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Marine Habitat Classification

Description of biotope or habitat type

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   Filamentous green seaweeds on low salinity infralittoral mixed sediment or rock

Physical habitat description

Salinity Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Muddy sediment with pebbles & cobbles & boulders
Zone Infralittoral
Depth Band 0-5 m, 5-10 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.SMp.KSwSS.FilG Filamentous green seaweeds on low salinity infralittoral mixed sediment or rock

  • 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 muddy sediments, often with boulders, cobbles and pebbles around the edges of lagoons, or other areas that are exposed to wide salinity variations are unsuitable for colonisation by many species. Such areas may be colonised by a dense blanket of ephemeral green algae such as Enteromorpha spp., Chaetomorpha linum, Cladophora liniformis or Rhizoclonium riparium. This biotope may also contain some red seaweeds, such as Furcellaria lumbricalis, but always at low abundance (compare with PolFur). Amongst the filamentous green algae, grazing molluscs and solitary ascidians may be present. Infauna may typically include Corophium volutator, Heterochaeta costata, Tubificoides benedeni and other taxa suited for low/variable salinity environments.


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
Hediste diversicolor 7 61-80 %
Pygospio elegans 5 61-80 %
Arenicola marina 5 Occasional 21-40 %
Heterochaeta costata 19 Abundant 61-80 %
Tubificoides benedii 12 Abundant 61-80 %
Mysidae 15 Frequent 41-60 %
Corophium volutator 56 Super abundant 81-100 %
Corophium volutator 2 1-20 %
Carcinus maenas 2 Occasional 21-40 %
Gasterosteus aculeatus 3 Occasional 21-40 %
Beggiatoa 2 Occasional 21-40 %
Enteromorpha 5 Frequent 21-40 %
Enteromorpha intestinalis 18 Frequent 21-40 %
Chaetomorpha linum 9 Frequent 21-40 %
Cladophora 5 Frequent 21-40 %
Rhizoclonium riparium 3 Frequent 21-40 %
Derbesia marina 2 Common 1-20 %
Filamentous green algae 9 Common 21-40 %

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
97.06 IMX.FiG
96.7 SIR.FiG

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