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Marine Habitat Classification


Description of biotope or habitat type

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   Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Extremely exposed
Tidal streams
Substratum Bedrock
Zone Eulittoral - upper, Littoral fringe - lower
Depth Band
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.HLR.FR.Fdis <I>Fucus distichus</I> and <I>Fucus spiralis</I> f. <I>nana</I> on extremely exposed upper shore 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

Extremely exposed gently or steeply sloping upper shore bedrock which supports a mixture of the wracks Fucus distichus and Fucus spiralis f. nana, the latter often at the top of the zone. On some sites F. distichus dominates and F. spiralis is not present. Other seaweeds normally found on exposed coasts are common in this biotope. These include ephemeral species such as the foliose red Porphyra umbilicalis and the green Enteromorpha spp. The winkles Melarhaphe neritoides and Littorina saxatilis can be found grazing on the bedrock or on the fucoids, while red crusts of Hildenbrandia rubra and the mussel Mytilus edulis are restricted to moist cracks and crevices. A sparse covering of the black lichens Verrucaria maura and Verrucaria mucosa can be found in the upper part of this biotope competing for space with barnacle Semibalanus balanoides and the limpet Patella vulgata. This biotope is very rare and restricted to the far north and west coasts.

Situation

This mixed band of F. distichus and F. spiralis f. nana is generally found between the Verrucaria maura and Porphyra spp. zone (Ver.Ver or Ver.B) above, and the M. edulis and barnacle zone below (MytB). It may also occur above a red algal zone consisting of Mastocarpus stellatus as recorded on Barra.

Temporal variation

Due to the occurrence of this biotope on very exposed coasts a certain amount of fluctuation between this biotope and the Ver.B biotope from year to year is to be expected. More information is required to validate this hypothesis. There can be seasonal fluctuations in the density of ephemeral green algae.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Semibalanus balanoides 7 Occasional 81-100 %
Patella vulgata 11 Frequent 81-100 %
Littorina 3 Common 61-80 %
Littorina saxatilis 5 Common 41-60 %
Melarhaphe neritoides 7 Common 41-60 %
Mytilus edulis 4 Occasional 61-80 %
Porphyra umbilicalis 6 Frequent 61-80 %
Hildenbrandia rubra 5 Common 41-60 %
Corallinaceae 3 Frequent 41-60 %
Fucus distichus 5 Frequent 61-80 %
Fucus spiralis 7 Common 61-80 %
Enteromorpha intestinalis 19 Common 81-100 %
Verrucaria maura 7 Frequent 61-80 %
Verrucaria mucosa 2 Frequent 21-40 %

Similar biotopes

LR.FLR.Eph.Ent
Occurs over a wide range of wave exposures and from the supralittoral to the upper eulittoral zone on freshwater influenced or unstable rock. Brown seaweeds including the wracks Pelvetia canaliculata, F. spiralis and F. distichus are not present, while different species of Enteromorpha dominate this biotope.

Biotope history

Classification Habitat code
6.95 LRK.FDIS

Photos

LR.HLR.FR.Fdis Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock, Berneray, Barra. David Connor © JNCC
LR.HLR.FR.Fdis Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock, Berneray, Barra. David Connor © JNCC
LR.HLR.FR.Fdis Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock, The Rib, Fogla Skerry, Shetland. Keith Hiscock © JNCC
LR.HLR.FR.Fdis Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock, The Rib, Fogla Skerry, Shetland. Keith Hiscock © JNCC
LR.HLR.FR.Fdis Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock, Eynhallow Island, Eynhallow Sound. Sue Scott © JNCC
LR.HLR.FR.Fdis Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock, Eynhallow Island, Eynhallow Sound. Sue Scott © JNCC

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