Description of biotope or habitat type
To understand more about what this page is describing, see How to use the classification. See also How to cite.
Ascophyllum nodosum on full salinity mid eulittoral mixed substrata
Physical habitat description
| Salinity | Full (30-35 ppt) |
|---|---|
| Wave exposure | Sheltered, Very sheltered, Extremely sheltered |
| Tidal streams | |
| Substratum | Mixed cobbles, boulders and pebbles on sediment |
| Zone | Eulittoral - mid |
| Depth Band | |
| 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.
- 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.
Description
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 Vertebrata 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 Ulva intestinalis or the barnacle Semibalanus balanoides. Winkles are common and Littorina littorea and Littorina 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.
Situation
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).
Temporal variation
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.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Ascophyllum nodosum | 33 | Abundant | 81-100% |
| Fucus vesiculosus | 13 | Frequent | 81-100% |
| Littorina littorea | 8 | Occasional | 61-80% |
| Semibalanus balanoides | 6 | Occasional | 61-80% |
| Vertebrata lanosa | 5 | Frequent | 41-60% |
| Carcinus maenas | 4 | Occasional | 41-60% |
| Patella vulgata | 4 | Occasional | 41-60% |
| Littorina | 3 | Common | 21-40% |
| Mytilus edulis | 3 | Occasional | 41-60% |
| Ulva intestinalis | 2 | Occasional | 41-60% |
| Nucella lapillus | 2 | Occasional | 41-60% |
| Gammaridae | 1 | Frequent | 21-40% |
| Polysiphonia | 1 | Occasional | 21-40% |
| Spirorbinae | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
LR.LLR.F.Asc.FS
Occurs on bedrock. Has a higher abundance and diversity of red seaweeds and species such as the hydroid Dynamena pumila and the lichen Verrucaria mucosa are present.
LR.LLR.FVS.AscVS
Occurs on bedrock or mixed substrata with variable salinity. Similar species composition but species, such as the hydroid D. pumila and the barnacle Austrominius modestus are usually present.
LR.HLR.FT.AscT
Occurs on rock and mixed substrata in fully marine conditions. Has a high abundance and diversity of red seaweeds and filter feeding species such as the sponges Leucosolenia spp. and Grantia compressa, the hydroid Clava multicornis and the sea squirt Dendrodoa grossularia.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 1995 | LMXD.ASC |
Photos
