Proceedings of the North Atlantic Submarine Canyons Workshop : February 7-9, 1989

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OCS Study
MMS 89-0016

Proceedings of the
North Atlantic Submarine Canyons
Workshop

February 7-9, 1989

Volume |
Synthesis Summary

DOCUMENT
LIBRARY

Woods Hole Oceanographic
institution

U. S. Department of the Interior
Minerals Management Service
Atlantic OCS Region

1989

Disclaimer

This report has been reviewed by the Minerals Management Service and approved
for publication. The opinions, findings, conclusions, or recommendations
expressed in the report are those of the authors, and do not necessarily
reflect the views or policies of the MMS. Mention of trade names or
commercial products does not constitute endorsement or recommendations for
use. This report has been technically reviewed according to contractual
specifications. It, however, is exempt from review by the MMS Technical
Publications Unit and the Regional Editor.

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OCS Study
MMS 89-0016

Proceedings of the
North Atlantic Submarine Canyons Workshop

February 7-9, 1989

Robert E. Miller
Contracting Officer’s Technical Representative

U.S. Department of the Interior
Minerals Management Service
Atlantic OCS Region

Vienna, Virginia

1989

Prepared for the Minerals Management Service
under contract No. 14-12-0001-30430 by:

Walcoff & Associates, Inc.

635 Slaters Lane, Suite 102

Alexandria, Virginia 22314
(703) 684-5588

§0272-101

REPORT DOCUMENTATION |": REPORT NO. 3. Recipient's Accession No.
PAGE OCS Study MMS 89-0016

4. Title and Subtitle 5. Report Date

Proceedings of the North Atlantic Submarine Canyons Workshop: February 7-9, 1989 Date Published: June 1989

7. Author(s) 8. Performing Organization Rept. No.

D. Aurand, R. Ayers, P. Boehm, M. Bothner, B. Butman, R. Cooper, F. Grassle, J. Hain, B. Hecker,
P. Hughes, J. Kraeuter, J. Lane, N. Maciolek, R. Miller, J. Neff, J. Ray, J. Teal, P. Valentine, B. Vild

9. Performing Organization Name and Address 10. Project/Task/Work Unit No.

Task 6
Walcoff & Associates, Inc.

635 Slaters Lane, Suite 102

Alexandria, Virginia 22314
11. Contract (C) or Grant (G) No.

(C) 14-12-0001 -30430
(G)
12. Sponsoring Organization Name and Address 13. Type of Report & Period Covered
U.S. Department of the Interior Final Report
Minerals Management Service, Atlantic OCS Region

381 Elden Street, Suite 1109
Herndon, Virginia 22070

15. Supplementary Notes

16. Abstract (Limit: 200 words)

A three-day workshop on North Atlantic submarine canyons was held in February 1989. About 20 participants reviewed available information and made
recommendations.

There are nine major submarine canyons along the southern flank of Georges Bank and several smaller ones. The canyons are unique habitats. Physical
and biological features are complex and heterogeneous—within canyons and between canyons. Of the total, two canyons-Lydonia and Oceanographer—
have been studied in detail. Lydonia is smaller, primarily low-energy, with deposition of fine-grained sediments. Oceanographer is larger, relatively high-
energy, with erosional scouring and little deposition.

The canyon heads, particularly those with boulder fields and "pueblo villages," are habitats and nursery grounds for commercial species that include tilefish
and lobsters. Attached filter-feeding faunas are common in some areas.

Metals and other contaminants from exploratory drilling are unlikely to cause environmental impacts beyond the vicinity of the wellsite. Many contaminants
are in forms biologically unavailable to marine organisms.

An oil spill would primarily cause surface-layer impacts--affecting fish eggs and larvae. Water-column impacts are unlikely. Transport of oil to the bottom
may occur, primarily in shallow water. Mechanisms are unknown, but may include adsorption onto sinking fine sediments and particles ("scavenging"), in-
cluding krill fecal pellets. Chemical effects on settling larvae may be more important than physical effects on the benthos.

Recommendations and findings include: 1) no rigs within 500 m of canyon boundary; 2) worst-case calculations indicate contaminants from drill site unlike-
ly to cause impacts; 3) produced water must meet discharge standards, with monitoring; and 4) there is insufficient information on possible impacts from
gas blowouts.
Research needs Included studies on sedimentary processes, canyon fisheries, additional canyon types, and studies linked to future drilling.

Revewers' comments, abstracts, an agenda, and an attendee list are appended.

. Document Analysis a. Descriptors
North Atlantic, submarine canyon, sedimentary processes, fishery, contaminants, drilling muds, continental shelt and slope, benthic fauna

b. Identifiers/Open-Ended Terms
c. COSATI Field/Group

18. Availability Statement 19. Security Class (This report) 21. No. of Pages
Unlimited Unclassified 593
20. Security Class (This page) 22. Price
Unclassified
(See Al — £39.18) ee Instructions on Reverse OPTIONAL FORM 272 (4-77)

(Formerly NTIS-35)
Department of Commerce

PREFACE

The purpose of this workshop was to provide a forum for the presentation
and discussion of the available environmental information on the geological,
biological, chemical, and physical characteristics of the North Atlantic
Submarine Canyons which incise the continental shelf of the Minerals
Management Service’s North Atlantic planning area. This environmental
information was presented by scientific experts from their respective fields.

The format of the workshop was designed to foster an open and free
scientific exchange of ideas, and opinions, with the primary focus placed on
reaching consensus with respect to the environmental effects of offshore
petroleum exploration and development activities on these submarine canyon

environments.

This report is organized into three major sections. The first section
contains the formal papers that were presented during the first day of the
workshop and the follow up questions and answers. The second section
consists of the roundtable discussions held on the second day focusing on the
geology and geochemistry, and biological communities of the North Atlantic
submarine canyons. The third section is the Final Summary Synthesis and
Conclusions reached by the workshop panel members.

This workshop was sponsored by the Atlantic OCS Regional Office of the
Minerals Management Service.

ACKNOWLEDGEMENTS

The Minerals Management Service wishes to express its sincere appreciation to
each of the workshop participants without whose diligence and cooperation,
this workshop effort would not have been possible. Further expressions of
gratitude are due to the Walcoff and Associates project staff for their
support in the coordination and logistics of the workshop, and especially to
the senior rapporteur, his staff, and the court reporter for their preparation
of the workshop summary synthesis and conclusion volume, and the transcript.

Grateful appreciation is also extended to the members of the Minerals
Management Service’s Branch of Environmental Studies and the Atlantic Region
OCS Environmental Studies Unit. Their cooperation and assistance prior to and
during the workshop aided significantly in the successful completion of this
deliberative approach to the resolution of complex and controversial

environmental issues.

Robert E. Miller, Ph.D.
Atlantic Region OCS
Minerals Management Service

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TABLE OF CONTENTS

PREFACE Pe ee ee a ee

ACKNOWLEDGEMENTS ee ag

DEFINITION OF NORTH ATLANTIC SUBMARINE CANYONS ‘
INTRODUCTORY REMARKS--Dr. Donald Aurand and Mr. James Lane
PRESENTATIONS .

Pre- and Post-Drilling Benchmarks and Monitoring Data of Ocean
Floor Fauna, Habitats, and Contaminant Loads in the Georges
Bank Submarine Canyons--Dr. Richard A. Cooper .

The Lydonia Canyon Experiment: Circulation, Hydrography, and
Sediment Transport--Dr. Bradford Butman .

Sedimentary Environments in Submarine Canyons and on the Outer
Shelf - Upper Slope of Georges Bank--Dr. Page C. Valentine

Toms Canyon Study--Dr. Robert C. Ayers, Jr.

Recent Developments in Industry Sponsored Research--Dr. James
RaVicg sais! ccnetnthae pA?

The Flux and Composition of Resuspended Sediment in Lydonia
Canyon: Implications for Pollutant Scavenging--Dr. Michael H.
Bothner. 2.4%

Overview of the Biogenic and Anthropogenic Hydrocarbon
Distributions in Sediments Along the North Atlantic

Margin--Dr. Paul D. Boehm. ......

Potential Effects of Drilling Effluents on Marine
Organisms--Dr. Jerry M. Neff ......

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ROUNDTABLE DISCUSSION: SUMMARY AND SYNTHESIS . .

FINAL SUMMARY SYNTHESIS AND CONCLUSIONS .

APPENDICES

Megafaunal Populations in Lydonia Canyon with Notes on Three
Other North Atlantic Canyons--Dr. Barbara Hecker

Benthic Infauna of Lydonia Canyon and the Adjacent Slope
Environment--Dr. Nancy J. Maciolek and Dr. J. Frederick Grassle

Massachusetts’ Perspective on Submarine Canyons and Drilling
Around These Canyons--Ms. Patricia E. Hughes

The Rhode Island Perspective on Submarine Canyons--Mr. Bruce F.
Vild.2

Geology and Geochemistry of North Atlantic Submarine Canyons--
Dr. Bradford Butman, Chairperson

Biological Communities of North Atlantic Submarine Canyons--
Dr. Barbara Hecker, Chairperson .

Conclusions .
Research Needs

A--Reviewers’ Comments
B--Abstracts
C--Workshop Agenda
D--List of Participants

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LIST OF FIGURES

The nine submarine canyons along the southern flank of
Georges Bank er ee ee

Georges Bank and currents .
Gulf Stream rings .
Mean Eulerian current .

Kinetic energy spectra of near-bottom currents on the shelf
and slope adjacent to Lydonia Canyon

Spatial distribution of energy in the near-bottom currents
along the axis of Lydonia Canyon

Percent current exceeds 20 cm/s .

Percent fine sediments in the surficial sediments on the shelf
and slope adjacent to Lydonia and Oceanographer Canyons .

Surficial sediment texture along the axis of Lydonia Canyon .

Histograms showing the flux of resuspended sediment at
different heights above the bottom haan fe

A. Histogram showing the relative mass of sediment
collected at station LCP

B. Schematic diagram showing position of teflon timing
layers and layers of coarser sediment

C. X radiograph of the sediment trap sample
D. Record of bottom stress
E. Calculated flux of trapped sediment .

Carbon-14 age of organic carbon in marine sediments from the
head of Lydonia . a ee

Concentration of barium in the fine fraction of material
collected in sediment traps .

Histogram showing the abundance of metals relative to world
average shales ar ee a

Isotope data suggest active processes in the canyon axis
Activity of plutonium-239/-240 with depth in sediment cores .

Seasonal variations in total hydrocarbon concentrations in
sediments . ee ee ee ee

Seasonal variations in pristane concentrations in sediments .
Map of Oceanographer, Heeltapper, and Filebottom Canyons

Map of Gilbert and Lydonia Canyons.

Map of Hydrographer Canyon

Cross section of 12 Georges Bank canyons and Hudson Canyon
at the 200-m isobath a ee Re eee ea

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LIST OF TABLES

Table 1. Sedimentary facies and sediment transport regimes for rims,
walls, and floors of high, moderate, and low energy canyons . . 27
Table 2. Comparison of mean silt-clay content and PAH concentrations in
SCUIMCHES & i0sr-¢.0..4 6 wee tee 4S oS Ge we ee ow eee OO

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DEFINITION:

North Atlantic submarine canyons (Figure 1) are V-shaped valleys
cut into the continental shelf and slope. They are highly
variable in length, size, relief, and wall steepness. The
largest, most well-developed canyons extend up to 25 km into the
shelf and seaward for much greater distances to the lower
continental slope and upper rise. The smallest canyons are
broad, shallow embayments of the outer shelf and upper slope.

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Figure 1. The nine major submarine canyons along the southern flank of
Georges Bank--the subject of the North Atlantic Submarine Canyons ae seen
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Not shown are several smaller canyons, such as Heeltapper and Dogbody.
eight squares on Georges Bank are the locations of the eight exploratory wells

drilled in 1980 and 1981.

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INTRODUCTORY REMARKS:
THE VIEW OF THE MINERALS MANAGEMENT SERVICE
ENVIRONMENTAL STUDIES PROGRAM

Dr. Donald Aurand
Branch of Environmental Studies
Minerals Management Service--Headquarters
Reston, VA
and
Mr. James Lane
Environmental Studies Unit
Minerals Management Service--Atlantic OCS Region
Vienna, VA

The goal of this workshop on North Atlantic submarine canyons is to
provide a forum for the synthesis and dissemination of available information
on submarine canyons of the North Atlantic and for discussion by scientific
experts and concerned parties. This presentation and discussion will lead, it
is hoped, to identifying the points of agreement, points of disagreement, and
recommendations. The foregoing will focus largely on technical material, but
will not exclude policy aspects.

A NEW APPROACH

This workshop represents a new approach for the Environmental Studies
Program. About 2 years ago, during a studies planning session, it was
recognized that additional field studies in canyon head areas would not
necessarily provide new data or resolve outstanding questions. What was more
important was to disseminate existing information and foster discussion. This
was consistent with a recent audit of the Minerals Management Service (MMS)
Environmental Studies Program by the General Accounting Office--which was
generally favorable to the program, but which suggested the need for improved
information transfer and dissemination.

Studies on North Atlantic submarine canyons had been underway for some
time, data were available, and a number of publications on the topic had
recently been completed. For this reason, submarine canyons were identified
as an appropriate topic for a new studies program approach--that of focusing a

workshop on a given topic.

THE ENVIRONMENTAL STUDIES PROGRAM

Historically, the role of the Environmental Studies Program has been
contracting for studies aimed at acquiring field and laboratory data and for
literature summaries or bibliographies. The scientific studies and literature
summaries are designed to:

mw enhance the leasing process by providing information for prediction of
impacts,

ws provide information on ways impacts to human, marine, biological, and
coastal environments can occur,

w ensure that available information is in a form useful to decision
makers, and

mw provide a basis for future monitoring of Outer Continental Shelf (OCS)
activities.

We no longer need to focus entirely on these traditional types of
studies, but need to do more with risk perception and communication. At
present, there is a growing trend toward synthesis reports and open-forum
discussions.

WORKSHOP HYPOTHESES

To provide a basis for the workshop and to stimulate discussion, two
hypotheses were proposed:

1. In submarine canyons of the North Atlantic margin where erosional
environments exist, the probability of serious environmental impact to
faunal assemblages from oil and gas activities in the vicinity of
canyon heads is low, and

2. In submarine canyons of the North Atlantic margin where depositional
environments may exist, the rate of accumulation of drilling-related
contaminants from oil and gas activities is slow enough not to present
serious environmental risks to faunal assemblages in the canyon heads.

To enhance exchange, the number of participants was limited, although a
number of observers have been accommodated.

NEW STUDIES?

Although much information is in hand, new studies are not ruled out.
While the program is not necessarily soliciting recommendations for new
studies, if there are technical issues that could be resolved through
scientific studies, a recommendation would be appropriate. Any new study
would need to be focused on an issue that can be resolved or narrowed, and
objectives, timing, needs, and users of the information must be clearly
identified.

FACTS AND VALUES

The focus of the workshop is on science, and the facts that support the
conclusions. A purpose of the workshop is to separate out value judgments
from the Environmental Studies Program. We can analyze elements of the risk
involved, but cannot decide if such risk is acceptable. The studies program
is not involved in making value judgments. This is a separate issue, and left
to decision makers and managers.

RESOLVING ISSUES

The Congress has in place a moratorium on leasing in submarine canyons
and in depths out to 400 m. This action was recognized at the outset as a
stopgap measure, and with evaluation of facts and deliberation, at least some
of the complex environmental issues may be resolved. The workshop organizers
are hoping for some level of consensus. Where this is not possible,

mechanisms such as minority reports are possible.

In closing, it is important to state that it is the aim of the workshop
to provide a forum where members may draw conclusions without undue bias or

pressure from MMS.

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PRE- AND POST-DRILLING BENCHMARKS AND MONITORING DATA
ON OCEAN FLOOR FAUNA, HABITATS, AND CONTAMINANT LOADS
IN THE GEORGES BANK SUBMARINE CANYONS

Dr. Richard A. Cooper
Professor of Marine Sciences
Director, National Undersea Research Center
University of Connecticut at Avery Point
Groton, CT

The biology and geology of 18 submarine canyons of the northwest Atlantic
was investigated by diver scientists, using manned submersibles, from 1973
through 1984. This effort entailed in-situ studies in 18 canyons ranging from
Corsair, Georges, Nygren, Powell, Lydonia, Gilbert, Oceanographer, Filebottom,
Hydrographer, and Veatch off Georges Bank to Atlantis, Block, Hudson, Toms,
Wilmington, Baltimore, Washington, and Norfolk off southern New England and
the Mid-Atlantic Bight. We concentrated on the canyons of Georges Bank and
those immediately to the southwest. The principal motivation was fisheries
assessment and habitat definition, including associated megabenthos. We were
concerned particularly with the canyon heads.

From 1980 through 1984 scientists from several New England research
institutions--National Marine Fisheries, U.S. Geological Survey, and National
Undersea Research Center--conducted a before-, during-, and post-drilling
study of the species abundance, community structure, animal-substrate
relationships, and body-substrate burdens of trace metals, polychlorinated
biphenyls (PCBs), and hydrocarbons within and downstream of oi] and gas
exploration areas on the south central portion of Georges Bank including
Lydonia, Oceanographer, and Veatch Canyons.

Ocean floor stations at specific sites (marked with a 37-kHz pinger) were
established in Lydonia Canyon (head of canyon and west wall) in 1980 and in
Oceanographer Canyon (head and west wall) and Veatch Canyon (west wall) in
1981 and 1982. Photo and video transects were made in July, along transects

oriented north, south, east, and west of the station marker. Estimates of
species abundance and community structure were made by habitat type. We also
collected surficial sediment samples, and animal samples (tilefish, scallops,
lobsters, and Jonah crabs) for tissue analysis.

We have classified the habitats of the canyon region as follows:

ws Type 1: Flat, featureless, with less than 5 percent overlay of rock
and gravel; accounts for approximately 60 percent of canyon heads.

= Type 2: Similar to Type 1, but with more than 5 percent overlay of
gravel and rock; about 10 percent of canyon head area.

ws Type 3: Boulder field, highly productive of fishery resources;
occupies about 5 percent of canyon head area.

ws Type 4: "Pueblo Village" environment; very important in fisheries;
accounts for some 20 percent of canyon head area.

ws Type 5: Sand dune and sand wave environment of the canyon axis;
occupies less than 5 percent of the canyon head area.

Canyons function as important nursery grounds for a wide variety of
megabenthic fauna such as shrimps, cancer crabs, lobsters, white hake, cusk,
ocean pout, conger eel, tilefish, black-bellied rosefish, etc. They provide
shelter that rarely occurs in noncanyon areas of the outer shelf and upper
slope for the adults of some 20 species. Our combined canyon studies show
that the surficial geologic features of the canyon heads support unique
ecosystems, largely because of their highly varied character.

We conclude that submarine canyons are complex three-dimensional
environments where there is little, if any, impact from active fishing gear;
they serve as refugia for many bottom-oriented species. Species diversity and
abundance are greater in canyons than in noncanyon areas at comparable depths.

Habitat diversity on a scale of a few meters to several kilometers leads to
species diversity.

Surficial sediments at each benchmark station were analyzed for trace
metals (barium, cadmium, copper, chromium, lead, mercury, and zinc),
hydrocarbons (aromatic and aliphatic), and PCBs. Scallops (muscle and
viscera), cancer crabs (hepatopancreas, claw/tail tissue, and eggs), and
tilefish (dorsal musculature) were subjected to the same analyses. Sediment
and animal-bound PCBs were below the levels of detection (0.005 ppm) prior to
drilling; subsequent analyses were not made (PCBs are not a component of
drilling muds and cuttings). Concentrations of petrogenic hydrocarbons (FI,
FII) were all undetectable before and after drilling. Trace metal
concentrations in the surficial sediments and in crabs and lobsters remained
relatively constant over time.

We did not find any effects from exploratory drilling. Since no impacts
were identified, this five-year data base is considered an appropriate
benchmark for future drilling operations.

Routine monitoring across habitat types from surface vessels appears to
be a waste of time. Examination of the benchmark data on annual variation in
species abundance, specifically for 14 designated key "indicator species,"
suggests that no one species is likely to reflect anything but a major impact
from production drilling. We suggest that community composition be examined
in a "site-specific" manner, that is, by habitat type and specific location,
in order to define faunal benchmarks for future oil and gas exploration.

THE LYDONIA CANYON EXPERIMENT:
CIRCULATION, HYDROGRAPHY, AND SEDIMENT TRANSPORT

Dr. Bradford Butman
U.S. Geological Survey
Branch of Atlantic Marine Geology
Woods Hole, MA

A field program (Butman 1988) was conducted to study the circulation and
sediment dynamics in Lydonia Canyon, located on the southern flank of Georges
Bank, and on the adjacent continental shelf and slope (Figure 2).

Its objectives were:

w to describe currents in Lydonia Canyon and the adjacent shelf and
slope, primarily in depths shallower than 1,500 m,

a to explore the role of canyons in transporting sediments onto or off
the shelf,

mw to see whether canyons are sinks for fine grain sediments, and

a to compare Lydonia Canyon and Oceanographer Canyon.

The program included (1) in-situ measurements by an array of moored
current meters, bottom tripods, and sediment traps maintained between November
1980 and 1982; (2) synoptic observations of the hydrography and suspended
sediments; (3) sidescan-sonar and high-resolution seismic
reflection surveys; (4) samples of the surficial sediments; and (5) direct
observations of the sea floor from the submersible Alvin.

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Figure 2. Georges Bank and currents. The principal canyons of Georges Bank
and the southern New England shelf. Bold arrows indicate net nontidal
circulation and the crossed two-headed arrows the major and minor axis of the
tidal currents. Two-headed arrow on the southern flank indicates orientation
of storm currents. Squares show locations of the eight exploratory wells
drilled on Georges Bank.

WATER CIRCULATION

The mean Eulerian current (that is, current measured at a fixed point)
was southwestward on the shelf adjacent to Lydonia Canyon and above the level
of the canyon rim at speeds of 5 to 10 cm/s. This southwestward flow parallel
to the isobaths is consistent with previous descriptions of the mean
circulation on Georges Bank.

On the continental slope, mean flow was strongly influenced by Gulf
Stream warm-core rings (Figure 3). Several rings passed to the south of
Lydonia Canyon during the observation period; the strong clockwise flow around
them caused eastward flow along the edge of the shelf as strong as 80 cm/s.
There is some evidence that the warm-core rings affect flow in the canyon by.
generating packets of high frequency current fluctuations. On the slope, the
influence of the rings in the water column extended to at least 250 m, but not
to 500 m. The influence of the rings did not extend onto the continental
shelf in water depths of 125 m.

Over the slope, there was a persistent off-shelf and down-slope component
of flow near the bottom of a few centimeters per second. Within the canyon,
the mean Eulerian flow near the bottom was complex (Figure 4). Near the head
of the canyon, at 300 m, net Eulerian flow 5 meters above bottom (mab) was
down-canyon at about 3 cm/s and was weak at 50 mab. At 550 m, the near-bottom
flow was up-canyon. At 600 m, the near-bottom flow was weakly up-canyon; the
flow at 100 mab was down-canyon. These observations suggest a convergence of
the mean Eulerian flow between 300 and 600 m and possibly several cells of
recirculation along the canyon axis. However, because of the energetic,
nonlinear, high-frequency motion observed in the canyon and the small spatial
scales, the mean Eulerian current may not indicate the actual Lagrangian
water-particle motion. Further analysis is required to determine the
Lagrangian circulation pattern.

Measurements made on the eastern rim of the canyon at about 200 m show
westward flow directly across the canyon axis. Measurements on the eastern

See vee

30 MARCH 1982

75°W 70°W 65°W 60°W

Figure 3. Gulf Stream rings. Position of the north wall of the Gulf Stream
and five warm core rings in late March 1982 based on satellite imagery. Ring
82A lies just to the south of Lydonia Canyon. When these rings are close to
the shelf break, the strong clockwise circulation around them causes eastward
flow along the outer edge of the shelf. In the absence of rings, currents
over the shelf and over the canyon are westward.

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Figure 4. Mean Eulerian current. Schematic map showing the general direction
of the mean Eulerian current near the bottom in the axis of Lydonia Canyon and
over the adjacent shelf and slope. Note that the net is down-canyon near the
head and up-canyon at about 450 m, suggesting a convergence toward the head.
Over the shelf and slope, circled dots indicate westward flow (out of the page
toward the reader) and circled x’s eastward flow (into the page away from the
reader). Over the outer edge of the shelf and slope, eastward flow is
associated with the presence of warm-core rings (see Figure 3).

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wall of the canyon, just a few kilometers away at comparable depths, show
northward inflow along the eastern wall. On the western wall, flow was
southward. The mean Eulerian currents in the canyon thus suggest a complex
vertical Eulerian circulation along the axis and horizontal exchange along the

canyon walls.

The current fluctuations with the canyon are aligned with the canyon
axis. The strength of the high-frequency fluctuations (motions with periods
shorter than about one day) increase toward the bottom and the head of the
canyon. The low-frequency currents (motions which fluctuate at periods longer
than about two days) were strongest over the slope and weakest in the canyon.
Along-shelf current fluctuations over the shelf were correlated with cross-
shelf flow over the canyon mouth (offshelf for southwestward flow), suggesting
enhanced cross-shelf exchange in the region of the canyon. Fluctuations at
semidiurnal periods dominate the current spectra. Near the canyon head, their
strength changes substantially with time, indicating random generation of
internal wave packets.

Similar studies in nearby Oceanographer Canyon show that currents there
are dominated by tidal currents and are stronger than in Lydonia Canyon. Net
Eulerian down-canyon flow was observed at both 200 and 600 m.

Kinetic energy spectra clearly show different current regimes on the
shelf and slope and in the canyon (Figure 5). With these spectra, the current
fluctuations can be conveniently separated using the periods at which they
oscillate into low-frequency flows (periods of more than 30 hr), tidal
currents (diurnal and semidiurnal), inertial fluctuations, and high-frequency
motions (periods of 2 to 10 hr).

On the shelf and slope, there is a large energy component at lower
frequencies (2 days or more) and the fluctuations are oriented along isobaths.
Low-frequency currents within the canyons are oriented along the axis and are
weak. At all stations, there was an energy peak correlated with semidiurnal
tides. In the canyons, the amplitude of the tidal, inertial, and high-

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* CROSS- SHELF
CROSS-CANYON

1076 10-5 1074

2.3x(cm/s)*

LCE (584) LCH (1375)
5 mab 5mab

(0) =
107 1i0°5 104 10-6 105 1074
FREQUENCY (Hz)

Figure 5. Kinetic energy spectra of near-bottom currents on the shelf
(station LCA) and slope (station LCI) adjacent to Lydonia Canyon (resolved
into alongshelf and cross-shelf) and along the canyon axis (stations LCB, LCE,
and LCH, resolved into along-canyon and cross-canyon currents).

frequency motions varied along the canyon axis (Figure 6). There was a clear
increase in high-frequency (2 to 10 hr) motions toward the canyon head. The
Lydonia Canyon region is one of the few areas of the shelf where all
frequencies are important in describing the system.

SEDIMENT TRANSPORT

Distribution of surficial sediments and high-resolution seismic
reflection data suggests that very fine sand and silts and clays accumulate in
the head of Lydonia Canyon and on areas of the adjacent shelf. There is
little silt-plus-clay on the crest of the bank where currents are strong, but
as much as 75 percent of the total sediment is located on the slope where
currents are weaker (Figure 6). The data suggest a depositional environment
surrounding the canyon head.

Silt-plus-clay content in the surficial sediments generally increased
with depth along the canyon axis (Figure 6). This overall trend was
interrupted at 300 to 400 m, where there is 30 to 40 percent silt-plus-clay.
At 500 m, sediments get coarser. Finally, farther down the canyon, sediments
get finer again. These distributions mirror current strengths: coarse
sediments where currents are strong, fine sediments where they are weaker.
However, current, sediment trap, and beam attenuation measurements show that
surficial sediments are reworked and suspended along the canyon axis to a
water depth of at least 600 m. Thus, although the texture suggests that fine
sediments may be accumulating, the axis is not tranquil at depths less than
600 m.

The Georges Bank canyons are complex topographically, with steep walls
that are vertical in places. One must consider not only sediment types on the
canyon floor but also on the walls, which change in character from the deeper
to the shallower parts.

Near-bottom current measurements on the slope from Baltimore Canyon to
Georges Bank (Csanady et al. 1988) show that, below 500-m water depth

Ri ia

NEAR BOTTOM ENERGY

(876)
——— HIGH FREQUENCY

\

\ a \ — — SEMIDIURNAL
\ y ae sacar’ INERTIAL

\ < \ —— DIURNAL

\

\ / \ —:— LOW FREQUENCY
\ / \
\

ENERGY (cm®/sec?)

DEPTH (m) 100 141 295 560 600 1275
STATION LCA LCU LCB LCS LCE LCH

Figure 6. Spatial distribution of energy in the near-bottom currents along
the axis of Lydonia Canyon. The amount of energy in five frequency bands
(high frequency, semidiurnal, inertial, diurnal, and low frequency) changes
along the canyon axis, presumably as a result of changes in the density field,
bottom slope, and incident energy.

oe ene

(depositional environment), currents exceed 20 cm/s only about 5 percent of
the time, and are less than 5 cm/s 40 percent of the time (Figure 7). On the
slope, the 300- to 500-m isobaths are an approximate transition zone between
an erosional and a depositional environment. In Lydonia Canyon and
Oceanographer Canyon, the currents at 300 and 500 m exceeded 20 cm/s at least
30 percent of the time. For these canyons, at the depths observed, currents
are much stronger than on the adjacent slope. Profiles of beam attenuation
compared sediment concentrations in the canyon and the adjacent shelf and
slope. In the canyons, suspended sediments were always greater than on the
slope at comparable depth. Suspended sediments increased near the bottom,
especially near the canyon head, presumably due to bottom resuspension.

LYDONIA AND OCEANOGRAPHER CANYONS COMPARED

Both Lydonia Canyon and Oceanographer Canyon are complex environments
where there are rapid changes (over a few hours) in suspended sediment
concentration, temperature, current velocity, and direction. The two canyons
differ in sediment texture, current strength, and direction of net flow. In
Oceanographer Canyon a net down-canyon flow was observed at 300 and 600 m.
Above about 500 m in Lydonia Canyon, currents exceed 20 cm/s 20 to 30 percent
of the time; in Oceanographer Canyon, they exceed this rate 40 to 60 percent
of the time (Figures 8 and 9). Based on the coarse-grained sediments and
stronger currents, the head of Oceanographer Canyon is primarily erosional,
whereas Lydonia Canyon has areas both of erosion and deposition. Both canyons
are much more energetic than the adjacent slope. Though the erosional/
depositional classification of canyons is important in analyzing the
hypotheses of this workshop, it is important to recognize that this
Classification is an extreme simplification.

om ye

PERCENT OF TIME

80 SPEEDS GREATER THAN 20 cm/s
Open Slope ——

a a Oceanographer @
S 60 Lydonia ®
uJ

S

oO

3}

ed

a

O

a

lJ

a

0) 1000 2000 3000
BOTTOM DEPTH (m)

Figure 7. Percent current exceeds 20 cm/s. The percentage of time during
which the near-bottom currents exceed 20 cm/sec in Lydonia and Oceanographer
Canyon and over the adjacent slope. The currents are much stronger in these
two major canyons at water depths less than 500 m than at comparable depths on

the slope, suggesting a more erosional environment (adapted from Csanady et
al. 1988).

2 1o:2

SEDIMENT TEXTURE
%e SILT & CLAY

68°30 68°20! 68°10" 68°00' 67°50' 67°40’ 67°30' 67°20" 67°10'

Figure 8. Percent fine sediments (silt-plus-clay) in the surficial sediments
on the shelf and slope adjacent to Lydonia and Oceanographer Canyons. Symbols
indicate location of samples from various field experiments. Texture within
the canyons not contoured. Note the increase in fine-grained sediments in
lobes to the east and west of Lydonia.

= 194

AXIS OF LYDONIA CANYON
Pac SEDIMENT TEXTURE
LB3i2 ZY LCH

are 1 | m4 ‘Z Yy

GRAVEL
Ewes

100

PERCENT
on
ro)

=
= Uff y
E cook SAMPLE DEPTH “Mii ”
3 Z
0 5 Uf
\500 aM “Wy
“Uf

Figure 9. Surficial sediment texture along the axis of Lydonia Canyon.
Percentages of fine (silt-plus-clay), medium (sand), and coarse-grained
(gravel) sediments along the axis of Lydonia canyon and the adjacent shelf
(upper panel). The lower panel shows the depths of the samples. Note the
increased fines near the head of Lydonia Canyon (station LCB) and the coarser
sediments near LCE where the currents are slightly stronger. The fine
sediments near the head are where Bothner measured accumulation rates of about
50 cm/1,000 yr. The mean Eulerian current measurements suggest a convergence
of the flow toward the head.

25902

QUESTIONS

Teal asked why Oceanographer and Lydonia Canyons are so different.
Butman responded that the current strength in the canyon depends on geometry
(wall slope and bottom slope) and the density structure in the water column.
These parameters control the propagation and intensification of energy near
the bottom. In some canyons, the bottom slope and water density may intensify
currents toward the canyon head. In other cases energy will be reflected back
out of the canyon. In Oceanographer Canyon and Lydonia Canyon there appears
to be a difference. It is a complex oceanographic problem, and there has been
little attempt to model the propagation of energy through the canyon using
realistic topography and density.

Boehm asked why silt gets deposited around the canyon head on the shelf.
Butman responded that he didn’t know. The thickness of the silt-plus-clay
near the canyon head is relatively thin.

Teal asked whether there were any severe events during the study. Butman
answered no and that, for the two year observational period, any two-to-four
months were representative of the remaining months. There was very little
variability in low frequency energy fluctuations but a large change in the
high frequencies. There was some correlation between the occurrence of warm-
core rings at the canyon mouth and the strength of the current fluctuations at
the canyon head. Flow in the canyon was generally not correlated with flow on
the shelf.

Kraeuter asked where the sediments were coming from. Butman responded
that they apparently come from the shelf. Some sediments from the middle part
of the canyon may be transported toward the head. This is a rate problem.
However, the present study has been process-oriented and does not specifically
address rates, though rates are important to the hypotheses in question.

sa sa

REFERENCES

Butman, B. North Atlantic slope and canyon study. U.S. Geological Survey
Open File Reports 88-27A and 88-27B. 1988; 1:65 p. 2:563 p.

Csanady, G. T.; Churchill, J. H.; Butman, B. Near-bottom currents over the

continental slope in the mid-Atlantic bight. Continental Shelf Research.
8:653-671; 1988.

eae

SEDIMENTARY ENVIRONMENTS IN SUBMARINE CANYONS AND
ON THE OUTER SHELF - UPPER SLOPE OF GEORGES BANK

Dr. Page C. Valentine
U.S. Geological Survey
Woods Hole, MA

Sedimentary environments have been identified on the southern margin of
Georges Bank in the depth range of 150 to 600 m on the basis of sedimentary
texture, bedforms, and direct current measurements. Dominantly erosional vs.
depositional environments are identified for the outer shelf, upper slope, and
submarine canyons along the southern margin of Georges Bank. Studies
conducted in Oceanographer, Lydonia, and other canyons suggest that it is
possible to predict sedimentary environments in unstudied canyons based on
overall canyon morphology and by analogy with the known distribution patterns
of canyon sedimentary environments.

SHELF ENVIRONMENT

Georges Bank is an isolated shoal, separated from continental sediment
sources by the Northeast Channel, Great South Channel, and the Gulf of Maine.
The mean regional flow field is clockwise around Georges Bank. The bank
surface is erosional; fine sediments winnowed from the bank top are delivered
to bank-edge environments. Coarse sands and gravels found near-bottom current
maxima on the bank grade to finer sands and mud along the southern margin.

At the shelf edge, rippled sand gives way to smoother and finer-grained
sand deposits as water depth increases on the upper slope. Submarine canyons
of varying size and wall steepness incise the Georges Bank shelf and contain
such sedimentary facies as pavements of ice-rafted gravel, bioeroded and
collapsed Pleistocene silt outcrops, mobile sands, and almost featureless
silty sands.

2523 2

SLOPE ENVIRONMENT

The upper slope east of Oceanographer Canyon, to a depth of 200 m
demonstrates normal downslope textural gradients related to bottom current
energies. By contrast, the upper slope between depths of 200 to 300 m is
erosional in nature with little silt or clay present. Below 300 m, silt and
clay content increases steadily downslope to the heads of small gullies found
at 500 m. The interval below 300 m is depositional and includes the floors of
small slope canyons such as Filebottom Canyon, which is covered with silty
sand. The lack of deposition in the 200- to 300-m interval is attributed to
strong, northeastward-flowing bottom currents of Gulf Stream warm-core rings
that intersect the upper slope environment. Nineteen warm-core rings impinged
on the Georges Bank margin in the Oceanographer-Lydonia Canyon region between
1976 and 1983. The upper slope was influenced by the clockwise flow of these
eddies for a total of 17 months during this 8-year period. Current velocities
of 50 to 60 cm/s (about 1 kt) effectively removed most fine sediment during
this interval.

CANYON ENVIRONMENTS

Sedimentary facies related to bottom currents were investigated in and
around several canyons on the southern margin of Georges Bank. These facies
are related to the overall morphology and energetics of the two canyons and
the sediment sources. The most extensive observations have been made in
Oceanographer and Lydonia Canyons. Gravel deposits and mobile sands are found
along the eastern rims of both canyons, and they are best developed along the
northeastern side of Oceanographer Canyon. A strong bottom current of unknown
origin flows westward at about 50 cm/s across the rims of both canyons at
depths of 150 to 200 m, transporting shelf sand across deposits of ice-rafted
gravel onto the east canyon walls.

Oceanographer Canyon walls are steep in places, with extensive bioeroded

outcrops of Pleistocene silt. Sediment that is spilled over the canyon rim
combines with silt eroded from the canyon walls and is transported downslope

ny ae

to the canyon floor. The floor is covered by coarse sands which are mobilized
into both large and small asymmetric bedforms. Ripples, megaripples, and sand
waves are present in the axial area down to at least 750 m. Analysis of
bedform shape indicates that sand is moved both up and down the canyon axis
with no net transport direction for sand. Silt and clay is winnowed by the
strong currents. Maximum current velocities measured in the axial area of
Oceanographer Canyon range between 75 and 100 cm/s. The floor of
Oceanographer Canyon is predominantly nondepositional with regard to fine
sediments.

The depositional facies of Lydonia Canyon are more complex but generally
contain silt and clay deposits both on the canyon walls and in the axial area.
Current velocities within this canyon are reduced relative to Oceanographer
Canyon.

Small, shallow canyons such as Heeltapper are relatively tranquil, and
like the upper slope, canyon floors are covered by silting sand.

CANYON MORPHOLOGY, CURRENTS, AND SEDIMENT TRANSPORT

The outer continental shelf and slope areas adjacent to and including
Oceanographer and Lydonia Canyons can be characterized in terms of sediment
transport and current strength. Areas of high sediment transport include the
eastern rims of both canyons and the axis of Oceanographer Canyon down to 750
m. Areas of moderate sediment transport include the walls of both canyons
and the mud-free interval of the upper slope swept by warm-core rings. Areas
of low net sediment transport include most of the head and axis of Lydonia
Canyon, the small canyons, and the continental slope below 300 m.

The data from the southern slope of Georges Bank suggests that the
energetics of bottom currents found within the canyons are directly related to
the overall canyon morphology. Large, long canyons with deep mouths at the
shelf break (the 200-m isobath) and steep walls interact with the tidal flow
regime to strengthen the bidirectional currents within the axial area.

= 325) =

Moderate size canyons with shallower mouths and less steep walls have weaker
bidirectional flows. Small shallow canyons and gullies are low energy
depositional environments. Because sediment transport and bottom facies are
generally well-correlated with current energy, the results from studies of
Lydonia, Oceanographer, and other canyons can be used to predict bottom
facies, sediment transport regimes, and depositional vs. erosional areas for
other canyons on the southern margin of Georges Bank (Table 1). High energy
canyons include Oceanographer, Hydrographer, and Gilbert. Moderate energy
canyons are Lydonia, Powell, Welker, and Veatch. Low energy canyons include
Atlantis and Heeltapper.

In general, sediment movement is more rapid in a narrow band along the
upper slope, along the lower walls and floors of large, high-energy canyons,
and from the shelf westward across the eastern rims of large and medium
canyons. Sediment movement is less rapid on the outer shelf, on most of the
upper slope, including the gullies, on the floors of medium and small canyons,
and on the shelf around some canyon heads. A moderately energetic canyon of
medium size such as Lydonia may be accumulating sediment most rapidly. The
movement and resuspension of fine-grained sediment on the floor of Lydonia
Canyon is substantial. However, the canyon traps a large volume of shelf sand
as well as bioeroded silt from outcrops on lower canyon walls, and sediment is
accumulating on its floor.

2.06 <

Table 1. Sedimentary facies and sediment transport regimes for rims, walls,
and floors of high, moderate, and low energy canyons along the Outer
Continental Shelf of Georges Bank. LGH = canyon length landward
from the canyon mouth at the shelf break (200-m isobath); DPH =
depth from canyon rim to floor at the canyon mouth; ANGL = slope
angle of lower canyon walls at the canyon mouth.

HIGH EWERGY CANYONS: LGH: 13-25 KM DPH: 750-1000 M NGL: 15-359
RIM: SHELF SAND+GRAVEL, RIPPLED-----SAMD IN TRANSIT TO WALLS-------- TIDAL CURRENTS,
GRAVEL [EAST RIM] -------------- STATIONARY WESTWARD CURRENT
VERY FINE SAND@---------------- DEPOSITED AT CANYON HEAD (FROM CANYON?)
WALLS: MANY SILT+CLAY OUTCROPS-------- EXTENSIVE BIOEROSION
MIXED SHELF SAND AND----~------- IN TRANSIT TO FLOOR------------- AXIAL(?) CURRENTS
SILT+CLAY, RIPPLED
FLOOR: SAND, RIPPLED, ----------------- TRANSPORTED UP-DOWN CANYON------ STRONG SEMI-DIURNAL
MANY LARGE BEDFORMS FINES SEPARATED; SAND DEPOSITED AXIAL CURRENTS
MODERATE ENERGY CANYONS: LGH: 8-18 KM DPH: 320-520 4 ANGL: 8-15°
RIM: SHELF SAND+GRAVEL, RIPPLED-----SAND IN TRANSIT TO WALLS-------- TIDAL CURRENTS.
GRAVEL [EAST RIM]-------------- STATIONARY WESTWARD CURRENT
VERY FINE SAND=<-<<<<<<<<<<<=<- DEPOSITED AT CANYON HEAD (FROM CANYON?)
WALLS: SILT+CLAY OUTCROPS---<---------- MUDERAYTE 3IOEROSION
MIXED SHELF SAND AND-~---------- IN TRANSIT TO FLOOR------------- AXLAL(?) CURRENTS
SILT+CLAY, RIPPLED
FLOOR: SILTY SAND, RIPPLED,----------- TRANSPORTED UP-DOWN CANYON------ MODERATE SEMI-DIURNAL
FEW LARGE BEDFORMS FINES RE-SUSPENDED ; AXLAL CURRENTS

SAND, SILT, CLAY DEPOSITED

LOW ENERGY CANYONS: LGH: 2.5-5 KM DP: 200-300 4 ANGL: 4-7°
RIM: SHELF SAND+GRAVEL, RIPPLED----- SAND IN TRANSIT TO WALLS TIDAL, WCR(?) CURRENTS
7GRAVEL [EAST RIM) IF CANYON INCISES SHELF 2 ty Se ?7WESTWARD CURRENT
WALLS: FEW SILT+CLAY OUTCROPS--------- MINOR BIOEROSION
MIXED SHELF SAND AND----------- IN TRANSIT TO FLOOR--~---------- AXIAL(?), WCR(?) CURRENTS

SILT+CLAY, FEW RIPPLES

FLOOR: SILTY SAND, FEW RIPPLES, ------- SAND, SILT, CLAY DEPOSITED------ WEAK SEMI-DIURNAL
NO LARGE BEDFORMS AXIAL CURRENTS

REFERENCES

Valentine, P. C.; Uzmann, J. R.; Cooper, R. A. Geology and biology of
Oceanographer Submarine Canyon. Marine Geology. 38:283-312; 1980.

Valentine, P. C.; Cooper, R. A.; Uzmann, J. R. Submarine sand dunes and
sedimentary environments in Oceanographer Canyon. Journal of Sedimentary
Petrology. 54:704-715; 1984.

Valentine, P. C.; Uzmann, J. R.; Cooper, R. A. Submarine topography,
surficial geology, and fauna of Oceanographer Canyon, northern part.
U.S. Geological Survey Miscellaneous Field Studies Map MF 1531. 5
sheets, scale 1:10,000; 1984.

Valentine, P. C. The shelf-slope transition--canyon and upper slope
sedimentary processes on the southern margin of Georges Bank. U.S.
Geological Survey Bulletin 1782. 1987; 29 p.

Valentine, P. G., and Uzmann, J. R. Submarine topography of Corsair Canyon,

northern part. U.S. Geological Survey Open-File Report 88-675. 2
sheets, scale 1:6000; 1988.

a): ar

TOMS CANYON STUDY

Dr. Robert C. Ayers, Jr.
Exxon Production Research Co.
Houston, TX

Exploratory drilling activity on the Middle Atlantic OCS was at its peak
during the years 1978 to 1981. Environmental concern about potential adverse
impact prompted Government-mandated studies, including one at Toms Canyon.
The wellsite, in Block 816, is at the edge of the continental shelf about
150 km from the New Jersey Coast and about 3.7 km northeast (up current) from
Toms Canyon. The Government required the lessee, Exxon USA, to perform a
monitoring study to determine if discharges from the well were entering the
canyon in harmful quantities. The study was carried out by EG&G under the
direction of Exxon Production Research Company.

The field study, from September 1980 to April 1981, included a pre-
drilling survey, four cruises during the drilling period, and continuous
monitoring of currents and sedimentation at several locations from the
drilling rig to midcanyon. The pre-drilling survey included bathymetry;
sediment sampling for background measurements of barium, chromium and
vanadium; and grain size analysis and sampling of biota. The bilogical
samples were to be analyzed only if Exxon drilled another well in Block 816 or
in any other block adjacent to Toms Canyon. Since no other wells were
drilled, the biological samples were never analyzed.

The sampling design included three transects, one running southwest and
downcurrent from the rig site across the canyon, one along the canyon axis,
and one north-south across the shelf break through the rig site. Bottom
samples were taken and water properties were measured throughout the water
column. Sediment traps and current meters were located near the bottom, and
in the upper water column near the rig, at the canyon rim and at mid-canyon.

29) =

RESULTS

Currents on the shelf were in line with other studies: mean flow
southwest along the isobaths at 10 to 21 cm/s and relatively uniform flow
throughout the water column. In the canyon, the currents were decoupled from
the shelf flow, running up and down the axis with a net up-canyon movement.

Sediment analysis showed up to 95 percent sand on the shelf, 50 percent
at about 350 m, and around 3 percent at 550 m in midcanyon. The silt/clay
ratio in most of the samples was about 2. Pre-drilling metals analysis for
the upper 3 cm of sediment showed background levels consistent with earlier
studies--barium at 156 to 303 ppm, chromium at 8 to 45 ppm and vanadium at 16
to 49 ppm. The higher levels were found in the canyon, reflecting the higher
concentration of fine sediments. During drilling, the barium levels in the
upper 3 cm of sediment were elevated to almost 5,000 ppm in the immediate
vicinity of the wellsite, but were down to background levels within 1 to
1.5 km downcurrent. Chromium and vanadium levels were not elevated above
background even at the wellsite.

The sedimentation rates, as measured by the traps ranged from 32 to
347 mg/m?/day near the sea surface (20-m depth), 98 to 800 mg/m*/day at
middepth (140-m depth), and 121 to 5,792 mg/m*/day in the canyon axis at 540-m
water depth, with one anomalously high value over 1.1 million mg/m*/day at
this location. Barium levels in the sediment traps were elevated above
sediment background with higher values occurring in the traps near the
wellsite. However, the percentage of mud solids in the sediment traps ranged
from about 10 percent at the 20-m depth and 1,500 m from the wellsite, to less
than 0.1 percent in the canyon--at the 540-m depth and 7 km from the wellsite.

CONCLUSIONS
= Mud solids were transported to the canyon but not in sufficient

quantity to affect the natural sedimentation rate or be detected in
canyon sediments.

2 302

= Barium levels were elevated in the sediments up to 1.5 km from the
wellsite. Chromium and vanadium sediment concentration’s were not

elevated, even at the wellsite.

a Sediments in the canyon are less sandy and more variable in
composition than those on the shelf.

COMMENT

Bothner observed that the anomalously high rate of sediment collection in
traps from the canyon axis may have been real as it is only about seven times
those measured in the axis of Lydonia Canyon. The rate of sediment collection
in traps 5 mab in Lydonia Canyon were 10 times higher during periods of strong

currents than during quiescent periods.

oo 4 ee

RECENT DEVELOPMENTS IN INDUSTRY SPONSORED RESEARCH

Dr. James P. Ray
Shell 0i1 Company
Houston, TX

Preliminary results were shown from three studies, which have not yet
been completed, in the vicinity of drilling operations off the coasts of
California, Texas, and Alabama. The California and Alabama studies were done
at single well sites. The Texas study was in a field of six development and
four exploratory wells.

The California field study took place in 1984 at Molino, about halfway
between Santa Barbara and Pt. Conception, about 3 mi offshore in a water depth
of 73 m. The 11,000-ft well used 10,700 bbl of drilling mud containing 860
metric tons of barite.

The results are consistent with earlier studies in a number of ways; for
example, plots of barium distribution in the sediments are directly related to
currents in the water column. Concentrations decrease rapidly with distance
away from the platform. Also, although total barium in the drilling mud
ranged up to 350,000 ppm, the soluble quantities obtained by a weak acid leach
technique were about two orders of magnitude lower--around 400 to 500 ppm.
Background levels of barium in near shore areas along the California coast
range from 700 to 900 ppm.

Other metals--zinc, lead, copper, and cadmium--follow the barium pattern.
Mercury, nickel and chromium show slight increases with distance, but that is
not thought to be related to drilling.

Biological studies were done on three species of bottom organisms--
Cyclocardia, a siphon-feeding clam, and Pectinaria and Nephtys, two deposit-
feeding polychaetes--to find out if the metals bioaccumulate, and where in the
organism the metals are located. It turned out that more than 97 percent was

ap Be

in the granular pellets, the insoluble fraction, which is most probably
excreted. Based on this information, the investigators hypothesize that
almost all of the barium taken up is in the insoluble, barium sulphate form.
Very little was found in the soluble fraction.

TEXAS

The Texas wellsite, examined in 1986 and 1987, is about 12 mi offshore
from San Antonio Bay, in about 25-m water depth. Nearly 17,000 metric tons of
barite were in the discharged drilling muds. A problem in this (and other
areas) is that there are often multiple discharge points within a development
field so that distributions are complicated. Some of the results showed very
jumbled patterns of distribution; nevertheless, it is clear that maximum
concentrations of metals were highest near the wells (closer than 200 m) and
decreased rapidly with distance. Barium was the only element that was
traceable beyond the first few hundred meters. Biological effects
attributable to bottom contamination were not detectable.

Core samples in these shallow waters were taken by hand, by divers, for
both fine fraction and bulk sediment analyses. The cores show bioturbation
ranging up to 10-cm depth.

ALABAMA

Studies were done during 1987 and 1988 about 5 mi off the mouth of Mobile
Bay, in water depth of 12 m. (Incidentally, this location is only a few miles
from the area where the Army Corps of Engineers dumps in a day 6 to 7 times as
much dredge spoils as the amount of material the drill rig discharges in its
active life--about 8 to 12 months of drilling). Here the sampling was done in
a ring pattern at varying distances from an exploratory well on four
occasions: before drilling, shortly after drilling began, right after drilling
stopped, and 8 to 9 months later. Again, both fine and bulk analyses were
done.

=~ "33 -

The usual pattern in the bulk sediment results was a sharp increase after
the commencement of drilling and a return to background or near background
levels at the end of 9 months. There was little discernible change over time
in the fine fractions. There appeared to be a lack of correlation between

mercury and barium.

CONCLUSIONS

There is little, if any, evidence of biological effects in these three
locations. Measurements of total metals in organisms can be misleading.
Detailed analysis of the actual fate of metals within the organism are needed
to more accurately determine biological impact.

QUESTIONS

Teal and Butman asked about the lack of mercury/barium correlation. The
speaker noted that there is some evidence of a cadmium-barium correlation in
tests off California but that it only appears at the stations immediately
downstream, at distances less than or equal to 400 m. The regulatory agencies
are interested in mercury and cadmium although mercury remains insoluble and
is not bioavailable. Cadmium is slightly soluble and has shown some limited
availability for uptake by organisms.

Cooper asked about effects on marine life. Ray saw no biological effects
beyond the immediate wellsite. In intracellular analysis of animal tissue,
the barium concentrations in the cytosol (soluble fraction) is one to two
orders of magnitude below the threshold levels of calcium (Ca++), and thus
probably would cause no toxic effects.

He re-emphasized the need to look at detail: the fine fraction in the

sediments and the different parts of the organism--in order to come to any

meaningful conclusions.

- 34 -

Bothner asked about the relative importance of dissolution of barium and
transport in mass balance studies. Ray responded that results to date don’t
add up: there’s not as much barium in marine sediments as one might predict.
Mass balance studies on the shelf predict higher levels of barium than are

actually present.

Note: The studies reviewed will be completed and available by the end of the
first quarter, 1989. The California study was conducted by Jenkins et al.,
California State--Long Beach; the API--Texas and the Mobile Bay--Alabama
Studies were by Continental Shelf Associates, A. Hart, B. Vittor, et al.
Because the studies reviewed were in draft final form, the data tables
presented for discussion could not be reprinted in this report.

be

THE FLUX AND COMPOSITION OF RESUSPENDED SEDIMENT IN LYDONIA
CANYON: IMPLICATIONS FOR POLLUTANT SCAVENGING

Dr. Michael H. Bothner
U. S. Geological Survey
Woods Hole, MA

One of the objectives of the U.S. Geological Survey’s sediment
geochemistry studies in Lydonia Canyon and on the adjacent continental shelf
and slope was to determine the relative potential for sediments to accumulate
contaminants. The analyses of bottom and suspended sediments have provided
four lines of evidence that suggest that the axis of Lydonia Canyon has a
higher potential for contaminant accumulation than the surrounding areas do.

The evidence supporting this conclusion includes the following:

ws The head and axes of Lydonia (and Oceanographer) Canyon has much
higher fluxes of resuspended sediment than the adjacent shelf or
slope. This resuspension activity provides more opportunity for
particles to adsorb dissolved contaminants from seawater.

ws The head of Lydonia Canyon is an area of active sediment accumulation.
(This is based on carbon-14 dating of piston cores.) Therefore, some
of the sediment that is recycled into the water column by resuspension
is eventually buried in the bottom sediments by subsequent deposition.

mw Enhanced scavenging of dissolved contaminants is suggested by the
inventories of sediment-reactive isotopes lead-210 and plutonium-239,
-240, which are higher in the sediments of the axis of Lydonia Canyon
than in sediment from areas of comparable depth on the continental
slope.

«436 -

m Although trace-metal levels are low in the surface sediments along the
Outer Continental Shelf and slope, the concentrations of cadmium,
chromium, copper, and lead--normalized for differences in grain size--
are higher in the canyon axis than in adjacent areas.

SEDIMENT RESUSPENSION

It is commonly reported in the literature that fine-grained sediments
provide active surfaces which can adsorb many dissolved inorganic and organic
contaminants in sea water. Resuspension of bottom sediments is one important
mechanism through which the opportunity for such adsorption reactions by
particulates can take place.

On each of the five current-meter deployments in and around Lydonia
Canyon, discussed in a previous talk by Butman, we fixed sediment traps at
various heights above the bottom in order to determine the RELATIVE intensity
of sediment resuspension in different areas and heights above bottom.

We claim only to measure the relative intensity of resuspension, because
the absolute efficiency of these sediment traps is unknown in a current flow
that is both strong and highly variable. However, all the results have been
normalized to a trap of standard dimensions and so a comparison of the
collection rates for different areas is possible (Bothner and others 1986).

Figure 10 summarizes the differences in the flux of trapped sediment
collected in Lydonia Canyon during the first experiment (12/1/80 to 4/29/81)
when areal coverage was the most extensive.

The rate of sediment collection (g/m*/day) increases greatly (almost
logarithmically) as the distance above the bottom decreases. This indicates

that resuspended bottom sediment is the source of the material collected.

The highest collection rates are observed near the bottom in the canyon
axis at locations in 300- and 600-m water depth. There, the rates are as much

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faqs 5 mab

Y= 20-26 mab
WB- so mab

Eg- 100 mab

[_]= 300 mab

Figure 10. Histograms showing the flux of resuspended sediment (g/m?/day) at

different heights (in meters) above the bottom.

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as 65 times higher than rates on the continental slope at comparable depth and
seven times higher than those measured on the continental shelf.

The frequency of sediment resuspension and its variability in intensity
were also indicated in the sediment-trap data. An instrument was placed in
some of the traps which deposited a layer of white teflon powder on the
accumulating sediment at 10 day intervals (Figure 11). The mass of sediment
collected between each time interval varied by an order of magnitude. The
variability in flux of trapped sediment correlated, in most cases, with high-
energy current events recorded by the current meters. It is during these
events that the coarsest sediment was resuspended and collected in the
sediment traps.

Not only is the resuspended sediment flux relatively intense and frequent
in the canyon axis, but it also influences a significant portion of the water
column. Traps placed between 20 and 102 mab exhibited a similar pattern of
alternating fine and coarse sediment, indicating that resuspended sediments
were being exposed to at least the lower 100 m of the water column.

These same processes of sediment resuspension seem to be intensified in
the axis of Oceanographer Canyon as well. During one deployment, the flux of
trapped material was 30 percent higher in Oceanographer Canyon than in Lydonia
Canyon at the same water depth.

RATES OF SEDIMENT ACCUMULATION AND SEDIMENT SOURCES

There is a growing body of information which suggests that the head of
Lydonia Canyon is accumulating sediments and that the continental shelf
contributes at least some of this material. On the basis of high-resolution,
seismic-reflection and sidescan-sonar data, Twichell (1983) mapped areas of
post-glacial sediment fill and suggested that accumulation of fine sediments
winnowed from the adjacent shelf was probably active. The carbon-14 age of
total organic carbon deposited with these sediments was determined on two

2 30

Figure ll.

A. Histogram showing the relative (%) mass of sediment collected at
station LCP, 5 mab, during each 10 day interval between September 28,
1981 and January 28, 1982.

B. Schematic diagram showing position of teflon timing layers (open
symbols) and layers of coarser sediment (dots). Percent sand is
indicated below schematic.

C. X radiograph of the sediment trap sample showing layers of coarser
(darker) and fine sediment. Top of sample is to the left.

D. Record of bottom stress (dynes per cm?) at the station LCP.
E. Calculated flux of trapped sediment. The size distribution (%) of

particles 8, 32-63, and 64-125 wm in diameter is indicated for periods
of increased flux (Bothner and others 1987a).

2 -40r=

% TOTAL WEIGHT COLLECTED

OVER 10 DAY INTERVALS
ro)

4/24!

43 67 2. «4 49 205i 8H 34
% TOTAL SAND FOR SAMPLED SECTION INDICATED BELOW SCHEMATIC

LCP aii 3(2371)

4) Current Stress (low—passed)

i)
3
g 2
1
0
26 6 16 26 S 15 25 5 1S 25 4 14 24
ay OcT NOV OEC JAN

1982

LCP Il Trap 316

350) Settling Flux PREDICTED SIZE DISTRIBUTION OF FLUX

8

on &
~250 ate!
g
200
=
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& 50
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26 16 26 5 15 25 1S 25 4 14 24
SEP OCT NOV OEC JAN

1981 1982

Figure ll.

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DYN/CMee2

rT
Oo
FLUX (gm/m'*/day)

piston cores collected from the head of Lydonia; the data show a near-linear
increase of age with depth, which suggests a constant and ongoing accumulation
of sediments at these locations over the last few thousand years (Figure 12).
The mean accumulation rate is 60 cm/1,000 yr or about 2 g/m*/day.

The carbon-14 age of the surface sediments is about 900 years, which
reflects the slow exchange of atmospheric and oceanic carbon dioxide and
bioturbation of the surface sediments.

The calculated rate of sediment accumulation from piston cores is at
least an order of magnitude less that the rate of sediment accumulation in
traps. Although the efficiency of the traps is not known, this implies that
canyon sediments are subjected to numerous cycles of resuspension and
deposition before final burial. These cycles are thought to increase the
opportunity for scavenging of dissolved contaminants by particles.

The rates of sediment accumulation have not been determined on the open
slope adjacent to Lydonia Canyon. The closest carbon-14-dated core on the
slope was taken south of Martha’s Vineyard in 1,100 m of water, where a rate
of 13 cm/1,000 yr was reported (Anderson and others 1988). The rates of
sediment accumulation on Georges Bank are assumed to be nil. Redistribution
of materials is occurring, but because of its present isolation from
continental sources of sediment, the Bank as a whole is considered erosional.

Transport of material from the continental shelf into the axis of Lydonia
Canyon is directly evidenced by the systematic increase with time in the
concentration of barium in sediment trap samples (Figure 13). The first
mooring deployment predated the exploratory drilling on Georges Bank and the
remaining four deployments included the period when eight wells were drilled,
the closest about 9 km away from mooring LCB.

The barite component of drilling mud, the source of this barium increase,

was highly diluted by the time it was collected in Lydonia Canyon. It was
measurable only in the fine fraction (finer than 60 microns) of the trapped

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THOUSANDS OF YEARS BEFORE PRESENT
6

200

SEDIMENT DEPTH (CM)

300

400

A= Grab 0C122-46, A= Grab 0C124-7A, (= piston core 0C122-43,
O= piston core 0C122-45. Linear regressions indicate accumulation

rates of 51 cm/1000 years for 0C122-45 and 69 cm/1000 years for
0C122-43.

Figure 12. Carbon-14 age of organic carbon in marine sediments from the head
of Lydonia.

Bey cae

400

300

200

Ba, IN PPM

100

Figure 13. Concentration of barium in the fine fraction of material collected
in sediment traps deployed at the head of Lydonia Canyon on different
deployment dates. Traps were recovered just prior to the next deployment.

= 4hr=

sediment, where barium concentrations increased only about 35 percent above
pre-drilling levels; maximum concentrations were 380 ppm. Near the drilling
rig in Block 410, the barium concentrations in the fine fraction of bottom
sediments reached 10,000 ppm in post-drilling samples.

TRACE METALS AND RADIONUCLIDES

Twelve metals were measured in bottom sediments at 15 stations on the
continental slope off Georges Bank, and all were found at levels expected for
uncontaminated fine grained sediment (Bothner and others 1987b). Lead was the
only metal showing slight enrichment in the surface sediments within the
cores, compared to deeper sediments. This trend is seen in many off-shore
areas and is thought to reflect the use of lead in gasoline and industry.

The metal concentrations in sediments from a station in Lydonia Canyon
and from the adjacent slope (both at 550-m water depth) were compared as a
test for differences in scavenging. The analysis was carried out on only the
sediment fraction finer than 60 microns. The heavy metal concentrations were
divided by Aluminum concentrations in order to normalize for textural
variability (Figure 14). For perspective, the resulting concentration ratios
were compared to those in world average shales (Krauskopf 1967).

Four metals (Figure 15) showed a consistently higher enrichment factor in
the canyon axis compared to the slope in each of the three sampling periods.
This is taken as supportive evidence, although certainly not dramatic, that
the potential for scavenging is greater in the canyons.

The hypotheses for greater scavenging in the canyons is more clearly
supported by the distribution of radioisotopes plutonium-239/-240 and lead-
210. Plutonium has been introduced to the ocean surface from nuclear weapons
testing in the atmosphere, and had a peak fallout about 1963. Lead-210 is
continuously generated from the natural decay of uranium. It has a half-life
of 22.3 years and is introduced to the ocean both from the atmosphere and from
in situ decay of dissolved radium-226.

iS

ENRICHMENT FACTOR

d/Al Cr/Al Cu/Al ~ Pb/ Al

Figure 14. Histogram showing the abundance of metals in the canyon axis and
on the slope relative to world average shales (world averages from Krauskopf
1967). Samples used in the calculations are the fine fraction (finer than 60
microns) of the upper 2 cm at 550-m water depth in the axis of Lydonia Canyon
and at the same depth on the adjacent continental slope (Stations 7 and 4 in
Bothner and others 1987b). Metal concentrations have been divided by Al to
correct for differences in sediment texture.

54i6-<

EXCESS ¢!Opb dpom/g
O 10) 20 30 40

SEDIMENT DEPTH (cm)

@LYDONIA CANYON AXIS (627m)
Z\CONTINENTAL SLOPE (630m)

Figure 15. Isotope data suggest active processes in the canyon axis.
Activity of excess lead-210 with depth in sediment cores from the axis of
Lydonia Canyon and from the continental slope (canyon core 4769, 40° 23.87'N,
67° 40.13’/W; slope core 4772, 40° 09.43’N, 68° 20.12’W). Inventories are 223
dpm/g and 86 dpm/g respectively.

Ber (ie

Data from two box cores show that the inventories of these isotopes
(activity/cm’?) are 2.5 times higher in the sediments of the canyon axis than
they are on the open slope. The specific activities (activity/g) are much
higher in the canyon axis as shown in Figures 15 and 16. These observations
are a clear indication that the sediments in the canyon axis are accumulating
more of these sediment-reactive isotopes as a result of the collectively more
active processes operating in the canyon. If a correction were made for the
percentage of fine sediment, the relative enrichment in the canyon would be

even greater.

The depth of penetration of these isotopes is a result of extensive
bioturbation in these sediments. This conclusion is based on the slow rates
of sediment accumulation in both areas and the presence of measurable
plutonium and excess lead-210 activities at depths much greater than can be
explained by the sedimentation rate. Preliminary estimates of the rates of
sediment mixing by organisms suggest nearly the same mixing coefficients for
both locations (about 1 cm*/yr; Bothner and others 1987a). Biological mixing
of the sediments is another mechanism that influences the retention of
contaminants in sediments.

SUMMARY

The data we have collected in Lydonia Canyon suggest that it has higher
potential as a sink for contaminants than adjacent areas of the continental
shelf or slope. The most compelling evidence for greater scavenging in this
canyon is found in the limited data showing inventories and specific
activities of plutonium and lead-210. The possible mechanisms for the
enhanced scavenging are higher rates of sediment accumulation and more intense
and frequent sediment resuspension.

Of the canyons in the North Atlantic OCS study area, Lydonia is the best

studied in terms of physical and geochemical measurements. While additional
information is needed in Lydonia Canyon to confirm some of the processes

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239,240 py dom/q

fe) 20 40 60 80

SEDIMENT DEPTH (cm)

@LYDONIA CANYON AXIS (627m)
ZA\CONTINENTAL SLOPE (630m)

Figure 16. Activity of plutonium-239/-240 with depth in sediment cores from
the axis of Lydonia Canyon and from the continental slope (canyon core 4769,
40° 23.87'N, 67° 40.13’W; Slope core 4772, 40° 09.43’N, 68° 20.12’W).
Inventories are 3.2 mCi/km? and 1.3 mCi/km* respectively.

dou

suggested by our limited data, a full effort is needed in some of the other

canyons of this area as well.

S50=

REFERENCES

Anderson, R. F., Bopp, R. F.; Buesseler, K. 0.; Biscaye, P. E. Mixing of
particles and organic constituents in sediments from the continental
shelf and slope off Cape Cod: SEEP-I results. Continental Shelf
Research. 8(5-7):925-946; 1988.

Bothner, M. H.; Butman, B.; Parmenter, C. M. A field comparison of four
sediment traps: changes in collection rate with trap geometry and size.
In: Butman, B., ed. North Atlantic slope and canyon study. U.S.
Geological Survey Open-File Report 88-27B. 1986:p. 1-22.

Bothner, M. H.; Parmenter, C. M.; Rendigs, R. R.; Rubin, M. The flux and
composition of resuspended sediment in submarine canyons off the
northeastern United States: implications for pollutant scavenging. In:
Butman, B., ed. North Atlantic slope and canyon study. U.S. Geological
Survey Open-File Report 88-27B. 1987a; 62 p.

Bothner, M. H.; Campbell, E. Y.; Parmenter, C. M.; Dangelo, W.; DiLisio, G.P.;
Rendigs, R. R.; Gillison, J. R. Analysis of trace metals in bottom
sediments in support of deepwater biological processes studies on the
U.S. North Atlantic continental slope and rise. U.S. Geological Survey
Open-File Report 88-2. 1987b; 50 p.

Krauskopf, K. B. Introduction to geochemistry. New York: McGraw Hill; 1967.

Twichell, D. C. Geology of the head of Lydonia Canyon. U.S. Atlantic
Continental Shelf. Marine Geology. 54:91-108; 1983.

= 5 2

OVERVIEW OF THE BIOGENIC AND ANTHROPOGENIC HYDROCARBON
DISTRIBUTIONS IN SEDIMENTS ALONG
THE NORTH ATLANTIC MARGIN

Dr. Paul D. Boehm
Battelle Ocean Sciences
Duxbury, MA

Georges Bank and the adjacent slope, rise, and submarine canyon areas are
characterized by highly dynamic sediment transport, deposition, and
resuspension cycles. Important questions concerning the hydrocarbon story for

this area are:

mw What are the overall concentrations of hydrocarbons in the sediments?

mw What is the composition of the hydrocarbon assemblage?

ws What is the distribution of both total hydrocarbons and individual
hydrocarbons?

w What are the sources and sinks of hydrocarbons?

mw What processes control distributions and concentrations?

HYDROCARBON DISTRIBUTION

Results of five MMS, National Oceanic and Atmospheric Administration
(NOAA), Bureau of Land Management, and Department of Energy studies show that
pollutant and biogenic hydrocarbons distributions follow the general trends of
those for fine sediments. Total hydrocarbons and polycyclic aromatic
hydrocarbons (PAH) are found at very low levels in the central bank area where
sediments are coarse. Total hydrocarbon values are 0.5 to 5 ppm for Georges
Bank with PAH values of 5 to 20 ppb. Elevated levels are found in the
depositional areas of the "mud patch" on the shelf south of Martha’s

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Vineyard (10 to 15 ppm and 100 to 2,000 ppb), at canyon heads, and along the
slope and rise (10 to 30 ppm and 50 to 500 ppb). In general, the PAH
compounds are of a nonfossil source indicating combustion as a likely origin.

SEASONAL TRENDS

Seasonal trends are different for total and PAH hydrocarbons. Total
hydrocarbons and terrigenous plant materials do not vary seasonally and appear
to be in an overall steady state (Figure 17). Pristane (a marine biogenic
hydrocarbon) does vary seasonally from a spring high to a winter low (Figure
18). This seasonality is presumably determined by seasonal cycles of erosion
and deposition. Pristane is eventually transported to depositional areas to
the west and southwest of Georges Bank. Sporadic incidence of petroleum
residues (e.g., tar balls) are observed but are relatively short-lived.
Indirect evidence (hydrocarbon chromatograms in conjunction with sediment
textural data) suggests that anthropogenic hydrocarbons are associated with
the easily resuspended fine sediments while biogenic hydrocarbons associate
with the coarser fractions (Table 2). It has been estimated that 40 to 50
percent of the organic matter is resuspended and removed from the shelf to the
slope during fine-grained sediment transport.

= 53 e

TAS 7102 69° 68° 67° 66° Ae how 69° 68° oz 66°

42°

40° E100

(29/9)

e (<1) (5-10)
@ (1-3) ®

@(3-5) & (>10]

Figure 17. Seasonal variations in total hydrocarbon concentrations in
sediments from Georges Bank and Nantucket Shoals. (A) Winter; (B) spring;
(C) summer; (D) fall.

741° 70° 69° 68° 67° 66° as 70° 69° 68° Gre 66°

(g/g)
e (0001-0005) @ [001-0041
@ (0005-0010) @ C004-011

Figure 18. Seasonal variations in pristane concentrations in sediments from
Georges Bank and Nantucket Shoals. (A) Winter; (B) spring; (C) summer;
(D) fall.

Table 2. Comparison of mean silt-clay content and PAH concentrations
in sediments collected in April 1985 (Cruise North-2).

Station Percent Percent
Station Depth (m Sau /Gila Carbon PAH?
11 255 30.6 0.47 49
7 560 9.0 0.20 15
4 550 29.4 0227 39
12 550 58.9 0.86 121
10 1220 68.4 0.80 22:
3 1350 75.6 1.18 132
fe) 1220 88.7 1.41 183
13 1250 93.6 Zu! 141
5 2065 29.8 0.28 28
8 2180 42.0 O52 49
14 2105 47.6 0.54 59
15 2155 5Sa4 0.70 73
6 ZS 54.0 0.43 39
2 2100 sy/ eal 1.06 123

“ng/g dry weight

S°G6n5

RELATION TO TOTAL ORGANIC CARBON

Both the saturates and the PAH compounds are strongly associated with
total organic carbon (TOC) in the sediments. While the absolute concentration
of total hydrocarbons ranges from 0.2 to 20 ppm and of PAH compounds ranges
from about 0.01 to 1.0 ppm, the respective ratios to TOC are relatively
constant, suggesting a well-mixed geochemical area. Saturated hydrocarbons of
a terrigenous plant wax origin dominate the overall assemblage and covary
strongly with TOC and the clay content of the sediment (THC = 0.96 (TOC) +
.29; r=.88). PAH also covaries strongly with TOC (PAH = 2.2 (TOC) - 0.027;
r=.93). The PAH distributions are similar to those originating in the
combustion of fossil fuels, with distributions dominated by the higher
molecular weight (i.e., 4- and 5-ring compounds) rather than petroleum-sourced
PAH. PAH also covaries strongly with terrigenous plant material (r=.93) and
is considered to be either sourced onshore and distributed with the plant wax
residues or is introduced via aerial transport and is mixed and distributed
with other fine-grained material. The PAH/TOC ratios are very similar to
those found in sediments from other geographical areas well removed from the
North Atlantic outer continental margin.

IMPLICATIONS FOR FATE OF POLLUTANTS

The distributions of hydrocarbons in the shelf and slope areas have
important implications for predictions of the fate of pollutants which may
originate through outer continental shelf development. Sedimented
hydrocarbons associated with fine-grained sediments will be redistributed from
their point of origin rapidly (weeks to months) and will be transported to
depositional areas which include canyon heads, deeper slope areas, and shelf
basins such as the "mud patch." In particular, canyon heads are likely sites
for the accumulation of total and PAH hydrocarbons. Although much of the
present data suggests that introduced pollutants will be deposited in canyon
heads and transported down the canyons, hydrocarbon data from muddy lobes
found on the shelf near the heads of Oceanographer and Lydonia Canyons suggest
a canyon source for this mud. Present data are thereby also consistent with

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the possibility of up-canyon transport of fines to the canyon head with spill-
over onto the shelf.

BAGS 2

POTENTIAL EFFECTS OF DRILLING EFFLUENTS ON MARINE ORGANISMS

Dr. Jerry M. Neff
Battelle Ocean Sciences Laboratory
Duxbury, MA

Of more than 25,000 offshore wells drilled in U.S. waters in the past 90
years, more than 10,000 are still in production. During drilling and
production, there are several possible discharges to the ocean and physical
alterations of the bottom that may have adverse effects on the marine
environment. Some discharges are authorized by permit; others are accidental.
The permitted discharges of greatest environmental concern are drilling muds,
drill cuttings, and produced water. The most important accidental discharge
is petroleum through operational spills or blowouts. Physical impacts may be
caused by the mere presence of the platform or by emplacement of pipelines on
the bottom. The major concern in this report is the impact of drilling muds
and cuttings discharges.

Such discharges are diluted very rapidly by dispersion and fractionation.
The heavier solids (representing about 90 percent of the mass of the mud)
settle rapidly to the bottom, usually within 200 to 1,000 m of the rig,
depending upon water depth and current speed. The liquids, soluble materials,
and fine clay-sized particles are carried away from the rig in a near-surface
plume and are diluted rapidly by mixing with seawater. In a typical current
of around 10 cm/s, a dilution of ten-thousand fold--well below toxic or even
sublethal levels--is accomplished within 200 m of the rig in less than half an
hour. Small wonder the National Academy of Science report concluded there is
essentially zero likelihood of any adverse effect within the water column.

The ingredients of greatest concern in drilling muds on the sea floor are
metals, notably barium, chromium, lead, and zinc. Cadmium and mercury are
regulated by the Environmental Protection Agency but are found above
background levels only in association with high concentrations of barium.
Minor ingredients sometimes added to drilling mud that may contribute to its

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impact include diesel fuel or mineral oil, surfactants, and biocides. Many
hundreds of acute toxicity bioassays have been performed with drilling muds,
and nearly 90 percent of the samples were found to be nontoxic or practically

nontoxic to marine organisms.
LABORATORY STUDIES

To test bioavailability, experiments were conducted with juvenile
lobsters and with flounder species. The animals were kept in aquaria with
either uncontaminated or highly contaminated bottom sediments and were fed
either uncontaminated or highly contaminated food over a period of 99 days--
long enough to consume 4 to 5 times their own body weights. Sufficient
drilling mud solids were added to sediment to increase the concentrations of
barium in sediment by 10,000 mg/kg. Flounder and lobsters were examined for
bioaccumulation of barium and chromium and for growth rate and mortality. In
both types of animals, there were no visible effects from eating contaminated
food; however, there were some problems from elevated levels of drilling mud
solids in the sediment. There was some bioaccumulation of barium, but not
chromium, from sediment. It was concluded that minimal bioavailability is
associated with sediments and none with food.

FIELD STUDIES
Review of many field studies in many regions points to three conclusions:
ws Effects on the benthic community are found only in the immediate
vicinity of oil rigs, usually in tranquil environments, and most

recover fully in less than a year after drilling stops.

ws Bioaccumulation of metals is limited to barium and chromium, with
small increases immediately after the discharge.

mw There has been no demonstrated effect of hydrocarbon contamination.

4360)

GEORGES BANK STUDIES

Two stations on the bank, close to exploratory drilling rigs, were
sampled quarterly for 3 years, with 29 stations in a ring pattern around one
rig, and 3 stations near a second rig. The sites were both on the south flank
of the bank, one in 80-m water depth, the other at 140 m. Chemical analyses
by Bothner showed five- to seven-fold increases in barium concentrations in
the bulk sediment, much higher in the fine fraction, and some drill cuttings.
There was a tendency for the barium to migrate as a result of reworking and
resuspension of sediments. There was little or no evidence of hydrocarbon
accumulation.

Biological effects were examined down current from the rigs. At the
shallower station, a strong seasonal signal was found in both diversity and
abundance, but no real biological impacts were attributable to the discharges.
At the deeper site, there was a smaller seasonal signal, but no other
discernible change occurred except a gradual increase over time in both
diversity and species abundance. The increase was attributed to an accident
of timing, as it was also seen at the control sites. Two species of amphipods
virtually disappeared when drilling began, but that was attributed to a severe
winter storm. In short, if there were any effects at all, they were small and
transitory.

DISCUSSION

Several questions concerned the laboratory experiments. Vild asked about
signs of stress in lobsters; there was slight elevation in mortality and
slight decreases in growth. Ray asked for barium concentrations in the
aquaria sediments; they were field muds from Gulf of Mexico rigs, and barium
concentrations were increased above background by 5,000 to 10,000 ppm. Cooper
noted that lobsters are very vulnerable to zinc and copper; Neff responded
that those metals are in forms that are not bioavailable.

ae ee

Maciolek asked about water depths where the most significant impact
occurs; it appears to be around 100 m on the Middle Atlantic shelf, 50 to
100 m in the North Sea. Ray described experiments at 35 feet and 75 m in the
Gulf of Mexico that showed no significant impact. There is no information on
possible impact at significantly greater depths, 500 m or more.

ne

MEGAFAUNAL POPULATIONS IN LYDONIA CANYON
WITH NOTES ON THREE OTHER NORTH ATLANTIC CANYONS

Dr. Barbara Hecker
Lamont Doherty Geological Observatory
Palisades, NY

Lydonia Canyon is a relatively narrow canyon that incises Georges Bank
approximately 11 mi north of the shelf-slope break. It has a narrow sediment-
covered axis flanked by steep walls with massive exposures of outcrop and
talus-strewn slopes.

Megafaunal populations in Lydonia Canyon were surveyed photographically
during 16 camera sled tows and 17 Alvin dives between May 1979 and September
1982. Nearly 115,000 square meters of sea floor, between 130- and 2,330-m
depth, were analyzed. More than 750,000 animals were identified. The analysis
included data on water depth, surficial geology, current indications, species
identification, and abundance. The area viewed was estimated for most of the
pictures since flat terrain was rarely encountered. The Alvin dives were used
to obtain data in very steep regions and collect "voucher" specimens for
better taxonomic identification.

RESULTS

Faunal abundance was much greater in the canyon than at comparable depths
on the slope. Total megafaunal abundance in the canyon was very high (up to
30 individuals/m?) at shallow depths, and intermediate at mid-slope (5
individuals/m?) and lower slope (7 to 8 individuals/m*) depths. Highest
concentrations were along the canyon axis, but abundance was also high on the
flanks, especially in areas of outcrops or boulders. Between 350 to 450 m in
the axis there were very high concentrations of a sea pen (Pennaula aculeata)
and brittle stars (Ophiura spp); other high concentrations were at 800 to
1,000 m (mostly hard-substrate corals) and below 1,600 m (a different brittle
star (Ophiomusirium lyman7)).

acco

The "percent similarity" index was used as a mathematical indication of
faunal similarity. The resulting cluster structure was a function of both
depth and location within the canyon. Clusters grouped at relatively low
percentages (15), an indication that many of the taxa were patchily
distributed.

Geographical mapping of the cluster results shows 5 broad faunal zones
(using the word "zone" loosely since clusters were usually a result of high
abundances of few species and clusters only grouped at 15 percent similarity)
on the walls and flanks of the canyon. The faunal distributions within the
canyon axis at depths of less than 1,500 m were extremely patchy and complex,
reflecting the substrate heterogeneity and active physical regime.

Cluster 1 consists of areas that are centered on the 200-m isobath around
the canyon rim. Species common to all areas in this cluster are crabs (Cancer
sp.), black-bellied rosefish, the anemone, Actinauge longicornis, and the
starfish, Sclerasterias tanneri.

Areas in cluster 2 range from 300 to 475 m but do not extend into the
canyon past the upper flanks. Common species are Bolocera tudiae, Hyalinoecia
artifex, Actinauge veri]]i, and long-finned hake.

Areas in cluster 3 are between 500 and 1,000 m and have a mud to cobble
substrate, with Synaphobranchus kaupi, Geryon quinquedens, Glyptocephalus
cynoglossus, and Asbestopluma sp.

Areas in clusters 4 and 5 are the deepest, with Distichoptilum gracile
and a cerjanthid anemone in both and Ophiomusium lymani in 5.

In contrast, the clusters consisting of axis areas (clusters 7, 8, 9) are

typified by a variety of corals and sponges, in addition to the background
fauna of clusters 1-5.

ey ae

GENERAL OBSERVATIONS

The canyon has a higher diversity than does the slope, reflecting the
addition of sessile filter feeders to the background slope fauna. At mid-
slope depths, carnivores predominate on the slope, while filter feeders are
preeminent at all depths in the canyon axis. In both regions, diversity is
higher on hard substrate than on soft. Diversity also increases with the size
of the hard substrate, being lowest in cobble areas, and highest on cliffs.

OTHER CANYONS

In 1977 Alvin made three dives in Oceanographer Canyon, three in Heezen
Canyon, and one in Corsair Canyon. The same kind of cluster analysis used in
Lydonia Canyon shows disparity among the three canyons, possibly reflecting
the disparity in their morphology and corresponding differences in their
physical regimes: Oceanographer Canyon is wide, with low stepped cliffs and
comparatively heavy sediments; Heezen is very narrow and deeply incised, with
large Eocene chalk cliff flanking the axis. Corsair is mostly sediment
covered with limited exposures of hard substrate. Only some of the faunal
differences among the canyons could be attributed to availability of hard
substrate.

CONCLUSIONS
ws Distributions of megafaunal assemblages in the Georges Bank canyons
are complex with a high degree of patchiness in many of their faunal

constituents.

ws The canyons are marked by high concentrations of sessile filter
feeders (corals and sponges).

a The different patterns reflect substrate heterogeneity, enhanced

current speeds within the canyons, resuspension events, and probably
the concentration of fine particles in the axis.

= 65) =

m The increased sediment load in the water column may stress filter
feeders through tissue abrasion, clogging of filter apparatus and
decreased larval settling. There may also be indirect effects through
changes in the substrate itself.

DISCUSSION
Bothner asked if the sled is remotely controlled. The answer is no; it

takes a picture every 15 seconds. There is too much tendency for an operator
to introduce bias by increasing coverage where the fauna is abundant.

igor2

BENTHIC INFAUNA OF LYDONIA CANYON
AND THE ADJACENT SLOPE ENVIRONMENT

Dr. Nancy J. Maciolek
(formerly of) Battelle Ocean Sciences
Duxbury, MA
and
Dr. J. Frederick Grassle
Woods Hole Oceanographic Institution
Woods Hole, MA

The Georges Bank Benthic Infauna Monitoring Program was carried out
between 1981 and 1984, and a deep-water characterization study (Study of
Biological Processes on the U.S. North Atlantic Slope and Rise) was made from
1984 to 1986. In both programs, the benthos was sampled quantitatively at
several stations including stations in Lydonia Canyon and on the adjacent
slope. The canyon/slope stations were at three water depths: approximately
150, 550, and 2,100 m. Stations were sampled from 3 to 8 times. Sampling was
conducted seasonally, but because we did not see pronounced seasonal effects,
the results are presented as an overview for each station.

COMMUNITY STRUCTURE

To assess community structure of the infaunal benthos, we recorded
species composition and abundance, and then determined which species were
numerical dominants at a station on a given sampling date and over al]
sampling dates. We also looked at diversity using the Shannon-Wiener
information index and the Hurlbert rarefaction method. Similarity among
samples and stations was also evaluated using the NESS similarity measure,
followed by cluster analysis.

oe yee

150-Meter Stations

One of the two 150-m stations in Lydonia Canyon was sampled four times
and then relocated, because at the first site we were sampling the wall of the
canyon where sediments were highly variable. In general, sediments at this
first site were very coarse, with less than 1 percent silt-plus-clay. At the
new station location where sediments were finer, the average silt-plus-clay
was about 30 percent. The slope station outside the canyon had fine sandy
sediments, with about 2 percent silt-plus-clay.

Faunal Composition and Dominance

Species composition was strikingly different between the two canyon
stations. Of the top 20 numerically dominant species, 8 were shared between
the two stations, but none of the top 10 dominants at one station were among
the top 10 at the other.

The dominant species at the coarse-sediment canyon station was a
polychaete, Lumbrineris latreil]i, which accounted for 7 percent of the fauna.
The rank of several of the subdominants at the coarse-sediment station varied
widely over the four sampling dates, probably because the same sediment type
was not sampled each time.

At the fine-sediment canyon station, the top dominant was the amphipod
Ampelisca agassizi, which accounted for about 12 percent of all individuals.
This species consistently ranked either first or second, except once when it
ranked fourth.

At the adjacent slope station, this same amphipod was the top dominant on
each of 12 sampling dates. Here, however, Ampelisca accounted for 35 percent
of all individuals. Comparing dominants between the canyon stations and the
slope station, there were more in common between the coarse-sediment station
and the slope station than between the fine-sediment canyon station and the
slope station. Of the top 20 dominants at the coarse-sediment canyon station,

£68.

13 were also dominant at the slope station. Of the top 20 dominants at the
fine-sediment canyon station, only 4 were also dominant at the slope station.
Density was highest at the fine-sediment canyon station, followed by the
coarse-sediment canyon and slope stations.

Diversity

We measured diversity using both the Shannon-Wiener information index and
the Hurlbert rarefaction method. The coarse-sediment canyon station had the
highest Shannon-Wiener diversity (5.41), followed by the fine-sediment canyon
station (4.72). The slope station had the lowest diversity (4.25).

For the rarefaction method, we calculated the number of species expected
for a given number of individuals. This method allows us to compare samples
of unequal sizes by reducing them to a common sample size. According to this
measure, the two canyon stations were less diverse than the slope station.

Similarity

Based on this analysis, we found that none of the three 150-m stations
were really very similar to each other. The canyon station with fine
sediments was seen to be most similar to a station in the "mud patch" located
far to the west (on the shelf south of Martha’s Vineyard). The coarse-
sediment station was similar to a station near the head of Oceanographer
Canyon, and the slope station was most similar to other slope stations near
the drill site in Block 410, several kilometers away. Despite the dominance
of Ampelisca at both the slope and fine-sediment canyon stations, the
remaining faunal composition at the two stations was very different.

550-Meter Stations
There were two stations at 550 m, one inside the canyon and one on the

adjacent slope. Sediment texture--a muddy sand--was very similar at the two
stations.

- 69 -

Faunal Composition

As at the 150-m stations, faunal composition was very different between
canyon and slope stations at 550 m. The same small polychaete, Tharyx
baptisteae, was the top dominant at both stations, but it accounted for 32
percent of total individuals at the canyon station and only about 6 percent at
the slope station. In all, of the top 20 dominant species, only 6 were
dominant at both stations.

Many species occurred at both stations but in significantly different
densities. We used analysis of variance to test for significant differences
in mean densities of individual species found at both stations: in almost al]
cases, differences between stations were highly significant. For example,
abundance of the bivalve Nucula subovata was significantly higher at the slope
station, whereas the polychaete Cossura longocirrata was significantly more
abundant at the canyon station. As at 150 m, total densities were much higher
in the canyon than on the slope.

Diversity

Using either the Shannon index or Hurlbert rarefaction, the canyon
station had lower diversity than the slope station. The Shannon H’ values
were 4.66 in the canyon and 6.00 on the slope.

Similarity

We compared the 550-m stations among themselves and with all other
stations sampled in the program. Cluster analysis of the 550-m stations
showed the slope station near the canyon to be more similar to another 550-m
slope station several kilometers distant than it was to the nearby canyon
station. The same pattern was seen when all stations were analyzed together.

2 101

2,100-Meter Stations

We sampled three stations at 2,100 m: one in the canyon and two on the
adjacent slope. At this depth, the story was very different from that at 150
or 550 m. At 2,100 m, the fauna at all three stations was very similar. The
top dominant species at all three stations was the polychaete Aurospio
dibranchiata, the dominant infaunal species at 2,100 m along the east coast of
the United States at least as far south as Cape Hatteras. This species
accounted for 8 to 11 percent of all individuals at each station. At
shallower stations, the percentage contribution of the top dominant species to
each community was very different.

Of the top 20 dominants at the 2,100-m stations, 11 or 12 were shared
between the slope and canyon stations, compared to 4 or 6 species shared
between canyon and slope stations at the shallower depths. Total densities
were similar at all three 2,100-m stations.

Diversity

Also in contrast to the situation at the shallower stations, diversity
was higher at the canyon station than at either of the 2,100-m slope stations,
whether measured by Shannon-Wiener or Hurlbert rarefaction.

Similarity

At 150 and 550 m, the canyon stations were clearly different from the
adjacent slope stations. At 2,100 m, the canyon station was highly similar to
the slope stations.
SUMMARY

In conclusion, we see that major differences in community structure occur

between canyon and slope stations at 150 and 550-m depth, but differences at
2,100 m are minor. Most interestingly, it appears that although subtle

agers

differences in sediment texture may account for faunal differences at 150 and
2,100 m, at 550 m the current regime may be more important than sediment
texture.

At 550 m, the sediment texture was similar at both the canyon and slope
station, but there is evidence that currents may cause much sediment
resuspension (presentation by Butman).

There appear to be differences in epifauna on the slope and in the canyon
at 550 m (presentation by Hecker). The red crab (Geryon quinquidens) is
common on the slope and may cause greater predation pressure on the infaunal
communities there.

RECOLONIZATION

Rates of recolonization were investigated using two designs of a free-
vehicle sediment tray, which were used to expose defaunated sediments at
2,100 m. The sediment was frozen and thawed to kill all living organisms
before being used in the trays. Based on field data, results from both
designs were found to be comparable.

Sediment trays were placed at three stations at 2,100 m on the slope.
Two were on the slope near Lydonia Canyon and one was several kilometers to
the west. Trays near the Lydonia Canyon stations were exposed for 7 months,
and those at the third station for 14 months. Average density at the 7-month
stations was 35 individuals/m?. At the 14-month station, after twice as long
an exposure, density was about 12 times as great: 416 individuals/m?.
However, this still was far lower than the normal density of about 4,000
individuals/m*. From these results, it is likely that deep-sea benthic
communities would take years to recover from a catastrophic impact.

tee

MASSACHUSETTS’ PERSPECTIVE ON SUBMARINE CANYONS
AND DRILLING AROUND THESE CANYONS

Ms. Patricia E. Hughes
Massachusetts Coastal Zone Management Office
Boston, MA

In late 1983 and through 1984, the Minerals Management Service, along

with the National Marine Fisheries Service and the U.S. Geological Survey,

worked on the development of a stipulation that prohibited drilling within 200

m of the submarine canyons in the North Atlantic OCS planning area. A further

part of the stipulation required monitoring of exploratory drilling activities

within 4 mi of the submarine canyons. This no-drilling stipulation was

established for three reasons:

to protect the unique biological habitats of the canyons
(presentations by Dick Cooper, Barbara Hecker, and Nancy Maciolek
discussed this aspect of the canyons. Dick called the canyons a very
unique habitat and indicated that the canyons are important nursery
areas for a number of species. Brad described the canyons as a
complex environment. )

to protect the important biological resources (Dick Cooper highlighted
the variety of species using the canyons that are subject to the
commercial fishery.)

to avoid spatial exclusion of fishing activity and minimize conflicts
between fishing (particularly pot fishing for lobsters and red crab
and long-line fishing for tilefish and swordfish) and petroleum
activity

Five years after the no-drilling stipulation, it is my opinion that the

information we’ve heard today reinforces the original no-drilling stipulation.

If the stipulation did not exist, the canyons would be viewed as areas of

oe cee

special biological significance, and stipulation 2 (the biological
stipulation) would be invoked. There would likely follow debate on whether
drilling should be allowed. If drilling were allowed, discharges might be
prohibited. If not prohibited, it is likely that discharge restrictions would
be required, as well as monitoring. The MMS has traditionally taken the
position of conditioning activity, and placing restrictions on drilling
activity in order to avoid deferring areas from leasing.

The MMS has taken this approach in some controversial areas, and in many
areas it has been a sensible method. But, in the North Atlantic, the
information argues for no drilling in submarine canyons, and further argues
whether, in fact, the 200-m exclusionary zone is sufficient.

I will close by noting that, although the present focus is exploratory
drilling, the potential impacts of development and production are what most
people are concerned about. The reasons include:

w transport of materials

mw pollutants attached to fine-grained sediments

m question of the fate of fine-grained materials in the canyons
mw recognition of the unique canyon habitat

All four argue for preventing these areas from being leased in the first
place.

S47 Ate

THE RHODE ISLAND PERSPECTIVE ON SUBMARINE CANYONS

Mr. Bruce F. Vild
Division of Planning
Rhode Island Department of Administration
Providence, RI

Even though this workshop and the studies program focus on science, I
hope everyone recognizes that science is only one facet of the controversy
over submarine canyons. Politics, economics, and public opinion enter
strongly into the policy equation--and influence the governors’ decisions, in
Rhode Island and elsewhere.

In New England, public opinion favors the fishermen. New Englanders are
suspicious of the oil companies, and by extension, the Department of the
Interior. Both are seen as a threat to fisherman. Attitudes displayed at
public hearings demonstrate this clearly. Some of the notions held by the
general public about fishermen and the environment may seem romantic, but they
must be not be ignored. They have an impact.

Supporting offshore drilling is unpopular in New England. Any policy
that a governor makes endorsing OCS exploration has to be tempered, not only
by environmental and scientific considerations, but also by political ones.
For my governor, or any governor, to support drilling in submarine canyons, it
will require far more than a statement that such activities are relatively
benign--assuming that such a statement is defensible. (Rhode Island is on
record opposing leasing and drilling in the canyons.)

On the economics side, the governors have to ask this about OCS
exploration: what’s in it for New England? Are the oil companies willing and
able to make any long-term commitment to the economic health of the region
that will balance the risk (perceived or actual) of allowing drilling--
especially in such controversial areas such as the submarine canyons? Since
there have been eight dry holes on Georges Bank, there is no direct evidence

- 75 -

that New England is going to benefit by its governors supporting offshore
drilling. Because the odds are against finding oil and gas in the North
Atlantic, the oil companies simply can’t make any guarantees that would make a
governor’s policy-making easier if he or she decides to endorse a drilling

program.

The voters know the fishermen and the environmentalists. They don’t know
the oil and gas explorationists. The oil and gas explorationists don’t have a
permanent presence in New England. When criticisms of the industry are made
or issues arise, there is no spokesperson for them to provide a counterpoint
to advocates for the fishermen and environmental groups. Public opinion
responds accordingly.

These are the political realities. And decisions are made by elected
officials--who are very sensitive to public opinion.

So, although I hope science will continue to play an important role in
the submarine canyon controversy, we have to keep in mind that science is not
the only thing that will be considered if the canyons are ever offered for
lease.

DISCUSSION

Aurand: Considering that exploratory drilling on Georges Bank didn’t
cause any damage, why has this fact been unsuccessful in reducing tension?

Vild: I’m not convinced that opposition hasn’t lessened, at least from
some of the fisherman’s groups, but there seems to be a consolidation of
interest around certain points--the submarine canyons, for example.

Hughes: For various reasons, including increased public awareness of the
Georges Bank fishery with passage of the 200-mi limit, research funded by DOI
that has helped to better define the Georges Bank system (for example,
described features that make Georges Bank "special"), reduction in resource

eyGus

estimates, and now, shared jurisdiction with Canada, and different national
philosophies on petroleum development and fisheries management, there is
heightened interest in the region. And, to most people, Georges Bank means
"fishes"

Ray: I see some hypocrisy here. There should be an environmental impact
statement on the different fisheries. In truth, there are many tradeoffs
involved with the fish that goes on your dinner table. Fishing tears up the
environment and, because of the by-catch, is often very wasteful.

People aren’t being honest with themselves. On the one hand, they’re
talking about hypothetical impacts, and on the other, they’re overlooking
actual impacts and damages that are quite routine.

Hughes: The science of fisheries management is as inexact as is the
predicton of the effects of oil and gas activities. The public is realizing
that there are questions about the conduct of the fisheries and on
conservation and management efforts.

Vild [on the subject of trying to avoid conflicts between the industries
or with the environment]: How about directional drilling in canyon areas?

Ray: Industry prefers straight drilling in the exploratory phase, but
development could use directional drilling.

Cooper: Looking at the fisheries in general, the likely impact
(negative) of oil and gas drilling operations on the commercial fisheries of
submarine canyons is greatly overshadowed by living resource losses. These
losses are due to man’s inability to wisely manage the fisheries, the
industry, or the ocean-floor environments that support a major portion of the
fishery, for example the groundfish (flounder, hake, cod, lobster, etc.)
fishery. At some point in the future, when oi] prices rise, and our
production is lower than it is now, what will we do then? The issue now is a
relatively easy one--compared perhaps to the future.

han) ff es

Vild: Jim Ray, what are the prospects of direct industry-to-industry
talks...that address topics like space restriction and gear loss? Can the two
industries come to a consensus?

Ray: There has been progress along this line in Alaska and California,
for example. There is a liaison office in California that provides a good
model to build on.

Teal: I suggest that exploration be decoupled completely from
development and production. Then, exploration could assess the resource,
without an automatic follow on. Decisions on production and development could
be made with the knowledge of the value of the resource present.

Vild: That wouldn’t work unless the government was willing to subsidize
exploration.

Ray: Industry would object to the government getting into the
exploration business. Competition and sharing of information would be
Factors.

Teal: I’m not saying that it’s easy or even possible, but to decouple

the process would allow the public to know the value of the resource prior to
leasing for development.

S Re

ROUNDTABLE DISCUSSION:
SUMMARY AND SYNTHESIS
GEOLOGY AND GEOCHEMISTRY OF NORTH ATLANTIC SUBMARINE CANYONS

Dr. Bradford Butman, Chairperson
U.S. Geological Survey
Woods Hole, MA

Following the first day’s scientific presentations, a roundtable
discussion of existing information on submarine canyons was held with an eye
toward producing a consensus summary document. The focus for consensus was to
be on mechanisms and not necessarily impacts. Agreement on mechanisms is
necessary to assess potential impacts of drilling from routine operations and
discharges, accidental spills, and "worst case" events.

GENERAL DESCRIPTION OF CANYONS

The submarine canyons that incise the southern margins of Georges Bank
vary in size, shape, and length. In some cases, they extend for long
distances past the shelf break onto the continental slope. Studies have been
conducted both in shallow- and deep-water parts of the canyons (see background
papers given on Day 1 of the workshop). These studies have shown that canyons
exhibit widely different sedimentary environments. Characteristics which
differ from canyon to canyon include sediment texture, bottom currents, and
intensity of erosional and depositional processes.

The workshop conclusions focus on the shallow parts of the canyons,”
defined as the area from the canyon head to the point where the canyon crosses

"See also reviewer comment in Appendix A.

= 79'=

the shelf-slope break (200-m isobath). These canyon areas (enclosed on three
sides by the shelf) are those most likely to be impacted by drilling on the
shelf, on canyon rims, and on the uppermost slope near the canyons.

Butman offered a series of general statements based on the concept of a
"typical" canyon, with a length of 10 to 20 km, a depth of 500 to 1,000 m, and
a width at the mouth of approximately 5 km (Figures 19 through 22 illustrate a
variety of canyon types in the Georges Bank region). Although the axis and
rim areas comprise a small portion of the total area of canyons, most of the
biological and geological sampling has been done in these areas. In contrast,
many of the visual observations made by submersibles in canyons have come from
the canyon walls. Nearly all the information to date has been obtained from
the upper portion (less than 700 m) of a very few canyons.

PHYSICAL FEATURES OF CANYONS

Many statements presented in the workshop were largely applicable to the
large, deep canyons such as Oceanographer, or the generic canyon presented in
the preceding figures (Figures 19 to 22). These statements were progressively
amended during discussion to include conditions and mechanisms found in other,
generally smaller canyons such as Lydonia. Throughout the workshop the
question was posed, in a number of different forms, as to just how applicable
many of the broader statements were to canyons in general.” The heterogeneity
of canyons was widely recognized.

There was consensus on the fact that canyons are unique habitats and
environments--as compared to slopes at comparable depths.

The general categories by which canyons could be defined as unique were:

ms Topography and features: canyon shape, substrate type, and
patchiness;

"See also reviewer comment in Appendix A.

Se e0ies

Figure 19. Map of Oceanographer, Heeltapper, and Filebottom Canyons located
on the southern margin of Georges Bank. Oceanographer is a large canyon, and
its shallow northern part incises the continental shelf for 25 km. By
contrast, Heeltapper is a small canyon that incises the shelf north of the
200-m isobath for only 3 to 4 km. Filebottom canyon is a slope canyon that
does not cut into the shelf. Dashed line is location of section in Figure 11]
(adapted from Valentine 1987).

=A). =

67°55"
EXPLANATION
+ SAMPLE
& CURRENT METER
—~ DIVE TRAVERSE
4t MULTIPLE DIVE TRAVERSES
(i sano bunes
= MET SEDIMENT TRANSPORT
D7 mano sanny Graver

Oo S WILOME TERS

Bothymotry im motors

GULBERT

Figure 20. Map of Gilbert and Lydonia Canyons located on the southern margin
of Georges Bank. Gilbert, a large canyon, has greater volume and relief than
Lydonia, a median-size canyon, which is longer. Dashed line is location of
section in Figure 11] (adapted from Valentine 1987).

Go.

69°05'__ 69°00

HYDROGRAPHER
CANYON

EXPLANATION
* SAMPLE
@ CURRENT METER
SAND DUNES
— NET SEDIMENT
TRANSPORT
2 KILOMETERS

Bathymetry in meters

Figure 21. Map of Hydrographer Canyon, a large canyon located on the southern
margin of Georges Bank. Dashed line is location of section in Figure 11
(adapted from Valentine 1987).

=.83 =

(eae ee ae ee eT

SHALLOP

ATLANTIS HEEL TAPPER

VEATCH

LYDONIA GILBERT

HYDROGRAPHER
OCEANOGRAPHER SEA LEVEL
500

ee]
1500
ie} SOO METERS

Figure 22. Cross section of 12 Georges Bank (North Atlantic) canyons and
Hudson Canyon (Middle Atlantic) at the 200-m isobath (see dashed lines in
Figures 8 to 10). Horizontal line above each section is sea level. No
vertical exaggeration. (Figure from Valentine 1987).

= $4. -

Currents: decoupled from the shelf flow; stronger or weaker; extremes

a
in current speed: net and oscillatory flows;

mw Resuspension of fine-grained sediment: intensity and frequency;

w Species diversity and density: epifauna and infauna; different
trophic structure and feeding strategies;

w Role in fisheries: largely untrawled areas; nurseries for shelf
fisheries; refuge sites; stock populations;

a Different geochemical environment and potential for pollutant
scavenging as expressed by different lead-210 and plutonium-239/-240
inventories;

ws Sediment accumulation rates: higher or lower.

QUESTIONS

To match scientific questions with supporting data, a list of questions

was developed in the general area of the geology and geochemistry of submarine

canyons.

Each question was followed by a short list of data categories.

Each

category is assessed as to whether the data support the idea (Y or N in the

first column); and which canyon(s) provided the data (second column:

O=Oceanographer; L=Lydonia; A=Atlantis; H=Hydrographer. )

Do particles (sand and fine-grained sediment) enter canyons from the

shelf, based on:

Y/N G
1. Flow regime and calculations? 1 L
2. Barium concentrations? Y L

- 85 -

3. Submersible observations? Y O,E.A,H

4. Sediment texture? Y 0,L,A,H
5. Seismic surveys? Y L
6. Accumulation rates? Y L

Sources: Butman for flow regime, Bothner for barium and accumulation
rates, Valentine for submersible observations and textural
analysis, and Twichell for high-resolution seismic data.

This information as presented met with general agreement.

ws Does fine-grained sediment accumulate on canyon floors (over last few
thousand years)?

Y/N C
1. Measured accumulation \j L
2. Texture and bedforms
Texture and bedforms N
3. Seismic surveys Y L
4. Convergent transport Y L

Sources: Butman for convergent transport data, Bothner for measured
accumulations, Valentine for texture and bedforms, and Twichel]
for seismic data.

S(96c=

There was general agreement that fine-grained sediment accumulates on the
floors of canyons of moderate size and energy, such as Lydonia, but not on the
floor of the best known large, deep, and high-energy canyon, Oceanographer.

m Is there evidence of contaminant accumulation, based on:

Y/N G

1. Sediment resuspension

(stripping, scavenging)? Y LO
2. Lead-210 and plutonium-239/-240

inventory? Y L
3. Lead-210 and plutonium-239/-240

concentration? y L
4. Trace metals? Y L
5. Hydrocarbon concentrations? N*

‘except Hudson canyon, where sludge dumping occurs

Sources: Bothner is source for the first four data categories, Boehm for
hydrocarbon data.

It was generally agreed that there is a high potential for contaminant
accumulation in canyons where fine-grained sediments are accumulating. This

is most clearly the case in Lydonia Canyon where resuspension of sediment
augments contaminant scavenging by fine sediments."

"See also reviewer comment in Appendix A.

2.87) &

DATA NEEDS

A few of the limitations of the available data were discussed, and
several areas of scientific information needs were listed:

= Physical processes: largely confined to water depths between 100 and
750 m, mostly in two canyons (Lydonia and Oceanographer)

a Lead-210 and plutonium-239/-240 data as an indicator of sediment
stripping efficiency

ws Rates of sediment accumulation and transport: canyons are possibly

"leaky systems"

w Radioisotope studies limited to one canyon (Lydonia)

s Biological processes, including mechanisms controlling species
diversity: variable substrate, limited exploitation, and temperature
controls

mw Geochemical data: walls vs. axis

mw tlextural data: none below 750 m

Aurand observed that agreement on things known was more useful for MMS
purposes than agreement on things unknown.

2°99 .

ROUNDTABLE DISCUSSION:
SUMMARY AND SYNTHESIS
BIOLOGICAL COMMUNITIES OF NORTH ATLANTIC SUBMARINE CANYONS

Dr. Barbara Hecker, Chairperson
Lamont Doherty Geological Observatory
Palisades, NY

Barbara Hecker assumed the chair for the discussion of biological
communities in submarine canyons. In somewhat the same format as Butman, she
presented a series of statements for discussion, amendment, and consensus.

s Do biological characteristics of canyon populations differ from those
of the outer continental shelf/upper slope in the following ways?

Megafauna Infauna
(all (Lydonia
Canyons) only)
1. Higher Biomass Lf Y
2. Higher Density yi uf
3. Faunally mediated contaminant
concentration via filter
feeding strategies (inferred) * ¥ f
4. Nurseries for commercial species Y -
5. Higher concentration of
commercial species Y -

*See also reviewer comment in Appendix A.

- 89 -

6. Species composition shifts Y ¥

7. "“Distinctiveness" of canyon
species Y ?
"Distinctiveness" was expressed in a number of different forms: "canyon

indicator" species and communities, "unique" species and communities, and
commercially important species "typically" found in canyons. Although it was
agreed that no species is unique to canyons, a number are particularly
diagnostic of canyon environments. These include the white hake, tilefish,
lobster, and various corals and sponges. Further discussion dealt with
various aspects of canyon populations including: migratory species vs.
permanent residents; mobile vs. attached (sessile) forms; and juvenile forms
that use canyons as nursery sites. Cooper stated that canyons are unique for
lobsters in that they serve as a major nursery site as well as home grounds.
Valentine said distinctive bottom communities such as the "pueblo villages"
(burrowed outcrops of Pleistocene silt that harbor a diverse fauna of fish and
crustaceans) are found in some larger canyons but not in small, shallow
canyons or gullies such as Heeltapper, Filebottom, and Dogbody. It is
difficult to agree on a generic "canyon" classification when present data
suggest there are at least three types of canyons along the Georges Bank
shelf. Butman suggested that the biological characteristics could be applied
on a canyon-by-canyon basis. Teal pointed out that the people presently
discussing the issues were best qualified to do that.

POSSIBLE BIOLOGICAL IMPACTS

Hecker continued with a series of questions on possible impacts of
drilling on canyon communities.

ms What are the "stock" populations in canyons and how are they
influenced?

2 90 =

a What controls settling success in benthic communities? What are the
cues in settling? Are they physical? Are they chemical? What
concentrations of what contaminant may interfere with the cues?

ws Are there different impacts at different life stages for the same
organism?

a What are short-term impacts vs. long term impacts?

Teal expressed the opinion that very often it takes at least a 10 percent
change in the physical environment before an animal perceives it. Offering a
very conservative opinion, he suggested that a 1 percent change in an
environmental parameter to which animals are particularly sensitive would have
no impact on an organism or a community. If the parameter starts at a value
well below that to which the animal is sensitive, a much larger change would
have no effect.

Cooper asked what specifically were the real dangers of drilling? Are
direct impacts such as suffocation by cuttings and drilling mud adjacent to
rigs more important or of greater concern than (as an example) impacts related
to the uptake of heavy metals? Ayers suggested that immediate impacts are
restricted to within a few hundred meters of the drill site and no significant
heavy metal impact has ever been seen. Most drilling mud metals are very
insoluble and the only ones present in concentrations significantly higher
than concentrations found in marine sediments are barium and sometimes
chromium. There is no evidence to suggest that barium, when present as barium
sulfate as it is in drilling mud, is a "bad actor" when introduced to healthy
marine populations. Ayers stressed that barium (as barium sulfate) is the
only drilling-mud component that is elevated in the sediments at distances
greater than a few hundred meters from the wellsite.

2x9 i

Cooper suggested that, under conditions of normal drilling operations,
there would be no measurable impacts. He then suggested that, in a "worst
case" scenario (a major oil spill), there may still be only short-lived
impacts. Since most commercially valuable species in the canyons are mobile
and fast and grow to maturity at a young age, most populations would be
capable of bouncing back from even a major oil spill.

Neff stated during this discussion that the major impact would be to
surface waters, possibly eggs and larvae of fish, and that may include cod,
haddock, and others. Neff further stated that he did not know of a mechanism
to transport enough oi] to the bottom to cause any serious long-term impacts.
For example, with cod fish, the eggs are on the bottom, they rise to the
surface, and then gradually sink back down again. So there is a period where
they are in the top meter or two. The fishing modelers hypothesize that the
period at the surface is the only opportunity for serious impact. Teal
suggested that a major oil spill was not the only "worst case" scenario. For
example, if one could imagine an event that transported a large amount of
long-lasting, toxic materials to the bottom in a localized area such as a
pueblo village, that might have a much grater effect than oil spilled on the
surface, little of which would even reach the bottom near canyons.

IMPACTS ON SESSILE ORGANISMS

Hecker stated that since commercial species are mobile and have rapid
growth, one would expect primarily short-term effects. But with sessile
species, effects are more likely to be long term. In a worst-case scenario,
where one would wipe out a local population, there would be concern about the
sessile organisms. If you wipe out a population in one canyon, have you wiped
out the entire "stock" population of that species, or is there substantial
transport and recruitment between canyons? She said that her instincts are
that the effects will be longer term, because the sessile organisms can’t

"See also reviewer comment in Appendix A.

= 922

"walk in" and repopulate an area. This leads to the question of how much of

the stock population are you wiping out? It will be a much higher percentage
for the sessile organisms that inhabit the canyons. Ayers and Hecker agreed

that the deeper one goes, the longer recolonization would take, and the more

sensitive the organisms become.

GEOGRAPHIC EXTENT AND AREA OCCUPIED BY CANYONS

Cooper stated that 20 percent of the upper continental slope off Georges
Bank is occupied by submarine canyons.” Hecker questioned whether the small
"noncanyons" should be subtracted. Teal summarized by saying that there seems

to be general agreement that the canyons occupy a substantial portion of the
upper slope.

"See also reviewer comment in Appendix A.

= 0}

FINAL SUMMARY SYNTHESIS AND CONCLUSIONS

CHARACTERISTICS OF CANYONS

To best summarize the information presented in a full day’s scientific
presentations and nearly a full day of roundtable discussions, "information
capsules" were prepared on the principal topics that seemed to underlie the
conclusions and recommendations of the scientific panel. These capsules
follow on the next several pages.

Submarine Canyons - Special Environments

Submarine canyons support a higher concentration (numbers, biomass, and
diversity) of large, bottom-dwelling animals than adjacent environments on the
continental shelf. The high biomass and diversity of commercially important
species such as lobsters, crabs, shrimp, flounders, hake, ocean pout, cusk,
and tilefish at the heads of canyons is primarily due to the wide variety of
substrate types. These substrates provide three-dimensional shelters,
including burrows and grottos excavated by the animals. Such shelters are
frequently utilized by juveniles, making the canyons important nursery
grounds. At greater depths along the canyon axis, and down the walls, are a
variety of corals and sponges. Many of these corals and sponges, along with
the cleaner shrimp, black-bellied rosefish, and tilefish from the shallow
regions of the canyon heads, are found only in canyons. Also, several species
that are common on the continental slope, such as brittle stars, long-nosed
eels, rattail fish, and sea pens, are found in much higher abundances in
canyons. The specific species composition varies from canyon to canyon,
probably reflecting physical differences among canyons. The sessile species
in the deeper canyon axis may represent an important proportion of the total
local population. These stock populations may be necessary for future

EeOAy =

recruitment to other areas. The submarine canyons of the northwest Atlantic
that fit this characterization are the following:

Corsair Heezen

Powel ] Lydonia
Gilbert Oceanographer
Hydrographer Veatch
Atlantis Block

Hudson Norfolk

There are other, smaller canyons and gullies, but they more closely
resemble habitats on the continental slope, or have not been studied.

Submarine Canyon Morphology and Sedimentary Environments

Submarine canyons on the southern margin of Georges Bank exhibit wide
variability in size and shape. Canyon morphology modifies axial current flow
that, in turn, is linked directly to variability of sedimentary environments.
The largest canyons incise the shelf 13 to 25 km and have 750 to 1,000 m of
relief at the shelf break (200 m). They are characterized by strong currents
and heterogenous sedimentary environments that include large areas of gravel,
rippled and duned sand, and bioeroded Pleistocene silt and clay outcrops.
Medium-size canyons (8 to 18 km length, 320 to 520 m relief) and small canyons
(2.5 to 5 km length, 200 to 300 m relief) exhibit proportionally less textural
variability and lower energy levels. The smallest canyons are broad
embayments of the shelf edge, and sediment texture is similar to the
homogeneous silty sand that covers the upper slope. Source areas of sediment
for the canyons are the continental shelf and bioerodable Pleistocene silt and
clay that veneers canyon walls.

Erosional processes on the bank margin include (a) sand transport from
the shelf edge and canyon rims to the upper slope and canyon walls,
respectively; (b) winnowing of fine sediment from sand on the upper slope in
the 200 to 300 m depth interval; (c) bioerosion of Pleistocene silt and clay

- 95 -

outcrops on canyon walls; and (d) winnowing and re-suspension of fine sediment
from sand, silt, and clay deposited on canyon floors.

Deposition of sediment occurs as follows: (a) sand, silt, and clay on
the upper slope below 300 m; (b) fine sediment around canyon heads; (c) sand
(containing little fine sediment) on the floors of large canyons; and (d)
sand, silt, and clay on the floors of medium and small canyons.

The physical environment of the canyon is reflected in the fauna. The
largest canyons contain the most heterogenous bottom (habitat) types, and the
epibenthic fauna there exhibits the highest diversity and greatest biomass.
Medium canyons are less diverse, and the fauna of the smallest canyons
resembles that of the upper slope due to the absence of hard substrate for
attached organisms. However, at deeper depths, these smaller canyons may
support high concentrations of "canyon indicator" taxa. This is true, for
example, in Heezen Canyon off Georges Bank and Hendrickson Canyon off New
Jersey.

Sediment Resuspension and Potential for Pollutant Transport on Particles

The processes of sediment resuspension are more frequent and much more
intense in the axes of Lydonia and Oceanographer Canyons than on the adjacent
continental shelf, or at comparable depths of the continental slope. Sediment
traps placed 5 m above the bottom in the canyon axis collected about 8 and 60
times more sediment than on the continental shelf and slope, respectively.
This greater resuspension activity in canyons increases the opportunity for
particles to adsorb and transport dissolved contaminants from the water column
to the bottom sediment. Measurements of lead-210 and plutonium-239/-240
distributions in sediment cores from the axis of Lydonia Canyon and from the
open continental slope (both locations at the 630-m water depth) support this
hypothesis. The behavior of these isotopes in the marine environment, by
virtue of their affinity for particulates, is analogous to the behavior of
many contaminants. Both isotopes have inventories (disintegrations per minute
per cm*) that are 2.5 times higher in the canyon axis than on the slope.

=06,-

Specific activities (dpm/g) are also much greater in the canyon axis,
indicating that enhanced scavenging rather than preferential deposition of
particles containing these isotopes accounts for these differences. The
greater inventories of isotopes found in Lydonia Canyon suggest that this
environment has a greater potential for scavenging dissolved contaminants than
noncanyon areas.

Canyon Fisheries

Several commercial species (lobster, Jonah crab, red crab, witch
flounder, four-spot flounder, white hake, squirrel hake, ocean pout, and
tilefish) are found in high abundance in the heads of submarine canyons, due
in part to the wide variety of low relief, three-dimensional habitats.

Fishing methods directed toward these species include traps and long- line
(baited hooks) gear. Mobile gear (trawls, dredges) is not used in the
canyons, so there is no physical damage to the habitats as has occurred in
historic fishing areas on the shelf and slope. Submarine canyons therefore
function as refuges ("home territory") for a number of commercial species and
their food organisms. All of these species are mobile and, with the exception
of tilefish which are very faithful (endemic) to a given tunnel or grotto
shelter, are likely to move out of the canyon head or along the rim or wall if
subjected to any stress. The most mobile (migratory) of these species, the
lobster, is known to undergo extensive seasonal migrations inshore, offshore,
and along the shelf. Approximately 75 percent of the offshore lobster catch
and 95 percent of the tilefish catch emanates from the submarine canyon
populations.

POSSIBLE IMPACTS
As in the previous section, information capsules are presented for topics

that are likely to be considered in relation to environmental impacts of
petroleum activities.

2AG7 =

Estimating Impacts

One approach to estimating how much of an impact oil and gas activities
could have is to make a simple calculation (following an earlier suggestion to
consider worst-case scenarios). To do so, we assume a reasonable discharge of
contaminants that are transported into a small area at the canyon head or
axis. The accumulation is then assumed to be evenly distributed into a thin
layer of surface sediment and the resulting concentration is compared with
background concentrations.

We assumed the contaminants would not settle disproportionately near the
drill site, but would be spread evenly throughout the 1 km*. We also assumed
that the materials would be mixed into a l-cm thick surface area. (Biological
mixing of materials within sediments is often deeper than this, and in regions
of high current velocities, physical processes can mix sediments deeper than 1
cm.

All three assumptions (area covered, depth of mixing, and amount
transported) yield a worse-case result--because the area covered and depth of
mixing is less then actually expected, and the amount transported is greater
than actually expected.

Based on these worst-case assumptions, however, we can consider the
potential elevation of the metal chromium present in drilling mud at a
concentration of 200 mg/kg. If we assume a total discharge of 1 million kg of
drilling mud/well, evenly distributed over 1 square km of canyon floor, and
mixed to a depth of 1 cm, that would add 20 ppm to the chromium content of the
top centimeter of sediment. Background values average 45 ppm (ranging from 35
to 80 ppm) in Lydonia Canyon, so the increase is on the order of 45 percent.
However, this increase assumes that all of the drilling mud reaches the
canyon, and all of it is deposited in 1 square kilometer. For perspective,
consider that the world average chromium concentration in crustal rocks is 100

ppm.

- 98 -

The same hypothetical worst-case scenario can be used to estimate the
potential changes to the physical nature of the sediments. The deposition of
this drilling mud would contribute at most 10 percent to the mass of natural
sediment in the upper 1 cm over the 1 square km area. Barium sulfate, the
only component of drilling mud with significantly higher density than natural
sediment, represents a variable fraction (one half to two thirds) of the total
drilling mud by weight.

Generally, deposition of particulates from drilling muds beyond the
wellsite should be at a relatively low rate: 0.1 cm/yr, compared with 0.06
cm/yr for natural deposition (also a low rate, based on measurements near the
canyon head).” Such deposits are unlikely to threaten megafauna, including
commercial fish and invertebrate species, except possibly in their early life
stages. At the expected low rate of deposition, material derived from
drilling muds should be quite thoroughly mixed into natural sediments by
physical and biological processes. Moreover, depositions from the drilling
mud represent only a fraction of total depositions from all sources in a
highly active environment. Thus the physical effects on the substrate beyond

500 m should be quite small.

Because, at least in some canyons, some turbulence and resuspension
occurs normally, some or most canyon fauna are not particularly sensitive to
sediment in the water. Therefore, the principal effect of the drilling muds
on the biota, beyond the near-field blanketing of the bottom, is likely to be
chemical. Although chemical constituents of drilling muds may not cause
direct mortality, there may nevertheless be an effect upon sensitive
organisms. Chemical cues may affect larval settlement or behavior and hence
recruitment.

"See also reviewer comment in Appendix A.

- 99 -

Life Stages and Sensitivity

Larvae are more sensitive than adults to contaminants and early juvenile
stages are particularly sensitive to physical disruption. Inhibition of
larval settlement on sediments whose attractiveness is affected by
contaminants could result in reduced recruitment of commercial species. Any
disturbance that drives juveniles from their nursery habitat will expose them

to more predation.
Drilling Muds

Assuming a wellsite 1 km from a canyon rim, the available information
suggests that very little biological impact due to drilling can be expected
within the canyon. The main concern during the exploration phase is drill
muds and cuttings, most of which would initially accumulate within 200 m of
the platform.” Some quantities can be expected to drift into the canyon,
especially if it is downcurrent from the platform. However, there is little
or no chance of burial of organisms or of chemical contamination of the
sediments, much less bioaccumulation of harmful materials at distances greater
than a few hundred meters from the wellsite. The metals found in drilling
muds are virtually all insoluble, and thus not available to animals.
Furthermore, barium, the most plentiful metal in drilling muds, is not toxic
to marine organisms when present as barium sulfate. In general, drilling-mud
metals are present in chemical forms that limit their bioavailability to
marine organisms.

Produced Water
Produced water is usually a saline brine with constituents similar to

those in seawater, as well as some hydrocarbons (including aromatics) and
metals. The metals may be concentrated up to three orders of magnitude above

“See also reviewer comment in Appendix A.

= 100%

seawater levels but all the constituents of produced water are diluted very
rapidly and would pose no problem in a canyon 1 km from the source. Even in a
worst-case situation in shallow water in the Gulf of Mexico over a period of
several years there is very little evidence of any effect of hydrocarbons from
normal drilling and production operations. The same is true of
radionuclides--there is some radium (radium-226 and -224) in produced water,
but there is little signal beyond the immediate discharge site.
Bioaccumulation of radium is possible, but there is no evidence to date
suggesting that it has occurred.

Amounts of produced water are highly variable; the average per platform
in the Gulf of Mexico is around 2,000 bbl/day. Volume increases with the age
of the well. There is little produced water associated with gas production.

A calculation illustrates the small effect of the produced water. At 50 ppm X
2,000 bbls/day, 16 L of oil and grease are discharged daily in the produced

water.
Physical Obstructions

Anchors could be used to secure a semi-submersible drilling platform
during exploration; for production, bottom-mounted rigs with no anchors would
be used. Anchors could extend radially up to 1 mi from the platform, but
there would be no need to locate one close to a canyon rim. Anchor impact on
the bottom is small. It was estimated that even if full production were to
take place on Georges Bank there would be no more than 30 platforms’ --the
number in the much more productive North Sea. Current shear like that found
at the shelf edge, even with warm-core rings, would not present an engineering
problem for drilling given the expected water depths.

“See also reviewer comment in Appendix A.

- 101 -

Blowouts

Environmental impact due to accidental blowout is predominately a problem
only on the surface, where the impact would depend on timing and presence of

fish eggs and larvae.

Gas Blowouts

There are few studies of gas blowouts reported. There has been one
report for a gas blowout in the North Sea, and perhaps two studies of gas
blowouts in Canadian waters--one in the Arctic and the other in the Canadian
Atlantic.

Most of the gas blowouts occur on the platform itself, so there is a
combination of sand, rocks, gas, and water blown into the air. Very few of
the situations actually happen subsurface, so high volumes of gas are not
generally injected directly into the water. The exception may be with
shallow-water gas blowouts, where there are ruptures outside the casing. The
gas is volatile and would disappear quickly.

Hydrocarbons

Increased particulates scavenge hydrocarbons from the water column during
spring bloom conditions. The settlement of this material to the bottom could
produce impacts. From this source, a gradual increase in hydrocarbon
accumulations in surficial sediments from produced water are likely to be
undetected, and because the rate is low, it may be substantially offset by
breakdown processes. However, net hydrocarbon accumulations, if they occur,
would likely be due mostly to other sources, such as accidental spills from
ships, etc.

= 102 =

CONCLUSIONS

After nearly two full days of reviewing the scientific facts, as recorded
in this report, a workshop consensus was reached on several findings and

recommendations.

= No rig should be closer than 500 m to the boundary of a canyon, as
defined by NOAA, because:*

1. It would prevent disturbance to the boulder fields and "pueblo
villages" that are important nursery areas.

2. It would exclude accumulation in the canyon of any rapidly
settling material (cuttings, a major fraction of the drilling

muds, and debris dropped off the rig);

3. Direct burial and smothering of organisms in the canyon would be
avoided;

4. There would be greater opportunity for increased dilution of
waterborne contaminants; and

5. This setback would appear to have little impact on the feasibility
of exploration or production drilling.

ws Dilution of metals in the water column indicates that they are
unlikely to cause biological problems, although some increases might

be measurable.”

= Barium accumulation is expected, but because of its low toxicity,” it
is unlikely to have a measurable biological effect.

“See also reviewer comments in Appendix A.

- 103 -

= It is unlikely that settlement of fine material from drilling would
alter the physical characteristics of the canyon sediment enough to
preclude settlement by larvae of benthic organisms.” This
conclusion was based on a worst-case order-of-magnitude calculation
similar to that for the metals.

mw Given a 500-m setback, it is unlikely that drilling muds and cuttings
would produce any measurable effects on the commercial species in the
heads of canyons.

w Given the low volume and high dilution, deck drainage and sewage
discharges are minor contaminants, and therefore are expected to have
no measurable input--compared to other discharges.

= Produced water must meet the current Environmental Protection Agency
discharge standard, presently no more than 48 mg/L (ppm) of oil and
grease.

ws Information on the concentrations of hydrocarbons and metals in
produced waters suggest no effects are expected in the water column.
Benthic effects are not expected but gradual accumulation of
hydrocarbons on the bottom has been shown in shallow water. If
production were to occur without further study of this benthic
hydrocarbon accumulation, discharge of produced water should be
monitored. It is more likely that hydrocarbon buildup would be
related to spills and blowouts.

a During oil spills and blowouts, there is a possibility of higher
accumulations of hydrocarbon in canyons than on the adjacent slope
(for example, in krill, or due to sedimentation and resuspension
processes).” However, the major short-term impacts would occur in the
surface layer and at the shelf water/slope water front. Benthic

“See also reviewer comments in Appendix A.

- 104 -

impacts, if they occur, are likely to be the result of oi] adsorbed on
the particles accumulating on the bottom over a long period of time.

Major short-term impacts will occur in the sea-surface layer,
especially at the shelf water/slope water front.

For major short-term impacts, planktonic eggs and larvae of
canyon fauna, especially commercial species, would be most vulnerable;
however, the magnitude of the impact is too dependent on a specific
situation to quantify.

a Insufficient information exists to evaluate the possibility of impacts
from gas blowouts.”

mw Canyons represent a large fraction of the fishing grounds for some
species. The 500-m setback should minimize a portion of this space
conflict. Anchor lines could occupy a large fraction of the preferred
fishing area near a canyon; however, some accommodation could be
achieved by industry-to-industry cooperation.

"See also reviewer comments in Appendix A.

- 105 -

RESEARCH NEEDS

= Data on the vertical particle flux, sediment transport, and rates of
sediment accumulation (processes that influence the fate and effects
of contaminants) are needed in the canyons of the North Atlantic area.
The lack of this basic information inhibits our ability to make
definitive conclusions.

= More information is needed to specify which canyons have fisheries or
other special biological characteristics, and which do not.

mw Sedimentological, geochemical, and physical oceanographic information
is only available for one or two canyons, primarily on the canyon
heads. Hypotheses based on this limited data have been proposed to
explain environmental processes and patterns in the canyons.
Comprehensive studies in a variety of canyon types would improve the
ability to predict potential impacts on canyon biota.

ws If drilling activity is to occur close to a boundary of a submarine

canyon in the mid- or North Atlantic areas, the processes associated
with potential impacts should be studied.

- 106 =

APPENDIX A

COMMENTS SUBMITTED BY WORKSHOP PARTICIPANTS BASED
ON REVIEW OF THE FINAL SUMMARY REPORT

These comments are appended separately rather than incorporated into the body
of the report as they reflect individual input and not necessarily a workshop

consensus.
Page Reviewer
79 James Ray
80 James Ray
87 James Ray
89 James Ray

Comment

Although the workshop focuses on the shallower
parts of canyons because of the amount of
oceanographic information available, the
discussions of probable impacts were a little
broader.

There was a specific point made that many of the
smaller "canyons" weren’t really canyons, but
small embayments of the shelf. This delineation
is important with regards to the number of areas
that people perceive as truly unique canyons.

This [regarding statement on potential for
contaminant accumulation in canyons with fine-
grained sediments] is a little misleading. To
say that this is an accumulation zone is
questionable, especially with deposition of all
similar size particles from shelf and slope co-
depositing. The "scavenging" theory is based on
limited data. There is virtually no data to
support the suggestion that ionic species of
contaminants above background levels would be
drifting in the water mass at any significant
distance downstream from a platform. The
possibilities of this being a mechanism for
concentrating rig pollutants in a canyon seems
questionable based on the present information.

[Regarding contaminant concentration by filter
feeders.] The concept of "contaminant
concentration" by coelenterates, e.g., corals
and gorgonians, is much different than the
accumulation process in bivalve mollusks, which
are for the most part missing in the canyons.
[There is some question about] the above theory,
and [there may not be] any data to support it.
I believe it is a nonmechanism for canyon
concentration of contaminants. [Pages 218 and
219 of the verbatim transcript for February 8,
1989 address this topic.--Ed.]

A-1

ei)

99

100

101

Reviewer

Pat Hughes

Page Valentine

Robert Ayers and
Nancy Maciolek

Robert Ayers

James Ray

Comment

[Disagrees with Cooper’s statement about
commercial species’ ability to recover
relatively quickly due in part to growth to
maturity at a young age]...lobsters take 6 1/2
to 7 years before they are sexually mature.

[Disagrees with Cooper’s statement that 20
percent of the upper continental slope off
Georges Bank is occupied by submarine
canyons]...no data to back up this statement.

[Both reviewers questioned the 0.1 cm/yr
deposition of particles from drilling mudsbeyond
the wellsite compared to 0.06 cm/yr for material
deposition--either the actual values or the
ratio caused question.] In addition, in the
Toms Canyon study (in the mid-Atlantic), Ayers
reports that sedimentation rates from drilling
mud varied from as high as 10 percent of the
natural sedimentation rate 1,500 m from the
wellsite (20-m depth) to about 0.1 percent of
the natural sedimentation rate in the canyon, 7
km from the wellsite (540-m depth).

[Drilling muds and cuttings] produce no water
column impact. They can cause a temporary
decrease in abundance levels of immobile
macrobenthos in the immediate vicinity (about
200 m) of the wellsite. There is usually no
change in diversity. Also, there is usually no
detectable impact in high-energy environments.

[Questions the accuracy of the statement,
"...even if full production were to take place
on Georges Bank, there would be no more than 30
platforms--the number in the much more
productive North Sea."] [page 266 of the
verbatim transcript for February 8, 1989 states
that because of the large number of wells able
to be drilled from one platform, the number of
platforms used would be smaller--and that the
number of platforms in the North Sea was thought
to be about 20, rather than 30--Ed.]

A-2

Page

103

103

103

103

Reviewer

Pat Hughes

Brad Butman

Robert Ayers

Brad Butman

Comment

[Suggests expansion of statement on the 500-m
setback] No drilling should occur within the
heads of submarine canyons nor within 500 m of
the boundary of a canyon....This statement
should include a list of the special features of
the canyons that have led this group to
recommend that drilling be prohibited within

500 m:

1. Canyons are complex environments,

ae Species diversity and abundance are
greater in canyons than on the adjacent
slope,

Se Canyons do trap sediments from the

adjacent shelf, and

4. Active resuspension of sediments in
canyons results in a higher potential for
the adsorption and removal of sediment-
reactive pollutants.

[Questions the recommended 500-m setback for
rigs, and suggests]...a larger distance to meet
the objectives listed. Especially around
Lydonia Canyon, the depositional region extends
several km onto the shelf around the rim.

[Suggests expansion of the statement regarding
dilution of metals in the water column.
Additions or modifications are underlined. ]
...dilution and settling of metals (they are
essentially 100 percent in particulate form or
adsorbed on particulates) indicates that they
are not a biological problem. [Suggests
deletion of the phrase]..."although some
increases might be measurable." [Adds] They are
also unlikely to be a significant problem in the
canyon sediments.

[While it is true that because of] dilution,
metals are unlikely to be a problem, the report
should explicitly state that exploratory
drilling would probably not present a problem.
The simple calculations assume one well is
drilled, potentially increasing the chromium
concentration 20 ppm in a region where the
background is about 50 ppm. Thus, while one

A-3

103

103

104

104

105

Reviewer

James Ray

Brad Butman

Pat Hughes

Page Valentine

James Ray

Comment

well may not be a problem, if 25 to 50 wells are
drilled from one platform, the metals could be a
problem.

[Questions use of description "low-toxicity" for
barium, since elsewhere in the workshop, barium
has been described as nontoxic. ]

[Comments on the effects of barium] Although
the concentrations from one well may be low,
multiple wells may provide significant
concentrations in confined areas. Although
apparently nontoxic, the physical effects of
barium (it is heavier and finer than the natural
sediments) may influence the benthic communities
in subtle ways. For example, in the MMS-
supported California Area Monitoring Program
(CAMP), careful laboratory experiments have
shown that feeding rates (as indicated by fecal-
pellet production) of polychete worms
(Mediomastus ambeseta) decreased with barium
concentrations on the order of 0.1 to 1 percent.
(Personal communication, Dr. Cheryl Ann Butman,
Woods Hole Oceanographic Institution, Woods
Hole, MA). More details of the barium
calculations should be presented (volume, area
of distribution, mixing depth, number of wells,
etc.).

[Expands on statement that settlement of fine
material from drilling would be unlikely to
alter physical characteristics of canyon
sediment so as to preclude larval settlement of
benthic organisms. Points out that the data
are]...inconclusive as to the potential risk of
chemical impacts to larval settling, etc.

[Suggests that the role of krill in possible
hydrocarbon accumulation in canyons is through
fecal pellets, recalling the workshop statement
that "the feeding activity of krill in surface
waters results in the production of rapidly
settling large fecal aggregates."]

Because of the nature of gas blowouts, it is

very unlikely that there would be significant
environmental [effects].

A-4

Comment

Page Reviewer
105 Robert Ayers [Suggests modification to the statement on gas

blowouts--modifications and additions are
underlined] Less information exists on possible

impacts from gas blowouts. However, since the

hydrocarbon gases rise into the atmosphere

rather than remain in the water column or

settle, it appears that impacts would be
significantly less than if crude oil were
spilled.

A-5

APPENDIX B

ABSTRACTS

Bei

PRE AND POST DRILLING BENCHMARKS AND MONITORING DATA OF
OCEAN FLOOR FAUNA, HABITATS, AND CONTAMINANT LOADS IN THE
GEORGES BANK SUBMARINE CANYONS

Dr. Richard A. Cooper
Professor of Marine Sciences
Director, National Undersea Research Center,
University of Connecticut at Avery Point,
Groton, CT 06340

ABSTRACT

The biology and geology of submarine canyons of the
northwest Atlantic was investigated by diver scientists,
using manned submersibles, from 1973 through 1984. This
effort entailed in-situ studies in eighteen canyons ranging
from Corsair, Georges, Nygren, Powell, Lydonia, Gilbert
Oceanographer, Filebottom, Hydrographer, and Veatch off
Georges Bank to Atlantis, Block, Hudson, Toms, Wilmington,
Baltimore, Washington and Norfolk off southern New England
and the Mid Atlantic Bight. From 1980 through 1984
scientists from several New England research institutions
(NMFS, USGS, and NURC) conducted a before, during, and post-
drilling study of the species abundance, community
structure, animal-substrate relationships and body-
substrate burdens of trace metals, PCB's, and hydrocarbons
within and downstream of oil and gas exploration areas on
the south central portion of Georges Bank. There was no
evidence of impact from drilling on the megabenthic fauna
and the quality of their ocean floor habitats within the
Georges Bank Canyons (Lydonia, Oceanographer, and Veatch).
The five-year "benchmark" and monitoring study, conducted
from the research submersible Johnson-Sea-Link, was
supported by NOAA's Office of Undersea Research (OUR) and
the National Marine Fisheries Service, Woods Hole, MA.

Site specific stations were established in Lydonia
Canyon (head of canyon and west wall) in 1980 and in
Oceanographer and Veatch Canyons in 1981 and 1982. Photo
and video transects were made in July, along transects
oriented north, south, east, and west of the station marker.

Estimates of species abundance and community structure were
made by habitat type.

We hypothesize that submarine canyons function as
refugia for many bottom-oriented species, where there is
little, if any, impact from active fishing gear. Species
diversity and abundance are greater in canyons than in non-
Canyon areas at comparable depths. Canyons also function as
important nursery grounds for a wide variety of megabenthic
fauna such as shrimps, Cancer crabs, American lobster, white
hake, cusk, ocean pout, conger eel, tilefish, and black-
bellied rosefish etc., and provide three-dimensional

B-2

shelter, rarely occurring in noncanyon areas of the outer
shelf and upper slope, for the adults of some 20 species.
Our combined canyon studies show that these large geologic
features represent unique ecosytems, largely because of
their highly varied, three dimensional habitats.

Examination of the benchmark data on annual variations
in species abundance, specifically for the fourteen
designated key "indicator species," suggests that no one
species is likely to clearly reflect anything other than a
major impact from production drilling. We suggest that
community composition be examined by habitat type and
specific location for defining faunal benchmarks in terms of
future oil and gas explorations.

Surficial sediments at each benchmark station were
analyzed for trace metals (Ba, Cd, Cu, Cr, Hg, Pb, and Zn),
hydrocarbons (aromatic and aliphatic), and PCB's. Scallops
(muscle and viscera), cancer crabs (hepatopancreas and claw
tissue), lobsters (hepatopancreas, claw/tail tissue, and
eggs), and tilefish (dorsal musculature) were subjected to
the same analyses. Sediment and animal bound PCBs were
below the levels of detection (0.005 ppm) prior to
drilling; subsequent analyses were not made. Concentrations
of petrogenic hydrocarbons (FI, FII) were all non detectable
prior to and after drilling. Trace metal concentrations in
the surficial sediments and in crabs and lobsters remained
relatively constant over time.

Since no impacts were identified with regard to

exploratory drilling, this 5-year data base is considered an
appropriate "benchmark" for future drilling operations.

B=3

THE LYDONIA CANYON EXPERIMENT:
CIRCULATION, HYDROGRAPHY, AND SEDIMENT TRANSPORT

by
Bradford Butman

U.S. Geological Survey
Branch of Atlantic Marine Geology
Woods Hole, MA 02543

A field program was conducted to study the circulation and sediment -
dynamics in Lydonia canyon, located on the southern flank of Georges Bank,
and on the adjacent continental shelf and slope. The program included (1)
insitu measurements by an array of moored current meters, bottom tripods,
and sediment traps maintained between November 1980 and November 1982; (2)
synoptic observations of the hydrography and suspended sediments; (3)
sidescan-sonar and high-resolution seismic reflection surveys; (4) samples
of the surficial sediments; and (5) direct observations of the sea floor
from the submersible ALVIN.

The distribution of surficial sediment and the high-resolution
seismic reflection data suggest that very fine sand and silts and clays
accumulate in the head of the canyon and on an area of the shelf adjacent
to the canyon. However, the current measurements show that the surficial
sediments are reworked and resuspended along the canyon axis to a water
depth of at least 600 mn. Thus, although fine sediments may be
accumulating, the axis is not tranquil. Maximum hour-averaged current
speeds 5 meters above bottom (mab) were greater than 60 cm/s at about 300
and 600 m in the canyon axis. No evidence of sediment movement was
observed at 1,380 m. The current observations suggest down-canyon
transport of sediment along the axis near the head at a water depth of
about 300 m and up-canyon transport at about 600 m, implying a convergence
in the transport of sand as bedload toward the head. Qualitatively, the
sediment distribution along the axis mirrors the strength of the near-
bottom currents (finer sediments in areas of weaker currents).

The mean Eulerian (measured at a fixed point) current was
southwestward on the shelf adjacent to Lydonia Canyon and above the level
of the canyon rim which is consistent with previous studies of the mean
circulation on Georges Bank. On the continental slope, the mean flow was
strongly influenced by Gulf Stream warm core rings. Several rings passed
to the south of Lydonia Canyon during the observation period; the strong
clockwise flow around them caused eastward flow along the edge of the
shelf as strong as 80 cm/s. On the slope, the influence of the rings in
the water column extended to at least 250 m, but not to 500 m. The
influence of the rings did not extend onto the Continental Shelf to water
depths of 125 m. Over the slope, there was a persistent off-shelf and
downslope component of flow near the bottom of a few centimeters per
second. There is some evidence that the warm core rings affect flow in
the canyon by generating packets of high-frequency current fluctuations.

Within the canyon, the mean Eulerian flow near the bottom was
complex. Near the head of the canyon, net Eulerian flow 5 mab was down-
canyon, at about 3 cm/s, and weak at 50 mab. At 550 m, the near-bottom
flow was up-canyon. At 600 m the near-bottom flow was weak; the flow 100

B-4

mab was up-canyon. These observations suggest a convergence of the mean
Eulerian flow between 300 and 600 m and possibly several cells of
recirculation along the canyon axis. However, because of the energetic,
non-linear, high-frequency motion observed in the canyon and the small
spatial scales, the mean Eulerian current may not indicate the actual
Lagrangian water-particle motion. Further analysis is required to
determine the Lagrangian circulation pattern. Measurements made on the
eastern rim of the canyon at about 200 m show westward flow directly
across the canyon axis. Measurements on the eastern wall of the canyon,
just a few km away at comparable depths, show northward inflow along the
eastern wall. Measurements on the western wall show southward outflow.
The mean Eulerian currents in the canyon thus suggest a complex vertical
Eulerian circulation along the axis and horizontal exchange along the
canyon walls.

The current fluctuations within the canyon are aligned with the
canyon axis. The strength of the high-frequency fluctuations (motions
with periods shorter than about one day) increase toward the bottom and
the head of the canyon. The low-frequency currents (motions which
fluctuate at periods longer than about 2 days) were strongest over the
slope and weakest in the canyon. Alongshelf current fluctuations over the
shelf were correlated with cross-shelf flow over the canyon mouth
(offshelf for southwestward flow), suggesting enhanced cross-shelf
exchange in the region of the canyon. The fluctuations at semidiurnal
periods dominate the current spectra; near the canyon head their strength
changes substantially with time, indicating random generation of internal
wave packets.

Similar studies in nearby Oceanographer Canyon show that the currents
are dominated by the tidal currents and are stronger than in Lydonia. Net
Eulerian down-canyon flow was observed at both 200 and 600 m.

Ba5

SEDIMENTARY ENVIRONMENTS IN SUBMARINE CANYONS AND
ON THE OUTER SHELF-UPPER SLOPE OF GEORGES BANK

Page C. Valentine
U.S. Geological Survey
Woods Hole, MA 02543

Sedimentary environments have been identified on the southern margin
of Georges Bank at depths of 150-600 m on the basis of texture and
bottom current patterns. At the shelf edge, rippled sand gives way to
smoother and finer-grained sand deposits as water depth increases on the
upper slope, which is dissected by steep-walled gullies. Submarine
canyons of varying size and wall steepness incise the Georges Bank Shelf
and contain such sedimentary facies as pavements of ice-rafted gravel,
bioeroded and collapsed Pleistocene silt outcrops, sand accumulations

surfaced with large and small bedforms, and almost featureless silty
sand.

Patterns of strong bottom currents are attributed to Gulf Stream
warm-core rings, tidal currents, and an unknown source. (1) Gulf Stream
warm-core-ring currents flow northeastward at about 50 cm/s, winnowing
very fine sand, silt, and clay from the upper slope between 200 and 300
m water depth. (2) Regional tidal currents are weak on the upper slope.
However, canyon morphology appears to affect tidal flow. At depths of
150 to 600 m in large canyons having steep walls (Oceanographer Canyon),
tidal currents are strong, attaining speeds of 75 to 100 cm/s. The
canyon floor is covered by coarse sediment and large bed forms. By
contrast, small, shallow canyons (Heel Tapper Canyon) are relatively
tranquil, and, like the upper slope, canyon walls and floors are covered
by silty sand. (3) A strong bottom current of unknown origin flows
westward at about 50 cm/s across the rims of Oceanographer and Lydonia
Canyons at depths of 150 to 200 m, transporting shelf sand across
deposits of ice-rafted gravel onto the east canyon walls.

Sediment movement is more rapid in a narrow band northeastward along
the upper slope, along the lower walls and floors of large, high-energy
canyons, and from the shelf westward across the east rims of large and
medium canyons. Sediment movement is less rapid on the outer shelf, on
most of the upper slope, including the gullies, on the floors of medium
and small canyons, and around some canyon heads. A moderately energetic
canyon of medium size such as Lydonia may be accumulating sediment most
rapidly. It traps a large volume of shelf sand as well as bioeroded
silt from outcrops on lower canyon walls.

B-6

TOMS CANYON STUDY
R. C. AYERS, JR. AND J. E,. O'REILLY
EXXON PRODUCTION RESEARCH COMPANY

DURING THE PERIOD 1978-81 EXPLORATORY DRILLING ACTIVITY ON THE
MID*ATLANTIC OCS WAS AT ITS PEAK. ALSO, DURING THIS PERIOD,
ENVIRONMENTAL CONCERN OVER THE IMPACT OF DRILLING IN THIS
FRONTIER AREA WAS QUITE HICH. TO ADDRESS ‘THE ENVIRONMENTAL
ISSUES, GOVERNMENT MANDATED STUDIES ON DRILLING DISCHARGE IMPACTS
WERE CONDUCTED BY INDUSTRY. THE TOMS CANYON STUDY WAS ONE OF
THESE. THE WELLSITE IN BLOCK 816, LOCATED APPROXIMATELY 150 kn
FROM THE NEW JERSEY COAST, WAS ALSO LOCATED APPROXIMATELY 3.7 kn
NORTH EAST AND UPCURRENT OF TOMS CANYON. THE MID-ATLANTIC
BIOLOGICAL TASK FORCE RECOMMENDED TO USGS THAT THE LESSEE,EXXON
USA, BE REQUIRED TO PERFORM A MONITORING STUDY TO DETERMINE IF
DISCHARGES FROM THE WELL WERE ENTERING THE CANYON IN HARMFUL
QUANTITIES. EXXON USA AGREED TO FUND THE STUDY WHICH WAS CARRIED
OUT BY EG&G ENVIRONMENTAL CONSULTANTS UNDER THE DIRECTION OF
EXXON PRODUCTION RESEARCH COMPANY.

THE MONITORING STUDY, CONDUCTED IN 1980-81, CONSISTED OF A
PRE-DRILLING, SEDIMENT SAMPLING SURVEY AND THREE DRILLING PHASE
SURVEYS. IT INCLUDED MEASUREMENTS OF CURRENTS, WATER PROPERTIES,
PHYSICAL AND CHEMICAL CHARACTERISTICS OF BOTTOM SEDIMENTS AND
MATERIAI, COLLECTED IN SEDIMENT TRAPS, A BATHYMETRIC SURVEY, AND
THE COMPOSITION AND QUANTITY OF DISCHARGED MATERIAL. BARIUM (FROM
BARITE) WAS USED AS A CONSERVATIVE TRACER OF THE DRILLING
DISCHARGES. IT WAS FOUND THAT ELEVATED BARIUM LEVELS COULD BE
DETECTED IN MATERIAL DEPOSITED IN SEDIMENT TRAPS AT THE RIM OF
THE CANYON. HOWEVER, THE DEPOSITION RATES FROM THB DISCHARGES
WERE TOO LOW TO MEASURABLY INCREASE CONCENTRATIONS OF BARIUM
IN SEDIMENTS LOCATED FURTHER THAN 1-1.5 km FROM THE WELLSITE.

B-7

RECENT DEVELOPMENTS IN
INDUSTRY SPONSORED RESEARCH

J.P. RAY
SHELL OIL COMPANY
HOUSTON, TX

This presentation will introduce and summanze several industry sponsored projects relating
to drilling fluids and cuttings that have been conducted over the past two years. Some of
this work has been submitted for journal publication, some will be relegated to the gray
literature.

Included in this summary are near and far-field rig monitoring programs conducted in the
Gulf of Mexico off Alabama and Texas. These include fate and effects monitoring relating
to both exploratory and development drilling. Sediment contamination (metals and
hydrocarbons) were considered in several of the studies in addition to benthic community
analysis. One location monitored exploratory discharges prior too, immediately after, and
one year post-drilling, in water depths of 10 m. Another assessed impacts due the discharges
from 10 wells into in a water depth of 28 m.

The industry, as part of their data gathering for comment submission on the proposed EPA
offshore effluent guidelines, have developed an extensive database on drilling mud
composition and acute toxicity from systems in field use for the past two years.
Generalizations regarding the general toxicity of field muds can be extracted from this
database and will be presented. This information is relevant to hazard assessment
considerations for the North and mid-Atlantic, and the related canyon areas.

A brief overview will be given of a major study conducted in California which quantified
sediment metals contamination, and their bioaccumulation and intra-cellular fate in three
different species of benthic infauna. Based on over 100,000 metals analyses, the data
suggests that barium is being accumulated as barium sulphate, and not the more soluble and
toxic barium ion. All sediment and faunal samples were taken from a discharge site in
water depths of > 70m.

Recent laboratory studies have explored the solubility and bioavailability of trace
contaminants, especially mercury and cadmium, from barite (the primary weighting agent used
in drilling muds). Because barite is the only mud component measurable in marine
sediments at distances beyond a few hundred meters, these studies have special relevance to
hazard assessments.

B-8

THE FLUX AND COMPOSITION OF RESUSPENDED SEDIMENT
IN TWO SUBMARINE CANYONS FROM THE WESTERN NORTH ATLANTIC:

IMPLICATIONS FOR POLLUTANT SCAVENGING

by

Michael H. Bothner
U.S. Geological Survey
Woods Hole, MA 02543

ABSTRACT

Sediment traps were used to estimate the flux of resuspended
sediments in Lydonia and Oceanographer Canyons and on the adjacent U.S.
North Atlantic continental shelf and slope. The axes of both canyons are
sites of much more resuspension activity than are areas of comparable
depth outside of the canyons. The highest resuspended flux (157 g/m? /day)
was measured in Lydonia Canyon axis 5 m off the bottom at 300-m water
depth. At the head of Lydonia Canyon, in water depths of 100 to 125 m,
the variability in the flux and texture of the trapped sediment correlates
with the timing and strength of major storms. Sediments trapped deeper
along the canyon axis show textural differences over time that are
similar to those observed at the head of the canyon, but the’ record is
more complicated. The greater variability in sediment textue at deep
sites suggests that additional processes, such as internal waves, cause
resuspension in the canyons.

The hypothesis that shelf-derived material is being transported into
Lydonia Canyon is supported by two recent data sets. First, the
concentration of barium, a major element in drilling mud, increased in the
resuspended sediment collected in Lydonia Canyon during the period in
which eight exploratory wells were drilled on Georges Bank. Second,
carbon-14 dating of piston cores from the head of Lydonia Canyon
indicates that sediment is accumulating at an average rate of 60 cm/1,000
yr. The core locations are down gradient and down current from the
southern flank of Georges Bank.

The more intense resuspension and higher accumulation rates in this
canyon, as compared to those on the adjacent continental slope, suggests
that the canyon sediments have a higher potential for the adsorption of
sediment-reactive pollutants. This hypothesis is based on _ the
observations that sediments in the canyon axis have higher specific
activities and higher inventories of lead-210 and plutonium-239, 240 than
sediments on the continental slope. In addition, concentration ratios
of Cd/Al, Cr/Al, Cu/Al, and Pb/Al are higher in surface sediments of the
axis of Lydonia Canyon than they are on the adjacent slope.

Frequent resuspension of fine-grained sediments in canyons
increases the opportunity for particulates to adsorb dissolved materials
and strip them from the water column. This process may make some canyons
a more effective sink for pollutants than the open slope.

B-9

OVERVIEW OF THE BIOGENIC AND ANTHROPOGENIC HYDROCARBON
DISTRIBUTIONS IN SEDIMENTS ALONG
THE NORTH ATLANTIC MARGIN

Paul D. Boehm
Technical Director

Battelle Ocean Sciences
Duxbury, MA

Georges Bank and the adjacent, slope, rise and submarine canyon areas are
characterized by highly dynamic sediment transport, deposition and
resuspension cycles. Pollutant and biogenic hydrocarbon distributions follow
the general trends of those for fine sediments. Saturated and polycyclic
aromatic hydrocarbons are found at very low levels in the central bank area
where sediments are coarse and are found at elevated levels in the
depositional areas of the "mud patch" , at canyon heads, and in fine grained
sediment areas further offshore.

Hydrocarbons of a biogenic, terrigenous nature appear to be in overal]
steady state, while marine biogenic hydrocarbon distributions are deposited
and then eroded from the surface sediments, eventually being deposited in
depositional areas to the southwest and west. Indirect evidence suggests that
anthropogenic hydrocarbons are associated with the easily resuspended fine
sediment fraction, while the biogenics associate with the coarser fractions.
It has been estimated that 40-50% of the organic matter is resuspended and
transported to the slope from the shelf.

Both the saturates and the PAH compounds are strongly associated with
total organic carbon in the sediments. Saturated hydrocarbons of a terrigenous
plant wax origin dominate the overall hydrocarbon assemblage. While the
absolute concentration of total hydrocarbons range from 0.2 to 20ppm, and PAH
compounds range from about 0.01 to 1.0 ppm, the respective ratios to TOC are
relatively constant, suggesting a well mixed geochemical area. The PAH/TOC
ratios are very similar to those found in sediments from other geographical
areas, well removed from the North Atlantic OCS. The PAH distributions are
similar to those originating in the combustion of fossil fuels, with
distributions dominated by the higher molecular weight PAH (i.e. 4- and 5-ring
compounds) rather than petroleum-sourced PAH.

The distributions of hydrocarbons in the shelf and slope areas have
important implications for predictions of the fate of pollutants which may
originate through outer continental shelf (OCS) development. Sedimented
hydrocarbons associated with fine grained sediments will be redistributed from
their point of origin rapidly (weeks to months) and will be transported to
depositional areas which include canyon heads, deeper slope areas and basins
such as the mud patch area. Data suggest that although introduced pollutants
may be deposited at these canyon heads and be transported down the canyons,
the data also suggest the possibility of up-canyon transport and deposition of
pollutants at canyon heads, as well.

POTENTIAL EFFECTS OF DRILLING EFFLUENTS
ON MARINE ORGANISMS
Jerry M. Neff
Battelle Ocean Sciences
Duxbury, Massachusetts 02332

During drilling and production from an offshore platform,
there are several possible discharges to the ocean and
physical alterations of the bottom that may have adverse
effects on the marine environment. Some discharges are
authorized by permit; others are accidental. The permitted
discharges of most environmental concern are drilling muds,
drill cuttings, and produced water. The most important
accidental discharge is petroleum through operational
spills or blowouts. Physical impacts may be caused by the
mere presence of the platform and by emplacement of
pipelines on the bottom. The focus of this talk will be on
impacts of drilling mud and cuttings discharges.

When discharged to the ocean, drilling muds and cuttings
are diluted very rapidly by dispersion and fractionation.
The heavier solids (representing about 90 percent of the
mass of the mud) settle rapidly to the bottom, usually
within 200 to 1000 meters of the rig, depending on water
current speed and water depth. The liquids, soluble
Materials, and fine clay-sized particles in the drilling
mud are carried away from the rig in a near-surface plume
and are diluted rapidly by mixing with seawater.

Because of the rapid dilution of drilling mud in surface
waters, significant biological impacts have not been
detected in the water column. However, drilling mud and
cuttings solids may cause adverse impacts in bottom living
(benthic) biological communities wherever the mud and
cuttings solids accumulate on the bottom. These impacts
could be due to physical burial, changes in sediment
texture making the habitat less suitable for some species,
or chemical toxicity of some drilling mud ingredients.

The ingredients in water-based drilling muds of greatest
environmental concern are metals. The metals most likely to
be present in drilling muds at concentrations significantly
higher than their concentrations in marine sediments are
barium, chromium, lead, and zinc. Minor ingredients
sometimes added to drilling muds that may contribute to its
impact include diesel fuel or mineral oil, surfactants, and
biocides. Many hundreds of acute toxicity bioassays have
been performed with water-based drilling muds. Nearly 90
percent of the samples were found to be non-toxic or
practically non-toxic to marine organisms.

Several large field studies have been performed in this
country and abroad by the oil industry and the government

(in the United States, usually the Minerals Management
Service of the Department of the Interior) around offshore
platforms. The objective of these monitoring programs was
to assess the impacts of drilling mud and cuttings
discharges on the benthic environment. Accumulation of
drill cuttings and of some drilling mud ingredients,
particularly barite, in sediments has been detected near
offshore exploratory rigs and production platforms. On
Georges Bank, elevated concentrations of barite derived
from drilling mud discharges were detected in sediments
near two exploratory rigs. The excess barite was washed out
of the sediments and diluted to background within one to
two years after cessation of drilling.

On the Mid-Atlantic outer continental shelf, but not on
Georges Bank, accumulation of drilling mud and cuttings
solids was accompanied by changes in benthic community
structure. Such benthic impacts, when they have been
detected, usually were restricted to a radius of about 200
meters from an exploratory rig from which only one well was
drilled. In the North Sea, impacts on the benthos around
multi-well development platforms sometimes extended out to
1000 to 3000 meters from the platform. Impacts were much
more severe if oil-based drilling muds were used and oily
cuttings were discharged (not permitted in U.S. waters)
than if water-based muds were used and discharged. Recovery
of benthic communities impacted by solids from water-based
drilling muds usually began within one or two years after
completion of drilling.

MEGAFAUNAL POPULATIONS IN LYDONIA CANYON, WITH NOTES ON THREE
OTHER NORTH ATLANTIC CANYONS

Barbara Hecker
Associate Research Scientist
Lamont Doherty Geological Observatory
Palisades, NY 10964

Megafaunal populations in Lydonia Canyon were photographically
surveyed during 16 camera sled tows and 17 ALVIN dives conducted between
May 1979 and September 1982. A total of 114,742 m2 of the seafloor, between
130 and 2330 m depth, was analyzed for this study. Lydonia Canyon is a
relatively narrow canyon that incises Georges Bank approximately 11 miles
north of the shelf-slope break. It has a narrow, sinuous sediment-covered
axis flanked by steep walls. The walls on both sides of the canyon exhibit
massive exposures of outcrop and steep, talus-strewn slopes.

Total megafaunal abundances in Lydonia Canyon are very high (up to
30 individuals per m2) at shallow depths, and intermediate at mid-slope (5

individuals per m2) and lower-slope (7 to 8 individuals per m2) depths.
Megafaunal distribution patterns within the canyon are complex and faunal
similarities among areas within a depth range are low. These low faunal
similarities reflect: patchy distributions of several of the dominant shallow
water taxa, substrate heterogeneity on the canyon walls, and differing
physical regimes in various parts of the canyon. The megafauna inhabiting
the axis and lower walls is usually dominated by filter-feeding corals and
sponges, and these taxa frequently comprise assembleges that are quite
distinct from those inhabiting the upper walls and the nearby slope.

Three other North Atlantic canyons (Oceanographer, Heezen, and
Corsair) were surveyed during 7 ALVIN dives conducted in September 1977.
Megafaunal populations differ substantially among the canyons, and between
the axis and wall within a canyon. While most of the taxa are widely
distributed, localized high abundances of individual taxa account for much of
the observed differences. This patchiness can only partialy be attributed to
differences in sustrate requirements, since several of the dominant taxa are
not restricted to hard substrate. However, as was the case in Lydonia
Canyon, the fauna in all three of these canyons is heavily dominated by
sessile filter feeders.

While these filter feeders require threshold currents and suspended
particles for their livelihood, they may also be susceptible to stresses
associated with increased sediment loads such as: tissue abrasion in regions
of strong current flow, clogging of filtering apparatuses in tranquil regions,
or decreased larval settling success. Additionally, concurrent physical studies
show enhanced current speeds and resuspension in the vicinity of canyons.
This indicates that the canyon system may well serve a role in transporting
and concentrating pollutants in the vicinity of these communities.

BENTHIC INFAUNA OF LYDONIA CANYON AND THE ADJACENT SLOPE ENVIRONMENT

Nancy J. Maciolek J. Frederick Grassle
Senior Research Scientist Senior Scientist
Battelle Ocean Sciences Woods Hole Oceanographic
Duxbury, MA 02332 Institution

Woods Hole, MA 02543

Among several stations sampled as part of programs funded by the
Minerals Management Service, stations were positioned at approximately
150, 550, and 2100 m in Lydonia Canyon and on the adjacent slope.

At 150 m, two stations were sampled inside the canyon and one on the
adjacent slope. Of the two canyon stations, one had silty sediments
and was dominated by the amphipod Ampelisca agassizi. The other
canyon station had coarser sediments and a much different suite of
dominant species. The slope station was also dominated by A.
agassizi, but a much higher percentage of the fauna at the slope
station (35%) than at the canyon station (12%) was accounted for by
this species. Of the next 19 dominant species, however, only two
occurred in common, indicating a major difference in faunal
composition between the slope and canyon station, even though both
were dominated by A. agassizi. Diversity was lower at both canyon
stations than at the slope station. Similarity analysis showed that
none of the three stations had a high level of similarity to any of
the other three, but each was most similar to other stations sampled
in the program. Subtle differences in sediment texture appear to
affect benthic community composition.

At 550 m, the top dominant at both stations was the polychaete Thayrx
annulosus, but this species accounted for 32% of the fauna at the
canyon station and only 6% of the fauna at the slope station. Of the
next 19 dominant species at the canyon station, five were also among
the top dominants at the corresponding slope station, but generally
ranked lower and did not dominate the slope community to the same
extent. Diversity was lower at the canyon station. The slope-
station fauna was more similar to the fauna at another slope station
more than 200 km distant (but also at 550 m) than it was to the
adjacent canyon station. Because sediment texture was similar at the
canyon and adjacent slope station, it is suggested that the current
regime at this depth controls the benthic community.

Maciolek and Grassle Page 2

Fewer faunal differences were evident at 2100 m, and these were not of
the same magnitude as those seen at shallower depths. The polychaete
Aurospio dibranchiata was the top dominant at both the canyon station
and two adjacent slope stations, where it accounted for 8 to 10% of the
total fauna. Of the next 19 dominant canyon species, 10 or 11 were
among the top dominants at the two slope stations, respectively. These
dominants often held similar ranks at the canyon and slope stations.
Unlike the situation at the shallower stations, diversity was higher at
the 2100-m canyon station than at either of the corresponding slope
stations. Sediment texture was similar at all three stations.

Infaunal biomass was measured on up to 12 sampling dates at the 150-m
stations and on one sampling date at the 2100-m stations. At both
depths, the mean biomass, reported as ash-free dry weight (AFDW), was
higher at the canyon station than at the slope station. Mean AFDW was
2.4 times higher at the 150-m canyon station and 2.0 times higher at
the 2100-m canyon station than at the corresponding slope stations.

DRILLING WAS PROHIBITED IN SUBMARINE CANYONS IN 1984
Patricia E. Hughes, OCS Coordinator
Massachusetts Coastal Zone Management Office

Research conducted along the North Atlantic continental shelf and slope
over the last fifteen years has contributed greatly to our understanding
of the physical, chemical, and biological processes of this region.
Research focused on the submarine canyons indicates that the processes
at work in them have created habitat that supports unique biological
communities in comparison with the adjacent shelf and slope environments.
Whether the canyons are erosional or depositional environments,

they support biological communities not found elsewhere.

The fundamental question underlying the two hypotheses being examined
at this workshop is: should oil and gas activities be permitted

in or adjacent to submarine canyons? In 1984, the Minerals Management
Service (MMS) answered this question by developing a lease stipulation
for proposed sale 82 that prohibited oi] and gas drilling activities
within 200 meters of the geographical boundaries of submarine canyons,
as defined by the National Oceanic and Atmospheric Administration.
Further, the lease stipulation included restrictions on drilling
activities within 4 miles of the submarine canyons.

It is assumed that this drilling prohibition was based on the scientific
community's current understanding of the canyons' oceanographic
processes and biological communities. This presentation will discuss
some of the factors believed to be important in the development

of this lease stipulation and relevant to the discussion of the
hypotheses.

NORTH ATLANTIC SUBMARINE CANYONS: MAINE’S PERSPECTIVE
Katrina Van Dusen

Maine State Planning Office

Maine has long been concerned about oil and gas
activity in canyon areas because of the unique and varied
habitats and diverse and abundant species found there.
These areas deserve special attention because they are a
nationally significant natural resource and because they
serve as nursery areas and refuge for commercially important
fish and shellfish. Qur concern has focussed on the
potential harm to these habitats that could be caused by
routine and accidental discharges from drilling activities,
as well as the bottom disturbance caused by the presence of
drilling rigs and the exclusion of fishermen from canyon
areas.

Maine’s interest in the canyons may not be as great as
in some of the other North Atlantic states because fewer of
our fishermen make the long trip to the southern edge of
Georges Bank. However, some of the species that spend part
of their lives in the canyons migrate inshore at other
times, especially lobsters, making the canyons important to
Maine fishermen even as they fish at a distance.

We are open to working together in this forum with the
hopes of acheiving some consensus on the viability of
drilling activity in and near submarine canyons. Prior to
Sale 82 we worked with the MMS on a canyon stipulation, an
indication of our openness to creative solutions. However, I
am very concerned about the scope of this workshop. The
workshop agenda appears to focus solely on “what happens" in
canyons with no time allocated for discussing whether what
happens is acceptable; the workshop hypotheses talk about
"low probability of serious environmental impact" and an
absence of "serious environmental risks." The stated
hypotheses can not be tested without consensus on what are
acceptable risks. Although this judgement can and should be
made with full consideration of the available scientific
information, it is ultimately a policy decision.

THE SUBMARINE CANYONS:
DRILL OR DEFER?
(A RHODE ISLAND PERSPECTIVE)
by
Bruce F. Vild, Principal Planner
Rhode Island Department of Administration, Division of Planning

The author has followed the Georges Bank/North Atlantic Planning Area
controversy for almost ten years, and has advised two Governors on the position
the State of Rhode Island should take on issues germane to offshore drilling
and habitat protection. A recurring problem, the author observes, is that
of allowing oil and gas companies the opportunity to drill in the North
Atlantic submarine canyons. Rhode Island traditionally has recommended
that canyon exploration for oil and gas be deferred. The author believes
that Rhode Island's position remains a sound judgment, in light of the findings
of environmental studies, and political realities. The data collected so
far do not lend themselves to hard-and-fast conclusions about the impacts
of drilling on canyon habitats, making prediction difficult. The commercial
fishing industry and environmental groups remain powerful constituencies.

The New England governors have no assurance that the oil and gas industry

is willing to invest heavily in the North Atlantic within the forseeable
future, so the benefits to our states from such activity are not forthcoming.
The problem of whether to allow drilling in the submarine canyons has many
facets other than science. In whatever solution becomes policy, the strongest
component is likely to be politics, not science.

APPENDIX C

MINERALS MANAGEMENT SERVICE

NORTH ATLANTIC SUBMARINE CANYONS WORKSHOP

PLENARY AGENDA

February 7, 1989:

8:00: a.m. cess Welcoming

Chairperson: Dr. Nancy Maciolek

$230 a.M..04-4 Pre and Post Drilling Bench
marks and Monitoring Data of
Ocean Floor Fauna, Habitats,
and Contaminant Loads in the
Georges Bank Submarine
Canyons

9500 -acMitas tc The Lydonia Canyon Experiment:
Circulation, Hydrography, and
Sediment Transport

9:30 a.m... Sedimentary Environments in
Submarine Canyons and on the
Outer Shelf-Upper Slope of
Georges Bank

10:00 a.m...<.. COFFEE BREAK
nO PO Fae Msace os Toms Canyon Study
OS4 5S ae Nese one Recent Developments in

Industry Sponsored Research

PLS Seae Moke ss The Flux and Composition of
Resuspended Sediment in Two
Submarine Canyons from the
Western North Atlantic:
Implications for Pollutant
Scavenging

Dr.
Mr.

Dr.

Dr.

Dr.

Dr.

Dr.

Dr.

*Actual presentation took place 8:15 a.m., February 8,

Cal

Don Aurand/
Jim Lane

Richard Cooper

Brad Butman

Page Valentine

Bob Ayers*

Jim Ray

Michael Bothner

1969)

11:45 a.m..... LUNCH BREAK

Chairperson: Dr. Page Valentine

1 00cpiM.c.26 Overview of the Biogenic and
Anthropogenic Hydrocarbon
Distributions in Sediments
Along the North Atlantic
Margin

1230" PeMe eo Potential Effects of Drilling
Effluents on Marine Organisms

22000 Delran: Megafaunal Populations in
Lydonia Canyon, with Notes
on Three Other North Atlantic
Canyons

2-30. Dele wens Benthic Infauna of Lydonia

Canyon and the Adjacent
Slope Environment

$250 PoMacenc COFFEE BREAK

Chairperson: Mr. Jim Lane

42007 D.Mys.c% Drilling was Prohibited in
Submarine Canyons in 1984

North Atlantic Submarine
Canyons:
Maine’s Perspective

The Submarine Canyons:

Drill or Defer?
A Rhode Island Perspective

C-2

Die

Dr.

Dr

Dr.
Dr.

Ms.

Ms.

Dr.

Paul Boehm

Jerry Neff

.Barbara Hecker

Nancy Maciolek/
Fred Grassle

Pat Hughes

Katrina VanDusen

Bruce Vild

MINERALS MANAGEMENT SERVICE
NORTH ATLANTIC SUBMARINE CANYONS WORKSHOP

AGENDA

ROUNDTABLE DISCUSSION
(All Panelists)

February 8, 1989:*

Chairperson: Dr. Don Aurand and Dr. Tom Ahlfeld
8:00 a.m. - 10:00 a.m.

Discussion of Hypothesis: "In submarine canyons of the North Atlantic
where erosional environments exist, there is a low probability of
serious environmental impact to faunal assemblages from oi] and gas
activities in the vicinity of canyonheads."

10:00 a.m..... COFFEE BREAK

10:15 a.m. - 12:00 noon

Discussion of Hypothesis: "In submarine canyons of the North Atlantic
Margin where depositional environments may exist, the rate of
accumulation of drilling related contaminants is slow enough not to
present serious environmental risks to faunal assemblages from oil and
gas activities in the vicinity of the canyonheads."

12:00 noon - 1:00 p.m. LUNCH BREAK
1300 p.m. - 5:00 pm.**
(3:00 p.m. - Coffee Break)

Chairperson: Dr. Brad Butman

PANEL A - Geology and Geochemistry of
North Atlantic Submarine Canyons

Panel Members: Dr. Brad Butman Dr. Paul Boehm
Dr. Page Valentine Dr. Bob Ayers
Dr. Mike Bothner Dr. Jerry Neff

Mr. Bruce Vild
*Discussions of hypotheses did not take place.

**Panels A and B met jointly during the morning. Preparation of the summary
synthesis and conclusions began in the afternoon.

G5

AGENDA

ROUNDTABLE DISCUSSION
(All Panelists)

February 8, 1989

In addition to the stated hypotheses discussed during the morning
session, the following topics are also suggested for related
discussions:

Effects of surficial sediment movement in canyons.

a
w Physical mixing processes in canyons.
ms Hydrocarbon and trace metal geochemistry processes in canyons.
w Habitat types and canyon morphologies.
ws Depositional versus erosional environments of canyons.
100° p.m. =" ~5:00 -pem. Chairperson: Dr. Fred Grassle
(3:00 p.m. - Coffee Break)

PANEL B - Biological Processes of
North Atlantic Submarine Canyons

Panel Members: Dr. Richard Cooper Dr. Jim Ray
Dr. Fred Grassle Ms. Katrina VanDusen
Dr. Barbara Hecker Ms. Pat Hughes

Dr. Nancy Maciolek

In addition to the stated hypotheses discussed during the morning
session, the following topics are also suggested for related

discussions:
ws Submarine canyons as nurseries for commercial fisheries.
= Benthic infauna of canyons.
m= Submarine canyon species: abundance and diversity.
w Habitat types and associated fauna.
ws Potential effects of varying flushing rates on canyon ecosystems.

C-4

MINERALS MANAGEMENT SERVICE
NORTH ATLANTIC SUBMARINE CANYONS WORKSHOP

AGENDA

PREPARATION OF DRAFT SCIENTIFIC PANEL
CONCLUSIONS AND RECOMMENDATIONS NARRATIVE SECTION

February 9, 1989*

(Coffee Breaks to be held at 10:00 a.m. & 3:00 p.m.)

During this final day of the workshop, the panel members are to meet to
prepare written drafts of their conclusions and recommendations focusing on
the workshop hypotheses discussed during the roundtable session and to
summarize their comments and views developed on the issues considered during
the concurrent panel sessions. This narrative section will form a
consolidated summary synthesis of the conclusions and recommendations of the
scientific panel members.

Rapporteurs will be available to assist in the preparation of the
scientific panel members conclusions and recommendation sections.

Co-chairpersons: Dr. Nancy Maciolek and Dr. Jerry Neff
8:00 a.m. Scientific Panel Deliberations
10:00 a.m. Coffee Break
10:15 a.m. Dialogue
11:00 a.m. Conclusions
12:00 LUNCH BREAK
feO00. p.m. Presentations and Wrap-up

3:00 COFFEE BREAK

*Preparation of summary synthesis and conclusions continued. Workshop ended
at approximately 2:30 p.m.

G5

APPENDIX D

MMS SUBMARINE CANYONS WORKSHOP PARTICIPANTS LIST

Dr. Donald Aurand (M)

Chief, Branch of
Environmental Studies

MMS - -Headquarters

12203 Sunrise Valley Drive

Reston, VA 22091

(703) 648-7866

Dr. Robert C. Ayers, Jr. (P)
Research Advisor

Exxon Production Research Company

P.O. Box 2189
Houston, TX 77001
(713) 965-4344

Dr. Heino Beckert (0)
Chief, Impact Analysis Unit
MMS--Atlantic Region

1951 Kidwell Drive

Vienna, VA 22182

(703) 285-2303

Dr. Paul D. Boehm (P)
Director, Marine Sciences
Arthur D. Little, Inc.

25 Acorn Park

Cambridge, MA 02140

(617) 864-5770

Dr. Michael H. Bothner (P)
Oceanographer

U.S. Geological Survey
Woods Hole, MA 02543

(508) 548-8700

Mr. Donald Bourne (R)
Box 21

Waquoit, MA 02536
(508) 548-1087

Dr. Michael Brody (0)

Fishery Biologist
MMS--Atlantic Region

1951 Kidwell Drive, Suite 601
Vienna, VA 22182

(703) 285-2188

D-1

Dr. Bradford Butman (P)
Oceanographer

U.S. Geological Survey
Woods Hole, MA 02543
(508) 548-8700

Ms. Roz Cohen (0)
Oceanographer

MMS

12203 Sunrise Valley Drive
Reston, VA 22091

(703) 648-7737

Dr. Richard A. Cooper (P)

Scientist & Director, National

Underwater Research Center

University of Connecticut,
Avery Point

Groton, CT 06340

(203) 445-4714

Dr. J. Frederick Grassle (P)
Senior Scientist

Woods Hole Oceanographic Institute
Woods Hole, MA 02543

(508) 548-1400

Dr. James Hain (R)

Associated Scientists at Woods Hole
Box 721

Woods Hole, MA 02543

(508) 564-4449

Dr. Barbara Hecker (P)

Associate Research Scientist Lamont
Doherty Geological Observatory
Palisades, NY 10964

(914) 359-2900 x448

Dr. Bruce Higgins (0)

NOAA Fisheries

Northeast Fisheries Center
Woods Hole, MA 02543

(508) 548-5123

Ms. Patricia E. Hughes (P)
OCS Coordinator
Massachusetts Coastal Zone
Management Program

Room 2006, Saltonstal]

100 Cambridge Street
Boston, MA 02202

(617) 727-9530

Dr. John Kraeuter (P)
Associate Director
Rutgers University
Shellfish Research Lab
P.O. Box 687

Port Norris, NJ 08344
(609) 785-0074

Mr. 1: E.-Landry. (0)
OCS Permit ENGR

EPA Compliance Bureau
JFK Building, Rm 2103
Boston, MA 02203
(617) 565-3508

Mr. James Lane (M)

Chief, Environmental Studies Unit
MMS--Atlantic OCS Region

1951 Kidwell Drive

Suite 601

Vienna, VA 22182

(703) 285-2155

Dr. Nancy Maciolek (P)
24 Hitty Tom Road
Duxbury, MA 02332
(617) 585-5822

Dr. Robert E. Miller (M)
Physical Scientist

MMS, Atlantic OCS Region

381 Elden Street, Suite 1109
Herndon, VA 22070

(703) 787-1066

Dr. Jerry M. Neff (P)
Battelle Ocean Sciences
397 Washington Street
Duxbury, MA 02332

(617) 934-0571

Dr. James P. Ray (P)

Manager

Environmental Sciences Support
MMS--Scientific Advisory Committee
Shell Oi]

P.O. Box 4320

Houston, TX 77210

(713) 241-3060

Dr. John Teal (P)

MMS--Scientific Advisory Committee
Woods Hole Oceanographic Institute
Woods Hole, MA 02543

(508) 548-1400 x2323

Dr. Page C. Valentine (P)
Geologist

U.S. Geological Survey
Woods Hole, MA 02543
(508) 548-8700

Mr. Bruce FP. Vild{P)
Principal Planner

State of Rhode Island
Department of Administration
Division of Planning

265 Melrose Street
Providence, RI 02907

(401) 277-2656

Ms. Patience Whitten (0)
EPA--Environmental Review
JFK Building, RGR - 2203
Boston, MA 02203

(617) 565-3414

Dr. R. Jude Wilber (R)
Sea Education Association
Box 6

Woods Hole, MA 02543
(508) 540-3954

Dr. Redwood Wright (R)

Associated Scientists at Woods Hole
Box 721

Woods Hole, MA 02543

(518) 548-5315

) indicates participant
) indicates observer

) indicates MMS staff

) indicates rapporteur

D-3

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