Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA3.36 Faunal communities on variable or reduced salinity Atlantic infralittoral rock

Faunal communities on variable or reduced salinity Atlantic infralittoral rock

Quick facts

Red List habitat type code NEAA3.36
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)


The extent of rocky habitat in rias, sea-lochs and estuaries can range from a narrow strip restricted to the top of the shore to littoral reef structures extending to the subtidal. Rocky habitats in these sheltered inlets are typically located in low wave energy environments with reduced salinity, subjected to accelerated tidal streams with increased turbidity and siltation. The associated communities are adapted to these conditions and consequently their composition and character is different to that found on similar substrata on the open coast. Estuarine rocky habitats often display a transition of community types down the length of an estuary, reflecting the different environmental conditions i.e. those at the upper ends of estuaries being specific to ultra-sheltered and low salinity, grading to communities similar to open coast rock communities towards the mouth of estuaries.

At the most diverse end of the scale this habitat may support a rich and exceptionally abundant sessile epibiota of anemones (e.g. Metridium senile and Diadumene sincta), filter feeding sponges (e.g. Halichondria panacea, Hymeniacidon perleve, Haliclona oculata, Raspalia spp., Suberties spp. and Stelligera spp.), bryozoans (e,g, Alcyonidium digitata, Bugula spp.), hydroids (e.g. Sertularella gaudichaudi, Tubularia spp.) and ascidians (e.g. Ascidiella aspersa and Dendrodoa grossularia). Seaweed dominated biotopes are generally poorly developed or absent. In some sea lochs dense mussel Mytilus edulis beds develop in tide-swept channels, whilst upper estuarine rocky habitats in the rias may support particular brackish-water tolerant faunas.

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.

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

Threat status

Synthesis of Red List assessment

This habitat does not have a small natural range nevertheless, because of the lack of quantitative data on extent and condition, no assessment of trends in quantity and quality can be made at the present time. For the purposes of Red List assessment it 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
    • Marine and Freshwater Aquaculture
    • Fishing and harvesting aquatic resources
  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Marine water pollution
  • Natural System modifications
    • Human induced changes in hydraulic conditions
  • Climate change
    • Changes in abiotic conditions

Habitat restoration potential

There is insufficient information to determine whether this habitat retains the capacity to recover when severely damaged and if so, over what time scales. Major influences include larval supply, hydrodynamics such as scour and turbidity levels.

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

Current approaches to conservation include the regulation of potentially damaging activities in Marine Protected Areas and through integrated coastal zone management schemes. General measures applied to large areas such as those which improve or maintain good water quality across the watershed are also beneficial.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • 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 >50,000 unknown unknown There is insufficient information for accurate calculation of EOO and AOO.
EU28+ unknown unknown There is insufficient information for accurate calculation of EOO and AOO.
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
Phone: +45 3336 7100