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Marine Habitat Classification

Description of biotope or habitat type

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   Hydroids, ephemeral seaweeds and Littorina littorea in shallow eulittoral mixed substrata pools

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed, Sheltered
Tidal streams
Substratum Cobbles; pebbles; gravel; sand
Zone Eulittoral
Depth Band Mid shore
Other Features Rockpool or standing water

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.Rkp.H Hydroids, ephemeral seaweeds and <I>Littorina littorea</I> in shallow eulittoral mixed substrata pools

  • 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.


Shallow pools on mixed cobbles, pebbles, gravel and sand characterised by abundant hydroids. Species present may include Obelia geniculata, O. dichotoma, O. longissima, Sertularia cupressina, Tublaria indivisa and Thuiaria thuja. The difficulty in identifying hydroids suggests many more species may be also be present. Other species typically found in this biotope include ephemeral green algae (Ulva spp. and Ulva sp.), red algae (Chondrus crispus and Coralline algae) and the winkle Littorina littorea. Within the pools, patches of sand may be occupied by the lugworm Arenicola marina and sand mason worms Lanice conchilega. These pools are often associated with mussel beds (MytX), with Mytilus edulis frequently recorded within the pools. Barnacles (Semibalanus balanoides and Austrominius modestus) and the keel worm Spirobranchus triqueter may be attached to shells and small stones. Mobile species typical of rock pool habitats, such as Crangon crangon and Pomatoschistus minutus will also be found within the pool.


No situation data available.

Temporal variation

No temporal data available.

Characterising species

Taxon Typical abundance - SACFOR scale % of core records where taxon was recorded
Arenicola marina 21-40%
Austrominius modestus Frequent 41-60%
Carcinus maenas Rare 41-60%
Chondrus crispus Occasional 41-60%
Corallinaceae Frequent 41-60%
Crangon crangon 21-40%
Fucus vesiculosus Rare 21-40%
Hydrozoa Abundant 81-100%
Lanice conchilega Occasional 41-60%
Littorina littorea Common 41-60%
Mytilus edulis Abundant 61-80%
Obelia longissima Common 21-40%
Semibalanus balanoides Frequent 41-60%
Spirobranchus triqueter Rare 21-40%
Ulva Rare 61-80%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
1996 (6.95) RKP.H

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