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Marine Habitat Classification

Description of biotope or habitat type

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   Codium spp. with red seaweeds and sparse Saccharina latissima on shallow, heavily-silted, very sheltered infralittoral rock

Physical habitat description

Salinity Reduced (18-30ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Boulders, cobbles, bedrock
Zone Infralittoral
Depth Band 0-5 m, 5-10 m
Other Features Heavy siltation

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.LIR.KVS.Cod <I>Codium</I> spp. with red seaweeds and sparse <I>Saccharina latissima</I> on shallow, heavily-silted, very sheltered infralittoral 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'
  • 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.


Very shallow, heavily-silted infralittoral rock characterised by dense stands of Codium spp., together with silt-tolerant red seaweeds, the green seaweed Ulva spp. and often only a sparse covering of the kelp Saccharina latissima. This biotope appears to have a restricted distribution, being known at present only from the sheltered voes of Shetland, some Scottish lagoons and from the harbours of south-west England. These locations suggest the habitat is likely to be subject to reduced salinity conditions (although the habitat data indicate mostly fully marine records). Dense Codium spp. can occur at very sheltered sites, on cobbles or boulders, often in dense patches interspersed with filamentous red seaweeds Bonnemaisonia hamifera, Antithamnionella spirographidis and Ceramium spp. Where sediment is present the red seaweed Polyides rotunda is commonly found along the rock-sediment interface, and the sponge Dysidea fragilis often occurs on the rock. Other red seaweeds that may be present include Chondrus crispus, Metacallophyllis laciniata, Gelidium spinosum, Corallina officinalis and coralline crusts. The brown seaweeds Halidrys siliquosa, Desmarestia viridis or Chorda filum may be present in high abundance and although kelp L. saccharina may occur, it is usually sparse. There are no conspicuous fauna that typify this biotope, though polychaetes such as terebellids and spirorbids may occur. The opisthobranch Elysia viridis may be locally abundant on the seaweeds and is known to favour Codium fragilis in particular. Large stands of Codium sp. (generally Common abundance) are accompanied by red seaweeds such as G. latifolium, C. laciniata and A. spirographidis on the rock beneath. Cod has been reported to occur in the shallows of The Fleet, Bembridge Ledges, Pagham Harbour and Jersey (Tittley et al. 1985). In Ireland, species-poor shallow, silted bedrock in the North Water of Mulroy Bay, Co. Donegal, is characterised by Griffithsia corallinoides (Common) and Codium tomentosum (Frequent) forming a narrow band below the kelp zone (Lsac.Ft). Cod has not been described from any other sites in Ireland. If Codium spp. is less than Common amongst dense L. saccharina and Chorda filum, it should not be recorded as Cod.


This biotope occurs on bedrock below a sublittoral fringe of mixed kelp L. saccharina and Laminaria digitata (Lsac.Ldig) or below a L. saccharina forest (Lsac.Ft) or else on isolated boulders on sediment. It appears to be most frequently found in lagoons. Further information on which species of Codium is present and on the associated fauna is required.

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Codium 32 Common 81-100%
Bonnemaisonia hamifera 9 Frequent 41-60%
Corallinaceae 4 Frequent 41-60%
Saccharina latissima 4 Abundant 41-60%
Carcinus maenas 3 Occasional 41-60%
Chorda filum 3 Frequent 41-60%
Desmarestia viridis 3 Frequent 21-40%
Ulva lactuca 3 Occasional 41-60%
Metacallophyllis laciniata 2 Occasional 21-40%
Corallina officinalis 2 Occasional 21-40%
Gelidium spinosum 2 Frequent 21-40%
Spirorbinae 2 Occasional 21-40%
Seraphsidae 2 Frequent 21-40%
Antithamnionella spirographidis 1 Frequent 21-40%
Ceramium 1 Common 21-40%
Ceramium nodulosum 1 Occasional 21-40%
Chondrus crispus 1 Frequent 21-40%
Cladophora 1 Occasional 21-40%
Ectocarpaceae 1 Occasional 21-40%
Halidrys siliquosa 1 Occasional 21-40%
Polyides rotunda 1 Occasional 21-40%

Similar biotopes or habitat types

In IR.LIR.KVS.Cod S. latissima is replaced in abundance by Codium spp.

Lower diversity of red and brown seaweeds.

Reduced salinity and lower diversity of red and brown seaweeds.

Dense Codium spp. can occur in the saline lagoons of Scotland amongst fucoids and C. filum.

Classification history of this biotope or habitat type

Classification version Code
2015 (15.03) IR.LIR.KVS.Cod
1996 (6.95) SIR.Lsac.CodR


IR.LIR.K.Cod Codium spp. with red seaweeds and sparse Saccharina latissima on shallow, heavily-silted, very sheltered infralittoral rock, W Kirk Taing, North Sanday. Sue Scott© JNCC
IR.LIR.K.Cod Codium spp. with red seaweeds and sparse Saccharina latissima on shallow, heavily-silted, very sheltered infralittoral rock, W Kirk Taing, North Sanday. Sue Scott© JNCC

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