Jncc coastal Directories Project Region 11 The Western Approaches

3.4.1  Introduction
The term coastal lagoons is used here to include true
lagoons, i.e. those wholly or partially separated from the sea
by a natural sedimentary barrier, and also artificial brackish
ponds and coastal pools, of a similarly restricted tidal range
and often containing comparable lagoonal wildlife.  Lagoons
are commonly shallow, often with a varying salinity ranging
from above to below normal sea-water levels (35 g/kg).
Freshwater systems are not considered here, nor are fully
flushed tidal pools.  
The contribution of the region’s lagoons to the size of the
British resource as a whole is shown in 
Table 3.4.1
.  The five
true lagoons of the region total 8.5 ha, amounting to just
over 1% of Britain’s total natural lagoonal resource (or 4% of
that resource excluding The Fleet, Dorset, which is by far
Britain’s largest lagoon, comprising nearly 70% of the total
resource) and 6% of the lagoonal resource that was regarded
by Barnes (1989) as being ‘especially noteworthy in the
national context’, again excluding The Fleet.  The region is
therefore of low significance nationally, although the
Swanpool Lagoon, Falmouth, Cornwall, is important in the
national context.  Throughout the region there are also a
Region 11  Chapter 3  Terrestrial coastal habitats
52
3.4  Coastal lagoons
Dr R.N.Bamber & Dr R.S.K.Barnes
Catsford
Common
Aberthaw
Bryher
Dennis
Cove
Tresemple
Swanpool
Maenporth
5°W
Natural lagoons
Other saline pools
Region 10
Region 12
Map 3.4.1
Coastal lagoons and lagoon-like habitat
Table 3.4.1  
Lagoonal areas for region in context
Region
Lagoonal
Overall %
% of GB total
area (ha)*
of GB total
excl. The Fleet
Cornwall (part)
6
<1
1
Somerset
1
<1
<1
Avon
0
0
0
Gloucester
0
0
0
Gwent
0
0
0
S. Glamorgan
2
<1
<1
Mid Glamorgan
0
0
0
Region 11
9
1
1
West Coast
98
8
13
Great Britain
1,261
Sources: Seaward (1986), Sheader & Sheader (1987, 1989).  Key:
*areas rounded to the nearest whole hectare.
Table 3.4.2  
Lagoons surveyed
Name
Grid ref.
Area
Type
(ha*)
Cornwall
Tresemple 
SW855446
<1
Sluiced pond
Swanpool
SW802315
4
Natural, estuarine
Maenporth
SW788297
0.5
Natural, estuarine
The Pool, Bryher,
SV874149
1.5
Natural, uncertain
Isles of Scilly
Dennis Cove Pool 
SW921744
<1
Sluiced pond
Somerset
Catsford Common
ST248451
1
Natural, percolation
S. Glamorgan
Aberthaw Lagoon
ST036602
1.5
Estuarine
Source: Barnes (1988, 1989).  Key: *to the nearest 0.5 ha.
number of small pools retained behind sea walls and coastal
sluices, generally less than 1 ha in size and of low salinity
(e.g. Tresemple, and Dennis Cove Pool, Cornwall).  
3.4.2  Important locations and species
Map 3.4.1
shows the locations of the lagoonal and other
saline pools mentioned; 
Table 3.4.2
gives details of their
areas and physiography.
True lagoons support only three types of aquatic
vegetation, namely stands of green algae (Chaetomorpha spp.,
Ulva spp. and Enteromorpha spp.), of sea-grasses and similar
plants (predominantly tasselweeds Ruppia spp.) and, much
more rarely, of stoneworts (especially Lamprothamnium).
Much of the area of their beds, however, is bare sediment,
devoid of vegetation cover.  Fringing stands of reeds
Phragmites spp., saltmarsh plants and/or sea club-rush
Scirpus maritimus are usual.  All these communities, with the
exception of the stoneworts, occur in the region.
Lagoons possess a characteristic aquatic invertebrate
fauna that shows little regional variation, even within
Europe.  In Britain, several of these species are very rare and
are protected under the Wildlife & Countryside Act 1981.
One of these protected species, the trembling sea mat
Victorella pavida, has its only UK occurrence in this region, in
Swanpool.  Swanpool is also one of the very few British
localities for the copepod Ergasilus lizae, which is parasitic
on grey mullet.  Other notable lagoonal species are the
brackish-water sand-shrimp Gammarus chevreuxi (in three
lagoons: Swanpool, Maenporth and Bryher), the lagoonal
mud snail Hydrobia ventrosa (at Catsford Common,
Somerset), and the lagoonal shrimp Corophium insidiosum
and lagoonal cockle Cerastoderma glaucum (in dense
populations in Aberthaw Lagoon).  The lagoonal prawn
Palaemonetes varians is common in the lagoons and small
saline pools of the region.
3.4.3  Human activities
Little active management is applied to the coastal lagoons
themselves, although the surrounding land is often

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intensively managed.  Aberthaw Lagoon has been much
reduced in area as a result of waste fuel ash dumping from
Aberthaw Power Station, which owns the land.  Following
advice, a policy was instigated in 1991 to maintain the water
conditions for the benefit of the lagoonal invertebrates (see
Bamber et al. 1993).  Algicide is occasionally used in
Swanpool to control summer blooms of potentially toxic
blue-green algae.
3.4.4  Information sources used
All likely lagoons in the region were surveyed as part of the
Nature Conservancy Council’s national lagoon survey in
1980-1988 (Little 1985; Seaward 1986; Sheader & Sheader
1987; Barnes 1989).  Detailed reports are available, including
maps of the habitats and species lists.  The data are
summarised by Barnes (1989), Sheader & Sheader (1989)
and Smith & Laffoley (1992), from which the data in this
section were derived.  
Surveys of the smaller ponds in Cornwall were generally
brief (single visits), with little intensive sampling.  However,
extensive data exist for both the Aberthaw and Swanpool
Lagoons, as a result of their histories of study,  including
seasonal and longer-term variations.  Swanpool Lagoon has
been the subject of intensive study since the late 1960s by a
research team based in the University of Bristol (see
Crawford et al. 1979 for descriptive literature).  The
Aberthaw Lagoon, South Glamorgan, has been studied by
Cardiff University, principally for its fish population (see
e.g. Creech 1990), and by Fawley Aquatic Research
Laboratories in 1990-91, who also revisited some of the
Cornish sites (Bamber et al. 1993).  
3.4.5  Further sources of information
A.  References cited
Bamber, R.N., Batten, S.D., & Bridgwater, N.D.  1993.  Design
criteria for the creation of brackish lagoons.  Biodiversity and
Conservation, 2: 127-137.
Barnes, R.S.K.  1988.  The coastal lagoons of Britain: an overview.
Nature Conservancy Council, CSD Report, No. 933.  
Barnes, R.S.K.  1989.  The coastal lagoons of Britain: an overview
and conservation appraisal.  Biological Conservation, 49: 295-313.
Crawford, R.M., Dorey, A.E., Little, C., & Barnes, R.S.K.  1979.
Ecology of Swanpool, Falmouth.  V. Phytoplankton and
nutrients.  Estuarine and Coastal Marine Science, 9: 135-160.
Creech, S.  1990.  The ecology and taxonomy of two European atherinids
(Teleostei: Atherinidae).  PhD Thesis, University College of Wales,
Cardiff.
Little, C.  1985.  Coastal saline lagoons in Cornwall.  Nature
Conservancy Council, CSD Report, No. 601.
Seaward, D.R.  1986.  Survey of coastal saline lagoons.  Somerset
and north Devon.  Nature Conservancy Council, CSD Report,
No. 754.
Sheader, M., & Sheader, A.  1987.  Lagoon survey of Avon and
Gloucestershire (Weston-super-Mare to Gloucester), July 1987.
Peterborough, Nature Conservancy Council.
Sheader, M., & Sheader, A.  1989.  The coastal saline ponds of England
and Wales: an overview.  Peterborough, Nature Conservancy
Council.  (Contract Surveys, No. 1009.)
Smith, B.P., & Laffoley, D.  1992.  A directory of saline lagoons and
lagoon like habitats in England. Peterborough, English Nature.
B.  Further reading
Further details of coastal habitat sites are available on the Coastal &
marine UKDMAP datasets module disseminated by the JNCC (Barne
et al. 1994).  Further details of lagoons and quasi-lagoonal features
are available on the UKDMAP datasets module disseminated by the
British Oceanographic Data Centre (BODC 1992).
Al-Suwailem, A.M.  1992.  The ecology of a saline lagoon in southern
England. PhD Thesis, Department of Oceanography, University
of Southampton.
Bamber, R.N., Batten, S.D., & Bridgwater, N.D.  1992.  On the
ecology of brackish water lagoons in Great Britain.  Aquatic
Conservation: Marine and Freshwater Ecosystems, 2: 65-94.
Barne, J., Davidson, N.C., Hill, T.O., & Jones, M.  1994.  Coastal and
marine UKDMAP datasets: a user manual.  Peterborough, Joint
Nature Conservation Committee.
British Oceanographic Data Centre.  1992.  United Kingdom digital
marine atlas.  User guide.  Version 2.0.  Birkenhead, Natural
Environment Research Council, British Oceanographic Data
Centre.
Little, C.  1986.  Lagoon types in Cornwall.  Porcupine Newsletter, 3:
166-169.
Seaward, D.  1986.  NCC survey of coastal saline lagoons in Dorset,
Devon and Somerset.  Porcupine Newsletter, 3: 164-165.
C.  Contact names and addresses
Type of information
Contact address and telephone no.
Brackish lagoons of the
Dr R.S.K. Barnes, St. Catharine’s
region
College, University of Cambridge,
Cambridge  CB2 1RL,
tel: [phone]
Brackish lagoons
Dr M. Sheader, Department of
Oceanography, University of
Southampton, Southampton
SO9 5NH, tel: [phone]
Lagoons in England 
*Maritime Team, English Nature
HQ, Peterborough,
tel: [phone]
Lagoonal species in Cornwall Cornish Biological Records Unit
(CBRU), Trevithick Centre,
Trevenson Road, Pool, Redruth,
Cornwall  TR15 3PL,
tel: [phone]
Lagoonal species in Devon
*M. Camplin, Devon Wildlife
Trust, Exeter, tel: [phone]
*Starred contact addresses are given in full in the Appendix.
3.4  Coastal lagoons
53

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