Description of biotope or habitat type
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Mytilus edulis and barnacles on very exposed eulittoral rock
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Very exposed, Exposed |
| Tidal streams | |
| Substratum | Bedrock |
| Zone | Eulittoral |
| Depth Band | |
| Other Features | Also occurs on vertical and steep bedrock on moderately exposed shores |
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
On very exposed to exposed rocky shores the eulittoral zone, particularly the mid and lower shore, is typically characterised by patches of small individuals of the mussel Mytilus edulis interspersed with patches of the barnacle Semibalanus balanoides and individuls of the limpet Patella vulgata. Amongst the mussels small individuals of red seaweeds including Ceramium spp., Corallina officinalis and Mastocarpus stellatus can be found. The foliose red seaweeds Porphyra umbilicalis and Palmaria palmata are commonly found as epiphytes on M. edulis where they can form luxuriant growths. The abundance of the red seaweeds generally increases down the shore and in the lower eulittoral they may form a distinct zone in which mussels or barnacles are scarce (FR, Coff.Coff or Him). Where M. edulis occurs on steep rock, red seaweeds are scarce and restricted to the lower shore. The whelk Nucella lapillus and a few winkles such as Littorina spp. can occur where cracks and crevices provide a refuge in the rock. Fucoids are generally absent, although some non-vesiculate Fucus vesiculosus may occur where the shore slopes more gently. This biotope also occurs on steep moderately exposed shores which experience increased wave energy.
Situation
MytB is generally found above a zone of either mixed turf-forming red seaweeds (FR), Himanthalia elongata (Him) or above the sublittoral fringe kelp Alaria esculenta (Ala) zone. Above MytB there may be a Verrucaria maura zone (Ver.Ver), a V. maura and sparse barnacle zone (Ver.B), often with P. umbilicalis or a denser barnacle and limpet zone (Sem; FvesB). In addition, patches of lichen Lichina pygmaea with the barnacle Chthamalus montagui (Cht.Cht) may also occur above this biotope, particularly on southern shores.
Temporal variation
Severe winter storms can cause periodic removal of this mussel and barnacle community.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Mytilus edulis | 32 | Abundant | 81-100% |
| Semibalanus balanoides | 24 | Common | 81-100% |
| Patella vulgata | 19 | Common | 81-100% |
| Nucella lapillus | 5 | Frequent | 41-60% |
| Porphyra umbilicalis | 5 | Frequent | 41-60% |
| Corallina officinalis | 2 | Occasional | 41-60% |
| Littorina | 2 | Common | 21-40% |
| Ceramium shuttleworthianum | 1 | Occasional | 21-40% |
| Mastocarpus stellatus | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
LR.HLR.MusB.Cht.Cht
Occurs at same wave exposure, but on more steep faces in the upper eulittoral zone. Chthamalus spp. dominate and the abundance of M. edulis is lower (Occasional). The presence of red seaweeds is more sparse, but the black lichen Verrucaria spp. may be present.
LR.HLR.MusB.Sem.Sem
Typically occurs in less wave exposed conditions. The abundance of M. edulis is lower (Occasional) or confined to crevices where they may be dense. Red seaweeds are also scarce.
LR.MLR.MusF.MytFves
Occurs on moderately exposed coasts, but otherwise in similar physical conditions. It has a higher species diversity and the wrack Fucus vesiculosus is present (Common).
LR.MLR.MusF.MytFR
Occurs on moderately exposed coasts, but otherwise in similar physical conditions. It has a higher species diversity and more red seaweeds are usually present. The wrack Fucus serratus is usually present (Common).Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1995 | LRK.MB |
Photos
