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Marine Habitat Classification

Description of biotope or habitat type

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   Balanus crenatus and Tubularia indivisa on extremely tide-swept circalittoral rock

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Extremely exposed, Very exposed, Exposed, Moderately exposed, Sheltered, Very sheltered, Extremely sheltered
Tidal streams Very strong (>6 kn), Strong (3-6 kn)
Substratum Bedrock, boulder, cobble
Zone Circalittoral - lower, Circalittoral - upper
Depth Band 0-5 m, 5-10 m, 10-20 m, 20-30 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.FaT.BalTub <I>Balanus crenatus</I> and <I>Tubularia indivisa</I> on extremely tide-swept 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.


This biotope typically occurs on upward-facing, extremely tide-swept, circalittoral bedrock, boulders and cobbles found in a broad spectrum of wave-exposures. It is characterised by a few species that are capable of maintaining a foothold in strong tides. These species either form a flat, adherent crust in the case of the barnacle Balanus crenatus, or have strong attachment points and are flexible, bending with the tide, such as the turf of the hydroid Tubularia indivisa. Other species able to tolerate these very strong tides, or just situated slightly out of the main force of the current, include the sponge Halichondria panicea, the robust hydroid Sertularia argentea and current-tolerant anemones such as Cylista elegans, Urticina felina and Metridium senile. Mobile species such as the starfish Asterias rubens, the crab Cancer pagurus and the whelk Nucella lapillus may also be present.


This biotope is typically occurs in deep, very tide-swept straights, sounds and narrows with a bedrock/boulder/cobble slope. Kelp forest (LhypT) occurs in shallower water.

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
Balanus crenatus 28 Abundant 81-100%
Tubularia indivisa 18 Frequent 81-100%
Cylista elegans 10 Frequent 61-80%
Asterias rubens 7 Occasional 61-80%
Cancer pagurus 5 Occasional 61-80%
Sertularia argentea 5 Frequent 41-60%
Urticina felina 4 Occasional 61-80%
Alcyonidium diaphanum 3 Occasional 41-60%
Metridium senile 3 Occasional 41-60%
Bryozoa 2 Occasional 41-60%
Flustra foliacea 2 Occasional 41-60%
Halichondria panicea 1 Common 21-40%
Nucella lapillus 1 Common 21-40%

Similar biotopes or habitat types

This biotope occurs under similar conditions to CR.HCR.FaT.BalTub although it tends to be found more on steep and vertical faces. CR.HCR.FaT.CTub.CuSp contains a more diverse range of sponges, bryozoans and ascidians than CR.HCR.FaT.BalTub. They both contain dense carpets of the robust hydroid T. indivisa.

This biotope occurs under similar wave-exposed conditions to CR.HCR.FaT.BalTub, but is subject to slightly weaker tides, which is perhaps reflected in the greater abundance of Alcyonium digitatum. Both sub-biotopes have a similarly impoverished epifauna, although CR.HCR.FaT.CTub.Adig has a slightly more diverse range of sponges.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) CR.ECR.BS.BalTub


CR.HCR.FAT.BalTub Balanus crenatus and Tubularia indivisa on extremely tide-swept circalittoral rock, S end, Kyle Rhea, Skye. Sue Hiscock© JNCC
CR.HCR.FAT.BalTub Balanus crenatus and Tubularia indivisa on extremely tide-swept circalittoral rock, S end, Kyle Rhea, Skye. Sue Hiscock© JNCC

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