Faunal and algal crusts with Pomatoceros triqueter and sparse Alcyonium digitatum on exposed to moderately wave-exposed circalittoral rock

English name: Faunal and algal crusts with Pomatoceros triqueter and sparse Alcyonium digitatum on exposed to moderately wave-exposed circalittoral rock

Quick facts

EUNIS habitat type code A4.2145
Bern Convention Included in a Resolution 4 habitat type at a higher level (A4)

Description (English)

This variant is typically found on the upper faces of exposed and moderately exposed circalittoral bedrock or boulders subjected to moderately strong to weak tidal streams. From afar, the seabed has a rather sparse, grazed appearance, reminiscent of a brittlestar bed after the brittlestars have moved elsewhere. The rocky substratum is generally covered with encrusting red algae and the white, calcareous tubes of the polychaete Pomatoceros triqueter, dotted with the abundant urchin Echinus esculentus. Under closer inspection, Alcyonium digitatum are usually seen attached to the rocky surface underneath rock overhangs and large boulders. Although they may be recorded as abundant or common in some areas, their relatively small size means that their biomass is generally lower than in other biotopes. Sparse clumps of robust hydroids such as Abietinaria abietina are frequently observed, and bryozoan crusts such as Parasmittina trispinosa are occasionally seen. Echinoderms such as the brittlestars Ophiothrix fragilis and Ophiocomina nigra, and the crab Cancer pagurus may be seen within crevices in the boulders/rock whilst the starfish Asterias rubens may be seen on the rock surface. Muddy-gravel patches between boulders (especially within Scottish sealochs) provide a suitable habitat for the anemone Urticina felina. The top shell Gibbula cineraria is occasionally seen grazing on the rock surface. Within this biotope, there is some regional variation. The robust hydroid A. abietina is typically found in higher abundances in northern (Scottish) regions, especially around the Isle of May.
Situation: Above the A4.2145 variant in the infralittoral zone, species such as Alaria esculenta and Laminaria hyperborea are found in more wave exposed sites (A3.111 / A3.113) while species such as Laminaria saccharina may be found above A4.2145 in the more sheltered examples. Due to moderately tide-swept conditions this variant is found in, clean, coarse sediment biotopes are generally found below A4.2145. Typical species found in these coarse sand/gravelly biotopes include Neopentadactyla mixta and Lanice conchilega (A5.44). Where wave exposure increases, this variant tends to change to A4.2122,, dominated by Caryophyllia smithii, Corynactis viridis, encrusting red algae and bryozoan crusts. Where tidal stream and wave-exposure decreases, this variant develops into a similar biotope dominated by encrusting red algae, Echinus esculentus and C.smithii (A4.2146).

Source: EUNIS habitat classification

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Species mentioned in habitat description

Algae Alaria esculenta
Algae Laminaria hyperborea
Algae Laminaria saccharina
Invertebrates Abietinaria abietina
Invertebrates Alcyonium digitatum
Invertebrates Asterias rubens
Invertebrates Cancer pagurus
Invertebrates Caryophyllia smithii
Invertebrates Corynactis viridis
Invertebrates Echinus esculentus
Invertebrates Gibbula cineraria
Invertebrates Lanice conchilega
Invertebrates Neopentadactyla mixta
Invertebrates Ophiocomina nigra
Invertebrates Ophiothrix fragilis
Invertebrates Parasmittina trispinosa
Invertebrates Pomatoceros triqueter
Invertebrates Urticina felina
Species scientific name English common name Species group
Alaria esculenta Algae
Laminaria hyperborea Algae
Laminaria saccharina Algae
Abietinaria abietina Invertebrates
Alcyonium digitatum Invertebrates
Asterias rubens Invertebrates
Cancer pagurus Invertebrates
Caryophyllia smithii Invertebrates
Corynactis viridis Invertebrates
Echinus esculentus Invertebrates
Gibbula cineraria Invertebrates
Lanice conchilega Invertebrates
Neopentadactyla mixta Invertebrates
Ophiocomina nigra Invertebrates
Ophiothrix fragilis Invertebrates
Parasmittina trispinosa Invertebrates
Pomatoceros triqueter Invertebrates
Urticina felina Invertebrates

Other classifications

Classification Code Habitat type name Relationship type
Marine Habitat Classification Britain/Ireland 0405 CR.MCR.EcCr.FaAlCr.Pom Faunal and algal crusts with <I>Pomatoceros triqueter</I> and sparse <I>Alcyonium digitatum</I> on exposed to moderately wave-exposed circalittoral rock source
CORINE Land Cover 5.2.3. Sea and ocean n/a
For relation to plant communities (syntaxa), see Vegetation types

History

Classification Code Habitat type name Relationship type
EUNIS Habitat Classification 200410 A4.2145 Faunal and algal crusts with Pomatoceros triqueter and sparse Alcyonium digitatum on exposed to moderately wave-exposed circalittoral rock same
EUNIS Habitat Classification 200308 A3.6611 Faunal and algal crusts, Echinus esculentus, sparse Alcyonium digitatum, Abietinaria abietina and other grazing-tolerant fauna on moderately exposed circalittoral rock narrower
EUNIS Habitat Classification 200308 A3.661 Faunal and algal crusts with Pomatoceros triqueter and sparse Alcyonium digitatum on exposed to moderately wave-exposed circalittoral rock same
EUNIS Habitat Classification 200202 A3.661 Faunal and algal crusts, Echinus esculentus, sparse Alcyonium digitatum and grazing-tolerant fauna on moderately exposed circalittoral rock same
EUNIS Habitat Classification 199910 A3.661 Faunal and algal crusts, Echinus esculentus, sparse Alcyonium digitatum and grazing-tolerant fauna on moderately exposed circalittoral rock same
MNCR BioMar 97.06 (Britain & Ireland) MCR.GzFa.FaAlC.Abi Faunal and algal crusts, Echinus esculentus, sparse Alcyonium digitatum, Abietinaria abietina and other grazing-tolerant fauna on moderately exposed circalittoral rock same
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