Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA4.31 Ascidian/Brachiopod communities on Atlantic sheltered upper circalittoral rock

Ascidian/Brachiopod communities on Atlantic sheltered upper circalittoral rock

Quick facts

Red List habitat type code NEAA4.31
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 type occurs on the wave-sheltered, circalittoral bedrock and boulders subject to weak tidal streams. The biotopes within this complex are characterised by brachiopod and ascidian communities.

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. for protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis.


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

Threat status

Synthesis of Red List assessment

Detailed information on the abundance and extent of this habitat is lacking but survey information reveals that it has a widespread distribution (e.g. west coast of Ireland, west coast of Scotland and the Gullmarsfjorden, Sweden) but very localised occurrence for the associated biotopes with brachiopods. There is a lack of information on the overall quantity and quality of this habitat including any historical or recent trends however,examples of the habitat have been observed and recorded in shallow (<50m) locations for many (>30) years and remain characteristic of those locations.
This habitat has a large EOO and AOO, and therefore qualifies as Least Concern under criterion B. However the habitat is assessed as Data Deficient both at the EU 28 and EU 28+ levels because of the lack of information area covered and on any trends in quantity and quality.
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
    • Marine and Freshwater Aquaculture
    • Intensive fish farming, intensification
  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Nutrient enrichment (N, P, organic matter)
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Siltation rate changes, dumping, depositing of dredged deposits

Habitat restoration potential

The overall capacity for this habitat to recover after it has been severly damaged is unknown. Characteristic species such as Antedon bifida, Nemertesia ramosa, large solitary ascidians and Clavelina lepadiformis have a high intolerance to substratum loss, smothering, increases in water flow rate as well as abrasion and physical disturbance and displacement. However, they are species that re-colonise rapidly. Of more concern are the associated biotopes characterised by brachiopods which are localized as the brachiopod species may take some time to recover from disturbance/loss. The MarLIN sensitivity review suggests that the associated biotope ' A4.314 Neocrania anomala and Protanthea simplex on sheltered circalittoral rock' has a ‘moderate’ capacity for recovery following damage by some physical and other 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

No conservation and management measures that specifically target this habitat have been identified however it is present within some Marine Protected Areas and can therefore benefit from associated measures such as those which limit potentially damaging activities e.g. by zoning fishing activities, setting limits of activities such as dredging which increase turbidity, not allowing fish farms nearby and regulating coastal development. The location of the associated biotope ' A4.314 Neocrania anomala and Protanthea simplex on sheltered circalittoral rock' should also be taken into account in ecological impact assessments and subsequent licensing of activities.

List of conservation and management needs

  • Measures related to marine habitats
    • Other marine-related measures
  • Measures related to spatial planning
    • Other marine-related measures
    • Establish protected areas/sites


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 Unknown Unknown
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 1,210,154 483 >2,100 The area estimate for this habitat has been derived from a synthesis of EUNIS seabed habitat geospatial information for the European Seas but is recognised as being an underestimate.
EU28+ >483 >2,100 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)
Kongens Nytorv 6
1050 Copenhagen K
Phone: +45 3336 7100