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Marine Habitat Classification

Description of biotope or habitat type

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   Infralittoral mobile sand in variable salinity (estuaries)

Physical habitat description

Salinity Reduced (18-30ppt), Variable (18-35 ppt)
Wave exposure Moderately exposed, Sheltered, Very sheltered
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Medium to fine sand
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m
Other Features

Biotope origin

Derived using data from Various
Faunal group Epifauna

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.SSaVS.MoSaVS Infralittoral mobile sand 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.


Very mobile sand in areas of strong tidal currents and variable salinity. No stable community is able to develop within this extremely mobile and abrasive habitat. The fauna encountered in this habitat consists of epifaunal crustaceans or relatively low numbers of robust species, such as the isopod Eurydice pulchra or Mesopodopsis slabberi. The polychaete Capitella capitata may occur frequently in some areas. Other taxa such as the polychaetes Eteone spp. and Arenicola marina, the mysid Neomysis integer and the amphipods Bathyporeia spp. and Haustorius arenarius may also be washed in from adjacent communities. This biotope is found in tidal channels of estuaries and areas where water movement keeps silt and mud in suspension, and excludes even the more robust infauna. If oligochaetes, polychaetes and bivalves are present in any numbers within this habitat type then care must be taken to avoid the inclusion of juvenile or spat recruitment counts which may mask the presence of this biotope. This is particularly relevant as sampling usually occurs at slack water periods when settlement takes place.


No situation data available.

Temporal variation

No temporal data avaialble.

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
Eurydice pulchra 59 8 41-60%
Capitella capitata 24 Frequent 15 21-40%
Mesopodopsis slabberi 11 3 21-40%
Haustorius arenarius 2 1 1-20%

Similar biotopes or habitat types

SS.SSa.SSaVS.MoSaVS bears some similarity with SS.SSa.SSaVS.NintGam although the latter is found further up the estuary at the transition between brackish and fresh water. The freshwater community present in SS.SSa.SSaVS.NintGam will not be present here.

A similar biotope that occurs in fully saline conditions, it can be distinguished from SS.SSa.SSaVS.MoSaVS by the absence of species tolerant to reduced salinities.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SSa.SSaVS.MoSaVS Infralittoral mobile sand in variable salinity (estuaries)
2004 (04.05) SS.SSa.SSaVS.MoSaVS Infralittoral mobile sand in variable salinity (estuaries)
1997 (97.06) SS.IGS.EstGS.MobRS Sparse fauna in reduced salinity infralittoral mobile sand

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