Skip to Content

Special Areas of Conservation

1170 Reefs

Marine, coastal and halophytic habitats

Description and ecological characteristics

Reefs are rocky marine habitats or biological concretions that rise from the seabed. They are generally subtidal but may extend as an unbroken transition into the intertidal zone, where they are exposed to the air at low tide. Intertidal areas are only included within this Annex I type where they are connected to subtidal reefs. Reefs are very variable in form and in the communities that they support. Two main types of reef can be recognised: those where animal and plant communities develop on rock or stable boulders and cobbles, and those where structure is created by the animals themselves (biogenic reefs).

Rocky reefs are extremely variable, both in structure and in the communities they support. A wide range of topographical reef forms meet the EU definition of this habitat type. These range from vertical rock walls to horizontal ledges, sloping or flat bed rock, broken rock, boulder fields, and aggregations of cobbles. Reefs are characterised by communities of attached algae (where there is sufficient light – on the shore and in the shallow subtidal) and invertebrates, usually associated with a range of mobile animals, including invertebrates and fish. The specific communities that occur vary according to a number of factors. For example, rock type is important, with particularly distinct communities associated with chalk and limestone. There may be further variety associated with topographical features such as vertical rock walls, gully and canyon systems, outcrops from sediment, and rockpools on the shore.

The greatest variety of communities is typically found where coastal topography is highly varied, with a wide range of exposures to wave action and tidal streams. Exposure to wave action has a major effect on community structure, with extremely exposed habitats dominated by a robust turf of sponges, anemones and foliose red seaweed, while reefs in the most sheltered sea lochs and rias support delicate or silt-tolerant filamentous algae, fan-worms, ascidians and brachiopods. The presence of enhanced tidal streams often significantly increases species diversity, although some communities require very still conditions. The strength of tidal streams varies considerably, from negligible in many sea loch basins, to very strong at 8-10 knots (4-5 m s-1) or more through tidal rapids or in sounds. In strong tidal streams there are communities of barnacles, the soft coral Alcyonium digitatum, massive sponges and hydroids.

In addition, in the UK there is a marked biogeographical trend in species composition related to temperature, with warm, temperate species such as the sea-fan Eunicella verrucosa and the corals Leptopsammia pruvoti and Balanophyllia regia, occurring in the south, and cold-water species, such as the anemone Bolocera tuediae and the red seaweed Ptilota plumosa, in the north. A major factor affecting reef communities is the turbidity of the water. In turbid waters, light penetration is low and seaweeds can occur only in shallow depths or in the intertidal zone. However, in such conditions animals have a plentiful supply of suspended food and filter-feeding species may be abundant. Salinity is also important. Although most reefs are fully marine, rocky habitats in certain marine inlets are subject to variable or permanently reduced salinities and support their own distinctive communities.

A strong vertical zonation is apparent. In the intertidal zone, lichens occur at the top of the shore, with littoral biotopes characterised by barnacles, mussels or species of fucoid (wrack) seaweeds. Vertical zonation extends subtidally into the circalittoral (below the photic zone).

In contrast to the variety of rocky reefs, there is somewhat less variation in biogenic reefs, but the associated communities can vary according to local conditions of water movement, salinity, depth and turbidity. The main species which form biogenic reefs in the UK are blue mussels Mytilus edulis, horse mussels Modiolus modiolus, ross worms Sabellaria spp., the serpulid worm Serpula vermicularis, and cold-water corals such as Lophelia pertusa.

Reefs are often associated with other marine Annex I habitats, and may also grade into 1230 Vegetated sea cliffs of the Atlantic and Baltic coasts on the coast.

Distribution of SACs/SCIs/cSACs with habitat 1170 Reefs. Click image for enlarged map.

European status and distribution

Reefs are widespread around the coasts of Europe, although particular types are more restricted in their distribution. Some types, such as chalk reefs, are more abundant in the UK than elsewhere in the EU.

UK status and distribution

Reefs occur widely around the UK coast, and are found in both inshore and offshore waters. There is a far greater range and extent of rocky reefs than biogenic concretions. Only a few invertebrate species are able to develop biogenic reefs, and these have a restricted distribution and extent in the UK.

Click here view UK distribution of this species

Site accounts

  • Anton Dohrn Seamount Extra-Regio
    Anton Dohrn Seamount houses hard bedrock reef of low topographic complexity, stony reef, and biogenic Lophelia pertusa reef in the deep circalittoral to bathyal zone (~500-1000m). Bedrock and boulder reef habitat on the seamount flanks support assemblages of holothurians, brittlestars, encrusting sponges, caryophyllid corals and lamellate sponges. Bedrock reef on parasitic cones and radial ridges supports relatively dense aggregations of gorgonians, antipatharians, Lophelia pertusa and soft corals. Biogenic reef is formed by live Lophelia pertusa reef and sediment in-filled dead L. pertusa frameworks.
  • Berwickshire and North Northumberland Coast Eastern Scotland, Extra-Regio, Northumberland and Tyne and Wear
    This site is an extensive and diverse stretch of coastline in north-east England and south-east Scotland. Moderately wave-exposed reef habitats occur throughout the site. The subtidal rocky reefs and their rich marine communities, together with the wide variety of associated littoral reefs, are the most diverse known on the North Sea coast. Their remarkably varied nature is due to the wide range of physical conditions in the area, from wave-exposed locations on the open coast, through more sheltered reefs within bays, to those exposed to strong tidal streams in sounds and off headlands. There is also a diverse range of rock types, including soft limestones and hard volcanic rock. The Farne Islands are of special importance as they are among the very few rocky islands with extensive reefs in the enclosed North Sea. A large number of the species present are characteristic of cold water and several reach their southern or eastern limit of distribution within the area.
  • Darwin Mounds Extra-Regio
    The Darwin Mounds is an extensive area of sandy mounds formed by seabed fluid expulsion, each of which is capped with multiple thickets of Lophelia pertusa, a cold-water coral. These thickets qualify as Annex I Reef according to the European Commission interpretation (CEC, 2007). The number of thickets vary per mound and may be between one and several metres wide and high. Hundreds of mounds lie within the site but two particularly dense fields of mounds are present to the north east and north west limit of the area (Bett, 2001). Each of the mounds is approximately 100m in diameter and 5m high, and distinguished by a 'tail' feature visible on sidescan sonar. The mounds support significant populations of the xenophyophore Syringammina fragilissima (a 15 cm diameter single celled organism) that is widespread in deep waters, but occurs in particularly high densities on the mounds and the tails (Bett, 2001).The occurrence of Lophelia pertusa reef as thickets capping sandy mounds is believed to be unique due to the particular geological processes which formed the mounds and the fact that the coral is growing on sand rather than a hard substratum (Masson et al, 2003). The individual reefs on each mound provide a habitat for various species of larger invertebrates such as sponges and brisingiid starfish.
  • East Mingulay Extra-Regio
    The reef areas to the east of Mingulay in the Outer Hebrides are found within a wide trench in the seabed at depths of about 100 to 250 metres. Nine reef areas have been identified, formed by characteristic mounds on the seabed up to 150 metres high. An area of approximately 26 square kilometres supports reef habitat, including both biogenic and non-biogenic (rocky) reefs. The biogenic reefs, covering an area of about 5.4 square kilometres, are formed of the cold-water coral, Lophelia pertusa. Although L. pertusa is the main reef-forming coral in the northeast Atlantic and as a species is thought to be widespread, it rarely forms reef complexes in inshore waters (within 12 nautical miles of the coast). In fact, East Mingulay is unique in that it is currently the only known area with extensive cold-water coral reefs within UK territorial waters. Most of the East Mingulay Lophelia pertusa reefs form typical biogenic masses that host a large variety of associated species. The remaining reef areas within the site boundary include a rich mix of habitats and species developed on dead coral, boulders, and rocky and cobbly reef structures. Surveys of the East Mingulay reef complex have identified over 400 species, including a sponge Cliona caledoniae which was new to science (Van Soest and Beglinger, 2008).
  • East Rockall Bank Extra-Regio
    East Rockall Bank houses bedrock, stony and cold water coral biogenic reef in the deep circalittoral to bathyal zone. Bedrock and stony reef supports assemblages of stylasterid lace corals and lobose sponges. Parasitic cones in the north of the site support sediment in-filled dead L. pertusa framework and live cold water coral reef, with antipatharians and gorgonians. Two canyon features cut into the flanks of the site and these are characterised by xenophyophores and decapod shrimps, with one canyon also supporting an abundance of caryophyllid corals and sea pens.
  • Firth of Lorn Extra-Regio, Highlands and Islands
    This well-defined, discrete area encompasses a complex group of islands, sounds and inlets characterised by some of the strongest tidal streams in the UK. The area is moderately exposed to wave action with very sheltered pockets enclosed by islands and skerries. Reefs extend from the shallow depths between the islands and mainland into depths of over 200 m, in many places close inshore. The varied physical environment is reflected in the variety of reef types and associated communities and species, which are amongst the most diverse in both the UK and Europe. These range from those characteristic of conditions sheltered from waves and currents, to those influenced by extreme tidal streams. A rapid transition in communities occurs with the deceleration of the tidal streams. Species present include some which are normally characteristic of deeper water (the sponges Mycale lingua and Clathria barleii, and the featherstar Leptometra celtica), and others which are considered scarce (including the brown alga Desmarestia dresnayi). Many species occurring here have either a northern or southern-influenced distribution and reach their geographic limits in this area, for example, the southern cup-coral Caryophyllia inornata, the nationally scarce brittlestar Ophiopsila annulosa, and the northern bryozoans Bugula purpurotincta and Caberea ellisii.
  • Flamborough Head East Yorkshire and Northern Lincolnshire, North Yorkshire
    Flamborough Head has been selected for the presence of species associated with the chalk and for the site’s location at the southern limit of distribution of several northern species. It lies close to the biogeographic boundary between two North Sea waterbodies and encompasses a large area of hard and soft chalk on the east coast of England. The site covers around 14% of UK and 9% of European coastal chalk exposure, represents the most northern outcrop of chalk in the UK, and includes bedrock and boulder reefs which extend further into deeper water than at other subtidal chalk sites in the UK, giving one of the most extensive areas of sublittoral chalk in Europe. The reefs and cliffs on the north side of the headland are very hard, resulting in, for example, the presence of many overhangs and vertical faces, a feature uncommon in sublittoral chalk. The clarity of the relatively unpolluted sea water and the hard nature of the chalk have enabled kelp Laminaria hyperborea forests to become established in the shallow sublittoral. The reefs to the north support a different range of species from those on the slightly softer and more sheltered south side of the headland. The site supports an unusual range of marine species and includes rich animal communities and some species that are at the southern limit of their North Sea distribution, e.g. the northern alga Ptilota plumosa. For these reasons, the sublittoral and littoral reef habitats at Flamborough are considered to be the most diverse in the UK.
  • Haig Fras Extra-Regio
    Haig Fras is an isolated, fully submarine bedrock outcrop located in the Celtic Sea, 95 km northwest of the Isles of Scilly. It is the only substantial area of rocky reef in the Celtic Sea beyond the coastal margin. It supports a variety of fauna ranging from jewel anemones and Devonshire cup coral near the peak of the outcrop to encrusting sponges, crinoids and ross coral towards the base of the rock (where boulders surround its edge) (Rees, 2000). There are four main habitat complexes; high energy circalittoral rock, moderate energy circalittoral rock, deep circalittoral coarse sediment and deep circalittoral sand. The total area of reef feature within the site boundary is approximately 175 km2. The rock type is granite, mostly smooth with occasional fissures. The rocky outcrop is approximately 45 km long and in one area rises to a peak which lies just 38 m beneath the sea surface (Rees, 2000, Barrio Froján et al., 2015). The surrounding seabed is approximately 118 m deep, with small dispersed patches of rocky outcropping within circalittoral sand and coarse sediment (Barrio Froján et al., 2015).
  • Haisborough, Hammond and Winterton Extra-Regio
    Sabellaria spinulosa reefs are located at Haisborough Tail, Haisborough Gat and between Winterton Ridge and Hewett Ridge. They arise from the surrounding coarse sandy seabed to heights of between 5cm to 10cm. The reefs are consolidated structures of sand tubes showing seafloor coverage of between 30 per cent to areas where reef occupies 100 per cent of the sediment. Some parts of the reefs appear to be acting as sediment traps, with exposed tube height accordingly reduced within the core parts of reefs.
  • Hatton Bank Extra-Regio
    Hatton Bank is a large volcanic bank, situated in the Atlantic North-West Approaches, towards the western extent of the UK Continental Shelf. The vast size and topographic complexity of the Hatton Bank supports a wide diversity of biological communities, each associated with different geomorphological structures and substratum types. The bank supports extensive areas of bedrock reef (particularly on the ridges along the top of the bank) and stony reef. Also present are elaborate cold water coral reefs, frequently associated with topographically distinct features, including pinnacles and mounds tens of metres in height and hundreds of metres in width.
  • Inner Dowsing, Race Bank and North Ridge Extra-Regio
    Abundant Sabellaria spinulosa agglomerations have consistently been recorded within the boundary of the cSAC (Foster-Smith & Hendrick, 2003). Survey data indicate that reef structures are concentrated in certain areas of the site, with a patchy distribution of crust-forming aggregations across the site. The main areas of S. spinulosa reef are found along the Lincolnshire coast south of Skegness at Lynn Knock and Skegness Middle Ground (south-east part of the site); just north of Docking Shoal bank; and associated with the southern edge of Silver Pit (in the northern area of the site) (Woo, 2008; Foster-Smith & Hendrick, 2003; Brutto, 2009; Limpenny et al, 2010).
  • Isles of Scilly Complex Cornwall and Isles of Scilly
    The Isles of Scilly are surrounded by reefs and rocky islets, some only extending into the shallow sublittoral, others extending well beyond 50 m depth. The location of the islands, exposed to the full force of the Atlantic, leads to the development of extremely exposed communities on west-facing reefs, whilst on the east-facing coast, more sheltered and silted reefs occur. The south-westerly position of the islands leads to a range of warm-water species being present, including sunset cup-coral Leptopsammia pruvoti, pink sea-fans Eunicella verrucosa, and Weymouth carpet-coral Hoplangia durotrix.
  • Lands End and Cape Bank Extra-Regio
    Closely associated with the main area of offshore upstanding rocky reefs within the Lands End and Cape Bank pSAC are isolated upstanding rocky reef pinnacles to the east and south. These isolated reefs appear to be as topographically complex and as biodiverse as those in the main area of upstanding rocky reef. Much of the coastal margin deepens to 30 m within a kilometre or two of the shore. It includes areas of sand which stretch out from the major bays and as patches between rock outcrops. The resistant headlands and islands are formed of a variety of rock types including granite, metamorphic and volcanic rocks which also form a fringing reef system. The site’s south westerly position on the British coast means that the sub-littoral zone is exposed to the full force of the waves and oceanic swells coming in from the Atlantic, as well as experiencing full salinity, given the absence of any major source of fresh water run off from the land. The offshore upstanding rocky reefs areas are the most biodiverse of all rocky reef habitats within the site.
  • Lizard Point Extra-Regio
    Lizard Point is unique in terms of its underlying geology, with no other existing SAC in the surrounding area offering such a variety of bedrock origins. The Lizard Point site consists of rugged inshore and offshore areas of submerged bedrock and boulders of complex geological origin, separated by extensive areas of thin, coarse mobile sediment covering flat sedimentary bedrock to the south and east, and the flat metamorphic bedrock to the west. There are two areas of upstanding offshore reef extending from approximately 3.5 to 9 km offshore and extending down to depths of 80 m in some areas.
  • Loch Creran Extra-Regio
    Loch Creran, situated at the northern end of the Firth of Lorn, is a typical fjordic sea loch. The site is particularly notable for biogenic reefs of the calcareous tube-worm Serpula vermicularis, which occur in shallow water around the periphery of the loch. This species has a world-wide distribution but the development of reefs is extremely rare; Loch Creran is the only known site in the UK to contain living S. vermicularis reefs and there are no known occurrences of similarly abundant reefs in Europe. Biogenic reefs of the horse mussel Modiolus modiolus, also confined to the shallow sublittoral, occur in the upper basin of the loch. The biogenic reefs increase habitat complexity and are colonised by an abundant and diverse faunal assemblage, including bryozoans, ascidians and sponges. Localised areas of bedrock reef, which support further species-rich assemblages, are also included within the site.
  • Lochs Duich, Long and Alsh Reefs Extra-Regio, Highlands and Islands
    This site is an extensive area of extremely sheltered reefs within a system of fjordic sea lochs in north-west Scotland. There is considerable diversity within the site, with areas of sheltered sublittoral rock supporting unusual assemblages of encrusting sponges and solitary ascidians, and, on shallower reefs, tide-swept kelp forests influenced by brackish water. Loch Duich is particularly notable for its well-developed communities of brachiopods and sea anemones on sheltered bedrock. Characteristic species include the sea anemone Protanthea simplex, the fan-worm Sabella pavonina, and the brachiopods Neocrania anomala and Terebratulina retusa. The reefs in Kyle Rhea and Kyle Akin are subject to some of the strongest tidal streams in the UK, and the bedrock in Kyle Rhea supports rich communities typically dominated by the hydroids Tubularia indivisa and Sertularia argentea, the barnacle Balanus crenatus, anemones, sponges and ascidians. Tide-swept reefs in Loch Alsh also support unusually dense beds of the brittlestar Ophiopholis aculeata, an extremely rare feature in the UK. The sheltered reefs in Loch Long, the second most brackish of the large Scottish sea lochs, are unusual in that they are subject to variable salinities and support communities characterised by encrusting sponges and large numbers of ascidians, such as Ascidia virginea, Boltenia echinata and Pyura squamulosa.
  • Lundy Devon
    Lundy is a granite and slate reef system and is selected for its outstanding representation of reef habitats in south-west England. Lundy Island is exposed to a wide range of physical conditions as a result of differing degrees of wave action and tidal stream strength on sheltered and exposed coasts and headlands. This range of physical conditions, combined with the site’s topographical variation, has resulted in the presence of a unusually diverse complex of marine habitats and associated communities within a small area. The reefs of Lundy extend well over 1 km offshore and drop steeply into deep water in some areas. The variety of habitats and associated species on the reefs is outstanding and includes, for example, a large number of seaweeds and many rare or unusual species, including Mediterranean-Atlantic species representing biogeographically distinct communities at, or very close to, their northern limit of distribution. In particular, fragile long-lived species, such as the soft coral Parerythropodium coralloides, sea-fan Eunicella verrucosa and a variety of erect branching sponges, are found in deep, sheltered conditions, particularly on the east coast of the island. All five British species of cup-coral are found here, including the scarlet and gold star-coral Balanophyllia regia and the sunset cup-coral Leptopsammia pruvoti.
  • Lyme Bay and Torbay Extra-Regio
    This site is situated mostly within the Western English Channel and Celtic Regional Sea and lies off the south coast of England off the counties of Dorset and Devon. The site comprises of two main areas containing Annex I ‘reef’ and ‘sea cave’ habitat. The reef features extend over a large area. Unlike other sites within the Lyme Bay and Torbay site, they do not extend directly out from the coast but occur as outcropping bedrock slightly offshore. The softer sediment habitats are commonly found between the bedrock or cobble / boulder areas. Examples of the classical wave-eroded sea caves are found at all the sites of different levels and rock types.The site is indicative of offshore reef and has particularly high species richness and identified it as a marine biodiversity “hot spot.
  • North Norfolk Sandbanks and Saturn Reef Extra-Regio
    The Saturn Sabellaria spinulosa biogenic reef, first discovered in 2002, consists of thousands of fragile sand-tubes made by ross worms (polychaetes) which have consolidated together to create a solid structure rising above the seabed (BMT Cordah, 2003). This structure qualifies as Annex I Reef according to European Commission interpretation (CEC, 2007). In 2003, the Saturn reef covered an area approximately 750m by 500m just to the south of Swarte Bank, varying in density over this area (BMT Cordah, 2003).
  • North West Rockall Bank Extra-Regio
    Rockall Bank is an offshore bank situated in the North East Atlantic, approximately 400 kilometres west of the Outer Hebrides. It is oriented northeast to southwest, and is approximately 450 kilometres in length and 200 kilometres wide (Howell et al., 2009). Depth ranges from over 1000m at the base of the Rockall Bank, to 200m across much of the top. The centre of the bank breaks the surface forming a rocky island outcrop around 25 metres wide and 20 metres high. On account of their sheer size, oceanic banks such as Rockall cause the deviation of ocean currents along their flanks. This facilitates the colonization of habitat-forming corals which depend on a consistent supply of current-transported organic matter and zooplankton (Freiwald et al., 2004). Rockall Bank is potentially one of the most extensive sites for biogenic reef formed by cold water coral species in UK waters. Inter-dispersed with the stony reef are sizeable patches of Annex I Lophelia pertusa reef and associated species, including erect sponges and the pencil urchin Cidaris cidaris. Stands of Madrepora oculata, another cold water coral species, are also present (Howell et al., 2009). Evidence from the 1970s suggests that areas of Lophelia pertusa reef up to 30m in diameter existed on the North West Rockall Bank (Wilson, 1979; Davies and Roberts, 2006), though more recent surveys (albeit at different locations in this region) have recorded reefs smaller in size (Howell et al., 2009). Cobble rubble surrounds the living reefs in many places, and supports fauna such as the squat lobster Munida rugosa, the holothurian Stichopus tremulus, brittle stars and encrusting yellow sponges.
  • Papa Stour Extra-Regio, Highlands and Islands
    Papa Stour is an example of very exposed reefs on hard rocks in the extreme north of Scotland. The rocky coastline of Papa Stour is among the most exposed in the UK, and the island and the adjacent mainland are fringed entirely by sublittoral bedrock and boulder reefs reaching depths of more than 30 m. The underwater terrain is rugged, with rock walls, slopes, gullies, ledges, ridges and boulder slopes, which support a diverse range of plant and animal communities. The extensive kelp forests on these reefs have a rich associated algal community at shallow depths because wave action prevents grazing by sea-urchins in some exposed areas. Kelp extends to depths of up to 28 m in the clear waters surrounding the island. Communities on circalittoral rock are characteristic of northern parts of the UK, with dominant species including the soft coral Alcyonium digitatum, the featherstar Antedon bifida, encrusting coralline algae, and the serpulid worm Pomatoceros triqueter. Wave-exposed gullies have rich, surge-tolerant communities, with turfs of the jewel anemone Corynactis viridis, ascidians and bryozoans. In the strong tidal streams of the Sound of Papa, boulder reefs and bedrock ridges are dominated by scour-tolerant organisms such as the hydroid Abietinaria abietina and the brittlestar Ophiocomina nigra.
  • Pembrokeshire Marine/ Sir Benfro Forol Extra-Regio, West Wales and The Valleys
    Reefs in this south-west Wales site are largely composed of igneous rock but include areas of more friable Old Red Sandstone and some limestone. Extensive areas of sublittoral rocky reef stretch offshore from the west Pembrokeshire coast and between the Pembrokeshire islands and many small rocky islets. Limestone reefs occur in the south of the site. Reefs also extend through Milford Haven and into the variable salinity conditions of the Daugleddau estuary. Reefs within the site are subject to an exceptional variation in strength of tidal streams and wave exposure. The highly variable rocky seabed topography, together with the indented coastline and extreme tidal range, cause strong tidal streams, particularly around headlands, through sounds and in tidal inlets. The shallower and south-west-facing rocky reefs are exposed to severe wave action, while many others are extremely wave-sheltered. Many of the reefs extend onto the shore and provide examples of both the most exposed and the most sheltered intertidal rock communities in southern Britain. Reef habitat diversity is increased by caves, tunnels and surge gullies in both subtidal and intertidal zones. The wide variation in exposure to water movement, the range of rock type, slope, aspect and topography, and the high water quality, together with local exposure to abrasion from adjacent sediments and reduced salinity in the Daugleddau, are reflected in the wide diversity and species abundance of biological communities. Offshore there are particularly extensive areas of tide-swept kelp and species-rich red algal populations and, across the large areas of deeper rock reef, a wide range and abundance of invertebrate animal communities, with hydroid, bryozoan, soft coral and anemone species. More sheltered reefs, including those in lowered salinity and higher turbidity, typically support diverse and species-rich sponge- and ascidian-dominated communities.
  • Pen Llŷn a'r Sarnau/ Lleyn Peninsula and the Sarnau East Wales, Extra-Regio, West Wales and The Valleys
    This site on the coast of north-west Wales encompasses a varied range of reef habitats, including an unusual series of submerged and intertidal glacial moraines. The areas of bedrock, boulders, cobbles, sandy rock, surge gullies and the tide-swept area of Bardsey Sound support a diverse array of plant and animal communities. There are distinctive communities on bedrock and boulders, ranging from sites exposed to very strong wave action and/or tidal streams to sites sheltered from strong water movement. For example, reefs on the north coast of the Llyn are dominated, in different locations, by either the mussels Musculus discors and Mytilus edulis or horse mussels Modiolus modiolus, or ascidians, or the tube worm Sabellaria spinulosa. Ross coral Pentapora foliacea has been recorded from these reefs and elsewhere around Bardsey and south-west Llyn. Several Mediterranean-Atlantic species have been recorded from south-east Bardsey. Reefs formed by honeycomb worm Sabellaria alveolata are found south and east of Pwllheli. The Sarnau (Sarn Badrig, Sarn-y-Bwch and Cynfelyn Patches) are very unusual shallow subtidal reefs, which extend many kilometres from the coast into Cardigan Bay. The Sarnau are glacial moraines (resulting from the last glaciation) and are composed entirely of boulders, cobbles and pebbles mixed with various grades of sediments. Fast tidal streams and strong wave action have a profound influence on the marine communities present, and the reefs are characterised by a large number of species resistant to scour and sand cover. Algal communities are dominant over much of the reefs, with growths of foliose red and brown algae forming very dense beds in many places, in the absence of shading from kelp. The brown algae Chorda filum and Laminaria saccharina and red algae flourish on or near the reef crest, while the number of algae species on pebbles increases with depth. In certain areas there are extensive forests of sea-oak Halidrys siliquosa. Rich animal-dominated biotopes are found in the deeper parts of the reefs, including crustaceans, cnidarians, sponges, hydroids and encrusting bryozoans.
  • Pisces Reef Complex Extra-Regio
    The Pisces Reef Complex is located in the western Irish Sea, in the north-west mud basin. It is approximately midway between the Isle of Man and the coast of Northern Ireland. The area consists of an extensive mud plain through which three areas of Annex I bedrock and boulder-dominated stony reef protrude. The areas are situated apart from each other at distances of between 5.5 km and 14 km. While the SAC consists of the three reef features, the boundary has been delineated to exclude the areas of muddy sediment in. The average seabed depth within the site boundary is approximately 100 m with a maximum of 134 m and a minimum of 70 m at the peaks of the rocky reef outcrops. The deepest depths are within the scour pits which encircle the outcropping rocky reefs. The three extruding reefs are composed of tertiary igneous rock and boulders. They rise 15-35m above the surrounding seabed. The reef tops are composed of silty bedrock, with a patchy veneer of muddy sediment, due to sediment deposition from a localised scouring process. The reefs themselves support a diverse community of brachiopods, ascidians, hydroids, sponges and fish. In particular, the mosaic of bedrock and stony reef provide a myriad of ledges and habitat niches. Of note is the occurrence of the Diphasia alata hydroid community. It is not currently included within the Marine Habitat Classification for Britain and Ireland, but is considered rare. The difference in species composition and abundance between the reefs and the surrounding mud plain highlights the importance of the reefs in providing a refuge for numerous species. The area of muddy sediment around the rocky reefs supports a major Nephrops norvegicus fishery and a high density of Nephrops burrows has been observed.
  • Plymouth Sound and Estuaries Cornwall and Isles of Scilly, Devon, Extra-Regio
    Plymouth Sound in south-west England has a wide variety of intertidal and subtidal reef biotopes. Of particular importance are the limestone reefs running along the northern shore from West Hoe to Batten Bay, which are one of only two coastal areas in south-west Britain with Devonian limestone. This relatively soft rock is extensively bored by the bivalve Hiatella arctica and the spionid worms Polydora spp., and harbours a rich fauna. In the sublittoral this steep-sided, wave-sheltered reef is dominated by a dense hydroid and bryozoan turf with anemones and ascidians. A number of rarely-recorded low shore biotopes also occur along the shores from Devil’s Point to Batten Bay, at Wembury, Penlee, Hoo Lake Point, and in the mouth of the River Yealm. The sublittoral is of particular importance for its kelp- and animal-dominated habitats. The area off Batten Bay contains the south-western kelp Laminaria ochroleuca, together with other uncommon species including the rare sea slug Okenia elegans and trumpet anemone Aiptasia mutabilis. Most circalittoral rocky reefs occur in areas of the Outer Sound, such as off Wembury, the Mewstone, Penlee Point and south of the breakwater. In the approaches to Plymouth Sound, abundant populations of the slow-growing, long-lived, nationally important pink sea-fan Eunicella verrucosa occur.
  • Pobie Bank Reef Extra-Regio
    Pobie Bank reef’s stony and bedrock reef provides a habitat to an extensive community of encrusting and robust sponges and bryozoans, which are found throughout the site. In the shallowest areas the bedrock and boulders also support encrusting coralline algae. Axinellid cup sponges (Axinella infundibuliformis) are common on the bedrock and stony reef at depth ranges of 70m to over 100m. The bryozoan Omalosecosa ramulosa is also common on these reefs, but this species is rare in inshore sites in this regional sea. In the deepest areas (>100m), low-lying silty bedrock is commonplace, supporting small erect sponges, cup corals (Caryophyllia smithii) and the brittlestar Ophiura albida
  • Rathlin Island Northern Ireland
    Rathlin Island is surrounded by a wide range of rocky habitats and is one of the best examples of reefs in Northern Ireland. Strong tidal streams prevail around most of the island, and there is little silt. As a result, turbidity is generally low, with the infralittoral extending below 20 m depth, and water temperatures are stable, not rising much above 13ºC in the summer. A very wide range of species has been recorded around the island, including a high proportion of species of particular interest. Along the south-west coast there is a very steep slope of large, stable boulders extending below 50 m in places. The boulders support biotopes dominated by Tubularia indivisa in deeper water and by a diverse assemblage of algae in the shallows. A number of species occur that are rare in Northern Ireland, especially those with south-western distributions, such as the sea-cucumber Holothuria forskali, the sponge Axinella damicornis, and the red alga Drachiella spectabilis. The north-west part of Rathlin Island consists of a shallow shelf 10-100 m wide along the base of the cliffs, followed by a vertical underwater cliff which starts at 20-30 m and descends to over 100 m. The cliffs are formed of both limestone and basalt, and support a rich assemblage of sponges and hydroids. Dominant species include Pachymatisma johnstonia, the soft coral Alcyonium digitatum, Dendrodoa grossularia and T. indivisa. To the north-east, the slope offshore is shallower, with the seabed consisting of areas of bedrock interspersed with stable boulder slopes. Sponges are particularly diverse and abundant. In shallow water there are overhangs and surge gullies with characteristic assemblages of species. The circalittoral zone of the east coast is mostly dominated by rich hydroid and sponge-dominated biotopes on bedrock, boulders, and cobbles, amongst coarse gravel. Frequent components of these biotopes are the hydroids Polyplumaria flabellata, Diphasia alata and the sponge Axinella infundibuliformis.
  • Sanday Extra-Regio, Highlands and Islands
    Sanday is a large, low-lying island in the north-east of the Orkney archipelago. Surrounded by clear, relatively shallow water, the island has a complex coastline dominated by extensive sandy beaches and sheltered inlets, interspersed with rocky headlands. Sanday is notable for the extensive subtidal bedrock reefs that surround the island and provide a habitat for dense forests of kelp Laminaria spp. The kelp occurs to a depth of about 20 m and provides a habitat for species-rich, red algal turf communities. Sponges, such as Clathrina coriacea, and ascidians, such as Aplidium punctum, occur on the vertical rock faces. The north coast of Sanday is tide-swept and appears to support a richer fauna than the south coast, with a dense bryozoan/hydroid turf and dense brittlestar and horse mussel Modiolus modiolus beds in mixed sediment below the kelp zone. Crabs and brittlestars are common within crevices in the rock.
  • Shell Flat and Lune Deep Extra-Regio
    Habitat occurrence description not yet available.
  • Skerries and Causeway Extra-Regio
    Habitat occurrence description not yet available.
  • Solan Bank Reef Extra-Regio
    Solan Bank presents highly topographic bedrock and smooth, undulating bedrock reef outcrops and stony reef (comprising boulders and cobbles) in a range of depth zonations from the infralittoral to deep circalittoral and within a range of energy levels with a resulting broad range of ecological communities and faunal diversity. The reefs support encrusting bryozoans, encrusting coralline algae, caryophyllid cup corals and ophiuroids. Highly sediment-scoured bedrock is mainly colonised by the keel worm Pomatoceros triqueter. Less-scoured bedrock support a range of sponges, bryozoans and hydroids. In shallower areas with increased water movement there is an increasing abundance of the soft coral, Alcyonium digitatum, the cup coral, Caryophyllia smithii and the jewel anemone, Corynactis viridis, with red algae and kelp in the shallowest areas.
  • Sound of Barra Extra-Regio, Highlands and Islands
    The Sound of Barra comprises a mixture of islands, extensive rocky reefs, sandbanks and shallow channels in a broad stretch between the southern end of South Uist and the north eastern shore of the island of Barra in the Outer Hebrides, off the west coast of Scotland. The reefs are most extensive in the western areas and, to a lesser extent, in the eastern parts of the Sound. The western part of the Sound is highly exposed with infralittoral rocky substrates dominated by tide-swept kelp forests Laminaria hyperborean communities, with a diverse associated fauna characteristic of accelerated tidal currents. There are also mixed kelp communities including Saccorhiza polyschides and Saccharina latissima in sand scoured areas. The depth in the site increases to the east, where shallower rock substrates also support kelp forests. Deeper rock surfaces are dominated by a turf of foliose red algae mixed with scour tolerant epifauna and with increasing depth there is an increased dominance of invertebrates similar to those of the shallower reefs. The intertidal rocky reefs support communities characteristic of a wide spectrum of exposure conditions. Exposed shores are dominated by the barnacle Chthamalus sp. with patches of small mussels, Corallina officinalis in the lower shore and a sublittoral fringe dominated by Dabberlocks algae Alaria sp.. Moderately exposed shores are characterised by a mosaic of the barnacle Semibalanus and Fucus vesiculosus and in the most sheltered shores are dominated by knotted wrack algae Ascophyllum nodosum .
  • South Wight Maritime Extra-Regio, Hampshire and Isle of Wight
    The southern shore of the Isle of Wight, off the coast of southern England, includes a number of subtidal reefs that extend into the intertidal zone. This site is selected on account of its variety of reef types and associated communities, including chalk, limestone and sandstone reefs. To the west and south-west some of the most important subtidal British chalk reefs occur, representing over 5% of Europe’s coastal chalk exposures, including the extensive tide-swept reef off the Needles and examples at Culver Cliff and Freshwater Bay. These support a diverse range of species in both the subtidal and intertidal. Other reef habitats within the site include areas of large boulders off the coast around Ventnor. There is a large reef of harder limestone off Bembridge and Whitecliff Bay, where the horizontal and vertical faces and crevices provide a range of habitats. The bedrock is extensively bored by bivalves. Their presence, together with the holes they create, give shelter to other species, which adds further to habitat diversity. Intertidal pools support a diverse marine life, including a number of rare or unusual seaweeds, such as the shepherd’s purse seaweed Gracilaria bursa-pastoris. A number of other species reach their eastern limit of distribution along the English Channel at the Isle of Wight.
  • St Kilda Extra-Regio, Highlands and Islands
    The St Kilda archipelago is a westerly outlier of the Outer Hebrides and represents extremely wave-exposed reefs. The islands are formed of hard, igneous rock, which forms steep and vertical reefs around the entire island group. Littoral reef communities extend several metres above mean high water because of wave exposure, and populations of the uncommon exposed-shore fucoid Fucus distichus are present. Rock faces may extend sublittorally to reach depths of 50 m and support communities characteristic of very exposed conditions on rock walls, overhangs and ledges, in surge gullies and amongst boulders. The clarity of the Atlantic sea water is high, and dense kelp forests may occur as deep as 35 m. Sublittoral fringe biotopes which, elsewhere, are found only at low-water mark, may here reach depths of 12 m. Circalittoral rock is dominated by diverse communities of anemones, sponges and soft corals, with different species of sponge, hydroid and bryozoan occurring in surge gullies and caves.
  • Stanton Banks Extra-Regio
    Stanton Banks are a series of granite rises which outcrop from the seafloor south of the Outer Hebrides. Although rounded by glacial action, they remain deeply fissured and extremely rugged (Stewart and Long, 2006). The inter-connecting gullies are filled with rippled coarse shell sand. The tops of the banks are smooth and characteristically colonised by encrusting red algae and small encrusting sponges. On the slopes, where the rock is less smooth, featherstars, dead man’s fingers and hydroids are abundant (Service & Mitchell, 2004). At their edges, the banks are fringed with boulders and cobbles.


    The Stanton Banks are located in the Scottish Continental Shelf Regional Sea (JNCC, 2004a; Defra 2004), and lie approximately 124km west of the UK mainland, 43km WSW of Tiree and 83km NNE of Malin Head (Ireland). The rocky outcrops rise from the seabed at 190m to approximately 62m from the sea surface encompassing a vertical rise of approximately 130m.

  • Start Point to Plymouth Sound & Eddystone Extra-Regio
    Numerous areas of reef (in many forms) exist within the Prawle Point to East Rutts and Bigbury Bay to Plymouth Sound reefs The site comprises coastal reef features associated with the extension of the exposed terrestrial geology out into the sublittoral zone and large areas of outcropping bedrock, boulders and cobbles in the offshore extents of the area. The reefs between Prawle Point and Salcombe appear similar in nature to that to the west of Salcombe (i.e., one of high topographic complexity). This large reef habitat comprises outcropping bedrock characterised by boulders and rocky gullies, fissures and crevices in the west of the area from Salcombe around the coast to Prawle Point. The inshore reefs here support large kelp forests and a variety of other algal species
  • Strangford Lough Northern Ireland
    Reefs in Strangford Lough vary from tide-swept bedrock and large boulders in the main channel of the Narrows, through sand-scoured bedrock and boulders at either end of the channel, to more sheltered bedrock and boulders in the main central portion of the Lough and in parts of the intertidal. Beds of horse mussels Modiolus modiolus form extensive biogenic reefs within the central portion of the Lough. Tide-swept bedrock is restricted to the Strangford Narrows, where rock surfaces are entirely clothed in suspension-feeding species, notably the soft coral dead-men’s fingers Alcyonium digitatum, sponges, especially Pachymatisma johnstonia and the rock-boring Cliona celata (which reaches massive proportions), ascidians, particularly Dendrodoa grossularia and Corella parallelogramma, and sea-anemones including Metridium senile. Very large boulders strew much of the bed of the Narrows, and are subject to strong tidal streams. These boulders are clothed with encrusting sponges, such as Myxilla incrustans and Myxilla fimbriata, with abundant hydroids, especially Tubularia indivisa, and sea anemones, including Sagartia elegans, Corynactis viridis and Actinothoe sphyrodeta. Coarse sand scours rock surfaces at the sides and either end of the Narrows. Here the characteristic species is the bryozoan Flustra foliacea. Though most of the intertidal zone is clothed in sediments, glaciated or sea-worn bedrock outcrops are found at many locations. Massive boulders (glacial erratics or the cores of eroded drumlins) occur on the shore and form rocky islands known as ‘pladdies’. Whilst Silurian rocks predominate, there is sandstone at Mountstewart and limestone at Limestone Rock. The fauna and flora associated with these outcrops are dependent on the rock type, the angle of bedding-plane and degree of weathering, the position on the shore, and the degree of exposure to currents and waves. Full development of the climax biotope associated with the M. modiolus beds depends on the very sheltered, plankton-rich waters of extremely low turbidity found in the central to northern area. M. modiolus rarely occurs in such still waters. The mussels and dead mussel shells provide a hard surface in an otherwise soft-sediment environment on which numerous other species (up to 100) depend. Many mobile suspension-feeders also occur, particularly the scallop Chlamys varia which is co-dominant with M. modiolus. A similar biotope, also dominated by M. modiolus, but with brittlestars Ophiothrix fragilis and Ophiocomina nigra replacing C. varia as co-dominant, occurs in the central to south-western area where water movement is slightly greater.
  • Studland to Portland Extra-Regio
    This site lies off the south coast of Dorset and contains numerous areas of reef in many forms, which exhibit a large amount of geological variety and biological diversity. Features of particular interest within the Studland Bay to Ringstead Bay area include a series of limestone ledges (up to 15m across) protruding from shelly gravel at Worbarrow Bay, which support a rich sponge and sea fan community; dense brittlestar beds (Ophiothrix fragilis)) on shale reefs extending from Kimmeridge; a unique reef feature, known as St Albans ledge, extending out over 10km offshore and subject to strong tidal action; and an area of large limestone blocks known as the “seabed caves”. The Portland Reefs are characterised by flat bedrock, limestone ledges (Portland stone), large boulders and cobbles. On the western side of Portland Bill, rugged limestone boulders provide deep gullies and overhangs. Mussel beds (Mytilus edulis) are found to occur in very high densities on bedrock associated with strong currents to the southeast of Portland Bill.
  • Thanet Coast Kent
    Thanet Coast in the extreme south-east of England has been selected on account of the unusual communities that are found on this, the longest continuous stretch of coastal chalk in the UK. It represents approximately 20% of the UK resource of this type and 12% of the EU resource. This site contains an example of reefs on soft chalk along the shore. Thanet has sublittoral chalk platforms that extend into the littoral and form chalk cliffs. The sublittoral chalk reefs within the site are comparatively impoverished, owing to the harsh environmental conditions in the extreme southern area of the North Sea, but they are an unusual feature because of the scarcity of hard substrates in the area. Infralittoral kelp forests are characteristically absent, owing to the high turbidity of the water. The subtidal chalk platforms extend offshore in a series of steps dissected by gullies. Species present include an unusually rich littoral algal flora, essentially of chalk-boring algae, which may extend above high water mark into the splash zone in wave-exposed areas. Thanet remains the sole known location for some algal species.
  • The Maidens Extra-Regio
    Habitat occurrence description not yet available.
  • The Wash and North Norfolk Coast East Anglia, Lincolnshire
    The Wash is the largest embayment in the UK with extensive areas of subtidal mixed sediment. In the tide-swept approaches to the Wash, with a high loading of suspended sand, the relatively common tube-dwelling polychaete worm Sabellaria spinulosa forms areas of biogenic reef. These structures are varied in nature, and include reefs which stand up to 30 cm proud of the seabed and which extend for hundreds of metres (Foster-Smith & Sotheran 1999). The reefs are thought to extend into The Wash where super-abundant S. spinulosa occurs and where reef-like structures such as concretions and crusts have been recorded. The site and its surrounding waters is considered particularly important as it is the only currently known location of well-developed stable Sabellaria reef in the UK. The reefs are particularly important components of the sublittoral as they are diverse and productive habitats which support many associated species (including epibenthos and crevice fauna) that would not otherwise be found in predominantly sedimentary areas. As such, the fauna is quite distinct from other biotopes found in the site. Associated motile species include large numbers of polychaetes, mysid shrimps, the pink shrimp Pandalus montagui, and crabs. S. spinulosa is considered to be an important food source for the commercially important pink shrimp P. montagui (see overview in Holt et al. 1998).
  • Wight-Barfleur Reef Extra-Regio
    Wight-Barfleur Reef is an area of bedrock and stony reef located in the central English Channel, between St Catherine’s point on the Isle of Wight and Barfleur Point on the Cotentin Peninsula in northern France. The SAC is approximately 65km long (east to west) and up to 26km wide. The depth within the SAC ranges from 25m to 100m, with the deepest areas to the south, and within the palaeovalley which runs along the south-east part of the SAC. The large area of bedrock reef within the SAC is characterised by a series of well-defined exposed bedrock ridges, up to 4m high. The rock is generally sandstone, mudstone and siltstone, although different regions within the SAC can be distinguished on the basis of the different textures formed by different types of rock. The southern area of the site is composed of flat, smooth, mudstone and sandstone, with overlying coarse sediment (gravels, cobbles and boulders) which in places forms stony reef. The south-eastern area of the site contains part of a large palaeochannel known as the Northern Palaeovalley, which forms a major channel running roughly north-east/south-west across the English Channel. In this area the palaeovalley remains largely unfilled by sediment due to the strong currents in the area, and is characterised by a gravel, cobble and boulder substrate which in places forms stony reef. The bedrock and stony reef areas support a diverse range of reef fauna. There are Ross corals and many types of sponges present, from encrusting sponges to larger branching types. Tube worms, anemones and tunicates (sea squirts) are also common on the large boulders and bedrock.
  • Wyville Thomson Ridge Extra-Regio
    The Wyville Thomson Ridge is a rock ridge situated in the Atlantic Ocean at the northern end of the Rockall Trough. It is approximately 20km wide and 70km long and rises from over 1000m depth to less than 400m at the summit. The Ridge is composed of extensive areas of stony reef interspersed with gravel areas and bedrock reef along the flanks. The stony reef is thought to have been formed by the ploughing movement of icebergs through the seabed at the end of the last ice age. These iceberg ‘ploughmarks’ consist of ridges of boulders, cobbles and gravel where finer sediments have been winnowed away by high energy currents at the site, interspersed with finer sediment troughs up to 5m-10m deep (Masson et al., 2000). The rock and stony reef areas support diverse biological communities representative of hard substratum in deep water, including a range of sponges; stylasterid, cup and soft corals; brachiopods; cyclostome bryozoans; dense beds of featherstars and brittlestars; sea urchins, sea cucumbers and sea spiders (Masson et al., 2000; Henry & Roberts, 2004; Howell et al., 2007; and Brian Bett, pers. comm., 2004). Communities on the bedrock reef vary in species composition between the two sides of the ridge due to the influences of different water masses (Howell et al., 2007). This combination of water masses in one area is unique in UK waters.
  • Y Fenai a Bae Conwy/ Menai Strait and Conwy Bay Extra-Regio, West Wales and The Valleys
    The reefs of the Menai Strait and Conwy Bay between mainland Wales and Anglesey include the tidal rapids of the Menai Strait, and limestone reefs along the south-east Anglesey coast and around Puffin Island and the Great and Little Ormes. The environmental conditions of the Menai Strait are unusual. The water is relatively turbid, containing a relatively high level of suspended material, and although the area is largely sheltered from wave action tidal streams are strong, reaching up to 8 knots (4 m s-1) in places during spring tides. As a result, the rocky reefs of the Strait are dominated by a diverse and unusual mixture of animals that feed mainly by filtering their food from the seawater. For example, colonies of sponges, such as the breadcrumb sponge Halichondria panicea, grow to unusually large sizes, with single colonies covering areas of over 1 m2. The limestone reefs are home to several species that bore into rock, and some limestone specialists are restricted to this relatively rare habitat. Species include the rock-boring sponge Cliona celata, piddocks Hiatella arctica, polychaete worms Polydora sp., and acorn worms Phoronis hippocrepia.

SACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection

Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access.

Please note that the map shows sites where the presence of a feature is classed as ‘grade d’, but these sites are not listed. This is because ‘grade d’ indicates a non-significant presence.