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Sheltered to extremely sheltered mid eulittoral rock with the wrack Ascophyllum nodosum. The red seaweed Vertebrata lanosa is often found growing as an epiphyte on the A. nodosum fronds while disturbed areas among the A. nodosum is colonised by the wrack Fucus vesiculosus and the green seaweed Ulva intestinalis.e barnacle Semibalanus balanoides, the limpet Patella vulgata and Littorina littorea can all be found on the bedrock underneath the A. nodosum canopy along with coralline crusts. The whelk Nucella lapillus can be found preying on the barnacles and limpets. Three variants of this biotope are described. These are: full salinity (Asc.FS), mixed substrata (Asc.X) and the loose lying growth form A. nodosum ecad mackaii found on very sheltered shores (Asc.mac). To other biotopes has been identified as well tide-swept (AscT) and variabel salinity (AscVS).

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.

Bedrock, stable boulders and cobbles in the mid-eulittoral zone of moderately exposed to extremely sheltered shores, in fully marine conditions, characterised by a dense canopy of the wrack Ascophyllum nodosum. Another wrack Fucus vesiculosus may in some places co-dominate the canopy. The hydroid Dynamena pumila can form colonies on the wracks F. vesiculosus and Fucus serratus. Variations in the ratio of A. nodosum and F. vesiculosus in the overlying canopy have little effect on the under-storey species. Beneath the canopy are a diverse array of filamentous and foliose red seaweeds, including Mastocarpus stellatus, Chondrus crispus, Gelidium pusillum and coralline crusts. The filamentous red seaweed Vertebrata lanosa is usually present on A. nodosum as an epiphyte. A few green seaweeds including Cladophora rupestris and Ulva spp. are also present in moderate to low densities. On the bedrock and boulders beneath the seaweed canopy is a fauna including the barnacle Semibalanus balanoides, the limpet Patella vulgata, tube-forming spirorbid polychaetes and the anemone Actinia equina. The latter can be present in damp cracks and crevices. On and among the seaweeds are mobile species including the winkles Littorina littorea and Littorina obtusata, the whelk Nucella lapillus or even the crab Carcinus maenas. At the top of the A. nodosum zone there might be the occasional presence of the olive green lichen Verrucaria mucosa.