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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.

   Infralittoral mixed sediment

Physical habitat description

Salinity Full (30-35 ppt), 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 Mixed sediment
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m, 20-30 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.IMx 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.


Shallow mixed (heterogeneous) sediments in fully marine or near fully marine conditions, supporting various animal-dominated communities, with relatively low proportions of seaweeds. This habitat may include well mixed muddy gravelly sands or very poorly sorted mosaics of shell, cobbles and pebbles embedded in mud, sand or gravel. Due to the quite variable nature of the sediment type, a widely variable array of communities may be found, including those characterised by bivalves (SS.SMx.IMx.VcorAsquAps, SS.SMx.IMx.CreAsAn, and SS.SMx.IMx.Ost), polychaetes (SS.SMx.IMx.SpavSpAn) and file shells (SS.SMx.IMx.Lim). This has resulted in many species being described as characteristic of this biotope complex all contributing only a small percentage to the overall similarity (see below). This biotope complex may also include a newly proposed Chaetopterus biotope (Rees pers com.) recently found in the eastern English Channel. This biotope is characterised by an undescribed Chaetopterus sp. and small Lanice conchilega. Further sampling is need in order to assess and fully characterise this potential biotope. As a result, the Chaetopterus biotope has not been included in this revision. Infaunal data for this biotope complex are limited to that described in the biotope SS.SMx.IMx.VcorAsquAps and so are not representative of the infaunal component of the whole biotope complex.


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 20 Common 41-60%
Apseudopsis latreillii 7 Common 81-100%
Sabella pavonina 7 Common 21-40%
Nematoda 2 Frequent 61-80%
Buccinum undatum 5 Occasional 41-60%
Calyptraea chinensis 5 Common 81-100%
Mediomastus fragilis 5 Common 81-100%
Urticina felina 5 Occasional 41-60%
Aphelochaeta marioni 4 Common 61-80%
Alcyonium digitatum 3 Occasional 21-40%
Asterias rubens 3 Occasional 21-40%
Monocorophium sextonae 3 Common 61-80%
Lanice conchilega 3 Occasional 21-40%
Maera grossimana 3 Common 61-80%
Melinna palmata 3 Abundant 61-80%
Nemertea 3 Common 81-100%
Paguridae 3 Occasional 21-40%
Pagurus bernhardus 3 Occasional 21-40%
Styela clava 3 Occasional 21-40%
Syllidia armata 3 Common 61-80%
Chaetozone gibber 3 Common 41-60%
Amphicteis gunneri 2 Abundant 41-60%
Ascidiella aspersa 2 Frequent 21-40%
Caulleriella alata 2 Common 41-60%
Cerianthus lloydii 2 Occasional 21-40%
Amphilectus fucorum 2 Occasional 21-40%
Gammarella fucicola 2 Frequent 61-80%
Hydrallmania falcata 2 Occasional 21-40%
Limaria hians 2 Abundant 21-40%
Ophiothrix fragilis 2 Occasional 21-40%
Spirobranchus lamarcki 2 Common 41-60%
Tellimya ferruginosa 2 Frequent 61-80%
Tubificoides benedii 2 Common 61-80%
Venerupis corrugata 2 Abundant 81-100%
Tubificoides swirencoides 2 Common 41-60%
Abludomelita gladiosa 1 Frequent 41-60%
Phyllodoce mucosa 1 Common 61-80%
Calliostoma zizyphinum 1 Rare 21-40%
Cancer pagurus 1 Rare 21-40%
Carcinus maenas 1 Occasional 21-40%
Hyas araneus 1 Occasional 21-40%
Janira maculosa 1 Frequent 61-80%
Metaphoxus simplex 1 Common 41-60%
Necora puber 1 Occasional 21-40%
Notomastus latericeus 1 Frequent 61-80%
Spirobranchus triqueter 1 Occasional 21-40%
Sphaerosyllis hystrix 1 Frequent 41-60%
Ostrea edulis 1 Occasional 1-20%

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.IMx Infralittoral mixed sediment
2004 (04.05) SS.SMx.IMx Infralittoral mixed sediment
1997 (97.06) SS.IMX.FaMx Shallow mixed sediment faunal communities

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