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Marine Habitat Classification


Description of biotope or habitat type

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


Habitat (physical) 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), Weak (>1 kn)
Substratum Bedrock, boulder, cobble
Zone Circalittoral - lower, Circalittoral - upper
Depth Band 5-10 m, 10-20 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.FluCoAs <I>Flustra foliacea</I> and colonial ascidians on tide-swept moderately 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 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. FluCoAs.SmAs tends to have a high abundance of barnacles, which populate the rocky seabed. The second variant (FluCoAs.Paur) 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, FluCoAs.X is found on mixed substrata and is characterised by a dense hydroid turf growing alongside F. foliacea and other scour-tolerant species.

Situation

No situation data available.

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
Leucosolenia botryoides 1 Frequent 21-40 %
Scypha ciliata 4 Frequent 61-80 %
Cliona celata 3 Occasional 61-80 %
Tubularia indivisa 2 Occasional 41-60 %
Halecium halecinum 2 Frequent 41-60 %
Hydrallmania falcata 1 Occasional 41-60 %
Nemertesia antennina 3 Frequent 61-80 %
Alcyonium digitatum 4 Occasional 81-100 %
Urticina felina 4 Frequent 61-80 %
Balanus crenatus 1 Frequent 41-60 %
Pagurus bernhardus 1 Occasional 41-60 %
Cancer pagurus 3 Occasional 61-80 %
Alcyonidium diaphanum 6 Frequent 81-100 %
Flustra foliacea 7 Frequent 81-100 %
Bugula flabellata 3 Occasional 61-80 %
Bugula plumosa 2 Frequent 41-60 %
Crossaster papposus 3 Occasional 61-80 %
Asterias rubens 8 Frequent 81-100 %
Ophiothrix fragilis 2 Frequent 41-60 %
Clavelina lepadiformis 3 Frequent 61-80 %
Polyclinum aurantium 3 Frequent 41-60 %
Botryllus schlosseri 2 Occasional 61-80 %

Similar biotopes

Not applicable or unknown.

Photos

CR.HCR.XFA.FluCoAs Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock, Sarn Badrig. Sue Hiscock © JNCC
CR.HCR.XFA.FluCoAs Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock, Sarn Badrig. Sue Hiscock © JNCC
CR.HCR.XFA.FluCoAs Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock, Sarn Badrig. Sue Hiscock © JNCC
CR.HCR.XFA.FluCoAs Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock, Sarn Badrig. Sue Hiscock © JNCC
CR.HCR.XFA.FluCoAs Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock, Off St Tudwals island. Keith Hiscock © JNCC
CR.HCR.XFA.FluCoAs Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock, Off St Tudwals island. Keith Hiscock © JNCC

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