Description of biotope or habitat type
Fabulina fabula and Magelona mirabilis with venerid bivalves and amphipods in infralittoral compacted fine muddy sand
Habitat (physical) 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|
|Depth Band||5-10 m, 10-20 m, 20-30 m|
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.
- 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
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 (Knitzer 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.
No temporal data available.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Nephtys cirrosa||1||Common||21-40 %|
|Nephtys hombergii||1||41-60 %|
|Spiophanes bombyx||15||Common||81-100 %|
|Magelona mirabilis||22||Common||81-100 %|
|Chaetozone setosa||13||Common||81-100 %|
|Lanice conchilega||19||Frequent||41-60 %|
|Pagurus bernhardus||4||Occasional||21-40 %|
|Liocarcinus depurator||13||Rare||41-60 %|
|Nucula nitidosa||3||Frequent||41-60 %|
|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 %|