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Marine Habitat Classification

Description of biotope or habitat type

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   Atrina fragilis and echinoderms on circalittoral mud

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Very exposed, Exposed, Moderately exposed 
Tidal streams
Substratum Mud
Zone Circalittoral
Depth Band 100-150 m
Other Features

Biotope origin

Derived using data from Video/still
Faunal group Epifauna

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 SS.SMu.CFiMu.AtrEch <I> Atrina fragilis</I>  and echinoderms on circalittoral mud

  • 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.


Circalittoral mud and mixed sediments characterised by the epifaunal assemblage of fan mussel Atrina fragilis and brittle star Amphiura. The description of this biotope is based on epifauna recorded from Small Isles (northwest Scotland) but could be found in other areas with similar environmental conditions. The fauna was diverse with burrowing crustaceans, echinoderms, sea anemones, ascidians and bryozoans. The characteristic fauna includes anemone Sagaritogeton lacerates, Alcyonidium digitatum, Hydrozoa, serpulid worm Salmacina dysteri and Munida rugosa. The description of this biotope is based on video data so the characterising fauna include only those species with an epifaunal expression. This epifaunal biotope may be associated with infaunal biotopes described for similar environmental conditions.


No situation data available.

Temporal variation

No temporal data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) % of core records where taxon was recorded Relative frequency %
Amphiura 24 1-20% 20.8
Cylista lacerata 19 1-20% 12.6
Atrina fragilis 16 1-20% 11.6
Alcyonium digitatum 8 1-20% 4.7
Hydrozoa 7 1-20% 5.2
Salmacina dysteri 7 1-20% 3.8
Munida rugosa 4 1-20% 4.7
Caridea 4 1-20% 2.3
Nephrops norvegicus 3 1-20% 1.8
Nemertesia antennina 2 1-20% 1.8
Inachus 1 1-20% 1.8
Ophiothrix fragilis 1 1-20% 2.8
Paguridae 1 1-20% 2.3
Urticina 1 1-20% 1.3
Adamsia palliata 1 1-20% 2.3
Pagurus prideaux 1 1-20% 2.3
Leptometra celtica 1 1-20% 3.3

Similar biotopes or habitat types

Not applicable or unknown.

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