Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA4.24 Mussel beds on moderate energy Atlantic circalittoral rock

Mussel beds on moderate energy Atlantic circalittoral rock

Quick facts

Red List habitat type code NEAA4.24
Threat status
Europe Data Deficient
EU Data Deficient
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This habitat occurs on moderately wave-exposed upper circalittoral bedrock subject to strong or moderately strong tidal streams. Mussels Mytilus edulis or Musculus discors can form dense beds, to the exclusion of other species, on the upper faces of bedrock, boulders and mixed substrata. The Musculus biotope occurs in much more wave sheltered and silted situations. There may also be an associated layer of pseudofaeces, forming a thick, silty matrix. 

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 over time.

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. The overall quality and continued occurrence of this habitat is, however, largely dependent on the presence of Mytilus edulis or Musculus discors which creates the biogenic structural complexity on which the characteristic associated communities depend. The density and the maintenance of a viable population of this species is a key indicator of habitat quality, together with the visual evidence of presence or absence of physical damage. However, beds of Mytilus edulis at least may disappear (most likely because of predation by starfish) but are likely to re-colonise at some time in the future (which may be several years) dependent on larval recruitment. 

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

Threat status

Synthesis of Red List assessment

The available information on the occurrence of this habitat is limited. The existing data suggests that it could potentially be considered Near Threatened under Criterion B if there were grounds for believing that this habitat was undergoing a decline in extent or quality. There are, however, no data on the present status or trends of this habitat and the accuracy of the mapping data cannot be verified at this time. This habitat is therefore considered to be Data Deficient for both the EU 28 and EU 28+.
Red List Category Red List Criteria
Data Deficient -
Red List Category Red List Criteria
Data Deficient -

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
    • Professional active fishing
    • Benthic or demersal trawling
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Siltation rate changes, dumping, depositing of dredged deposits
    • Dumping, depositing of dredged deposits
    • Other siltation rate changes

Habitat restoration potential

Mussels, as a generalisation, are considered to have a strong ability to recover from natural disturbance due to high production rates. The more firmly attached, stable communities on subtidal rock can have significantly more diverse associated communities (than those on mixed sediments); comprised of typically 50-100 species. Effects of mussel loss may therefore be significant at the community level, particularly as mussels settle preferentially on conspecifics and reduction of adults may reduce subsequent recruitment, although this relationship is poorly understood. Mussels are also likely to build up longer-lived beds on subtidal rock; Mytilus edulis has been reported as reaching 18-24 years in age in the Danish Wadden Sea. The MarLIN sensitivity reviews record the habitat as ‘Moderate’ or ‘low’ sensitivity to several pressures/activities.

Trends in extent

Average current trend in quantity

Unknown Unknown
EU28 EU28+

Trends in quality

Average current trend in quality

Unknown Unknown
EU28 EU28+

Conservation and management needs

This habitat is afforded protection within some Marine Protected Areas. Beneficial management measures include the regulation of fishing methods and the control of any activity which damages or disturbs seabed communities.

List of conservation and management needs

  • Measures related to spatial planning
    • Other marine-related measures
    • Establish protected areas/sites
  • Measures related to hunting, taking and fishing and species management
    • Regulation/Management of fishery in marine and brackish systems


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)
Celtic Seas Present Unknown Unknown Unknown
Greater North Sea
Bay of Biscay and the Iberian Coast

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 >44,447 >10 Unknown Based on a limited data set. EOO amd AOO known to be an underestimate.v
EU28+ >10 Unknown Based on a limited data set. EOO amd AOO known to be an underestimate.v
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)
Kongens Nytorv 6
1050 Copenhagen K
Phone: +45 3336 7100