Description of biotope or habitat type
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Faunal crusts on wave-surged littoral cave walls
Physical habitat description
| Salinity | Full (30-35 ppt), Variable (18-35 ppt) |
|---|---|
| Wave exposure | Exposed, Moderately exposed, Sheltered |
| Tidal streams | |
| Substratum | Bedrock |
| Zone | Eulittoral |
| Depth Band | |
| Other Features | Moist, dark caves; Vertical faces; Ceilings |
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'
Point data based on records in the UK Marine Recorder Snapshot.
Description
The inner walls of caves, predominantly in the mid shore in wave-surged conditions dominated by barnacles Semibalanus balanoides, and Verruca stroemia, with patches of encrusting sponges such as Halichondria panicea and Grantia compressa and occasional patches of the mussel Mytilus edulis. Increased moisture allows a denser faunal population than ScrFa to develop within the cave. The limpet Patella vulgata and spirorbid tube-forming polychaetes can be present. The hydroid Dynamena pumila and anemones such as Metridium senile and Actinia equina may occur towards the lower reaches of the cave. Where a dense faunal turf of barnacles or bryozoan crusts covers the cave walls, the biotope can also extend to cover the ceiling and may be accompanied by the bryozoan Alcyonidium diaphanum. Variations of this biotope may occur in mid and lower shore scoured caves in south Wales the rock is dominated by dense Sabellaria alveolata. In south-west England the rock can be completely covered by the barnacle Perforatus perforatus. There may be a variation in the species composition from cave to cave, depending on local conditions.
Situation
This biotope usually occurs above the sand/pebble scoured ScrFa zone and may extend to the ceilings of the caves.
Temporal variation
Unknown.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Actinia equina | 27 | Frequent | 61-80% |
| Semibalanus balanoides | 11 | Occasional | 41-60% |
| Halichondria panicea | 9 | Occasional | 41-60% |
| Bryozoa indet crusts | 7 | Common | 21-40% |
| Spirorbinae | 7 | Common | 21-40% |
| Verruca stroemia | 6 | Common | 21-40% |
| Patella vulgata | 5 | Rare | 41-60% |
| Corallinaceae | 4 | Super abundant | 21-40% |
| Perforatus perforatus | 4 | Occasional | 21-40% |
| Mytilus edulis | 4 | Occasional | 41-60% |
| Dynamena pumila | 3 | Frequent | 21-40% |
| Grantia compressa | 3 | Occasional | 21-40% |
| Metridium senile | 3 | Occasional | 21-40% |
Similar biotopes or habitat types
Not applicable or unknown.
