Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA3.22 Kelp and seaweed communities in tide-swept sheltered Atlantic infralittoral rock

Kelp and seaweed communities in tide-swept sheltered Atlantic infralittoral rock

Quick facts

Red List habitat type code NEAA3.22
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 is a species-rich, structurally complex habitat that develops in areas of infralittoral rock sheltered from wave action but exposed to strong tidal streams such as the sheltered narrows and sills of Scottish sea lochs or in Norwegian fjords.  In the sublittoral fringe dense Laminaria digitata is found together with erect seaweeds, sponges, ascidians and bryozoans. Below this, on bedrock and stable boulders a canopy of mixed kelp (primarily Laminaria hyperborea and Saccharina latissima) occurs with foliose red seaweeds, sponges and ascidians. In some situations, for examples on mixed substrata of boulders, cobbles, pebbles and gravel, there may be a reduced kelp canopy of L. hyperborea and S. latissima, but with a rich red seaweed component and maerl at some sites. Where the tide-swept rock occurs in estuarine conditions, the reduced and variable salinity as well as increased turbidity of the water has a significant effect on the biota, limiting the infralittoral zone to very shallow depths. The rock in these situations is characterised by a relatively low abundance of S. latissima with foliose red seaweeds, sponges and ascidians. L. hyperborea is rarely present.

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

Survey information confirms that this habitat has a widespread distribution in the North East Atlantic. It has been studied in detail in some localities however there is insufficient information to determine whether there have been any historical, recent and possible future trends in quantity or 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 because of the lack of information on its area and 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

  • Urbanisation, residential and commercial development
    • Urbanised areas, human habitation
  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Modification of hydrographic functioning, general
    • Modification of water flow (tidal & marine currents)

Habitat restoration potential


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

Controls on activities that change the hydrological regime, such as coastal construction works, tidal energy generation schemes and land claim are important for the conservation of this habitat. These types of measures have been introduced where this habitat occurs both within and outside marine protected areas.

List of conservation and management needs

  • Measures related to marine habitats
    • Other marine-related measures
  • Measures related to spatial planning
    • 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 1,161,730 57 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+ >57 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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