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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.

   Nephtys hombergii and Macoma balthica in infralittoral sandy mud

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Sandy mud
Zone Circalittoral, Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m
Other Features Organically enriched

Biotope origin

Derived using data from Grab
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.

Distribution of habitat SS.SMu.ISaMu.NhomMac <I>Nephtys hombergii</I> and <I>Macoma balthica</I> in infralittoral sandy mud

  • 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.


Near-shore shallow sandy muds and muds, and sometimes mixed sediments, may be characterised by the presence of the polychaete Nephtys hombergii and the bivalve Macoma balthica. Abra alba, and Nucula nitidosa may also be important although they may not necessarily occur simultaneously or in high numbers. Other taxa include Spiophanes bombyx, Lagis koreni, and Echinocardium cordatum. In some areas Scoloplos armiger and Crangon crangon may also be present. The community appears to be quite stable (Dewarumez et al. 1992) and the substratum is typically rich in organic content. This community has been included in the 'Boreal Offshore Muddy Sand Association' of Jones (1950) and is also described by several other authors (Petersen 1918; Cabioch & Glaçon 1975). A similar community may occur in deep water in the Baltic (Thorson 1957). This biotope may occur in slightly reduced salinity estuarine conditions where Mya sp. may become a significant member of the community (Thorson 1957).


The community may occur in small patches or swathes in shallow waters parallel to the shore (Jones 1950; Cabioch & Glaçon 1975) or in shallow nearshore depressions or trenches where finer material collects e.g. off the Suffolk coast (IECS 1991). This biotope is known to occur in patches between Denmark and the western English Channel.

Temporal variation

Sites with SS.SMu.ISaMu.NhomMac may develop into Amphiura biotopes with time (E.I.S. Rees pers. comm. 1996).

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
Nephtys hombergii 37 Common 57 81-100%
Macoma balthica 20 Frequent 41 61-80%
Nucula nitidosa 18 Frequent 109 41-60%
Abra alba 6 13 41-60%
Echinocardium cordatum 3 16 21-40%
Lagis koreni 3 9 21-40%
Spiophanes bombyx 3 11 21-40%
Ophiura ophiura 2 9 21-40%
Magelona mirabilis 1 4 1-20%

Similar biotopes or habitat types

In deeper, less muddy areas SS.SMu.ISaMu.NhomMac may grade into SS.SSa.CMuSa.AalbNuc and it is possible that this biotope is part of the Abra dominated muddy sand biotopes.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMu.ISaMu.NhomMac Nephtys hombergii and Macoma balthica in infralittoral sandy mud
2004 (04.05) SS.SMu.ISaMu.NhomMac Nephtys hombergii and Macoma balthica in infralittoral sandy mud
1997 (97.06) SS.IMS.FaMS.MacAbr Macoma balthica and Abra alba in infralittoral muddy sand or mud
1996 (6.95) IMS.AbrLag

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