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Marine Habitat Classification

Description of biotope or habitat type

To understand more about what this page is describing, see How to use the classification. See also How to cite.

   Abra alba and Nucula nitidosa in circalittoral muddy sand or slightly mixed sediment

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Fine muddy sands occasionally with small gravel content
Zone Circalittoral
Depth Band 10-20 m, 20-30 m, 30-50 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.CMuSa.AalbNuc <I>Abra alba</I> and <I>Nucula nitidosa</I> in circalittoral muddy sand or slightly mixed sediment

  • 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.


Non-cohesive muddy sands or slightly shelly/gravelly muddy sand characterised by the bivalves Abra alba and Nucula nitidosa. Other important taxa include Nephtys spp., Chaetozone setosa and Spiophanes bombyx with Fabulina fabula also common in many areas. The echinoderms Ophiura albida and Asterias rubens may also be present. The epibiotic biotope EcorEns may overlap this biotope. This biotope is part of the Abra community defined by Thorson (1957) and the infralittoral etage described by Glemarec (1973).


No situation data available.

Temporal variation

Numbers of adult Abra alba can exceed 1000 m-

Characterising species

Taxon Typical abundance - SACFOR scale
Echiurus echiurus
Goniada maculata
Nephtys Common
Nephtys hombergii
Scoloplos armiger
Spiophanes bombyx Frequent
Chaetozone setosa Common
Scalibregma inflatum
Owenia fusiformis
Lanice conchilega
Lanice conchilega Occasional
Nucula nitidosa Frequent
Solenidae Super abundant
Fabulina fabula Common
Abra alba Abundant
Abra prismatica Frequent
Asterias rubens Occasional
Ophiura albida Abundant
Ophiura albida Rare

Similar biotopes or habitat types

In muddier sediments AalbNuc may grade into AfilMysAnit

At greater depths and in muddier sediments AalbNuc may grade into BlyrAchi

In muddier sediments AalbNuc may grade into LkorPpel

The two biotopes may be separated by the relative dominance of Abra alba and Nucula spp. in AalbNuc and the increased proportion of amphipods such as Bathyporeia spp.

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