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Marine Habitat Classification

Description of biotope or habitat type

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   Fucus serratus with sponges, ascidians and red seaweeds on tide-swept lower eulittoral mixed substrata

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Sheltered, Very sheltered
Tidal streams Moderately strong (1-3 kn)
Substratum Boulders, cobbles and pebbles on muddy sediments
Zone Eulittoral - lower
Depth Band Lower shore
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 LR.HLR.FT.FserTX <I>Fucus serratus</I> with sponges, ascidians and red seaweeds on tide-swept lower eulittoral mixed substrata

  • 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'

Point data based on records in the UK Marine Recorder Snapshot.


Sheltered lower shore boulders, cobbles and pebbles on muddy sediments that are subject to enhanced tidal water movement and characterised by a species rich community. Dominant species include the sponges Halichondria panicea and Hymeniacidon perlevis, the sea squirts Ascidiella aspera, Ascidiella scabra, Styela clava and Botryllus schlosseri. A number of filamentous red seaweeds including Halurus flosculosus, Ceramium spp., Gracilaria gracilis, Vertebrata fucoides and foliose seaweeds Mastocarpus stellatus and Chondrus crispus are usually present. The brown seaweed Dictyota dichotoma and the wrack Fucus serratus with colonies of the hydroid Dynamena pumila, and Ectocarpus sp. may be found on more stable substrata. Boulders and large cobbles provide substrata for the top shell Steromphala cineraria, the whelk Nucella lapillus and barnacles such as Semibalanus balanoides, Balanus crenatus, or in areas with variable salinity Austrominius modestus, and the tube-forming polychaete Spirobranchus triqueter. Patches of sand or mud are often characterised by the polychaete Lanice conchilega and the polychaete Sabella pavonina. Aggregations of the mussel Mytilus edulis and, in southern and eastern England the limpet Crepidula fornicata, may be found attached to cobbles and pebbles. Sites in Scottish sea lochs may support maerl Lithothamnion spp. and bivalves Venerupis corrugata (see also VsenMtru).


This biotope is found above a community dominated by kelp such as Laminaria digitata (Ldig) or seagrass beds dominated by Zostera subg. Zostera marina (Zmar) depending on the substrata found below. It is found below biotopes dominated by wrack Fucus vesiculosus (Fves) or M. edulis beds (MytFab; Myt.Myt).

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Chondrus crispus 6 Frequent 41-60%
Steromphala cineraria 6 Frequent 61-80%
Littorina littorea 5 Occasional 61-80%
Spirobranchus triqueter 5 Occasional 41-60%
Ulva intestinalis 4 Occasional 61-80%
Fucus serratus 4 Frequent 61-80%
Halichondria panicea 4 Occasional 41-60%
Mytilus edulis 4 Occasional 41-60%
Ulva lactuca 4 Frequent 61-80%
Semibalanus balanoides 3 Occasional 41-60%
Corallinaceae 3 Occasional 61-80%
Carcinus maenas 3 Occasional 41-60%
Ceramium 3 Occasional 41-60%
Austrominius modestus 3 Occasional 41-60%
Gracilaria gracilis 3 Occasional 41-60%
Lanice conchilega 3 Occasional 41-60%
Mastocarpus stellatus 3 Occasional 41-60%
Hymeniacidon perlevis 2 Occasional 41-60%
Nucella lapillus 2 Occasional 41-60%
Ascidiella scabra 1 Occasional 21-40%
Balanus crenatus 1 Occasional 21-40%
Botryllus schlosseri 1 Rare 21-40%
Crepidula fornicata 1 Occasional 21-40%
Lithothamnion 1 Occasional 1-20%
Vertebrata fucoides 1 Rare 41-60%
Sabella pavonina 1 Occasional 21-40%
Styela clava 1 Rare 21-40%

Similar biotopes or habitat types

Occurs on bedrock and large boulders in areas with moderately strong tidal streams. It has a lower species richness and it lacks species associated with the mixed substrata such as L. conchilega, while filterfeeders such as spirorbid polychaetes are usually present.

Occurs on similar substrata, but is not tide-swept. It lacks the filter-feeding community associated with tide-swept conditions. Species not found include sponges such as H. perleve and bryozoans such as Electra pilosa.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) SLR.FserX.T

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