Description of biotope or habitat type
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Sponges, bryozoans and ascidians on deeply overhanging lower shore bedrock or caves
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Moderately exposed, Sheltered |
| Tidal streams | |
| Substratum | Bedrock |
| Zone | Eulittoral - lower, Eulittoral - mid, Sublittoral fringe |
| Depth Band | Lower shore |
| Other Features | Overhanging and shaded vertical rock; Lower shore caves |
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
Overhanging, and shaded vertical, bedrock on the lower shore and in lower shore caves, which is not subject to appreciable wave-surge, characterised by crusts of bryozoans including Oshurkovia littoralis, sponges such as Grantia compressa, Halichondria panicea, Sycon ciliatum and Hymeniacidon perlevis and the ascidian Botryllus schlosseri. On overhangs, the hydroid Dynamena pumila hangs in distinct form from overhanging rock. The barnacles Balanus crenatus, Perforatus perforatus (sometimes at high densities) and Semibalanus balanoides, and the calcareous tube-forming polychaetes Spirorbis spp. and Spirobranchus triqueter can be present as well. Certain species which are generally confined to the sublittoral, including the anemones Metridium senile and Corynactis viridis, may be found in the lower shore caves and overhangs. Littoral species such as Actinia equina are also present. The only algae present are coralline crusts. The list of characterising species partly reflects the variation in the species composition between individual overhangs and caves although this biotope can have a high species richness.
Situation
This biotope is found in the lower eulittoral and sublittoral fringe in less wave-surged conditions than that of SR.Den.
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 |
|---|---|---|---|
| Halichondria panicea | 21 | Frequent | 61-80% |
| Hymeniacidon perlevis | 10 | Occasional | 41-60% |
| Dynamena pumila | 9 | Frequent | 41-60% |
| Oshurkovia littoralis | 5 | Frequent | 21-40% |
| Semibalanus balanoides | 3 | Frequent | 21-40% |
| Actinia equina | 3 | Occasional | 21-40% |
| Grantia compressa | 3 | Frequent | 21-40% |
| Spirobranchus triqueter | 3 | Occasional | 21-40% |
| Corallinaceae | 2 | Occasional | 21-40% |
| Balanus crenatus | 2 | Occasional | 21-40% |
| Perforatus perforatus | 2 | Occasional | 21-40% |
| Botryllus schlosseri | 2 | Rare | 21-40% |
| Corynactis viridis | 2 | Occasional | 21-40% |
| Spirobranchus | 2 | Frequent | 21-40% |
| Porifera indet crusts | 2 | Occasional | 21-40% |
| Bryozoa indet crusts | 1 | Frequent | 21-40% |
| Dendrodoa grossularia | 1 | Rare | 21-40% |
| Dysidea fragilis | 1 | Frequent | 21-40% |
| Metridium senile | 1 | Occasional | 21-40% |
| Sycon ciliatum | 1 | Rare | 21-40% |
Similar biotopes or habitat types
LR.FLR.CvOv.SpR
LR.FLR.CvOv.SpByAs is distinguished from SR by its lack of shade-tolerant red algae, although some may occur on the edges of the overhangs.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1997 (97.06) | LR.SByAs |
| 1996 (6.95) | MLR.S.ByAs |
| 1995 | LRK.BAS |
Photos
