Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA1.11 Mytilus edulis and/or barnacle communities on wave-exposed Atlantic littoral rock

Mytilus edulis and/or barnacle communities on wave-exposed Atlantic littoral rock

Quick facts

Red List habitat type code NEAA1.11
Threat status
Europe Least Concern
EU Least Concern
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This habitat type is found in the mid- to upper eulittoral on shores that are moderately or very exposed to wave action. It is characterised by bedrock and boulders dominated by the mussel Mytilus edulis, barnacles Chthamalus spp. and/or Semibalanus balanoides and limpets Patella spp. There is much regional variation in the species and zonation of the barnacles. 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. The lichen Lichina pygmaea may be prominent, especially in the south, where it can form distinct patches or even a separate zone among the Chthamalus spp.

With decreasing wave exposure F. vesiculosus is able to survive, gradually replacing the barnacles and P. vulgata biotope. On such moderately exposed shores this habitat may occur on steep and vertical faces, while fucoids dominate the flatter areas. In areas of soft rock (e.g. shales), the barnacles may be scarce or absent and the rock dominated by P. vulgata.

Indicators of quality:

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include: the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change overtime.

There are no commonly agreed indicators of quality for this habitat, although particular parameters may have been set in certain situations e.g. protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis. Indicators which have been developed for the assessment of ecological quality of coastal water bodies for the Water Framework Directive (WFD) that are relevant to this habitat include a consideration of macroalgae species richness, proportions of different taxa of algae present , and the abundace and coverage of the rocky surfaces by typical species. 

Characteristic species
For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

This habitat has a large natural range in the North East Atlantic region extending from the Canaries and Azores in the west to the Skagerrak coast of Sweden in the east. The precise extent is unknown but existing survey data indicate that the thresholds for a threatened category on the basis of restricted geographic distribution are exceeded. Expert opinion is that the quantity and quality of this habitat has most likely been stable over the last 50 years. Known threats are unlikely to affect all localities at once. This habitat has therefore been assessed as Least Concern for both the EU 28 and EU 28+.
Red List Category Red List Criteria
Least Concern
Red List Category Red List Criteria
Least Concern

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Pollution
    • Marine water pollution
    • Oil spills in the sea
  • Climate change
    • Changes in abiotic conditions
    • Temperature changes (e.g. rise of temperature & extremes)
    • Wave exposure changes
    • Sea-level changes
    • Changes in biotic conditions
    • Habitat shifting and alteration
    • Migration of species (natural newcomers)

Habitat restoration potential

This is a very dynamic habitat. Generally, the effects of chronic impacts on this habitat are reversible provided the disturbance is stopped. Recovery from acute impacts is also possible but may take much longer depending on the scale of the impact. Some of the characteristic species (mussels and barnacles) are adept at colonising empty space. Recovery on bare rock can take place rapidly with succession on rocky shores occurring over relatively short time scales in the order of less than 5-10 years depending on the availability of larvae and successful spatfalls. Longer time scales may be needed for recovery for species with low dispersal rates and in certain situations, e.g. oil spills, especially if the rock surface remains contaminated. If limpet population structure and barnacle densities are used as criteria then 15 years may be a more realistic time scale for recovery following oil spills even on exposed rocky shores. Timescales for recovery following the severe winter of 1962-3, where some species and associated communities on rocky shores took almost 40 years to reoccupy their previous range limits indicates that recovery may take even longer.

Trends in extent

Average current trend in quantity

Stable Stable
EU28 EU28+

Trends in quality

Average current trend in quality

Stable Stable
EU28 EU28+

Conservation and management needs

There are limited opportunities and need for specific conservation and management measures directed at this habitat.
More general beneficial measures include pollution control and regulation, development control and contingency plans to be followed in the event of a major pollution incident, survey and monitoring programmes, raised public awareness of their ecological value and vulnerability, representation in marine protected areas and measures to reduce global warming and sea level rise.

List of conservation and management needs

  • Measures related to marine habitats
    • Other marine-related measures
  • Measures related to spatial planning
    • Other marine-related measures


For each habitat a distribution map was produced from a wide variety of sources indicating known and potential occurrences of the habitat in 10x10 km grids within Europe. Occurrences in grid cells were given in two classes: actual distribution from relatively reliable sources (surveys, expert knowledge), and potential distribution based on models or less reliable indicators. Please download the fact sheet to see the map.

Geographic occurrence and trends

Seas Present or presence uncertain Current area of habitat (Km2) Recent trend in quantity (last 50 years) Recent trend in quality (last 50 years)
Bay of Biscay and the Iberian Coast Present unknown Stable Stable
Celtic Seas
Greater North Sea

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 644,989 603 unknown EOO and AOO have been calculated on the available data. Although this data set is known to be incomplete the figures exceed the thresholds for threatened status.
EU28+ 603 unknown EOO and AOO have been calculated on the available data. Although this data set is known to be incomplete the figures exceed the thresholds for threatened status.
AOO = the area occupied by a habitat measured in number of 10x10 km grid cells.
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).

Characteristic species

Not available

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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1050 Copenhagen K
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