Description of biotope or habitat type
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Caryophyllia smithii, Swiftia pallida and large solitary ascidians on exposed or moderately exposed circalittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Extremely exposed, Very exposed, Exposed, Moderately exposed, Sheltered |
| Tidal streams | Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible) |
| Substratum | Bedrock; boulder |
| 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 typically occurs on exposed to moderately wave-exposed, circalittoral bedrock and boulders rock subject to mainly weak tidal streams and has a thin layer of silt present. It is found predominantly from 10-30m water depth. From afar, this biotope is mostly distinguished by the frequently occurring seafan Swiftia pallida, encrusting red algae and the abundant cup coral Caryophyllia smithii. This biotope has quite an impoverished appearance, compared with SwiLgAs which has a strong sponge component. Other species present are typically in low abundance. Echinoderms such as Echinus esculentus, Antedon bifida, Antedon petasus, Leptometra celtica, Marthasterias glacialis, Luidia ciliaris and Asterias rubens may be recorded. Large hydroids such as Nemertesia antennina and Nemertesia ramosa may occasionally be seen in isolated clumps on the tops of boulders and rocky outcrops. The anthozoan Parazoanthus anguicomus may be recorded. Bryozoans such as Parasmittina trispinosa and Porella compressa are occasionally observed. The polychaete Spirobranchus triqueter may be observed encrusting the sides of rocks and boulders while occasional Alcyonium digitatum may also be seen. A small suite of large ascidians may be present, including Ascidia mentula, Clavelina lepadiformis, Ciona intestinalis, Diazona violacea and Ascidia virginea. Sponges are typically absent from this biotope, although Cliona celata may be recorded occasionally. The top shell Steromphala cineraria is usually present. Under boulders and overhangs, the squat lobster Munida rugosa can usually be seen hiding. All these records are from the west coast of Scotland (East coast of Lewis /Outer Hebrides).
Situation
Above this biotope in the infralittoral zone, sheltered kelp forests are usually found, with species such as Laminaria hyperborea, Saccharina latissima and Sacchoriza polyschides. This biotope is found on bedrock and boulders, which may either be protruding from the surrounding sediment, or the sediment may be in a separate zone below the bedrock. These sediments may either be deep mud (with species such as Pachycerianthus and Nephrops ) on the sheltered sites or slightly coarser sediments (with Pennatula and Virgularia) on slightly more exposed sites.
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 |
|---|---|---|---|
| Caryophyllia smithii | 22 | Abundant | 81-100% |
| Swiftia pallida | 12 | Frequent | 81-100% |
| Corallinaceae | 7 | Abundant | 41-60% |
| Echinus esculentus | 6 | Frequent | 61-80% |
| Parasmittina trispinosa | 5 | Occasional | 61-80% |
| Ascidia mentula | 4 | Occasional | 61-80% |
| Munida rugosa | 4 | Occasional | 61-80% |
| Nemertesia antennina | 4 | Occasional | 61-80% |
| Antedon bifida | 3 | Occasional | 41-60% |
| Antedon petasus | 3 | Frequent | 41-60% |
| Marthasterias glacialis | 2 | Occasional | 41-60% |
| Nemertesia ramosa | 2 | Occasional | 41-60% |
| Spirobranchus triqueter | 2 | Occasional | 41-60% |
| Alcyonium digitatum | 1 | Occasional | 41-60% |
| Ascidia virginea | 1 | Occasional | 41-60% |
| Asterias rubens | 1 | Occasional | 41-60% |
| Ciona intestinalis | 1 | Occasional | 41-60% |
| Clavelina lepadiformis | 1 | Occasional | 41-60% |
| Cliona celata | 1 | Occasional | 41-60% |
| Diazona violacea | 1 | Occasional | 41-60% |
| Steromphala cineraria | 1 | Occasional | 21-40% |
| Luidia ciliaris | 1 | Rare | 41-60% |
| Porella compressa | 1 | Rare | 41-60% |
Similar biotopes or habitat types
CR.HCR.XFa.SwiLgAs
This biotope occurs in slightly more tide-swept sites than CR.MCR.EcCr.CarSwi.LgAs. They both occur across similar depth bands. CR.HCR.XFa.SwiLgAs appears a lot more biologically diverse, with a greater range of sponges, hydroids, bryozoans and ascidians, although this difference may possibly be due to poor data.
CR.MCR.EcCr.CarSwi.Aglo
This biotope predominantly occurs in the sheltered end of the wave-exposure spectrum, subject to only weak tidal streams. It is typically found across similar depth bands as CR.MCR.EcCr.CarSwi.LgAs. This heavily silted biotope is characterised by Swiftia pallida, Alcyonium glomeratum, Isozoanthus sulcatus and the prominent Holothuria (Panningothuria) forskali. This biotope is only present around the coast of Ireland.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1997 (97.06) | CR.MCR.XFa.ErSSwi |
