Skip to Content

Marine Habitat Classification


Description of biotope or habitat type

To understand more about what this page is describing, see How to use the classification. See also How to cite.

   Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed, Sheltered, Very sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Bedrock, boulders, cobbles, gravel, sand, mud
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.AmenCio.Bri Dense brittlestars with sparse <I>Ascidia mentula</I> and <I>Ciona intestinalis</I> on sheltered circalittoral mixed substrata

  • 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 biotope is typically found on wave-sheltered sites (although it may be found in wave-exposed through to extremely wave-sheltered conditions), on circalittoral mixed substrata (Bedrock, boulders, cobbles, pebbles and gravel), subject to moderately strong to weak tidal streams. This biotope often has a silty appearance in parallel with AmenCio.Ant but is characterised by a dense carpet of brittlestars (Ophiothrix fragilis, Ophiocomina nigra and to a lesser extent Ophiura albida) which virtually cover the seabed. Where the underlying substratum is visible, pink coralline crusts and the white calcareous tubes of the keelworm Pomatoceros triqueter are often observed. Hydroids and bryozoans are scarce, perhaps partly due to the smothering effect of the brittlestars and possibly due to the grazing pressure of the sea urchin Echinus esculentus which is occasionally recorded. Other echinoderms present include Asterias rubens and Crossaster papposus. The solitary ascidian Ciona intestinalis may be seen attached to isolated rocks and boulders, whilst on the tops and sides of larger boulders, dead man's fingers Alcyonium digitatum may be recorded. The hermit crab Pagurus bernhardus is often recorded, whilst under boulders and in crevices the claws belonging to the long-clawed squat lobster Munida rugosa may be seen.

Situation

AmenCio.Bri is found in predominantly sheltered areas, so in the infralittoral zone above, kelp forest formed by dense Laminaria saccharina and cape-form Laminaria hyperborea are frequently recorded. A dense understorey of red algae is also present.

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
Alcyonium digitatum 1 Occasional 41-60 %
Pomatoceros triqueter 3 Frequent 41-60 %
Pagurus bernhardus 4 Occasional 41-60 %
Munida rugosa 1 Occasional 21-40 %
Crossaster papposus 2 Occasional 41-60 %
Asterias rubens 4 Occasional 61-80 %
Ophiothrix fragilis 27 Abundant 81-100 %
Ophiocomina nigra 21 Common 81-100 %
Ophiura albida 4 Frequent 41-60 %
Echinus esculentus 6 Occasional 61-80 %
Ciona intestinalis 1 Occasional 21-40 %
Corallinaceae 7 Frequent 41-60 %

Similar biotopes

CR.MCR.EcCr.FaAlCr.Bri
This biotope occurs on more wave-exposed mixed substratum, subject to varying amounts of tide. Tends to have similar species diversity as AmenCio.Bri, but delicate hydroids have been replaced by more robust species such as Abietinaria abietina. Occasionally, bryozoan crusts may be present in FaAlCr.Bri.

Photos

CR.LCR.BRAS.AmenCio.Bri Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata, Reef N of Samalaman Island, Sound of Arisaig. David Mills © JNCC
CR.LCR.BRAS.AmenCio.Bri Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata, Reef N of Samalaman Island, Sound of Arisaig. David Mills © JNCC
CR.LCR.BRAS.AmenCio.Bri Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata, Reef N of Samalaman island, Sound of Arisaig. Dave Mills © JNCC
CR.LCR.BRAS.AmenCio.Bri Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata, Reef N of Samalaman island, Sound of Arisaig. Dave Mills © JNCC

Back to top