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Marine Habitat Classification


Description of biotope or habitat type

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   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.
Zone Infralittoral
Depth Band 0-5 m, 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.SsubNhom <I>Spisula subtruncata</I> and <I>Nephtys hombergii</I> in shallow 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.

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 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.

Situation

No situation data available.

Temporal variation

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).

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
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 %
Cirratulidae 1 6 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 %

Similar biotopes

SS.SCS.ICS.MoeVen
SsubNhom is found on slightly siltier and/or shelly sand and can be distinguished by the dominance of S. subtruncata.

SS.SSa.IMuSa.FfabMag
SsubNhom is muddier than FfabMag and can be distinguished by the dominance of Spisula

SS.SSa.CMuSa.AalbNuc
SsubNhom is less muddy than AalbNuc and can be distinguished by the dominance of Spisula.


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