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Marine Habitat Classification

Description of biotope or habitat type

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   Infralittoral surge gullies and caves

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Extremely exposed, Very exposed, Exposed, Moderately exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Bedrock (boulders, cobbles, pebbles or coarse sediment in gully floors)
Zone Infralittoral, Sublittoral fringe
Depth Band 0-5 m, 5-10 m, 10-20 m
Other Features Wave surged gullies or caves; vertical (and overhanging 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.FIR.SG Infralittoral surge gullies and 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'
  • 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.


Infralittoral rocky habitats subject to strong wave surge conditions, as found in surge gullies and shallow caves, and typically colonised by faunal communities of encrusting or cushion sponges, colonial ascidians, short turf-forming bryozoans, anthozoans, barnacles and, where there is sufficient light, red seaweeds. These features usually consist of vertical bedrock walls, occasionally with overhanging faces, and support communities which reflect the degree of wave surge they are subject to, and any scour from mobile substrata on the cave/gully floors. The larger cave and gully systems, such as found in Shetland, Orkney, the Western Isles and St Kilda, typically show a marked zonation from the entrance to the rear of the gully/cave as wave surge increases and light reduces. This is reflected in communities of anthozoans, ascidians, bryozoans and red seaweeds near the entrance, leading to sponge crust-dominated communities and finally barnacle and spirorbid worm communities in the most severe surge conditions. Gully/cave floors usually have mobile boulders, cobbles, pebbles or coarse sediment. The mobile nature of the gully/cave floors leads to communities of encrusting species, tolerant of scour and abrasion or fast summer-growing ephemeral species. The lower zone of the gully side walls are also often scoured, and typically colonised by coralline crusts and barnacles.


On open rocky coasts with moderate or greater wave action.

Temporal variation

Unknown, although winter storms likly to yield scouring on gully/cave walls; some ephemeral growth likely in calmer summer months.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Corallinaceae 7 Frequent 41-60%
Balanus crenatus 7 Frequent 41-60%
Clathrina coriacea 6 Frequent 41-60%
Cancer pagurus 5 Occasional 41-60%
Dendrodoa grossularia 5 Common 21-40%
Halichondria panicea 5 Frequent 41-60%
Cylista elegans 5 Occasional 41-60%
Urticina felina 4 Occasional 41-60%
Asterias rubens 3 Occasional 41-60%
Tubularia indivisa 3 Occasional 21-40%
Alcyonium digitatum 2 Occasional 21-40%
Botryllus schlosseri 2 Occasional 21-40%
Corynactis viridis 2 Frequent 21-40%
Didemnidae 2 Frequent 21-40%
Pachymatisma johnstonia 2 Occasional 21-40%
Spirobranchus triqueter 2 Occasional 21-40%
Porifera indet crusts 2 Occasional 21-40%
Bryozoa indet crusts 1 Frequent 21-40%
Calliostoma zizyphinum 1 Occasional 21-40%
Amphilectus fucorum 1 Occasional 21-40%
Henricia 1 Occasional 21-40%
Metridium senile 1 Frequent 21-40%
Myxilla incrustans 1 Occasional 21-40%
Polyclinum aurantium 1 Frequent 21-40%
Echinus esculentus 1 Occasional 21-40%

Similar biotopes or habitat types

Has a more prominant kelp and seaweed component.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) EIR.SG

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