Offshore subtidal sands and gravels
Sand and gravel sediments are the most common subtidal habitat around the coast of the British Isles and are abundant in the offshore waters of Scotland. Offshore fine and muddy sands often comprise communities of tube building polychaetes, burrowing brittlestars, polychaetes and bivalves, other communities in medium sands are dominated by pea urchins, while communities in fine sands are dominated by amphipods and hooded shrimps.
The biotopes shown on these layers are being identified as part of development of the deep-sea habitat classification for Britain and Ireland. They include 4 layers:
- Echinocyamus pusillus, Ophelia borealis and Abra prismatica in circalittoral fine sand (SS.SSa.CFiSa.EpusOborApri). Circalittoral and offshore medium to fine sands at a depth range of 40-140m may be characterised by the pea urchin Echinocyamus pusillus, the polychaete Ophelia borealis and the bivalve Abra prismatica may develop. Other species may include the polychaetes Spiophanes bombyx, Pholoe sp., Exogone spp., Sphaerosyllis bulbosa, Goniada maculata, Chaetozone setosa, Owenia fusiformis, Glycera lapidum, Lumbrineris latreilli and Aricidea cerrutii and the bivalves Thracia phaseolina and Moerella pygmaea and to a lesser extent Spisula elliptica and Timoclea ovata. This biotope has been found in the central and northern North Sea (Connor et al., 2004).
- Hesionura elongata and Protodorvillea kefersteini in offshore coarse sand (SS.SCS.OCS.HeloPkef). In the UK offshore (deep) circalittoral habitats with coarse sand may support populations of the interstitial polychaete Hesionura elongata with Protodorvillea kefersteini. Other notable species include the phyllodocid polychaete Protomystides limbata and the bivalve Moerella pygmaea. This biotope was reported in the offshore northern North Sea by Eleftheriou and Basford (1989). Relatively little data exists for this biotope.
- Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand (SS.SSa.Osa.OfusAfil). Areas of slightly muddy sand (generally <20% mud) in offshore waters may be characterised by high numbers of the tube building polychaete O. fusiformis often with the brittlestar A. filiformis. Whilst O. fusiformis is also found in other circalittoral or offshore biotopes it usually occurs in lower abundances than in this biotope. Other species found in this community are the polychaetes Goniada maculata, Pholoe inornata, Diplocirrus glaucus, Chaetozone setosa and Spiophanes kroyeri with occasional bivalves such as Timoclea ovata and Thyasira equalis. The sea cucumber Labidoplax buski and the cumacean Eudorella truncatula are also commonly often found in this biotope (Connor et al., 2004).
- Other Offshore subtidal sands and gravels.