Jncc coastal Directories Project Region 11 The Western Approaches

4.2.1  Introduction
This section covers the occurrence and distribution of sea-
bed habitats and of groups of species that live on the sea bed
(benthic communities, collectively called the benthos), both
in the intertidal zone and subtidally; the distribution and
occurrence of individually rare and scarce species is covered
in section 5.4. 
There are a great variety of marine habitats and
communities present along the coastline of this region.  At the
western tip of Cornwall are very exposed rocky shores, high
cliffs and exposed sandy beaches; in the upper Bristol Channel
there are extensive sandflats and mudflats subject to variable
salinity and a huge tidal range (12.3 m during spring tides at
Avonmouth - the second largest range in the world).  In the
sublittoral there is a wide range of habitats, and communities
associated with these are often particularly rich in species.
The influence of the relatively warm waters of the Gulf
Stream, which bathe the South-West Peninsula, and to a lesser
extent of a Lusitanian current from the south give a distinctive
character to many communities.  Many of the Mediterranean-
Atlantic species that occur, such as sea fans, cup corals and
soft corals, are of high nature conservation importance largely
as a result of their rarity in the UK, confined as they are to the
south-west.  In addition, they are often very colourful,
thereby adding to the aesthetic appeal of many sites.
Some of the country’s richest areas of marine life are
concentrated within the region.  Many of these are now
recognised by various designations (see also 
Chapter 7
).
England’s first (and at present only) statutory Marine
Nature Reserve exists around the island of Lundy in the
Bristol Channel.  There are also five Voluntary Marine
Nature Reserves in the region: at Roseland, on the Fal River
(established 1982, although currently inactive), the Helford
River Voluntary Marine Conservation Area (1987); around
the Isles of Scilly (1989); Polzeath Voluntary Marine Wildlife
Area (Cornwall) (1995) and the north Devon coast from
Morte Point to Combe Martin (1994).  English Nature has
identified seven Sensitive Marine Areas (SMAs) within this
region (English Nature 1994a) (see 
Map 7.4.1
).  SMA is a
non-statutory designation that highlights areas of particular
conservation interest.  In addition there are four possible
Special Areas of Conservation (SACs) qualifying for their
marine interest.  These are the Fal and Helford, the Isles of
Scilly, Lundy Island and the Severn Estuary.
A number of wrecks (ships, aircraft and other solid
material) occur off the coast of this region, as elsewhere (see
also 
section 6.4
).  These objects offer hard substrate in areas
that may be largely sedimentary, thus providing discrete
new habitats for opportunistic colonising species that
otherwise would not be present. 
4.2.2  Important locations and species
Table 4.2.1 
lists locations of marine biological importance
mentioned in the text (
Map 4.2.1
).  There are likely to be
other areas of importance for which there is currently
insufficient information on which to base an assessment. 
Region 11  Chapter 4  Marine and estuarine environments
68
4.2  The sea bed
R.A. Irving
5°W
Region 10
Region 12
1,2
3
4–9
10
11
12,13
14
15
16
17
18
19
20
21
22 23
24
25
26
27
28
29
30
34
31-33
35-39
40
41
42
43
44
45
46
47
Map 4.2.1  
Locations of marine biological interest described in the
text (see 
Table 4.2.1
).
Falmouth to Land’s End
Falmouth and the Helford River together form one of the
best ria (drowned river valley) systems in Britain.  It is of
major nature conservation interest and has been put
forward as a possible Special Area of Conservation (SAC)
for its sublittoral sandbanks, intertidal mudflats and
sandflats and large shallow inlets and bays.  Its interest is
also recognised by the identification of the stretch from
Dodman Point (Region 10) to the Lizard as a Sensitive
Marine Area (SMA) (English Nature 1994a) (see also 
section
7.4.4
).  The Fal Estuary has a high diversity of marine
habitats, communities and species.  Slow tidal streams and a
high rate of siltation have resulted in the presence of
extensive sediment banks (Davies in prep. b).  A number of
sites within the Fal Estuary are of particular importance.
Place Cove, including the adjacent Amsterdam Point, near
the mouth of the Percuil River, is a sheltered sediment cove
with nationally important rich communities of burrowing
species (Powell et al. 1978).  Patches of sublittoral rock, an
uncommon habitat within marine inlets, provide a
substratum for a rich sponge and sea squirt community
(Davies in prep. b).  The St. Mawes Bank to the west of the
Roseland peninsula is also of national importance for its
extensive (approximately 150 ha) bed of living maerl, an
unusual calcareous alga.  This is the best developed maerl
bed outside Scotland.  Two species are present:
Phymatolithon calcareum and Lithothamnion coralloides.  The
maerl nodules form a lattice structure which supports a
wealth of animal and algal species, including the rare
Couch’s goby Gobius couchi and two nationally important
species of red alga.  Further inshore, the coarse sediment is
colonised by eelgrass Zostera marina, which also has a rich
and distinctive community associated with it.  Further
north, at Turnaware Point, the tide-swept stony sediment
has a diverse array of species of regional importance
(Rostron 1987).
The Helford River is a shallow estuary, with rocky
shores and moderate tidal streams in the lower reaches,
leading to the development of interesting marine
communities.  Powell et al. (1978) described the whole

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