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.
- 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 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.
Situation
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