Intertidal rock, sediments and biodiversity

Status of intertidal rock and sediments: Deterioration and some concern

(Baxter et al, 2011)

Status of benthic habitats: Stable situation since 2012

 

The intertidal zone is the area covered by water at Mean High Water Springs and exposed at Mean Low Water Springs. This area is unique, being covered by water, and exposed to the air throughout the tidal cycle, meaning a variety of factors such as wave exposure and action, temperature, and salinity can affect the biodiversity, rocks, and sediments within this zone. The species within this zone must be able to survive this hostile environment, covered and uncovered twice daily by the tidesexposed to stormy seas, dried by the sun and wind or frozen. Sediments found in this zone in the Solway Firth are often mobile, and vascular plant communities in the upper shore form saltmarshes. 

Intertidal areas are important in the Solway, contributing towards a vast array of species and habitats. The large tidal range results in large areas of intertidal rocks and sediments which host rich biodiversity. The intertidal areas of the Solway also contribute to socio-economic benefits to the local area but are often undervalued despite their significant ecological value.

 

Image; Parton. © Solway Firth Partnership

Intertidal rock, sediments and biodiversity

In the Solway

Within the inner Solway many rocky shores give way to sediment flats on the lower shore. The inner Solway has the third largest area of estuarine intertidal flats in Britain, which together with the extensive subtidal sandbanks, forms one of the largest continuous areas of sedimentary habitats. Intertidal sand banks cover ~26,000ha, over 50% of the total area of the inner Solway.

Other large expanses of intertidal sandbanks include: Kirkcudbright Bay (~750ha) and Fleet Bay (~750ha), Wigtown Bay (2,900ha) and Luce Bay (~1,160ha). Rough Firth, Auchencairn Bay and Orchardton Bay have a combined intertidal sand and mudflat extent of ~1,150ha (Dumfries and Galloway Biodiversity Partnership, 2009).

The flats are an important feeding habitat for many fish populations and provide nursery areas for species such as plaice and sole. They also provide a feeding ground for ~140,000 (120,000 according to the 1996 report) wintering waterfowl. Dunes and shingle beaches are host to colonies of the rare and locally restricted Isle of Man cabbage (Coincya monensis subsp. monensis) and sand leek (allium scorodoprasum). Rocky shores provide feeding habitat for several wader species and are a preferred hunting ground for otters. Sea cliffs, along with hosting interesting coastal plant communities, also provide safe nesting sites for large numbers of breeding seabirds including fulmar, kittiwake, guillemot and razorbill.

Loch Ryan is home to a significant population of native oysters (Ostrea edulis). Generally associated with shallow, subtidal coastal and estuarine habitats, native oysters can form biogenic reefs supporting communities of other species. Scotland’s Marine Atlas (Baxter et al, 2011) includes native oysters within the ‘intertidal sediments’ section of data, as native oysters can occur in the intertidal zone. However, as native oysters in Loch Ryan are generally found in shallow waters, and fished by dredging from the seabed from hard bottomed areas on the east side of the Loch, near to Lefnoll Point (also see shallow and shelf subtidal sediments).

A full assessment of the species which can be found in these intertidal habitats is available in the Dumfries and Galloway Local Biodiversity Action Plan (DGLBAP) Part 2, available here. The DGLBAP fully explores species groups such as birds, flowering and non-flowering plants, invertebrates, fungi and lichens, and mammals which are associated with each habitat. In order to not repeat information already publicly available the DGLBAP is signposted and strongly recommended.

There is also an assessment of the habitats for part of the Solway Coast in Chapter 8 of the 1996 ‘Solway Firth Broad Scale Habitat mapping report‘. This chapter travels along the Scottish Solway coast from east to west, from the River Sark as far as Balcary, and describes the intertidal habitat of small coastal units based on preexisting surveys (Cutts & Hemingway, 1996). The report is available here.

For the English side of the Solway the Cumbria Landscape Character Guidance and Toolkit maps and describes the character of different landscape types across the county and provides guidance to help maintain their distinctiveness. Several of these landscape types are intertidal such as flats, marsh, dunes, beaches, mosses etc. They provide a helpful overview of information about the character and limited information about the ecology of these areas along the whole Cumbrian coast, beyond the extent of the Solway Firth.

Many of these coastal and intertidal habitats have been granted a protected status. Some designations are mentioned within the sections below, however for more information on designated sites in the Solway see Protected Areas.

 

Image; Burgh By Sands. © Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Sandflats and Mudflats

Communities vary throughout the Solway, with different areas of the shore offering different conditions which results in different communities.

Sand and mudflats support fish such as the common goby (Pomatoshistus microps)flounder, (Platichthys flesus) and provide a nursery for sea bass (Dicentrarchus labrax)plaice (Pleuronectes platessa)common sole (Solea solea), and Atlantic herring (Clupea herangus). Seasonal pelagic species, include the lesser sand eel (Ammodytes oobianus) and mullets (Mugilidae spp.). Sea lamprey (Petromyzon marinus)river lamprey (Lampetra fluviatilis)allis shad (Alosa alosa) and twaite shad (Alosa fallax) migrate over sand and mudflats to reach freshwater spawning grounds (Dumfries and Galloway Biodiversity Partnership, 2009). Sparling (Osmerus eperlanus), also known as European smelt, is another fish species which relies on the shallow sandflats of the Solway, with the Cree Estuary being one of the few Scottish spawning grounds of sparling. In 2019 the inner Solway on the English side of the Firth was designated as a Marine Conservation Zone specifically and solely for European smelt (see Protected Areas). Intertidal sand and mudflats in the Solway Firth are also protected features of the Solway Firth Special Area of Conservation, and Luce Bay and Sands Special Area of Conservation designations.

Sandflats and mudflats are also important feeding areas for many nationally and internationally significant species of overwintering wildfowl and waders. The estuary is very important in the UK in terms of overwintering birds (~140,000) (See Birds). Lugworm and Ragworm are also important species exploited for fishing bait. Harbour porpoises (Phocena phocena) are seen over the mud and sand within shallow Solway waters (see Whales, dolphins and porpoises).

In general, marine species richness and evenness increases with distance from freshwater input. Only especially adapted organisms can thrive in an estuarine habitat. For example, there may be as many as 20,000 burrowing amphipods (Corophium volutator) per square metre of sediment and the surface-living mud snail (Hydrobia ulvae) may reach densities of 200,000/m2 in the upper intertidal zone (Dumfries and Galloway Biodiversity Partnership, 2009).

In sandy and muddy shores a wide variety of other smaller polychaetes and oligochaete worms also occur. The burrowing amphipod (Corophium volutator) may be abundant. Bivalves include Macoma balthica, Cerastoderma edule and Abra tenuis. The mud snail (Hydrobia ulvae) is often common, and it or its tracks may be obvious on the surface of the sediment. The surface of the mud is often covered with green algae such as Enteromorpha species or Ulva lactuca (Dumfries and Galloway Biodiversity Partnership, 2009).

There is usually a black layer close to the sediment surface. Away from low salinities Cerastoderma edule and Macoma balthica may be abundant and a richer animal community can develop.

More muddy shores are suitable for the peppery furrow shell (Scrobicularia plana) community, whereas sandier shores are more suitable for the lugworm (Arenicola marina) community.

Animals living in sediment community. Solway Firth Partnership (1996)


Sand
 and mudflat mobility arises from changing erosional and depositional regimes, exposure to strong tidal streams and wave action. Much of the Solway coastline is dominated by sandy sediment and the presence of intertidal sediment flats of fine sands, rather than muds, under these estuarine salinities is unusual. The sand and mud flats can be very mobile due to the ever- changing erosional and depositional regime and exposure to strong tidal streams and wave action. River channel courses within the Solway estuaries and the Firth as a whole are constantly changing. Within the estuaries the fauna of the mid-channel banks is generally less rich than the more stable fringing sandbanks. The peppery furrow shell (Scrobicularia plana) the Baltic tellin (Macoma balthica) and the cockle (Cerastoderma edule) are common.

 

Extreme Lower Shore

On the extreme lower shore and in the shallow subtidal zone of the north Solway, fine sand and muddy sand may feature beds of common eel-grass (Zostera marina) in sheltered bays, for example at Rough Firth and Auchencairn Bay. The beds provide a habitat for other species and the roots increase sediment stability.

 

Lower Shore

Communities in the lower shore muddy sand of the open coast can feature a rich variety of polychaete worms. Species which may be present include; Nephtys cirrosa, Nephtys hombergii, Paranais fulgens, the lugwormArenicola marina, Spio filicornis, Scolopos armiger, Pygospio elegans and Megalona mirabilis. Bivalves in the clean sands typically include Angulus tenuis, Donax vittatus as well as Chamelea gallina, Mactra stultorum and Fabulina fabula. The centre of Luce Bay supports a dense population of the burrowing heart urchin (Echinocardium cordatum) and razor shells (Ensis spp) (Dumfries and Galloway Biodiversity Partnership, 2009).

In the lower shore, where there is clean medium to fine sand on moderately exposed shores, and where the sediment is sufficiently stable there are populations of cockles (Cerastoderma edule) and other bivalves not usually found on more exposed shores.

The bivalve Angulus tenuis may be present in high densities. The community is found on the lower and mid shore where the sediment is saturated most of the time. The mud content results in a reduced amphipod component and the presence of a wider range of polychaete worms.

 

Middle to Lower Shore

Muddy sand communities in the mid to lower shore are comprised of dense beds of the lugworm (Arenicola marina), although they can be found anywhere from the upper shore to the lower shore, in sheltered conditions and in low or variable salinity.

In this habitat, the sediment generally remains saturated during low water. Other species present include the bivalves (Macoma balthica and Cerastoderma edule) and the polychaete worms; Pygospio elegans, Hediste diversicolor and Nephtys hombergii. The recruitment of lugworms (Arenicola marina) can be very variable and it may be temporarily absent from areas.

The nationally rare wine-glass hydroid (Obelia bidentata) grows up to 2.5cm long in tree-like pink colonies in the inner Solway (Dumfries and Galloway Biodiversity Partnership, 2009).

 

Upper to middle shore

In the upper to mid shore where there is reduced salinity a wide range of polychaete worms are present, including: Nephtys hombergii, Pygospio elegansArenicola marina and the widespread ragworm Hediste diversicolor. The green algaUlva intestinalis and sea lettuce, Ulva lactuca may colonise the surface of mud in the summer months in sheltered conditions and variable salinities.

 

Upper Shore

On the upper shores of the Solway much of the mud and sand flat is colonised by saltmarsh vegetation, considered below. Elsewhere on these shores and on more exposed beaches and sandbanks there may be little or no conspicuous signs of life. However, life in the sand and mudflats of the Solway is quite the opposite, with Solway sediments supporting rich communities of marine and estuarine species. The eel grasses (types of seagrass) Zostera noltii and Zostera angustifolia colonise areas of intertidal flat on the north side of the Solway. With the exception of the eel grasses, flowering plants are unable to survive in these hostile marine environments. Roots from eel grasses help hold sediment and support a communities of worms, cockles, and other intertidal species.

Many of the larger animal species (macrofauna) burrow in the sediment. Doing so allows them to protect themselves from drying out and being eaten by surface living predators such as birds and fish. The nature of the communities present depends upon factors such as the type of sedimentheight on the shore, exposure to wave action and salinity.

Coarse well-sorted sands on exposed beaches dry out too much for the majority of marine life. Muds on the other hand remain saturated with water but have little water exchange and often have little or no oxygen present in the sediment even just below the surface. Between these extremes there are a wide range of habitats in which the silt content, salinity, wave exposure and other factors are important in determining community development.

 

Image; Grune Point © Solway Coast Area of Outstanding Natural Beauty

Intertidal rock, sediments and biodiversity

Seagrass

Seagrass beds can be found in mud and sand in both the intertidal and subtidal zones with low wave action. Unlike algae which uses holdfasts to secure itself to the sea floor, seagrass is a flowering plant with roots and leaves, even when located in the subtidal zone.

Three species of seagrass are known to occur in the UK, all of which have been recorded in the Solway in the past;

  • Common Seagrass (Zostera marina) is found in fully marine situations and occasionally in estuaries, on sheltered gravel, sand or mud from Low Water Spring tide to 4m.
  • Narrow-leaved Seagrass (Zostera angustifolia) is found on mud banks, creeks and estuaries from half-tide to Low Water Spring.
  • Dwarf Seagrass (Zostera noltii) occurs in similar habitats to Z. Angustifolia but may extend to the lower saltmarsh communities around Mean High Water.’
    (Dumfries and Galloway Biodiversity Partnership, 2009).

A survey of Loch Ryan was undertaken by the Scottish Environment Protection Agency (SEPA) in 2010 which found intertidal seagrass (specifically Z. noltii) to be present off Stranraer and at Wig Sands. A full survey was undertaken in 2013 when; ‘seagrass beds mapped at Wig Sands covered 21,100m2 with an average percent cover between 30-40%. In the Stranraer area the seagrass covered 83,700m2 with an average percent cover between 12-56%. Z. noltii was the only seagrass species found in the loch’ (Foster and Davidson, 2018).

From information provided in the DGLBAP seagrass in the Solway has occurred in other areas outside of Loch Ryan. DGLBAP outlines that Z. noltii was also present at; Manxman’s Lake in Kirkcudbright Bay, around Rough Island in Rough Firth, in Auchencairn Bay, in Fleet Bay and at Baldoon Sands in Wigtown Bay around the time of writing the action plan (Dumfries and Galloway Biodiversity Partnership, 2009). The DGLBAP also suggested the presence of Zostera marina in Loch Ryan, although this is a fully marine seagrass and therefore was not be captured by SEPAs 2013 intertidal survey. The action plan also outlined that, at the time of writing, the plan; ‘Zostera angustifolia occurs in many of the same locations in Kirkcudbright Bay, Rough Firth and Auchencairn Bay. Seagrass beds have also been recorded in the Nith Estuary‘ (Dumfries and Galloway Biodiversity Partnership, 2009).

 

Intertidal rock, sediments and biodiversity

Scar Ground

Scar grounds are areas of pebblescobbles and boulders raised above the level of the surrounding mobile sand but may frequently be covered or scoured by the sand. Lower-lying scar ground may be only briefly exposed to colonisation by marine life before it is inundated or scoured by sand again. These coarse sediments are not widespread within the Solway; where they occur, they have usually been formed from erosion of boulder clays and other glacial deposits.

More extensive areas of scar ground are present on the English side of the Solway than on the Scottish side, most notably at Dubmill Point and down the coast to Workington. On the Scottish side scar ground is present at Powfoot and on the east side of Luce Bay with other patches on Wigtown Bay and at Hestan Rock.

Scar Ground
Solway Firth Partnership (1996)

Colonisation is influenced by the time of year when the rocky surfaces become exposed as the spawning and recruitment of many marine plants and animals is seasonal. The first colonisers include barnacles (Semibalanus balanoides and Elminius modestus) and various algae, both green (Ulothrix spp., Enteromorpha spp. and Ulva lactuca) and red (.Porphyra spp.). Newly exposed scar grounds are also colonised by non-flowering plants such as; gutweeds (Enteromorpha linza and E. intestinalis), sea lettuce (Ulva lactua), and purple laver (Porphyra umbilicalis) (Dumfries and Galloway Biodiversity Partnership, 2009). If the rock exposure continues, additional colonisers include periwinkles (Littorina littorea) and brown fucoid algae (Fucus spp).

In areas away from periodic inundation by sand, a richer and more diverse community can establish. Even here, the dominant species can change rapidly. Many of the species which occur are characteristic of subtidal rocky habitats but are able to extend into the intertidal on these scars. The breadcrumb sponge (Halichondria panicea) is a conspicuous part of a widespread scar community. The honeycomb, ‘reef-building’ worm (Sabellaria alveolata) reaches its northern limit in the British Isles in the Solway. It builds its tube from sand or shells fragments and colonies of the worm can form extensive hummocks and reefs over the shore, discussed below. However, large settlements of mussel (Mytilus edulis) sometimes cover the Sabellaria beds, smothering the worms and eventually leading to the collapse of the reefs.

 

Image; Powfoot. © G. Reid/ Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Rocky shore

The most extensive areas of rocky shore in north-west England are the St Bees Head sandstone shores. Boulders and outcrops of rock are present along the coast between St Bees Head and WorkingtonSolidified slag (‘slagcrete’) from former ironworks sites has added to the hard substratum present. On the north coast of the Firth, rock outcrops within the inner Solway generally give way to sand high on the shore and only sediment scoured upper shore rock is present. Rocky shore communities are much more extensive between Southerness Point and the Mull of Galloway. These shores generally consist of boulders with occasional bedrock outcrops ranging from open coast exposed to wave action to sheltered embayments.

Rocky shores are a hostile environment for marine species to live in, and so plants and animals have to be well adapted to this harsh environment and to out compete other species for very limited space.

Fish are often present on the mid and upper shore in spring and summer, moving downshore or offshore in winter. Species include the common blenny (Lipophrys pholis)rock goby (Gobius paganellus) and butterfish (Pholis gunnellus) (Dumfries and Galloway Biodiversity Partnership, 2009).

Otters (Lutra lutra) feed on intertidal rocky shores. Grey seals (Halichoerus grypu) and the rarely seen common seal (Phoca vitulina) use undisturbed rocky shores as haul-out sites (see Seals).

Rocky Shores
Solway Firth Partnership (1996)

 

As can be seen in the diagram (below) prepared for the original 1996 Solway Review, seaweeds are common on rocky shores of the Solway, showing clear zones in this type of shore habitat. The low shore (otherwise known as the ‘low intertidal zone’) is the area of the intertidal zone closest to the low tide mark, and is only exposed to the air close to low tide, often being covered by the tide as it ebbs and flows. The middle shore (otherwise known as the ‘mid intertidal zone’), and upper shore (otherwise known as the ‘high intertidal zone’) are progressively further from the low tide mark and therefore exposed to the air for longer periods of time, given the time it takes the tide to rise. The splash zone (otherwise known as supratidal/ supralittoral/ spray zone) is technically beyond the intertidal zone as it is not covered by water even at high tide. This zone is still impacted by the marine environment given the influence of saltwater spray, and wave influence during storm events.

 

Lower Shore

Within the inner Solway many of the rocky shores give way to sediment flats on the lower shore. Subtidal fringe communities are generally restricted to the open coasts of Dumfries and Galloway and to the rocky coast around St Bees Head.

They are characterised by a canopy of the kelp (Laminaria digitata) beneath which the rock surface is encrusted by coralline red algae. Barnacles (Semibalanus balanoides and Balanus crenatus) are also common. The brown seaweed Alaria esculenta occurs on the more exposed shores. According to the DGLBAP; ‘The green seaweed (Tellamia contorta) is known from the Rhins, but is difficult to find and probably widespread, being largely restricted to the inside of living periwinkle shells’ (Dumfries and Galloway Biodiversity Partnership, 2009). Red algae such as Palmaria palmata, Mastocarpus stellatus and Chondrus crispus are frequent amongst the kelp. Kelp forests are found at Lady Bay in Loch Ryan and the Mull of Galloway. Species include oarweed (Laminaria digitata)sugar kelp (Saccharina latissama), and dabberlocks (Alaria esculentla).

Rocky shore animals and zonation.
Solway Firth Partnership (1996)

 

Middle Shore

On moderately exposed lower shores serrated wrack (Fucus serratus)barnacles (S. balanoides)dogwhelks (Nucella lapillus) and limpets (Patella vulgata) are present. Coralline algal crusts cover much of the rock surface and this increases with wave exposure. There is an overlying dense turf of red algae including Palmaria palmata, Mastocarpus stellatusCorallina officinalis and Lomentaria articulata, which extends up the shore on overhangings and in crevices, protected from desiccation. Pits and crevices in the rock form refuges for small musselsgastropod molluscs and the beadlet anemone (Actinia equinus). Under sheltered conditions there is a more luxuriant growth and canopy of the wracks with a sparser understory on the rock. The lower shores are often dominated by brown species of seaweed, with scarce species such as Petrospongium berkeleyi and Corynophlaea crispa being recorded at Mull of Galloway, and diverse red seaweeds (such as Erythrotrichia investiens and E. bertholdii) growing on other algae in the lower intertidal and shallow subtidal zone (Dumfries and Galloway Biodiversity Partnership, 2009).

On the exposed rocky mid shore the barnacle (Semibalanus balanoides) is dominant with green algae (Ulva lactuca and Ulva intestinalis) common. Bladder wrack (Fucus vesiculosus), and knotted wrack (Ascophyllum nodosum) are common and coralline red seaweeds dominate the rockpools. Dogwhelk (Nucella lapillus) remain characteristic of this zone, as is egg wrack (Ascophyllum nodosum) in very sheltered areas.

The edible blue mussel (Mytilus edulis) beds are common along the Scottish and English Solway coasts in the intertidal and subtidal zones. There are several mussel beds between Maryport and Silloth, notably near Dubmill and Mawbray on the Cumbrian coast; Ellison’s Inner & Mid Beds, Beckfoot Flats & Lees Scar. Dubmill North bed is below mean low water springs and therefore is not intertidal as are many blue mussel beds on the Scottish side of the Firth. Some intertidal blue mussel beds are previously recorded in Balcary Bay, Fleet Bay and in the Dee Estuary. According to a 1997 report from Scottish Natural Heritage (now NatureScot), the Solway was the location in Scotland most reported to feature ‘transient populations’ of mussels. Due to the mobile nature of sediments in the Solway there is the potential for blue mussel beds to establish in an area and then be displaced. Elsewhere beds tend to become established with location remaining consistent over long periods (McKay & Fowler, 1997).

Biogenic reefs, such as blue mussel beds, are raised from the seabed, and made from hard matter, such as shells, created by living organism activities. These reefs are often located below the low water mark in the subtidal area of UK waters. Seagrass is also a biogenic habitat (not a reef as seagrass does not create solid matter) as it creates a habitat in itself (more on biogenic habitats see shallow and shelf subtidal sediments).

Rocky shore species have also colonised the upper parts of Robin Rigg Wind Farm marine structures which, similar to coastal areas, are covered and exposed twice a day with the tides, creating a habitat similar to the intertidal environment on the structures. Species on the structures include barnacles, mussels and seaweeds.

 

Upper Shore

The upper area of the intertidal zone (littoral fringe) is characterised by channelled wrack (Pelvetia canaliculata), spiral wrack (Fucus spiralis), periwinkles (Littorina saxatilis and Littorina littorea) and black lichen. With increased exposure to wave action L. saxatilis and black lichen increase as the wracks decrease. On exposed shores a band of the barnacle (Chthamalus montagui) is present. Under sheltered conditions the wracks are dominant with the occasional introduced Australian barnacle (Elminius modestus). Reptiles such as Adders (Vipera berus) and Common Lizards (Zootoca vivipara) are occasional visitors to intertidal rocky shores, particularly in warm sunny weather when they can be seen basking in the sunshine to warm themselves.

 

Splash Zone

Splash zone rocks with yellow and grey lichens are found on shores above high tides, its vertical extent increasing with increased exposure to wave action. It is characterised throughout the Solway by the colourful lichens Verrucaria maura (black), Caloplaca marina (orange), Xanthoria parietina (yellow) and Lecanora atra (grey). Some mosses capable of surviving salt water spray can also be found in the splash zone, such as seaside grimmia (Schistidium maritimum) (Dumfries and Galloway Biodiversity Partnership, 2009).

 

Rockpools

Rockpools occur on many of the rocky shores of the Solway. They are characterised by a dense covering of encrusting coralline algae on which Corallina officinalis often forms a dense turf. Filamentous and foliose red algae include; Chondrus crispus, Ceramium rubrum and Mastocarpus stellatus. Animals present include periwinkles (Littorina obtusata and Littorina saxatilis), topshells (Gibbula cineraria) and limpets (Patella vulgata), all of which can occur in large numbers. The beadlet anenome (Actinia equina) is often common in pits and crevices. Unlike other areas of rocky shore, seaweeds are unlikely to be the dominant species found in rockpools.

 

Image; Seaweed at Powillimount © Reid/ Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Honeycomb Worm Reef

The ‘reef-building’ honeycomb worm (Sabellaria alveolata) is a filter feeder which reaches its northern limit in the British Isles in the Solway, growing primarily on subtidal and intertidal rock, but can also form on other substrates. The biogenic reefs reach 30-50cm thick and larvae generally settle on established locations. The most extensive reefs in the Scottish Solway are found at SouthernessRascarrel/Balcary Bay, Meikle Ross, Kirkandrews Bay/Islands of Fleet and Stairhaven/Auchenmalg on the east side of Luce Bay. At St Bees Head the presence of colonies on vertical bedrock is indicative of the amount of sand suspended in seawater. Honeycomb worm reefs are one of the features protected through both the Cumbria Coast Marine Conservation Zone and Allonby Bay Marine Conservation Zone (see Protected Areas), with the management of both sites aiming to maintain the favourable condition of the nationally important reefs (along with maintaining the favourable condition of other protected intertidal features and recovering Razorbill, Alca torda, to favourable condition (in the Cumbria Coast site).

The worms are called ‘honeycomb worms’ due to the tubes they construct in reefs, which look akin to honeycomb structures in a beehive. These worms can possibly live up to 9 years, however generally have a life span between 3 and 5 years. Reefs outlive the worms residing within them and provide habitat for other species.

 

Image; Honeycomb worm reef. © N. Coombey/ Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Peat and Clay

Peat and clay exposures are known to occur in the Solway Firth and are important for providing insights into the history of an area, often preserving the remains of plants or animals. Peat and clay have helped preserve ancient forests at locations such as Allonby, Beckfoot (Cumbria), and Redkirk (Dumfries and Galloway), with more at Glasson, where sunken forests were discovered between 1812-1832 during Carlisle Canal excavation (Historic England, n.d). Peat and clay exposures can provide habitat for piddocks, such as Pholas dactylus, Barnea candida

, a burrowing bivalve which also burrow into the wood of submerged trees. Peat and clay exposures are included as one of the three marine habitats designated as protected features within the Allonby Bay Marine Conservation Zone (see Protected Areas). They are also included as features in the 2013 designation of the Cumbria Coast Marine Conservation Zone, part of which lies in the Solway. However, according to the ‘feature maps’ for this zone the peat and clay exposures occur along the Cumbrian coast beyond the Solway Firth.

Redkirk’s peat exposures feature the remains of 8,000 year old tree stumps (Scottish Coastal Archaeology and the Problem of Erosion (SCAPE) 2019). As mentioned throughout the Solway Review, the changing and shifting sands of the Solway mean that intertidal habitats and features such as peat and clay exposures, and the history they hold, may be frequently covered or exposed by sand and sediment. Erosion of peat and clay exposures may accelerate with climate change due to increased wave action and storminess.

 

Image; Redkirk, 8,000 year old tree stumps. © N. Coombey/ Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Vegetated Shingle

Shingle comprises sediments of a size between sand and boulders (2mm to 200mm in diameter).

The fringing shingle beaches of Cumbria and the raised shingle beaches of the Scottish Solway represent a considerable amount of the British shingle resource. Shingle shores are important for breeding waders such as oystercatcher and ringed plover and for seabirds such as little tern (see Birds). The north Solway has sandy and marshy shingle from Powfoot to Dornoch with a boulder shore backed by a raised shingle beach at Rascarrel Bay. Wildfowl graze on the shingle adjacent to the saltmarsh at Powfoot. From Burrow Head to Auchenmalg Bay there is an almost continuous raised sand/shingle beach. This varies in width from a few metres to more complex spit and ridge systems, as at Philip and Mary and Claymoddie.

On the sandier shores fringing much of the south Solway the pioneer community consists of sea sandwort (Honkenya peploides), sea holly (Eryngium maritimum) and sand couch-grass (Elymus farctus). A common pioneer community on shingle strands is that dominated by sea radish (Raphanus maritimus), sea mayweed (Tripleurospermum maritimum) and false oat grass (Arrhenatherum elatius), sometimes with orache (Atriplex prostrata) and curled dock (Rumex crispus). The raised shingle beaches of the Scottish Solway are important for their acid woody vegetation of gorse (Ulex europaeus), bramble (Rubus fruticosus) and prostrate blackthorn (Prunus spinosa) scrub, with burnet rose (Rosa pimpinelli folia). Rascarrel Bay is unique in having wet woodland with sallow (Salix cinerea) and hazel (Corylus avellana) present on the shingle shore.

The yellow horned-poppy (Glaucium flavum) reaches its northern limit on the north Solway shore whilst the most important rare shingle plant of north-west Britain, the nationally scarce oyster plant (Mertensia maritima), is near to its southern limit. Luce Bay supports a particularly good representation of north-western shingle communities. The nationally scarce Isle of Man cabbage (Rhyncosinapis monensis) and Ray’s knotgrass (Polygonum raii) also are found on the fringing beaches and shingle of the Solway.

Shingle beaches throughout the Solway are also popular areas for reptiles such as adder (Vipera berus).

Coastal vegetated shingle outside the reach of waves is a feature of qualifying interest, and one of several features, which form part of the Solway Firth Special Area of Conservation designation (see Protected Areas).

Vegetated shingle is one of three intertidal soft coast habitats mapped throughout Scotland by NatureScot as part of the Habitat Map of Scotland. The data, covering the Scottish side of the Solway, is available and can be explored through links on the NatureScot Habitat Map of Scotland page, available here.

 

Image; Workington. © Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Saltmarsh

Saltmarsh, or ‘merse‘ as it is known locally in Scotland, are important intertidal areas found in the middle or upper levels of the intertidal environment, and are flooded with the tides. Saltmarsh looks like a grassy flat area between land and sandy or muddy low intertidal areas. Shingle can also be found on the seaward edge of some Solway saltmarshes. They are important intertidal habitats with vast and varied importance in nutrient and sediment transport, coastal defence, and carbon storage. Areas of saltmarsh are under pressure from ongoing threats such as climate change and sea level rise. In addition to the frequent saltmarshes along the Scottish Solway coast, according to a NatureScot commissioned report all three of the largest saltmarshes in Scotland are located within the Solway; Caerlaverock, Kirkconnell Merse and Wigtown (Haynes, 2016). Saltmarsh is also one of three intertidal soft coast habitats mapped throughout Scotland by NatureScot as part of the Habitat Map of Scotland. The data, covering the Scottish side of the Solway, is available and can be explored through links on the NatureScot Habitat Map of Scotland page, available here.

Saltmarsh are habitats which are created through sediment trapping shrubs which can survive the frequent inundation of salt water from the changing tides, but are also developed in sheltered areas meaning the tides are less affected by wave action. These intertidal habitats are colonised by the most salt tolerant plants and slowly build up trapped sediments into mounds of grasses and shrubs. Saltmarshes eventually look like islands built up from the water and progressively join to form complete coverage closer to land, with creeks allowing for the ebb and flow of the tide to move around them. These creeks can sometimes be deep and broad, which can make saltmarsh dangerous to navigate, and cause internal erosion should they widen. Some areas of saltmarsh in the Solway have been eroded over time, whereas others have accreted, although globally there is a significant trend that this habitat is being degraded and lost.

A creek in the saltmarsh at Burgh Marsh, Cumbria. © Solway Firth Partnership

Saltmarshes are vitally important for socio-economic and environmental reasons. The presence of wildfowl and waders, which feed on the saltmarsh, has helped several nature conservation designations and sites become established around the Firth. They also provide important feeding and breeding habitat for natterjack toads (Epidalea calamita) which are found at the most northern point of their range in the Solway. Given the deep creeks, frequent flooding, and potentially difficulties crossing saltmarsh habitats, recreational uses are limited, with wildfowling and coastal/dog walking being among the most frequent uses. Cattle grazing has been a frequent use of Solway saltmarshes and is discussed below. Healthy saltmarsh may also function as a natural coastal defence by reducing wave action reaching the upper shore. Coastal defence is a highly valuable ecosystem service provided by saltmarsh habitat, effectively dispersing wave action and offering progressively significant defence from waves as the area of saltmarsh becomes wider.

The Solway features small areas of saltmarsh along much of the coastline. English saltmarsh areas include Rockcliffe and Burgh, as well as Moricambe Bay in the inner Solway, with Caerlaverock and Kirkconnel Merses in Scotland’s inner Solway. In the outer Solway the largest area of saltmarsh is located in Wigtown Bay. The location of the Solway saltmarshes links northern and southern British saltmarsh communities.

The saltmarsh vegetation reflects the age, type of sediment and management of the marshes and shows a well-represented sequence of communities from the shore moving inland. The seaward edge of the saltmarsh is usually pioneered by common saltmarsh grass (Puccinellia maritima), whilst glasswort (Salicornia europaea) colonises mudflats. The invasive cord grass (Spartina anglica) is now found in estuaries in the Solway Firth, dominating communities in the Rough Firth; Auchencairn & Orchardton Bays; Fleet Bay; and Wigtown (Haynes, 2016). Sea-milkwort (Glaux maritima) is another pioneering species but is more common further inland than glasswort or saltmarsh grass, so is associated more with the lower to mid area of saltmarsh. Given the frequent inundation with saltwater only highly salt tolerant plants, for example the moss Hennediella heimii, can survive in the lower reaches of Solway saltmarsh. 

Pioneer saltmarsh communities in the Solway include; 

  • Annual Salicornia saltmarsh community, associated with sandflats (although often sparse),
  • Transitional low-marsh vegetation with Puccinellia maritima, annual Salicornia species and Suaeda maritima
  • Aster tripolium var. discoideus saltmarsh community
  • The invasive Spartina anglica saltmarsh community, and the sub communities;
  • Coastal stands of rayed Aster tripolium,
  • Puccinellia maritima dominated sub-community, and
  • Puccinellia maritima-Spartina anglica sub-community
    (Haynes, 2016)

 

Section through a typical Solway saltmarsh showing stages of community development.
Solway Firth Partnership (1996)

Landward from the pioneer zone there is a transition to grassy saltmarsh dominated by red fescue (Festuca rubra), thrift (Armeria maritima) and saltmarsh rush (Juncus gerardii). In places, creeping bent (Agrostis stolonifera), sea plantain (Plantago maritima), sea arrowgrass (Triglochin maritima), parsley water-dropwort (Oenanthe lachenalii) and various sedges (Carex spp.) are also prominent. The saltmarsh flat-sedge (Blysmus rufus) occurs on the northern shore in wet depressions and flushes in the upper marsh. Many herbaceous species such as sea purslane (Halimione portaculoides) and common sea-lavender (Limonium vuigare) are restricted by grazing and are found by fringing creeks and channels. The DGLBAP also notes that ‘the Solway provides virtually the only UK records of Pseudephemerum nitidum in this habitat. Most species are found in mid to upper saltmarshes, especially where grazed and flushed with freshwater’ (Dumfries and Galloway Biodiversity Partnership, 2009).

Lower saltmarsh communities in the Solway include;

  • Puccinellia maritima dominated sub-community
  • Puccinellia maritima-Spartina anglica sub-community

(Haynes, 2016)

Middle saltmarsh communities, several of which are unique to the Solway in Scotland, include;

  • Glaux maritima sub-community (often forms as a response to grazing by geese)
  • Limonium vulgare-Armeria maritima sub-community
  • Plantago maritima-Armeria maritima sub-community
  • Halimione portulacoides dominated sub-community
  • Puccinellia maritima sub-community
  • Juncus maritimus-Triglochin maritima saltmarsh

(Haynes, 2016)

The landward edge of the marshes has fewer salt-tolerant plants leaving grasses such as bents (Agrostis spp.) and fescues (Festuca spp), saltmarsh grass (Puccinellia maritima) and saltmarsh rush (Juncus gerardii). Upper shore communities also include ‘the uncommon seaside centaury (Centaurium littorale) and lesser centaury (Centaurium pulchellum) at the northern edge of its range, as well as many plants that are not specialist salt-tolerant species, including the nationally rare holy grass (Hierochloe odorata)’ (Dumfries and Galloway Biodiversity Partnership, 2009). Inland brackish water areas support common reed, (Phragmites australisor) pools with aquatic plants such as the scarce whorl-grass (Catabrosa aquatica) and flowering rush (Butomus umbellatus).

The extent and variety of vegetation forms communities in the estuarine saltmarshes or merses of high nature conservation importance with broad transitions to mature ‘upper marsh’ being particularly well represented.

Upper saltmarsh communities in the Solway include;

  • Puccinellia maritima sub-community
  • Juncus gerardii dominated sub-community (variant of which is found across Caerlaverock and Nith Estuary saltmarshes, which includes Trifolium repens within the sward)
  • Festuca rubra-Glaux maritima sub-community
  • Tall Festuca rubra dominated sub-community
  • Leontodon autumnalis sub-community
  • Carex flacca sub-community
  • Artemisia maritima saltmarsh
  • Plantago maritima sub-community
  • Eleocharis uniglumis saltmarsh community

(Haynes, 2016)

Well-developed creek systems are present in the Solway saltmarshes, including unusual examples on high mature marsh where vegetation is removed. All known types of saltpans are also represented. In several places the erosional edge of the saltmarsh is exceptional where combined marine and fluvial processes have formed a cliff two or three metres high. Additionally, the inner Solway saltmarshes provide the finest example in Britain of marsh terraces formed by the process of creek migration and geological uplift.

Strandline saltmarsh communities in the Solway include;

  • Ephemeral saltmarsh vegetation with Sagina maritima
  • Elymus repens saltmarsh

(Haynes, 2016)

Saltmarsh in the Solway supports a range of species such as the natterjack toad and numerous species of invertebrate, and supports the vast bird population of the Solway including wildfowl and waders. Saltmarsh is one of the habitats which help contribute to the international important species and numbers of birds in the Solway Firth, and the designations which have been established (see Protected Areas). Saltmarsh is also a habitat which is a key feature in several designations around the Solway, in addition to the species of conservation importance is supports.

As saltmarsh intertidal habitats transition to coastal habitats, coastal grassland communities may be present. Coastal grasslands such as; Festuca rubra-Agrostis stolonifera-Potentilla anserina grassland, Festuca arundinacea grassland, and Agrostis stolonifera-Alopecurus geniculatus grassland are known to be present in the transitional zone of Solway saltmarshes.

 

Carbon Storage

In addition to ecological value, saltmarsh have a variety of socio-economic benefits, as mentioned above. One of the key resources which saltmarsh provides is storage of blue carbon. The carbon storage value and effectiveness of saltmarsh habitats are being increasingly studied in order to manage and restore this habitat effectively. Various UK projects and research have been focussed on saltmarsh recording, carbon storage potential, restoration, management, and value. For example, the C-SIDE Carbon Quest survey is ‘striving to produce the first large-scale empirical study of saltmarsh carbon storage, accretion rates, its drivers and the long-term stability/resilience of these stores. The outcomes of the work will provide practical guidance for coastal managers and inform shoreline policy to safeguard carbon storage in the intertidal zone’ (C-SIDE, n.d.)

While offering effective carbon sequestration to help mitigate climate change, saltmarsh habitat is also under pressure from climate change. There is a trend that this habitat is being degraded and lost both globally and likely also in the UK, and climate change has the potential to exacerbate this loss. According to the 2005 Shoreline Management Plan in Dumfries and Galloway, sea level rise alone is not expected to significantly reduce saltmarsh habitat in the inner Solway, given the abundance of sediment available. There is more concern that increases in water level could increase wave action over ‘a longer period of the tidal cycle’ which could lead to erosion of saltmarshes and ‘changes in river flows that can effect the location of the river channels.’ (HR Wallingford Limited, 2005).

 

Agricultural use of Saltmarsh

Coastal grazing marsh is a different and distinctive habitat from saltmarsh consisting of low-lying grassland drained by a network of ditches which may be either freshwater or brackish, regularly flooded by the sea. Often the botanical interest of grazing marshes is associated with the ditch systems rather than the fields between them. Traditionally, there has been only small scale and piecemeal enclosure of saltmarsh on the Solway for agricultural use as grazing marsh. Much of this is around the estuaries of the Rivers Esk, Annan and Eden and in Moricambe Bay.

In several areas around the Solway the seawall marks the abrupt landward transition to permanent leys; agricultural land which is maintained as pastures but which has been re-seeded to improve its agricultural value.

Grazing has had a major influence on the structure and species composition of the saltmarsh communities. Heavily grazed marshes have a lower diversity and abundance of herbaceous plants, these being restricted to or most abundant on creek banks and in other habitats less accessible to grazing animals. Careful management of the grazing is necessary to maintain the high importance of the saltmarshes for breeding and wintering birds. A relatively high grazing pressure prevents the development of coarse and tussocky vegetation and produces a short grassy sward. This encourages young grass growth in early spring which is important grazing for barnacle geese, pink-footed geese and other wildfowl. Lower grazing pressure can produce a mosaic of long tussocks and short turf which is favoured by many wader species for breeding and roosting. The importance of appropriate and continued agricultural management of the saltmarshes to maintain these wildlife interests is recognised widely.

Given the rich biodiversity of saltmarsh habitat, the difficulty in using saltmarsh areas for many socio-economic activities, and the suitability for grazing livestock, Solway saltmarshes have historically been used for agricultural purposes on both the Scottish and Cumbrian sides. Cumbrian Solway saltmarshes have been grazed by cattle since 1150AD, and most of the marshes remain common land with areas of saltmarsh auctioned out to farmers annually as ‘stints’. Stints relate to a specific number of animals which can graze and is variable depending on which land the stint relates to. The grazing commons are run by ‘Marsh Committees’, and are auctioned for grazing under strict rules. Only the auctioneer knows how many stints are on sale each year. There are no fences restricting movement of the animals who wander freely on the marsh.

Rockcliffe marsh in the Inner Solway is a ~2,800 acre saltmarsh owned by Castletown Estate and Farm. The saltmarsh is used to rear ‘saltmarsh lamb‘, and also to graze cattle in order to control the vegetation growth and contribute to the healthy functioning of the marsh.

Unlike on the English side of the Firth, which is predominantly common land, coastal saltmarsh on the Scottish side is often under private ownership managed by conservation organisations. The areas of improved agricultural grassland at Eastpark Farm (managed by Wildfowl and Wetlands Trust) and inland of the Caerlaverock National Nature Reserve support a sizable proportion of the internationally significant population of Svalbard barnacle geese (Branta Leucopsis) throughout the winter. Wildfowl and Wetlands Trust (WWT) Caerlaverock grazes a small flock of Hebridean Sheep and our two Longhorn Cows over the summer months to achieve ‘conservation grazing’ on Saltcot Merse. In 2020 COVID lockdown restricted WWT’s ability to graze the merse, instead relying on cutting the fields by tractor. Read more about WWT’s conservation grazing here. On the Caerlaverock National Nature Reserve, cattle grazing helps keep the saltmarsh grasses at the right height for wintering and breeding birds, illustrating the practicality of grazing on these habitats, benefiting farmers and assisting in the effective management of saltmarsh for species. During the summer months cattle may also be found grazing on the Southwick Coast Scottish Wildlife Trust site near Dalbeattie, and Royal Society for the Protection of Birds Crook of Balloon merse.

Grazing is beneficial to saltmarsh habitats if managed appropriately, for example in terms of numbers of animals, and time of year.

 

Image; Interactive salt marsh map of the UK © C-SIDE (Carbon Storage in Intertidal Environments) Project

Intertidal rock, sediments and biodiversity

Sand Dunes

Sand dunes are the accumulation of wind-blown sand which builds up over time, typically in ridges and mounds, as the sand is trapped in vegetation. Sand dunes provide a habitat for a variety of plants and species, many of which are rare or threatened. Many of the Solway sand dune areas are protected through designations such as Ramsar, Special Area of Conservation (SAC) and Site of Special Scientific Interest (SSSI), to maintain or re-establish favourable condition of these habitats. Sand dunes also offer ecosystem services and socio-economic benefits, as do all intertidal habitats. Grazing can be a useful tool for sand dune management to keep vegetation under control.

Two major types of sand dune system are represented in the Solway Firth. The largest acidic dune system on the west coast of Scotland, Torrs Warren at the head of Luce Bay, is in part a ‘hindshore’ type of dune, and has a variety of designations (SSSI, SAC, Ramsar site) to restore the dunes to favourable condition. This type of sand dune develops above beaches with a good supply of sand and an onshore prevailing wind which drives sand inland as a series of dune ridges or mobile crescent-shaped dunes. They occur in the most exposed sectors of the Irish Sea. ‘Bay’ dunes occur along the coast between Silloth and Maryport. These form where the shoreline is exposed to prevailing winds but there are no major headlands to trap the sand.

Many of the major dune habitat types are well represented in the Solway Firth. The embryo dune communities are characterised by species such as sand couch-grass (Elymus farctus) which is adapted to rapidly changing sand levels. The mobile or yellow dunes which occur landward of these are typically dominated by species such as marram grass (Ammophila arenaria). Both these grass species are important in the accretion of sand to form dune systems. Yellow dunes are so-called because there is little accumulation of organic matter in the sand and so the sand retains its original colour. With increasing stability and vegetation cover thin soils start to form within the semi-fixed or grey dunes. These are dominated by species such as sand sedge (Carex arenaria). Behind these dunes acidic, neutral or calcareous fixed dune grasslands occur, often with depressions or dune slacks where the water table can be at or near the surface for part of the year. Where dune grassland has become leached of calcium, heather (Calluna vulgaris) can establish and form dune heath. There are also often wetter marshy areas formed between the sand dune system and the grazing land which occurs landward of them.

Torrs Warren encompasses the largest and most complex system of beach and dune systems in the south of Scotland. It is internationally important for the generally undisturbed dune habitat and the high diversity of plant communities which it supports. The list of higher plants exceeds 220 species with abundant populations of lesser twayblade orchid (Listera cordata) and shepherd’s cress (Teesdalia nudicaulis). Several rare or notable species of flies and beetles have been recorded and the site is nationally important for the water-beetles, woodlice and grasshoppers which have been recorded.

In Scotland there is also ‘a narrow belt of Marram-dominated dunes…from Southerness to Mersehead (Site of Special Scientific Interest) and at Port Logan (Local Wildlife Site). At the head of Brighouse Bay (Site of Special Scientific Interest) there is a small area of embryo dunes and dune grassland. Narrow belts of dune habitat occur elsewhere on the Galloway coast, for example at Sandyhills Bay, Almorness, Fleet Bay, Monreith, and Killantringan Bay’ (Dumfries and Galloway Biodiversity Partnership, 2009). Royal Society for the Protection of Birds (RSPB) Mersehead also features coastal dune and dune grassland habitats.

Sand dunes are one of three intertidal soft coast habitats mapped throughout Scotland by NatureScot as part of the Habitat Map of Scotland. The data covering the Scottish side of the Solway is available and can be explored through links on the NatureScot Habitat Map of Scotland page, available here.

Silloth Dunes and Mawbray Banks form part of an extensive coastal dune system extending from Silloth to Dubmill Point. The site illustrates the transition from vegetated shingle bank through mobile and fixed sand dune communities to dune grassland and maritime heath. The areas of acidic dune grassland and heath are of particular note as they provide an example of this now rare and restricted habitat in Cumbria. These dunes are particularly important for the notable colonies of the rare and locally restricted Isle of Man cabbage (Rhynchosinapis monensis) and sand leek (Allium scorodoprasum). Other species present include burnet rose (Rosa pimpinellifolia), bloody cranesbill (Geranium sanguineum), and common restharrow (Ononis repens). The Mawbray Banks dune grasslands and rare dune heath are home to the heather mining bee (Andrena fuscipes) (which collect pollen from bell heather), and the heath bumblebee (Bombus jonellus), although the invasive Japanese Rose (Rosa Rugosa) has become a dominating species on the Mawbray Banks dunes. Rosa Rugosa has also dominated dunes at Beckfoot which the Solway Coast Area of Outstanding Natural Beauty (Solway Coast AONB) have tried to control by removal.

.

 

Typical Sand Dune Habitat.
Solway Firth Partnership (1996)

 

The variety of species which can be found on Solway sand dunes depends on the type of dune and area of the dune. The habitat is important for invertebrates, flowering plants, non-flowering plants, reptiles, amphibians, fungi and lichen. Natterjack toads (Epidalea calamita) are among the species which can be found on the coastal sand dunes on both sides of the inner Solway, breeding in shallow pools in dune slacks. See the DGLBAP for a full assessment of the flora and fauna which can be found on dunes on the Scottish side of the Firth.  

Dune habitat is also under potential threat, and is at risk of habitat loss. Torrs Warren dunes are included in an area of military activity. This restriction could potentially damage dune habitats through military activity, but also offers reduced public interaction with the dunes, likely benefitting the biodiversity of the dunes. Recreational use of the dunes has the potential to significantly damage this habitat. Boardwalks, maintained pathways and fenced off sensitive areas are some of the ways this issue is managed. However, there have been ongoing issues with vehicles such as quad bikes and motorbikes accessing and driving over the dunes. This is an increasing issue along the inner Scottish Solway since the introduction of COVID-19 pandemic regulations. This type of behaviour has also been an issue on the sand dunes at Mawbray Banks but is being addressed in an attempt to remind visitors to the Solway Coast AONB that this behaviour is dangerous for wildlife and is illegal. There could be issues with the expected increase in domestic tourism as a result of COVID-19 restrictions easing with visitors trampling and damaging sand dunes through inappropriate practices, such as using barbecues and camping.

Overstabalisation of sand dunes reduces the open sand areas throughout dune habitats. Species which thrive in the dunes need this open sand habitat, and are under pressure through habitat loss. The growing succession zone of sand dune habitat, reduces the area available for embryo dunes and fixed dunes. The ‘Dynamic Dunescapes‘ project is attempting to help combat this issue. Grune Point and Silloth dunes are two of the sites included in the ambitious project seeking to re-establish the dynamic characteristic of dunes through a variety works. The creation of additional new natterjack toad pools, the opening of areas near the natterjack pools to expose bare sand, introducing small native breed cattle, stock fencing, scrub control, the removal of the unstable timber boardwalk and replacement with a new path, and the ongoing removal and control of the invasive Japanese Rose (Rosa Rugosa) are all actions which have been/will be taken as part of conservation efforts at the Mawbray Banks dunes. For more information and updates on the ongoing work see the Solway Coast AONB nature recovery page for the dunes here.

A webinar organised by Solway Firth Partnership and Solway Coast AONB was streamed in 2021 on the Dynamic Dunes on the Solway. This webinar included presentations from the Dynamic Dunescapes project, Royal Society for the Protection of Birds Mersehead, and Solway Coast AONB. The webinar is available here.

 

Image; Mawbray Dunes © Solway Coast Area of Outstanding Natural Beauty

Intertidal rock, sediments and biodiversity

Maritime Cliffs

Maritime cliffs have a very limited distribution within the eastern Irish Sea and are confined mostly to the north coast of the Solway and St Bees Head in Cumbria.

Typically the cliffs support thrift, otherwise known as sea pinks (Armeria maritima), common scurvygrass (Cochlearia officinalis), english stonecrop (Sedum anglicum) and sea campion (Silene maritima) with sea spleenwort (Asplenium marinum) present in damp crevices. Rock samphire (Crithmum maritimum) and the rare rock sea lavender (Limonium binervosum) are also present on cliffs in the Solway. Near the top of the cliffs species such as bloody cranesbill (Geranium sanguineum), wood vetch (Vicia sylvatica), orpine (Sedum telepbium) and soft shield fern (Polystichum setiferum) occur. The Rhins of Galloway cliffs have a variety of wildflowers, detailed in the Solway Firth Partnership ‘Flower Guide’, along with where and when you’re most likely to find the flower, published in 2021, available here. Along dry sand cliff tops, such as at St Bees Head, grassland with species such as dyer’s greenweed (Genista tinctorial) alternate with patches of western gorse (Ulex galli) and heather (Calluna vulgaris).

St Bees Head is the most westerly point on the Cumbria coast and consists of a 6 km length of sheer cliff face, cliff top vegetation, cliff fall rubble, shingle and wave- cut platform. The sheer cliffs provide the outstanding biological interest at St Bees with the only breeding site on the coast of Cumbria for a variety of colonial seabirds (see Birds). The cliff face supports a diverse flora in the crevices and ledges of the crumbling sandstone.

Maritime cliffs along the Scottish coast are variable, however, ‘only very small areas of low soft cliffs occur, mostly in the inner Solway. Hard cliffs with vertical exposures are more typical of the outer Solway, extending very approximately to 11km. A further 97km is composed of coastal slopes with grassland, scrub and woodland, not including slopes behind raised beaches. Coastal heath occurs only in very small pockets, particularly on the Rhins. The maximum cliff height in Dumfries & Galloway is 110m at Dunman, near Mull of Galloway’ (Dumfries and Galloway Biodiversity Partnership, 2009).

The best example of a maritime cliff on the north side of the Solway occurs at the Mull of Galloway where there is a seabird colony of fulmars (Fulmarus glacialis), kittiwakes (Rissa tridactyla), guillemots (Uria aalga) and razorbills (Alca torda).

The cliffs support a wide variety of coastal plant communities. Cliffs extend around the west side of the Rhins of Galloway, with only the occasional low sandy inlet such as at Port Logan or Portpatrick. In places, such as at Southwick, the cliffs have been colonised by woodland providing a lichen-rich habitat; Ravenshall Wood is an important example. Cliffs are absent from the inner Solway. According to the DGLBAP other important maritime cliffs can be found around;

  • Portling [Brandy Cove and Pipers Cave] to Castlehill Point
  • Balcary to Torrs Point
  • Borgue Coast
  • Burrow Head, and the west coast of the Rhins
  • Rough Island
  • Hestan Island
  • Islands of Fleet
  • Scare Rocks (Dumfries and Galloway Biodiversity Partnership, 2009).

Important areas for coastal scrub and woodland occur at Ravenshall and Southwick, while there are many examples of sea caves along the Solway coast, including Barlocco Heughs, Dove Cave and Cave of Uchtriemackean (Dumfries and Galloway Biodiversity Partnership, 2009).

There are a number of Solway caves which often form an important part of history, folklore and oral history around the Solway, acting as inspiration from which the culture of the area has developed. The origins of place names of some Solway caves are explored in the Solway Firth Partnership publication ‘Caves and Graves’ (available here) which was published as part of the Coastwise Project. Not only do these caves and maritime cliffs provide recreational draw for coastal walking and local exploring, but provide educational and historic resource for visitors and locals. Given the difficulty of accessing cliff faces there is limited disturbance to this habitat, with rock climbing and scrambling being some of the limited activities. Caves may, on the other hand, create a draw for increased tourism and recreation which could potentially cause disturbance or damage to species and vegetation. This is likely to be limited by factors such as lack of awareness of many caves, and difficulty accessing them due to tidal or weather conditions.

 

Image; Portpatrick Cliffs. © E. Baruah

Intertidal rock, sediments and biodiversity

Sandy Beaches

Both Dumfries and Galloway and Cumbria have expansive sandy beaches with species often hidden under sand of a variety of grain sizes depending on the wave action. Exposed sandy beaches tend to have finer sediments than found on sheltered beaches.

Sandy beaches on the Scottish side of the Firth include extensive areas such as at the head of Luce Bay and west of Southerness to Mersehead. Sand is sometimes even included in the place name for sandy areas of the coast such as Sandyhills and Sandgreen. Other notable sandy beaches include Port Logan and Broadsea Bay, with smaller areas of beach throughout the coastline such as; Nun Mill Bay, Brighouse Bay, Carrick, Mossyard.

On the Cumbrian side of the Solway sandy beaches occur all along the coast, often interspersed with shingle or rocky coastline. Maryport has a sandy beach to the east of Maryport Marina and lighthouse, there are areas of sandy beach at Allonby Bay, sandy beach east from Crosscannonby to Allonby, and Dubmill to Silloth, and sandy and shingle beach at Skinburness. When looking at the coast during low tide there appears to be vast areas of sandy beach due to the sandflats exposed at low tide such as the sandy area seaward of saltmarsh at Cardurnock.

Small species are more common on sandy beaches, outnumbering larger species. Overall on sandy beaches around the Solway Coast ‘bristleworms Polychaete, bivalve molluscs and amphipod crustaceans are abundant and total biomass may be enormous…The upper shore of free-draining beaches of coarse sand is a hostile environment for marine life and only a few burrowing invertebrates such as amphipods (Bathyporeia spp), an isopod (Eurydice pulchra) and a tube worm (Scolelepis squamata) are likely to occur to any extent’ (Dumfries and Galloway Biodiversity Partnership, 2009). The stability of a sandy beach will directly impact the species of plant found in the upper ranges of this intertidal environment, with pioneer plant species (such as frosted orache (Atriplex laciniata), sea sandwort (Honckenya peploides), sea rocket (Cakile maritima) and prickly saltwort (Salsola kali)) most likely to be found. These plants may be negatively impacted by trampling from visitors to sandy beaches, as they are high value areas for tourism and recreational activities.

Sandy beaches are often flooded with tourists and locals on sunny, warm days. There is the potential for sandy beaches around the Solway to be under increasing tourism pressure in the future as the COVID-19 pandemic is likely to drive an increase in domestic tourism, at least in the short term. This poses a risk for sandy beaches being damaged, littered, and the wildlife disturbed.

 

Image; Crosscanonby © Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Strandline

A strandline is the high water mark where debris is deposited twice a day with the tides. The strandline provides an indicator to visitors of the large tidal range of the Solway. The low tide strandline can illustrate the difference between low and high water. The majority of strandlines around the Solway feature deposited seaweed, often ripped from their holdfasts by turbulent sea, and driftwood which has been washed in, although some strandlines can feature vegetation. Vegetated strandlines are common along much of the Cumbrian and Dumfries and Galloway coastline, with the exception being at cliffs and steep shores. These environments tend to lack strandlines as the accumulation of debris is difficult unless it becomes caught in the rocks. Accumulation of material on the Solway coast is more significant on the Scottish coast due to the Solway’s tides, currents, frequent bays and inlets, and the fact that the coast is sheltered from the full force of waves from the Atlantic Ocean by Ireland and the Isle of Man. The prevailing winds also have a significant impact on the overall movement of floating material towards the Scottish Solway coast. Solway Firth Partnership has a ‘Beachcombers Guide to the Solway Coast Strandline‘ available online, which looks as common sights on the Scottish Solway strandline.

Common strandline sights include;

  • Egg cases – Also known as ‘Mermaid’s Purses’ from sharks, skates and rays in the Solway (See Sharks, Skates, and Rays).
  • Common whelk egg cases & Whelk shells
  • Marine Litter (discussed below)
  • Shells – Crab, cockle, winkle, whelk, mussel are all common shells to find
  • Seaweeds – kelp, wracks
  • Deceased species
  • Less common shells – blue rayed limpet (Patella pellucida), necklace shell (Euspira catena)
  • Salt tolerant plants- frosted orache (Atriplex laciniata), Sea Sandwort (Honckenya peploides), Sea Rocket (Cakile maritima), Prickly Saltwort (Salsola kali). The strandlines left by the highest spring tides are often colonised by annual plants such as sea rocket, which have adapted to survive in very punishing conditions.

A growing issue for strandlines around the Solway, and the world, is marine litter (see Marine Litter). The strandline is often where marine litter is deposited or caught up in natural strandline debris. This is a huge issue, not only for humans and the species which rely on this habitat, but for the wider food web of terrestrial and marine species. This issue is compounded by the fact that marine litter caught in strandline debris may be difficult to find and remove, often being microplastics or hidden/caught in natural debris, and therefore very time consuming to collect.

Given the seaweed found in this habitat is often rotting, invertebrates such as sandhoppers (Talitris saltator) thrive, in turn providing prey for a variety of birds.

A full assessment of the species which can be found in strandline habitats in Dumfries and Galloway is available in the DGLBAP, available here.

 

Image; Strandline at Sandyhills © G. Reid/ Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Recent trends

The harvesting of cockles was significant in the 1980’s and 1990’s, which affected the stock and associated intertidal biodiversity. Cockle fisheries in the Scottish Solway Firth were closed in 2011 under the Inshore Fishing (Prohibition of Fishing for Cockles) (Solway Firth) (Scotland) Order 2011, to allow recovery. This closure followed a five-year Solway Firth Regulating Order (2006-2011) managed by the Solway Shellfish Management Association (dissolved 2017). This closure was due to concerns over the sustainability of the species in the region, having been commercially harvested since 1987. There is a potential opportunity to reopen the cockle fishery. However, a 2014 study (The Solway Cockle Fishery Management Study) identified challenges due the inconsistent quality of the cockles and restricted demand (Marine Scotland Science, 2015). According to the North Western Inshore Fisheries and Conservation Authority (NWIFCA) the three cockle beds on the English Solway: Middle Bank Cockle Bed, Beckfoot Cockle Bed and Cardurnock Flats Cockle Bed, are currently closed under NWIFCA Byelaw 3 Paragraph 12 due to low stocks. For more information on cockle fishing in the Solway see the Sea Fisheries section of the Solway Review, within the Productive chapter.

There has been a recent trend of research and study focussed on intertidal and subtidal habitats such as native oyster beds, seagrass beds, and saltmarsh looking at restoration and conservation of these environments which offer multiple benefits for people in the immediate vicinity and further afield. Natural flood defence and carbon storage and sequestration are being increasingly studied as they are recognised as valuable and important ecosystem services which can help reduce the effects of climate change.

However, climate change is also an increasing threat to intertidal habitats around the UK. These habitats are at risk from both direct (temperature, rainfall) and indirect (sea-level rise, increased flooding, erosion) impacts from rising temperatures. A 2020 Marine Climate Change Impacts Partnership paper (Burden et al, 2020) looks at the impacts the intertidal environments; saltmarsh, shingle, machair, sand dunes, and maritime cliffs and slopes. As seen in the information above 4 out of these 5 habitats are found around both shores of the Solway Firth. This paper provides an overview of the the UK extent of these habitats, as well as (anthropogenic and natural) processes likely to be affected by climate change, and challenges. Although these are primarily in a UK-wide context the paper provides an excellent overview of climate change impacts in these habitats.

The invasive non-native species (INNS) common cord grass (Spartina anglica) continues to spread posing a threat to native cordgrass (Spartina maritima), and risking the development of a monoculture. With growing concern that climate warming could make the Solway an increasingly suitable area for other INNS to become established there is an ongoing threat to biodiversity in the intertidal environment, and wider marine environment, of the Solway. See Marine Invasive Non-Native Species for more information about INNS in the Solway.

Honeycomb worm reef growth trends are unclear but there is no evidence of decline.

In recognition of the importance of these features, many sites have been granted protected status (See Protected Areas).

Intertidal habitats are assessed as part of the ‘benthic habitats’ descriptor for the purpose of assessing progress towards achieving ‘Good Environmental Status’ (GEnvS). Achieving GEnvS in the marine environment is required as per the Marine Strategy Framework Directive to provide more effective marine environment protection and sustainable use. The 2019 updated assessment of the second implementation cycle of the UK’s Marine Strategy looks at the progress the UK has made towards GEnvS and further action required. Overall, the extent which intertidal environments have progressed towards GEnvS is ‘uncertain’, with some areas of saltmarsh not consistent with GEnvS and climate change reducing the resilience of some rocky shore communities against anthropogenic pressures (Department for Environment, Food & Rural Affairs, 2019). Targets for intertidal seagrass bed communities have been met for the Celtic Seas, including the Irish Sea, but with low confidence as the assessments only cover 8/475 coastal water bodies, among other knowledge gaps. Among the indicators used to assess progress towards GEnvS for benthic habitats are; intertidal seagrass, intertidal saltmarsh, intertidal community index, and intertidal rocky shore. For more information on the assessments of; intertidal community response to temperature change (Intertidal Community Index), the condition of intertidal seagrass communities (determined using Water Framework Directive (WFD) Methods), the condition of intertidal saltmarsh communities (determined using WFD Methods) although the Irish Sea is not assessed, and intertidal rocky shore macroalgae communities (determined using WFD Methods), click the links for each topic included above or explore the Marine Online Assessment Tool.

As mentioned above, the long-term effects of COVID-19 from increased visitors and issues related to visitors such as litter, barbecue damage, trampling, or disturbance to habitats and species are unknown at present.

 

Image; Cockle shell. © N. Coombey/ Solway Firth Partnership

Intertidal rock, sediments and biodiversity

Priority habitats and pressures

 

Priority marine habitats found on/in intertidal rock and sediments;

Scottish Priority Marine Features (PMF) List available here.
UK Biodiversity Action Plan (UK BAP)* Habitat descriptions available here. Habitat descriptions for each specific priority habitat are available here.
Species and Habitats of Principal importance (SPI) England. List available here.
Features of Conservation Interest (FOCI) (Marine Conservation Zone Features) England. List available here.
Scottish Biodiversity List (SBL) Scotland. List available here.

 

*Note; The UK Biodiversity Action Plan has now been succeeded by the ‘UK Post-2010 Biodiversity Framework‘, published in July 2012. Despite this, the UK BAP lists of priority species and habitats are invaluable for Scotland and England when drawing up their own biodiversity lists.

Category Broad Feature Category Type Pressures/ Sensitivities Presence
Biogenic reefs Blue mussel beds FOCI/ SBL/ SPI/ PMF/ UK BAP Storm damage, smothering, cold weather, coastal development, anchoring and other activities which cause physical disturbance, harvesting Scotland, England
Honeycomb worm reef FOCI/ SBL/ SPI/ UK BAP Change in sediment dynamics, natural mobility, exploitation, coastal development, water abstraction, disturbance Scotland, England
Habitats Coastal vegetated shingle SBL/ SPI/ UK BAP Change in sediment dynamics, natural mobility, exploitation, coastal development, water abstraction, disturbance Scotland, England
Coastal saltmarsh SBL/ SPI/ UK BAP Land claim, erosion, coastal squeeze, sediment dynamics, cord grass, unsuitable grazing, other human influences, climate change, internal erosion (expansion of creeks) Scotland, England
Intertidal mudflats SBL/ SPI/ PMF/ UK BAP Physical disturbance, changes in wave regimes, INNS, sea-level rise, pollution, contamination, nutrient/organic enrichment and siltation Scotland, England
Intertidal boulder communities FOCI*/ SBL/ SPI/ UK BAP* Boulder turning for peelers and winkles, public shore visits and water quality Scotland, England
Seagrass beds FOCI/ SBL/ SPI/ PMF/ UK BAP Suction and bait dredging, coastal developments Scotland, England
Sheltered muddy gravels FOCI/ SBL/ SPI/ UK BAP Physical disturbance, bait digging, fisheries, organic enrichment, persistent bio-accumulating chemicals, INNS Scotland, England
Coastal and floodplain grazing marsh SBL/ SPI/ UK BAP Predating unsuitable flood defences, eutrophication, flooding, climate change (sea level rise), pollution Scotland/ England
Coastal Sand Dunes SBL/ SPI/ UK BAP Erosion, recreation, antisocial behaviour, stabilisation, INNS, pollution, litter Scotland/ England
Maritime Cliffs and Slopes SBL/ SPI/ UK BAP Erosion, coastal development, recreation (rock climbing), climate change (sea level rise), coastal defence (on soft cliffs) Scotland/ England
Estuarine rocky habitats FOCI/ SBL/ SPI/ UK BAP Water quality, dredging, coastal defence, climate change (sea level rise), INNS, recreation Scotland/ England
Peat and clay exposures FOCI/ SPI/ UK BAP Development, smothering, climate change, bait collection, coastal defence, INNS (American piddock, Petricola pholadiformis) Scotland/ England

*intertidal under boulder communities

Intertidal rock, sediments and biodiversity

References

Cumbria Biodiversity Data Centre. (n.d.) Available here. (Accessed: 10.03.18)

Cumbria Biodiversity Data Centre (2016). Habitat statement – Coastal Intertidal Habitats. Available here. (Accessed: 01.04.21)

Cumbria Biodiversity Partnership (2001). The Cumbria Biodiversity Action Plan. Available here. (Accessed: 01.04.21)

Joint Nature Conservation Committee and Department of Environment, Food and Rural Affairs (on behalf of the Four Countries’ Biodiversity Group). (2012). UK Post-2010 Biodiversity Framework. Available here. (Accessed: 07.07.18)

Joint Nature Conservation Committee (2007). UK Biodiversity Action Plan Priority Marine Species. Available here. (Accessed: 07.03.18)

Joint Nature Conservation Committee (2007). UK Biodiversity Action Plan Priority Habitats. Available here. (Accessed: 07.03.18)

Marine Life Information Network (n.d.). Habitats listed as Features of Conservation Interest (FOCI). Available here. (Accessed: 14.05.20)

Marine Life Information Network (n.d.). Habitats listed as ‘habitats of principal importance’. Available here. (Accessed: 14.05.20)

Marine Management Organisation. (n.d). Marine Planning Evidence Base. Available here. (Accessed: 14.05.18)

Marine Scotland (n.d.). National Marine Plan Interactive. Available here. (Accessed: 06.08.19)

Michael T. Burrows, Nova Mieszkowska, John Baxter, Cristina Vina-Herbon, Gemma Singleton, Karen Robison & Mike Young (2018). Intertidal community index (MarClim). UK Marine Online Assessment Tool. Available here. (Accessed: 05.04.21)

Mills, F., Sheridan, S. and Brown S., (2017). Clyde Marine Region Assessment. Clyde Marine Planning Partnership. pp 231. Available here. (Accessed: 14.05.18)

NatureScot (2020). Priority Marine Features in Scotland’s Seas. Available here. (Accessed: 01.04.21)

NatureScot (2020). Scottish Biodiversity List. Available here. (Accessed: 04.05.21)

Phillips, G., McGruer, K., Crook, D., Doria, L., Herbon, C., Khan, J., Mackie, T., Singleton, G. & Young, C. (2018). Condition of intertidal rocky shore macroalgae (seaweed) communities in coastal waters determined using Water Framework Directive methods. UK Marine Online Assessment Tool. Available here. (Accessed: 05.04.21)

Phillips, G., McGruer, K., Crook, D., Doria, L., Herbon, C., Khan, J., Mackie, T., Singleton, G. & Young, C. (2018). Condition of intertidal saltmarsh communities in coastal waters determined using Water Framework Directive methods. Marine Online Assessment Tool. Available here. (Accessed: 05.04.21)

Phillips, G., McGruer, K., Crook, D., Doria, L., Herbon, C., Khan, J., Mackie, T., Singleton, G. & Young, C. (2018). Condition of intertidal seagrass communities in coastal waters determined using Water Framework Directive methods. UK Marine Online Assessment Tool. Available here. (Accessed: 05.04.21)

Solway Firth Partnership (1996). The Solway Firth Review, Solway Firth Partnership, Dumfries. Available here. (Accessed 23.07.19)

UK National Ecosystem Assessment (2011). The UK National Ecosystem Assessment Technical Report. UNEP-WCMC, Cambridge. Available here. (Accessed: 28.05.18)

 

In-Text References;

Baxter, J.M., Boyd, I.L., Cox, M., Donald, A.E., Malcolm, S.J., Miles, H., Miller, B., Moffat, C.F., (Editors), (2011). Scotland’s Marine Atlas: Information for the national marine plan. Marine Scotland, Edinburgh. pp 191. Available here. (Accessed: 22.07.19)

Burden, A., Smeaton, C., Angus, S., Garbutt, A., Jones, L., Lewis H.D.and Rees. S.M. (2020). Impacts of climate change on coastal habitats relevant to the coastal and marine environment around the UK. MCCIP Science Review 2020, 228–255. Available here. (Accessed: 01.04.21)

C-SIDE (n.d.) The C-SIDE Project. Available here. (Accessed: 22.07.20)

Cutts, N. & Hemmingway, K. (1996). The Solway Firth: broad scale habitat mapping. Scottish Natural Heritage Research, Survey and Monitoring Report No. 46. Available here. (Accessed: 22.07.20)

Department for Environment, Food & Rural Affairs (2019). Marine Strategy Part One: UK updated assessment and Good Environmental Status. Available here. (Accessed: 22.07.20)

Dumfries and Galloway Biodiversity Partnership (2009). Dumfries and Galloway Local Biodiversity Action Plan. Available here. (Accessed: 01.04.21)

Foster and Davidson (2018). Angiosperm Monitoring for the EU Water Framework Directive 2013 – 2015: Baseline seagrass surveys of the Montrose Basin, Eden Estuary, Forth Estuary and Loch Ryan. Report Number: MB-01/2018. Available here. (Accessed: 01.04.21)

Haynes, T.A. (2016). Scottish saltmarsh survey national report. Scottish Natural Heritage (now NatureScot). Commissioned Report No. 786. Available here. (Accessed: 22.07.20)

Historic England (n.d.). Intertidal and Coastal Peat Database, Cumbria. Available here. (Accessed: 28.04.21)

HR Wallingford Limited (2005). Dumfries and Galloway Shoreline Management Plan, Study: Stage 1, Volume 1, Report EX 4963 Rev 2.0. Available here. (Accessed 22.07.19)

Marine Scotland Science (2015). Solway Cockle Fishery Management Study. Available here. (Accessed: 28.07.20)

McKay, D.W. and Fowler, S.L. (1997). Review of the Exploitation of the Mussel, Mytilus edulis, in Scotland. Scottish Natural Heritage (now NatureScot) Review. No 68. Available here. (Accessed: 28.07.20)

Scottish Coastal Archaeology and the Problem of Erosion (SCAPE) (2019). Mesolithic oaks to Mulberry Harbours – 8,000 years of history along the Solway Firth. Available here. (Accessed 27.04.21)

United Kingdom Marine Monitoring & Assessment Strategy (n.d.). Summary of Progress towards Good Environmental Status. Available here. (Accessed: 15.12.20)

 

Image; Rayed trough shell. © N. Coombey/ Solway Firth Partnership