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Marine Habitat Classification

Description of biotope or habitat type

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   Polyides rotunda and/or Furcellaria lumbricalis on reduced salinity infralittoral rock

Physical habitat description

Salinity Reduced (18-30ppt), Low (<18ppt)
Wave exposure Very sheltered, Extremely sheltered
Tidal streams Very weak (negligible)
Substratum Bedrock; boulders, cobbles and pebbles
Zone Infralittoral
Depth Band 0-5 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 IR.LIR.Lag.ProtFur <I>Polyides rotunda</I> and/or <I>Furcellaria lumbricalis</I> on reduced salinity infralittoral 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'
  • 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.


Bedrock and boulders characterised by a dense turf of the red seaweeds Polyides rotunda and/or Furcellaria lumbricalis, often with a dense mat of filamentous brown and green seaweeds including Ectocarpaceae and Cladophora spp. Other red seaweeds presents include Chondrus crispus, Gracilaria gracilis and coralline crusts as well as the odd brown seaweed Chorda filum or Laminaria spp. Associated with these seaweeds are a variety of ascidians including Clavelina lepadiformis, Ascidiella aspersa, Ascidiella scabra and Ciona intestinalis as well as the anemones Anemonia viridis and Actinia equina and the sponge Halichondria panicea. More mobile fauna include the starfish Asterias rubens, the crab Carcinus maenas, the hermit crab Pagurus bernhardus, the opossum shrimps Mysidae and the gastropod Littorina littorea. Attached to the rock or cobbles are spirorbid polychaetes and the mussel Mytilus edulis. Please notice that part of this diversity is due to large differences between sites.


Nearby rock (AscSpAs and FChoG) and seagrass Ruppia maritima dominating much of the surrounding muddy sediment (Rup). Mixed sediment supports filamentous green seaweeds e.g. Cladophora spp. and Derbesia marina on (FiG).

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Furcellaria lumbricalis 11 Common 41-60%
Polyides rotunda 10 Common 41-60%
Asterias rubens 7 Occasional 61-80%
Corallinaceae 6 Occasional 61-80%
Carcinus maenas 6 Frequent 41-60%
Mysidae 5 Occasional 41-60%
Ascidiella aspersa 5 Frequent 41-60%
Chorda filum 5 Frequent 41-60%
Ciona intestinalis 5 Frequent 41-60%
Ectocarpaceae 3 Occasional 21-40%
Ulva 3 Occasional 41-60%
Spirorbinae 3 Frequent 21-40%
Actinia equina 2 Occasional 21-40%
Anemonia viridis 2 Frequent 21-40%
Chondrus crispus 2 Occasional 21-40%
Cladophora 2 Frequent 21-40%
Cladophora rupestris 2 Occasional 21-40%
Clavelina lepadiformis 2 Frequent 21-40%
Ascidiella scabra 1 Occasional 21-40%
Gracilaria gracilis 1 Frequent 21-40%
Halichondria panicea 1 Occasional 21-40%
Littorina littorea 1 Frequent 21-40%
Mytilus edulis 1 Frequent 21-40%
Pagurus bernhardus 1 Frequent 21-40%
Laminaria 1 Frequent 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
2015 (15.03) IR.LIR.Lag.ProtFur
1997 (97.06) SLR.PolFur

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