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IR.MIR.KR.XFoR
Dense foliose red seaweeds on silty moderately exposed infralittoral rock

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Habitat (physical) description

Distribution

 Salinity: Full (30-35 ppt) 
 Wave exposure: Moderately exposed 
 Tidal streams: Moderately strong (1-3 kn) 
 Substratum: Bedrock; boulders & cobbles 
 Zone: Infralittoral 
 Depth Band: 5-10 m, 10-20 m 
 Other Features: In turbid conditions 

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.MIR.KR.XFoR  Dense foliose red seaweeds on silty moderately exposed infralittoral rock
Distribution of habitat IR.MIR.KR.XFoR Dense foliose red seaweeds on silty moderately exposed infralittoral 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

Upward-facing surfaces of shallow, infralittoral bedrock and boulders in areas of turbid water dominated by dense red seaweeds, with the notable absence of kelp. The stable rock, which can be cobbles or boulders but is more typically bedrock, is usually silted. Individual species of foliose red seaweeds such as Plocamium cartilagineum or Calliblepharis ciliata often dominate. Other red seaweeds likely to be present include Phyllophora crispa, Rhodymenia holmesii, Halurus flosculosus, Cryptopleura ramosa, Hypoglossum hypoglossoides, Heterosiphonia plumosa and coralline crusts. The brown seaweed Dictyota dichotoma is sometimes present, although never abundant. This biotope does not generally occur below kelp park but rather occurs on shallow, silted rock on which kelp would normally grow in less turbid conditions. The fauna can be variable but is generally typified by the presence of silt-tolerant animals such as encrusting sponges, particularly Dysidea fragilis and Halichondria panicea, the hydroid Tubularia indivisa, bryozoan crusts and scattered Sabellaria spinulosa and Balanus crenatus. In the summer months the seaweeds can become heavily encrusted with the bryozoan Electra pilosa and the ascidian Molgula manhattensis which can also form dense mats on the rock. The polychaete Lanice conchilega can be present, where sandy and muddy patches occur. Where this biotope occurs on chalk bedrock, such as off the Sussex coast, the piddock Pholas dactylus is often found bored into the rock. This biotope is recorded from the English Channel, off Kent, Sussex and the Isle of Wight. Please notice that individual sites of this biotope can vary significantly in the species composition.

Situation

This biotope generally occurs on discrete bedrock outcrops surrounded by areas of mixed sediment or mobile sand. Off Sussex, it occurs on the horizontal chalk bedrock forming the tops of cliffs (2-3m in height).

Temporal variation

The seaweeds die back in late autumn and summer leaving, silted, coralline-encrusted rock with a sparse fauna of sponges, S. spinulosa and occasional hydroids and bryozoans. The bryozoan Amathia lendigera can also become abundant amongst the seaweeds during the summer months.

Similar biotopes

IR.HIR.KFaR.FoRThis biotope occurs in deeper water below the kelp park with a higher diversity of sponges like H. panicea and D. fragilis.
IR.HIR.KFaR.FoR.DicThis biotope occurs in deeper water below the kelp park with a high abundance of the brown seaweeds Dictyopteris membranacea (Frequent) and D. dichotoma (Common). It also has a higher diversity of sponges like H. panicea and D. fragilis.
SS.SMp.KSwSS.LsacR.CbPbThis biotope occurs on mixed, mobile substrata and is characterised by red seaweeds such as Halarachnion ligulatum, Lomentaria orcadensis, Naccaria wiggii and Compsothamnion thuyoides that thrive in these conditions.

Characterising Species

Taxa Frequency Typical Abundance % Contribution to similarity
Porifera indet crusts R 4
Tubularia indivisa R 2
Lanice conchilega O 3
Amphipoda A 4
Caprellidae C 2
Mytilus edulis P 1
Electra pilosa F 15
Molgula manhattensis R 1
Corallinaceae O 4
Calliblepharis ciliata C 2
Phyllophora crispa O 3
Plocamium cartilagineum F 14
Halurus flosculosus F 11
Heterosiphonia plumosa F 3
Cryptopleura ramosa C 3
Hypoglossum hypoglossoides O 9
Foliose red algae A 5
Dictyota dichotoma O 1

Example photographs of biotope

No characteristic photos currently available. If you are able to provide a photograph of this biotope please contact .


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