Portland Harbour Shore

Site of Special Scientific Interest · 50.5907, -2.4606

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Dorset County King Charles Way - Rufus Castle to Lulworth Cove National TrailSouth West Coast Path National Trail

Condition (Natural England)

Favourable (8) Unfavourable No Change (2)
UnitFeatureConditionArea (ha)Assessed
SY669765 — Favourable 8.91 2021-11-16
SY669767 — Favourable 2.78 2021-11-16
SY670753 — Favourable 9.19 2009-10-07
SY671770 — Favourable 8.91 2021-11-16
SY672771 — Favourable 8.91 2021-11-16
SY674773 — Favourable 8.91 2021-11-16
SY682784 — Unfavourable No Change 2.28 2022-03-30
SY683784 — Favourable 8.91 2021-11-16
SY685787 — Unfavourable No Change 1.03 2022-03-30
SY687786 — Favourable 8.91 2021-11-16

Climate exposure

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

Coastal

Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.

Habitats

Salt marsh

Geology & landscape

Geological Period: Jurassic · Rock Type: Siltstone

Landscape processes: Coastal

Description

Portland Harbour Shore SSSI Description The cliffs along the north-western shore of Portland Harbour are of outstanding geological importance. The site also includes maritime grassland and the intertidal shore itself. There are outstanding sections in the Corallian (Oxfordian) rocks. The site includes the type localities for several formations including the Nothe Clay, and Nothe Grit, Bencliff Grit and the Sandsfoot Clay, and Grit: several of which are more thickly developed here than in the standard section a few miles to the east at Osmington. The section here covers much of the Oxfordian time interval from the Nothe Grit to the Passage Beds at the very top of the stage, and exposure of the Sandsfoot Clay – Ringstead Coral Bed interval surpasses even that of the type section. A key site in Jurassic stratigraphic studies. The site contains the thickest baylei – cymodoce Zone Kimmeridge Clay in Dorset. Above a clear junction with the Corallian Beds, an eleven metre section is visible up to the Black Head Siltstone. Historically, Waagen defined the boundary between the Corallian and the Kimmeridge Beds in this section, and the site is important as the source of Rasenia, and in the subdivision of the cymodoce Zone on the basis of its faunal assemblages. An historic locality in studies of Kimmeridgian strata. The Lower Kimmeridge Clay (baylei, cymodoce, mutabilis Zones) of Smallmouth Sands has yielded one of the most varied Kimmeridgian reptile faunas. It is the best site for forms such as the turtles (4 species) and the pterosaurs (3 species). The specimens collected include type specimens of one turtle, two pterosaurs, one sauropod, one ichthyosaur, and possibly a plesiosaur. A key site with a fauna complementing the Kimmeridge Clay vertebrate fauna of the type section in the Isle of Purbeck. The causeway along the south western shore of the Harbour supports extensive, rich maritime grassland, similar to that in the adjacent Chesil and the Fleet SSSI. Characteristic species include sea couch Elytrigia atherica, thrift Armeria maritima, sand sedge Carex arenaria and the local Portland spurge Euphorbia portlandica. There are also patches of saltmarsh vegetation with the uncommon shrubby seablite Suaeda vera.

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
sea couch Elytrigia atherica Not listed in GB list grass poaceae
thrift Armeria maritima CR herb plumbaginaceae
Portland spurge Euphorbia portlandica LC herb euphorbiaceae
shrubby seablite Suaeda vera LC herb amaranthaceae
sand sedge Carex arenaria LC sedge cyperaceae

Plant communities

SM1 — Salt marsh

Zostera communities

Zostera angustifolia, Zostera marina, Zostera noltei, Spartina anglica, Porphyra umbilicalis, Chondria dasyphylla, Polysiphonia nigra, Chara aspera, Chaetomorpha linum, Chaetomorpha tortuosa, Cladophora battersii, Cladophora retroflexa, Ulva intestinalis, Ulva lactuca, Fucus spiralis

SM2 — Salt marsh

Ruppia maritima salt-marsh community

Ruppia maritima

SM3 — Salt marsh

Eleocharis parvula salt-marsh community

Eleocharis parvula

SM4 — Salt marsh

Spartina maritima salt-marsh community

Suaeda maritima, Salicornia europaea, Salicornia perennis, Puccinellia maritima, Spartina anglica, Spartina maritima

SM5 — Salt marsh

Spartina alterniflora salt-marsh community

Puccinellia maritima, Spartina alterniflora, Spartina anglica

SM6 — Salt marsh

Spartina anglica salt-marsh community

Atriplex portulacoides, Suaeda maritima, Aster tripolium, Cochlearia anglica, Spergularia media, Atriplex hastata, Salicornia europaea, Plantago maritima, Limonium vulgare, Puccinellia maritima, Spartina anglica, Catenella caespitosa, Fucus vesiculosus, Fucus vesiculosus ecad volubilis

SM7 — Salt marsh

Arthrocnemum perenne stands

Atriplex portulacoides, Suaeda maritima, Aster tripolium, Spergularia media, Salicornia europaea, Salicornia perennis, Limonium vulgare, Puccinellia maritima, Bostrychia scorpioides

SM8 — Salt marsh

Annual Salicornia salt-marsh community

Atriplex portulacoides, Suaeda maritima, Aster tripolium, Salicornia europaea, Puccinellia maritima, Spartina anglica

SM9 — Salt marsh

Suaeda maritima salt-marsh community

Atriplex portulacoides, Suaeda maritima, Aster tripolium, Salicornia europaea, Puccinellia maritima, Spartina anglica

SM10 — Salt marsh

Transitional low-marsh vegetation with Puccinellia maritima annual Salicornia species and Suaeda maritima

Atriplex portulacoides, Suaeda maritima, Aster tripolium, Spergularia media, Salicornia europaea, Triglochin maritimum, Armeria maritima, Limonium vulgare, Puccinellia maritima, Spartina anglica

SM11 — Salt marsh

Aster tripolium var. discoideus salt-marsh community

Atriplex portulacoides, Suaeda maritima, Aster tripolium, Spergularia media, Salicornia europaea, Salicornia perennis, Plantago maritima, Puccinellia maritima, Spartina anglica, Bostrychia scorpioides, Fucus vesiculosus, Pelvetia canaliculata

SM12 — Salt marsh

Rayed Aster Tripolium on slat marshes

Schoenoplectus lacustris, Juncus bufonius, Suaeda maritima, Aster tripolium, Spergularia marina, Spergularia media, Atriplex hastata, Salicornia europaea, Triglochin maritimum, Plantago maritima, Puccinellia distans, Puccinellia maritima, Spartina anglica

SM13 — Salt marsh

Puccinellia maritima salt-marsh community

Atriplex portulacoides, Juncus gerardii, Suaeda maritima, Aster tripolium, Cochlearia anglica, Cochlearia officinalis, Spergularia media, Atriplex hastata, Salicornia europaea, Salicornia perennis, Triglochin maritimum, Plantago maritima, Armeria maritima, Limonium humile, Limonium vulgare, Glaux maritima, Agrostis stolonifera, Festuca rubra, Puccinellia maritima, Spartina anglica, Spartina maritima, Bostrychia scorpioides, Fucus cottonii

SM14 — Salt marsh

Halimione portulacoides salt-marsh community

Atriplex portulacoides, Juncus maritimus, Suaeda maritima, Artemisia maritima, Aster tripolium, Inula crithmoides, Spergularia media, Salicornia europaea, Salicornia perennis, Triglochin maritimum, Plantago maritima, Armeria maritima, Limonium vulgare, Elytrigia atherica, Puccinellia maritima, Spartina anglica

SM15 — Salt marsh

Juncus maritimus-Triglochin maritima salt-marsh community

Atriplex portulacoides, Carex extensa, Juncus gerardii, Juncus maritimus, Suaeda maritima, Oenanthe lachenalii, Artemisia maritima, Cochlearia anglica, Cochlearia officinalis, Spergularia media, Atriplex hastata, Salicornia europaea, Triglochin maritimum, Plantago maritima, Armeria maritima, Limonium humile, Limonium vulgare, Glaux maritima, Agrostis stolonifera, Festuca rubra, Phragmites australis, Puccinellia maritima, Spartina anglica, Fucus cottonii

SM16 — Salt marsh

Festuca rubra salt-marsh community

Atriplex portulacoides, Carex distans, Carex flacca, Juncus gerardii, Hypnum cupressiforme, Kindbergia praelonga, Rhytidiadelphus squarrosus, Scorzoneroides autumnalis, Cochlearia anglica, Cerastium fontanum, Sagina procumbens, Spergularia media, Atriplex hastata, Salicornia europaea, Lotus corniculatus, Trifolium repens, Triglochin maritimum, Plantago lanceolata, Plantago maritima, Armeria maritima, Limonium vulgare, Glaux maritima, Ranunculus acris, Potentilla anserina, Agrostis stolonifera, Anthoxanthum odoratum, Cynosurus cristatus, Festuca rubra, Holcus lanatus, Puccinellia maritima

SM17 — Salt marsh

Artemisia maritima salt-marsh community

Atriplex portulacoides, Juncus gerardii, Juncus maritimus, Suaeda maritima, Suaeda vera, Artemisia maritima, Cochlearia anglica, Cochlearia officinalis, Spergularia media, Atriplex hastata, Salicornia europaea, Triglochin maritimum, Plantago coronopus, Plantago maritima, Armeria maritima, Limonium vulgare, Glaux maritima, Agrostis stolonifera, Elytrigia atherica, Elytrigia repens, Festuca rubra, Hordeum marinum, Parapholis strigosa, Puccinellia maritima

SM18 — Salt marsh

Juncus maritimus salt-marsh community

Carex distans, Carex extensa, Carex otrubae, Juncus gerardii, Juncus maritimus, Amblystegium serpens, Kindbergia praelonga, Oenanthe lachenalii, Cirsium arvense, Scorzoneroides autumnalis, Sonchus arvensis, Cochlearia officinalis, Silene flos-cuculi, Atriplex hastata, Lotus corniculatus, Trifolium repens, Vicia cracca, Triglochin maritimum, Plantago maritima, Armeria maritima, Rumex crispus, Glaux maritima, Samolus valerandi, Ranunculus acris, Potentilla anserina, Galium palustre, Agrostis stolonifera, Elytrigia repens, Festuca rubra, Holcus lanatus, Poa pratensis, Schedonorus arundinaceus

SM19 — Saline lagoon, Salt marsh

Blysmus rufus salt-marsh community

Blysmus rufus, Carex extensa, Carex lepidocarpa, Carex nigra, Eleocharis quinqueflora, Eleocharis uniglumis, Juncus articulatus, Juncus gerardii, Amblystegium serpens, Calliergonell cuspidatum, Drepanocladus polygamus, Leptodictyum riparium, Oenanthe lachenalii, Scorzoneroides autumnalis, Cochlearia anglica, Trifolium repens, Triglochin maritimum, Triglochin palustre, Plantago maritima, Armeria maritima, Glaux maritima, Potentilla anserina, Agrostis stolonifera, Alopecurus geniculatus, Festuca rubra, Puccinellia maritima

SM20 — Saline lagoon, Salt marsh

Eleocharis uniglumis salt-marsh community

Bolboschoenus maritimus, Carex distans, Carex extensa, Carex nigra, Eleocharis quinqueflora, Eleocharis uniglumis, Juncus articulatus, Juncus gerardii, Leptodictyum riparium, Oenanthe lachenalii, Hydrocotyle vulgaris, Scorzoneroides autumnalis, Atriplex hastata, Trifolium repens, Triglochin maritimum, Triglochin palustre, Plantago maritima, Armeria maritima, Glaux maritima, Samolus valerandi, Potentilla anserina, Galium palustre, Agrostis stolonifera, Alopecurus geniculatus, Festuca rubra

SM21 — Salt marsh

Suaeda vera-Limonium binervosum salt-marsh community

Atriplex portulacoides, Frankenia laevis, Suaeda maritima, Suaeda vera, Artemisia maritima, Cochlearia anglica, Cochlearia danica, Cochlearia officinalis, Sagina maritima, Spergularia marina, Spergularia media, Salicornia europaea, Plantago maritima, Armeria maritima, Limonium bellidifolium, Limonium binervosum, Limonium vulgare, Glaux maritima, Elytrigia atherica, Festuca rubra, Puccinellia maritima

SM22 — Salt marsh

Halimione portulacoides-Frankenia laevis salt-marsh community

Atriplex portulacoides, Frankenia laevis, Suaeda maritima, Spergularia media, Salicornia europaea, Salicornia perennis, Plantago coronopus, Plantago maritima, Armeria maritima, Limonium vulgare, Elytrigia juncea, Festuca rubra, Parapholis strigosa, Puccinellia maritima

SM23 — Salt marsh

Spergularia marina-Puccinellia distans salt-marsh community

Atriplex portulacoides, Juncus bufonius, Suaeda maritima, Spergularia marina, Spergularia media, Atriplex hastata, Salicornia europaea, Triglochin maritimum, Plantago maritima, Polygonum aviculare, Glaux maritima, Agrostis stolonifera, Alopecurus geniculatus, Elytrigia atherica, Festuca rubra, Parapholis strigosa, Puccinellia distans, Puccinellia maritima

SM24 — Salt marsh

Elymus pycnanthus salt-marsh community

Atriplex portulacoides, Juncus gerardii, Juncus maritimus, Hypnum cupressiforme, Suaeda vera, Artemisia maritima, Aster tripolium, Sonchus arvensis, Atriplex hastata, Atriplex littoralis, Beta vulgaris sp maritima, Plantago maritima, Armeria maritima, Limonium vulgare, Glaux maritima, Potentilla anserina, Galium aparine, Agrostis stolonifera, Ammophila arenaria, Elytrigia atherica, Festuca rubra, Parapholis strigosa, Phragmites australis, Puccinellia maritima

SM25 — Salt marsh

Suaeda vera drift-line community

Atriplex portulacoides, Suaeda maritima, Suaeda vera, Artemisia maritima, Cochlearia anglica, Cochlearia danica, Cochlearia officinalis, Spergularia media, Atriplex littoralis, Salicornia europaea, Salicornia perennis, Triglochin maritimum, Plantago maritima, Limonium vulgare, Glaux maritima, Elytrigia atherica, Festuca rubra, Puccinellia maritima, Bostrychia scorpioides, Pelvetia canaliculata

SM26 — Salt marsh

Inula crithmoides stands

Atriplex portulacoides, Suaeda maritima, Inula crithmoides, Spergularia media, Salicornia europaea, Salicornia perennis, Plantago maritima, Armeria maritima, Limonium vulgare, Elytrigia atherica, Festuca rubra, Puccinellia maritima, Spartina anglica, Bostrychia scorpioides

SM28 — Salt marsh

Elymus repens salt-marsh community

Bolboschoenus maritimus, Carex otrubae, Eleocharis uniglumis, Juncus gerardii, Kindbergia praelonga, Odontites verna, Anthriscus sylvestris, Apium graveolens, Heracleum sphondylium, Oenanthe crocata, Oenanthe lachenalii, Torilis japonica, Centaurea nigra, Cirsium arvense, Cirsium vulgare, Scorzoneroides autumnalis, Sonchus arvensis, Tripleurospermum maritimum, Cochlearia anglica, Cochlearia officinalis, Silene uniflora, Stellaria media agg., Atriplex hastata, Atriplex littoralis, Calystegia sepium, Lotus corniculatus, Medicago lupulina, Melilotus altissima, Trifolium repens, Vicia cracca, Triglochin maritimum, Plantago lanceolata, Plantago maritima, Rumex conglomeratus, Rumex crispus, Glaux maritima, Potentilla anserina, Galium aparine, Urtica dioica, Agrostis stolonifera, Alopecurus geniculatus, Arrhenatherum elatius, Dactylis glomerata, Deschampsia cespitosa, Elytrigia repens, Festuca rubra, Holcus lanatus, Lolium perenne, Poa pratensis, Puccinellia maritima, Schedonorus arundinaceus