Description of biotope or habitat type
Infralittoral surge gullies and caves
Habitat (physical) 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.
- 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
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.
Unknown, although winter storms likly to yield scouring on gully/cave walls; some ephemeral growth likely in calmer summer months.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Clathrina coriacea||6||Frequent||41-60 %|
|Pachymatisma johnstonia||2||Occasional||21-40 %|
|Halichondria panicea||5||Frequent||41-60 %|
|Esperiopsis fucorum||1||Occasional||21-40 %|
|Myxilla incrustans||1||Occasional||21-40 %|
|Porifera indet crusts||2||Occasional||21-40 %|
|Tubularia indivisa||3||Occasional||21-40 %|
|Alcyonium digitatum||2||Occasional||21-40 %|
|Urticina felina||4||Occasional||41-60 %|
|Metridium senile||1||Frequent||21-40 %|
|Sagartia elegans||5||Occasional||41-60 %|
|Corynactis viridis||2||Frequent||21-40 %|
|Pomatoceros triqueter||2||Occasional||21-40 %|
|Balanus crenatus||7||Frequent||41-60 %|
|Cancer pagurus||5||Occasional||41-60 %|
|Calliostoma zizyphinum||1||Occasional||21-40 %|
|Bryozoa indet crusts||1||Frequent||21-40 %|
|Asterias rubens||3||Occasional||41-60 %|
|Echinus esculentus||1||Occasional||21-40 %|
|Polyclinum aurantium||1||Frequent||21-40 %|
|Dendrodoa grossularia||5||Common||21-40 %|
|Botryllus schlosseri||2||Occasional||21-40 %|