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Marine Habitat Classification

Description of biotope or habitat type

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   Philine aperta and Virgularia mirabilis in soft stable infralittoral mud

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Mud occasionally with small stones
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m
Other Features

Biotope origin

Derived using data from Various
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.IFiMu.PhiVir <I>Philine aperta</I> and <I>Virgularia mirabilis</I> in soft stable infralittoral 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.


Physically very stable muds, occasionally with small stones, with a high proportion of fine material (typically greater than 80 %) may contain the opisthobranch Philine aperta and the seapen Virgularia mirabilis. These muds typically occur in shallow water down to about 12-15 m where significant seasonal variation in temperature is presumed to occur. This habitat is restricted to the most sheltered basins in, for example, sea lochs. Although most records suggest full salinity conditions are prevalent, some sites may be subject to variable salinity. Philine aperta is the most characteristic species of this habitat, occurring in high densities at many sites, whilst Virgularia mirabilis, a species found more widely in muddy sediments, appears to reach its highest densities in this shallow mud but may not be present in all examples of this biotope. Other conspicuous species found in this shallow muddy habitat include Cerianthus lloydii, Pagurus bernhardus, Sagartiogeton spp. and Hydractinia echinata. Burrowing crustacean megafauna, characteristic of deeper mud, are rare or absent from this shallow sediment although Nephrops norvegicus may sometimes be recorded. This biotope has been primarily recorded on the basis of its epifauna and a few conspicuous infauna. Little data exists on the infaunal component of this biotope but it may include Nephtys spp., spionid polychaetes, Ampelisca spp. and the bivalves Nucula spp., Thyasira flexuosa, Kurtiella bidentata and Abra spp. In the south of Great Britain, the polychaete Sternaspis scutata is also characteristic of this biotope. This polychaete is rare in Great Britain (Sanderson 1996). Indeed, this southern variant of the biotope is very restricted in the UK to Portland Harbour but is known to occur further south in the Gulf of Gascony and the Mediterranean (Glemarec 1973; Dauvin et al. 1994).


No situation data available.

Temporal variation

It is possible that this biotope is a temporal variant of other SMu biotopes. The key species, Philine aperta, may be highly variable from year to year. The sediment may also be covered by a diatom film at certain times of the year.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Philine aperta 30 Common 81-100%
Pagurus bernhardus 11 Frequent 61-80%
Virgularia mirabilis 8 Frequent 41-60%
Cerianthus lloydii 7 Frequent 41-60%
Asterias rubens 5 Occasional 41-60%
Carcinus maenas 5 Occasional 41-60%
Hydractinia echinata 4 Occasional 41-60%
Liocarcinus depurator 3 Occasional 41-60%
Aequipecten opercularis 2 Rare 21-40%
Ascidiella aspersa 2 Occasional 21-40%
Cylista undata 2 Frequent 21-40%
Seraphsidae 2 Occasional 21-40%
Pomatoschistus 2 Occasional 21-40%
Amphiura filiformis 1 Frequent 21-40%
Saccharina latissima 1 Rare 21-40%
Cylista lacerata 1 Occasional 21-40%

Similar biotopes or habitat types

SS.SMu.CFiMu.SpnMeg is similar to SS.SMu.IFiMu.PhiVir, but occurs deeper, is more stable, and is characterised by burrowing megafauna and the sea pen Pennatula phosphorea.

SS.SMu.IFiMu.PhiVir displays some resemblance to SS.SMu.CFiMu.BlyrAchi, but the latter is characterised by a high abundance of ophiuroid species particularly Amphiura spp.

SS.SMu.IFiMu.PhiVir may be closely allied to SS.SMu.ISaMu.KurAbr, possibly sharing some of the infaunal elements of this biotope. However, SS.SMu.ISaMu.KurAbr is found on sandier sediments.

SS.SMu.ISaMu.CundAasp appears to be an disturbed version of SS.SMu.IFiMu.PhiVir lacking in P. aperta and V. mirabilis.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMu.IFiMu.PhiVir Philine aperta and Virgularia mirabilis in soft stable infralittoral mud
2004 (04.05) SS.SMu.IFiMu.PhiVir Philine aperta and Virgularia mirabilis in soft stable infralittoral mud
1997 (97.06) SS.IMU.MarMu.PhiVir Philine aperta and Virgularia mirabilis in soft stable infralittoral mud

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