Description of biotope or habitat type
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Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Exposed, Moderately exposed, Sheltered |
| Tidal streams | Moderately strong (1-3 kn), Weak (>1 kn) |
| Substratum | Bedrock, boulder |
| Zone | Circalittoral - lower, Circalittoral - upper |
| 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 biotope typically occurs from exposed through to sheltered circalittoral bedrock or boulders subject to moderately strong to weak tidal streams. It is found in water depths ranging from 4m to 37m. This biotope is distinguished by frequently occurring Swiftia pallida, abundant Caryophilia smithii and a diverse range of ascidians including Clavelina lepadiformis, Ascidia mentula, Polycarpa pomaria, Diazona violacea and Corella parallelogramma. A sparse, yet diverse hydroid turf is often apparent, with species such as Aglaophenia tubulifera, Nemertesia antennina, Schizotricha frutescens, Halecium halecinum, Abietinaria abietina, Nemertesia ramosa and Halopteris catharina often recorded. Spaces amongst the turf are usually colonised by the polychaete Spirobranchus triqueter and encrusting red algae. Crinoids such as Antedon petasus, Antedon bifida and Leptometra celtica may be seen filter feeding on the tops of outcrops and boulders, along with the soft coral Alcyonium digitatum. Other echinoderms such as Echinus esculentus, Crossaster papposus and Asterias rubens may also be recorded. There may also be a bryozoan component to the sparse faunal turf. Species such as Securiflustra securifrons and Eucratea loricata as well as the crustose Parasmittina trispinosa are all usually present. There may be a few isolated growths of sponge, such as Iophon nigricans, Axinella infundibuliformis and Haliclona urceolus. Other species that may be present include the brachiopod Terebratulina retusa and the top shell Calliostoma zizyphinum. The crustacean Munida rugosa may be visible in crevices. All records are from the west coast of Scotland (east coast of Lewis /Outer Hebrides).
Situation
Above this biotope, kelp forests and parks are typically found in the infralittoral, with Saccharina latissima and Laminaria hyperborea. This biotope is found in Scottish Sealochs and, in the most sheltered situations, may graduate into NeoPro at greater depths.
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 | 7 | Frequent | 81-100% |
| Swiftia pallida | 6 | Frequent | 81-100% |
| Aglaophenia tubulifera | 4 | Frequent | 61-80% |
| Ascidia mentula | 4 | Frequent | 61-80% |
| Clavelina lepadiformis | 4 | Occasional | 81-100% |
| Antedon bifida | 3 | Frequent | 61-80% |
| Nemertesia antennina | 3 | Occasional | 61-80% |
| Spirobranchus triqueter | 3 | Frequent | 61-80% |
| Echinus esculentus | 3 | Occasional | 61-80% |
| Abietinaria abietina | 2 | Frequent | 41-60% |
| Alcyonium digitatum | 2 | Occasional | 61-80% |
| Antedon petasus | 2 | Frequent | 41-60% |
| Axinella infundibuliformis | 2 | Occasional | 61-80% |
| Corella parallelogramma | 2 | Occasional | 61-80% |
| Diazona violacea | 2 | Occasional | 61-80% |
| Halecium halecinum | 2 | Occasional | 61-80% |
| Iophon nigricans | 2 | Occasional | 61-80% |
| Munida rugosa | 2 | Occasional | 61-80% |
| Parasmittina trispinosa | 2 | Occasional | 61-80% |
| Polycarpa pomaria | 2 | Occasional | 61-80% |
| Schizotricha frutescens | 2 | Occasional | 61-80% |
| Securiflustra securifrons | 2 | Frequent | 61-80% |
| Corallinaceae | 1 | Frequent | 41-60% |
| Asterias rubens | 1 | Occasional | 41-60% |
| Calliostoma zizyphinum | 1 | Occasional | 41-60% |
| Crossaster papposus | 1 | Rare | 61-80% |
| Eucratea loricata | 1 | Frequent | 41-60% |
| Haliclona oculata | 1 | Occasional | 41-60% |
| Halopteris catharina | 1 | Frequent | 41-60% |
| Leptometra celtica | 1 | Occasional | 41-60% |
| Nemertesia ramosa | 1 | Occasional | 41-60% |
| Terebratulina retusa | 1 | Occasional | 41-60% |
Similar biotopes or habitat types
CR.MCR.EcCr.CarSwi.LgAs
This biotope is found over a broad range of sites with different wave-exposures, subject to moderately strong to very weak tidal streams. Substratum is typically similar to CR.HCR.XFa.SwiLgAs. This biotope is more impoverished than CR.HCR.XFa.SwiLgAs, lacking the diverse range of sponges, hydroids and bryozoans but still with frequent S. pallida.
CR.MCR.EcCr.CarSwi.Aglo
This biotope occurs predominantly in the sheltered end of the wave-exposure spectrum, and is subject to only weak tidal streams. It is typically found across similar depth bands as CR.HCR.XFa.SwiLgAs. This heavily silted biotope is characterised by S. pallida, Alcyonium glomeratum, Isozoanthus sulcatus and the prominent Holothuria (Panningothuria) forskali, the latter two of which are absent from CR.HCR.XFa.SwiLgAs. 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 |
Photos
