Biodiversity & Conservation

Mytilus edulis and barnacles on very exposed eulittoral rock



Image Anon. - Close view of Mytilus and dense barnacles covering rock surface. Image width ca XX cm.
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Distribution map

LR.ELR.MB.MytB recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland Present on all coasts of the British Isles with the exception of south east England.
National importance Common

Text page icon Description of biotope

For a full description of this biotope including characterizing species, distribution, survey information and references visit JNCC

The eulittoral zone, particularly mid and lower shore zones, of very exposed rocky shores are typically characterized by patches of small mussels Mytilus edulis interspersed with patches of barnacles Semibalanus balanoides. Amongst the mussels small red algae including Ceramium shuttleworthianum, Corallina officinalis, Mastocarpus stellatus and Aglaothamnion spp. can be found. Two red algae in particular, Porphyra umbilicalis and Palmaria palmata, are commonly found on the Mytilus itself and can form luxuriant growths. The abundance of the red algae generally increases down the shore and in the lower eulittoral they may form a distinct zone in which mussels or barnacles are scarce (MLR.R, ELR.Him or ELR.Coff). Where Mytilus occurs on steep rock, red algae are scarce, and restricted to the lower levels. The dog whelk Nucella lapillus and a few littorinid molluscs occur where cracks and crevices provide a refuge in the rock. Fucoids are generally absent, although some Fucus vesiculosus f. linearis may occur where the shore slopes more gently. ELR.MytB is generally found above a zone of either mixed turf-forming red algae (MLR.R), Himanthalia elongata (ELR.Him) or above the sublittoral fringe kelp Alaria esculenta (EIR.Ala). Above ELR.MytB there may be a Porphyra zone (LR.Ver.Por), a Verrucaria maura and sparse barnacle zone (LR.Ver.B) or a denser barnacle and limpet zone (ELR.BPat), often with Porphyra. In addition, patches of Lichina pygmaea with barnacles (ELR.BPat.Lic) may also occur above this biotope, particularly on southern shores. This biotope also occurs on steep moderately exposed shores which experience increased wave crash. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Additional information icon Additional information


This review can be cited as follows:

Tyler-Walters, H. 2002. Mytilus edulis and barnacles on very exposed eulittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/11/2015]. Available from: <>