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Marine Habitat Classification


Description of biotope or habitat type

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   Faunal crusts on wave-surged littoral cave walls


Habitat (physical) description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered
Tidal streams
Substratum Bedrock
Zone Eulittoral
Depth Band
Other Features Moist, dark caves; Vertical faces; Ceilings

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.FaCr Faunal crusts on wave-surged littoral cave walls

  • 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.

Description

The inner walls of caves, predominantly in the mid shore in wave-surged conditions dominated by barnacles Semibalanus balanoides, and Verruca stroemia, with patches of encrusting sponges such as Halichondria panicea and Grantia compressa and occasional patches of the mussel Mytilus edulis. Increased moisture allows a denser faunal population than ScrFa to develop within the cave. The limpet Patella vulgata and spirorbid tube-forming polychaetes can be present. The hydroid Dynamena pumila and anemones such as Metridium senile and Actinia equina may occur towards the lower reaches of the cave. Where a dense faunal turf of barnacles or bryozoan crusts covers the cave walls, the biotope can also extend to cover the ceiling and may be accompanied by the bryozoan Alcyonidium diaphanum. Variations of this biotope may occur in mid and lower shore scoured caves in south Wales the rock is dominated by dense Sabellaria alveolata. In south-west England the rock can be completely covered by the barnacle Balanus perforatus. There may be a variation in the species composition from cave to cave, depending on local conditions.

Situation

This biotope usually occurs above the sand/pebble scoured ScrFa zone and may extend to the ceilings of the caves.

Temporal variation

Unknown.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Grantia compressa 3 Occasional 21-40 %
Halichondria panicea 9 Occasional 41-60 %
Dynamena pumila 3 Frequent 21-40 %
Actinia equina 27 Frequent 61-80 %
Metridium senile 3 Occasional 21-40 %
Spirorbidae 7 Common 21-40 %
Verruca stroemia 6 Common 21-40 %
Semibalanus balanoides 11 Occasional 41-60 %
Balanus perforatus 4 Occasional 21-40 %
Patella vulgata 5 Rare 41-60 %
Mytilus edulis 4 Occasional 41-60 %
Bryozoa indet crusts 7 Common 21-40 %
Corallinaceae 4 Super abundant 21-40 %

Similar biotopes

Not applicable or unknown.

Photos

LR.FLR.CVOV.FaCr Faunal crusts on wave-surged littoral cave walls, Skrowa Skerry and cave, West Mainland. Eleanor Murray © JNCC
LR.FLR.CVOV.FaCr Faunal crusts on wave-surged littoral cave walls, Skrowa Skerry and cave, West Mainland. Eleanor Murray © JNCC

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