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Marine Habitat Classification

Description of biotope or habitat type

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   Antedon spp., solitary ascidians and fine hydroids on sheltered circalittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Bedrock, boulders
Zone Circalittoral
Depth Band 5-10 m, 10-20 m, 20-30 m, 30-50 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 CR.LCR.BrAs.AntAsH <I>Antedon</I> spp., solitary ascidians and fine hydroids on sheltered circalittoral 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.


This biotope is typically found on silty boulder or rock slopes, in the sheltered parts of sealochs, subject to weak or very weak tidal currents. The seabed consists of smooth, silty bedrock or boulders, often as outcrops on mixed muddy sediment. There are often small vertical faces on the sides of rock ridges, and at few sites, there may be more extensive steep or vertical bedrock. In sharp contrast to the barren, grazed appearance of AmenCio.Ant, the species composition of AntAsH is quite diverse, although no one phyla dominates. A wide range of encrusting species may be found, including the brachiopod Novocrania anomala, the saddle oyster Pododesmus patelliformis, encrusting red algae and polychaetes (Spirobranchus triqueter and Protula tubularia). Other conspicuous species include crinoids on the tops of boulders (Antedon bifida, commoner in shallower water and Antedon petasus, commoner in deeper water), scattered solitary and colonial ascidians (Ascidia mentula, Ascidia virginea, Corella parallelogramma, Clavelina lepadiformis and Ciona intestinalis) and tufts of fine hydroids (Kirchenpaueria pinnata, Nemertesia antennina, Obelia dichotoma and Halceum halecinum). The cup coral Caryophyllia smithii and the crustose bryozoan Parasmittina trispinosa are all typically present, as are a wide range of echinoderms, including the sea urchin Echinus esculentus, the starfish Asterias rubens and Crossaster papposus, and the brittlestars Ophiothrix fragilis and Ophiura albida. Other species recorded are the squat lobster Munida rugosa, the hermit crab Pagurus bernhardus and the chiton Tonicella marmorea.


The range of biotopes shallower and deeper than AntAsH is typical of a sheltered sealoch. Silted kelp biotopes (e.g. LhypLsac, Lsac) are typically found shallower than AntAsH in the infralittoral zone. Deeper than AntAsH, the boulder slope typically grades into a muddy slope or plain (CMU or CMX), along with fauna commonly associated with soft-sediments (e.g. seapens and the mud snail Turritella).

Temporal variation

Not known.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Spirobranchus triqueter 7 Frequent 81-100%
Corallinaceae 6 Common 61-80%
Ascidia mentula 6 Occasional 81-100%
Asterias rubens 5 Occasional 81-100%
Munida rugosa 5 Frequent 81-100%
Echinus esculentus 5 Occasional 81-100%
Ciona intestinalis 4 Frequent 61-80%
Corella parallelogramma 4 Occasional 81-100%
Kirchenpaueria pinnata 3 Frequent 61-80%
Novocrania anomala 3 Frequent 61-80%
Ophiothrix fragilis 3 Occasional 61-80%
Pagurus bernhardus 3 Occasional 61-80%
Antedon bifida 2 Occasional 61-80%
Antedon petasus 2 Occasional 61-80%
Ascidia virginea 2 Occasional 61-80%
Caryophyllia smithii 2 Occasional 61-80%
Clavelina lepadiformis 2 Occasional 41-60%
Halecium halecinum 2 Occasional 41-60%
Ophiura albida 2 Occasional 61-80%
Protula tubularia 2 Occasional 61-80%
Crossaster papposus 1 Rare 61-80%
Nemertesia ramosa 1 Occasional 41-60%
Obelia dichotoma 1 Occasional 41-60%
Parasmittina trispinosa 1 Occasional 41-60%
Pododesmus patelliformis 1 Occasional 41-60%
Tonicella marmorea 1 Occasional 41-60%

Similar biotopes or habitat types

Not applicable or unknown.


CR.LCR.BRAS.AntAsH Antedon spp., solitary ascidians and fine hydroids on sheltered circalittoral rock, NW Sligneach Mor, Loch Sunart. Dale Rostron© JNCC
CR.LCR.BRAS.AntAsH Antedon spp., solitary ascidians and fine hydroids on sheltered circalittoral rock, NW Sligneach Mor, Loch Sunart. Dale Rostron© JNCC

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