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Marine Habitat Classification


Description of biotope or habitat type

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   Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure Very sheltered, Extremely sheltered
Tidal streams Very strong (>6 kn), Strong (3-6 kn), Moderately strong (1-3 kn)
Substratum Bedrock; boulders; cobbles
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.HLR.FT.AscT <I>Ascophyllum nodosum</I>, sponges and ascidians on tide-swept mid 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

Very sheltered to extremely sheltered areas of mid eulittoral rock that are subject to strong to moderate tidal streams, such as the narrows in sea lochs, and characterised by the wrack Ascophyllum nodosum. The wracks Fucus vesiculosus and Fucus serratus are occasionally present. The increased water movement encourages a rich associated fauna including several filter-feeding groups. These include the sponges Leucosolenia spp., Grantia compressa, Halichondria panicea and Hymeniacidon perleve which frequently occur on steep and overhanging faces of boulders and bedrock. It also includes the sea squirts Dendrodoa grossularia and Ascidiella scabra, which occur on steep surfaces and beneath boulders. Hydroids such as the pink Clava multicornis can form colonies on A. nodosum while Dynamena pumila is more often found on F. vesiculosus or F. serratus. Underneath the canopy formed by the brown seaweeds is a diverse community of the red seaweeds Gelidium pusillum, Chondrus crispus, Lomentaria articulata, Membranoptera alata and coralline crusts, but the green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris can be present. The filamentous red seaweed Polysiphonia lanosa can usually be found growing on A. nodosum. On the rock beneath are the limpet Patella vulgata and the barnacle Semibalanus balanoides, while the crab Carcinus maenas and a variety of winkles including Littorina littorea, Littorina mariae and Littorina obtusata can be found on or among the boulders. The whelk Nucella lapillus can either be found in cracks and crevices or preying on the barnacles.

Situation

This biotope occurs lower on the shore than the Fucus spiralis biotope (Fspi) although on some shores a narrow zone of F. vesiculosus (Fves) may occur immediately above the A. nodosum. Asc.T is found above the tide-swept F. serratus dominated biotope (Fserr.T).

Temporal variation

A. nodosum can reach an age of 25 years and the communities are usually very stable. F. vesiculosus or F. serratus can occur in patches where the A. nodosum has been removed.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Grantia compressa 1 Occasional 41-60 %
Halichondria panicea 3 Occasional 61-80 %
Hymeniacidon perleve 1 Rare 41-60 %
Clava multicornis 3 Frequent 41-60 %
Dynamena pumila 6 Frequent 81-100 %
Semibalanus balanoides 5 Occasional 61-80 %
Carcinus maenas 2 Occasional 61-80 %
Littorina obtusata/mariae 1 Occasional 41-60 %
Patella vulgata 6 Occasional 81-100 %
Littorina littorea 1 Frequent 21-40 %
Nucella lapillus 4 Occasional 81-100 %
Dendrodoa grossularia 3 Frequent 61-80 %
Gelidium pusillum 2 Frequent 41-60 %
Corallinaceae 4 Frequent 61-80 %
Chondrus crispus 1 Frequent 41-60 %
Lomentaria articulata 2 Occasional 41-60 %
Membranoptera alata 1 Rare 41-60 %
Polysiphonia lanosa 6 Frequent 81-100 %
Ascophyllum nodosum 19 Super abundant 81-100 %
Fucus serratus 3 Occasional 61-80 %
Fucus vesiculosus 4 Occasional 61-80 %
Enteromorpha intestinalis 3 Occasional 61-80 %
Ulva lactuca 4 Occasional 61-80 %
Cladophora rupestris 2 Frequent 41-60 %

Similar biotopes

LR.LLR.F.Asc.FS
Occurs on bedrock with weak tidal streams. Lower diversity of filter feeders and lacks species such as the sponges Leucosolenia spp. and G. compressa, the hydroid C. multicornis or the sea squirt D. grossularia .

LR.LLR.FVS.AscVS
Occurs on bedrock or mixed substrata with variable salinity. Coralline crusts and C. crispus, N. lapillus and anemone Actinia equina are not usually present in this species impoverished biotope. It is also lacks the filter feeders mentioned above.

LR.LLR.F.Asc.X
Occurs on mixed substrata in fully marine conditions. Has a lower abundance and diversity of red seaweeds and lacks species such as Leucosolenia spp. and G. compressa, the hydroid C. multicornis and the sea squirt D. grossularia.

Biotope history

Classification Habitat code
97.06 SLR.ASC.T

Photos

LR.HLR.FT.AscT Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock, Loch nam Bodach, Loch nam Bodach, Lewis. Rohan Holt © JNCC
LR.HLR.FT.AscT Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock, Loch nam Bodach, Loch nam Bodach, Lewis. Rohan Holt © JNCC
LR.HLR.FT.AscT Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock, Loch An-t-Sroim, Loch Eynort. ANON © JNCC
LR.HLR.FT.AscT Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock, Loch An-t-Sroim, Loch Eynort. ANON © JNCC
LR.HLR.FT.AscT Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock, Bagh na Haun. ANON © JNCC
LR.HLR.FT.AscT Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock, Bagh na Haun. ANON © JNCC

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