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Marine Habitat Classification


Description of biotope or habitat type

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   Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock, boulders or cobbles with coarse sediment
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m
Other Features Sediment abrasion

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.XKHal <I>Halidrys siliquosa</I> and mixed kelps on tide-swept infralittoral rock with coarse sediment

  • 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.

Description

Tide-swept boulders and cobbles, often with a mobile component to the substrata (pebbles, gravel and sand), characterised by dense stands of the brown seaweed Halidrys siliquosa. It is can be mixed with the foliose brown seaweed Dictyota dichotoma and kelp such as Laminaria saccharina and Laminaria hyperborea. Below the canopy is an undergrowth of red seaweeds that are tolerant of sand-scour such as Phyllophora crispa, Phyllophora pseudoceranoides, Rhodomela confervoides, Corallina officinalis and Chondrus crispus. Other red seaweeds such as Plocamium cartilagineum, Calliblepharis ciliata, Cryptopleura ramosa, Delesseria sanguinea, Heterosiphonia plumosa, Dilsea carnosa, Hypoglossum hypoglossoides and Brongniartella byssoides may be locally abundant, particularly in the summer months. There may be a rich epibiota on H. siliquosa, including the hydroid Aglaophenia pluma, ascidians such as Botryllus schlosseri. There is generally a sparse faunal component colonising the boulders and cobbles, comprising the tube-building polychaete Pomatoceros triqueter, the crab Cancer pagurus, the starfish Asterias rubens, the gastropod Gibbula cineraria and the sea anthozoan Urticina felina. The bryozoan Electra pilosa can form colonies on the kelp.

Situation

XKHal can occur below the tide-swept Laminaria digitata zone of the sublittoral fringe bedrock or boulders (LdigT). Less stable substrata of boulders, cobbles or pebbles may support kelp and Chorda filum in the shallows (LsacChoR) or dense ephemeral seaweeds (EphR). Sand-influenced rocky outcrops in deeper water may support a Flustra foliacea community (FluCoAs). This biotope is widespread and is found on the open coast in Wales, the south-west and the English Channel as well as more sheltered tidal rapids in the Scottish sealochs. It can form extensive forests or parks in certain areas (Dorset, Sarns). In Wales, the south-west and west of England the red seaweeds Spyridia filamentosa and Halarachnion ligulatum and brown seaweeds Dictyopteris membranacea and Taonia atomaria are frequent. In Scotland, kelp occur at a greater proportion of sites, solitary ascidians such as Ascidiella spp. are more common and the featherstar Antedon bifida and brittlestars Ophiothrix fragilis are found.

Temporal variation

Higher diversity of red seaweeds during the summer.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Aglaophenia pluma 1 Frequent 21-40 %
Urticina felina 1 Occasional 41-60 %
Pomatoceros triqueter 3 Frequent 61-80 %
Cancer pagurus 1 Occasional 41-60 %
Gibbula cineraria 2 Occasional 41-60 %
Electra pilosa 2 Frequent 41-60 %
Asterias rubens 3 Frequent 61-80 %
Botryllus schlosseri 3 Frequent 61-80 %
Corallinaceae 3 Frequent 41-60 %
Corallina officinalis 1 Occasional 41-60 %
Calliblepharis ciliata 2 Occasional 41-60 %
Dilsea carnosa 2 Occasional 61-80 %
Chondrus crispus 2 Occasional 41-60 %
Phyllophora crispa 1 Occasional 41-60 %
Phyllophora pseudoceranoides 2 Frequent 41-60 %
Plocamium cartilagineum 4 Frequent 61-80 %
Heterosiphonia plumosa 3 Frequent 61-80 %
Cryptopleura ramosa 2 Occasional 41-60 %
Hypoglossum hypoglossoides 1 Occasional 41-60 %
Brongniartella byssoides 3 Frequent 61-80 %
Rhodomela confervoides 2 Occasional 41-60 %
Dictyota dichotoma 4 Frequent 61-80 %
Laminaria hyperborea 1 Frequent 21-40 %
Laminaria saccharina 2 Occasional 41-60 %
Halidrys siliquosa 15 Common 81-100 %

Similar biotopes

IR.HIR.KSed.XKScrR
This biotope is distinguished from XKHal by its greater scour.

IR.MIR.KT.XKT
This biotope is distinguished from XKHal by occurring at more sheltered shores and by the occurrence of species like the urchin Echinus esculentus, the brittlestar Ophiothrix fragilis and the crab Carcinus maenas (all typical abundance of Occasional).

IR.MIR.KT.XKTX
Usually at more sheltered shores with a mixed substratum, variable salinity and stronger tidal streams. Species like the urchin E. esculentus, the brittlestar Ophiothrix fragilis and the crap C. maenas and encrusting red algae Lithothamnion graciale (Frequent) occurs in this biotope.

Biotope history

Classification Habitat code
97.06 MIR.HalXK
96.7 MIR.HalXK.Ft
96.7 MIR.HalXK.Pk

Photos

IR.HIR.KSED.XKHal Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment, Off Churn Rock, Farnes. Teresa Bennett © JNCC
IR.HIR.KSED.XKHal Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment, Off Churn Rock, Farnes. Teresa Bennett © JNCC
IR.HIR.KSED.XKHal Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment, Tob Valasay rapids, Tob Valasay, Lewis. Robert Irving © JNCC
IR.HIR.KSED.XKHal Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment, Tob Valasay rapids, Tob Valasay, Lewis. Robert Irving © JNCC
IR.HIR.KSED.XKHal Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment, Bun Sruth, Western Isles. ANON © JNCC
IR.HIR.KSED.XKHal Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment, Bun Sruth, Western Isles. ANON © JNCC

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