Description of biotope or habitat type
Ascophyllum nodosum on full salinity mid eulittoral mixed substrata
Habitat (physical) description
|Salinity||Full (30-35 ppt)|
|Wave exposure||Sheltered, Very sheltered, Extremely sheltered|
|Substratum||Mixed cobbles, boulders and pebbles on sediment|
|Zone||Eulittoral - mid|
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.
Sheltered to extremely sheltered full salinity mixed substrata (cobbles, boulders and pebbles on sediment) characterised by a canopy formed by a mosaic of the wracks Ascophyllum nodosum and Fucus vesiculosus. The red seaweed Polysiphonia lanosa can often be found as an epiphyte on the A. nodosum. The mussel Mytilus edulis often occurs in clumps, and provides further suitable substrata for the attachment of fucoids and red and green seaweeds such as Polysiphonia spp. and Enteromorpha intestinalis or the barnacle Semibalanus balanoides. Winkles are common and Littorina littorea and Littorina obtusata/mariae may occur in high densities, while species such as the limpet Patella vulgata, the crab Carcinus maenas and the whelk Nucella lapillus may occur on and around the boulders. Gammarids can be found underneath the boulders or among the seaweeds, while tube-forming spirorbids are found on the boulders, shells or on the F. vesiculosus. Infaunal species including the polychaetes Arenicola marina and Lanice conchilega may occur in the sediment between the cobbles.
A sparse S. balanoides, P. vulgata and L. littorea community (BLitX) can occur above this biotope. On shores with a proportion of smaller cobbles and boulders, large A. nodosum plants become uncommon and F. vesiculosus dominates the canopy (Fves.X). F. vesiculosus also tends to replace A. nodosum in areas with freshwater influence. Below this biotope are either a Fucus serratus dominated biotope (Fserr.X) or a M. edulis dominated biotope (Myt.Myt).
A. nodosum communities tend to be stable due to longevity of the individual A. nodosum, but because of the mixed substrata some variation in the densities of F. vesiculosus and A. nodosum can be expected.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Semibalanus balanoides||6||Occasional||61-80 %|
|Carcinus maenas||4||Occasional||41-60 %|
|Littorina obtusata/mariae||3||Common||21-40 %|
|Patella vulgata||4||Occasional||41-60 %|
|Littorina littorea||8||Occasional||61-80 %|
|Nucella lapillus||2||Occasional||41-60 %|
|Mytilus edulis||3||Occasional||41-60 %|
|Polysiphonia lanosa||5||Frequent||41-60 %|
|Ascophyllum nodosum||33||Abundant||81-100 %|
|Fucus vesiculosus||13||Frequent||81-100 %|
|Enteromorpha intestinalis||2||Occasional||41-60 %|