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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.

   Dense Desmarestia spp. with filamentous red seaweeds on exposed infralittoral cobbles, pebbles and bedrock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock & boulders
Zone Infralittoral - upper, Sublittoral fringe
Depth Band 5-10 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.HIR.KSed.DesFilR Dense <I>Desmarestia</I> spp. with filamentous red seaweeds on exposed infralittoral cobbles, pebbles and bedrock

  • 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.


Wave-exposed seasonally mobile substrata (pebbles, cobbles) dominated by dense stands of the brown seaweed Desmarestia aculeata and/or Desmarestia ligulata. Infralittoral pebbles and cobbles that are scoured through mobility during storms, but become stable in the summer allowing the growth of such algae as Desmarestia spp. Filamentous red seaweeds such as Bonnemaisonia asparagoides and Vertebrata byssoides are usually present. Stunted individuals of the kelp such as Laminaria hyperborea and Saccharina latissima may be present where bedrock is available. A variety of foliose red seaweeds such as Cryptopleura ramosa, Chondrus crispus, Plocamium cartilagineum, Hypoglossum hypoglossoides and Nitophyllum punctatum may on occasion be present underneath the kelp canopy. Other red algae including Corallina officinalis, Rhodomela confervoides and coralline crusts including Lithothamnion spp. may be present as well as well as the foliose brown seaweed Dictyota dichotoma and the green Ulva intestinalis. Due to the nature of this biotope the faunal component is very impoverished though the gastropod Steromphala cineraria can be found among the cobbles.


Often a narrow zone on mixed substrata below a stable zone of kelp on bedrock. Where seasonally mobile substrata affect nearby bedrock this biotope may occur in place of kelp forest.

Temporal variation

See biotope description

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Desmarestia aculeata 24 Common 81-100%
Bonnemaisonia asparagoides 9 Occasional 21-40%
Vertebrata byssoides 9 Frequent 61-80%
Dictyota dichotoma 6 Frequent 41-60%
Saccharina latissima 4 Occasional 41-60%
Plocamium cartilagineum 4 Frequent 41-60%
Cryptopleura ramosa 3 Occasional 21-40%
Desmarestia ligulata 3 Frequent 21-40%
Hypoglossum hypoglossoides 3 Rare 41-60%
Lithothamnion 3 Common 21-40%
Spirobranchus triqueter 3 Occasional 21-40%
Urticina felina 3 Occasional 21-40%
Laminaria 3 Frequent 21-40%
Corallinaceae 2 Frequent 21-40%
Corallina officinalis 2 Occasional 21-40%
Steromphala cineraria 2 Frequent 41-60%
Rhodophyta 2 Frequent 21-40%
Chondrus crispus 1 Frequent 41-60%
Delesseria sanguinea 1 Rare 21-40%
Ulva 1 Occasional 21-40%
Laminaria hyperborea 1 Occasional 21-40%
Nitophyllum punctatum 1 Occasional 21-40%
Rhodomela confervoides 1 Occasional 21-40%

Similar biotopes or habitat types

Occurs on bedrock at slightly more exposed coasts. The kelp Saccorhiza polyschides has a higher abundance (Abundant), while the brown seaweed D. aculeata has a lower abundance (Occasional) than in IR.HIR.KSed.DesFilR.

Occurs at similar conditions but at slightly more exposed coasts. The two kelps Saccharina latissima and S. polyschides has a higher abundance (both Common), while the brown seaweed D. aculeata has a lower abundance (Occasional) than in IR.HIR.KSed.DesFilR.

Occurs in similar conditions as IR.HIR.KSed.DesFilR but has a very low species diversity and lacks the brown seaweed D. aculeata.

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