Description of biotope or habitat type
Spisula subtruncata and Nephtys hombergii in shallow muddy sand
Habitat (physical) description
|Salinity||Full (30-35 ppt)|
|Wave exposure||Moderately exposed, Sheltered|
|Tidal streams||Moderately strong (1-3 kn), Weak (>1 kn)|
|Substratum||Muddy sand occasionally with surface shell fragments.|
|Depth Band||0-5 m, 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 shallow non-cohesive muddy sands, in fully marine conditions, a community characterised by the bivalve Spisula subtruncata and the polychaete Nephtys hombergii may occur. The sediments in which this community is found may vary with regard silt content but they generally have less than 20% silt/clay and in some areas may contain a degree of shell debris. This biotope falls somewhere between SSA.FfabMag and SSA.AalbNuc with regard sediment type (i.e. somewhat muddier than SSA.FfabMag and less muddy than SSA.AalbNuc) and may have species in common with both. As a result, other important species in this community include Abra alba, Fabulina fabula spp. and Mysella bidentata spp. In addition, Diastylis rathkei/typical, Philine aperta (in muddier sediments), Ampelisca spp., Ophiura albida, Phaxas pellucidus and occasionally Bathyporeia spp, may also be important, although this is not clear from the data available. In areas of slightly coarser, less muddy sediment S. solida or S. elliptica may appear occasionally in this biotope. Abundances of Spisula subtruncata in this biotope are often very high and distinguish it from other closely related biotopes. Extensive areas of this community to the north east of the Dogger Bank were recorded in the 1950s, but these seem to have declined since then (Kroncke 1990). More information is required with regard the status of this biotope.
No situation data available.
In some areas this biotope may be a temporal variant or sub-biotope of SSA.FfabMag and SSA.AalbNuc rather than an established biotope in itself. For example SSA.SsubNhom has been recorded in Red Wharf Bay and Conwy Bay where it appears to be short term variant of other more established biotopes (e.g. SSA.AalbNuc) and appears to have only intermittent occurrence in single age cohort patches possibly due to predation in some areas (e.g. Red Wharf Bay) by the common Scoter Melanitta nigra (E.I.S. Rees pers. comm. 2002).
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||Typical abundance - (count per m2)||% of core records where taxon was recorded|
|Harmothoe lunulata||1||Common||31||61-80 %|
|Pholoe inornata||2||Common||43||61-80 %|
|Sthenelais limicola||4||Abundant||31||81-100 %|
|Eteone longa||2||6||61-80 %|
|Glycera tridactyla||4||Common||24||81-100 %|
|Nephtys hombergii||7||Common||69||81-100 %|
|Spiophanes bombyx||5||Frequent||60||81-100 %|
|Magelona alleni||4||Frequent||20||61-80 %|
|Chaetozone setosa||6||Common||44||61-80 %|
|Owenia fusiformis||2||Common||23||61-80 %|
|Lagis koreni||2||Common||645||41-60 %|
|Pariambus typicus||1||Frequent||33||41-60 %|
|Nucula nitidosa||2||Common||82||41-60 %|
|Mysella bidentata||5||Frequent||184||81-100 %|
|Mactra stultorum||2||Common||31||61-80 %|
|Spisula subtruncata||9||Common||189||81-100 %|
|Fabulina fabula||6||Common||31||81-100 %|
|Abra alba||13||Common||1629||81-100 %|
|Chamelea gallina||2||9||61-80 %|
|Dosinia lupinus||1||Common||10||61-80 %|
|Amphiura brachiata||4||Abundant||141||81-100 %|
|Ophiura ophiura||1||Abundant||11||41-60 %|