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Marine Habitat Classification


Description of biotope or habitat type

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   Chthamalus spp. on exposed eulittoral rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Very exposed, Exposed, Moderately exposed
Tidal streams
Substratum Bedrock; large boulders
Zone Eulittoral - mid, Eulittoral - upper
Depth Band Mid shore, Upper shore
Other Features Also on sheltered vertical bedrock

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 LR.HLR.MusB.Cht <I>Chthamalus</I> spp. on exposed eulittoral 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'

Point data based on records in the UK Marine Recorder Snapshot.

Description

Very exposed to moderately exposed upper and mid eulittoral bedrock and boulders characterised by a dense community of barnacles, including Chthamalus montagui, Chthamalus stellatus and Semibalanus balanoides, and the limpet Patella vulgata. Damp cracks and crevices in the rock provide a refuge for small individuals of the mussel Mytilus edulis and the winkles Melarhaphe neritoides and Littorina saxatilis. These crevices can also be occupied by encrusting coralline algae and the anemone Actinia equina. Black patches of the lichen Verrucaria maura may be found in this zone. There is much regional variation in the distribution and zonation of Chthamalus spp. On the west coast Chthamalus spp. dominate the upper eulittoral, often forming a distinct white band above a darker band of S. balanoides in the mid eulittoral zone. C. montagui is better adapted to resist desiccation and, therefore, extends further up the shore. On some shores, particularly in the south-west, Chthamalus spp. is the dominant barnacle throughout the eulittoral zone (Cht.Cht). On other shores, particularly in the south, Lichina pygmaea can form a distinct zone (Cht.Lpyg).

Situation

Cht is found below the black lichen Verrucaria maura (Ver.B or Ver.Ver) on very exposed shores and above the mussel Mytilus edulis and barnacle biotope (MytB). On slightly less exposed shores the wrack Fucus vesiculosus is able to survive and a mixed barnacle and F. vesiculosus biotope may occur (Sem.FvesR) beneath Cht. On such moderately exposed shores Cht may still occur on steep and vertical faces, while fucoids dominate the flatter areas (Sem.FvesR or Fves), though these communities should not be confused with Sem.FvesR. Cht can also occur above Sem. On very sheltered sea lochs in Argyll, West Scotland Chthamalus spp. are unusually abundant in the upper eulittoral zone.

Temporal variation

Unknown.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Actinia equina 2 Occasional 41-60 %
Chthamalus montagui 27 Abundant 81-100 %
Chthamalus stellatus 7 Frequent 61-80 %
Semibalanus balanoides 6 Frequent 41-60 %
Patella vulgata 16 Common 61-80 %
Littorina 3 Common 41-60 %
Littorina saxatilis 14 Frequent 61-80 %
Melarhaphe neritoides 5 Common 21-40 %
Mytilus edulis 5 Occasional 61-80 %
Lichina pygmaea 2 Frequent 21-40 %
Verrucaria maura 2 Frequent 21-40 %

Similar biotopes

Not applicable or unknown.

Biotope history

Classification Habitat code
97.06 ELR.BPat.Cht

Photos

LR.HLR.MUSB.Cht Chthamalus spp. on exposed eulittoral rock, Broadhaven, Dunbar. Jon Davies © JNCC
LR.HLR.MUSB.Cht Chthamalus spp. on exposed eulittoral rock, Broadhaven, Dunbar. Jon Davies © JNCC
LR.HLR.MUSB.Cht Chthamalus spp. on exposed eulittoral rock, Trebetherick. Keith Hiscock © JNCC
LR.HLR.MUSB.Cht Chthamalus spp. on exposed eulittoral rock, Trebetherick. Keith Hiscock © JNCC

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