Search

In offshore circalittoral slightly muddy mixed sediments, a diverse community particularly rich in polychaetes with a significant venerid bivalve component may be found. Typical species include the polychaetes Glycera lapidum, Aonides paucibranchiata, Laonice bahusiensis, Mediomastus fragilis, Hilbigneris gracilis, Pseudomystides limbata, Protomystides bidentata and syllid species and bivalves such as Timoclea ovata, Glycymeris glycymeris, Spisula elliptica and Goodallia triangularis. Some examples of this biotope may have abundant juvenile Modiolus modiolus. Several echinoderms including Amphipholis squamata, Echinocyamus pusillus are present in many locations. In coarser variations of the biotope, with gravelly sediment and the presence of pebbles or cobbles, the biotope may support encrusting fauna such as hydroids, Sertularia cupressina and Hydrallmania falcata, bryozoans and Spirobranchus triqueter. Mobile crustacea including the long-clawed porcelain crab Pisidia longicornis and amphipod Nototropis vedlomensis can also be highly abundant. This biotope has been recorded in the Irish Sea and English Channel and collectively with SS.SCS.CCS.MedLumVen comprise the 'Deep Venus Community' and the 'Boreal Off-Shore Gravel Association' as defined by other workers (Ford 1923; Jones 1950).

Offshore (deep) circalittoral habitats with coarse sands and gravel, stone or shell and occasionally a little silt (<5%) may be characterised by the polychaetes Glycera lapidum and Amythasides macroglossus with the bivalve Thyasira spp. (particularly Thyasira succisa). Other taxa include polychaetes such as Exogone verugera, Notomastus latericeus, Spiophanes kroyeri, Aphelochaeta marioni (Tharyx marioni) and Hilbigneris gracilis and occasional numbers of the bivalve Timoclea ovata. This biotope bears some resemblance to the shallow SS.SCS.ICS.Glap and to the circalittoral and offshore venerid biotopes (SS.SCS.CCS.MedLumVen and SS.SMx.OMx.PoVen) but differs by the range of polychaete and bivalve fauna present. This biotope is notable for the presence of the rarely recorded ampharetid polychaete Amythasides macroglossus and also for the small ear file clam Limatula subauriculata which is common in some examples of this biotope.

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.