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.HLR.MusB.MytB recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Marine natural heritage importance

Listed under EC Habitats Directive
National importance Common
Habitat Directive feature (Annex 1) Reefs
Large shallow inlets and bays

Biotope importance

Suspension feeding Mytilus beds can deplete the seston (organic particulates) available downstream of them and are probably important in energy flow within the wider ecosystem (Holt et al., 1998). Dense beds of bivalve suspension feeders increase turnover of nutrients and organic carbon in estuarine (and presumably coastal) environments by effectively transferring pelagic phytoplanktonic primary production to secondary production (pelagic-benthic coupling) (Dame, 1996). Although, mussel abundance in this biotope does not constitute a bed, in combination with abundant suspension feeding barnacles, the biotope is probably of similar importance in the local ecosystem.

Eggs, larvae and other reproductive propagules (e.g. algal spores) are probably an important food source for zooplankton, and subtidal epifauna. The Mytilus edulis patches probably also provide refuges from predation and environmental extremes for other species (see habitat complexity).

Mytilus species are important food sources for birds, and Mytilus is a staple food for oystercatchers and eider ducks. Oystercatchers also feed on limpets. While not as important to birds as mussel beds in sedimentary habitats (Holt et al., 1998), the biotope probably provides an important feeding area for local resident populations of oystercatchers.

Fish and crustaceans migrating into the intertidal zone to feed as the tide rises or emerging from tide pools, are important predators of rocky shore species. Corkwing wrasse Crenilabrus melops rely heavily on the intertidal, whilst resident blennies are predators of barnacles especially. Nucella lapillus is preyed on by numerous birds, however, the dogwhelk is not considered to be an important food source, except where alternative food sources are absent (Crothers, 1985).


Small, rocky shore mussel patches exemplified by this biotope are probably not subject to large scale exploitation. However, Holt et al. (1998) noted that small, accessible mussel beds may be exploited locally by anglers for bait. For example, a small bed close to a road on Anglesey was almost eliminated by anglers and bait diggers over a period of years (see sensitivity; Holt et al., 1998).

Patella vulgata is occasionally harvested by hand, without regulation, for human consumption and may result in changes in the community structure (see sensitivity). Few other species are likely to be subject to exploitation.

Rocky shores are widely exploited for a range of recreational uses including rock pooling, angling and as a resource for students and scientific researchers. Trampling has been shown to have a significant impact on community structure (see sensitivity).

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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 26/11/2015]. Available from: <>