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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.

   Thyasira spp. and Ennucula tenuis in circalittoral sandy mud

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed, Sheltered
Tidal streams Very weak (negligible)
Substratum Mud occasionally with scattered shells or gravel
Zone Circalittoral
Depth Band 20-30 m, 30-50 m, 50-100 m
Other Features

Biotope origin

Derived using data from Various
Faunal group 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.CSaMu.ThyEten <I>Thyasira</I> spp. and <I>Ennucula tenuis</I> in circalittoral sandy 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 cohesive sandy muds with small quantities of gravel, off sheltered or moderately exposed coasts may support populations characterised by Thyasira spp., in particular Thyasira flexuosa. Other characteristic taxa may include Ennucula tenuis, Goniada maculate and in some areas Rhodine gracilior. Kurtiella bidentata, Abra alba, Harpinia antennaria and Amphiura filiformis may be abundant in some examples of this biotope. Whilst moderately diverse, animal abundances are often low and it is possible that the biotope is the result of sedimentary disturbance e.g. from trawling and is possibly an impoverished version of SS.SMu.CSaMu.AfilEten. Collectively the biotopes SS.SMu.CSaMu.ThyEten, SS.SMu.CSaMu.AfilKurAnit, SS.SMu.CSaMu.AfilEten, SS.SMu.OMu.PjefThyAfil, and SS.SSa.OSa.OfusAfil, may form the Amphiura dominated components of the 'off-shore muddy sand association' described by other workers (Jones 1951; Thorson 1957; Mackie 1990) and the infralittoral etage described by Glemarec (1973).


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
Thyasira flexuosa 50 Occasional 81-100%
Abra alba 25 81-100%
Mya arenaria 25 81-100%
Thyasira flexuosa 12 Frequent 61-80%
Nemertea 7 61-80%
Goniada maculata 5 61-80%
Ennucula tenuis 4 Frequent 41-60%
Rhodine gracilior 4 Common 41-60%
Abra alba 3 41-60%
Amphiura filiformis 3 Abundant 41-60%
Galathowenia oculata 3 21-40%
Harpinia antennaria 3 Frequent 41-60%
Abyssoninoe hibernica 3 21-40%
Kurtiella bidentata 3 Frequent 41-60%
Terebellides stroemii 3 21-40%
Chaetozone setosa 2 41-60%
Cylichna cylindracea 2 41-60%
Diplocirrus glaucus 2 41-60%
Glycera unicornis 2 21-40%
Lucinoma borealis 2 41-60%
Nephtys 2 41-60%
Owenia fusiformis 2 Common 21-40%
Paraonidae 2 21-40%
Anobothrus gracilis 1 21-40%
Phaxas pellucidus 1 21-40%
Pholoe inornata 1 21-40%
Scalibregma inflatum 1 Common 21-40%
Spiophanes bombyx 1 21-40%
Spiophanes kroyeri 1 21-40%
Virgularia mirabilis 1 21-40%
Thyasira 1 Common 1-20%

Similar biotopes or habitat types

The current biotope may be distinguished from SS.SMu.CSaMu.AfilEten by the differing abundances of the characterising species Amphiura filiformis and Thyasira flexuosa in the two biotopes.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMu.CSaMu.ThyNten Thyasira spp. and Nuculoma tenuis in circalittoral sandy mud
2004 (04.05) SS.SMu.CSaMu.ThyNten Thyasira spp. and Nuculoma tenuis in circalittoral sandy mud

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