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CR.HCR.DpSp.PhaAxi
Phakellia ventilabrum and Axinellid sponges on deep, wave- exposed circalittoral rock

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Habitat (physical) description

Distribution

 Salinity: Full (30-35 ppt) 
 Wave exposure: Extremely exposed, Very exposed, Exposed 
 Tidal streams: Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible) 
 Substratum: Bedrock 
 Zone: Circalittoral - lower, Circalittoral - upper 
 Depth Band: 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.

Previous code

This biotope occurred in previous versions of the classification as:
CR.MCR.XFa.PhaAxi - Version: 97.06

Distribution of habitat CR.HCR.DpSp.PhaAxi  Phakellia ventilabrum and Axinellid sponges on deep, wave- exposed circalittoral rock
Distribution of habitat CR.HCR.DpSp.PhaAxi Phakellia ventilabrum and Axinellid sponges on deep, wave- exposed circalittoral rock, based on records on the UK Marine Recorder database and EUSeaMap. Red dots represent records on which the biotope is based. Blue dots show other certain records, black dots show records tentatively assigned to this biotope. Yellow areas show level 2 and 3 sublittoral and deep-sea habitats prediced by EUSeaMap within UK waters.

Biotope description

This biotope typically occurs on the upper faces of deep (commonly below 30m depth), wave-exposed circalittoral rock subject to negligible tidal streams. Although it occurs in exposed and very exposed conditions, at such depth, the turbulent wave action appears to have a much-attenuated effect on the fauna compared with shallower depths. As the majority of records are from depths between 30-50+ m, slightly deeper than the depths of most surveys, it is possible that this biotope is more widespread than the available dataset indicates. The sponge component of this biotope is the most striking feature, with similar species to the bryozoan and erect sponge biotope complex (BrErSp) although in this case, the sponges Phakellia ventilabrum, Axinella infundibuliformis, Axinella dissimilis and Stelligera stuposa dominate. Other sponge species frequently found on exposed rocky coasts are also present in low to moderate abundance. These include Cliona celata, Polymastia boletiformis, Haliclona viscosa, Pachymatisma johnstonia, Dysidea fragilis, Suberites carnosus, Stelligera rigida, Hemimycale columella and Tethya aurantium. The cup coral Caryophyllia smithii and the anemone Corynactis virdis may be locally abundant in some areas, along with the holothurian Holothuria forskali. The soft corals Alcyonium digitatum and Alcyonium glomeratum are frequently observed. The bryozoans Pentapora foliacea and Porella compressa are also more frequently found in this deep-water biotope. Bryozoan crusts such as Parasmittina trispinosa are also occasionally recorded. Isolated clumps of large hydroids such as Nemertesia antennina, Nemertesia ramosa and Sertularella gayi may be seen on the tops of boulders and rocky outcrops. Large echinoderms such as Echinus esculentus, Luidia ciliaris, Marthasterias glacialis, Strichastrella rosea, Henricia oculata and Aslia lefevrei may also be present. The seafan Eunicella verucosa may be locally common but to a lesser extent than in ByErSp.Eun. The top shell Calliostoma zizyphinum is often recorded as present.

Situation

CarSp.PenPor probably occurs above PhaAxi in shallower water where the exposure of the coast ensures that there is more water mixing due to wave action. Deeper down, this effect is attenuated, allowing PhaAxi biotope to develop.

Temporal variation

Axinella dissimilis tends to grow extremely slowly.

Similar biotopes

CR.MCR.EcCr.CarSp.PenPcomThis biotope occurs under similar conditions as PhaAxi, although it tends to be found over a shallower depth range. Although high abundances of C. smithii are recorded in both these biotopes, CarSp.PenPcom has a less diverse sponge fauna than PhaAxi. The latter in particular is characterised by a diverse range of erect branching sponges. E. verrucosa is also occasionally found in PhaAxi.
CR.HCR.XFa.ByErSp.SagThis biotope occurs on extremely exposed to moderately exposed coasts, subject to moderately strong tides. ByErSp.Sag also occurs over a shallower depth band. ByErSp.Sag has a more restricted range of sponges compared to PhaAxi. However, there is usually a more diverse range of hydroid and bryozoan 'turf-forming' species in ByErSp.Sag. Both biotopes occur mainly around the west coast of Ireland.
CR.HCR.XFa.ByErSp.EunThis biotope occurs under similar wave-exposure conditions as PhaAxi, but is found in sites subject to moderately strong tidal streams. ByErSp.Eun is found much shallower than the deeper PhaAxi, with a mean depth of 20m to 24m, although typically found on the same substratum. E. verrucosa is very abundant in this biotope, although it is still present in PhaAxi. It is the absence of significant numbers of erect sponges that distinguishes this biotope from PhaAxi.

Characterising Species

Taxa Frequency Typical Abundance % Contribution to similarity
Pachymatisma johnstonia O 3
Tethya aurantium O 1
Polymastia boletiformis F 3
Suberites carnosus O 2
Stelligera rigida O 2
Stelligera stuposa F 3
Cliona celata F 4
Axinella dissimilis O 2
Axinella infundibuliformis F 4
Phakellia ventilabrum F 2
Hemimycale columella O 1
Haliclona viscosa F 3
Dysidea fragilis O 3
Sertularella gayi O 2
Nemertesia antennina O 2
Nemertesia ramosa O 1
Alcyonium digitatum F 3
Alcyonium glomeratum F 2
Eunicella verrucosa O 1
Corynactis viridis F 2
Caryophyllia smithii F 6
Calliostoma zizyphinum O 3
Porella compressa F 4
Pentapora foliacea F 2
Parasmittina trispinosa F 2
Luidia ciliaris O 2
Henricia oculata O 3
Stichastrella rosea O 1
Marthasterias glacialis O 2
Echinus esculentus O 3
Holothuria forskali F 4
Aslia lefevrei O 1

Example photographs of biotope


PhaAxi: Sponges Phakellia ventilabrum and Axinella dissimilis on very deep circalittoral rock., Kilkieran Bay, Co. Galway, Bernard Picton, © JNCC
Click on an image for a larger view


Version 15.03 of the classification adds a deep-sea section to version 04.05; therefore superseding version 04.05, 97.06 and 03.02.

This online classification should be cited as:

JNCC (2015) The Marine Habitat Classification for Britain and Ireland Version 15.03 [Online]. [Date accessed]. Available from: jncc.defra.gov.uk/MarineHabitatClassification

Information from the shallower section (up to sublittoral sediment, taken from Version 04.05) be cited as the report accompanying Version 04.05, as follows:

CONNOR, D.W., J.H. ALLEN, N.GOLDING, K.L.HOWELL, L.M. LIEBERKNECHT, K.O. NORTHEN AND J.B. REKER (2004) The Marine Habitat Classification for Britain and Ireland Version 04.05. In: JNCC (2015) The Marine Habitat Classification for Britain and Ireland Version 15.03 [Online]. [Date accessed].
Available from: jncc.defra.gov.uk/MarineHabitatClassification
ISBN 1 861 07561 8


Information from the deep-sea section (added in March 2015) should be cited as the report accompanying the deep-sea section, as follows:

PARRY, M.E.V., K.L. HOWELL, B.E. NARAYANASWAMY, B.J. BETT, D.O.B. JONES, D.J. HUGHES, N. PIECHAUD, T.D. NICKELL, H. ELLWOOD, N. ASKEW, C. JENKINS and E. MANCA (2015) A Deep-sea Section for the Marine Habitat Classification of Britain and Ireland. JNCC report 530. In: JNCC (2015) The Marine Habitat Classification for Britain and Ireland Version 15.03 [Online]. [Date accessed].
Available from: jncc.defra.gov.uk/MarineHabitatClassification
ISSN 0963 8901