Portmuck
Also within
Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
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
Geology & landscape
Geological Feature: Igneous Intrusion, Rock Outcrop · Geological Period: Cretaceous, Jurassic · Rock Type: Basalt, Chalk, Flint, Limestone, Mudstone, Sandstone, Siltstone
Landscape processes: Coastal, Volcanic / Igneous
Birds & fish recorded
Birds
| Species | Season |
|---|---|
| fulmar | Breeding |
| guillemot | Breeding |
| kittiwake | Breeding |
| puffin | Breeding |
| razorbill | Breeding |
| razorbill | Unknown |
Description
Portmuck Razorbill Coastal processes, Cretaceous stratigraphy, Tertiary igneous, Mineralogy The coastal section from McIlroy's Port to Isle of Muck exhibits a range of notable geological and geomorphological features. These include, from oldest to youngest, the Mesozoic sediments west of Portmuck harbour, the volcanic vent and associated minerals at McIlroy's Port, the unusual minerals which occur near Isle of Muck and the gravel barrier or tombolo between Isle of Muck and the mainland. The cliffs also support a range of plant species typical of such habitat together with some saltmarsh. The cliffs at the Isle of Muck are the site of a small seabird colony. At Portmuck, Mesozoic strata from the Lias Waterloo Mudstone Formation to the Cretaceous Glenarrn Chalk Member are well exposed in a series of coastal cliffs. The fossiliferous Lower Lias Waterloo Mudstone Formation is exposed as a foreshore outcrop of soft blue clay and limestone. The thin shelly limestone forms a foreshore reef. These are Jurassic in age, some 200 million years old. The Hibernian Greensands Formation is well exposed in the cliffs to the west of Portmuck Harbour and includes sandstone and marl of the Kilcoan Sands, Island Magee Siltstone and Belfast Marls Members. These are the best exposures of the Hibernian Greensands Formation in Northern Ireland and form the oldest Cretaceous sediments present here, dating from some 97 million years ago. The Hibernian Greensands Formation is overlain by the slightly younger Cloghfin Sponge Beds Member. This series is approximately lm thick and is a glauconitic chalk rich in fossil sponges; it contains fragments of Inoceramus shells, a bivalve common in these Cretaceous seas. This in turn is overlain by a sequence of the Ulster White Limestone Formation, 32 m. thick but often much affected by slippage and faulting. McIlroy's Port to the north of Portmuck exhibits an explosive volcanic vent sited in a composite flow. These features date from the Tertiary period, some 60 million years old. This site contains the only known occurrence of the mineral sodalite in Ireland. The lava flow, which is divided into a composite flow, is the best example of this feature in the Antrim basalts. The upper component is some 15 m. thick while the lower basalt is about 3 m thick. The lower zone of the flow is particularly rich in olivine, a mineral which solidifies early in molten basaltic lava, and here has settled due to gravity. Within this lower zone, there are numerous patches and veins of a range of minerals including the sodalite. South ofMcIlroy's Port a conspicuous dolerite dyke intrudes the older chalk and the overlying basalt. The development of a wide range of minerals in the metamorphosed, mineral-filled hollows or amygdales of the adjacent basalts has been noted. The White Limestone is disturbed and baked close to the dyke. The basalt flows just west of this dyke are thin pahoehoe units which exhibit ropey lava surfaces, evidence of a more viscous lava type. A further dolerite dyke, opposite the Isle of Muck, has resulted in the chalk here being replaced by the minerals chalcedony, magnetite and garnet. At the southern end of the site, faulting brings the Lower Basalts to sea-level as a cliffline. Contained in the basalts are a range of secondary minerals known as zeolites. These formed within cavities in the basalt as warm water circulated within the igneous rocks soon after they solidified. The warm water dissolved a range of minerals which solidified as zeolites as the water cooled. Among these is a type first identified from this area and named Gobbinsite; a range of other zeolites are also present. South of Portmuck a gravel barrier, or tombolo, links the Isle of Muck and the mainland. This tombolo is the only such feature on the open sea coast of Northern Ireland. The gravel barrier, composed of rounded gravel and boulders of chalk, flint and basalt, appears to resemble a classic tombolo but it is possible that it did not form in the normal manner for such features. Rather, evidence points to it having originated through southward movement and eventual stranding of a gravel barrier in shallow water. As there is no evidence of fresh gravel input from the adjacent coastline, it is likely that the tombolo is in an advanced stage of development in which a fixed volume of sediment is redistributed within the structure. Evidence of former higher sea-levels can be seen at a number of places within the area. Portmuck exhibits a number of stranded clifflines, notably opposite the Isle of Muck while abandoned sea caves, arches and raised beaches are present to the north of McIlroy's Port. A range of plant communities are associated within the site. Although the cliffs within the site are composed of a variety of rock types, the distribution of these communities depends more on the nature and stability of the cliff section. While the composition of communities may vary in detail, there are a number of species which occur commonly throughout the site in most situations. These include red fescue Festuca rubra, sea mayweed Tripleurospermum maritima, sea plantain Plantago maritima, common scurvey grass Cochlearia officinalis and thrift Armeria maritima. Cliff sections which experience slippage, and so have a disturbed soil, support rank red fescue Festuca rubra, common ragwort Jacobaea vulgaris, common nettle Urtica dioica, perennial sow thistle Sonchus arvensis and hogweed Heracleum sphondylium. Stable, near-vertical rock faces, generally have either high ivy Hedera helix cover or, on less steep faces, sea campion Silene uniflora. Where soil is very thin or almost non-existent on these slopes the grass component is reduced allowing a greater diversity of associated species including harebell Campanula rotundifolia, common knapweed Centaurea nigra, kidney vetch Anthyllis vulneraria, yarrow Achillea millefolium, birdsfoot trefoil Lotus corniculatus, lady's bedstraw Galium verum, wild carrot Daucus carota and sea campion Silene uniflora. These tend to be the most species rich areas within the site. Isle of Muck supports a notable population of breeding seabirds. The most numerous group are the auks with razorbill Alca torda and guillemot Uria aalgae present together with small numbers of puffin Fratercula arctica. Kittiwake Rissa tridactyla and fulmar Fulmarus glacialis are also present together with black guillemot Cepphus grylle which utilises a series of small caves and crevices for nesting. https://www.daera-ni.gov.uk/publications/portmuck-assi
Species mentioned
Show the 23 species mentioned in the description, with red-list status| English name search for this in other sites |
Latin name search with Google |
IUCN / Red List | Type | Family |
|---|---|---|---|---|
| razorbill | Alca torda | LC (Breeding) | bird-auk | alcidae |
| black guillemot | Cepphus grylle | NT (Breeding) | bird-auk | alcidae |
| puffin | Fratercula arctica | CR (Breeding) | bird-auk | alcidae |
| guillemot | Uria aalge | LC (Breeding) | bird-auk | alcidae |
| fulmar | Fulmarus glacialis | CR (Breeding) | bird-fulmar | procellariidae |
| kittiwake | Rissa tridactyla | EN (Breeding) | bird-gull | laridae |
| red fescue | Festuca rubra | LC | grass | poaceae |
| yarrow | Achillea millefolium | LC | herb | asteraceae |
| lady's fingers (kidney vetch) | Anthyllis vulneraria | NT | herb | fabaceae |
| thrift | Armeria maritima | CR | herb | plumbaginaceae |
| harebell | Campanula rotundifolia | LC | herb | campanulaceae |
| black knapweed | Centaurea nigra | LC | herb | asteraceae |
| scurvy grass | Cochlearia officinalis | LC | herb | brassicaceae |
| wild carrot | Daucus carota | LC | herb | apiaceae |
| lady's bedstraw | Galium verum | LC | herb | rubiaceae |
| hogweed | Heracleum sphondylium | CR(PE) | herb | apiaceae |
| ragwort | Jacobaea vulgaris | LC | herb | asteraceae |
| birdsfoot trefoil | Lotus corniculatus | LC | herb | fabaceae |
| sea plantain | Plantago maritima | LC | herb | plantaginaceae |
| sea campion | Silene uniflora | LC | herb | carophyllaceae |
| perennial sow- thistle | Sonchus arvensis | LC | herb | asteraceae |
| nettle | Urtica dioica | LC | herb | urticaceae |
| ivy | Hedera helix | LC | woody climber | araliaceae |
Plant communities
SM1 — Salt marsh
Zostera communities
Show 15 indicator speciesZostera 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
SM3 — Salt marsh
Eleocharis parvula salt-marsh community
Show 1 indicator speciesEleocharis parvula
SM4 — Salt marsh
Spartina maritima salt-marsh community
Show 6 indicator speciesSuaeda maritima, Salicornia europaea, Salicornia perennis, Puccinellia maritima, Spartina anglica, Spartina maritima
SM5 — Salt marsh
Spartina alterniflora salt-marsh community
Show 3 indicator speciesPuccinellia maritima, Spartina alterniflora, Spartina anglica
SM6 — Salt marsh
Spartina anglica salt-marsh community
Show 14 indicator speciesAtriplex 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
Show 9 indicator speciesAtriplex 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
Show 6 indicator speciesAtriplex portulacoides, Suaeda maritima, Aster tripolium, Salicornia europaea, Puccinellia maritima, Spartina anglica
SM9 — Salt marsh
Suaeda maritima salt-marsh community
Show 6 indicator speciesAtriplex 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
Show 10 indicator speciesAtriplex 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
Show 12 indicator speciesAtriplex 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
Show 13 indicator speciesSchoenoplectus 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
Show 23 indicator speciesAtriplex 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
Show 16 indicator speciesAtriplex 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
Show 24 indicator speciesAtriplex 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
Show 30 indicator speciesAtriplex 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
Show 24 indicator speciesAtriplex 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
Show 32 indicator speciesCarex 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
Show 26 indicator speciesBlysmus 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
Show 25 indicator speciesBolboschoenus 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
Show 21 indicator speciesAtriplex 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
Show 14 indicator speciesAtriplex 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
Show 18 indicator speciesAtriplex 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
Show 24 indicator speciesAtriplex 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
Show 20 indicator speciesAtriplex 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
Show 14 indicator speciesAtriplex 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
Show 51 indicator speciesBolboschoenus 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