Description of biotope or habitat type
Ascophyllum nodosum and Fucus vesiculosus on variable salinity mid eulittoral rock
Physical habitat description
|Variable (18-35 ppt)
|Very sheltered, Extremely sheltered
|Moderately strong (1-3 kn), Weak (>1 kn), Very weak (negligible)
|Bedrock; boulders; cobbles
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.
- 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'
Point data based on records in the UK Marine Recorder Snapshot.
Very sheltered to extremely sheltered mid eulittoral bedrock, boulders or cobbles subject to variable salinity characterised by an impoverished community dominated by a mixture of the wracks Ascophyllum nodosum and Fucus vesiculosus. Underneath the canopy are a few green seaweeds including Ulva intestinalis and Cladophora spp., while the red seaweed Vertebrata lanosa can be found as an epiphyte on A. nodosum. On the rock and among the boulders are the winkles Littorina littorea and Littorina saxatilis, the crab Carcinus maenas, the barnacles Semibalanus balanoides and Austrominius modestus and even the occasional mussel Mytilus edulis. Among the seaweeds and underneath the boulders a variety of gammarids can be found.
This biotope usually lies below the Fucus spiralis biotope (Fspi.VS) or the Fucus ceranoides dominated biotopes (Fcer) and above the variable salinity F. serratus dominated biotope (Fserr.VS), although on some shores a narrow zone of F. vesiculosus (Fves) may occur immediately above the A. nodosum. With increasing wave exposure the A. nodosum canopy can be more dense (Asc.FS).
A. nodosum can reach an age of 25 years and the communities are usually stable. F. vesiculosus or F. serratus can occur in patches where the A. nodosum has been removed.
|Relative importance of taxon for defining this community (%)
|Typical abundance - SACFOR scale
|% of core records where taxon was recorded
Similar biotopes or habitat types
Classification history of this biotope or habitat type