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Marine Habitat Classification

Description of biotope or habitat type

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   Sargassum muticum in eulittoral rockpools

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered
Tidal streams
Substratum Bedrock
Zone Eulittoral - lower, Eulittoral - mid
Depth Band Lower shore, Mid shore
Other Features Rockpool

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.FLR.Rkp.FK.Sar <I>Sargassum muticum</I> in eulittoral rockpools

  • 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.


Shallow rockpools throughout the eulittoral zone on exposed to moderately exposed shores dominated by the brown seaweed Sargassum muticum and the red seaweed Corallina officinalis. Other brown seaweeds, including the kelp Saccharina latissima, Laminaria digitata and the wrack Fucus serratus may occur along with Dictyota dichotoma, but S. muticum always dominates. Underneath the canopy is a rich red seaweed community which includes both foliose and filamentous species such as Palmaria palmata, Chondrus crispus, Lomentaria articulata, Osmundea pinnatifida, Ceramium spp. and Dumontia contorta. Encrusting coralline algae and Hildenbrandia rubra often cover the rock surface. The foliose green seaweed Ulva lactuca is usually present in high abundance growing on the mobile gravel and boulders on the bottom of the rockpools, often along with other ephemeral green seaweeds such as Cladophora rupestris and Ulva intestinalis. The winkle Littorina littorea, the limpet Patella vulgata and the top shells Steromphala cineraria and Steromphala umbilicalis can often be found grazing on the biofilm of the rock surface or the seaweeds. Crevices and fissures in the rock provide cover for anemones such as Actinia equina and Anemonia viridis, cover while the prawn Palaemon serratus often can be found in large numbers hiding underneath the seaweed canopy or along the boulders on the bottom. Some sand scour can affect these rockpools.


Rockpools throughout the eulittoral zone in bedrock on exposed and moderately exposed shores. The non-native S. muticum is an opportunistic alga which has spread extensively around the south-west coast of Britain since its introduction to UK waters in the early 1970s from the northern Pacific ocean. It is spreading to other parts of the UK. It can dominate rockpools (and other habitats), often to the exclusion of other native species such as Laminaria spp. and fucoids.

Temporal variation

As all the available records are from the south-west of Britain some changes in the species composition can be expected from more northern sites.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Sargassum muticum 14 Abundant 81-100%
Corallina officinalis 10 Common 81-100%
Ulva lactuca 9 Common 81-100%
Corallinaceae 5 Frequent 61-80%
Chondrus crispus 4 Frequent 61-80%
Ulva intestinalis 3 Frequent 41-60%
Fucus serratus 3 Occasional 61-80%
Littorina littorea 3 Frequent 61-80%
Actinia equina 2 Occasional 61-80%
Dictyota dichotoma 2 Occasional 41-60%
Dumontia contorta 2 Frequent 41-60%
Steromphala umbilicalis 2 Occasional 61-80%
Palaemon serratus 2 Occasional 41-60%
Patella vulgata 2 Occasional 41-60%
Anemonia viridis 1 Occasional 41-60%
Calliblepharis jubata 1 Frequent 41-60%
Ceramium 1 Occasional 61-80%
Cladophora rupestris 1 Occasional 41-60%
Steromphala cineraria 1 Frequent 41-60%
Hildenbrandia rubra 1 Occasional 21-40%
Laminaria digitata 1 Occasional 41-60%
Saccharina latissima 1 Occasional 41-60%
Lomentaria articulata 1 Occasional 41-60%
Osmundea pinnatifida 1 Occasional 41-60%
Palmaria palmata 1 Occasional 41-60%

Similar biotopes or habitat types

The variants of the LR.FLR.Rkp.Cor biotope do not have the same presence of large brown seaweeds and they occur across a broader range of wave exposures.

Occurs at the same wave exposure in the mid to lower eulittoral zone. Similar species richness and species composition, though F. serratus and L. digitata dominate instead of S. muticum. Due to less environmental stress (from scour) Ulva lactuca is not found in high abundance (Occasional).


LR.FLR.RKP.FK.Sar Sargassum muticum in eulittoral rockpools, Wembury. Keith Hiscock© JNCC
LR.FLR.RKP.FK.Sar Sargassum muticum in eulittoral rockpools, Wembury. Keith Hiscock© JNCC
LR.FLR.RKP.FK.Sar Sargassum muticum in eulittoral rockpools, Rothingdean, W Sussex. Kate Northen© JNCC
LR.FLR.RKP.FK.Sar Sargassum muticum in eulittoral rockpools, Rothingdean, W Sussex. Kate Northen© JNCC

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