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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.

   Aphelochaeta spp. and Polydora spp. in variable salinity infralittoral mixed sediment

Physical habitat description

Salinity Reduced (18-30ppt), Variable (18-35 ppt), Low (<18ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Sandy gravelly muddy mixed sediment
Zone Infralittoral
Depth Band 0-5 m, 5-10 m
Other Features

Biotope origin

Derived using data from Various
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.SMx.SMxVS.AphPol <I>Aphelochaeta</I> spp. and <I>Polydora</I> spp. in variable salinity infralittoral 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.


In sheltered muddy mixed sediments in estuaries or marine inlets with variable or reduced/low salinity communities characterised by Aphelochaeta marioni and Polydora ciliata may be present. Other important taxa may include the polychaetes Nephtys hombergii, Chaetozone zetlandica and Melinna palmata, tubificid oligochaetes and bivalves such as Abra nitida. Conspicuous epifauna may include members of the bivalve family Cardiidae (cockles) and the slipper limpet Crepidula fornicata. This biotope is often found in polyhaline waters.


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
Cardiidae 50 41-60%
Aphelochaeta marioni 33 Common 81-100%
Crepidula fornicata 27 41-60%
Cirripedia 14 Common 21-40%
Polydora ciliata 10 Abundant 61-80%
Nephtys hombergii 8 Common 61-80%
Chaetozone zetlandica 5 Common 41-60%
Polychaeta 4 1-20%
Melinna palmata 4 Common 21-40%
Abra nitida 3 Common 41-60%
Carcinus maenas 3 1-20%
Tubificoides 3 Frequent 41-60%
Eteone longa 2 Frequent 41-60%
Harmothoe 2 Common 41-60%
Mediomastus fragilis 2 41-60%
Streblospio shrubsolii 2 21-40%
Tubifex 2 Frequent 21-40%
Cerastoderma edule 1 41-60%
Ampharete 1 Common 21-40%
Capitella capitata 1 Occasional 41-60%
Hediste diversicolor 1 41-60%
Lanice conchilega 1 Frequent 21-40%
Pygospio elegans 1 Frequent 21-40%
Scoloplos armiger 1 21-40%

Similar biotopes or habitat types

In areas of mixed sediment, where A. marioni occurs in high numbers, it may be difficult to separate SS.SMu.SMuVS.AphTubi from SS.SMx.SMxVS.AphPol, requiring classification on sediment characteristics and associated species in addition to the abundance of A. marioni.

SS.SMu.SMuVS.PolCvol is similar to SS.SMx.SMxVS.AphPol but occurs in muddier estuarine conditions.

SS.SMx.SMxVS.CreMed may be distinguished from SS.SMx.SMxVS.AphPol by the abundance of C. fornicata and its sediment characteristics. SS.SMx.SMxVS.AphPol may also be found in reduced salinity conditions.

As salinity increases SS.SMx.SMxVS.AphPol may grade into SS.SMu.ISaMu.MelMagThy with those species characteristic of the latter increasing in abundance.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMx.SMxVS.AphPol Aphelochaeta spp. and Polydora spp. in variable salinity infralittoral mixed sediment
2004 (04.05) SS.SMx.SMxVS.AphPol Aphelochaeta spp. and Polydora spp. in variable salinity infralittoral mixed sediment
1997 (97.06) SS.IMX.EstMx.PolMtru Polydora ciliata, Mya truncata and solitary ascidians in variable salinity infralittoral mixed sediment

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