Description of biotope or habitat type
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Brittlestars overlying coralline crusts, Parasmittina trispinosa and Caryophyllia smithii on wave-exposed 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), Weak (>1 kn) |
| Substratum | Bedrock, boulders |
| Zone | Circalittoral |
| Depth Band | 10-20 m, 20-30 m, 30-50 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 variant is typically found on the upper faces of wave-exposed circalittoral bedrock or boulders subject to moderately strong to weak tidal streams, on open coasts. However, the depth at which the variant occurs means that wave action is not so severe on the seabed as to displace the dense mat of brittlestars that covers the seabed. Ophiothrix fragilis is usually the most dominant species in shallow water, with Ophiocomina nigra usually found amongst them, but sometimes becoming the dominant species in deeper water. Although brittlestar biotopes are typically species-poor, the underlying fauna in this variant is relatively diverse and resembles that of CarSp.PenPcom. Species such as the anemone Urticina felina, the cup coral Caryophyllia smithii, and the anemone Corynactis viridis may occasionally be present. There may also be sparse clumps of various hydroids including Halecium halecinum, Nemertesia antennina, Nemertesia ramosa, Sertularella gayi and Abietinaria abietina. Soft coral Alcyonium digitatum is occasionally present and there may be sparse specimens of the sponges Cliona celata and Polymastia boletiformis. In addition, various echinoderms such as Asterias rubens, Antedon bifida, Echinus esculentus, Henricia oculata, Marthasterias glacialis and Luidia ciliaris may be observed. The barnacle Balanus crenatus and the polychaete Spirobranchus triqueter may be seen attached to any available space on the bedrock and boulders not smothered by brittlestars. Bryozoan crusts such as Parasmittina trispinosa may also be present.
Situation
Wave-exposed seabed composed of bedrock ridges and/or boulder or cobble slope. Shallower than this biotope, the lower infralittoral kelp park is dominated by Laminaria hyperborea. A dense understorey may be present, containing Antedon spp., Phycodrys rubens and Plocamium cartilagineum.
Temporal variation
Not known.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Ophiothrix fragilis | 14 | Abundant | 81-100% |
| Ophiocomina nigra | 12 | Common | 81-100% |
| Asterias rubens | 7 | Occasional | 81-100% |
| Alcyonium digitatum | 5 | Occasional | 81-100% |
| Antedon bifida | 4 | Occasional | 61-80% |
| Calliostoma zizyphinum | 4 | Occasional | 81-100% |
| Henricia oculata | 4 | Occasional | 81-100% |
| Urticina felina | 4 | Frequent | 81-100% |
| Echinus esculentus | 4 | Occasional | 61-80% |
| Caryophyllia smithii | 3 | Occasional | 61-80% |
| Halecium halecinum | 3 | Occasional | 61-80% |
| Marthasterias glacialis | 3 | Occasional | 61-80% |
| Corallinaceae | 2 | Frequent | 41-60% |
| Cliona celata | 2 | Occasional | 61-80% |
| Corynactis viridis | 2 | Frequent | 41-60% |
| Nemertesia antennina | 2 | Occasional | 41-60% |
| Parasmittina trispinosa | 2 | Frequent | 41-60% |
| Abietinaria abietina | 1 | Occasional | 41-60% |
| Balanus crenatus | 1 | Frequent | 21-40% |
| Luidia ciliaris | 1 | Occasional | 41-60% |
| Nemertesia ramosa | 1 | Occasional | 41-60% |
| Polymastia boletiformis | 1 | Occasional | 41-60% |
| Spirobranchus triqueter | 1 | Occasional | 41-60% |
| Sertularella gayi | 1 | Occasional | 41-60% |
Similar biotopes or habitat types
CR.MCR.EcCr.FaAlCr.Bri
This biotope is found on slightly more wave-sheltered coasts, but subject to similar moderately strong to weak tidal streams. LR.LLR.FaAlc.Bri also tends to be fond on a more heterogeneous seabed, whereas CR.MCR.EcCr.CarSp.Bri is typically found on bedrock or boulders. Although they are both brittlestar biotopes, unlike CR.MCR.EcCr.CarSp.Bri, LR.LLR.FaAlc.Bri is devoid of any sponges, and is characterised by graze-resistant hydroids.