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Marine Habitat Classification


Description of biotope or habitat type

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   Ascophyllum nodosum on full salinity mid eulittoral mixed substrata


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams
Substratum Mixed cobbles, boulders and pebbles on sediment
Zone Eulittoral - mid
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.LLR.F.Asc.X <I>Ascophyllum nodosum</I> on full salinity mid eulittoral mixed substrata

  • 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

Sheltered to extremely sheltered full salinity mixed substrata (cobbles, boulders and pebbles on sediment) characterised by a canopy formed by a mosaic of the wracks Ascophyllum nodosum and Fucus vesiculosus. The red seaweed Polysiphonia lanosa can often be found as an epiphyte on the A. nodosum. The mussel Mytilus edulis often occurs in clumps, and provides further suitable substrata for the attachment of fucoids and red and green seaweeds such as Polysiphonia spp. and Enteromorpha intestinalis or the barnacle Semibalanus balanoides. Winkles are common and Littorina littorea and Littorina obtusata/mariae may occur in high densities, while species such as the limpet Patella vulgata, the crab Carcinus maenas and the whelk Nucella lapillus may occur on and around the boulders. Gammarids can be found underneath the boulders or among the seaweeds, while tube-forming spirorbids are found on the boulders, shells or on the F. vesiculosus. Infaunal species including the polychaetes Arenicola marina and Lanice conchilega may occur in the sediment between the cobbles.

Situation

A sparse S. balanoides, P. vulgata and L. littorea community (BLitX) can occur above this biotope. On shores with a proportion of smaller cobbles and boulders, large A. nodosum plants become uncommon and F. vesiculosus dominates the canopy (Fves.X). F. vesiculosus also tends to replace A. nodosum in areas with freshwater influence. Below this biotope are either a Fucus serratus dominated biotope (Fserr.X) or a M. edulis dominated biotope (Myt.Myt).

Temporal variation

A. nodosum communities tend to be stable due to longevity of the individual A. nodosum, but because of the mixed substrata some variation in the densities of F. vesiculosus and A. nodosum can be expected.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Spirorbidae 1 Occasional 21-40 %
Semibalanus balanoides 6 Occasional 61-80 %
Gammaridae 1 Frequent 21-40 %
Carcinus maenas 4 Occasional 41-60 %
Littorina obtusata/mariae 3 Common 21-40 %
Patella vulgata 4 Occasional 41-60 %
Littorina littorea 8 Occasional 61-80 %
Nucella lapillus 2 Occasional 41-60 %
Mytilus edulis 3 Occasional 41-60 %
Polysiphonia 1 Occasional 21-40 %
Polysiphonia lanosa 5 Frequent 41-60 %
Ascophyllum nodosum 33 Abundant 81-100 %
Fucus vesiculosus 13 Frequent 81-100 %
Enteromorpha intestinalis 2 Occasional 41-60 %

Similar biotopes

LR.LLR.F.Asc.FS
Occurs on bedrock. Has a higher abundance and diversity of red seaweeds and species such as the hydroid Dynamena pumila and the lichen Verrucaria mucosa are present.

LR.LLR.FVS.AscVS
Occurs on bedrock or mixed substrata with variable salinity. Similar species composition but species, such as the hydroid D. pumila and the barnacle Elminius modestus are usually present.

LR.HLR.FT.AscT
Occurs on rock and mixed substrata in fully marine conditions. Has a high abundance and diversity of red seaweeds and filter feeding species such as the sponges Leucosolenia spp. and Grantia compressa, the hydroid Clava multicornis and the sea squirt Dendrodoa grossularia.

Biotope history

Classification Habitat code
6.95 LMXD.ASC

Photos

LR.LLR.F.Asc.X Ascophyllum nodosum on full salinity mid eulittoral mixed substrata, NE of Dorathy Stone, Loch Eil. Charlotte Johnston © JNCC
LR.LLR.F.Asc.X Ascophyllum nodosum on full salinity mid eulittoral mixed substrata, NE of Dorathy Stone, Loch Eil. Charlotte Johnston © JNCC
LR.LLR.F.Asc.X Ascophyllum nodosum on full salinity mid eulittoral mixed substrata, Brean Down, Severn Estuary. Kate Northen © JNCC
LR.LLR.F.Asc.X Ascophyllum nodosum on full salinity mid eulittoral mixed substrata, Brean Down, Severn Estuary. Kate Northen © JNCC
LR.LLR.F.Asc.X Ascophyllum nodosum on full salinity mid eulittoral mixed substrata, Brean Down, Severn Estuary. Kate Northen © JNCC
LR.LLR.F.Asc.X Ascophyllum nodosum on full salinity mid eulittoral mixed substrata, Brean Down, Severn Estuary. Kate Northen © JNCC

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