Description of biotope or habitat type
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Solitary ascidians, including Ascidia mentula and Ciona intestinalis, on wave-sheltered circalittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Moderately exposed, Sheltered, Very sheltered |
| Tidal streams | Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible) |
| Substratum | Bedrock, boulders, cobbles |
| Zone | Circalittoral |
| Depth Band | 5-10 m, 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 predominantly occurs on the upper faces of wave-sheltered (often sealochs) circalittoral bedrock, boulder and cobble slopes with little tidal flow. Apart from the solitary ascidians Ciona intestinalis and Ascidia mentula, this biotope has a rather barren, pink appearance (due to the encrusting red algae), possibly due to grazing pressure from the sea urchin Echinus esculentus. Other organisms found encrusting the rocky surface include the polychaete Spirobranchus triqueter and the cup coral Caryophyllia smithii. Other species occasionally encountered include Alcyonium digitatum, Asterias rubens, Pagurus berhardus, Crossaster papposus, Antedon bifida and Metridium senile. Crustaceans such as Munida rugosa and Cancer pagurus may be recorded in crevices. Two variants of this biotope exist: AmenCio.Ant and AmenCio.Bri. AmenCio.Bri occurs where is a dense carpet of brittlestars which sometimes completely cover the rocky substratum. Species present include Ophiothrix fragilis, Ophiocomina nigra and Ophiura albida.
Situation
No situation data available.
Temporal variation
The abundance of C. intestinalis tends to fluctuate seasonally, so it may appear absent at a site at one time of year and then be present at other times, altering the visual appearance of the biotope. Other solitary ascidian species such as A. mentula and Ascidiella aspersa tend to be longer-lived (approximately 7 years and 3 years, respectively).
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Ophiothrix fragilis | 15 | Abundant | 61-80% |
| Ophiocomina nigra | 10 | Common | 41-60% |
| Echinus esculentus | 10 | Occasional | 61-80% |
| Corallinaceae | 8 | Common | 41-60% |
| Spirobranchus triqueter | 7 | Frequent | 41-60% |
| Asterias rubens | 6 | Occasional | 61-80% |
| Ciona intestinalis | 4 | Occasional | 41-60% |
| Pagurus bernhardus | 4 | Occasional | 41-60% |
| Munida rugosa | 3 | Occasional | 21-40% |
| Ophiura albida | 3 | Occasional | 21-40% |
| Alcyonium digitatum | 2 | Occasional | 21-40% |
| Ascidia mentula | 2 | Occasional | 21-40% |
| Crossaster papposus | 2 | Occasional | 41-60% |
| Antedon bifida | 1 | Occasional | 21-40% |
| Cancer pagurus | 1 | Rare | 21-40% |
| Caryophyllia smithii | 1 | Occasional | 21-40% |
| Metridium senile | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
Not applicable or unknown.