Habitat account - Marine, coastal and halophytic habitats


1110 Sandbanks which are slightly covered by sea water all the time 

Background to selection

Distribution of SACs/SCIs/cSACs with habitat 1110 Sandbanks which are slightly covered by sea water all the time.  Click image for enlarged map.
Distribution of SACs/SCIs/cSACs with habitat 1110 Sandbanks which are slightly covered by sea water all the time. Click image for enlarged map.

Description and ecological characteristics

Sandbanks which are slightly covered by sea water all the time consist of sandy sediments that are permanently covered by shallow sea water, typically at depths of less than 20 m below chart datum (but sometimes including channels or other areas greater than 20 m deep). The habitat comprises distinct banks (i.e. elongated, rounded or irregular ‘mound’ shapes) which may arise from horizontal or sloping plains of sandy sediment. Where the areas of horizontal or sloping sandy habitat are closely associated with the banks, they are included within the Annex I type.

 

The diversity and types of community associated with this habitat are determined particularly by sediment type together with a variety of other physical, chemical and hydrographic factors. These include geographical location (influencing water temperature), the relative exposure of the coast (from wave-exposed open coasts to tide-swept coasts or sheltered inlets and estuaries), the topographical structure of the habitat, and differences in the depth, turbidity and salinity of the surrounding water. Within the UK’s inshore waters Sandbanks which are slightly covered by sea water all the time can be categorised into four main sub-types:

 

     

  1. gravelly and clean sands;
  2. muddy sands;
  3. eelgrass Zostera marina beds;
  4. maerl beds (composed of free-living Corallinaceae).

 

The latter two sub-types are particularly distinctive and are of high conservation value because of the diversity of species they may support and their general scarcity in UK waters.

 

Shallow sandy sediments are typically colonised by a burrowing fauna of worms, crustaceans, bivalve molluscs and echinoderms. Mobile epifauna at the surface of the sandbank may include shrimps, gastropod molluscs, crabs and fish. Sand-eels Ammodytes spp., an important food for birds, live in sandy sediments. Where coarse stable material, such as shells, stones or maerl is present on the sediment surface, species of foliose seaweeds, hydroids, bryozoans and ascidians may form distinctive communities. Shallow sandy sediments are often important nursery areas for fish, and feeding grounds for seabirds (especially puffins Fratercula arctica, guillemots Uria aalge and razorbills Alca torda) and sea-duck (e.g. common scoter Melanitta nigra).

 

Sandbanks which are slightly covered by sea water all the time are frequently associated with other marine Annex I habitats, for example grading into 1140 Mudflats and sandflats not covered by sea water at low tide in the intertidal zone. They are often component habitats of 1130 Estuaries and 1160 Large shallow inlets and bays.

European status and distribution

 

Sandbanks which are slightly covered by sea water all the time occur widely on the Atlantic coasts of north-west Europe.

UK status and distribution Click to view UK distribution of this habitat

 

Sandbanks which are slightly covered by sea water all the time occur widely around the UK coast. They are widespread in inshore waters (within 12 nautical miles of the coast) and also occur offshore in the southern North Sea and in the Irish Sea (between 12 and 200 nautical miles).

Site selection rationale

 

The SAC series includes large sublittoral sandbanks showing good habitat structure and function. The selected sites represent the range of variation within the four main sub-types (gravelly and clean sands, muddy sands, eelgrass beds, and maerl beds), which are often associated with different physiographic features (e.g. estuaries, open coast, bays, sea lochs). The differing character of this habitat around the UK coast has also been taken into account.

 

Most of the sites selected for sublittoral sandbanks also include a range of other qualifying interest features, such as marine and coastal habitats, migratory fish, and seals.

 

Potential sandbank sites in UK offshore waters (between 12 and 200 nautical miles from the coast) are currently being considered for recommendation to Defra. Areas will be identified to represent the different sub-types (linear tidal sandbanks and sandy mounds composed of muddy sand, sand and gravelly sand) in each relevant biogeographic region of UK waters.


Site accounts

Bassurelle Sandbank Extra-Regio
The Bassurelle Bank is a linear sandbank in the Dover Strait which straddles the boundary between UK and French waters. It is an example of an open shelf ridge sandbank, which is formed by tidal currents (Graham et al., 2001). The part of the sandbank within UK waters is approximately 2.5km at its widest point, and has a maximum height of around 15m. It extends for about 15km in a NE-SW direction to the UK-France median line, and then continues for some distance into French waters.
Carmarthen Bay and Estuaries/ Bae Caerfyrddin ac Aberoedd East Wales, Extra-Regio, West Wales and The Valleys
Carmarthen Bay and Estuaries on the south coast of Wales includes the sandbank of Helwick Bank, a linear shallow subtidal sandbank that is unusual in being highly exposed to wave and tidal action. The animal communities found in and on the bank reflect these conditions, being tolerant of high levels of disturbance. Within Carmarthen Bay there are also several other smaller sandbanks in relatively shallow waters, which support a range of species (including bivalves, amphipods and worms), many of which spend most of their time wholly or partly buried in the sediment.
Dogger Bank Extra-Regio
The Dogger Bank is an extensive sublittoral sandbank in the southern North Sea formed by glacial processes and submergence through sea-level rise. A large part of the southern area of the bank is covered by water seldom deeper than 20 m below chart datum. The bank is non-vegetated and comprises moderately mobile, clean sandy sediments. It is likely that the fauna of the bank has been impacted by bottom-trawling which may have reduced the number of long-lived or fragile organisms, and resulted in a community dominated by robust short-lived invertebrates including polychaetes such as Nephtys cirrosa. However, the gross physical structure of the bank is intact, and the biology is likely to be representative of the habitat.
Fal and Helford Cornwall and Isles of Scilly, Extra-Regio
This is a sheltered site on the south-west coast of England, with a low tidal range and a wide range of substrates resulting in biologically one of the richest examples of sandbanks in the UK. Sublittoral sandbanks are present throughout much of the ria system and Falmouth Bay. There are particularly rich sublittoral sand invertebrate communities with eelgrass Zostera marina beds near the mouth of both the Fal and Helford and in some channels of the rias, such as the Percuil River and Passage Cove. Of particular importance are the maerl (Phymatolithon calcareum and Lithothamnion corallioides) beds that occur in the lower Fal on St Mawes Bank, and the extensive areas of maerl gravel which extend throughout the Carrick Roads and Falmouth Bay. These are the largest beds in south-west Britain and harbour a rich variety of both epifaunal and infaunal species, including some which are rarely encountered, such as Couch’s goby Gobius couchi.
Haisborough, Hammond and Winterton Extra-Regio
The Haisborough, Hammond and Winterton site lies off the north east coast of Norfolk, and contains a series of sandbanks which meet the Annex I habitat description ‘Sandbanks slightly covered by sea water all the time’. The central sandbank ridge in the site is composed of alternating ridge headland associated sandbanks (Dyer & Huntley, 1999). This ridge consists of the sinusoidal banks which have evolved over the last 5,000 years, originally associated with the coastal alignment at the time that the Holocene marine transgression occurred (Cooper et al, 2008). The bank system consists of: Haisborough Sand, Haisborough Tail, Hammond Knoll, Winterton Ridge and Hearty Knoll. Hewett Ridge and Smiths Knoll form an older (~7,000BP) sequence of sandbank ridges located along the outer site boundary. Inshore are the Newarp Banks and North and Middle Cross Sands which lie on the south west corner of the site. These banks are believed to be geologically recent, their genesis dating to around the 5th Century AD (Cooper et al, 2008).
Inner Dowsing, Race Bank and North Ridge Extra-Regio
The Inner Dowsing, Race Bank and North Ridge site is located off the south Lincolnshire coast in the vicinity of Skegness, extending eastwards and north from Burnham Flats on the North Norfolk coast, occupying The Wash Approaches. Water depths are generally shallow and mostly less than 30m below chart datum. The area encompasses a wide range of sandbank types (banks bordering channels, linear relict banks, sinusoidal banks with distinctive ‘comb-like’ subsidiary banks) and biogenic reef of the worm Sabellaria spinulosa. These features lay almost entirely on the glacial till of the Bolders Bank Formation which is responsible for much of the evident surface topography, especially glacial mounds, channels and hollows (Cooper et al, 2008). The group of banks within the Wash Approaches are generally between 15 to 20km long and 1.5 to 3km wide. They arise from the basal layers by 7 to 12m with crest heights generally less than 5m BCD. The sedimentary component of the banks is fine to medium sands, predominantly being derived from coastal erosional processes over the last 5,000 years following the last glacial retreat and marine inundation (Cooper et al, 2008).
Isles of Scilly Complex Cornwall and Isles of Scilly
The Scilly archipelago, off the south-west tip of England, encompasses extensive sublittoral sandy sediments, which, between the islands, are contiguous with the intertidal sandflats. They are important in the UK for the extent and diversity of their associated communities. In particular, their isolation and the presence of oceanic water contribute to the special nature of the site, which is characterised by shallow sandy sediments with low silt content and by the fully marine salinity. There are rich communities present on the tide-swept sandbanks in the narrow channels between the islands and in the deeper, more stable, wave-sheltered sediments. The fauna of these sediments includes tanaid crustaceans, a diversity of polychaete worms, and various echinoderms. The shallow sublittoral sediments are colonised by the most extensive and best-developed eelgrass Zostera marina beds in southern England (Hocking & Tompsett 2001). These beds have a rich associated flora and fauna of algae, hydroids, sea anemones, molluscs and fish. Fauna with warm-water affinities include the trumpet anemone Anthopleura ballii.
Margate and Long Sands Extra-Regio
Margate and Long Sands starts to the north of the Thanet coast of Kent and proceeds in a north-easterly direction to the outer reaches of the Thames Estuary. It contains a number of Annex I Sandbanks slightly covered by seawater at all times, the largest of which is Long Sands itself. The sandbanks are composed of well-sorted sandy sediments, with muddier and more gravelly sediments in the troughs between banks, and the upper crests of some of the larger banks dry out at low tide. The banks are tidally-influenced estuary mouth sandbanks, the southern banks aligned approximately east-west in the direction of tidal currents entering the Thames Estuary from the English Channel whereas Long Sand is aligned in a north east - south west orientation with influence from the North Sea. In common with all sandbanks the structure of the banks is dynamic and there have been significant movements of the bank edges over time. The fauna of the bank crests is characteristic of species-poor, mobile sand environments, and is dominated by polychaete worms and amphipods. Within the troughs and on the bank slopes a higher diversity of polychaetes, crustacea, molluscs and echinoderms are found. Mobile epifauna includes crabs and brown shrimp, along with squid and commercially important fish species such as sole and herring. Although this site is being put forward for designation on the basis of the presence of Sandbank Annex I interest feature, there is a significant amount of the reef-forming ross worm (Sabellaria spinulosa) at this site, which when formed as a reef qualifies as an Annex I habitat (biogenic reef). However, the available data indicate that the distribution of S. spinulosa is patchy, or that the aggregations form crusts rather than reefs. Areas of high S. spinulosa density support a diverse attached epifauna of bryozoans, hydroids, sponges and tunicates, and additional fauna including polychaetes, bivalves, amphipods, crabs and lobsters. These diverse communities are usually found on the flanks of the sandbanks and towards the troughs.
North Norfolk Sandbanks and Saturn Reef Extra-Regio
The North Norfolk Sandbanks are the most extensive example of the offshore linear ridge sandbank type in UK waters (Graham et al., 2001). They are subject to a range of current strengths which are strongest on the banks closest to shore and which reduce offshore (Collins et al., 1995). The outer banks are the best example of open sea, tidal sandbanks in a moderate current strength in UK waters. Sandwaves are present, being best developed on the inner banks; the outer banks having small or no sandwaves associated with them (Collins et al., 1995). The banks support communities of invertebrates which are typical of sandy sediments in the southern North Sea such as polychaete worms, isopods, crabs and starfish. The sandbanks have a north-west to south-east orientation and are thought to be progressively, though very slowly, elongating in a north-easterly direction (perpendicular to their long axes) (Cooper et al., 2008). They extend from about 40km (22 nautical miles) off the north-east coast of Norfolk out to approximately 110km (60n miles) (Collins et al., 1995). The banks included are: Leman, Ower, Inner, Well, Broken, Swarte and four banks called, collectively, the Indefatigables. The summits of the banks are in water shallower than 20m below Chart Datum, and the flanks of the banks extend into waters up to 40 m deep.
Pen Llyn a`r Sarnau/ Lleyn Peninsula and the Sarnau East Wales, Extra-Regio, West Wales and The Valleys
Pen Llyn a’r Sarnau on the north-west coast of Wales includes the sandbanks of Devil’s Ridge, Bastram Shoal, the Tripods, and areas within and to the south of Tremadog Bay. These include examples of fully marine salinity, tide-swept sandbanks and relatively sheltered sandbanks. On Devil’s Ridge, Bastram Shoal and the Tripods strong tides mean that the sand, shell and gravel sediments are constantly shifting, and as a result the sandbanks support animals that can tolerate these high levels of disturbance.
Plymouth Sound and Estuaries Cornwall and Isles of Scilly, Devon, Extra-Regio
Plymouth Sound and Estuaries, on the south-west coast of England, has been selected for its extensive areas of sublittoral sandbanks, which consist of a range of sandy sediments within the inlet and on the open coast. These sediments include tide-swept sandy banks in estuarine habitats, sandy muds north of the Breakwater, muddy sands in Jennycliff Bay, fine sands with eelgrass Zostera marina and a rich associated flora and fauna in the Yealm entrance, as well as tide-swept sandy sediments with associated hard substrates colonised by distinctive communities of algae and invertebrates.
Red Bay Extra-Regio
The Red Bay site is located off the County Antrim village of Cushendun, Northern Ireland. It contains Annex I Sandbanks slightly covered by seawater at all times which are composed of maerl, sub-fossil maerl, coarse sands, gravels and cobbles. The sand bank is comprised of relic drowned drumlins from the last ice-age ca 15000 yr BP. The Red Bay sandbanks are dominated by both living maerl and sub-fossil maerl and have been thoroughly mapped and characterised as part of this SAC selection assessment. Unique to this site is the presence of large 2-3m high mega-ripples of sub-fossil maerl. These mega-ripples are comprised of maerl, gravel and sands on the crests, and cobbles and globular sub-fossil maerl in the troughs, with occasional sand patches on the slopes.
Shell Flat and Lune Deep Extra-Regio
Shell Flat sandbank runs northeast from the southern corner of the site in a blunt crescent to the south west.The sandbank forms a continuous structure approximately 15km long from east to west. The bank is an example of a Banner Bank, which are generally only a few kilometres in length with an elongated pear/sickle-shaped form, located in water depths less than 20m below Chart Datum (CD). Shell Flat is considered to be an excellent example of Annex I sandbank Habitat. In terms of sediment type, the bank comprises a range of mud and sand sediments from silts and clays through to coarse sands. Shell Flat is characterised by its low biodiversity, high biomass and is noted as an important foraging ground for many over wintering bird species. Surveys have identified that a large population (50,000+) of the species feed on the submerged sandbanks. This has made the Liverpool Bay area the most important site in the UK for the sea duck.
Skerries and Causeway Extra-Regio
Habitat occurrence account not yet available.
Solway Firth Cumbria, Extra-Regio, South Western Scotland
The Solway is representative of sublittoral sandbanks on the coast of north-west England/south-west Scotland. The sandbanks comprise mainly gravelly and clean sands, owing in part to the very dynamic nature of the estuary. The inner estuary contains constantly changing channels, and a predominance of sand is characteristic of such high-energy systems. There is a transition to less extreme conditions in the outer estuary. The dominant species of the infaunal communities comprise different annelid worms, crustaceans, molluscs and echinoderms, depending on the nature of the substrate. For example, the bivalve molluscs Fabulina fabula and Spisula subtruncata occur at the edge of sandbanks in fine and medium sand respectively. These communities are richer in the less extreme conditions of the outer estuary.
Sound of Arisaig (Loch Ailort to Loch Ceann Traigh) Extra-Regio, Highlands and Islands
The Sound of Arisaig is representative of sublittoral sandbanks on the west coast of Scotland. It is sheltered, with low turbidity, and has an unusually high diversity of sublittoral sediment habitats within a relatively small area. These range from very soft mud and muddy sands in Loch Ailort and the deeper parts of its entrance to coarse, clean shell-sand in the more exposed parts of the site. This site is particularly significant in that it supports some of the most extensive beds of maerl in the UK. These maerl beds have very rich associated communities that include several rare and scarce species, such as the alga Gloiosiphonia capillaris and the hydroid Halecium plumosum. Eelgrass Zostera marina is found on shallow sand in outer Loch Ailort. In the more sheltered conditions in inner Loch Ailort muddy sand occurs, supporting large populations of the echiuran worm Amalosoma eddystonense, a nationally scarce species. The Sound of Arisaig supports species with predominantly southern distributions, such as the sipunculan worm Sipunculus nudus, and those with predominantly northern distributions, such as the starfish Luidia sarsi. The site is an important part of the transition from southern to northern communities that occurs along the coast of the UK.
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 range of subtidal sandbank habitat biotopes reflects the environmental conditions within the Sound. The area is highly exposed in the west (with highly mobile, impoverished sands), tide swept but reduced exposure in the mid-channel (increased diversity of fauna with some maerl) with deeper more sheltered areas to the east (stable fine sand with a diverse infaunal community). Moving further eastwards the sediment is gravelly with large pronounced ripples and small amounts of maerl. The southern part of the Sound is more sheltered and sediments are composed of fine sand with small amounts of silt. Sediment communities are variable in composition but are often dominated by algal mats in this southern part. The sea grass beds in the Sound generally occur on the sandy substrates in moderately exposed or sheltered environments and cover a large area although the density of the Zostera is often low. Maerl is also present over a wide area, located within deeper more, exposed environments of the Sound. Although the abundance of live maerl is often low, this habitat still provides a complex niche for a diverse group of species.
The Maidens Extra-Regio
Habitat occurrence account not yet available.
The Wash and North Norfolk Coast East Anglia, Lincolnshire
On this site sandy sediments occupy most of the subtidal area, resulting in one of the largest expanses of sublittoral sandbanks in the UK. It provides a representative example of this habitat type on the more sheltered east coast of England. The subtidal sandbanks vary in composition and include coarse sand through to mixed sediment at the mouth of the embayment. Sublittoral communities present include large dense beds of brittlestars Ophiothrix fragilis. Species include the sand-mason worm Lanice conchilega and the tellin Angulus tenuis. Benthic communities on sandflats in the deeper, central part of the Wash are particularly diverse. The subtidal sandbanks provide important nursery grounds for young commercial fish species, including plaice Pleuronectes platessa, cod Gadus morhua and sole Solea solea.
Y Fenai a Bae Conwy/ Menai Strait and Conwy Bay Extra-Regio, West Wales and The Valleys
Menai Strait and Conwy Bay between mainland Wales and Anglesey includes the Four Fathom Banks complex, which is a relatively rare type of subtidal sandbank in Wales, in that it is comparatively large, and is fairly sheltered from wave action but situated in an area of open coast. The sandbanks vary from stable muddy sands in areas that experience weak tidal streams to relatively clean well-sorted and rippled sand in the outer area of the bank where tidal streams are stronger. In very shallow waters, particularly in the inner shore areas, relatively species-rich sandy communities are dominated by polychaetes such as Spio filicornis. In some years when numbers of bivalves are high, internationally important flocks of common scoter Melanitta nigra have been observed to congregate in the area of the Four Fathom Banks complex to feed.

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

Cardigan Bay/ Bae Ceredigion Extra-Regio, West Wales and The Valleys
Dornoch Firth and Morrich More Extra-Regio, Highlands and Islands
Essex Estuaries Essex, Extra-Regio
Firth of Tay and Eden Estuary Eastern Scotland, Extra-Regio
Humber Estuary East Yorkshire and Northern Lincolnshire, Extra-Regio, Lincolnshire
Loch nam Madadh Extra-Regio, Highlands and Islands
Luce Bay and Sands Extra-Regio, South Western Scotland
Lundy Devon
Moray Firth Extra-Regio
Morecambe Bay Cumbria, Extra-Regio, Lancashire
Murlough Extra-Regio, Northern Ireland
Pembrokeshire Marine/ Sir Benfro Forol Extra-Regio, West Wales and The Valleys
Rathlin Island Northern Ireland
Sanday Extra-Regio, Highlands and Islands
Severn Estuary/ Môr Hafren Dorset and Somerset, East Wales, Extra-Regio, Gloucestershire, Wiltshire and Bristol/Bath area
Solent Maritime Extra-Regio, Hampshire and Isle of Wight, Surrey, East and West Sussex
 

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