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Marine Habitat Classification


Description of biotope or habitat type

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   Chthamalus spp. on exposed upper 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 rock

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.Cht <I>Chthamalus</I> spp. on exposed upper 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. Patches of the black lichen Verrucaria maura and the green seaweed Enteromorpha intestinalis may be present, though in low abundance (Occasional). Shaded vertical littoral fringe and upper eulittoral bedrock may be characterised by the shade-tolerant red seaweeds Catenella caespitosa, Bostrychia scorpioides and/or Lomentaria articulata. Where the turf of C. caespitosa is well established, barnacles are rare. Geographical variation: 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 (Sem). C. montagui is better adapted to resist desiccation and, therefore, extends further up the shore. In the south-west Chthamalus spp. can be the dominant barnacles throughout the eulittoral zone.

Situation

Cht.Cht is found below the black lichen Verrucaria maura (Ver.B or Ver.Ver) on very exposed shores. It is found above the mussel Mytilus edulis and barnacles 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 the 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 29 Abundant 81-100 %
Chthamalus stellatus 7 Common 41-60 %
Semibalanus balanoides 7 Frequent 41-60 %
Patella vulgata 19 Common 81-100 %
Littorina 2 Common 21-40 %
Littorina saxatilis 11 Frequent 61-80 %
Melarhaphe neritoides 3 Common 21-40 %
Mytilus edulis 6 Occasional 61-80 %
Enteromorpha intestinalis 2 Frequent 21-40 %
Verrucaria maura 2 Frequent 21-40 %

Similar biotopes

LR.FLR.Lic.Ver.Ver
Occurs in the littoral fringe above the Cht.Cht biotope. The barnacles C. montagui and S. balanoides and limpets P. vulgata are sparse (all Occasional) while V. maura occurs at a higher abundance (Abundant).

LR.HLR.MusB.Cht.Lpyg
Found especially in the south. Lichina pygmaea forms a distinct band, often with the bivalve Lasaea adasoni embedded in the thalli. The species composition is similar though red and green seaweeds such as Corallinaceae and Enteromorpha spp. are not present.

LR.HLR.MusB.Sem.FvesR
Occurs in the mid eulittoral zone on slightly less exposed shores. It notably lacks Chthamalus spp. and is dominated by a higher abundance of S. balanoides and the whelk Nucella lapillus. Usually, a sparse flora of seaweeds is present including the wrack Fucus vesiculosus and the green seaweed Enteromorpha spp.

Biotope history

Classification Habitat code
97.06 ELR.BPat.Cat in part
97.06 ELR.BPat.Cht in part

Photos

LR.HLR.MUSB.Cht.Cht Chthamalus spp. on exposed upper eulittoral rock, Trebetherick. Keith Hiscock © JNCC
LR.HLR.MUSB.Cht.Cht Chthamalus spp. on exposed upper eulittoral rock, Trebetherick. Keith Hiscock © JNCC
LR.HLR.MUSB.Cht.Cht Chthamalus spp. on exposed upper eulittoral rock, Cornwall. Kate Northen © JNCC
LR.HLR.MUSB.Cht.Cht Chthamalus spp. on exposed upper eulittoral rock, Cornwall. Kate Northen © JNCC

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