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Marine Habitat Classification

Description of biotope or habitat type

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   Ascophyllum nodosum with epiphytic sponges and ascidians on variable salinity infralittoral rock

Physical habitat description

Salinity Variable (18-35 ppt)
Wave exposure Extremely sheltered
Tidal streams Weak (>1 kn), Very weak (negligible)
Substratum Bedrock; boulders and cobbles
Zone Infralittoral
Depth Band 0-5 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 IR.LIR.Lag.AscSpAs <I>Ascophyllum nodosum</I> with epiphytic sponges and ascidians on variable salinity infralittoral 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.


Dense subtidal stands of Ascophyllum nodosum, heavily epiphytised by sponges and ascidians in lagoon-like habitats. The wracks Fucus vesiculosus and Fucus serratus can be present along with the brown seaweed Chorda filum and the red seaweed Polyides rotunda. The crab Carcinus maenas can be present between the A. nodosum holdfasts along with the shrimps Mysidae.


Nearby rock often supports similar biotopes of submerged fucoids and green seaweeds (FChoG). Slightly deeper rock often supports Saccharina latissima (Lsac.Ft), usually surrounded by more extensive areas of sediment. Seagrass beds thrive well in the muddy sand of these lagoons and often cover large areas. They include both Ruppia maritima and Zostera subg. Zostera marina (Rup and Zmar).

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Ascophyllum nodosum 40 Frequent 81-100%
Carcinus maenas 21 Occasional 81-100%
Polyides rotunda 7 Frequent 41-60%
Chorda filum 4 Frequent 41-60%
Fucus serratus 4 Frequent 41-60%
Fucus vesiculosus 4 Frequent 61-80%
Mysidae 3 Occasional 41-60%

Similar biotopes or habitat types

Not applicable or unknown.

Classification history of this biotope or habitat type

Classification version Code
1997 (97.06) SLR.AscSAs

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