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Marine Habitat Classification

Description of biotope or habitat type

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   Fucus serratus, sponges and ascidians on tide-swept lower eulittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Very strong (>6 kn), Strong (3-6 kn), Moderately strong (1-3 kn)
Substratum Bedrock; boulders; cobbles
Zone Eulittoral - lower
Depth Band
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.FserT <I>Fucus serratus</I>, sponges and ascidians on tide-swept lower eulittoral rock

  • 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 to extremely sheltered lower eulittoral bedrock, boulders and cobbles that are subject to increased tidal water movement and characterised by the wrack Fucus serratus and a rich assemblage of filter-feeding fauna. This community is encouraged by the increased water movement. It includes species such as the sponges Halichondria panicea and Hymeniacidon perlevis, which occur frequently on steep and overhanging faces. Underneath the F. serratus canopy is a diverse flora of foliose red seaweeds including Mastocarpus stellatus, Lomentaria articulata, Membranoptera alata and Chondrus crispus. The green seaweeds Cladophora spp., Ulva intestinalis and Ulva lactuca and the wrack Ascophyllum nodosum are present though usually in small numbers. On the rock underneath the seaweed canopy, species such as the limpet Patella vulgata, the barnacles Semibalanus balanoides and Balanus crenatus and the whelk Nucella lapillus can be found though in lower abundance than higher up the shore. Also present on the rock are the tube-forming polychaetes Spirobranchus triqueter and spirorbids and more mobile species such as the winkles Littorina fabalis and Littorina littorea, the top shell Steromphala cineraria and the crab Carcinus maenas. Lastly, several species of bryozoans are usually present including Electra pilosa and Alcyonidium gelatinosum, all competing for space with the hydroid Dynamena pumila, which can form dense populations on the F. serratus fronds.


Areas where increased tidal movement influences such a community are in the narrows and/or intertidal sills of Scottish sea lochs and the rias in south-west England. In the few cases where the rock is also subject to variable salinity, an impoverished community results and records should be classified as Fserr.VS rather than the present biotope.

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Fucus serratus 19 Abundant 81-100%
Halichondria panicea 6 Frequent 81-100%
Corallinaceae 5 Frequent 61-80%
Dynamena pumila 5 Frequent 61-80%
Mastocarpus stellatus 5 Frequent 61-80%
Cladophora 4 Occasional 41-60%
Patella vulgata 4 Occasional 61-80%
Ulva intestinalis 3 Frequent 61-80%
Spirorbinae 3 Frequent 41-60%
Ulva lactuca 3 Frequent 61-80%
Nucella lapillus 3 Occasional 61-80%
Semibalanus balanoides 2 Frequent 41-60%
Ascophyllum nodosum 2 Occasional 41-60%
Balanus crenatus 2 Common 41-60%
Carcinus maenas 2 Occasional 41-60%
Chondrus crispus 2 Occasional 41-60%
Lomentaria articulata 2 Occasional 41-60%
Spirobranchus triqueter 2 Occasional 41-60%
Alcyonidium gelatinosum 1 Common 21-40%
Steromphala cineraria 1 Occasional 41-60%
Hymeniacidon perlevis 1 Occasional 41-60%
Littorina littorea 1 Occasional 41-60%
Littorina fabalis 1 Occasional 41-60%
Membranoptera alata 1 Occasional 41-60%

Similar biotopes or habitat types

Occurs on bedrock and boulders at a wide range of wave exposures. It also has a high species richness due to a diversity of micro-habitats. Mobile species such as Pisidia longicornis, Porcellana platycheles and Cancer pagurus are usually present.

Occurs on bedrock and in weak tidal streams. It has a lower species diversity and sponges such as H. perleve and hydroids such as Alcyonidium spp. and Electra pilosa are usually not present.

Occurs on variable salinity lower eulittoral bedrock and boulders. The individual M. edulis are large and the barnacle Austrominius modestus can be present in high numbers. Sponges such as Halichondria panicea and foliose red seaweeds such as Lomentaria articulata or Chondrus crispus are absent.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) SLR.Fserr.T
1996 (6.95) SLR.Fser.T
1995 LRK.FSE.T


LR.HLR.FT.FserT Fucus serratus, sponges and ascidians on tide-swept lower eulittoral rock, Mhic Eachain. ANON© JNCC
LR.HLR.FT.FserT Fucus serratus, sponges and ascidians on tide-swept lower eulittoral rock, Mhic Eachain. ANON© JNCC

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