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Marine Habitat Classification

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.

   Mytilus edulis beds on reduced salinity infralittoral rock

Physical habitat description

Salinity Reduced (18-30ppt), Low (<18ppt)
Wave exposure Very sheltered, Extremely sheltered
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock; boulders
Zone Infralittoral
Depth Band 0-5 m
Other Features May occur on vertical rock.

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 IR.LIR.IFaVS.MytRS <I>Mytilus edulis</I> beds on reduced salinity infralittoral 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'
  • Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat

Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.


This biotope occur in shallow, often tide-swept, reduced salinity conditions. Dense beds of the mussel Mytilus edulis with the occasional barnacle Balanus crenatus. A wide variety of epifaunal colonisers on the mussel valves, including seaweeds, hydroids and bryozoans can be present. Predatory starfish Asterias rubens can be very common in this biotope. This biotope generally appears to lack large kelp plants, although transitional examples containing mussels and kelps plants may also occur. More information needed to validate this description.


Occurs in tide-swept entrance channels in very enclosed basins of sealochs where the basins are typically of lowered salinity. Also occurs in very sheltered subtidal rock (often vertical) in lagoons.

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Balanus crenatus 85 Common 81-100%
Mytilus edulis 9 Abundant 81-100%
Asterias rubens 1 Frequent 81-100%

Similar biotopes or habitat types

Not applicable or unknown.

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