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Marine Habitat Classification


Description of biotope or habitat type

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   Brittlestars on faunal and algal encrusted exposed to moderately wave-exposed circalittoral rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Bedrock, boulders, cobbles, pebbles, gravel
Zone Circalittoral
Depth Band 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.MCR.EcCr.FaAlCr.Bri Brittlestars on faunal and algal encrusted exposed to moderately wave-exposed 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 is typically found on the upper faces of exposed and moderately wave-exposed circalittoral bedrock, boulders and cobbles subject to moderately strong to weak tidal streams. It is characterised by high densities of brittlestars (predominantly Ophiothrix fragilis, Ophiocomina nigra and Ophiura albida). In fact, they may form such dense beds that the seabed underneath may not be visible. The rocky substratum is usually colonised by species such as encrusting red algae and the white, calcareous tubes of the polychaete Pomatoceros triqueter. Only robust hydroids such as Abietinaria abietina, Alcyonium digitatum and bryozoan crusts such as Parasmittina trispinosa are able to tolerate the significant smothering effect from the dense mat of brittlestars. Other species typically seen include Echinus esculentus, Asterias rubens, Pagurus bernhardus, Anapagurus hyndmanni, Gibbula cineraria, Urticina felina, Pododesmus patelliformis and Ciona intestinalis.

Situation

Shallower than the FaAlCr.Bri variant, kelp park and forest may be found with species such as Laminaria saccharina and Laminaria hyperborea.

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
Abietinaria abietina 2 Occasional 41-60 %
Alcyonium digitatum 6 Occasional 81-100 %
Urticina felina 3 Occasional 41-60 %
Pomatoceros triqueter 12 Frequent 61-80 %
Anapagurus hyndmanni 1 Frequent 21-40 %
Pagurus bernhardus 3 Occasional 61-80 %
Gibbula cineraria 3 Occasional 41-60 %
Pododesmus patelliformis 1 Occasional 21-40 %
Parasmittina trispinosa 1 Occasional 21-40 %
Asterias rubens 7 Occasional 81-100 %
Ophiothrix fragilis 16 Abundant 81-100 %
Ophiocomina nigra 7 Common 61-80 %
Ophiura albida 2 Frequent 41-60 %
Echinus esculentus 10 Frequent 81-100 %
Ciona intestinalis 2 Occasional 41-60 %
Corallinaceae 8 Common 61-80 %

Similar biotopes

CR.LCR.BrAs.AmenCio.Bri
This biotope occurs on more wave-sheltered mixed substratum, subject to moderately strong to very weak tidal streams. It tends to have a similar species diversity to FaAlCr.Bri, but robust hydroids such as A. abietina have been replaced by more delicate species such as Kirchenpaueria pinnata. Occasionally, bryozoan crusts may be present in FaAlCr.Bri as well.

CR.MCR.EcCr.CarSp.Bri
This biotope is found on much more exposed bedrock or boulders. A diverse range of species is associated with this biotope including numerous hydroids, bryozoans and echinoderms.

Biotope history

Classification Habitat code
97.06 CR.MCR.Bri.Oph
97.06 CR.MCR.Bri.Oph.Oacu

Photos

CR.MCR.ECCR.FaAlCr.Bri Brittlestars on faunal and algal encrusted exposed to moderately wave-exposed circalittoral rock, SE Seaforth Island, Loch Seaforth, Lewis. Sue Hiscock © JNCC
CR.MCR.ECCR.FaAlCr.Bri Brittlestars on faunal and algal encrusted exposed to moderately wave-exposed circalittoral rock, SE Seaforth Island, Loch Seaforth, Lewis. Sue Hiscock © JNCC

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