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.

   Loose-lying mats of Phyllophora crispa on infralittoral muddy sediment

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Sheltered, Very sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Mud or muddy sand with shells, gravel or pebbles
Zone 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.KSwSS.Pcri Loose-lying mats of <I>Phyllophora crispa</I> on infralittoral muddy 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.


Infralittoral muddy sand and sandy mud, sometimes with some shells or pebbles, and a dense, loose-lying cover of Phyllophora crispa. This biotope occurs in very sheltered conditions such as those found in sealochs and voes. SMP.Pcri is similar to other biotopes described with dense, loose-lying algae but has been less frequently recorded, and from the few records available, appears to occur in slightly deeper infralittoral waters primarily between 10m to 30m and typically in fully saline waters. The seaweeds in this biotope may be epiphytised by ascidians such as Ascidiella aspera. Kelp such as Laminaria saccharina and red seaweeds including Plocamium cartilagineum may be present in some areas. The scallops Pecten maximus and Aequipecten opercularis may also be found occasionally in this biotope and Trailliella/Bonnemaisonia hamifera may also be present but not at the levels found in SMP.Tra.


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
Hydractinia echinata 2 Occasional 21-40 %
Cerianthus lloydii 1 Frequent 21-40 %
Terebellidae 1 Frequent 41-60 %
Balanus crenatus 2 Occasional 41-60 %
Pagurus bernhardus 6 Occasional 61-80 %
Liocarcinus depurator 14 Frequent 81-100 %
Carcinus maenas 3 Occasional 41-60 %
Pecten maximus 2 Occasional 41-60 %
Aequipecten opercularis 2 Occasional 41-60 %
Electra pilosa 1 Occasional 21-40 %
Henricia 1 Rare 21-40 %
Asterias rubens 6 Occasional 41-60 %
Echinus esculentus 3 Occasional 41-60 %
Ascidiella aspersa 5 Frequent 41-60 %
Bonnemaisonia hamifera 2 Common 21-40 %
Phyllophora crispa 27 Abundant 81-100 %
Plocamium cartilagineum 3 Frequent 41-60 %
Laminaria saccharina 3 Frequent 41-60 %

Similar biotopes or habitat types

Similar to Pcri however, Trailliea, if present in Pcri, does not form distinct mats as in Tra.

Classification history of this biotope or habitat type

Classification version Code
97.06 IMX.Pcri

Back to top