Content uploaded by Andrew S.Y. Mackie
Author content
All content in this area was uploaded by Andrew S.Y. Mackie on Feb 07, 2017
Content may be subject to copyright.
Sand Wave Field: The OBel Sands, Bristol Channel, UK
2012
James, J.W.C., Mackie, A.S.Y., Rees, E.I.S. & Darbyshire, T.
Elsevier
32 Jamestown Road, London NW1 7BY
225 Wyman Street, Waltham, MA 02451, USA
First edition 2012
Copyright © 2012 Elsevier Inc. All rights reserved
No part of this publication may be reproduced or transmitted in any form or by any means,
electronic or mechanical, including photocopying, recording, or any information storage
and retrieval system, without permission in writing from the publisher. Details on how to
seek permission, further information about the Publisher’s permissions policies and our
arrangement with organizations such as the Copyright Clearance Center and the Copyright
Licensing Agency, can be found at our website: www.elsevier.com/permissions
This book and the individual contributions contained in it are protected under copyright by the
Publisher (other than as may be noted herein).
Notices
Knowledge and best practice in this field are constantly changing. As new research and
experience broaden our understanding, changes in research methods, professional practices,
or medical treatment may become necessary.
Practitioners and researchers must always rely on their own experience and knowledge in
evaluating and using any information, methods, compounds, or experiments described herein.
In using such information or methods they should be mindful of their own safety and the
safety of others, including parties for whom they have a professional responsibility.
To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors,
assume any liability for any injury and/or damage to persons or property as a matter of
products liability, negligence or otherwise, or from any use or operation of any methods,
products, instructions, or ideas contained in the material herein.
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress
ISBN: 978-0-12-385140-6
For information on all Elsevier publications
visit our website at elsevierdirect.com
This book has been manufactured using Print On Demand technology. Each copy is produced
to order and is limited to black ink. The online version of this book will show color figures
where appropriate.
Seafloor Geomorphology as Benthic Habitat. DOI:
© 2012 Elsevier Inc. All rights reserved.2012
10.1016/B978-0-12-385140-6.00012-8
Sand Wave Field: The OBel Sands,
Bristol Channel, UK
J.W. Ceri James1,3, Andrew S.Y. Mackie2, E. Ivor S.
Rees3, Teresa Darbyshire2
1British Geological Survey, Keyworth, Nottingham, England, UK,
2Amgueddfa Cymru—National Museum Wales, Cathays Park, Cardiff,
Wales, UK, 3School of Ocean Sciences, Bangor University, Menai
Bridge, Wales, UK
12
Abstract
The OBel Sands, an area of sand waves up to 19 m high, cover an extensive area,
!1,000 km2, in the Outer Bristol Channel off the coast of Wales. The sand wave field can be
divided into a northern half with a dense concentration of bedforms on a sand substrate, and
southern half with isolated sand waves on a coarse substrate. In both areas, the sand waves
are generally asymmetric in cross profile, with steep west-facing lee slopes associated with
the Channel’s ebb tides. The sand waves commonly have abundant megaripples and second-
ary sand waves on their slopes; these dynamic environments maintain little or no epifauna.
The infaunal assemblages are varied and primarily related to sediment composition, sedi-
ment stability, and depth. Species richness is highest in coarse sediment between isolated
sand waves and on the nearby platform. These areas generally support a rich epifauna.
Key Words: marine habitat, sand wave, macrofauna, diversity, multivariate analyses,
Bristol Channel
Introduction
The OBel Sands, an extensive area of sand waves up to 19 m high, cover over
1,000 km2 in the Outer Bristol Channel off the Welsh coast (Figure 12.1). The sand
wave field can be divided into a northern half, the NOBel Sands, with a dense concen-
tration of bedforms on a sand substrate, and a southern half, the SOBel Sands, with
isolated sand waves on a coarse sediment substrate. The sand wave field stretches west
to east for about 40 km in its northern half; it narrows to the south to a width of about
12 km. Its north–south extent is over 37 km. The OBel Sands are surrounded by a sand
sheet to the north, and elsewhere by a seabed predominantly of coarse sediment and
rock; including these, the total area studied is about 2,400 km2 (Figure 12.1).
Seafloor Geomorphology as Benthic Habitat228
Figure 12.1 Geomorphic features, bedforms, and seabed character map of the Outer Bristol
Channel study area.
Sand Wave Field: The OBel Sands, Bristol Channel, UK 229
Across the OBel Sands, the ambient seabed declines from east to west at a depth
range of about 37 to !55 m. The Bristol Channel has the second highest tidal range
in the world. Although not as large as further east, where the Bristol Channel becomes
narrower, the tidal range in the Outer Bristol Channel is significant, with a mean spring
tidal range varying from around 6.5 to 8 m. The tidal wave emanating from the Atlantic
enters the study area from the southwest. Over the OBel Sands, the depth averaged
mean spring tidal currents are relatively strong, with values of between 1.0 and 1.3 m/s.
It is only within Carmarthen Bay and the lee of Lundy Island that tidal currents
decrease to "0.5 m/s. The tidal streams are commonly rectilinear, with the western
directed ebb tidal constituent being dominant. This tidal asymmetry is also matched
by the dominance of west-facing asymmetry in the large sand waves of the area, com-
monly indicative of net sand transport to the west.
The Outer Bristol Channel is open to the west and southwest. This is the source
direction of the strongest and most frequent winds. It also equates with the direction
of the longest fetch out into the Atlantic—over hundreds of kilometers. However,
modelling indicates that wave effects on the seabed in the Outer Bristol Channel are
only likely to be significant in water depths "20 m [1].
The OBel Sands are in an area where human impact on the benthic environment is
designated as high [2]. It is an area affected by shipping, some fishing, telecommu-
nication cables, and recent initiation of aggregate extraction. It has also been desig-
nated as a potential area for wind farm development [3].
The area was surveyed and studied from 2003 to 2006, and five research cruises
were conducted [4,5]. The geophysical survey strategy was based on 11 parallel cor-
ridors, 30–45 km long and about 5 km apart (Figure 12.2) covered with multibeam
and sidescan sonar across a kilometer-wide swath and a single line of boomer sub-
bottom profiler down the corridor center line. In total 2,177 line km of multibeam,
1,436 line km of sidescan, and 330 line km of boomer were collected. Singlebeam
echo sounder data was also used to provide a seabed morphology model across most
of the OBel Sands based on a 50-m grid (Figure 12.2) and enabled mapping and cor-
relation of the major sand waves between the survey corridors.
Within the survey corridors, seabed samples were collected using a 0.1-m2 modi-
fied Van Veen grab and provided 134 macrofaunal stations and 140 sediment sam-
ples. A 2-m beam trawl was deployed at 13 trawl box locations and completed 53
tows. The video and camera sledge was towed across the seabed at 24 locations and
was particularly useful in ground truthing the multibeam and sidescan data and inter-
pretations (Figure 12.3).
Geomorphic Features and Habitats
The present-day distribution of sediments and geomorphic features in the OBel
Sands area appears to be the product of sedimentation processes associated with
two major geological environments. The first is glacial and glacio-fluvial associ-
ated with the Quaternary Last Glaciation, when an ice lobe extended south out into
Carmarthen Bay and the northern half of the OBel Sands and initially deposited
Seafloor Geomorphology as Benthic Habitat230
Figure 12.2 Seabed morphology modelled from singlebeam data (1977) overlain with
multibeam data (corridors 1–11, south to north: 2003–2004; southeast rectangle: 2002).
(Multibeam rectangle provided by UK Maritime and Coastguard Agency. Singlebeam data
derived in part from material obtained from the UK Hydrographic Office with the permission
of the Controller of Her Majesty’s Stationery Office and UKHO. © British Crown & SeaZone
Solutions Ltd. 2004. All rights reserved. Data License No. 112005.006.)
Sand Wave Field: The OBel Sands, Bristol Channel, UK 231
Figure 12.3 Examples of acoustic and photographic images of the Outer Bristol Channel
seabed: (A) sidescan and photo showing minor sand ripples with mud/organic floc material
from the sand sheet southeast of Caldey Island, off Tenby; (B) multibeam and photo showing
minor sand ripples associated with a sand wave from the NOBel Sands; (C) example of
multibeam (location not marked) and photo showing surface lag gravel and shells from
between isolated sand waves in the SOBel Sands northeast of Lundy; (D) sidescan from
platform in southeast, with photo showing gravelly mixed sediment and exposed rock ledge
colonized by bryozoans Flustra foliacea and Alcyonium digitata, sponges, and the crab,
Cancer pagurus.
Seafloor Geomorphology as Benthic Habitat232
glacial sediments subsequently overlain by sand and gravel. At the glacial maximum,
around 22,000 years ago, sea level would have been at least 100 m lower than the
present day, and the area would have been a marginal glaciated terrestrial environ-
ment. The subsequent amelioration of climate brought on the development of the
second major geological environment with the gradual rise in sea level culminating
in a fully marine environment. The morphology of the OBel Sands area underwent
considerable metamorphosis as sea level rose, and wave and tidal currents began to
fashion mobile sandy sediments to produce one of the most significant sand wave
fields on the UK continental shelf.
The geomorphic features described here were identified from the interpretation
of the corridor-based high-resolution seismic surveys, plus the seabed morphology
model derived from singlebeam echo sounder data. Data from previous studies, par-
ticularly with regard to seabed sediment distribution based on sampling, have also
been utilized. These have all been analyzed and mapped within a GIS system to pro-
duce a fourfold classification based on large and extensive regional scale features.
The classification includes the OBel Sands subdivided into two areas, the NOBel
Sands and the SOBel Sands.
Sand Sheet (Figure 12.1, 1)
Lies within the southwest-facing embayment of Carmarthen Bay, which is about
27 km wide and deepens gradually to the southwest and reaches maximum depths
of 25–30 m across its mouth. It is dominantly a smooth seabed of fine to medium
sand with some small rippled bedforms. There are some muddy (Figure 12.3A),
coarse, and shelly patches and channels. Waves are important as a transport mecha-
nism in shallow water as tidal current energy decreases. The inner bay acts as a store
for sandy sediment. The western part of Helwick Bank, predominantly composed of
medium sand, occurs in the southeastern part (Figure 12.1).
Sand Wave Field (NOBel Sands) (Figure 12.1, 2)
An extensive sand wave field covering an area of around 440 km2. The crests of the sand
waves in the eastern and central part of NOBel Sands lie in water depths between 25 and
40 m, whereas those further to the west have crests in water depths of 40–60 m. The dis-
tance between the individual waves varies on average from 1,000 to 1,500 m, though the
lower and upper ranges observed are 600–3,000 m. The sand waves are laterally exten-
sive and continuous, with crest lengths ranging from 1 to 7 km long. Although the sand
waves themselves comprise medium- to coarse-grained sand, the seabed surrounding
these features tends to be slightly coarser, consisting of gravelly sand or sandy gravel.
Between the sand waves, the overall topography of the seabed tends to be relatively flat.
The maximum sand wave height observed in the NOBel Sands is 19 m, though more
commonly observed heights are 12–14 m. The sand wave crests are oriented with a regu-
lar sinuosity aligned on two principal trends: NNW (330°/340°) to SSE (150°/160°), and
NNE (10°/20°) to SSW (190°/200°).
Sand Wave Field: The OBel Sands, Bristol Channel, UK 233
The sand waves display strong asymmetry, with lee slopes facing west to southwest.
The angle of the lee slopes generally range between 5° and 10°, although upper crest
sections of the lee slopes on some waves may be much steeper, with angles of up to 24°.
The stoss slopes are much gentler and have angles generally less than 3°. The surfaces of
the large sand waves are commonly covered by mobile sediment in the form of megar-
ipples and ripples (Figure 12.3B). However, although their surfaces are mobile, the posi-
tion and form of these large sand waves appears to have remained static in recent times
given the resolution of the 1977 data set (Figure 12.2). Hence, the large sand waves may
be in a state of in situ equilibrium. In the south of the sand wave field, there is an area
of bifurcating high-frequency sand waves. These include primary waves that are gener-
ally 4–10 m high, with both west-facing asymmetrical sand waves and symmetrical sand
waves, and secondary sand waves up to 4 m high.
Isolated Sand Waves (SOBel Sands) (Figure 12.1, 3)
In the SOBel Sands, the commonly isolated sand waves are generally less than 10 m
high, with wavelengths ranging from 150 to 1,800 m. The majority of sand wave
crests lie in water depths of 40 m, with a relatively flat seabed between the waves
at around 45 m. The sand waves are oriented approximately normal to the peak tidal
currents (ranging from NNW–SSE to N–S) and display strong asymmetry, with the
lee slopes facing west to southwest. The angle of the lee slope ranges between 5° and
10°, although smaller sections of the lee slopes on some sand waves have steeper
slopes, with angles of up to 18°. The stoss slopes are much gentler, with angles of
less than 3°. Sidescan data indicate that megaripples occur on both the stoss and lee
slopes of the !10- and "10-m sand waves (Figure 12.1). These megaripples are
often oriented obliquely to parts of the sand wave crests, suggesting that the orien-
tation of the megaripples is determined by the local flow conditions over the larger
waves and not solely by the residual tidal currents. A number of sand waves have
developed double crests that have an elliptical plan along sand wave crests. They are
most common on individual waves in the SOBel Sands. They can be found in vari-
ous stages of development with numerous individual ellipses aligned along crests.
Some are not fully developed and may be an indication of restricted sediment sup-
ply. The seabed between the isolated sand waves in the SOBel Sands is covered by
predominantly coarse sediment (Figure 12.3C) with thin sand, which can be seen in
patches or as sand ribbons and streaks. These may have rippled or megarippled sur-
faces. In some areas, isolated outcrops of rock may appear at the seabed.
Platform (Figure 12.1, 4)
The platform which lies to the southwest and east of the OBel Sands is character-
ized by a coarse sediment substrate of gravelly sand, sandy gravel, and gravel with
patches and streaks of thin sandy sediment. Rock exposed on the seabed in the south-
west are mainly individual masses; there is some structure and lineation in the out-
crops, but bedding is not well developed. The platform in the southeast is dominated
Seafloor Geomorphology as Benthic Habitat234
Figure 12.4 Diagrammatic distribution map of the benthic macrofaunal assemblages in the
Outer Bristol Channel study area, determined from a semiquantitative cluster analysis of 127
stations (each 2 # 0.1 m2 Van Veen grab samples; 0.5 mm mesh sieve).
Sand Wave Field: The OBel Sands, Bristol Channel, UK 235
by well-bedded rock outcrops, exposed at the seabed in water depths of 20 to less than
40 m in the center of the Channel. The rock outcrops have formed a very frequent dense
series of small scarps and troughs up to a meter or two high; the majority are "0.5 m
high (Figure 12.3D). The rocks have been subject to tectonic movement, and the bed-
ding exposed on the seabed can be linear and sinuous, and disrupted by faults and folds.
Sediment is commonly restricted to the troughs and can include gravel and sand. There
are a few small isolated sand waves, as well as occasional sand ribbons and sand patches.
Biological Communities
Macrofaunal characterization was primarily done through analyses of quantita-
tive data acquired through deployment of a modified 0.1 m2 Van Veen grab at 127
stations. Seven more stations were sampled qualitatively using the grab or dredge,
while three additional stations were from out of the study area. The larger epifauna
and sediment surface were assessed at 13 beam trawl and 24 video locations. A total
of 948 taxa (including 130 colonial species) were found, and an average of 1,665
individuals was enumerated per 0.2 m2 quantitative station. Various analyses were
carried out on the data, including a semiquantitative cluster analysis. In this analy-
sis, frequency scale estimates of the colonial epifauna (hydroids and bryozoa) were
assigned numerical equivalents and added to the quantitative infaunal data.
The semiquantitative cluster analysis (not shown) revealed five broad faunal clusters,
and the distributions of each (Figure 12.4) were in general agreement with the major geo-
morphic features (Figure 12.1). Four subgroups were recognized within faunal assem-
blages II and III, while six subgroups were delineated within assemblage IV. The faunal
characterizations within each main geomorphic feature are summarized below according
to the habitat (biotope) classification manual for Britain and Ireland [6].
Sand Sheet
In Carmarthen Bay (Figures 12.1 and 12.4), the sand sheet supported the main
assemblage II subgroup (IIb) “Fabulina fabula and Magelona mirabilis with venerid
bivalves and amphipods in infralittoral compacted fine muddy sand.” Areas of more
mobile sand to the southwest and southeast (north of Helwick Bank) had assem-
blages with affinities to the sand wave field of the NOBel Sands to the south. The
Helwick Bank fauna (assemblage I), associated with fine to medium sands, had only
45 taxa and was described as a “sparse fauna in infralittoral mobile clean sand.” This
is consistent with an earlier study of Helwick Bank [7].
The faunas (IIc and IId) of the stable sands to the south and southwest of the sand
sheet exhibited affinities with other biotopes, characterized by bivalves “Abra alba
and Nucula nitidosa in circalittoral muddy sand or slightly mixed sediment,” or by
polychaetes and brittle-stars—“Owenia fusiformis and Amphiura filiformis in off-
shore circalittoral sand or muddy sand.” Stony areas southeast of Tenby were part
of a loosely defined assemblage V. Juvenile mytilid mussels were abundant, and
encrusting and colonial species common.
Seafloor Geomorphology as Benthic Habitat236
Sand Wave Field (NOBel Sands)
Dominated by two subgroups of faunal assemblage III (Figure 12.4). Subgroup IIIa
was assigned to the “Hesionura elongata and Microphthalmus similis with other inter-
stitial polychaetes in infralittoral mobile coarse sand” biotope. Subgroup IIIb was very
closely related, but increased presence of tube-dwelling polychaetes such as Lagis
koreni and Spiophanes bombyx, and reductions in small interstitial species, reflected
the generally finer sediments and more stable conditions. Some gravelly areas had
assemblage IV biotopes similar to those found in the SOBel Sands to the south. The
biotopes in the northwest of the NOBel Sands were largely those attributed to assem-
blage subgroups IIc and IId, as found in the adjacent sand sheet area to the north.
Isolated Sand Waves (SOBel Sands)
Sand waves occurring within the SOBel Sands (Figures 12.1 and 12.4) had the same
fauna as assemblage subgroup IIIa found in the sand waves of the NOBel Sands.
However, the seabed of the SOBel Sands was mainly gravelly, and most of the area
was characterized as assemblage subgroup IVa in terms of both its infauna and
epifauna. The former, described as “Mediomastus fragilis, Lumbrineris spp. and
venerid bivalves in circalittoral coarse sand or gravel,” was overlain by the hydroids
“Sertularia cupressina and Hydrallmania falcata on tide-swept sublittoral sand with
cobbles or pebbles” with patches of the encrusting honeycomb worm “Sabellaria
spinulosa on stable circalittoral mixed sediment.” The fauna here closely resembles
that found in gravelly areas of the southern Irish Sea [8,9].
Platform
Fauna within the platform areas was almost entirely attributable to assemblage sub-
groups IVa, IVb, and IVe. Subgroup IVb showed an increased presence of the cumacean
Pseudocuma similis, echinoid Echinocyamus pusillus, and bivalve Goodallia triangula-
ris, and was considered a sandier variant of subgroup IVa. The platform in the southeast,
to the north of Morte Point (Figure 12.1), was characterized by either subgroup IVa or
IVe. The fauna of the latter was indicative of a mosaic of bottom types—from bedrock to
cobbles, sand veneers, and pockets of muddy mixed sediments. This area was described
as having a “polychaete-rich deep Venus community in offshore mixed sediment” co-
occurring with “Sabellaria spinulosa on stable circalittoral mixed sediment.” The hetero-
geneity of the seabed was visible in videos of the area, and areas of exposed rock showed
evidence of the “Flustra foliacea and Hydrallmania falcata on tide-swept circalittoral
mixed sediment” biotope (Figure 12.3D).
Species Richness
Patterns in species richness were investigated in relation to geomorphic features and
generalized sediment types: muddy, sandy, gravelly, and stony (Figure 12.5). The
Helwick Sand Bank was clearly the most impoverished, with the more stable sand
sheet of Carmarthen Bay supporting more species, while gravelly sediments were
Sand Wave Field: The OBel Sands, Bristol Channel, UK 237
the richest. Conversely, the gravelly sediments in the sand wave field (NOBel Sands)
were not richer than the sands. The mobility of the sand was thought to be the con-
trolling feature there, restricting the development of the rich infaunal and epifaunal
assemblages usually found in more stable gravelly areas [8–10]. The gravelly sedi-
ments of the isolated sand wave field (SOBel Sands), platform, and stony areas had
the highest species richness and the most epifaunal species.
Surrogacy
The relationships between the benthic macroinfauna were investigated [5] using the
BIO-ENV and LINKTREE routines in PRIMER [11,12]. The strongest relation-
ships were obtained with a combination of sediment parameters (primarily sand and
mud content) and depth. The correlations (ρs $ 0.59%0.62 for 3–6 variables) were
Figure 12.5 Macrofaunal species richness according to the broad sediment category for
each geomorphic feature: (A) quantitative grab data (excluding colonial epifauna) and
(B) qualitative data including colonial bryozoans and hydroids. Species richness calculated
as the number of taxa per 0.2 m2 (2 # 0.1 m2 Van Veen Grab samples; 0.5 mm mesh sieve)
station. Numbers on bars represent the number of stations involved.
Seafloor Geomorphology as Benthic Habitat238
similar to those found in studies carried out in the Celtic Sea/Irish Sea area to the
west and northwest of the Bristol Channel [8,9]. The inclusion of hydrodynamic data
from a current velocity model from the Proudman Oceanographic Laboratory did not
improve the species–environment relationships, because the resolution of the model
could not differentiate changes at the scale of the sand waves.
Acknowledgments
This paper is based on research undertaken for the Outer Bristol Channel Marine Habitat Study.
The two principal funding bodies for the study were the Aggregate Levy Sustainability Fund for
Wales, which is administered by the Welsh Assembly Government, and the Sustainable Land
Won and Marine Dredged Aggregate Minerals Programme of the Aggregate Levy Sustainability
Fund in England. The National Museum of Wales (NMW) and the British Geological Survey
contributed data from their own research programs and made funding available for surveys.
The Natural Environment Research Council provided ship time for one of the geophysical
surveys. The Crown Estate and the British Marine Aggregate Producers Association (BMAPA)
provided funding and contributed data. The Maritime and Coastguard Agency kindly provided
multibeam survey data. Chris Howlett of the UKHO was instrumental in digitizing the 1977
singlebeam survey data. Sally Philpott, Angela Morando, and Gareth Jenkins of BGS and Kate
Mortimer of NMW are thanked for their contribution to the marine habitat study. Ceri James
publishes with the approval of the Director, British Geological Survey (NERC).
References
[1] H.R. Wallingford. Dredging on Nobel Banks (Area 476), Bristol Channel, Coastal
Impact Study Report, EX 4597, Hydraulics Research Wallingford, Wallingford, 2002.
[2] B.S. Halpern, S. Walbridge, K.A. Selkoe, C.V. Kappel, F. Micheli, C. D’Agrosa, et al., A
global map of human impact on marine ecosystems, Science 319 (2008) 948–952.
[3] J. McMahon, T. Golding. Atlantic Array: Environmental Impact Assessment Scoping
Report, Bristol Channel Zone Ltd/RWE npower Renewables, Swindon, 2010, p. 309.
http://infrastructure.independent.gov.uk/wp-content/uploads/2010/04/Atlantic-Array-
Scoping-Report.pdf.
[4] J.W.C. James, S.L. Philpott, G. Jenkins, A.S.Y. Mackie, T. Darbyshire, E.I.S. Rees. Outer
Bristol channel marine habitat study—2003 investigations and results, British Geological
Survey Commissioned Report CR/04/054, 2004, p. 113.
[5] A.S.Y. Mackie, J.W.C. James, E.I.S. Rees, T. Darbyshire, S.L. Philpott, K. Mortimer,
et al. (2006). The outer Bristol channel marine habitat study. Studies in Marine
Biodiversity and Systematics from the National Museum of Wales, BIOMÔR Reports 4,
1-249 & A1-A227, &DVD-ROM, 2007.
[6] D.W. Connor, J.H. Allen, N. Golding, L.K. Howell, L.M. Lieberknecht, K.O. Northen,
et al. (2004). The marine habitat classification for Britain and Ireland version 04.05.
JNCC, Peterborough. ISBN 1 861 07561 8. (internet version) www.jncc.gov.uk/
MarineHabitatClassification.
[7] T. Darbyshire, A.S.Y. Mackie, S.J. May, D. Rostron. A macrofaunal survey of Welsh
sandbanks, Countryside Council for Wales CCW Report 539, 2002, p. 113.
Sand Wave Field: The OBel Sands, Bristol Channel, UK 239
[8] A.S.Y. Mackie, P.G. Oliver, E.I.S. Rees. Benthic biodiversity in the southern Irish Sea,
Studies in Marine Biodiversity and Systematics from the National Museum of Wales,
BIOMÔR Reports 1, 1995, p. 263.
[9] K.A. Robinson, T. Darbyshire, K. Van Landeghem, C. Lindenbaum, F. McBreen,
S. Creavan, et al. Habitat Mapping for Conservation and Management of the Southern
Irish Sea (HABMAP) I: Seabed Surveys, Studies in Marine Biodiversity and Systematics
from the National Museum of Wales. BIOMÔR Reports 5(1), 2009, p. 148, Appendices
p. 74.
[10] A.S.Y. Mackie, Macrofaunal assemblages and their sedimentary habitats: working
toward a better understanding, Irish Sea Semin. Rep. 32 (2004) 30–38.
[11] K.R. Clarke, R.N. Gorley, PRIMERv5: User Manual/Tutorial, PRIMER-E Ltd,
Plymouth, 2006.
[12] K.R. Clarke, R.M. Warwick, Change in marine communities: an approach to statistical
analysis and interpretation, PRIMER-E Ltd, Plymouth, 2001.
