Description of biotope or habitat type
Mytilus edulis and barnacles on very exposed eulittoral rock
Habitat (physical) description
|Salinity||Full (30-35 ppt)|
|Wave exposure||Very exposed, Exposed|
|Other Features||Also occurs on vertical and steep bedrock on moderately exposed shores|
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.
On very exposed to exposed rocky shores the eulittoral zone, particularly the mid and lower shore, is typically characterised by patches of small individuals of the mussel Mytilus edulis interspersed with patches of the barnacle Semibalanus balanoides and individuls of the limpet Patella vulgata. Amongst the mussels small individuals of red seaweeds including Ceramium spp., Corallina officinalis and Mastocarpus stellatus can be found. The foliose red seaweeds Porphyra umbilicalis and Palmaria palmata are commonly found as epiphytes on M. edulis where they can form luxuriant growths. The abundance of the red seaweeds generally increases down the shore and in the lower eulittoral they may form a distinct zone in which mussels or barnacles are scarce (FR, Coff.Coff or Him). Where M. edulis occurs on steep rock, red seaweeds are scarce and restricted to the lower shore. The whelk Nucella lapillus and a few winkles such as Littorina spp. can occur where cracks and crevices provide a refuge in the rock. Fucoids are generally absent, although some non-vesiculate Fucus vesiculosus may occur where the shore slopes more gently. This biotope also occurs on steep moderately exposed shores which experience increased wave energy.
MytB is generally found above a zone of either mixed turf-forming red seaweeds (FR), Himanthalia elongata (Him) or above the sublittoral fringe kelp Alaria esculenta (Ala) zone. Above MytB there may be a Verrucaria maura zone (Ver.Ver), a V. maura and sparse barnacle zone (Ver.B), often with P. umbilicalis or a denser barnacle and limpet zone (Sem; FvesB). In addition, patches of lichen Lichina pygmaea with the barnacle Chthamalus montagui (Cht.Cht) may also occur above this biotope, particularly on southern shores.
Severe winter storms can cause periodic removal of this mussel and barnacle community.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Semibalanus balanoides||24||Common||81-100 %|
|Patella vulgata||19||Common||81-100 %|
|Nucella lapillus||5||Frequent||41-60 %|
|Mytilus edulis||32||Abundant||81-100 %|
|Porphyra umbilicalis||5||Frequent||41-60 %|
|Corallina officinalis||2||Occasional||41-60 %|
|Mastocarpus stellatus||1||Occasional||21-40 %|
|Ceramium shuttleworthianum||1||Occasional||21-40 %|