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Marine Habitat Classification

Description of biotope or habitat type

To understand more about what this page is describing, see How to use the classification. See also How to cite.

   Bryozoan turf and erect sponges on tide-swept 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)
Substratum Bedrock; boulder
Zone Circalittoral - lower, Circalittoral - upper
Depth Band 10-20 m, 20-30 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.HCR.XFa.ByErSp Bryozoan turf and erect sponges on tide-swept 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 biotope is typically found on wave-exposed circalittoral bedrock or boulders subject to tidal streams ranging from moderately strong to strong. It often has a thin layer of silt covering the seabed, and is characterised by a bryozoan/hydroid turf with erect sponges. Typical bryozoans to be found include crisiids, Alcyonidium diaphanum, Flustra foliacea, Pentapora foliacea, Crisularia plumosa and Bugulina flabellata, while typical hydroids include Nemertesia antennina, Nemertesia ramosa and Halecium halecinum. The soft coral Alcyonium digitatum is frequently recorded on the tops of boulders and rocky outcrops. Characteristic erect sponges include Raspailia ramosa, Stelligera stuposa and Stelligera montagui; other sponges present include Cliona celata, Dysidea fragilis, Pachymatisma johnstonia, Polymastia boletiformis, Hemimycale columella, Amphilectus fucorum, Polymastia mamillaris and Tethya aurantium. Other species present include Caryophylia smithii, Actinothoe sphyrodeta, Corynactis viridis, Urticina felina, Balanus crenatus, Asterias rubens, Marthasterias glacialis, Henricia oculata, Echinus esculentus, Clavelina lepadiformis, Calliostoma zizyphinum and Necora puber. Three variants of this biotope have been described, but all are characterised by a bryozoan turf with erect sponges. ByErSp.Eun is found primarily on circalittoral bedrock and is dominated by the seafan Eunicella verrucosa. ByErSp.DysAct is found under slightly stronger tide-swept conditions, and is characterised particularly by the sponge D. fragilis and the anemone A. sphyrodeta. Finally ByErSp.Sag is characterised by the anemone Cylista elegans.


No situation data available.

Temporal variation

No temporal variation data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Alcyonium digitatum 5 Frequent 81-100%
Caryophyllia smithii 4 Frequent 61-80%
Cliona celata 4 Occasional 81-100%
Nemertesia antennina 4 Frequent 81-100%
Alcyonidium diaphanum 3 Frequent 61-80%
Asterias rubens 3 Frequent 61-80%
Dysidea fragilis 3 Frequent 61-80%
Actinothoe sphyrodeta 2 Occasional 61-80%
Balanus crenatus 2 Occasional 21-40%
Crisularia plumosa 2 Frequent 41-60%
Calliostoma zizyphinum 2 Occasional 41-60%
Clavelina lepadiformis 2 Occasional 61-80%
Corynactis viridis 2 Frequent 41-60%
Amphilectus fucorum 2 Frequent 41-60%
Flustra foliacea 2 Frequent 41-60%
Hemimycale columella 2 Occasional 61-80%
Nemertesia ramosa 2 Occasional 61-80%
Pachymatisma johnstonia 2 Occasional 61-80%
Polymastia boletiformis 2 Frequent 61-80%
Raspailia ramosa 2 Occasional 61-80%
Stelligera stuposa 2 Occasional 41-60%
Echinus esculentus 2 Occasional 61-80%
Bugulina flabellata 1 Occasional 41-60%
Crisiidae 1 Frequent 41-60%
Halecium halecinum 1 Frequent 41-60%
Henricia oculata 1 Occasional 41-60%
Marthasterias glacialis 1 Occasional 41-60%
Necora puber 1 Occasional 41-60%
Pentapora foliacea 1 Occasional 41-60%
Polymastia mamillaris 1 Occasional 41-60%
Stelligera montagui 1 Occasional 41-60%
Tethya aurantium 1 Occasional 41-60%
Urticina felina 1 Occasional 41-60%

Similar biotopes or habitat types

Not applicable or unknown.


CR.HCR.XFA.ByErSp Bryozoan turf and erect sponges on tide-swept circalittoral rock, Sligneach Mor, Sunart. Rohan Holt© JNCC
CR.HCR.XFA.ByErSp Bryozoan turf and erect sponges on tide-swept circalittoral rock, Sligneach Mor, Sunart. Rohan Holt© JNCC

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