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Marine Habitat Classification

Description of biotope or habitat type

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   Saccorhiza polyschides and other opportunistic kelps on disturbed sublittoral fringe 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
Zone Infralittoral - upper, Sublittoral fringe
Depth Band 0-5 m, Lower shore
Other Features Disturbed (by storms or sand scour)

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.Sac <I>Saccorhiza polyschides</I> and other opportunistic kelps on disturbed sublittoral fringe 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.


Exposed low-lying reefs in the sublittoral fringe or upper infralittoral (generally above 5m depth), mainly in the southwest and west, dominated by the kelp Saccorhiza polyschides. This opportunistic coloniser replaces Laminaria digitata or Laminaria hyperborea as the dominant kelp, following 'disturbance' of the canopy. This may be the result of storms, when loose sediment and even cobbles or boulders are mobilised, scouring most seaweeds and animals from the surrounding rock. As S. polyschides is essentially a summer annual (occasionally it lasts into a second year), it is also particularly common close to rock/sand interfaces which become too scoured during winter months to prevent the longer-living kelps from surviving. As a result of the transient nature of this biotope, its composition is varied; it may contain several other kelp species, including L. digitata, Saccharina latissima and Alaria esculenta, at varying abundances. Laminaria spp. sporelings can also be a prominent feature of the site. Beneath the kelp, (scour-tolerant) red seaweeds including Corallina officinalis, Kallymenia reniformis, Plocamium cartilagineum, Chondrus crispus, Dilsea carnosa and encrusting coralline algae are often present. Foliose red seaweeds such as Metacallophyllis laciniata, Cryptopleura ramosa and Palmaria palmata also occur in this biotope. P. palmata and Delesseria sanguinea often occur as epiphytes on the stipes of L. hyperborea, when it is present. The foliose green seaweed Ulva spp. is fast to colonise newly cleared areas of rock and is often present along with the foliose brown seaweed Dictyota dichotoma. Due to the disturbed nature of this biotope, fauna are generally sparse, being confined to encrusting bryozoans and/or sponges, such as Halichondria panicea and the gastropod Steromphala cineraria.


On some shores (for example in Cornwall and south-west Ireland), S. polyschides competes so effectively with the other laminarians that it forms a well-defined zone in shallow water, between the L. digitata (Ldig) and L. hyperborea zones (LhypR and Lhyp). Elsewhere, it is found at sites that have been physically disturbed, removing areas of established kelp (L. hyperborea) thus allowing this opportunistic biotope to develop over a short space of time.

Temporal variation

There may be significant variations in this biotope over time, as by its very nature, it is dominated by many fast-growing annual seaweeds. The foliose green seaweed Ulva sp. is fast to colonise newly cleared areas of rock and can be present as a dense growth on the rock around the Saccorhiza polyschides. Similarly, large patches of Laminaria spp. sporelings may be present at times.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Saccorhiza polyschides 30 Abundant 81-100%
Corallinaceae 10 Frequent 61-80%
Cryptopleura ramosa 4 Frequent 41-60%
Saccharina latissima 4 Frequent 41-60%
Steromphala cineraria 3 Frequent 41-60%
Laminaria digitata 3 Common 21-40%
Laminaria hyperborea 3 Common 21-40%
Plocamium cartilagineum 3 Occasional 41-60%
Alaria esculenta 2 Occasional 21-40%
Corallina officinalis 2 Frequent 21-40%
Dictyota dichotoma 2 Frequent 21-40%
Dilsea carnosa 2 Frequent 21-40%
Palmaria palmata 2 Frequent 21-40%
Ulva lactuca 2 Frequent 21-40%
Metacallophyllis laciniata 1 Frequent 21-40%
Delesseria sanguinea 1 Frequent 21-40%
Halichondria panicea 1 Occasional 21-40%
Kallymenia reniformis 1 Frequent 21-40%

Similar biotopes or habitat types

This biotope occurs in deeper water and often forms a mixed kelp canopy of S. latissima, L. hyperborea and S. polyschides. Although S. polyschides can occur in equal abundance to the other kelps it may be absent altogether from some sites. It supports a slightly richer faunal community of species commonly found in deeper water, such as Alcyonium digitatum, Caryophyllia (Caryophyllia) smithii and encrusting bryozoans.

Classification history of this biotope or habitat type

Classification version Code
1996 (6.95) MIR.Spol

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