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Marine Habitat Classification


Description of biotope or habitat type

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   Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock, boulder
Zone Circalittoral - lower, Circalittoral - upper
Depth Band 10-20 m, 20-30 m, 30-50 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 CR.HCR.XFa.SwiLgAs Mixed turf of hydroids and large ascidians with <I>Swiftia pallida</I> and <I>Caryophyllia smithii</I> on weakly tide-swept circalittoral 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.

Description

This biotope typically occurs from exposed through to sheltered circalittoral bedrock or boulders subject to moderately strong to weak tidal streams. It is found in water depths ranging from 4m to 37m. This biotope is distinguished by frequently occurring Swiftia pallida, abundant Caryophilia smithii and a diverse range of ascidians including Clavelina lepadiformis, Ascidia mentula, Polycarpa pomaria, Diazona violacea and Corella parallelogramma. A sparse, yet diverse hydroid turf is often apparent, with species such as Aglaophenia tubulifera, Nemertesia antennina, Polyplumaria frutescens, Halecium halecinum, Abietinaria abietina, Nemertesia ramosa and Halopteris catharina often recorded. Spaces amongst the turf are usually colonised by the polychaete Pomatoceros triqueter and encrusting red algae. Crinoids such as Antedon petasus, Antedon bifida and Leptometra celtica may be seen filter feeding on the tops of outcrops and boulders, along with the soft coral Alcyonium digitatum. Other echinoderms such as Echinus esculentus, Crossaster papposus and Asterias rubens may also be recorded. There may also be a bryozoan component to the sparse faunal turf. Species such as Securiflustra securifrons and Eucratea loricata as well as the crustose Parasmittina trispinosa are all usually present. There may be a few isolated growths of sponge, such as Iophonopsis nigricans, Axinella infundibuliformis and Haliclona urceolus. Other species that may be present include the brachiopod Terebratulina retusa and the top shell Calliostoma zizyphinum. The crustacean Munida rugosa may be visible in crevices. All records are from the west coast of Scotland (east coast of Lewis /Outer Hebrides).

Situation

Above this biotope, kelp forests and parks are typically found in the infralittoral, with Laminaria saccharina and Laminaria hyperborea. This biotope is found in Scottish Sealochs and, in the most sheltered situations, may graduate into NeoPro at greater depths.

Temporal variation

Not known

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Axinella infundibuliformis 2 Occasional 61-80 %
Iophonopsis nigricans 2 Occasional 61-80 %
Haliclona urceolus 1 Occasional 41-60 %
Halecium halecinum 2 Occasional 61-80 %
Abietinaria abietina 2 Frequent 41-60 %
Halopteris catharina 1 Frequent 41-60 %
Nemertesia antennina 3 Occasional 61-80 %
Nemertesia ramosa 1 Occasional 41-60 %
Polyplumaria frutescens 2 Occasional 61-80 %
Aglaophenia tubulifera 4 Frequent 61-80 %
Alcyonium digitatum 2 Occasional 61-80 %
Swiftia pallida 6 Frequent 81-100 %
Caryophyllia smithii 7 Frequent 81-100 %
Pomatoceros triqueter 3 Frequent 61-80 %
Munida rugosa 2 Occasional 61-80 %
Calliostoma zizyphinum 1 Occasional 41-60 %
Terebratulina retusa 1 Occasional 41-60 %
Eucratea loricata 1 Frequent 41-60 %
Securiflustra securifrons 2 Frequent 61-80 %
Parasmittina trispinosa 2 Occasional 61-80 %
Antedon bifida 3 Frequent 61-80 %
Antedon petasus 2 Frequent 41-60 %
Leptometra celtica 1 Occasional 41-60 %
Crossaster papposus 1 Rare 61-80 %
Asterias rubens 1 Occasional 41-60 %
Echinus esculentus 3 Occasional 61-80 %
Clavelina lepadiformis 4 Occasional 81-100 %
Diazona violacea 2 Occasional 61-80 %
Corella parallelogramma 2 Occasional 61-80 %
Ascidia mentula 4 Frequent 61-80 %
Polycarpa pomaria 2 Occasional 61-80 %
Corallinaceae 1 Frequent 41-60 %

Similar biotopes

CR.MCR.EcCr.CarSwi.LgAs
This biotope is found over a broad range of sites with different wave-exposures, subject to moderately strong to very weak tidal streams. Substratum is typically similar to SwiLgAs. This biotope is more impoverished than SwiLgAs, lacking the diverse range of sponges, hydroids and bryozoans but still with frequent S. pallida.

CR.MCR.EcCr.CarSwi.Aglo
This biotope occurs predominantly in the sheltered end of the wave-exposure spectrum, and is subject to only weak tidal streams. It is typically found across similar depth bands as SwiLgAs. This heavily silted biotope is characterised by S. pallida, Alcyonium glomeratum, Isozoanthus sulcatus and the prominent Holothuria forskali, the latter two of which are absent from SwiLgAs. This biotope is only present around the coast of Ireland.

Biotope history

Classification Habitat code
97.06 CR.MCR.XFa.ErSSwi

Photos

CR.HCR.XFA.SwiLgAs Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock, Opposite Gearraidh Mhurchaidh, Loch Seaforth, Lewis. Bernard Picton © JNCC
CR.HCR.XFA.SwiLgAs Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock, Opposite Gearraidh Mhurchaidh, Loch Seaforth, Lewis. Bernard Picton © JNCC
CR.HCR.XFA.SwiLgAs Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock, Pinnacle in mouth of Loch Craignish. Mark Davies © JNCC
CR.HCR.XFA.SwiLgAs Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock, Pinnacle in mouth of Loch Craignish. Mark Davies © JNCC

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