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Marine Habitat Classification

Description of biotope or habitat type

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   Alcyonium digitatum and faunal crust communities on vertical circalittoral bedrock

Physical habitat 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)
Substratum Bedrock
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.

Distribution of habitat CR.MCR.EcCr.AdigVt <I>Alcyonium digitatum</I> and faunal crust communities on vertical circalittoral bedrock

  • 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

Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.


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 Spirobranchus 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 Cylista 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.

Temporal variation

No temporal variation data available.

Characterising species

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%
Corallinaceae 10 Common 61-80%
Echinus esculentus 9 Frequent 61-80%
Asterias rubens 8 Occasional 61-80%
Spirobranchus triqueter 8 Common 61-80%
Antedon bifida 6 Frequent 41-60%
Caryophyllia smithii 4 Frequent 41-60%
Clavelina lepadiformis 4 Occasional 41-60%
Calliostoma zizyphinum 3 Occasional 41-60%
Ascidia mentula 2 Occasional 21-40%
Cancer pagurus 2 Occasional 41-60%
Ciona intestinalis 2 Occasional 21-40%
Corynactis viridis 2 Common 21-40%
Metridium senile 2 Occasional 21-40%
Ophiothrix fragilis 2 Occasional 21-40%
Parasmittina trispinosa 2 Occasional 21-40%
Urticina felina 2 Occasional 41-60%
Cylista elegans 1 Occasional 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

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