Description of biotope or habitat type
To understand more about what this page is describing, see How to use the classification. See also How to cite.
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.
- 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.
Description
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.
Situation
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.