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Marine Habitat Classification

Description of biotope or habitat type

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   Polychaete/oligochaete-dominated upper estuarine mud shores

Physical habitat description

Salinity Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams
Substratum Sandy mud, mud
Depth Band Lower shore, Mid shore, 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.LMu.UEst Polychaete/oligochaete-dominated upper estuarine mud shores

  • 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.


Upper estuarine sandy mud and mud shores, in areas with significant freshwater influence. Littoral mud typically forms mudflats, though dry compacted mud can form steep and even vertical structures, particularly at the top of the shore adjacent to saltmarshes. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. The upper estuarine mud communities support few infaunal species and are principally characterised by a restricted range of polychaetes and oligochaetes.


There are three oligochaete dominated upper estuarine mud biotopes. Of these three, NhomStr occurs the furthest towards the mid estuary, and possibly lower on the shore than the other two. Tben is the most extreme upper estuarine biotope, occurring at the head of estuaries where there is no strong river flow and hence conditions are very sheltered, and there is a very strong freshwater influence. Further towards the mid estuary, this biotope may occur at the top of the shore, with Hed.Ol and NhomStr further down the shore.

Temporal variation

Enteromorpha spp. and Ulva lactuca may form mats on the surface of the mud during the summer months, particularly in areas of nutrient enrichment.

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 40 Super abundant 1584 81-100%
Oligochaeta 9 Abundant 6871 21-40%
Streblospio shrubsolii 9 Common 1289 41-60%
Corophium volutator 8 Common 1811 21-40%
Tubificoides benedii 8 Common 2031 21-40%
Manayunkia aestuarina 4 Common 1832 21-40%
Baltidrilus costatus 3 Abundant 1699 21-40%
Nematoda 2 Common 558 1-20%
Peringia ulvae 2 Common 294 21-40%
Pygospio elegans 2 Common 121 21-40%
Scrobicularia plana 2 Common 36 21-40%
Cyathura carinata 2 Common 121 1-20%
Nephtys hombergii 1 Common 30 41-60%

Similar biotopes or habitat types

Not applicable or unknown.

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