Rathlin Island

General site character

• Marine areas, Sea inlets (93%)
  
• Shingle, Sea cliffs, Islets (7%)
  

Annex I habitats that are a primary reason for selection of this site

• 1170 Reefs

  Rathlin Island is surrounded by a wide range of rocky habitats and is one of the best examples of reefs in Northern Ireland. Strong tidal streams prevail around most of the island, and there is little silt. As a result, turbidity is generally low, with the infralittoral extending below 20 m depth, and water temperatures are stable, not rising much above 13ºC in the summer. A very wide range of species has been recorded around the island, including a high proportion of species of particular interest. Along the south-west coast there is a very steep slope of large, stable boulders extending below 50 m in places. The boulders support biotopes dominated by Tubularia indivisa in deeper water and by a diverse assemblage of algae in the shallows. A number of species occur that are rare in Northern Ireland, especially those with south-western distributions, such as the sea-cucumber Holothuria forskali, the sponge Axinella damicornis, and the red alga Drachiella spectabilis. The north-west part of Rathlin Island consists of a shallow shelf 10-100 m wide along the base of the cliffs, followed by a vertical underwater cliff which starts at 20-30 m and descends to over 100 m. The cliffs are formed of both limestone and basalt, and support a rich assemblage of sponges and hydroids. Dominant species include Pachymatisma johnstonia, the soft coral Alcyonium digitatum, Dendrodoa grossularia and T. indivisa. To the north-east, the slope offshore is shallower, with the seabed consisting of areas of bedrock interspersed with stable boulder slopes. Sponges are particularly diverse and abundant. In shallow water there are overhangs and surge gullies with characteristic assemblages of species. The circalittoral zone of the east coast is mostly dominated by rich hydroid and sponge-dominated biotopes on bedrock, boulders, and cobbles, amongst coarse gravel. Frequent components of these biotopes are the hydroids Polyplumaria flabellata, Diphasia alata and the sponge Axinella infundibuliformis.

• 1230 Vegetated sea cliffs of the Atlantic and Baltic Coasts

  Rathlin Island represents an extensive area of hard cliff along the exposed northern coastline of Northern Ireland. The site exhibits contrasting geology, with Cretaceous chalk overlain by Tertiary basalts. The site consists of very high vertical sea cliffs and sea stacks to the north and east, with more gentle slopes on the eastern coast. As a result of these variations in height and slope, in addition to the diversity of aspects, exposure and rock type, a wide range of maritime cliff vegetation communities is present. Red fescue Festuca rubra is often the dominant species in the grassland communities, while heath is also present in some places. Some species recorded for the site are scarce in Northern Ireland, including common juniper Juniperus communis, Scots lovage Ligusticum scoticum and roseroot Sedum rosea.

• 8330 Submerged or partially submerged sea caves

  Rathlin, situated off the north coast of Northern Ireland, includes well-developed examples of both partially submerged and submerged caves and overhangs in limestone and basalt in a strong tidal stream. Submerged caves occur mainly at depths ranging from 20 to over 100 m. The site has a rich assemblage of sponges and hydroids. Species found include sponges such as Stryphnus ponderosus and Dercitus bucklandi, and the anemones Sagartia elegans, Parazoanthus axinellae and P. anguicomus, which are frequent. The site is used by cave-breeding 1364 Grey seal Halichoerus grypus.

Annex I habitats present as a qualifying feature, but not a primary reason for selection of this site

• 1110 Sandbanks which are slightly covered by sea water all the time
• 1210 Annual vegetation of drift lines

Annex II species that are a primary reason for selection of this site

• Not Applicable

Annex II species present as a qualifying feature, but not a primary reason for site selection

• Not Applicable