Description of biotope or habitat type
To understand more about what this page is describing, see How to use the classification. See also How to cite.
Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Very sheltered, Extremely sheltered |
| Tidal streams | Very strong (>6 kn), Strong (3-6 kn), Moderately strong (1-3 kn) |
| Substratum | Bedrock; boulders; cobbles |
| Zone | Eulittoral - mid |
| Depth Band | |
| Other Features |
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
Very sheltered to extremely sheltered areas of mid eulittoral rock that are subject to strong to moderate tidal streams, such as the narrows in sea lochs, and characterised by the wrack Ascophyllum nodosum. The wracks Fucus vesiculosus and Fucus serratus are occasionally present. The increased water movement encourages a rich associated fauna including several filter-feeding groups. These include the sponges Leucosolenia spp., Grantia compressa, Halichondria panicea and Hymeniacidon perlevis which frequently occur on steep and overhanging faces of boulders and bedrock. It also includes the sea squirts Dendrodoa grossularia and Ascidiella scabra, which occur on steep surfaces and beneath boulders. Hydroids such as the pink Clava multicornis can form colonies on A. nodosum while Dynamena pumila is more often found on F. vesiculosus or F. serratus. Underneath the canopy formed by the brown seaweeds is a diverse community of the red seaweeds Gelidium pusillum, Chondrus crispus, Lomentaria articulata, Membranoptera alata and coralline crusts, but the green seaweeds Ulva intestinalis, Ulva lactuca and Cladophora rupestris can be present. The filamentous red seaweed Vertebrata lanosa can usually be found growing on A. nodosum. On the rock beneath are the limpet Patella vulgata and the barnacle Semibalanus balanoides, while the crab Carcinus maenas and a variety of winkles including Littorina littorea, Littorina fabalis and Littorina obtusata can be found on or among the boulders. The whelk Nucella lapillus can either be found in cracks and crevices or preying on the barnacles.
Situation
This biotope occurs lower on the shore than the Fucus spiralis biotope (Fspi) although on some shores a narrow zone of F. vesiculosus (Fves) may occur immediately above the A. nodosum. Asc.T is found above the tide-swept F. serratus dominated biotope (Fserr.T).
Temporal variation
A. nodosum can reach an age of 25 years and the communities are usually very stable. F. vesiculosus or F. serratus can occur in patches where the A. nodosum has been removed.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Ascophyllum nodosum | 19 | Super abundant | 81-100% |
| Dynamena pumila | 6 | Frequent | 81-100% |
| Patella vulgata | 6 | Occasional | 81-100% |
| Vertebrata lanosa | 6 | Frequent | 81-100% |
| Semibalanus balanoides | 5 | Occasional | 61-80% |
| Corallinaceae | 4 | Frequent | 61-80% |
| Ulva lactuca | 4 | Occasional | 61-80% |
| Nucella lapillus | 4 | Occasional | 81-100% |
| Fucus vesiculosus | 4 | Occasional | 61-80% |
| Clava multicornis | 3 | Frequent | 41-60% |
| Dendrodoa grossularia | 3 | Frequent | 61-80% |
| Ulva intestinalis | 3 | Occasional | 61-80% |
| Fucus serratus | 3 | Occasional | 61-80% |
| Halichondria panicea | 3 | Occasional | 61-80% |
| Carcinus maenas | 2 | Occasional | 61-80% |
| Cladophora rupestris | 2 | Frequent | 41-60% |
| Gelidium pusillum | 2 | Frequent | 41-60% |
| Lomentaria articulata | 2 | Occasional | 41-60% |
| Chondrus crispus | 1 | Frequent | 41-60% |
| Grantia compressa | 1 | Occasional | 41-60% |
| Hymeniacidon perlevis | 1 | Rare | 41-60% |
| Littorina littorea | 1 | Frequent | 21-40% |
| Littorina | 1 | Occasional | 41-60% |
| Membranoptera alata | 1 | Rare | 41-60% |
Similar biotopes or habitat types
LR.LLR.F.Asc.FS
Occurs on bedrock with weak tidal streams. Lower diversity of filter feeders and lacks species such as the sponges Leucosolenia spp. and G. compressa, the hydroid C. multicornis or the sea squirt D. grossularia .
LR.LLR.FVS.AscVS
Occurs on bedrock or mixed substrata with variable salinity. Coralline crusts and C. crispus, N. lapillus and anemone Actinia equina are not usually present in this species impoverished biotope. It is also lacks the filter feeders mentioned above.
LR.LLR.F.Asc.X
Occurs on mixed substrata in fully marine conditions. Has a lower abundance and diversity of red seaweeds and lacks species such as Leucosolenia spp. and G. compressa, the hydroid C. multicornis and the sea squirt D. grossularia.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1997 (97.06) | SLR.ASC.T |
Photos
