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Marine Habitat Classification


Description of biotope or habitat type

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   Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock


Habitat (physical) 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 Often on vertical 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 CR.LCR.BrAs.AmenCio.Ant Solitary ascidians, including <I>Ascidia mentula</I> and <I>Ciona intestinalis</I>, with <I>Antedon</I> spp. on wave-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.

Description

This variant occurs on circalittoral bedrock or boulder slopes in generally wave-sheltered conditions (often in sea lochs) with little tidal flow. It is frequently found on vertical or steeply-sloping rock. Apart from the large ascidians, Ascidia mentula and Ciona intestinalis, the rock surface usually has a rather sparse appearance. Scyphistomae larvae are often present on any vertical surfaces. Grazing by the sea urchin Echinus esculentus leaves only encrusting red algae (giving the bedrock/boulder substratum a pink appearance), cup corals Caryophyllia smithii and the keelworm Pomatoceros triqueter. There may be a few hydroid species present, such as Nemertesia spp. and Kirchenpaueria pinnata, occasional Alcyonium digitatum and occasional Metridium senile. Barnacles Balanus spp. and the colonial ascidian Clavelina lepadiformis also occasionally occur. At some sites, echinoderms such as the crinoid Antedon spp., the starfish Crossaster papposus and Asterias rubens and the brittlestar Ophiothrix fragilis (in low densities) may be found. The squat lobster Munida rugosa is likely to be found in crevices, under boulders, and the hermit crab Pagurus bernhardus may be observed moving around the rock surface. The brachiopod Neocrania anomala is frequently observed (especially where this biotope occurs shallower than NeoPro for example). The saddle oyster Pododesmus patelliformis may occasionally be seen attached to the rock/boulder face.

Situation

This biotope is typical of one found in sheltered sealochs. On slightly more wave and tide exposed sites, a transition to the more diverse AntAsH biotope will occur. Below AmenCio.Ant, you may find the NeoPro biotope (especially situated on the sills of sealochs).

Temporal variation

The abundance of C. intestinalis tends to fluctuate seasonally, so it may appear absent at a site at one time of year and then be present at other times, altering the visual appearance of the biotope. Other solitary ascidian species such as A. mentula and Ascidiella aspersa tend to be longer-lived (approximately 7 years and 3 years respectively).

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Kirchenpaueria pinnata 1 Occasional 21-40 %
Nemertesia antennina 1 Occasional 21-40 %
Alcyonium digitatum 2 Occasional 21-40 %
Metridium senile 2 Occasional 21-40 %
Caryophyllia smithii 5 Occasional 41-60 %
Pomatoceros triqueter 10 Frequent 61-80 %
Balanus crenatus 1 Occasional 21-40 %
Pagurus bernhardus 2 Occasional 21-40 %
Munida rugosa 5 Occasional 41-60 %
Pododesmus patelliformis 1 Frequent 21-40 %
Neocrania anomala 1 Frequent 21-40 %
Antedon bifida 4 Occasional 41-60 %
Antedon petasus 2 Frequent 21-40 %
Crossaster papposus 2 Occasional 21-40 %
Asterias rubens 6 Occasional 41-60 %
Ophiothrix fragilis 2 Occasional 21-40 %
Echinus esculentus 12 Occasional 81-100 %
Clavelina lepadiformis 2 Occasional 41-60 %
Ciona intestinalis 9 Frequent 61-80 %
Ascidia mentula 6 Frequent 41-60 %
Corallinaceae 7 Common 41-60 %

Similar biotopes

CR.MCR.EcCr.FaAlCr
This biotope is found on more wave-exposed sites subject to moderately strong to weak tidal streams. They occur on similar substratum and appear similar due to their characteristically barren nature. FaAlCr tends to have a higher abundance of A. digitatum than AmenCio.Ant, while the latter instead has a diverse range of solitary ascidians. AmenCio.Ant also tends to appear more silty than FaAlCr.

CR.LCR.BrAs.AntAsH
This biotope occurs at similar depths and conditions as AmenCio.Ant. It tends to be more species rich, with a diverse range of hydroids and echinoderms. Other species such as Chaetopterus variopedatus and Sabella pavonina may also be present occasionally.

Photos

CR.LCR.BRAS.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock, Skerry west of Sgeir Fhada, Loch Sunart. Christine Howson © JNCC
CR.LCR.BRAS.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock, Skerry west of Sgeir Fhada, Loch Sunart. Christine Howson © JNCC
CR.LCR.BRAS.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock, Skerry west of Sgeir Fhada, Loch Sunart. Christine Howson © JNCC
CR.LCR.BRAS.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock, Skerry west of Sgeir Fhada, Loch Sunart. Christine Howson © JNCC
CR.LCR.BRAS.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock, Unspecified location. ANON © JNCC
CR.LCR.BRAS.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock, Unspecified location. ANON © JNCC

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