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Marine Habitat Classification

Description of biotope or habitat type

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   Caryophyllia smithii, Swiftia pallida and Alcyonium glomeratum on wave-sheltered circalittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
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.

Distribution of habitat CR.MCR.EcCr.CarSwi.Aglo <I>Caryophyllia smithii</I>, <I>Swiftia pallida</I> and <I>Alcyonium glomeratum</I> on wave-sheltered circalittoral rock

  • 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.


This variant typically occurs on sheltered, ridged, circalittoral bedrock or boulders subject to only weak tidal streams, but may be found in somewhat more exposed conditions. It is found in water depths ranging from 15m to 32m. Commonly occurring Swiftia pallida characterises this heavily silted biotope along with Caryophyllia smithii and frequent Alcyonium glomeratum. Under the silt, bryozoan crusts such as Parasmittina trispinosa may be found. There is a strong echinoderm component to the community, with the tentacles of Aslia lefevrei frequently seen protruding from crevices in the ridged bedrock. Holothuria (Panningothuria) forskali is often seen on the upper faces of boulders and bedrock. Marthasterias glacialis, Asterias rubens, Echinus esculentus, Henricia oculata and Luidia ciliaris may also be present. A sparse hydroid turf may also be present, with species such as Schizotricha frutescens, Halecium halecinum and Nemertesia antennina. In addition, there may be anthozoans such as Isozoanthus sulcatus and Corynactis viridis. The sponge Suberites carnosus is typically associated with a heavily silted habitat. Other sponges present include Cliona celata, Stelligera stuposa and Polymastia boletiformis. The only records are from the west coast of Ireland.


Usually found on bedrock ridges and outcrops surrounded by sand and muddy gravel.

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 12 Common 81-100%
Swiftia pallida 11 Common 81-100%
Aslia lefevrei 8 Frequent 81-100%
Suberites carnosus 8 Occasional 81-100%
Cliona celata 6 Occasional 81-100%
Holothuria (Panningothuria) forskali 6 Occasional 81-100%
Alcyonium glomeratum 6 Frequent 81-100%
Asterias rubens 5 Occasional 81-100%
Marthasterias glacialis 5 Occasional 81-100%
Isozoanthus sulcatus 4 Occasional 61-80%
Luidia ciliaris 4 Occasional 61-80%
Schizotricha frutescens 4 Frequent 61-80%
Echinus esculentus 4 Frequent 61-80%
Halecium halecinum 2 Occasional 41-60%
Henricia oculata 2 Occasional 61-80%
Parasmittina trispinosa 2 Occasional 41-60%
Polymastia boletiformis 2 Occasional 41-60%
Stelligera stuposa 2 Occasional 41-60%
Corynactis viridis 1 Occasional 41-60%
Nemertesia antennina 1 Occasional 41-60%

Similar biotopes or habitat types

This biotope is found over a broad range of sites with different wave-exposures, subject to moderately strong to very weak tidal streams. The substratum is typically similar to CR.MCR.EcCr.CarSwi.Aglo, but CR.MCR.EcCr.CarSwi.LgAs has a lower diversity of sponges and hydroids.

This biotope occurs in slightly more wave-exposed and more tide-swept sites than CR.MCR.EcCr.CarSwi.Aglo. 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.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) CR.MCR.XFa.ErSSwi

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