Habitat account - Marine, coastal and halophytic habitats


1330 Atlantic salt meadows (Glauco-Puccinellietalia maritimae

Background to selection

Distribution of SACs/SCIs/cSACs with habitat 1330 Atlantic salt meadows (Glauco-Puccinellietalia maritimae).  Click image for enlarged map.
Distribution of SACs/SCIs/cSACs with habitat 1330 Atlantic salt meadows (Glauco-Puccinellietalia maritimae). Click image for enlarged map.

Description and ecological characteristics

 

Atlantic salt meadows develop when halophytic vegetation colonises soft intertidal sediments of mud and sand in areas protected from strong wave action. This vegetation forms the middle and upper reaches of saltmarshes, where tidal inundation still occurs but with decreasing frequency and duration. A wide range of community types is represented and the saltmarshes can cover large areas, especially where there has been little or no enclosure on the landward side. The vegetation varies with climate and the frequency and duration of tidal inundation. Grazing by domestic livestock is particularly significant in determining the structure and species composition of the habitat type and in determining its relative value for plants, for invertebrates and for wintering or breeding waterfowl. In the UK this Annex I type corresponds to the following NVC types:

 

     

  • SM10  Transitional low-marsh vegetation
  • SM11  Aster tripolium var. discoideus salt-marsh community
  • SM12  Rayed Aster tripolium salt-marsh community
  • SM13  Puccinellia maritima salt-marsh community
  • SM14  Halimione portulacoides saltmarsh community
  • SM15  Juncus maritimus – Triglochin maritima salt-marsh community
  • SM16  Festuca rubra salt-marsh community (coastal examples only)
  • SM17  Artemisia maritima salt-marsh community
  • SM18  Juncus maritimus salt-marsh community
  • SM19  Blysmus rufus salt-marsh community
  • SM20  Eleocharis uniglumis salt-marsh community.

 

Inland stands of SM16 are referable to Annex I type H1340 Inland salt meadows.

 

At the lower reaches of the saltmarsh the vegetation is often naturally species-poor and may form an open sward of common saltmarsh-grass Puccinellia maritima. Further up the marsh, the vegetation becomes herb-dominated and red fescue Festuca rubra becomes more important. The upper saltmarsh shows considerable variation, particularly where there are transitions to other habitats. Communities present may include tussocks of sea rush Juncus maritimus dominating a herb-rich vegetation, and saltpans supporting patches of species-poor vegetation dominated by saltmarsh flat-sedge Blysmus rufus (in the north) or slender spike-rush Eleocharis uniglumis. Grazed saltmarsh in northern Scotland may contain frequent turf fucoid Fucus cottonii.

 

There may be transitions from upper saltmarsh to a number of habitats, including sand dune, machair, coastal shingle, freshwater marshes and woodland. This part of the saltmarsh succession has been particularly vulnerable to destruction by enclosure, usually involving the erection of a sea bank to exclude sea water, and remaining areas are regarded as particularly important for biodiversity conservation.

 

There are marked regional variations in the Atlantic salt meadow communities of the UK. In east and south-east England low to mid-marsh communities predominate, owing to extensive enclosure of the upper marsh. In contrast, the salt meadows of north-west England and south-west Scotland are dominated by extensive areas of grazed upper marsh communities characterised by Puccinellia maritima and saltmarsh rush Juncus gerardii. Swamp communities are particularly common in the upper marsh in south-west England, while Juncus maritimus communities are characteristic of Welsh saltmarshes, and transitional common reed Phragmites australis communities are common in south-east Scotland. Some characteristic plant species of southern saltmarshes are absent from Scotland, while others such as sea-purslane Atriplex portulacoides have a restricted distribution in northern Britain.

European status and distribution

 

This Annex I type is predominantly found on Atlantic coasts in western Europe.

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

 

Atlantic salt meadows occur on North Sea, English Channel and Atlantic shores. There are more than 29,000 ha of the habitat type in the UK, mostly in the large, sheltered estuaries of south-east, south-west and north-west England and in south Wales. Smaller areas of saltmarsh are found in Scotland.

Site selection rationale

 

Sites have been selected to cover the geographical range and ecological variation of Atlantic salt meadows in the UK. The sites selected are for the most part the largest examples of this habitat type, with good structure and function, and which support a well-developed zonation of plant communities within the saltmarsh. There are transitions to other high-quality habitat assemblages at many of the sites that have been selected. Sites with complete sequences of vegetation and transitions to other habitats, such as sand dunes, represent the range of variation of the habitat type, and this has been an important consideration in site selection.


Site accounts

Carmarthen Bay and Estuaries/ Bae Caerfyrddin ac Aberoedd East Wales, Extra-Regio, West Wales and The Valleys
This extensive site in south Wales has a complete sequence of saltmarsh vegetation, from pioneer vegetation through to upper saltmarsh transitions. The grazed saltmarshes include upper margins with sea rush Juncus maritimus and marsh-mallow Althaea officinalis, which are a particularly distinctive ecological feature of this site. The area is also important for transitions from saltmarsh to sand dune and other habitats.
Dee Estuary/ Aber Dyfrdwy Cheshire, East Wales, Extra-Regio, Merseyside, West Wales and The Valleys
The Dee Estuary is representative of H1330 Atlantic salt meadows in the north-west of the UK. It forms the most extensive type of saltmarsh in the Dee, and since the 1980s it has probably displaced very large quantities of the non-native common cord-grass Spartina anglica. The high accretion rates found in the estuary are likely to favour further development of this type of vegetation. The saltmarsh is regularly inundated by the sea; characteristic salt-tolerant perennial flowering plant species include common saltmarsh-grass Puccinellia maritima, sea aster Aster tripolium, and sea arrowgrass Triglochin maritima. In a few areas there are unusual transitions to wet woodland habitats.
Dornoch Firth and Morrich More Extra-Regio, Highlands and Islands
Dornoch Firth and Morrich More is the most northerly site selected for Atlantic salt meadows and represents this habitat type in the northern part of its UK range. The site supports a wide variety of community types, with the characteristic zonation from pioneer to upper marsh vegetation. At Morrich More the saltmarshes lie adjacent to sand dunes and there are important transitions between these habitats.
Essex Estuaries Essex, Extra-Regio
Although the saltmarshes in this area are generally eroding, extensive salt meadows remain and Essex Estuaries represents Atlantic salt meadows in south-east England, with floristic features typical of this part of the UK. Golden samphire Inula crithmoides is a characteristic species of these marshes, occurring both on the lower marsh and on the drift-line. It represents a community of south-east England also found to the south in mainland Europe.
Fal and Helford Cornwall and Isles of Scilly, Extra-Regio
The Fal and Helford is an example of saltmarsh vegetation in a ria (drowned river valley), a physiographic type restricted to south-west England and west Wales. There is a narrow saltmarsh zonation typical of rias, from pioneer to upper marsh, and transitions to woodland where the fringing trees overhang the tidal river, an unusual juxtaposition of vegetation in the UK.
Glannau Môn: Cors heli / Anglesey Coast: Saltmarsh West Wales and The Valleys
This site, which includes both the Braint and Cefni estuaries, forms a complex of saltmarsh and dune habitats lying either side of the dune systems at Newborough Warren. Atlantic salt meadows form the bulk of the saltmarsh vegetation, but much of it is far from typical. In the Braint estuary the vegetation is characterised by unusually large amounts of greater sea-spurrey Spergularia media, whilst in the Cefni estuary the more typical Atlantic salt meadow is subordinate to saltmarsh dominated by sea rush Juncus maritimus. In fact, this is one of the largest stands of Juncus maritimus saltmarsh in Britain, and has affinities with 1410 Mediterranean salt meadows (Juncetalia maritimi), an Annex I vegetation type that is not now considered to occur in the UK.
Morecambe Bay Cumbria, Extra-Regio, Lancashire
Morecambe Bay is characteristic of saltmarshes in north-west England, with large areas of closely grazed upper marsh. The mid-upper marsh vegetation is strongly dominated by the saltmarsh-grass/fescue Puccinellia/Festuca communities, of which over 1,000 ha occur here, and by smaller areas of saltmarsh rush Juncus gerardii community. NVC type SM18 Juncus maritimus community is also more strongly represented here than elsewhere in England. The plant species include both southern elements, such as lesser centaury Centaurium pulchellum, and northern elements, such as saltmarsh flat-sedge Blysmus rufus and few-flowered spike-rush Eleocharis quinqueflora.
North Uist Machair Highlands and Islands
The saltmarshes of north-west Scotland are usually small, and differ considerably from other saltmarshes in Europe, notably in their morphology, the scarcity or absence of a pioneer zone and the prevalence of the turf fucoid Fucus cottonii in closely-grazed turf. North Uist Machair is one of the larger composite examples. Many species dominant on southern British saltings are completely absent, and much of the expanse comprises common saltmarsh-grass Puccinellia maritima, sea-milkwort Glaux maritima, plantain Plantago spp. and thrift Armeria maritima, with red fescue Festuca rubra and saltmarsh rush Juncus gerardii at higher levels. Transitions to terrestrial habitats tend to be richer in species, featuring silverweed Potentilla anserina and smooth meadow-grass Poa pratensis while transitions to fens have saltmarsh flat-sedge Blysmus rufus and sea arrowgrass Triglochin maritimum. Locally there are also fine transitions to dune and machair, making this one of the most varied of north-western saltmarshes.
Plymouth Sound and Estuaries Cornwall and Isles of Scilly, Devon, Extra-Regio
This site is representative of a ria system in south-west England. The well-developed salinity gradient supports Atlantic salt meadow together with natural transitions to brackish and freshwater communities, including reedbeds supporting the only UK population of triangular club-rush Schoenoplectus triqueter. Some stands of saltmeadow are structurally and botanically diverse and include sea club-rush Scirpus maritimus and saltmarsh rush Juncus gerardii, with red fescue Festuca rubra, sea rush J. maritimus and thrift Armeria maritima at higher levels. The locally common parsley water-dropwort Oenanthe lachenalii is also found in some parts of the site, and there are stands of sea-purslane Halimione portulacoides, which is unusual in Cornwall. The Atlantic salt meadows make a vital contribution to the structure and function of the estuary and the other habitats within it.
Severn Estuary/ Môr Hafren Dorset and Somerset, East Wales, Extra-Regio, Gloucestershire, Wiltshire and Bristol/Bath area
Habitat occurrence account not yet available.
Solent Maritime Extra-Regio, Hampshire and Isle of Wight, Surrey, East and West Sussex
The Solent contains the second-largest aggregation of Atlantic salt meadows in south and south-west England. Solent Maritime is a composite site composed of a large number of separate areas of saltmarsh. In contrast to the Severn estuary, the salt meadows at this site are notable as being representative of the ungrazed type and support a different range of communities dominated by sea-purslane Atriplex portulacoides, common sea-lavender Limonium vulgare and thrift Armeria maritima. As a whole the site is less truncated by man-made features than other parts of the south coast and shows rare and unusual transitions to freshwater reedswamp and alluvial woodland as well as coastal grassland. Typical Atlantic salt meadow is still widespread in this site, despite a long history of colonisation by cord-grass Spartina spp.
Solway Firth Cumbria, Extra-Regio, South Western Scotland
The Solway Firth, between north-west England and south-west Scotland, has been little affected by enclosure, with the result that it demonstrates unusually large areas of upper marsh and transitions to freshwater grassland communities. There is a greater proportion of sand in the substrate than is found in more southern saltmarshes. The mid-upper marsh is heavily dominated by saltmarsh rush Juncus gerardii community with smaller areas of the saltmarsh-grass/fescue Puccinellia/Festuca communities. The site has been selected because of its large size and uninterrupted transitions. Some of the species present, for example sea-purslane Atriplex portulacoides, common sea-lavender Limonium vulgare and lax-flowered sea-lavender Limonium humile, are at their northern limit in the UK.
The Wash and North Norfolk Coast East Anglia, Lincolnshire
This site on the east coast of England is selected both for the extensive ungrazed saltmarshes of the North Norfolk Coast and for the contrasting, traditionally grazed saltmarshes around the Wash. The Wash saltmarshes represent the largest single area of the habitat type in the UK. The Atlantic salt meadows form part of a sequence of vegetation types that are unparalleled among coastal sites in the UK for their diversity and are amongst the most important in Europe. Saltmarsh swards dominated by sea-lavenders Limonium spp. are particularly well-represented on this site. In addition to typical lower and middle saltmarsh communities, in North Norfolk there are transitions from upper marsh to freshwater reedswamp, sand dunes, shingle beaches and mud/sandflats.

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

Alde, Ore and Butley Estuaries East Anglia
Bann Estuary Northern Ireland
Chesil and the Fleet Dorset and Somerset
Culbin Bar Highlands and Islands
Drigg Coast Cumbria
Humber Estuary East Yorkshire and Northern Lincolnshire, Extra-Regio, Lincolnshire
Kenfig/ Cynffig East Wales
Moine Mhor Highlands and Islands
Murlough Extra-Regio, Northern Ireland
North Antrim Coast Northern Ireland
Pembrokeshire Marine/ Sir Benfro Forol Extra-Regio, West Wales and The Valleys
Pen Llyn a`r Sarnau/ Lleyn Peninsula and the Sarnau East Wales, Extra-Regio, West Wales and The Valleys
Strangford Lough Northern Ireland
 

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