Description of biotope or habitat type
Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock
Habitat (physical) description
|Salinity||Reduced (18-30ppt), Low (<18ppt)|
|Wave exposure||Extremely sheltered|
|Tidal streams||Very weak (negligible)|
|Substratum||Bedrock; boulders, cobbles and pebbles|
|Depth Band||0-5 m|
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'
- Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat
Permanently submerged mixed fucoids on rock in lagoons. The main species are the wracks Fucus serratus and Fucus vesiculosus, but the brown seaweeds Chorda filum, Ascophyllum nodosum and Ectocarpaceae can be present as well. Red seaweeds are normally present and include Mastocarpus stellatus, Polyides rotundus, Chondrus crispus, Ceramium spp. and coralline crusts. A variety of green seaweeds is also present and include Enteromorpha spp., while dense patches of Cladophora rupestris may occur on vertical rock faces. The faunal component is restricted to the mussel Mytilus edulis, the polychaete Arenicola marina and the crab Carcinus maenas. Opossum shrimps Mysidae can be present as well. The kelp Laminaria saccharina is absent, possibly due to the low salinity conditions.
Nearby rock often supports similar biotopes of submerged fucoids (AscSpAs and FcerEnt) or where salinity is further reduced ProtFur can occur. Slightly deeper rock often supports Laminaria saccharina (Lsac.Ft), usually surrounded by more extensive areas of sediment. Seagrass beds thrive well in the muddy sediments of the lagoons and often cover large areas. They include both Ruppia spp. and Zostera marina and some locations in the Outer Hebrides support dense beds of the nationally rare stonewort Lamprothamnion papulosum (Rup and Zmar). The sublittoral mud, which abuts most of the submerged rock, can become anoxic and covered by a bacterial mat of Beggiatoa spp. (Beg).
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Arenicola marina||2||Occasional||21-40 %|
|Carcinus maenas||3||Occasional||21-40 %|
|Littorina littorea||6||Frequent||41-60 %|
|Mytilus edulis||3||Occasional||21-40 %|
|Chondrus crispus||1||Occasional||21-40 %|
|Mastocarpus stellatus||2||Occasional||21-40 %|
|Polyides rotundus||2||Occasional||21-40 %|
|Chorda filum||3||Occasional||21-40 %|
|Ascophyllum nodosum||3||Occasional||21-40 %|
|Fucus serratus||30||Common||61-80 %|
|Fucus vesiculosus||12||Frequent||41-60 %|
|Enteromorpha intestinalis||3||Frequent||21-40 %|
|Cladophora rupestris||3||Frequent||21-40 %|
Not applicable or unknown.