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Marine Habitat Classification

Description of biotope or habitat type

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   Oligochaetes in variable or reduced salinity infralittoral muddy sediment

Physical habitat description

Salinity Reduced (18-30ppt), Variable (18-35 ppt)
Wave exposure Very sheltered, Extremely sheltered
Tidal streams Moderately strong (1-3 kn), Weak (>1 kn)
Substratum Cohesive muddy sediment, sandy mud
Zone Infralittoral
Depth Band 0-5 m
Other Features Possibly affected by a high biochemical oxygen demand

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.SMuVS.OlVS Oligochaetes in variable or reduced salinity infralittoral muddy sediment

  • 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.


Reduced or variable salinity muddy and sandy mud sediments characterised by oligochaetes, particularly of the genus Tubificoides or from the group Enchytraeidae. The abundance of the oligochaetes may vary by several orders of magnitude but very few other species will be present. Organic loading and poor water-exchange within the sediment lead to anoxic conditions which may explain the low species richness within this biotope.


This biotope is found towards the edges of tidal channels in estuaries where current velocities allow deposition of silt and the establishment of an infaunal community. The biotope may occur downstream of SMU.LhofTtub, differentiated by the absence of the freshwater species, and adjacent to more mobile and sandier biotopes in the tidal channels.

Temporal variation

No temporal data available.

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
Oligochaeta 84 Frequent 245 61-80 %
Tubificoides pseudogaster 2 40 1-20 %
Diptera larva 11 Abundant 61 21-40 %

Similar biotopes or habitat types

LhofTtub is similar to OlVS however the latter lacks the freshwater element

CapTubi can be separated from OlVS by the presence of the polychaete Capitella capitata.

More mobile muds, which occur in areas with an extremely high suspended particulate component to the water column, MoMu, may contain a very similar suite of species to OlVS and can only positively be separated by a description of the sediment characteristics in the field.

Classification history of this biotope or habitat type

Classification version Code

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