Description of biotope or habitat type
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Filamentous red seaweeds, sponges and Balanus crenatus on tide-swept variable-salinity infralittoral rock
Physical habitat description
| Salinity | Variable (18-35 ppt) |
|---|---|
| Wave exposure | Extremely sheltered |
| Tidal streams | Moderately strong (1-3 kn) |
| Substratum | Bedrock; boulders |
| Zone | Infralittoral |
| Depth Band | 0-5 m |
| Other Features | Heavily silted / turbid water |
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
Tide-swept infralittoral rock subject to variable salinity and turbid waters occurs in the mid to upper reaches of the rias of south-west Britain, where riverine freshwater input reduces the salinity. Very shallow rock under these conditions is characterised by a covering of filamentous red seaweed such as Callithamnion spp., Antithamnion spp., Ceramium spp., Griffithsia devoniensis, Pterothamnion plumula and Vertebrata fucoides, as well as the filamentous green seaweed Cladophora spp. Foliose red seaweeds such as Hypoglossum hypoglossoides, Cryptopleura ramosa and Erythroglossum laciniatum commonly occur, as does the foliose green seaweed Ulva lactuca. Although Saccharina latissima is often present it is usually in very low abundance (Occasional). The fluctuating salinity limits the number of species able to exist in this habitat. The animal community is dominated by the sponges Halichondria panicea and Hymeniacidon perlevis and the barnacle Balanus crenatus. The ascidians Clavelina lepadiformis and Dendrodoa grossularia can be locally abundant at some sites. The crab Carcinus maenas is usually present, as is the mussel Mytilus edulis. The bryozoan Crisularia plumosa is sometimes present. Where vertical rock is present, the seaweeds Ceramium nodulosum, P. plumula, C. ramosa, H. hypoglossoides and E. laciniatum are typically found.
Situation
This biotope is usually found amidst sediment or rock and as such there is no defined zonation of the surrounding biotopes. Shallow sediments nearby may support seagrass beds (Zostera spp.) or infaunal-dominated sediments (SS.SCS.ICS). Nearby, deeper tide-swept rock may support circalittoral communities dominated by sponges, hydroids and ascidians on stable rock (CuSpH.As) or dense bryozoans on mixed substrata (SpNemAdia & FluHocu).
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 |
|---|---|---|---|
| Hypoglossum hypoglossoides | 18 | Frequent | 81-100% |
| Pterothamnion plumula | 14 | Frequent | 61-80% |
| Erythroglossum laciniatum | 8 | Frequent | 41-60% |
| Halichondria panicea | 8 | Common | 61-80% |
| Callithamnion | 6 | Frequent | 41-60% |
| Carcinus maenas | 4 | Occasional | 41-60% |
| Hymeniacidon perlevis | 4 | Frequent | 41-60% |
| Balanus crenatus | 3 | Occasional | 61-80% |
| Vertebrata fucoides | 3 | Occasional | 21-40% |
| Antithamnion | 2 | Occasional | 21-40% |
| Cladophora | 2 | Occasional | 21-40% |
| Griffithsia devoniensis | 2 | Frequent | 21-40% |
| Mytilus edulis | 2 | Occasional | 21-40% |
| Ulva lactuca | 2 | Occasional | 21-40% |
| Crisularia plumosa | 1 | Occasional | 21-40% |
| Ceramium nodulosum | 1 | Occasional | 21-40% |
| Clavelina lepadiformis | 1 | Frequent | 21-40% |
| Cryptopleura ramosa | 1 | Common | 21-40% |
| Dendrodoa grossularia | 1 | Occasional | 21-40% |
| Saccharina latissima | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
IR.MIR.KT.SlatT
This biotope occurs at similar conditions as IR.MIR.KT.FilRVS. The species diversity is also similar between the to biotopes, but IR.LIR.K.SlatT have a higher abundance of the kelp S. latissima (Common) and of the ascidian Dendrodoa grossularia (Abundant). IR.MIR.KT.FilRVS have a higher abundance of the sponge H. panicea.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1996 (6.95) | SIR.Lsac.FiR |