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Marine Habitat Classification


Description of biotope or habitat type

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   Semibalanus balanoides and Littorina spp. on exposed to moderately exposed eulittoral boulders and cobbles


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed
Tidal streams
Substratum Boulders; cobbles; pebbles
Zone Eulittoral
Depth Band Mid shore
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 LR.HLR.MusB.Sem.LitX <I>Semibalanus balanoides</I> and <I>Littorina</I> spp. on exposed to moderately exposed eulittoral boulders and cobbles

  • 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

Large patches of boulders, cobbles and pebbles in the eulittoral zone on exposed to moderately exposed shores colonised by the barnacle Semibalanus balanoides and, on larger rocks, the limpet Patella vulgata. The winkles Littorina littorea and Littorina saxatilis and the whelk Nucella lapillus are typically found in high numbers on and around cobbles and smaller boulders, while the anemone Actinia equina occurs in damp areas between and underneath larger boulders. Between the cobbles and pebbles, the mussel Mytilus edulis occasionally occurs, but always at low abundance, as do the crab Carcinus maenas and gammarid amphipods. Ephemeral green seaweeds such as Enteromorpha intestinalis may cover cobbles and boulders. The foliose red seaweeds Chondrus crispus, Mastocarpus stellatus and Osmundea pinnatifida as well as the wrack Fucus vesiculosus may also occur in low abundance on cobbles and boulders. The top shells Gibbula cineraria and Gibbula umbilicalis can, on more sheltered shores, be found among the seaweeds or underneath the boulders. The barnacle Elminius modestus is present on some shores.

Situation

On exposed shores with large boulders Sem.LlitX is found below the black lichen Verrucaria maura and sparse barnacles biotope (Ver.Ver or Ver.B) and/or below the Chthamalus spp. and P. vulgata biotope (Cht). Below this biotope the Himanthalia elongata dominated biotopes may occur (Him; Coff). On less exposed shores Sem.LlitX can be found above the Fucus serratus biotope on boulders (Fser.Bo).

Temporal variation

Seasonally mobile boulders, cobbles and pebbles are likely to have a sparser coverage of flora and fauna, because the rocks can be subject to turning. Ephemeral green seaweeds can dominate during the summer.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Actinia equina 4 Occasional 41-60 %
Semibalanus balanoides 25 Abundant 81-100 %
Carcinus maenas 2 Occasional 41-60 %
Patella vulgata 15 Common 81-100 %
Littorina littorea 22 Common 81-100 %
Littorina saxatilis 7 Frequent 61-80 %
Nucella lapillus 4 Occasional 41-60 %
Mytilus edulis 5 Occasional 61-80 %
Corallinaceae 1 Occasional 41-60 %
Mastocarpus stellatus 1 Occasional 41-60 %
Fucus vesiculosus 2 Occasional 41-60 %
Enteromorpha intestinalis 1 Occasional 21-40 %

Similar biotopes

LR.HLR.MusB.Sem.FvesR
Occurs at a similar wave exposure in the eulittoral zone, but usually on bedrock. Due to the more stable substrata N. lapillus (Frequent) and P. vulgata (Abundant) are found in higher abundance. L. littorea are not present in high abundance (Occasional) and C. maenas are rare.

LR.HLR.MusB.Sem.Sem
Occurs at a similar wave exposure in the eulittoral zone, but on bedrock shores. This biotope has a lower species diversity and notably lacks A. equina and L. littorea, while L. saxatilis is common. Seaweeds are also usually rare due to wave scourge.

LR.FLR.Eph.BLitX
Occurs on sheltered to extremely sheltered shores with mixed substrata and often with reduced salinity. Large boulders or bedrock are not present. The species diversity and their abundance are impoverished with the notable absence of red seaweeds.

Biotope history

Classification Habitat code
97.06 BLlit in part
6.95 LMXD.BLIT in part

Photos

LR.HLR.MUSB.Sem.LitX Semibalanus balanoides and Littorina spp. on exposed to moderately exposed eulittoral boulders and cobbles, Souter Point, Marsden. Paul Brazier © JNCC
LR.HLR.MUSB.Sem.LitX Semibalanus balanoides and Littorina spp. on exposed to moderately exposed eulittoral boulders and cobbles, Souter Point, Marsden. Paul Brazier © JNCC

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