4 results for 'SS.SSa.IFiSa.NcirBat'
SS.SSa.IFiSa.NcirBat Nephtys cirrosa and Bathyporeia spp. in infralittoral sand
Well-sorted medium and fine sands characterised by Nephtys cirrosa and Bathyporeia spp. (and sometimes Pontocrates spp.) which occur in the shallow sublittoral to at least 30 m depth. This biotope occurs in sediments subject to physical disturbance, as a result of wave action (and occasionally strong tidal streams in outer estuarine variants of the biotope). The magelonid polychaete Magelona mirabilis may be frequent in this biotope in more sheltered, less tideswept areas whilst in coarser sediments the opportunistic polychaete Chaetozone setosa may be commonly found. The faunal diversity of this biotope is considerably reduced compared to less disturbed biotopes (such as SS.SSa.IMuSa.FfabMag) and for the most part consists of the more actively-swimming amphipods. Sand eels Ammodytes sp. may occasionally be observed in association with this biotope (and others) and spionid polychaetes such as Spio filicornis and S. martinensis may also be present. Occasional Lanice conchilega may be visible at the sediment surface. Variants of the biotope in coarser sediment may have more variable fauna, with the absence of Nephtys, and presence of bryozoans, such as Crisia, however retain examples of Bathyporeia spp. and Magelona spp.
SS.SSa.IFiSa.IMoSa Infralittoral mobile clean sand with sparse fauna
Medium to fine sandy sediment in shallow water, often formed into dunes, on exposed or tide-swept coasts often contains very little infauna due to the mobility of the substratum. Some opportunistic populations of infaunal amphipods may occur, particularly in less mobile examples in conjunction with low numbers of mysids such as Gastrosaccus spinifer, the polychaete Nephtys cirrosa and the isopod Eurydice pulchra. Sand eels Ammodytes sp. may occasionally be observed in association with this biotope (and others). This biotope is more mobile than SS.SSa.IFiSa.NcirBat and may be closely related to LS.LSa.MoSa.BarSa on the shore. Common epifaunal species such as Pagurus bernhardus, Liocarcinus depurator, Carcinus maenas and Asterias rubens may be encountered and are the most conspicuous species present.
SS.SCS.ICS.SLan Dense Lanice conchilega and other polychaetes in tide-swept infralittoral sand and mixed gravelly sand
Dense beds of Lanice conchilega occur in coarse to medium fine gravelly sand in the shallow sublittoral, where there are strong tidal streams or wave action. Several other species of polychaete also occur as infauna e.g. Spiophanes bombyx, Scoloplos armiger, Chaetozone setosa and Magelona mirabilis. Lanice beds are found in a wide range of habitats including muddier mixed sediment. The dense Lanice biotope (LS.LSa.MuSa.Lan) on certain lower shores may be a littoral extension of the current biotope. The presence of L. conchilega in high numbersmay, over time, stabilise the sediment to the extent where a more diverse community may develop. Possibly, as a result of this, there is a high level of variation with regard the infauna found in SS.SCS.ICS.SLan. It is likely that a number of sub-biotopes may subsequently be identified for this biotope. Offshore from the Wash and the North Norfolk coast Lanice beds are often found intermixed with Sabellaria spinulosa beds in muddier mixed sediment, particularly in the channels between the shallow sandbanks, which are prevalent in this area. It is possible that the presence of Lanice has stabilised the habitat sufficiently to allow the deposition of finer material, which has subsequently assisted the development of S. spinulosa. It may be more accurate to define SS.SCS.ICS.SLan as an epibiotic biotope which overlays a variety of infaunal biotopes (e.g. SS.SSa.IFiSa.NcirBat in finer sands and SS.SSa.CMuSa.AalbNuc or SS.SSa.IMuSa.FfabMag in slightly muddier areas).
SS.SSa.IMuSa.EcorEns Echinocardium cordatum and Ensis spp. in lower shore and shallow sublittoral slightly muddy fine sand
Sheltered lower shore and shallow sublittoral sediments of sand or muddy fine sand in fully marine conditions, support populations of the urchin Echinocardium cordatum and the razor shell Ensis siliqua or Ensis ensis. Other notable taxa within this biotope include occasional Lanice conchilega, Pagurus, Liocarcinus spp. and Asterias rubens. This biotope has primarily been recorded by epifaunal dive, video or trawl surveys where the presence of relatively conspicuous taxa such as E. cordatum and Ensis spp. have been recorded as characteristic of the community. However, these species, particularly E. cordatum, have a wide distribution and are not necessarily the best choice for a characteristic taxa (Thorson, 1957). Furthermore, detailed quantitative infaunal data for this biotope is rather scarce, possibly as a result of survey method as remote grab sampling is likely to under-estimate deep-burrowing species such as Ensis sp. (Warwick & Davis 1977). Consequently, it may be better to treat this biotope as an epibiotic overlay which is likely to overlap with a number of other biotopes such as SS.SSa.IMuSa.FfabMag, SS.SSa.IFiSa.NcirBat and SS.SSa.CMuSa.AalbNuc with infaunal components of these biotopes occurring within SS.SSa.IMuSa.EcorEns. The precise nature of this infaunal community will be related to the nature of the substratum, in particular the quantity of silt/clay present. Infaunal species may include the polychaetes Spiophanes bombyx, Magelona mirabilis, Nephtys cirrosa and Chaetozone setosa and the amphipod Bathyporeia spp. This biotope is currently broadly defined and needs further consideration as to whether it should be placed at biotope or biotope complex level. SS.SSa.IMuSa.AreISa is another biotope based primarily on epibiotic data. It is likely that this biotope and SS.SSa.IMuSa.EcorEns form a wider epibiotic sand /muddy sand community with SS.SSa.IMuSa.EcorEns biased towards sandier areas and SS.SSa.IMuSa.AreISa towards slightly muddier areas.