Description of biotope or habitat type
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Modiolus modiolus beds on open coast circalittoral mixed sediment
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Sheltered |
| Tidal streams | Moderately strong (1-3 kn) |
| Substratum | Muddy gravel and sand, with shells and stones |
| Zone | Circalittoral |
| Depth Band | 50-100 m |
| Other Features |
Biotope origin
| Derived using data from | Various |
| Faunal group | Epifauna/infauna |
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.
- 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.
Description
Muddy gravels and coarse sands in deeper water of continental seas may contain venerid bivalves with beds of Modiolus modiolus. The clumping of the byssus threads of the M. modiolus creates a stable habitat that attracts a very rich infaunal community with a high density of polychaete species including Glycera lapidum, Paradoneis lyra, Aonides paucibranchiata, Laonice bahusiensis, Protomystides bidentata, Lumbrineris spp., Mediomastus fragilis and syllids such as Exogone spp. and Sphaerosyllis spp. Bivalves such as Spisula elliptica, Timoclea ovata and other venerid species are also common. Brittlestars such as Amphipholis squamata may also occur with this community. This biotope is very similar to SS.SMx.OMx.PoVen and the 'boreal off-shore gravel association' and the 'deep Venus community' described by previous workers (Ford 1923; Jones 1951). Similar Modiolus beds (though with a less diverse infauna) on open coast stable boulders, cobbles and sediment are described under SS.SBR.SMus.ModT.
Situation
No situation data available.
Temporal variation
No temporal data available.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | Typical abundance - (count per m2) | % of core records where taxon was recorded |
|---|---|---|---|---|
| Modiolus modiolus | 4 | Super abundant | 385 | 81-100% |
| Aonides paucibranchiata | 3 | Common | 164 | 81-100% |
| Exogone verugera | 3 | Common | 151 | 81-100% |
| Glycera lapidum | 3 | Common | 94 | 81-100% |
| Amphipholis squamata | 2 | Abundant | 71 | 81-100% |
| Echinocyamus pusillus | 2 | Abundant | 140 | 61-80% |
| Parexogone hebes | 2 | Frequent | 75 | 81-100% |
| Harmothoe impar | 2 | Common | 54 | 81-100% |
| Laonice bahusiensis | 2 | Common | 69 | 81-100% |
| Leptochiton asellus | 2 | Abundant | 122 | 81-100% |
| Hilbigneris gracilis | 2 | Common | 75 | 81-100% |
| Mediomastus fragilis | 2 | Common | 288 | 81-100% |
| Nemertea | 2 | Common | 58 | 81-100% |
| Paradoneis lyra | 2 | Common | 90 | 81-100% |
| Polycirrus | 2 | Common | 50 | 81-100% |
| Protomystides bidentata | 2 | Common | 53 | 81-100% |
| Sphaerosyllis | 2 | Frequent | 41 | 81-100% |
| Spisula elliptica | 2 | Common | 51 | 81-100% |
| Asclerocheilus intermedius | 1 | Frequent | 32 | 81-100% |
| Leiochone johnstoni | 1 | Abundant | 52 | 61-80% |
| Eusyllis blomstrandi | 1 | Frequent | 39 | 81-100% |
| Grania | 1 | 44 | 81-100% | |
| Hydroides norvegica | 1 | Frequent | 35 | 81-100% |
| Lysilla | 1 | Abundant | 26 | 81-100% |
| Nereiphylla lutea | 1 | Abundant | 56 | 81-100% |
| Dipolydora flava | 1 | Frequent | 35 | 81-100% |
| Sphaerosyllis bulbosa | 1 | Frequent | 203 | 61-80% |
| Syllis | 1 | Frequent | 22 | 81-100% |
| Timoclea ovata | 1 | Common | 29 | 81-100% |
Similar biotopes or habitat types
SS.SMx.OMx.PoVen
SS.SMx.OMx.PoVen is similar to SS.SBR.SMus.ModMx but lacks the epifaunal Modiolus bed.
SS.SBR.SMus.ModT
SS.SBR.SMus.ModT tends to occur at the entrance to channels where tidal streams are strong.Classification history of this biotope or habitat type
| Classification version | Code | Habitat name |
|---|---|---|
| 2015 (15.03) | SS.SBR.SMus.ModMx | Modiolus modiolus beds on open coast circalittoral mixed sediment |
| 2004 (04.05) | SS.SBR.SMus.ModMx | Modiolus modiolus beds on open coast circalittoral mixed sediment |
| 1997 (97.06) | SS.CMX.ModMx | Modiolus modiolus beds on circalittoral mixed sediment |