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.

   Phymatolithon calcareum maerl beds with Neopentadactyla mixta and other echinoderms in deeper infralittoral clean gravel or coarse sand

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Maerl gravel; coarse sand
Zone Circalittoral - upper, Infralittoral - lower
Depth Band 5-10 m, 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.SMp.Mrl.Pcal.Nmix <I>Phymatolithon calcareum</I> maerl beds with <I>Neopentadactyla mixta</I> and other echinoderms in deeper infralittoral clean gravel or coarse sand

  • 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.


Lower infralittoral maerl beds characterised by Phymatolithon calcareum in gravels and sand with a variety of associated echinoderms. The echinoderm Neopentadactyla mixta is frequently observed in this biotope. Other echinoderms such as Echinus esculentus, Ophiura albida and rarely Luidia ciliaris may also be present. Red seaweed such as Plocamium cartilagineum may be present but at a much lower abundance than in Pcal.R and with fewer species present. Other, more ubiquitous echinoderms such as Asterias rubens may also be found in low numbers throughout Pcal biotopes.


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
Cerianthus lloydii 3 Occasional 41-60 %
Chaetopterus variopedatus 2 Occasional 41-60 %
Lanice conchilega 3 Occasional 41-60 %
Pomatoceros triqueter 2 Occasional 41-60 %
Pagurus bernhardus 10 Occasional 61-80 %
Liocarcinus depurator 3 Occasional 41-60 %
Gibbula magus 2 Occasional 41-60 %
Tectura virginea 1 Occasional 21-40 %
Pecten maximus 3 Occasional 41-60 %
Ensis 2 Frequent 21-40 %
Luidia ciliaris 1 Rare 21-40 %
Asterias rubens 8 Occasional 81-100 %
Ophiura albida 1 Occasional 21-40 %
Echinus esculentus 4 Occasional 41-60 %
Neopentadactyla mixta 4 Frequent 41-60 %
Pomatoschistus 1 Occasional 21-40 %
Phymatolithon calcareum 20 Common 61-80 %
Plocamium cartilagineum 2 Occasional 41-60 %
Desmarestia viridis 1 Occasional 21-40 %
Laminaria saccharina 3 Occasional 41-60 %

Similar biotopes or habitat types

Pcal.R occurs shallower than Pcal.Nmix with a greater abundance and diversity of red seaweeds.

Classification history of this biotope or habitat type

Classification version Code
97.06 IGS.Phy.HEc

Back to top