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Marine Habitat Classification

Description of biotope or habitat type

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   Ephemeral green or red seaweed communities (freshwater or sand-influenced)

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed, Sheltered, Very sheltered, Extremely sheltered
Tidal streams
Substratum Bedrock; boulders
Zone Littoral fringe - lower, Eulittoral
Depth Band Lower shore, Mid shore, Upper shore
Other Features

Download comparative physical and biological data. The comparative tables enable a rapid comparison of the species composition and principal physical characteristics between a given set of biotopes.

Distribution of habitat LR.FLR.Eph Ephemeral green or red seaweed communities (freshwater or sand-influenced)

  • Records used to define the biotope (core records)
  • Other records assigned to this biotope, marked as 'certain'
  • Other records assigned to this biotope, marked as 'uncertain'

Point data based on records in the UK Marine Recorder Snapshot.


Ephemeral seaweeds on disturbed littoral rock in the lower to upper shore. Dominant green seaweeds include Ulva intestinalis, Ulva lactuca and the red seaweeds Rhodothamniella floridula and Porphyra purpurea. Winkles such as Littorina littorea and Littorina saxatilis, the limpet Patella vulgata and the barnacles Semibalanus balanoides can occur, though usually in low abundance. The crab Carcinus maenas can be found where boulders are present, while the barnacle Austrominius modestus is usually present on sites subject to variable salinity. On moderately exposed shores, the biotope is Ulva spp. on freshwater-influenced or unstable upper shore rock (Ent) or P. purpurea and/or Ulva spp. on sand-scoured mid to lower eulittoral rock (EntPor). Eulittoral mixed substrata subject to variations in salinity and/or siltation characterised by dense blankets of ephemeral green and red seaweeds (EphX), or if the substratum is too mobile or disturbed to support a seaweed community (BLitX). These are biotopes with a low species diversity and the relatively high number of species in the characterising species list are due to a variation in the species composition from site to site, not to high species richness on individual sites.


This biotope complex occurs the splash zone, sometimes on cliff faces, and throughout the main intertidal zone.

Temporal variation

No temporal variation data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Ulva intestinalis 37 Common 61-80%
Austrominius modestus 10 Occasional 21-40%
Littorina littorea 7 Occasional 21-40%
Chlorophyceae 5 Abundant 21-40%
Littorina saxatilis 5 Occasional 21-40%
Carcinus maenas 4 Occasional 21-40%
Patella vulgata 4 Occasional 21-40%
Semibalanus balanoides 3 Occasional 41-60%
Ulva lactuca 3 Occasional 21-40%
Fucus vesiculosus 2 Occasional 21-40%
Rhodothamniella floridula 1 1-20%
Porphyra purpurea 1 1-20%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) LR.LR (part)

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