Skip to Content

Marine Habitat Classification

Description of biotope or habitat type

To understand more about what this page is describing, see How to use the classification. See also How to cite.

   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

Biotope origin

Derived using data from Various
Faunal group Epifauna/Infauna

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 sea lochs 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 suite 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
Cerastoderma edule 33 Common 81-100%
Carcinus maenas 25 Occasional 61-80%
Abra nitida 22 Common 61-80%
Peringia ulvae 20 Frequent 61-80%
Beggiatoa 16 21-40%
Chaetozone caputesocis 15 Frequent 61-80%
Arenicola marina 12 Frequent 41-60%
Pagurus bernhardus 7 Occasional 41-60%
Asterias rubens 6 Occasional 41-60%
Philine aperta 6 Frequent 21-40%
Diatoms - film 4 21-40%
Aphelochaeta marioni 4 41-60%
Oxydromus flexuosus 4 41-60%
Liocarcinus depurator 3 Rare 21-40%
Cerianthus lloydii 2 Occasional 21-40%
Hediste diversicolor 2 Frequent 21-40%
Hydractinia echinata 2 Occasional 21-40%
Saccharina latissima 2 21-40%
Polydora ciliata 1 21-40%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code Habitat name
2015 (15.03) SS.SMu.IFiMu Infralittoral fine mud
2004 (04.05) SS.SMu.IFiMu Infralittoral fine mud
1997 (97.06) SS.IMU.MarMu Shallow marine mud communities

Back to top