Skip to Content

Marine Habitat Classification

Description of biotope or habitat type

To understand more about what this page is describing, see How to use the classification. See also How to cite.

   Kelp and seaweed communities in tide-swept sheltered conditions

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Bedrock, boulders and cobbles
Zone Infralittoral, Sublittoral fringe
Depth Band 0-5 m, 5-10 m, 10-20 m, Lower shore
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 IR.MIR.KT Kelp and seaweed communities in tide-swept sheltered conditions

  • 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'
  • Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat

Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.


Sheltered infralittoral rock exposed to strong tidal streams. In the sublittoral fringe dense Laminaria digitata is found together with erect seaweeds, sponges, ascidians and bryozoans (LdigT). Below this, on bedrock and stable boulders a canopy of mixed kelp (primarily Laminaria hyperborea and Saccharina latissima) occurs with foliose red seaweeds, sponges and ascidians (XKT). This biotope is typically found in the sheltered narrows and sills of Scottish sealochs. Mixed substrata of boulders, cobbles, pebbles and gravel, that also occurs in the tidal rapids of Scottish sealochs, supports a reduced kelp canopy (L. hyperborea and L. saccharina; typically Frequent), with a rich red seaweed component and maerl at some sites (XKTX). In south-west Britain, sheltered, tide-swept rock is restricted to estuarine conditions where variable salinity and increased turbidity of the water have a significant effect on the biota, limiting the infralittoral zone to very shallow depths. Unlike the tide-swept channels in sealochs, the rock in these estuaries is characterised by a relatively low abundance of L. saccharina (< Common) with foliose red seaweeds, sponges and ascidians (LsacT). L. hyperborea is rarely present.


No situation data available.

Temporal variation

No temporal variation data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Saccharina latissima 7 Frequent 61-80%
Halichondria panicea 6 Frequent 41-60%
Corallinaceae 4 Frequent 41-60%
Carcinus maenas 4 Occasional 41-60%
Laminaria hyperborea 4 Common 41-60%
Spirobranchus triqueter 4 Frequent 41-60%
Asterias rubens 3 Occasional 41-60%
Ulva lactuca 3 Occasional 41-60%
Balanus crenatus 2 Frequent 21-40%
Botryllus schlosseri 2 Occasional 41-60%
Chondrus crispus 2 Occasional 41-60%
Dictyota dichotoma 2 Occasional 21-40%
Steromphala cineraria 2 Occasional 41-60%
Halidrys siliquosa 2 Occasional 41-60%
Laminaria digitata 2 Common 21-40%
Echinus esculentus 2 Occasional 21-40%
Anemonia viridis 1 Occasional 21-40%
Clavelina lepadiformis 1 Occasional 21-40%
Corallina officinalis 1 Occasional 21-40%
Hypoglossum hypoglossoides 1 Frequent 21-40%
Lithothamnion glaciale 1 Frequent 21-40%
Ophiothrix fragilis 1 Occasional 21-40%
Urticina felina 1 Occasional 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

Back to top