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Marine Habitat Classification

Description of biotope or habitat type

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   Mussel and/or barnacle communities

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Extremely exposed, Very exposed, Exposed, Moderately exposed
Tidal streams
Substratum Bedrock; large boulders
Zone Eulittoral - mid, Eulittoral - upper
Depth Band Mid shore, Upper shore
Other Features Also on sheltered vertical bedrock

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.

Distribution of habitat LR.HLR.MusB Mussel and/or barnacle communities

  • 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.


Communities on very exposed to moderately exposed upper and mid eulittoral bedrock and boulders dominated by the mussel Mytilus edulis (MytB), barnacles Chthamalus spp. and/or Semibalanus balanoides and limpets Patella spp. (Cht, Sem). Several variants are identified. Some shores are characterised by dense bands of the barnacle Semibalanus balanoides and the limpet Patella vulgata (Sem). The barnacles may be covered by Porphyra umbilicalis on the upper shore of exposed sites. Cracks and crevices in the rock provide a refuge for small individuals of the mussel M. edulis, winkles Littorina saxatilis and the whelk Nucella lapillus. Red seaweeds also frequently occupy damp crevices, particularly Ceramium shuttleworthianum, Corallina officinalis, Osmundea pinnatifida and encrusting coralline algae, but the non-vesiculate form of the wrack Fucus vesiculosus might be present (Sem.FvesR). Large numbers of the winkle Littorina littorea often dominate fields of large boulders or shores with a more mixed substratum (Sem.LlitX). There is much regional variation affecting the zonation of barnacles in the British Isles. In the north-west C. montagui and/or C. stellatus can form a distinct band above S. balanoides. In the south-west C. montagui and/or C. stellatus can be the dominant barnacles throughout the eulittoral zone (Cht.Cht). On the east coasts S. balanoides is able to extend to the upper shore due to the absence of Chthamalus spp. and thereby any competition. The lichen Lichina pygmaea may be prominent, especially in the south, where it can form distinct patches or even a separate zone among the Chthamalus spp. (Cht.Lpyg). In areas of soft rock (e.g. shales), the barnacles may be scarce or absent and the rock dominated by P. vulgata.


This biotope complex is found in the mid to upper eulittoral on very to moderately exposed shores below the lichen dominated biotopes (Lic) and is typically characterised by patches of mussels M. edulis interspersed with barnacles. Below the MusB biotopes is a community dominated by the wrack Himanthalia elongata and red seaweeds such as C. officinalis, Mastocarpus stellatus and O. pinnatifida (FR). With decreasing wave exposure F. vesiculosus is able to survive, gradually replacing the barnacles and P. vulgata biotope (FvesB). On such moderately exposed shores MusB biotopes may occur on steep and vertical faces, while fucoids dominate the flatter areas (Sem.FvesR, FvesB).

Temporal variation

No temporal variation data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Semibalanus balanoides 33 Common 81-100%
Patella vulgata 21 Common 61-80%
Mytilus edulis 15 Frequent 61-80%
Littorina littorea 6 Frequent 21-40%
Nucella lapillus 5 Frequent 41-60%
Littorina saxatilis 2 Frequent 21-40%
Actinia equina 1 Occasional 21-40%
Chthamalus montagui 1 Rare 1-20%
Corallina officinalis 1 Occasional 21-40%
Littorina 1 Common 21-40%
Mastocarpus stellatus 1 Occasional 21-40%
Palmaria palmata 1 Occasional 21-40%
Porphyra umbilicalis 1 Frequent 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) ELR.BPat (part)
1997 (97.06) ELR.MB (part)
1995 LRK.BP


LR.HLR.MUSB Mussel and/or barnacle communities, S Point En nan Gobhar, Loch Ailort. Keith Hiscock© JNCC
LR.HLR.MUSB Mussel and/or barnacle communities, S Point En nan Gobhar, Loch Ailort. Keith Hiscock© JNCC

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