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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.

   Sublittoral mixed sediment in variable salinity (estuaries)

Physical habitat description

Salinity 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 Muddy gravelly mixed sediment with stones and shells
Zone Infralittoral
Depth Band 0-5 m, 5-10 m
Other Features

Biotope origin

Derived using data from Various
Faunal group Epifauna/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.SMx.SMxVS Sublittoral mixed sediment in variable salinity (estuaries)

  • 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.


Shallow sublittoral mixed sediments in estuarine conditions, often with surface shells or stones, enabling the development of diverse epifaunal communities, e.g. Crepidula fornicata (SS.SMx.SMxVS.CreMed), as well as infaunal communities. This biotope complex is therefore often quite species rich, compared with purer sediments.


No situation data available.

Temporal variation

No temporal data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Crepidula fornicata 58 Frequent 61-80%
Aphelochaeta marioni 22 Common 61-80%
Cardiidae 20 21-40%
Cirripedia 7 Common 21-40%
Carcinus maenas 7 Occasional 21-40%
Mediomastus fragilis 6 Frequent 61-80%
Nephtys hombergii 6 Common 61-80%
Crepidula fornicata 5 Abundant 61-80%
Polydora ciliata 5 Abundant 41-60%
Chaetozone zetlandica 3 Common 21-40%
Tubificoides benedii 3 Common 41-60%
Exogone naidina 2 Frequent 41-60%
Melinna palmata 2 Common 41-60%
Scoloplos armiger 2 Common 41-60%
Sphaerosyllis 2 Frequent 21-40%
Abra alba 1 Common 21-40%
Abra nitida 1 Common 21-40%
Capitella capitata 1 Frequent 41-60%
Eteone longa 1 41-60%
Lepidonotus squamatus 1 41-60%
Tubificoides 1 Frequent 21-40%
Tubificoides swirencoides 1 Common 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMx.SMxVS Sublittoral mixed sediment in variable salinity (estuaries)
2004 (04.05) SS.SMx.SMxVS Sublittoral mixed sediment in variable salinity (estuaries)
1997 (97.06) SS.IMX.EstMx Estuarine sublittoral mixed sediments

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