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Marine Habitat Classification

Description of biotope or habitat type

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   Saccharina latissima and/or Saccorhiza polyschides on exposed infralittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Very exposed, Exposed, Moderately exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock; boulders and cobbles
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m, 20-30 m
Other Features Often (but not always) disturbance due to scour or seasonal instability of substratum

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.SlatSac <I>Saccharina latissima</I> and/or <I>Saccorhiza polyschides</I> on exposed 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.


A forest or park of the fast-growing, opportunistic kelps Saccharina latissima and/or Saccorhiza polyschides often occurs on seasonally unstable boulders or sand/pebble scoured infralittoral rock. The substratum varies from large boulders in exposed areas to smaller boulders and cobbles in areas of moderate wave exposure or nearby bedrock. In these cases, movement of the substratum during winter storms prevents a longer-lived forest of Laminaria hyperborea from becoming established. This biotope also develops on bedrock where it is affected by its close proximity to unstable substrata. Other fast-growing brown seaweeds such as Desmarestia viridis, Desmarestia aculeata, Cutleria multifida and Dictyota dichotoma are often present. Some L. hyperborea plants may occur in this biotope, but they are typically small since the plants do not survive many years. The kelp stipes are usually epiphytised by red seaweeds such as Delesseria sanguinea and Phycodrys rubens. Other red seaweeds present beneath the kelp canopy include Plocamium cartilagineum, Nitophyllum punctatum, Metacallophyllis laciniata and Cryptopleura ramosa. Encrusting algae often form a prominent cover on the rock surfaces, including red, brown and coralline crusts. Faunal richness and diversity is generally low compared to the more stable L. hyperborea kelp forest and park communities (LhypR). Where some protection is afforded the anthozoan Alcyonium digitata can occur in addition to the more robust species such as the tube-building worm Spirobranchus triqueter. Mobile species include the to shell Steromphala cineraria and Calliostoma zizyphinum and the sea urchin Echinus esculentus. The hydroid Obelia geniculata and the bryozoan Membranipora membranacea can often be found colonising the kelp fronds.


This biotope can be found below the L. hyperborea zone (LhypFa or LhypR), especially where close to a rock/ sand interface (where it is subject to sand/pebble scour in winter). Where this biotope occurs on bedrock, not scoured by mobile sediment, it is thought to occur as a result of intense wave action in winter storms which is too severe to allow L. hyperborea to develop and remain in shallow water.

Temporal variation

Due to the disturbed nature of this biotope there can be significant changes in the structure of the community. Coralline and brown algal crusts with sparse kelp plants generally dominate areas that have been recently disturbed. Diversity is low and a few species of fast-growing seaweeds can dominate the seabed. A longer established community will have larger, mixed kelp plants and a greater diversity of red seaweeds.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Laminaria hyperborea 15 Common 41-60%
Corallinaceae 12 Common 81-100%
Echinus esculentus 8 Occasional 61-80%
Asterias rubens 5 Occasional 61-80%
Delesseria sanguinea 5 Occasional 61-80%
Saccharina latissima 5 Common 81-100%
Steromphala cineraria 4 Occasional 41-60%
Saccorhiza polyschides 4 Common 61-80%
Membranipora membranacea 2 Frequent 21-40%
Alcyonium digitatum 2 Occasional 41-60%
Calliostoma zizyphinum 2 Occasional 41-60%
Metacallophyllis laciniata 2 Frequent 41-60%
Cryptopleura ramosa 2 Frequent 41-60%
Cutleria multifida 2 Frequent 21-40%
Dictyota dichotoma 2 Frequent 41-60%
Obelia geniculata 2 Frequent 21-40%
Phycodrys rubens 2 Occasional 41-60%
Plocamium cartilagineum 2 Frequent 41-60%
Spirobranchus triqueter 2 Frequent 21-40%
Desmarestia aculeata 1 Occasional 21-40%
Desmarestia viridis 1 Occasional 21-40%
Nitophyllum punctatum 1 Occasional 41-60%

Similar biotopes or habitat types

Occurs at similar conditions but at slightly less exposed coasts. The brown seaweed Desmarestia aculeata has a higher abundance (Abundant) than in IR.HIR.KSed.Sac, while the kelp S. latissima has a lower abundance (Occasional). The kelp S. polyschides rarely occurs.

Classification history of this biotope or habitat type

Classification version Code
2015 (15.03) IR.HIR.KSed.LsacSac
1996 (6.95) EIR.LsacSpol

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