Description of biotope or habitat type
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Bryozoan turf and erect sponges on tide-swept circalittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Extremely exposed, Very exposed, Exposed, Moderately exposed |
| Tidal streams | Strong (3-6 kn), Moderately strong (1-3 kn) |
| Substratum | Bedrock; boulder |
| Zone | Circalittoral - lower, Circalittoral - upper |
| Depth Band | 10-20 m, 20-30 m |
| Other Features |
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 is typically found on wave-exposed circalittoral bedrock or boulders subject to tidal streams ranging from moderately strong to strong. It often has a thin layer of silt covering the seabed, and is characterised by a bryozoan/hydroid turf with erect sponges. Typical bryozoans to be found include crisiids, Alcyonidium diaphanum, Flustra foliacea, Pentapora foliacea, Crisularia plumosa and Bugulina flabellata, while typical hydroids include Nemertesia antennina, Nemertesia ramosa and Halecium halecinum. The soft coral Alcyonium digitatum is frequently recorded on the tops of boulders and rocky outcrops. Characteristic erect sponges include Raspailia ramosa, Stelligera stuposa and Stelligera montagui; other sponges present include Cliona celata, Dysidea fragilis, Pachymatisma johnstonia, Polymastia boletiformis, Hemimycale columella, Amphilectus fucorum, Polymastia mamillaris and Tethya aurantium. Other species present include Caryophylia smithii, Actinothoe sphyrodeta, Corynactis viridis, Urticina felina, Balanus crenatus, Asterias rubens, Marthasterias glacialis, Henricia oculata, Echinus esculentus, Clavelina lepadiformis, Calliostoma zizyphinum and Necora puber. Three variants of this biotope have been described, but all are characterised by a bryozoan turf with erect sponges. ByErSp.Eun is found primarily on circalittoral bedrock and is dominated by the seafan Eunicella verrucosa. ByErSp.DysAct is found under slightly stronger tide-swept conditions, and is characterised particularly by the sponge D. fragilis and the anemone A. sphyrodeta. Finally ByErSp.Sag is characterised by the anemone Cylista elegans.
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 | 5 | Frequent | 81-100% |
| Caryophyllia smithii | 4 | Frequent | 61-80% |
| Cliona celata | 4 | Occasional | 81-100% |
| Nemertesia antennina | 4 | Frequent | 81-100% |
| Alcyonidium diaphanum | 3 | Frequent | 61-80% |
| Asterias rubens | 3 | Frequent | 61-80% |
| Dysidea fragilis | 3 | Frequent | 61-80% |
| Actinothoe sphyrodeta | 2 | Occasional | 61-80% |
| Balanus crenatus | 2 | Occasional | 21-40% |
| Crisularia plumosa | 2 | Frequent | 41-60% |
| Calliostoma zizyphinum | 2 | Occasional | 41-60% |
| Clavelina lepadiformis | 2 | Occasional | 61-80% |
| Corynactis viridis | 2 | Frequent | 41-60% |
| Amphilectus fucorum | 2 | Frequent | 41-60% |
| Flustra foliacea | 2 | Frequent | 41-60% |
| Hemimycale columella | 2 | Occasional | 61-80% |
| Nemertesia ramosa | 2 | Occasional | 61-80% |
| Pachymatisma johnstonia | 2 | Occasional | 61-80% |
| Polymastia boletiformis | 2 | Frequent | 61-80% |
| Raspailia ramosa | 2 | Occasional | 61-80% |
| Stelligera stuposa | 2 | Occasional | 41-60% |
| Echinus esculentus | 2 | Occasional | 61-80% |
| Bugulina flabellata | 1 | Occasional | 41-60% |
| Crisiidae | 1 | Frequent | 41-60% |
| Halecium halecinum | 1 | Frequent | 41-60% |
| Henricia oculata | 1 | Occasional | 41-60% |
| Marthasterias glacialis | 1 | Occasional | 41-60% |
| Necora puber | 1 | Occasional | 41-60% |
| Pentapora foliacea | 1 | Occasional | 41-60% |
| Polymastia mamillaris | 1 | Occasional | 41-60% |
| Stelligera montagui | 1 | Occasional | 41-60% |
| Tethya aurantium | 1 | Occasional | 41-60% |
| Urticina felina | 1 | Occasional | 41-60% |
Similar biotopes or habitat types
Not applicable or unknown.
