Description of biotope or habitat type
Semibalanus balanoides and Littorina spp. on exposed to moderately exposed eulittoral boulders and cobbles
Physical habitat description
|Full (30-35 ppt)
|Exposed, Moderately exposed
|Boulders; cobbles; pebbles
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.
- 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.
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 Ulva 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 Steromphala cineraria and Steromphala umbilicalis can, on more sheltered shores, be found among the seaweeds or underneath the boulders. The barnacle Austrominius modestus is present on some shores.
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).
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.
|Relative importance of taxon for defining this community (%)
|Typical abundance - SACFOR scale
|% of core records where taxon was recorded
Similar biotopes or habitat types
Classification history of this biotope or habitat type