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Marine Habitat Classification

Description of biotope or habitat type

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   Sparse fauna (barnacles and spirorbids) on sand/pebble-scoured rock in littoral caves

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered
Tidal streams
Substratum Bedrock
Zone Eulittoral
Depth Band
Other Features Moist, dark caves; Vertical faces

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.FLR.CvOv.ScrFa Sparse fauna (barnacles and spirorbids) on sand/pebble-scoured rock in littoral caves

  • 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.


Upper to lower shore sand- or pebble-scoured cave walls characterised by an impoverished faunal assemblage which may include bryozoan crusts, scattered sponges Halichondria panicea, barnacles such as Semibalanus balanoides or often large Balanus crenatus and the limpet Patella vulgata. The isopod Ligia oceanica may seek refuge in crevices in the rock, and due to the decreased effect of desiccation in these damp caves, other species such as the anemone Actinia equina and spirorbid polychaetes are able to extend further up the shore than normally found on open rock. The lower section of the wall which is subject to greatest scour may be characterised by a band of Spirobranchus triqueter and spirorbid tube-forming polychaetes. In wave sheltered conditions, this biotope may extend to the cave ceiling. The rear of caves on the lower shore may support only sparse fauna consisting of spirorbid polychaetes and barnacles such as Chthamalus montagui with scattered Spirobranchus sp., scattered bryozoan and coralline crusts and in the south-west, occasional Sabellaria alveolata. Shade-tolerant red algae such as Lomentaria articulata may occasionally occur. Due to the low species abundance in this biotope, there may be a variation from cave to cave, depending on local conditions.


This biotope is found in caves between the barren (of macro-fauna or flora) or very species poor BarCv zone and the wave-surged, more densely populated FaCr zone. On the walls above the scour and near the cave entrance the community may grade into a red algal dominated community (AudCla).

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Spirorbinae 29 Common 41-60%
Semibalanus balanoides 24 Common 41-60%
Corallinaceae 12 Common 41-60%
Spirobranchus triqueter 7 Occasional 41-60%
Patella vulgata 6 Occasional 41-60%
Actinia equina 4 Occasional 21-40%
Chthamalus montagui 4 Common 21-40%
Halichondria panicea 4 Occasional 41-60%
Littorina arcana 3 Occasional 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

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