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Marine Habitat Classification


Description of biotope or habitat type

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   Mixed turf of bryozoans and erect sponges with Dysidea fragilis and Actinothoe sphyrodeta on tide-swept wave-exposed circalittoral rock


Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Extremely exposed, Very exposed, Exposed, Moderately exposed
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn)
Substratum Bedrock; boulder
Zone Circalittoral - lower, Circalittoral - upper
Depth Band 5-10 m, 10-20 m, 20-30 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.ByErSp.DysAct Mixed turf of bryozoans and erect sponges with <I>Dysidea fragilis</I> and <I>Actinothoe sphyrodeta</I> on tide-swept wave-exposed 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 variant typically occurs on exposed and moderately wave-exposed bedrock and boulders subject to a variety of tidal regimes (from strong through to weak). It is found mainly in the 10-20m depth range and does not usually occur deeper than 30 m. It therefore often straddles the upper circalittoral and lower infralittoral. It often has a light covering of silt and sand may be in the vicinity. Sponges form a dominant part of this variant, although cover usually appears patchy, with no single species dominating. Species present include Dysidea fragilis, Pachymatisma johnstonia, Amphilectus fucorum, Hemimycale columella, Cliona celata, Stelligera montagui, Polymastia boletiformis, Stelligera stuposa, Raspailia ramosa, Tethya aurantium, Polymastia mamillaris and Axinella dissimilis. Tufts of large hydroids such as Nemertesia antennina, frequently recorded on the tops of outcrops and boulders, stand out more clearly than the understorey of finer hydroid and bryozoan turf such as Aglaophenia pluma, Bugulina flabellata, Crisularia plumosa, crisiids, Cellaria sinuosa and Bugulina turbinata. Other bryozoans such as Alcyonidium diaphanum and Flustra foliacea are also frequently recorded. Other more widespread species present include Asterias rubens, Actinothoe sphyrodeta, Balanus crenatus, Caryophyllia smithii, Corynactis viridis, Necora puber and Clavelina lepadiformis. This variant has been recorded off the south east coast of Ireland, the welsh coast and Lundy Island.

Situation

This biotope is typically found on exposed coasts, with exposed kelp forest in the infralittoral zone, characterised by species such as Laminaria hyperborea and Saccorhiza polyschides. The ByErSp.DysAct variant is usually found below ByErSp.Eun, with similar geographic range.

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
Dysidea fragilis 5 Frequent 81-100%
Asterias rubens 4 Frequent 81-100%
Pachymatisma johnstonia 4 Occasional 81-100%
Actinothoe sphyrodeta 3 Frequent 81-100%
Alcyonium digitatum 3 Occasional 61-80%
Balanus crenatus 3 Frequent 61-80%
Caryophyllia smithii 3 Frequent 61-80%
Amphilectus fucorum 3 Frequent 81-100%
Flustra foliacea 3 Frequent 61-80%
Nemertesia antennina 3 Frequent 61-80%
Alcyonidium diaphanum 2 Frequent 61-80%
Bugulina flabellata 2 Occasional 61-80%
Crisularia plumosa 2 Frequent 61-80%
Cliona celata 2 Occasional 61-80%
Crisiidae 2 Common 41-60%
Hemimycale columella 2 Occasional 61-80%
Polymastia boletiformis 2 Frequent 41-60%
Raspailia ramosa 2 Occasional 61-80%
Stelligera montagui 2 Occasional 61-80%
Stelligera stuposa 2 Occasional 61-80%
Aglaophenia pluma 1 Frequent 41-60%
Axinella dissimilis 1 Occasional 41-60%
Bryozoa 1 Frequent 41-60%
Bugulina turbinata 1 Frequent 41-60%
Cellaria sinuosa 1 Frequent 41-60%
Clavelina lepadiformis 1 Occasional 41-60%
Corynactis viridis 1 Frequent 41-60%
Necora puber 1 Occasional 61-80%
Polymastia mamillaris 1 Occasional 61-80%
Tethya aurantium 1 Occasional 61-80%

Similar biotopes or habitat types

CR.HCR.XFa.ByErSp.Eun
This sub-biotope is found on very wave-exposed circalittoral bedrock with slightly weaker tidal streams than CR.HCR.XFa.ByErSp.DysAct. It is also found slightly deeper than CR.HCR.XFa.ByErSp.DysAct. E. verrucosa is absent from CR.HCR.XFa.ByErSp.DysAct.

CR.HCR.XFa.ByErSp.Cyl
This sub-biotope occurs under similar wave-exposure conditions but with weaker tides than CR.HCR.XFa.ByErSp.DysAct. It is also found slightly deeper than CR.HCR.XFa.ByErSp.DysAct. Both sub-biotopes have similar suites of species but distinct geographical distributions: CR.HCR.XFa.ByErSp.DysAct only tends to be found off Wales and Lundy whereas CR.HCR.XFa.ByErSp.Cyl is usually found off the west coast of Ireland.

CR.HCR.XFa.FluCoAs
This biotope occurs under similar wave-exposure conditions, but with slightly weaker tides than CR.HCR.XFa.ByErSp.DysAct. Both tend to occur throughout similar depth ranges and substratum. They also both tend to have a thin layer of silt overlying them. Sponges, hydroids and bryozoans are present in both biotopes; although F. foliacea is present in CR.HCR.XFa.ByErSp.DysAct, it is not present to the same abundance as in CR.HCR.XFa.FluCoAs, where it forms dense aggregations on the bedrock and boulders. In addition, species such as C. smithii and C. viridis are absent from CR.HCR.XFa.FluCoAs.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) CR.MCR.XFa.ErSPbolSH

Photos

CR.HCR.XFA.ByErSp.DysAct Mixed turf of bryozoans and erect sponges with Dysidea fragilis and Actinothoe sphyrodeta on tide-swept wave-exposed circalittoral rock, N of Jennys Cove, Lundy. Keith Hiscock© JNCC
CR.HCR.XFA.ByErSp.DysAct Mixed turf of bryozoans and erect sponges with Dysidea fragilis and Actinothoe sphyrodeta on tide-swept wave-exposed circalittoral rock, N of Jennys Cove, Lundy. Keith Hiscock© JNCC
CR.HCR.XFA.ByErSp.DysAct Mixed turf of bryozoans and erect sponges with Dysidea fragilis and Actinothoe sphyrodeta on tide-swept wave-exposed circalittoral rock, Penninis Head. Keith Hiscock© JNCC
CR.HCR.XFA.ByErSp.DysAct Mixed turf of bryozoans and erect sponges with Dysidea fragilis and Actinothoe sphyrodeta on tide-swept wave-exposed circalittoral rock, Penninis Head. Keith Hiscock© JNCC

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