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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.

   Faunal communities on variable or reduced salinity infralittoral rock

Physical habitat description

Salinity Reduced (18-30ppt), Variable (18-35 ppt), Low (<18ppt)
Wave exposure Very sheltered, Extremely sheltered
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Bedrock, shells, mud, artificial and other
Zone Infralittoral
Depth Band 0-5 m
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.

Distribution of habitat IR.LIR.IFaVS Faunal communities on variable or 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.


Shallow subtidal rocky habitats which support faunal-dominated communities, with seaweed communities only poorly developed or absent. In some sealochs dense mussel Mytilus edulis beds (MytRS) develop in tide-swept channels, whilst upper estuarine rocky habitats in the south-west coast rias may support particular brackish-water tolerant faunas (CcasEle; HarCon).


No situation data available.

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 65 Abundant 81-100%
Balanus crenatus 8 Frequent 41-60%
Carcinus maenas 6 Occasional 41-60%
Halichondria panicea 3 Common 21-40%
Ectocarpaceae 2 Frequent 21-40%
Metridium senile 2 Frequent 21-40%
Ascidiella aspersa 1 Occasional 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) SIR.EstFa

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