Description of biotope or habitat type
Seapens and burrowing megafauna in circalittoral fine mud
Habitat (physical) description
|Salinity||Full (30-35 ppt), Variable (18-35 ppt)|
|Wave exposure||Moderately exposed, Sheltered, Very sheltered, Extremely sheltered|
|Tidal streams||Weak (>1 kn), Very weak (negligible)|
|Depth Band||10-20 m, 20-30 m, 30-50 m|
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
Plains of fine mud at depths greater than about 15 m may be heavily bioturbated by burrowing megafauna; burrows and mounds may form a prominent feature of the sediment surface with conspicuous populations of seapens, typically Virgularia mirabilis and Pennatula phosphorea. The burrowing crustacea present typically include Nephrops norvegicus, which is frequently recorded from surface observations although grab sampling may fail to sample this species. Indeed, some forms of sampling may also fail to indicate seapens as characterising species. This biotope also seems to occur in deep offshore waters in the North Sea, where densities of Nephrops norvegicus may reach 68 per 10 m-2 (see Dyer et al. 1982, 1983), and the Irish Sea. The burrowing anemone Cerianthus lloydii and the ubiquitous epibenthic scavengers Asterias rubens, Pagurus bernhardus and Liocarcinus depurator are present in low numbers in this biotope whilst the brittlestars Ophiura albida and Ophiura ophiura are sometimes present, but are much more common in slightly coarser sediments. Low numbers of the anemone Pachycerianthus multiplicatus may also be found, and this species, which is scarce in the UK, appears to be restricted to this habitat (Plaza & Sanderson 1997). The infauna may contain significant populations of the polychaetes Pholoe spp., Glycera spp., Nephtys spp., spionids, Pectinaria belgica and Terebellides stroemi, the bivalves Nucula sulcata, Corbula gibba and Thyasira flexuosa, and the echinoderm Brissopsis lyrifera.
These soft mud habitats occur extensively throughout the more sheltered basins of sealochs and voes and are present in quite shallow depths (as little as 15 m) in these areas probably because they are very sheltered from wave action.
No temporal data available.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Hydractinia echinata||1||Occasional||21-40 %|
|Virgularia mirabilis||20||Frequent||61-80 %|
|Pennatula phosphorea||6||Frequent||41-60 %|
|Cerianthus lloydii||13||Occasional||61-80 %|
|Chaetopterus variopedatus||2||Occasional||21-40 %|
|Nephrops norvegicus||18||Frequent||61-80 %|
|Pagurus bernhardus||5||Occasional||41-60 %|
|Liocarcinus depurator||8||Occasional||41-60 %|
|Turritella communis||3||Frequent||21-40 %|
|Asterias rubens||8||Occasional||61-80 %|
|Amphiura chiajei||2||Common||21-40 %|