Description of biotope or habitat type
Alcyonium digitatum and faunal crust communities on vertical circalittoral bedrock
Habitat (physical) description
|Salinity||Full (30-35 ppt)|
|Wave exposure||Extremely exposed, Very exposed, Exposed, Moderately exposed|
|Tidal streams||Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)|
|Zone||Infralittoral - lower, Circalittoral|
|Depth Band||5-10 m, 10-20 m, 20-30 m, 30-50 m|
|Other Features||Vertical rock|
Download comparative physical and biological data. The comparative tables enable a rapid comparison of the species composition and principal physical characteristics between a given set of biotopes.
- Records used to define the biotope (core records)
- Other records assigned to this biotope, marked as 'certain'
- Other records assigned to this biotope, marked as 'uncertain'
- Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat
This biotope typically occurs on the vertical faces and overhangs of exposed to moderately exposed lower infralittoral and upper circalittoral bedrock subject to moderately strong to weak tidal streams. Due to the large numbers of the urchin Echinus esculentus often recorded, this biotope tends to have a grazed appearance, and the bedrock is often encrusted with pink coralline algae, encrusting bryozoans such as Parasmittina trispinosa and the calcareous tubeworm Pomatoceros triqueter. Dense aggregations of dead mans fingers Alcyonium digitatum may be present along with the cup coral Caryophyllia smithii. Other species present include the echinoderms Asterias rubens, Ophiothrix fragilis and Antedon bifida, the ascidians Clavelina lepadiformis, Ciona intestinalis and Ascidia mentula, the anthozoans Urticina feline, Cortynactis viridis, Metridium senile and Sagartia elegans, the gastropod Calliostoma zizyphinum and the crustacean Cancer pagurus. Three regional variations of this biotope have been recorded. One variant found typically off the north-east coast of Scotland and around the Northern Isles, has a very impoverished appearance dominated by anthozoans. A second variant occurs along the west coast of Scotland, extending to Rockall in the west, and the Northern Isles in the north-east, and has a more fauna, characterised by hydroids, sponges, anthozoans and echinoderms. A third variant occurs along the north-east coast of England (Northumberland) up to the Northern Isles and is dominated by Alcyonium digitatum, brittlestars and Echinus esculentus.
No situation data available.
No temporal variation data available.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Alcyonium digitatum||13||Common||61-80 %|
|Urticina felina||2||Occasional||41-60 %|
|Metridium senile||2||Occasional||21-40 %|
|Sagartia elegans||1||Occasional||21-40 %|
|Corynactis viridis||2||Common||21-40 %|
|Caryophyllia smithii||4||Frequent||41-60 %|
|Pomatoceros triqueter||8||Common||61-80 %|
|Cancer pagurus||2||Occasional||41-60 %|
|Calliostoma zizyphinum||3||Occasional||41-60 %|
|Parasmittina trispinosa||2||Occasional||21-40 %|
|Antedon bifida||6||Frequent||41-60 %|
|Asterias rubens||8||Occasional||61-80 %|
|Ophiothrix fragilis||2||Occasional||21-40 %|
|Echinus esculentus||9||Frequent||61-80 %|
|Clavelina lepadiformis||4||Occasional||41-60 %|
|Ciona intestinalis||2||Occasional||21-40 %|
|Ascidia mentula||2||Occasional||21-40 %|
Not applicable or unknown.