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Marine Habitat Classification

Description of biotope or habitat type

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   Fabulina fabula and Magelona mirabilis with venerid bivalves and amphipods in infralittoral compacted fine muddy sand

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Medium to very fine sand with some silt
Zone Infralittoral
Depth Band 5-10 m, 10-20 m, 20-30 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 SS.SSa.IMuSa.FfabMag <I>Fabulina fabula</I> and <I>Magelona mirabilis</I> with venerid bivalves and amphipods in infralittoral compacted fine muddy sand

  • 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.


In stable, fine, compacted sands and slightly muddy sands in the infralittoral and littoral fringe, communities occur that are dominated by venerid bivalves such as Chamelea gallina. This biotope may be characterised by a prevalence of Fabulina fabula and Magelona mirabilis or other species of Magelona (e.g. M. filiformis). Other taxa, including the amphipod Bathyporeia spp. and polychaetes such as Chaetozone setosa, Spiophanes bombyx and Nephtys spp. are also commonly recorded. In some areas the bivalve Spisula elliptica may also occur in this biotope in low numbers. The community is relatively stable in its species composition, however, numbers of Magelona and F. Fabulina tend to fluctuate. Around the Scilly Isles numbers of F. fabulina in this biotope are uncommonly low whilst these taxa are often found in higher abundances in muddier communities (presumably due to the higher organic content). Consequently it may be better to revise this biotope on the basis of less ubiquitous taxa such as key amphipod species (E.I.S. Rees pers. comm. 2002) although more data is required to test this. FfabMag and MoeVen are collectively considered to be the 'shallow Venus community' or 'boreal off-shore sand association' of previous workers (see Petersen 1918; Jones 1950; Thorson 1957). These communities have been shown to correlate well with particular levels of current induced 'bed-stress' (Warwick & Uncles 1980). The 'Arctic Venus Community' and 'Mediterranean Venus Community' described to the north and south of the UK (Thorson 1957) probably occur in the same habitat and appears to be the same biotope described as the Ophelia borealis community in northern France and the central North Sea (Knitzer et al. 1992). Sites with this biotope may undergo transitions in community composition. The epibiotic biotopes EcorEns and AreISa may also overlay this biotope in some areas.


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
Polychaeta 8 Occasional 21-40 %
Nephtys 6 Common 61-80 %
Nephtys cirrosa 1 Common 21-40 %
Nephtys hombergii 1 41-60 %
Spio 1 Frequent 41-60 %
Spiophanes bombyx 15 Common 81-100 %
Magelona mirabilis 22 Common 81-100 %
Cirratulidae 2 Common 41-60 %
Chaetozone setosa 13 Common 81-100 %
Lanice conchilega 19 Frequent 41-60 %
Bathyporeia 2 Frequent 21-40 %
Pagurus bernhardus 4 Occasional 21-40 %
Liocarcinus depurator 13 Rare 41-60 %
Nucula nitidosa 3 Frequent 41-60 %
Ensis 8 Frequent 21-40 %
Phaxas pellucidus 2 Common 41-60 %
Fabulina fabula 17 Common 81-100 %
Abra alba 1 21-40 %
Chamelea gallina 3 Common 41-60 %
Asterias rubens 3 Rare 21-40 %
Echinocardium cordatum 34 Frequent 61-80 %
Pomatoschistus minutus 4 Frequent 21-40 %
Pleuronectidae 2 1-20 %

Similar biotopes or habitat types

FfabMag forms part of a continuum of communities found along the depth and sand/silt gradients with an increase in silt/clay leading to the development of AalbNuc in deeper water.

As sediment disturbance increases and the finer silt fraction is unable to sediment out of the water column FfabMag may grade into the sandy biotope NcirBat.

MoeVen is found in slightly coarser sediments. FfabMag differs from MoeVen because of the prevalence of the brittle-shelled F. fabula over the more robust Moerella and Spisula, and because it occurs in generally finer, more compact sands.

In very shallow water with a greater mud fraction this biotope may give way to the sandy mud biotope NhomMac.

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