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Marine Habitat Classification

Description of biotope or habitat type

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   Fucoids in variable salinity

Physical habitat description

Salinity Reduced (18-30ppt), Variable (18-35 ppt), Low (<18ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
Substratum Bedrock, boulders and cobbles
Zone Eulittoral - lower, Eulittoral - mid, Eulittoral - upper, Eulittoral
Depth Band Lower shore, Mid shore, Upper 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.LLR.FVS Fucoids in variable salinity

  • 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.


Blankets of fucoid seaweeds dominating sheltered to extremely sheltered rocky shores with variable salinity. The wrack Pelvetia canaliculata (PelVS) occurs on the upper shore, with the wrack Fucus spiralis (FspiVS) below. The middle shore is dominated by vast areas of the wrack Ascophyllum nodosum or the wrack Fucus vesiculosus (AscVS, FvesVS) or a mixture of both. The wrack Fucus serratus covers lower shore bedrock and boulders (FserVS). Fucus ceranoides can be found on extremly sheltered shores with variable or low salinity (Fcer). The variable salinity communities are species impoverished compared to fucoids in full salinity or in tide-swept conditions as red seaweeds and sponges are usually absent. Underneath the canopy are a few green seaweeds including Ulva intestinalis and Cladophora spp., while the red seaweed Vertebrata lanosa can be found as an epiphyte on A. nodosum. On the rock and among the boulders are the winkles Littorina littorea and Littorina saxatilis, the crab Carcinus maenas, the barnacles Semibalanus balanoides and Austrominius modestus and even the occasional mussel Mytilus edulis.


On sheltered eulittoral rocky shores with variable salinity conditions, such as sea loch or estuaries.

Temporal variation

No temporal variation data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Fucus vesiculosus 13 Frequent 41-60%
Semibalanus balanoides 11 Frequent 41-60%
Ascophyllum nodosum 11 Common 41-60%
Ulva intestinalis 8 Occasional 41-60%
Carcinus maenas 7 Occasional 41-60%
Fucus spiralis 7 Frequent 21-40%
Littorina littorea 7 Occasional 41-60%
Austrominius modestus 6 Frequent 21-40%
Mytilus edulis 4 Occasional 21-40%
Gammaridae 3 Frequent 21-40%
Littorina 3 Occasional 61-80%
Fucus serratus 2 Frequent 21-40%
Pelvetia canaliculata 1 Rare 1-20%

Similar biotopes or habitat types

Not applicable or unknown.

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