and pH
The effects of sludge disposal on dissolved oxygen concentration and pH
in the vicinity of disposal are issues raised in H09. Because these
parameters are expected to be routinely measured during all monitoring
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activities, the value of historical results are limited. Dissolved oxygen
concentrations have been reported for Studies 1, 3A, 4A, SCf SO, and 6. A
typical range for reported dissolved oxygen concentrations is 7.0 - 7.8 mg/l
( EPA , 1987b) in surface water and 4.9 - 6.6 mg/L ( EPA , I9BBa) at
250-ro depths. Measurements of pH have been reported for Studies 5C, 5D, and
6. Typically, pH ranges between 7.8 and 8.3 ( EPA , 1988a).
4.3 MARINE BIOLOGY
The null hypotheses directed at the assessment of short- and long-term
effects (Tiers 2 and 4) focus on changes in biological conditions within and
near the 106-Mile Site. The specific marine biological measurements dictated
by the hypotheses are as follows;
* Plankton communities
* Primary productivity
Planktonic biomass
* Commercially important species
Important prey species
* Endangered species
Benthic communities
Pathogens
Because none of the studies reviewed in this report were specifically
directed at monitoring short- or long-term effects of sludge disposal at the
106-Mile Site, none of the null hypotheses in Tiers 2 and 4 can be tested
using available data. However, the data that are available provide a
baseline against which future monitoring data can be compared.
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4.3.1 Plankton Communities
The issue of the long-tern effects of sludge disposal on plankton
communities is raised in H022. Primary productivity and planktonic bioiass,
issues found in Holl, are Issues that are also related to plankton
communities.
Baseline Surveys (Studies 5C. 5D. and 6)
The most recent baseline surveys-(Studies 5C and 5D) of the 106-Mile
Site and the baseline survey to the North Atlantic Incineration Site (Study
6) have included measurements of chlorophyll (as chlorophyll a),
phaeophytin, and adenosine triphosphate (ATP). ATP is used as an indication
of the biomass of live microorganisms, including bacteria, phytoplankton, and
zooplankton; chlorophyll is used as an indication of the quantity of
phytoplankton 1n seawaterj and phaeophytin is a degradation product of
chlorophyll. Whereas ATP and chlorophyll provide an indication of
planktonic biomass and primary productivity, the ratio of chlorophyll to
phaeophytin provides an indication of the health of the phytoplankton
population. The ratio of chlorophyll to phaeophytin decreases in
phytoplankton at depths below the euphotic zone or in areas of heavy
zooplankton grazing. EPA (1987a, l§87b» 1988a) has reported results of
these measurements at stations within and in the vicinity of the 106-Mile
Site,* normal chlorophyll/phaeophytin range between 1.4 and 1.7.
SEEP (Study 2)
As part of Study 2, Walsh et al. (1988b) conducted high-frequency
sampling of the 1984 spring bloom within the Mid-fttlantic Bight. Data were
obtained from moored fluoroieters, transmissometers, thermistors, and current
meters deployed south of Martha's Vineyard and Long Island,* airborne sensors,'
and shipboard bottle and fluorescence-conductivity-temperature-depth (F/CTD)
casts. Data were used to estimate the export of phytoplankton from the Mid-
Atlantic during the 1984 spring bloom and to provide validation data for a
simulation model (Walsh et al., 1988c). The results suggested a seaward
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export of perhaps 0.20 mg chlorophyll nr3 day! at depths of 75-81 m during
February to April 1984. This horizontal loss of algal carbon would represent
19-67 percent of the March-April 1984 primary production within the overlying
euphotic zone. Estimates of the vertical flux of organic carbon suggested
that approximately 50 percent of the carbon export at the shelf break might
be derived from the adjacent overlying water column, with the rest derived
from lateral injections of near-bottom particles originating on the inner
shelf.
Although the data generated in Study 2 may be of limited value in
testing the null hypotheses associated with plankton communities, the data
generated from Studies 5C, 5D, and 6 provide important baseline information
for comparing results of future monitoring at the 106-Mile Site.
4.3.2 Commercial. Prey, and Endangered Species
The issue of bioaccumulation of sludge constituents by important
commercial or prey species is raised in H012 (short-term effects) and Hol8
(long-term effects). The long-term effect of sludge constituents on the
distribution of endangered species is addressed in H017.
As indicated in Table 3, observations of cetaceans, marine turtles, and
seabirds have been conducted by the Manomet Bird Observatory as part of
several surveys to the 106-Mile Site and the North Atlantic Incineration Site
(Battelle, 1984; EPA , 1987a; EPA , 1987b; EPA , 1988a).
Cetaceans and marine turtles observed In the vicinity of the 106-Mile Site
include sperm, minke, fin, pilot, and possibly sei whales; dolphins, grampus,
and leatherback turtles. Several species of seabirds, which are not expected
to be directly affected by sludge disposal, were also observed. It should be
noted that not all of the species observed (e.g., pilot whales, dolphins,
grampus) are on the endangered list. Endangered species distributions were
also reported as part of the Northeast Monitoring Program (NOAA, 1983).
The National Oceanic and Atmospheric Administration (NOAA, 1983) has
reported on the distribution of fish and fisheries in the vicinity of the
106-Mile Site. The survey, conducted as part of the Northeast Monitoring
Program, includes commercially important and important prey species.
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Because results of the Northeast Monitoring Program are not recent,
this program was not selected as one of the primary programs (Table 3)
reviewed for this report. More recent data on distributions of endangered
species are available (Battelle, 1984; EPA , 1987«; £PA , 1987b;
EPA , 1988a) and provide more relevant baseline data for comparison with
future monitoring studies. None of the studies reviewed for this report
specifically address distributions of important commercial or prey species.
4.3.3 Benthie Communities
The issue of long-tern effects on benthic community structure is raised
in H020. Comprehensive studies of benthic community structure along the
Atlantic slope and rise in the vicinity of the 106-Mile Site have been
conducted as part of Studies 3 and 4, A wealth of baseline data has been
generated and reported by Maciolek et al. (1987a, 1987b).
Benthic Infauna
The diversity of benthic infaunal species was evaluated by Hurlbert
rarefaction, species accumulation over increasing area, and Shannon-Wiener
methods. For the Mid-Atlantic study (Maciolek et al., 1987a), diversity at
the mid-slope (2020 - 2195m) stations (176 to 184 species per 1000
individuals) was greater than that at the remaining stations (144 to 171
species per 1000 individuals). A similar result was reported for the North
Atlantic study (Maciolek et al, 1987b) where the raid-slope stations (1220 -
1350m) exhibited higher diversities than either shallower or deeper stations.
Polychaetes comprised the majority of dominant species at all depth intervals
within the Mid- and North Atlantic study areas. The top dominant at stations
deeper than 2020 m was the spionid polychaete Aurospio dibranchiata«
Infaunal communities at the shallower, mid-slope stations were dominated by
the sipunculan Aspidoslphon zinni and the aplacophoran mollusc Prochaetoderma
yengei. Water depth and sediment grain size were significant determinants of
infaunal community structure. The diversity of the benthic infaunal
community was stable over all sampling seasons. Wet, dry, and ash-free dry
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weights were also reported for both the Mid-Atlantic and North Atlantic
studies.
Benthic recolonization experiments were conducted as part of Studies 3A
and 4A. In a significant result from the Mid-Atlantic study, the 6-month
experiment conducted in 1985 showed recolonization by a different fauna than
was observed over the same time period in 1984 (Maciolek et al.( 1987a).
Results from both studies suggested that recolonization of disturbed or
defaunated sediments is very slow (on the order of years) in the deep sea
relative to shallow coastal water depths (weeks to months).
Benthic epifaunal community structure was also examined as part of
Studies 3A and 4A. The results of the Mid-Atlantic study indicated trends in
epifaunal trophic structure and species composition which were related to a
combination of depth and topography (Maciolek et al., 1987a). The highest
density of total megafauna (5-6 individuals/m2) was observed at depths
between 1800 and 1900 m. Fauna! density was lower (3-4 individuals/m2) at
depths between 1900 and 2350 m. Higher densities were also found on shallow
ridges and in flat valleys than on steep slopes and in deep valleys. Similar
densities of total megafauna were recorded for the western transect of the
North Atlantic study at depths between 1800 and 2200 m (Maciolek et al.,
1987b). Although filter feeders and deposit feeders were both dominant,
their relative proportion shifted according to bottom topography. A higher
proportion of filter feeders was found on ridges and in flat valleys; a
higher proportion of deposit feeders was found on steep slopes and in deep
valleys.- No consistent seasonal or yearly differences in epifaunal community
structure were reported for either study.
The data obtained as part of the studies of biological processes on the
U.S. Mid- and North Atlantic slope and rise provide much recent baseline
data on benthic communities in the vicinity of the 106-Mile Site. Although
these data are not sufficient to test the relevant null hypothesis H020»
they may be used to compare results of future monitoring studies.
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4.3.4 Pathogens
None of the studies reviewed for this report included baseline
information regarding pathogens in the vicinity of the 106-Mile Site. This
lack of information will be addressed in future monitoring studies in order
to test the related null hypothesis, Ho23.
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Across the New England Continental Shelf Break and Slope. Contin.
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Bothner, M.E., E.Y. Campbell, 6.P. DiLusio, C.M. Pirmeter, R.R. Rendlgs,
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Walsh, J.J., P.E. Biscayne, and 6.T. Csanady. 1988a. The 1983-84 Shelf
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highlights. Contiru Shelf. Res, In Press.
Walsh, J.J., C.D. Wirick, L.J. Pletrafesa, I.E. Whitledge, F.E. Hoge,
and R.N. Swift. 1988b. High-frequency sampling of the 1984
spring bloom within the Mid-Atlantic Bight; synoptic shipboard,
aircraft, and in situ perspectives of the SEEP - I experiment.
Contln. Shelf Res. In Press.
Walsh, J.J., D.A. Dieterle, and M.B. Heyers. 1988c. A simulation
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Bight. Contln. Shelf Res. In Press
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DumpsHe 106. In May 1974 Baseline Investigation of Deepwater
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