Description of (Mastocarpus stellatus) and (Chondrus crispus) on very exposed to moderately exposed lower eulittoral rock
Exposed to moderately exposed lower eulittoral vertical to almost horizontal bedrock characterised by a dense turf of Mastocarpus stellatus and Chondrus crispus (either together or separately). Beneath these foliose seaweeds the rock surface is covered by encrusting coralline algae and the barnacle Semibalanus balanoides, the limpet Patella vulgata and spirorbid polychaetes. Other seaweeds including the red Lomentaria articulata and Osmundea pinnatifida, Palmaria palmata, Corallina officinalis and coralline crusts. The wrack Fucus serratus and the green seaweeds Enteromorpha intestinalis and Ulva lactuca may also be present though usually at a low abundance. Although both M. stellatus and C. crispus are widespread in the lower eulittoral and the sublittoral fringe, they occur only infrequently in a distinct band, or in large enough patches, to justify separation from A1.2141. Consequently, where only small patches of these species occur within a larger area of mixed red algal turf, then records should be assigned to more general mixed red algal turf biotope (A1 122; A1.123). M. stellatus can be present in high abundance in a number of biotopes (A1 122: A1.123; A1.2141 etc.) found on the shore. At least one other species normally co-dominates and records should be assigned to the appropriate biotope. Caution should be taken regarding the characterising species list due to the low number of records. More information needed to validate this description. Situation: This biotope can form a band above the main kelp zone, above Alaria esculenta (A3.111) or the mussel Mytilus edulis (A1.111) or within a F. serratus-red algal mosaic (A1.2141). Temporal variation: M. stellatus is more resistant to wave action than C. crispus and may therefore dominate more exposed shores; it can dominate vertical rock at very exposed sites (e.g. Mingulay, Outer Hebrides). On more sheltered shores, especially in the south-west, M. stellatus may give way to C. crispus which has a faster growth rate.