Description of biotope or habitat type
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Spisula subtruncata and Nephtys hombergii in shallow muddy sand
Physical habitat 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. |
| Zone | Infralittoral |
| Depth Band | 0-5 m, 5-10 m, 10-20 m, 20-30 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.
- 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.
Description
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 to 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 SS.SSa.IMuSa.FfabMag and SS.SSa.CMuSa.AalbNuc with regard to sediment type (i.e. somewhat muddier than SS.SSa.IMuSa.FfabMag and less muddy than SS.SSa.CMuSa.AalbNuc) and may have species in common with both. As a result, other important species in this community include Abra alba, Fabulina fabula and Kurtiella bidentata. 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 to the status of this biotope.
Situation
No situation data available.
Temporal variation
In some areas this biotope may be a temporal variant or sub-biotope of SS.SSa.IMuSa.FfabMag and SS.SSa.CMuSa.AalbNuc rather than an established biotope in itself. For example SS.SSa.IMuSa.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. SS.SSa.CMuSa.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).
Characterising species
| 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 |
|---|---|---|---|---|
| Spisula subtruncata | 9 | Common | 189 | 81-100% |
| Nephtys hombergii | 7 | Common | 69 | 81-100% |
| Chaetozone setosa | 6 | Common | 44 | 61-80% |
| Fabulina fabula | 6 | Common | 31 | 81-100% |
| Kurtiella bidentata | 5 | Frequent | 184 | 81-100% |
| Spiophanes bombyx | 5 | Frequent | 60 | 81-100% |
| Acrocnida brachiata | 4 | Abundant | 141 | 81-100% |
| Glycera tridactyla | 4 | Common | 24 | 81-100% |
| Magelona alleni | 4 | Frequent | 20 | 61-80% |
| Sthenelais limicola | 4 | Abundant | 31 | 81-100% |
| Chamelea gallina | 2 | 9 | 61-80% | |
| Eteone longa | 2 | 6 | 61-80% | |
| Lagis koreni | 2 | Common | 645 | 41-60% |
| Mactra stultorum | 2 | Common | 31 | 61-80% |
| Nucula nitidosa | 2 | Common | 82 | 41-60% |
| Owenia fusiformis | 2 | Common | 23 | 61-80% |
| Pholoe inornata | 2 | Common | 43 | 61-80% |
| Abra alba | 13 | Common | 1629 | 81-100% |
| Cirratulidae | 1 | 6 | 61-80% | |
| Dosinia lupinus | 1 | Common | 10 | 61-80% |
| Malmgrenia lunulata | 1 | Common | 31 | 61-80% |
| Ophiura ophiura | 1 | Abundant | 11 | 41-60% |
| Pariambus typicus | 1 | Frequent | 33 | 41-60% |
Similar biotopes or habitat types
SS.SCS.ICS.MoeVen
SS.SSa.IMuSa.SsubNhom is found on slightly siltier and/or shelly sand and can be distinguished by the dominance of S. subtruncata.
SS.SSa.IMuSa.FfabMag
SS.SSa.IMuSa.SsubNhom is muddier than SS.SSa.IMuSa.FfabMag and can be distinguished by the dominance of Spisula.
SS.SSa.CMuSa.AalbNuc
SS.SSa.IMuSa.SsubNhom is less muddy than SS.SSa.CMuSa.AalbNuc and can be distinguished by the dominance of Spisula.Classification history of this biotope or habitat type
| Classification version | Code | Habitat name |
|---|---|---|
| 2015 (15.03) | SS.SSa.IMuSa.SsubNhom | Spisula subtruncata and Nephtys hombergii in shallow muddy sand |
| 2004 (04.05) | SS.SSa.IMuSa.SsubNhom | Spisula subtruncata and Nephtys hombergii in shallow muddy sand |
| 1997 (97.06) | SS.IGS.FaG.Sell | Spisula elliptica and venerid bivalves in infralittoral clean sand or shell gravel |