Skip to Content

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.

   Crepidula fornicata with ascidians and anemones on infralittoral coarse mixed sediment

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed
Tidal streams Moderately strong (1-3 kn)
Substratum Medium-coarse sands with gravel, shell, pebbles and cobbles
Zone Circalittoral
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.SMx.IMx.CreAsAn <I>Crepidula fornicata</I> with ascidians and anemones on infralittoral coarse 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.


Medium-coarse sands with gravel, shells, pebbles and cobbles on moderately exposed coasts may support populations of the slipper limpet Crepidula fornicata with ascidians and anemones. C. fornicata is common in this biotope though not as abundant as in the muddier estuarine biotope SS.SMx.SMxVS.CreMed to which this is related. Anemones such as Urticina felina and Alcyonium digitatum and ascidians such as Styela clava are typically found in this biotope. Bryozoans such as Flustra foliacea are also found along with polychaetes such as Lanice conchilega. Little information is available with regard to the infauna of this biotope but given the nature of the sediment the infaunal communities are liable to resemble those in biotopes from the SS.SCS habitat complex. As with SS.SMx.CMx.FluHyd this biotope could be considered a superficial or epibiotic overlay but more data is required to support this.


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 47 Common 81-100%
Paguridae 8 Frequent 41-60%
Styela clava 6 Occasional 41-60%
Urticina felina 5 Occasional 41-60%
Alcyonium digitatum 3 Occasional 21-40%
Flustra foliacea 3 Frequent 21-40%
Lanice conchilega 3 Occasional 21-40%
Calliostoma zizyphinum 2 Occasional 21-40%
Maja squinado 2 Rare 21-40%
Hydrozoa 1 21-40%
Anemonia viridis 1 Occasional 21-40%
Buccinum undatum 1 Occasional 21-40%
Foliose red algae 1 21-40%
Spirobranchus 1 Occasional 21-40%
Ostrea edulis 1 Rare 21-40%
Pomatoschistus 1 Occasional 21-40%

Similar biotopes or habitat types

SS.SMx.SMxVS.CreMed is found in less exposed marine areas, in particular estuaries, with a lower silt content and variable salinity.

SS.SMx.CMx.FluHyd is found in deeper water in slightly more exposed areas with a higher proportion of cobbles and pebbles and in slightly stronger currents.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMx.IMx.CreAsAn Crepidula fornicata with ascidians and anemones on infralittoral coarse mixed sediment
2004 (04.05) SS.SMx.IMx.CreAsAn Crepidula fornicata with ascidians and anemones on infralittoral coarse mixed sediment
1997 (97.06) LS.LMU.SMu.HedMac (part) Hediste diversicolor and Macoma balthica in sandy mud shores
1997 (97.06) SS.IMX.EstMx.CreAph (part) Crepidula fornicata and Aphelochaeta marioni in variable salinity infralittoral mixed sediment

Back to top