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.

   Cerianthus lloydii with Nemertesia spp. and other hydroids in circalittoral muddy mixed sediment

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed, Sheltered, Very sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Sandy muddy gravel with surficial cobbles, pebbles and shells
Zone Infralittoral - lower, Circalittoral
Depth Band 10-20 m, 20-30 m
Other Features

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.CMx.ClloMx.Nem <I>Cerianthus lloydii</I> with <I>Nemertesia</I> spp. and other hydroids in circalittoral muddy 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 sandy gravel with appreciable quantities of surficial cobbles, pebbles and shells a community similar to ClloMx may develop with frequent Cerianthus lloydii and other burrowing anemones. However, the pebbles and cobbles embedded in the sediment are colonised by hydroids and in particular Nemertesia antennina and N. ramosa. Other hydroids may include Kirchenpaueria pinnata and Halecium halecinum whilst ascidians such as Ascidiella aspersa or Corella parallelogramma may also be present locally. Pecten maximus and Pomatoceros triqueter may also be frequent in certain areas.


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
Halecium halecinum 1 Occasional 21-40 %
Nemertesia antennina 8 Occasional 61-80 %
Nemertesia ramosa 8 Occasional 41-60 %
Cerianthus lloydii 21 Frequent 81-100 %
Chaetopterus variopedatus 1 Occasional 21-40 %
Terebellidae 1 Occasional 21-40 %
Lanice conchilega 3 Occasional 21-40 %
Pomatoceros triqueter 3 Frequent 41-60 %
Pagurus bernhardus 5 Occasional 41-60 %
Liocarcinus depurator 4 Occasional 41-60 %
Turritella communis 1 Frequent 21-40 %
Pecten maximus 5 Occasional 41-60 %
Aequipecten opercularis 1 Occasional 21-40 %
Asterias rubens 8 Occasional 61-80 %
Ophiura albida 3 Occasional 21-40 %
Echinus esculentus 3 Occasional 41-60 %

Similar biotopes or habitat types

In areas of similar sediment but with fewer surface pebbles, cobbles and shells there are fewer sites of attachment for hydroids such as Nemertesia and ClloMx.Nem is replaced by SMX.ClloMx

Back to top