Description of biotope or habitat type
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Brittlestars on faunal and algal encrusted exposed to moderately wave-exposed circalittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Exposed, Moderately exposed |
| Tidal streams | Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible) |
| Substratum | Bedrock, boulders, cobbles, pebbles, gravel |
| 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 exposed and moderately wave-exposed circalittoral bedrock, boulders and cobbles subject to moderately strong to weak tidal streams. It is characterised by high densities of brittlestars (predominantly Ophiothrix fragilis, Ophiocomina nigra and Ophiura albida). In fact, they may form such dense beds that the seabed underneath may not be visible. The rocky substratum is usually colonised by species such as encrusting red algae and the white, calcareous tubes of the polychaete Spirobranchus triqueter. Only robust hydroids such as Abietinaria abietina, Alcyonium digitatum and bryozoan crusts such as Parasmittina trispinosa are able to tolerate the significant smothering effect from the dense mat of brittlestars. Other species typically seen include Echinus esculentus, Asterias rubens, Pagurus bernhardus, Anapagurus hyndmanni, Steromphala cineraria, Urticina felina, Pododesmus patelliformis and Ciona intestinalis.
Situation
Shallower than the FaAlCr.Bri variant, kelp park and forest may be found with species such as Saccharina latissima and Laminaria hyperborea.
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 | 16 | Abundant | 81-100% |
| Spirobranchus triqueter | 12 | Frequent | 61-80% |
| Echinus esculentus | 10 | Frequent | 81-100% |
| Corallinaceae | 8 | Common | 61-80% |
| Asterias rubens | 7 | Occasional | 81-100% |
| Ophiocomina nigra | 7 | Common | 61-80% |
| Alcyonium digitatum | 6 | Occasional | 81-100% |
| Steromphala cineraria | 3 | Occasional | 41-60% |
| Pagurus bernhardus | 3 | Occasional | 61-80% |
| Urticina felina | 3 | Occasional | 41-60% |
| Abietinaria abietina | 2 | Occasional | 41-60% |
| Ciona intestinalis | 2 | Occasional | 41-60% |
| Ophiura albida | 2 | Frequent | 41-60% |
| Anapagurus hyndmanni | 1 | Frequent | 21-40% |
| Parasmittina trispinosa | 1 | Occasional | 21-40% |
| Pododesmus patelliformis | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
CR.LCR.BrAs.AmenCio.Bri
This biotope occurs on more wave-sheltered mixed substratum, subject to moderately strong to very weak tidal streams. It tends to have a similar species diversity to CR.MCR.EcCr.FaAlCr.Bri, but robust hydroids such as A. abietina have been replaced by more delicate species such as IR.LIR.Kirchenpaueria pinnata. Occasionally, bryozoan crusts may be present in CR.MCR.EcCr.FaAlCr.Bri as well.
CR.MCR.EcCr.CarSp.Bri
This biotope is found on much more exposed bedrock or boulders. A diverse range of species is associated with this biotope including numerous hydroids, bryozoans and echinoderms.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1997 (97.06) | CR.MCR.Bri.Oph |
| 1997 (97.06) | CR.MCR.Bri.Oph.Oacu |
