EUNIS habitat classification 2012 amended 2019 > A - Marine habitats > A4 - Circalittoral rock and other hard substrata > A4.1 - Atlantic and Mediterranean high energy circalittoral rock > A4.13 - Mixed faunal turf communities on circalittoral rock > A4.134 - Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock

Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock

English name: Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock

Quick facts

EUNIS habitat type code A4.134
Bern Convention Included in a Resolution 4 habitat type at a higher level (A4)

Description (English)

This biotope typically occurs on the upper faces of moderately tide-swept, moderately wave-exposed circalittoral bedrock or boulders (although a variant is found on mixed substrata). It most frequently occurs between 10-20m water depth. The biotope is exposed to varying amounts of scour (due to nearby patches of sediment) and, as a consequence, is characteristically dominated by dense Flustra folicaea, a range of colonial ascidians and a variety of other scour/silt-tolerant species. In addition to F. foliacea, other bryozoans present in this biotope include Alcyonidium diaphanum, Bugula flabellata and Bugula plumosa. Varying amounts of the soft coral Alcyonium digitatum may be recorded, depending on the amount of scouring which may vary locally. Where scour is a major factor, species such as the scour-tolerant Urticina felina are frequently observed. Hydroids present in this biotope include Nemertesia antennina, Halecium halecium, Tubularia indivisa and Hydrallmania falcata. Other species present include silt-tolerant sponges such as Scypha ciliata, Cliona celata, Leucosolenia botryoides, and the ascidians Clavelina lepadiformis and Botryllus schlosseri. Balanus crenatus may be recorded occasionally on the boulder/rock surface, and the crab Cancer pagurus may be observed finding refuge in crevices and under boulders. More ubiquitous species present include Asterias rubens, Crossaster papposus, Ophiothrix fragilis and Pagurus bernhardus. Three variants of this biotope have been defined. Unit A4.1342 tends to have a high abundance of barnacles, which populate the rocky seabed. The second variant (A4.1341) is characterised by abundant Polyclinum aurantium in addition to F. foliacea, which often incorporates sand grains into itself, giving the crustose appearance of sandy rock nodules. Finally, A4.1343 is found on mixed substrata and is characterised by a dense hydroid turf growing alongside F. foliacea and other scour-tolerant species.

Source: EUNIS habitat classification

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Species mentioned in habitat description

Invertebrates Alcyonidium diaphanum
Invertebrates Alcyonium digitatum
Invertebrates Asterias rubens
Invertebrates Balanus crenatus
Invertebrates Botryllus schlosseri
Invertebrates Bugula flabellata
Invertebrates Bugula plumosa
Invertebrates Cancer pagurus
Invertebrates Clavelina lepadiformis
Invertebrates Cliona celata
Invertebrates Crossaster papposus
Invertebrates Halecium halecium
Invertebrates Hydrallmania falcata
Invertebrates Leucosolenia botryoides
Invertebrates Nemertesia antennina
Invertebrates Ophiothrix fragilis
Invertebrates Pagurus bernhardus
Invertebrates Polyclinum aurantium
Invertebrates Tubularia indivisa
Invertebrates Urticina felina
Species scientific name English common name Species group
Alcyonidium diaphanum Invertebrates
Alcyonium digitatum Invertebrates
Asterias rubens Invertebrates
Balanus crenatus Invertebrates
Botryllus schlosseri Invertebrates
Bugula flabellata Invertebrates
Bugula plumosa Invertebrates
Cancer pagurus Invertebrates
Clavelina lepadiformis Invertebrates
Cliona celata Invertebrates
Crossaster papposus Invertebrates
Halecium halecium Invertebrates
Hydrallmania falcata Invertebrates
Leucosolenia botryoides Invertebrates
Nemertesia antennina Invertebrates
Ophiothrix fragilis Invertebrates
Pagurus bernhardus Invertebrates
Polyclinum aurantium Invertebrates
Tubularia indivisa Invertebrates
Urticina felina Invertebrates

Other classifications

Classification Code Habitat type name Relationship type
Marine Habitat Classification Britain/Ireland 0405 CR.HCR.XFa.FluCoAs <I>Flustra foliacea</I> and colonial ascidians on tide-swept 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 A4.134 Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock same
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