Description of biotope or habitat type
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Rhodothamniella floridula on sand-scoured lower eulittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Exposed, Moderately exposed |
| Tidal streams | Moderately strong (1-3 kn), Weak (>1 kn) |
| Substratum | Bedrock; boulders |
| Zone | Eulittoral - lower |
| Depth Band | Lower shore |
| Other Features | Sand-scour |
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
Lower eulittoral and sublittoral fringe bedrock and boulders subject to mild sand-scouring characterised by a canopy of the wracks Fucus serratus or Fucus vesiculosus, beneath which a mat of the sand-binding red seaweed Rhodothamniella floridula occurs. These mats can form distinct areas without F. serratus. The small hummocks of R. floridula also contain a diversity of other red seaweeds tolerant of sand scour, e.g. Palmaria palmata, Chondrus crispus, coralline crusts and Mastocarpus stellatus. The brown seaweed Cladostephus spongiosus or the ephemeral green seaweed Ulva intestinalis, Ulva lactuca or Cladophora rupestris may occur. The hydroid Dynamena pumila can form colonies on the F. serratus fronds. The barnacle Semibalanus balanoides, the limpet Patella vulgata, the anemone Actinia equina and the polychaete Spirobranchus triqueter may be present where bedrock are available along with a few winkles such as Littorina littorea. In addition, polychaetes and amphipods may burrow into the R. floridula mat, while the mussel Mytilus edulis is restricted to small crevices in the bedrock. The species diversity of this biotope is normally low and there can be much variation in the species composition from site to site.
Situation
Above this biotope in sand influenced areas are a community dominated by M. edulis and F. vesiculosus or where the sand scour is more severe, is a biotope dominated by ephemeral seaweeds such as Ulva spp. and the red seaweed Porphyra spp. (EntPor). Below this biotope are biotopes dominated by F. serratus and/or red seaweeds (see Fser variants) or biotopes dominated by kelp such as Alaria esculenta and/or Laminaria digitata (Ala.Ldig).
Temporal variation
Where sand scour is more severe, fucoids and R. floridula may be rare or absent and green ephemeral seaweeds dominate the substratum (EntPor).
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Rhodothamniella floridula | 27 | Abundant | 81-100% |
| Fucus serratus | 8 | Abundant | 61-80% |
| Mastocarpus stellatus | 8 | Frequent | 61-80% |
| Semibalanus balanoides | 7 | Occasional | 41-60% |
| Ulva intestinalis | 7 | Common | 41-60% |
| Patella vulgata | 6 | Occasional | 21-40% |
| Ulva lactuca | 6 | Occasional | 61-80% |
| Corallinaceae | 3 | Common | 41-60% |
| Cladostephus spongiosus | 3 | Occasional | 41-60% |
| Palmaria palmata | 3 | Occasional | 41-60% |
| Chondrus crispus | 2 | Frequent | 21-40% |
| Cladophora rupestris | 2 | Occasional | 21-40% |
| Dynamena pumila | 2 | Occasional | 21-40% |
| Littorina littorea | 2 | Occasional | 21-40% |
| Actinia equina | 1 | Occasional | 21-40% |
| Carcinus maenas | 1 | Occasional | 21-40% |
| Mytilus edulis | 1 | Occasional | 21-40% |
| Fucus vesiculosus | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
LR.MLR.BF.Fser
These biotopes occurs on lower shore rock, but lack the sand scour. R. floridula is not usually present in sufficient density to form a mat on the rock.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1996 (6.95) | MLR.Aud |
| 1995 | LRK.FSE.AUD |
Photos
