Lower Fal & Helford Intertidal

Also within

Cornwall County Cornwall Scenic Area King Charles Way - Penzance to St Mawes National TrailKing Charles Way - St Mawes to Cremyll National TrailSouth West Coast Path National Trail

Condition (Natural England)

Unit	Feature	Condition	Area (ha)	Assessed
SW709260	—	Favourable	128.39	2013-09-09
SW711261	—	Favourable	128.39	2013-09-09
SW715251	—	Favourable	128.39	2013-09-09
SW717253	—	Favourable	128.39	2013-09-09
SW719259	—	Favourable	128.39	2013-09-09
SW721255	—	Favourable	128.39	2013-09-09
SW736273	—	Favourable	128.39	2013-09-09
SW738261	—	Favourable	128.39	2013-09-09
SW746267	—	Favourable	128.39	2013-09-09
SW756263	—	Favourable	128.39	2013-09-09
SW758269	—	Favourable	128.39	2013-09-09
SW762262	—	Favourable	128.39	2013-09-09
SW771249	—	Favourable	47.07	2013-09-09
SW771271	—	Favourable	47.07	2013-09-09
SW778261	—	Favourable	47.07	2013-09-09
SW779252	—	Favourable	47.07	2013-09-09
SW780270	—	Favourable	47.07	2013-09-09
SW784255	—	Favourable	47.07	2013-09-09
SW785257	—	Favourable	47.07	2013-09-09
SW786257	—	Favourable	47.07	2013-09-09
SW787257	—	Favourable	47.07	2013-09-09
SW824342	—	Favourable	15.02	2013-09-09
SW838329	—	Favourable	15.02	2013-09-09
SW845318	—	Favourable	7.95	2013-09-09
SW846310	—	Favourable	7.95	2013-09-09
SW846313	—	Favourable	7.95	2013-09-09
SW847322	—	Favourable	7.95	2013-09-09
SW848310	—	Favourable	7.95	2013-09-09
SW849309	—	Favourable	7.95	2013-09-09
SW850309	—	Favourable	7.95	2013-09-09
SW852323	—	Favourable	65.08	2013-09-09
SW860345	—	Favourable	65.08	2013-09-09
SW861333	—	Favourable	65.08	2013-09-09
SW862345	—	Favourable	65.08	2013-09-09

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Habitats

Coastal vegetated shingle, Fast flowing river and stream

Geology & landscape

Rock Type: Shale

Landscape processes: Coastal

Description

Lower Fal and Helford Intertidal SSSI Description The site encompasses sections of the shores of the Fal estuary, most of the Percuil estuary and most of the tidal portion of the Helford River. Sections of the Fal and the outer part of the Helford River provide excellent examples of a range of rocky shore types. A range of wave exposures, variations in geology, tidal streams and aspect gives variety to the shore communities which occur. These grade from robust limpet and barnacle dominated rock surfaces on many headlands, to dense brown algal cover in the more sheltered sections. Sediments vary from open shore coarse mixed mud and sands to fine soft muds which are typical of upper estuarine conditions. Within this range of sediment types rich communities of burrowing polychaete worms, bivalve molluscs and echinoderms are present, varying according to sediment grade and salinity. The Fal Estuary and Helford River together form an example of a ria (drowned river valley) system and support communities representative of those occurring in enclosed marine waters in south-western Britain. Rias have only a low freshwater input, and the area therefore contains a diversity of fully marine habitats, including a range of typically south-western species. The steep-sided ria of the Fal has extensive areas of shallow sediment banks either side of a sinuous main channel. It is characterised by very slow tidal currents in most areas. Downstream of Turnaware Point the ria opens out into the Carrick Roads which is a wide largely subtidal inlet fringed by rocky shores. Areas of intertidal flats are found predominantly within tributaries, particularly the Percuil River. A number of species more typical of open coasts are able to penetrate into the lower reaches contributing to the richness of intertidal communities. The Helford is fairly narrow, widening at the entrance, with a number of relatively short, narrow and steeply-sided branches and creeks. The upper reaches are extremely silted such that at low tide up to four kilometres of the upper reaches dry out apart from a narrow channel which drains freshwater streams into the creeks. In the middle and lower reaches the fringing intertidal is generally a narrow strip of rocky shores with areas of sedimentary and mixed substratum habitats. Percuil River: This is the most significant inlet of interest in the Fal, grading from rocky shores in the outer section to extensive areas of sediment in the upper sections. Rocky shores are represented by sections from west of Newtown Farm to Castle Point and from Zone Point to Amsterdam Point. Within a small distance (around two kilometres) a great change in wave exposure occurs. The section from Zone Point to Carricknath Point consists of steep vertically bedded strata. The strata dip in an easterly direction, parallel with the shore, such that overhangs and vertical steps face the prevailing wave action. Smooth areas of midshore rock are dominated by limpets and barnacles, with rich lower shore overhangs, including many typically sublittoral species such as the seasquirt Clavellina lepadiformis. There are many midshore pools, some large and deep. Such pools have rich communities of algae including a variety of south-western species such as Red grape weed Gastroclonium ovatum and little bushy wrack Cystoseira tamariscifolia. North-east of Carricknath Point the shoreline changes in character. Facing north-west, it is sheltered from wave action and is dominated by fucoid brown algae, typically egg wrack Ascophyllum nodosum. This represents the sheltered algal dominated rocky shores which are so characteristic of the south-western rias. Rocky shores to the north of the Percuil, between Castle Point and west of Newton Farm are, in the main, more gently sloping than those of St Anthony Head. They consist of a mosaic of plant and animal communities, predominantly limpet/barnacle and fucoid brown algae on the midshore, with rich serrated wrack Fucus serratus dominating the lower shore. Additional interest is provided by the presence of stable boulders on the lower shore which harbour rich communities. Characteristic species include cushion starfish Asterina gibbosa, star ascidians Botryllus schlosseri and a range of sponges. The sediment shore communities exhibit distinct zonation in relation to various environmental factors. In fully marine conditions at the mouth of the Fal the sheltered sand habitat is very rich. A number of species are only found on the shores of the Fal at Amsterdam Point including species of amphipods, polychaete worms, bivalves and sea cucumber Paraleptopentacta elongata. Other species characterising this area include the sand mason worm Lanice conchilega, the razor shell Ensis arcuatus and the burrowing heart urchin Echinocardium cordatum. Many other species are only found around St Mawes within the Fal system and include those with a preference for sand subject to high salinity, for example the brittle stars Ophiura ophiura and Acrocnida brachiata. Those in the muddier sediments of Place Cove include polychaete worms such as Myxicola infundibulum and Sabella pavonina and bivalves such as the carpet shell Venerupis senegalensis and the razor shell Ensis arcuatus. West of Amsterdam Point the presence of sheltered rocky platform and boulders, as well as sand, adds to the diversity of intertidal habitats in St Mawes inlet. The red seaweed sand binder Rhodothamniella floridula is common on the lower shore where rock changes to sand with luxuriant growth further up the shore, whilst in Pelyn Creek an unusual unattached form of the egg wrack Ascophyllum nodosum is present. Further variety is given by the transition upstream of sediment communities which are more typical of reduced salinity, including muddy shores characterised by polychaete worms and the peppery furrow shell Scrobicularia plana and, towards the extreme upper reaches, by the ragworm Hediste diversicolor and oligochaete worms. Fal rocky shore: The western section of Fal shoreline, between Penarrow Point and Trefusis Quay adds further interest. The southern part of this area is wave exposed rock, predominantly with typical limpet and barnacle communities. Numerous rock pools occur in the mid and lower shore, dominated by a range of coralline algae, including crustose forms common coral weed Corallina officinalis, and a south-western species pink plates Mesophyllum lichenoides. Towards Penarrow Point, wave exposure is reduced, but tidal currents result in an extremely rich mid and lower shore, with a dense turf of red and brown algae, with sponges and anemones. A wide variety of algae occur, including many which have a distribution limited to the south-west, including red grape weed Gastroclonium ovatum, dulse Palmaria palmata, bunny-eared bead weed Lomentaria articulata, bonnemaison’s hook weed Bonnemaisonia hamifera. With these are found the sponges Sycon ciliatum, Leucosolenia botryoides, Halichondria panicea and Hymeniacidon perleve and the anemones Actinia equina, Anemonia viridis and Sagartia elegans. Helford Rover and Gillan Creek: The Helford is notable as a natural physiographic feature, representing the range of communities which are present in an estuary from the limit of saline influence out to the open coast at the mouth. There are extensive areas of intertidal sediment, predominantly mud flats in the upper estuary and muddy sands in the lower reaches. Major areas of sandier sediment are present at Gillan Harbour, Flushing Cove, Treath, Helford Point and Helford Passage. These flats are extremely rich in both burrowing and surface fauna including the peacock worm Sabella pavonina and other polychaetes, and the cockle Cerastoderma edule. Extensive areas of sediment flats occur at the Bar round to Passage Cove, and on the opposite shore around Helford Point. At the Bar these range from sandy mud to coarse gravel and pebbles. A wide variety of seaweeds occur attached to the pebbles including long wart weed Gracilaria gracilis longissima, banded pincer weed Ceramium virgatum and siphon weed Polysiphonia elongata whilst the fauna is less diverse and dominated by polychaete worms such as the sand mason Lanice conchilega, and hermit crabs. In Passage Cove there is an equally high diversity of seaweeds but with some fauna associated with the more abundant pebbles including the chinaman’s hat Calyptraea chinensis and the brittle star Ophiothrix fragilis. Burrowing animals are limited and include capitellid worms and the mollusc Lucinoma borealis. Shale and shingle shores are present up the river, often replaced by deep mud towards low water, including at Merthen Wood, Groyne Point, Frenchman’s Creek and Calmansack. There is seaweed cover on these shores including channel wrack Pelvetia canaliculata, spiraled wrack Fucus spiralis and bladder wrack Fucus vesiculosus and egg wrack Ascophyllum nodosum. On the upper shore the seaweeds Bostrychia scorpioides and creeping chain weed Catenella caespitosa are unusually abundant. The fauna on such shores is often limited with only the shore crab Carcinus maenas, mussels Mytilus edulis and the barnacle Austrominius modestus being widespread. Downstream of Merthen Wood the fauna also includes gastropods such as Littorina littorea and L. obtusata, the barnacle Semibalanus balanoides. Of note is an area of mixed shale shingle with mud on the lower shore between Helford Point and Frenchman’s Creek with a rich community of massive sponges Hymeniacidon perleve and the tube worm Sabella pavonina. There are rocky shore habitats throughout the ria but particularly in the outer reaches. At Padagarrack Cove smooth sloping bedrock outcrops adjacent to sand on the lower shore. The red seaweed Audouniella is abundant together with a variety of species typical of the sand-rock interface including Chondracanthus acicularis and hairy basket weed Spyridia filamentosa. Extensive intertidal reefs are present at Men-aver and Nare Point. Because they are rugged, and gently sloping with numerous gullies and vertical faces, they offer a wide range of habitats, from wave exposed open surfaces to sheltered, shaded gully walls. This encourages an enormous variety of plants and animals. A notable feature of many of the rocky shores are rock pools on the lower mid and lower shore. These have extremely rich seaweed communities, supporting abundant growth of bushy wracks Cystoseira spp., slender-beaded coral wrack Jania rubens, common coral weed Corallina officinalis, Dumont’s tubular weed Dumontia contorta and pink plates Mesophyllum lichenoides. A number of these seaweeds are southern species. Throughout the lower reaches rocky overhangs on the lower shore support a community that includes sponges, barnacles, top shells, the cushion star Asterina gibbosa, anemones and seaweeds such as spiny straggle weed Gelidium spinosum (latifolium), dulse Palmaria palmata, grape pip weed Mastocarpus stellatus and club bead weed Lomentaria clavellosa. Rich animal communities are also associated with boulders at Padagarrack Cove and south of Rosemullion Head, and include the barnacle Verruca stroemia, the broad-clawed porcelain crab Porcellana platycheles and the sea urchin Psammechinus miliaris. Rocky shores in the middle part of the river harbour populations of Couch’s goby Gobius couchi known from very few sites in Britain. Towards the limit of tidal influence, at the head of many creeks, rocky upper shores are dominated by brown algae, typically the egg wrack Ascophyllum nodosum, with other species more characteristic of lowered salinity such as the bryozoan Amathia imbricata.

Species mentioned

Show the 60 species mentioned in the description, with red-list status ▾

Plant communities