Jncc coastal Directories Project Region 11 The Western Approaches

5.4  Rare sea-bed species
103
Table 5.4.1  
‘Nationally rare’ and ‘nationally scarce’ marine benthic species found in the region (continued)
Species
Type of
Area(s) of
Habitat/associations
Comments
Useful
organism
occurrence
reference
Watersipora
complanata*
A sea mat
Isles of Scilly
Intertidal.  Distinctive
encrustations on hard
substrata.
Southern.  Elsewhere
widely distributed in the
Mediterranean.
Hayward &
Ryland (1979)
Smittina affinis*
A sea mat
Lundy
Encrusting hard substrata
from about 2-18 m
Elsewhere from Brittany
Hayward &
Ryland (1990)
Schizobrachiella
sanguinea*
A sea mat
Off Helford River
Sublittoral on hard
substrata from 10-50 m
Southern species.  Occurs
south to the western
Mediterranean.
Hayward &
Ryland (1979)
Hippoporidra
lusitania*
A sea mat
Lundy
Little known
Also known from Isle of
Man and N. Brittany.
May be relict species.
Turbicellepora
magnicostata*
Orange peel
bryozoan
Isles of Scilly
Encrusting a variety of
hard substrata and algae.
Occurs intertidally to
50 m.
Southern.  In Great Britain
known only from the Isles
of Scilly.  Also known
south to the
Mediterranean.
Hayward &
Ryland (1979)
Pycnoclavella
aurilucens
A sea squirt
Porthkerris Bay, Isles of
Scilly, Gurley Rock
(Harlyn Bay), Camel,
Kellan Head, Lobber
Point, Sharpnose Point,
Lundy, Rillage Point,
Blackstone Point,
Highveer Point
Current-swept rocks at
10-30 m
Cautiously regarded as
scarce.  Southern Also
from Brittany & perhaps
south to Mediterranean.
Hayward &
Ryland (1990)
Phallusia mammillata
A sea squirt
Helford River,
Isles of Scilly
On hard substrata with
slow to fast water
movement.  Lower shore
to 180 m.
Southern species.  In GB
occurs mainly off
southern Cornwall and
Devon.  Also Spain &
Mediterranean.
Hayward &
Ryland (1990)
Molgula oculata
A sea squirt
Helford River, Isles of
Scilly, St. Ivels Island,
Lundy
Low shore and sublittoral
sediments, usually partly
protruding
May occur more widely
than currently known
Hayward &
Ryland (1990)
Aglaothamnion
diaphanum*
A red
seaweed
Isles of Scilly
On variety of substrata
including other algae and
bedrock.  Subtidal from
about 7-25 m at
moderately wave-exposed
sites.
Southern species.  Also
known south to Atlantic
coast of France.
Maggs &
Hommersand
(1993)
Aglaothamnion
priceanum*
A red
seaweed
Manacles
On other algae from about
5-30 m.  Occurs on
moderately exposed
shores.
Occurs from Norway to
NW France.  Found very
infrequently.
Maggs &
Hommersand
(1993)
Cryptonemia
lomation*
A red
seaweed
Manacles, Isles of Scilly
Habitat poorly known
Southern species.  These
are the first authentic
records outside the
Mediterranean.
Maggs &
Guiry (1987a)
Gelidium
sesquipedale*
A red
seaweed
Sennen Cove, Gurnard’s
Head, Isles of Scilly
Shallow subtidal.  Occurs
on coasts exposed to
severe wave action.
Southern species
restricted in GB to
Cornwall & Devon.
Elsewhere south to
Mediterranean &
N. Africa.
Dixon & Irvine
(1977)
Gelidiella calcicola*##
A red
seaweed
Fal Estuary, Isles of Scilly
Normally confined to
maerl
Localised in restricted
habitat
Maggs &
Guiry (1987b)
Lithothamnion
corallioides##
Maerl
Fal Estuary, Helford River Forming maerl beds.
Associated with rich
assemblages of deposit
and suspension feeders.
On EC Habitats & Species
Directive, Annex Vb.
Falmouth has the most
extensive living maerl bed
in England.  In Helford it
is the most abundant
maerl species.
Irvine &
Chamberlain
(1994)

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Region 11  Chapter 5  Important species
104
Table 5.4.1  
‘Nationally rare’ and ‘nationally scarce’ marine benthic species found in the region (continued)
Species
Type of
Area(s) of
Habitat/associations
Comments
Useful
organism
occurrence
reference
Gracilaria bursa-
pastoris
A red
seaweed
Helford River, Bosahan
Head, Kennack Sands,
Isles of Scilly
On stone in sheltered
places.  Upper subtidal,
often with sand
deposition.
Southern.  Elsewhere
widely distributed in
warm waters.
Dixon & Irvine
(1977)
Gracilaria
multipartita
A red
seaweed
Helford River
On stone from upper
subtidal to 15 m.  Tolerant
of sand and silt
deposition.
Southern.  Probably
widely distributed in
warm waters.
Dixon & Irvine
(1977)
Schmitzia hiscockiana
A red
seaweed
Carrick North Point (Fal
Estuary), Isles of Scilly,
Lundy
Subtidal current-exposed
cobbles
Scattered distribution in
GB.  Common at few sites
of occurrence.  Possibly
endemic to the British
Isles.
Maggs &
Guiry (1985)
Gigartina pistillata
A red
seaweed
Lizard (Kennack, Soapy
Cove, Asparagus Is.,
Kynance Cove, Jangye-
ryn), Isles of Scilly
On stone.  Shallow
subtidal, in pools and
occasionally exposed by
the tide.  Tolerant of sand
cover.  Sheltered and
slightly wave-exposed
sites.
South-western species in
British Isles
Dixon & Irvine
(1977)
Cruoria
cruoriaeformis##
A red
seaweed
Fal Estuary, Isles of Scilly
Virtually confined to
maerl
Southerly species in the
British Isles
Maggs &
Guiry (1989)
Bornetia secundiflora* A red
seaweed
Helford River, Isles of
Scilly, Booby’s Bay (?)
Boulders and bedrock.
Subtidal fringe to 3 m
depth.  Moderate to
exposed sites.
Southern species.
Occurring south to
Morocco and
Mediterranean.
Maggs &
Hommersand
(1993)
Pterosiphonia pennata A red
seaweed
Lizard (Cadgwith), Isles
of Scilly, Greenaway
Beach, Tintagel Head,
Penhally Hill, off Beeny
Sisters, Concleave Strand,
Lower Sharpnose Point,
Lundy
On muddy bedrock and
pebbles and also on maerl.
Moderate to very wave
sheltered sites.  Extreme
low water to 10 m.
Southern species.  SW
Europe and
Mediterranean.  Wide
distribution in Atlantic
and Pacific.
Maggs &
Hommersand
(1993)
Zanardinia prototypus A brown
seaweed
Mother Ivey’s Bay, Camel,
Penally Hill, Beeny
Sisters, Pentagon, Lundy,
Concleave Strand, Baggy
Point to Foreland Point
On hard substrata.
Subtidal to 20 m.
Especially on silty rock.
Subtropical to warm
temperate species.
Ephemeral species -
probably substantial
annual fluctuations in
population size.
Fletcher (1987)
Choristocarpus
tenellus
A brown
seaweed
E. Pennally Hill, Lundy
On gravel around 20 m
Little known
Padina pavonica
Turkey
feather alga
Boscastle
On hard substrata
Southern.  Ephemeral
species - substantial
changes in populations
with time.
Price et al.
(1979)
Carpomitra costata
A brown
seaweed
Falmouth, Manacles, UCY
reef, Isles of Scilly, off
Penally Hill, off Beeny
Sisters, Lundy
On bedrock and boulders.
Subtidal to 37 m.  Tolerant
of sand cover.
Probably a summer
annual.  Southern species.
Fletcher (1987)
Species names are after Howson (1987); in the absence of a specific common name the nearest available group name has been used.  Key: *
= nationally rare; # = protected under the Wildlife & Countryside Act 1981; ## = maerl or in association with maerl; ? = present occurrence at
this site uncertain/dubious record.  Note: many of the scarce species listed here are only a little more common than the rare species listed.
the marine environment in the UK (Fowler & Laffoley 1993).
It may also be possible that some out-posted populations of
particular species at the limit of their range may be
genetically isolated and/or divergent from core populations
and important to the genetic biodiversity of the species as a
whole.  The importance of genetic, species and habitat
biodiversity in the UK has recently been the focus of
Biodiversity: the Steering Group report (Anon. 1995).  Ecological
and pragmatic arguments for the conservation of
populations of species that are rare because they are at the
margins of wider distributions are summarised by Hunter &
Hutchinson (1994).

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