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Marine Habitat Classification


Description of biotope or habitat type

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   Hediste diversicolor and Macoma balthica in littoral gravelly mud


Habitat (physical) description

Salinity Reduced (18-30ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams
Substratum Gravelly mud
Zone
Depth Band Lower shore, Mid shore, Strandline, Upper shore
Other Features

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.

Distribution of habitat LS.LMx.GvMu.HedMx.Mac <I>Hediste diversicolor</I> and <I>Macoma balthica</I> in littoral gravelly mud

  • 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'

Point data based on records in the UK Marine Recorder Snapshot.

Description

Sheltered gravelly mud shores, subject to reduced salinity. The infaunal community consists of the ragworm Hediste diversicolor, as well as the spire shell Hydrobia ulvae and the baltic tellin Macoma balthica. The presence of the gravel in the sediment is unlikely to have a large influence on the infaunal composition, which is driven mainly by the estuarine sandy mud conditions. Coarse material on the sediment surface may however enrich the biota with additional epifaunal species such as barnacles and algae. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.

Situation

It is probable that there are broad transition areas between this biotope, and the corresponding muddy sediment biotope HedMac. The boundaries may be very indistinct, with HedMx.Mac present in patches of gravelly mud on areas of mudflat, where the main biotope is HedMac. This biotope has been found alongside its mud equivalent in the Stour estuary.

Temporal variation

Not known.

Characterising Species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale Typical abundance - (count per m2) % of core records where taxon was recorded
Hediste diversicolor 61 Super abundant 2388 81-100 %
Hydrobia ulvae 25 Common 2296 81-100 %
Macoma balthica 11 Common 413 81-100 %

Similar biotopes

LS.LMu.MEst.HedMac
Occurs in lower estuarine muds and sandy muds, without a gravel fraction. The infauna is dominated by the same species, but is more diverse (though that may be an artefact of greater number of samples in the HedMac biotope).

LS.LMx.GvMu.HedMx.Str
Occurs in gravelly sandy mud lower down on the shore, under more sheltered conditions. The polychaete infauna is much more diverse, and a range of oligochaete species are found. M. balthica is rare.

LS.LMx.GvMu.HedMx.Scr
Occurs higher up on the shore under more sheltered conditions. The infaunal assemblage is more diverse, with a greater range of polychaetes and bivalves. Scrobicularia plana is abundant, though M. balthica is only occasionally present.

LS.LMx.GvMu.HedMx.Cir
Occurs in slightly more sheltered gravelly sandy mud. The principal differences in the infaunal assemblage are the greater diversity of polychaete species, particularly Tharyx killariensis, the abundance of oligochaetes, and the comparative rarity of molluscs.

LS.LMx.GvMu.HedMx.Cvol
Occurs in more sheltered gravelly sandy mud. The principal differences in the infaunal assemblage are the abundance of oligochaetes and Corophium volutator, and the low frequency of occurrence of molluscs.


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