Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA1.32 Fucoids on variable salinity Atlantic littoral rock

Fucoids on variable salinity Atlantic littoral rock

Quick facts

Red List habitat type code NEAA1.32
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)


Blankets of fucoid seaweeds, dominating sheltered to extremely sheltered rocky shores with variable salinity, such as sea loch or estuaries. The extent of rocky habitat in estuaries can range from a narrow strip restricted to the top of the shore to littoral reef structures extending to the subtidal, particularly in rias. The topography of estuarine rocky shores also varies from flat and gently sloping to rugged reefs and large boulders with many microhabitats.

Rocky habitats in estuaries are typically located in low wave energy environments with reduced salinity, and experience accelerated tidal streams with increased turbidity and siltation. The communities present 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 to communities similar to open coast rock communities towards the mouth of estuaries.  The wrack Pelvetia canaliculata occurs on the upper shore, with  Fucus spiralis  below. The middle shore is dominated by vast areas of  Ascophyllum nodosum, Fucus vesiculosus, or a mixture of both. Fucus serratus covers lower shore bedrock and boulders. Fucus ceranoides can be found on extremely sheltered shores with variable or low salinity as it is more tolerant of reduced salinity than the other fucoids, so tends to replace Fucus spiralis, Fucus vesiculosus and Ascophyllum nodosum towards the upper reaches of estuaries and sea lochs. This biotope may, however, still contain other fucoids, although Fucus ceranoides always dominates.

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. Dominance of fucoids (cover or biomass ratios of fucoids to other macroalgae) or penetration of fucoids along the salinity gradient is used in some countries as a Water Framework Directive parameter for assessing ecological status.

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. Local and/or seasonal factors often exert a substantial influence on intertidal habitats making it difficult to distinguish any long-term trend across the region. This is complicated further because differences between localities are often linked to differences in geographical latitude and, therefore, to differences in climatic traits like temperature and/or ice cover.
Where this habitat has been studied in detail some trends in quantity and quality have been reported over various time scales however, there is insufficient information to provide an overall estimate of historical, recent and possible future trends in quantity and quality.
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 due to lack of information on 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

  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Marine water pollution
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Removal of sediments (mud...)
    • Estuarine and coastal dredging
    • Siltation rate changes, dumping, depositing of dredged deposits
    • Sea defense or coast protection works, tidal barrages
  • Climate change
    • Changes in abiotic conditions
    • Wave exposure changes
    • Sea-level changes

Habitat restoration potential

This habitat will not have any capacity to recover if the rocky substrate on which it depends is removed, permanently submerged or smothered with soft sediment. If not, and the pressures which caused the damage are removed, recovery times will depend on availability and suitable conditions for the settlement of the characteristic species of algae.

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

Conservation and management of this habitat need to be integrated into the management of the sheltered inlets in which it occurs. This includes the planning and regulation of activities like coastal works, the discharge of hazardous substances, the establishment of nitrate sensitive zones, specifications relating to the dredging of navigational channels and dredge spoil disposal.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to marine habitats
    • Other marine-related measures
  • Measures related to spatial planning
    • Other marine-related measures
  • Measures related to urban areas, industry, energy and transport
    • Urban and industrial waste management


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 348,779 251 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+ 251 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
Phone: +45 3336 7100