Description of biotope or habitat type
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Spirobranchus triqueter with barnacles and bryozoan crusts on unstable circalittoral cobbles and pebbles
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Very exposed, Exposed, Moderately exposed |
| Tidal streams | Strong (3-6 kn), Moderately strong (1-3 kn) |
| Substratum | Cobbles and pebbles with sand |
| Zone | Circalittoral |
| Depth Band | 5-10 m, 10-20 m, 20-30 m, 30-50 m, 50-100 m |
| Other Features |
Biotope origin
| Derived using data from | Video/Grab |
| Faunal group | Epifauna |
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 characterised by a few ubiquitous robust and/or fast growing ephemeral species which are able to colonise pebbles and unstable cobbles and slates which are regularly moved by wave and tidal action. The main cover organisms tend to be restricted to calcareous tube worms such as Spirobranchus triqueter or S. lamarcki, small barnacles including Balanus crenatus and Balanus balanus, and a few bryozoan and coralline algal crusts. Barnacles may be predominantly observed in shallower variants of the biotope. Scour action from the mobile substratum prevents colonisation by more delicate species. Occasionally, in tide-swept conditions tufts of hydroids such as Sertularia argentea and Hydrallmania falcata are present. Occasional epifauna may include Asterias rubens, Cerianthus lloydii, and Alcyonium digitatum. Bryozoa Parazoanthus anguicomus, Ulva, Porania, and Porifera can also be present. This biotope often grades into SS.SMx.CMx.FluHyd which is characterised by large amounts of the above hydroids on stones also covered in Spirobranchus and barnacles. The main difference here is that SS.SMx.CMx.FluHyd seems to develop on more stable, consolidated cobbles and pebbles or larger stones set in sediment in moderate tides. These stones may be disturbed in the winter and therefore long-lived and fragile species are not found.
Situation
This biotope is found on exposed open coasts, at the entrance to marine inlets as well as offshore deeper waters.
Temporal variation
No temporal data available.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | % of core records where taxon was recorded | Relative frequency % |
|---|---|---|---|
| Spirobranchus | 67 | 41-60% | 51.3 |
| Hydrozoa | 25 | 1-20% | 9.5 |
| Paguridae | 1 | 1-20% | 2.3 |
| Alcyonium digitatum | 1 | 1-20% | 1.3 |
| Bryozoa | 1 | 1-20% | 1.2 |
| Spirobranchus triqueter | 1 | 1-20% | 0.9 |
| Balanus crenatus | 1 | 1-20% | 0.2 |
| Balanus balanus | 1 | 1-20% | 0.1 |
Similar biotopes or habitat types
IR.FIR.SG.CC.Mo
A similar shallow water biotope occurring on cobbles at the base of surge gullies.
SS.SMx.CMx.FluHyd
As substratum stability increases (larger rocks and less turbulent wave action) more species are able to colonise the sea bed. SS.SMx.CMx.FluHyd, CR.HCR.XFa.FluCoAs.SmAs and CR.HCR.XFa.ByErSp.DysAct in that order, represent the progression from SS.SCS.CCS.SpiB to more stable mixed substrata although still with a high proportion of scour- and sand-tolerant species.Classification history of this biotope or habitat type
| Classification version | Code | Habitat name |
|---|---|---|
| 2015 (15.03) | SS.SCS.CCS.PomB | Pomatoceros triqueter with barnacles and bryozoan crusts on unstable circalittoral cobbles and pebbles |
| 2004 (04.05) | SS.SCS.CCS.PomB | Pomatoceros triqueter with barnacles and bryozoan crusts on unstable circalittoral cobbles and pebbles |
| 1997 (97.06) | SS.ECR.EFa.PomByC | Pomatoceros triqueter, Balanus crenatus and bryozoan crusts on mobile circalittoral cobbles and pebbles |