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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.

   Circalittoral fine mud

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Moderately exposed, Sheltered, Very sheltered, Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Mud
Zone Circalittoral
Depth Band 10-20 m, 20-30 m, 30-50 m
Other Features

Biotope origin

Derived using data from Various
Faunal group Epifauna/infauna

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 Circalittoral fine 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.


Sublittoral muds, occurring below moderate depths of 15-20 m, either on the open coast or in marine inlets such as sea lochs. The seapens Virgularia mirabilis and Pennatula phosphorea are characteristic of this biotope complex together with the burrowing anemone Cerianthus lloydii and the ophiuroid Amphiura spp. The relatively stable conditions often lead to the establishment of communities of burrowing megafaunal species, such as Nephrops norvegicus.


No situation data available.

Temporal variation

No temporal data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Nephtys hystricis 43 41-60%
Amphiura chiajei 23 41-60%
Chaetozone setosa 21 41-60%
Nephrops norvegicus 20 Frequent 61-80%
Virgularia mirabilis 17 Frequent 61-80%
Cerianthus lloydii 10 Occasional 61-80%
Abra alba 7 21-40%
Asterias rubens 7 Occasional 41-60%
Liocarcinus depurator 6 Occasional 41-60%
Pennatula phosphorea 6 Frequent 41-60%
Pagurus bernhardus 5 Occasional 41-60%
Amphiura chiajei 3 Common 21-40%
Amphiura filiformis 3 Common 21-40%
Kurtiella bidentata 3 21-40%
Seraphsidae 2 Occasional 21-40%
Turritellinella tricarinata 2 Frequent 21-40%
Funiculina quadrangularis 2 Frequent 21-40%
Munida rugosa 1 Occasional 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMu.CFiMu Circalittoral fine mud
2004 (04.05) SS.SMu.CFiMu Circalittoral fine mud
1997 (97.06) SS.CMU Circalittoral muddy sands

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