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Marine Habitat Classification

Description of biotope or habitat type

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   Mytilus edulis, Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed
Tidal streams
Substratum Bedrock; large boulders
Zone Eulittoral - lower
Depth Band
Other Features Sand or silt affected

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.MLR.MusF.MytFR <I>Mytilus edulis</I>, <I>Fucus serratus</I> and red seaweeds on moderately exposed lower eulittoral rock

  • 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.


Lower eulittoral moderately exposed bedrock covered by a dense community of large individuals of the mussel Mytilus edulis, often with a scarce covering of the wrack Fucus serratus and red seaweeds. The red seaweeds may include Palmaria palmata, Mastocarpus stellatus, Ceramium spp., Audouinella spp. and Chondrus crispus. Ephemeral green seaweeds such as Ulva intestinalis and Ulva lactuca commonly occur on the shells of the mussels. The barnacle Semibalanus balanoides is common on both the mussel valves and on patches of bare rock, where the limpet Patella vulgata is also found, often at high abundance. The whelk Nucella lapillus and the winkle Littorina littorea occur within the mussel bed, as well as the polychaete Spirobranchus triqueter and the crab Carcinus maenas. The anemone Actinia equina is present in cracks and crevices. These moist areas can be overgrown by coralline crusts.


Above this biotope on sand influenced shores is a M. edulis and F. vesiculosus dominated biotope (MytFves). In the sublittoral fringe below MytFR is a biotope dominated by the kelp Laminaria digitata (Ldig.Ldig).

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Mytilus edulis 29 Abundant 81-100%
Semibalanus balanoides 9 Common 61-80%
Nucella lapillus 6 Frequent 61-80%
Mastocarpus stellatus 5 Frequent 61-80%
Palmaria palmata 5 Occasional 61-80%
Patella vulgata 5 Occasional 61-80%
Ulva intestinalis 4 Common 41-60%
Fucus serratus 4 Common 61-80%
Ulva lactuca 4 Occasional 41-60%
Corallinaceae 2 Frequent 41-60%
Audouinella 2 Frequent 21-40%
Ceramium 2 Frequent 41-60%
Littorina littorea 2 Frequent 41-60%
Actinia equina 1 Occasional 21-40%
Carcinus maenas 1 Frequent 21-40%
Chondrus crispus 1 Occasional 41-60%
Spirobranchus triqueter 1 Occasional 41-60%

Similar biotopes or habitat types

Occurs on more exposed shores. Has lower species richness with the notable absence of species such as F. serratus and L. littorea.

Occurs in similar wave exposure though in the mid eulittoral zone. F. vesiculosus dominates though F. serratus can be present in low abundance. Kelp such as L. digitata are not present and usually the abundance of the red seaweeds is lower.

Occurs on mixed substrata, and F. serratus is typically absent, while L. littorea occurs in higher abundance. Red seaweeds are usually not scarce; the barnacle Austrominius modestus can be present.

Classification history of this biotope or habitat type

Classification version Code
1996 (6.95) MLR.Myt.R

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