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Marine Habitat Classification

Description of biotope or habitat type

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   Infralittoral fine mud

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Mud (occasionally with shells or stones)
Zone Infralittoral
Depth Band 0-5 m, 5-10 m, 10-20 m
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 SS.SMu.IFiMu Infralittoral fine 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'
  • Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat

Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.


Shallow sublittoral muds, extending from the extreme lower shore to about 15-20 m depth in fully marine or near marine conditions, predominantly in extremely sheltered areas with very weak tidal currents. Such habitats are found in sealochs and some rias and harbours. Populations of the lugworm Arenicola marina may be dense, with anemones, the opisthobranch Philine aperta and synaptid holothurians also characteristic in some areas. The extent of the oxidised layer may be shallow with some areas being periodically or permanently anoxic. In these areas bacterial mats may develop on the sediment surface. Infaunal records for this biotope complex are limited encompassing only one biotope. They are therefore not representative of the full suit of infaunal species found in this biotope.


No situation data available.

Temporal variation

No temporal data available.

Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Hydractinia echinata 2 Occasional 21-40 %
Cerianthus lloydii 2 Occasional 21-40 %
Ophiodromus flexuosus 4 41-60 %
Hediste diversicolor 2 Frequent 21-40 %
Polydora ciliata 1 21-40 %
Aphelochaeta marioni 4 41-60 %
Caulleriella caputesocis 15 Frequent 61-80 %
Arenicola marina 12 Frequent 41-60 %
Pagurus bernhardus 7 Occasional 41-60 %
Liocarcinus depurator 3 Rare 21-40 %
Carcinus maenas 25 Occasional 61-80 %
Hydrobia ulvae 20 Frequent 61-80 %
Philine aperta 6 Frequent 21-40 %
Cerastoderma edule 33 Common 81-100 %
Abra nitida 22 Common 61-80 %
Asterias rubens 6 Occasional 41-60 %
Beggiatoa 16 21-40 %
Diatoms - film 4 21-40 %
Laminaria saccharina 2 21-40 %

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
97.06 IMU.MarMu

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