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Marine Habitat Classification


Description of biotope or habitat type

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   Rhodothamniella floridula on sand-scoured lower eulittoral rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Exposed, Moderately exposed
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock; boulders
Zone Eulittoral - lower
Depth Band Lower shore
Other Features Sand-scour

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.MLR.BF.Rho <I>Rhodothamniella floridula</I> on sand-scoured lower eulittoral rock

  • 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.

Description

Lower eulittoral and sublittoral fringe bedrock and boulders subject to mild sand-scouring characterised by a canopy of the wracks Fucus serratus or Fucus vesiculosus, beneath which a mat of the sand-binding red seaweed Rhodothamniella floridula occurs. These mats can form distinct areas without F. serratus. The small hummocks of R. floridula also contain a diversity of other red seaweeds tolerant of sand scour, e.g. Palmaria palmata, Chondrus crispus, coralline crusts and Mastocarpus stellatus. The brown seaweed Cladostephus spongiosus or the ephemeral green seaweed Enteromorpha intestinalis, Ulva lactuca or Cladophora rupestris may occur. The hydroid Dynamena pumila can form colonies on the F. serratus fronds. The barnacle Semibalanus balanoides, the limpet Patella vulgata, the anemone Actinia equina and the polychaete Pomatoceros triqueter may be present where bedrock are available along with a few winkles such as Littorina littorea. In addition, polychaetes and amphipods may burrow into the R. floridula mat, while the mussel Mytilus edulis is restricted to small crevices in the bedrock. The species diversity of this biotope is normally low and there can be much variation in the species composition from site to site.

Situation

Above this biotope in sand influenced areas are a community dominated by M. edulis and F. vesiculosus or where the sand scour is more severe, is a biotope dominated by ephemeral seaweeds such as Enteromorpha spp. and the red seaweed Porphyra spp. (EntPor). Below this biotope are biotopes dominated by F. serratus and/or red seaweeds (see Fser variants) or biotopes dominated by kelp such as Alaria esculenta and/or Laminaria digitata (Ala.Ldig).

Temporal variation

Where sand scour is more severe, fucoids and R. floridula may be rare or absent and green ephemeral seaweeds dominate the substratum (EntPor).

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Dynamena pumila 2 Occasional 21-40 %
Actinia equina 1 Occasional 21-40 %
Semibalanus balanoides 7 Occasional 41-60 %
Carcinus maenas 1 Occasional 21-40 %
Patella vulgata 6 Occasional 21-40 %
Littorina littorea 2 Occasional 21-40 %
Mytilus edulis 1 Occasional 21-40 %
Palmaria palmata 3 Occasional 41-60 %
Rhodothamniella floridula 27 Abundant 81-100 %
Corallinaceae 3 Common 41-60 %
Chondrus crispus 2 Frequent 21-40 %
Mastocarpus stellatus 8 Frequent 61-80 %
Cladostephus spongiosus 3 Occasional 41-60 %
Fucus serratus 8 Abundant 61-80 %
Fucus vesiculosus 1 Occasional 21-40 %
Enteromorpha intestinalis 7 Common 41-60 %
Ulva lactuca 6 Occasional 61-80 %
Cladophora rupestris 2 Occasional 21-40 %

Similar biotopes

LR.MLR.BF.Fser
These biotopes occurs on lower shore rock, but lack the sand scour. R. floridula is not usually present in sufficient density to form a mat on the rock.

Biotope history

Classification Habitat code
6.95 LRK.FSE.AUD
96.7 MLR.Aud

Photos

LR.MLR.BF.Rho Rhodothamniella floridula on sand-scoured lower eulittoral rock, Rottingdean, W. Sussex. Kate Northen © JNCC
LR.MLR.BF.Rho Rhodothamniella floridula on sand-scoured lower eulittoral rock, Rottingdean, W. Sussex. Kate Northen © JNCC
LR.MLR.BF.Rho Rhodothamniella floridula on sand-scoured lower eulittoral rock, Longhouton Steel, Boulmer. Jon Davies © JNCC
LR.MLR.BF.Rho Rhodothamniella floridula on sand-scoured lower eulittoral rock, Longhouton Steel, Boulmer. Jon Davies © JNCC
LR.MLR.BF.Rho Rhodothamniella floridula on sand-scoured lower eulittoral rock, Birling Gap-east side, Beachy Head - Seven Sisters. David George © JNCC
LR.MLR.BF.Rho Rhodothamniella floridula on sand-scoured lower eulittoral rock, Birling Gap-east side, Beachy Head - Seven Sisters. David George © JNCC

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