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Marine Habitat Classification

Description of biotope or habitat type

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   Large solitary ascidians and erect sponges on wave-sheltered circalittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Very sheltered, Extremely sheltered
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Bedrock, boulders
Zone Circalittoral
Depth Band 5-10 m, 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.LCR.BrAs.LgAsSp Large solitary ascidians and erect sponges 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 biotope is typically found on silty circalittoral bedrock and boulders in wave-sheltered channels subject to varying amounts of tidal flow. These fully marine inlets and channels have steep, often vertical sides with small terraces or ledges. This biotope, characterised by erect sponges and large solitary ascidians, appears to be biologically diverse. A diverse ascidian fauna is generally present, including Ascidia mentula, Aplidium punctum, Corella parallelogramma, Ascidia virginea, Botryllus schlosseri, Clavelina lepadiformis and Ciona intestinalis. An equally diverse sponge fauna, with massive erect sponges particularly noticeable, compliments these species. Dominant species include Amphilectus fucorum, Dysidea fragilis, Tethya aurantium, Polymastia boletiformis, Raspailia ramosa, Stelligera stuposa, Polymastia mamilliaris and Pachymatisma johnstonia. Other sponges present are Suberites carnosus, Haliclona fistulosa, Stelligera montagui, Mycale (Aegogropila) rotalis, Haliclona (Haliclona) simulans, Iophon hyndmani and Hemimycale columella. Various sponge crusts may also be present but in most cases in lower abundances. Other significant components of the community include the cup coral Caryophyllia smithii and various echinoderms, including the sea urchin Echinus esculentus and the starfish Henricia oculata and Marthasterias glacialis. Small isolated clumps of Nemertesia antennina and individual Alcyonium digitatum may be seen, whilst the top shell Calliostoma zizyphinum may also be present. At present, there are relatively few records in this biotope, as it is only reported from around the south-western coast of Ireland, where sponge diversity is very high.


Due to the sheltered nature of the biotope, LgAsSp is usually situated on bedrock/boulder outcrops associated with mud slopes and plains. Typical species found within these circalittoral muds include the seapen Virgularia mirablis and the anemone Pachycerianthus multiplicatus. In the infralittoral zone, sheltered kelp biotopes such as LsacX with Saccharina latissima occur frequently. In areas where there is a slightly stronger tidal-stream, the circalittoral muddy plains become more muddy gravel plains and slopes. Typical species found within these habitats include the anemones Mesacmaea mitchellii and Aureliana heterocera. When tidal-streams becomes negligible, but with similar wave-sheltered conditions, you tend to find CarSwi.Aglo biotopes occurring, especially in the same geographical location (around south-west/west Ireland) as LgAsSp.

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
Ascidia mentula 7 Common 81-100%
Amphilectus fucorum 7 Frequent 81-100%
Dysidea fragilis 5 Frequent 61-80%
Aplidium punctum 4 Frequent 61-80%
Henricia oculata 4 Occasional 81-100%
Polymastia boletiformis 4 Frequent 61-80%
Raspailia ramosa 4 Frequent 61-80%
Tethya aurantium 4 Frequent 61-80%
Ascidia virginea 3 Common 41-60%
Caryophyllia smithii 3 Frequent 61-80%
Corella parallelogramma 3 Common 41-60%
Pachymatisma johnstonia 3 Frequent 61-80%
Polymastia mamillaris 3 Frequent 61-80%
Stelligera stuposa 3 Occasional 61-80%
Botryllus schlosseri 2 Occasional 61-80%
Clavelina lepadiformis 2 Occasional 41-60%
Haliclona fistulosa 2 Occasional 41-60%
Haliclona oculata 2 Frequent 41-60%
Iophon hyndmani 2 Occasional 41-60%
Marthasterias glacialis 2 Occasional 41-60%
Mycale (Aegogropila) rotalis 2 Frequent 41-60%
Stelligera montagui 2 Frequent 41-60%
Suberites carnosus 2 Frequent 41-60%
Echinus esculentus 2 Occasional 61-80%
Porifera 1 Frequent 21-40%
Alcyonium digitatum 1 Occasional 41-60%
Calliostoma zizyphinum 1 Occasional 41-60%
Ciona intestinalis 1 Occasional 41-60%
Hemimycale columella 1 Occasional 41-60%
Nemertesia antennina 1 Occasional 41-60%

Similar biotopes or habitat types

This biotope is found under similar silty, wave-sheltered conditions as CR.LCR.BrAs.LgAsSp but with negligible tidal streams. Found in sheltered sealochs, there is an impoverished faunal component with solitary ascidians dominating. It lacks the diverse sponge component which is characteristic of CR.LCR.BrAs.LgAsSp.

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