Description of biotope or habitat type

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   Hediste diversicolor, Macoma balthica and Eteone longa in littoral muddy sand

Description

Fine to very fine muddy sand on the mid shore at the lower extreme of estuaries, and in moderately exposed and sheltered bays and marine inlets, sometimes subject to variable salinity. The infauna is characterised by the polychaetes Eteone longa, Hediste diversicolor (ragworm) and Pygospio elegans, oligochaetes (mostly Tubificoides benedii and T. pseudogaster), the crustaceans Corophium volutator and Crangon crangon, the spire shell Peringia ulvae and the baltic tellin Macoma balthica. The cockle Cerastoderma edule may be abundant, and the sand gaper Mya arenaria may be superabundant, though these species are not always present, or may be missed in core samples due to their large size. The polychaetes Arenicola marina, Polydora cornuta and Capitella capitata, the shrimp Crangon crangon, and the Mussel Mytilus edulis are sometimes present.

Situation

HedMacEte can occur on the mid shore of sheltered, lower estuaries, with the MEST communities in muddier sediments on the lower shore. Under moderately exposed conditions in lower estuaries and towards open coasts, it may occur alongside other muddy sand biotopes such as CerPo or BatCare.

Temporal variation

Enteromorpha spp. or Ulva lactuca may form mats on the surface of the sediment during the summer months, particularly in areas of freshwater influence and/or where there is nutrient enrichment.

Characterising species

Similar biotopes or habitat types

LS.LSa.FiSa.Po

These biotopes occur in slightly more exposed, marine sediments which lack a silt/clay fraction. The principal infaunal difference is the absence of C. edule and M. balthica.

LS.LMu.MEst.HedMac

Occurs in more sheltered, less saline, mid-shore or lower shore sandy mud and mud. E. longa and P. elegans are less consistently present, but Tubificoides spp. are abundant.

LS.LMu.MEst.HedMacScr

Occurs in less saline, more sheltered muddy conditions on the lower shore, further towards the head of estuaries. There is a greater diversity of polychaetes, M. balthica is not always present, but Scrobicularia plana occurs in high densities.

LS.LMu.MEst.NhomMacStr

Occurs lower down on the shore, in muddier sediments. H. diversicolor occurs only occasionally, but Nephtys hombergii tends to be abundant. Tubificoides spp. are common.

LS.LSa.MuSa.MacAre

Occurs in similar environmental conditions, though on more sheltered coasts and only rarely where there is freshwater influence. H. diversicolor is absent, and fewer mollusc species are present. M. arenaria and H. ulvae do not occur.

LS.LMu.UEst.Hed.Str

Occurs in less saline, more sheltered muddy conditions on the lower shore, further towards the head of estuaries. P. elegans occurs less frequently, Streblospio shrubsolii is abundant. The only molluscs that occur are occasionally common Peringia ulvae and S. plana.

LS.LMu.UEst.Hed.Ol

Occurs in more sheltered, less saline, mid-and lower-shore sandy mud. The polychaete fauna is a lot poorer, and bivalves are virtually absent.

Classification history of this biotope or habitat type