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Lower eulittoral bedrock and stable boulders on moderately exposed to sheltered shores with a canopy of the wrack Fucus serratus and an associated fauna consisting of the limpet Patella vulgata, the barnacle Semibalanus balanoides, the whelk Nucella lapillus, the anemone Actinia equina and the sponge Halichondria panicea. Green seaweeds such as Ulva intestinalis and Ulva lactuca are usually present among/beneath the F. serratus canopy. Three variants of this biotope are described. These are: F. serratus with red seaweeds (Fser.R) and F. serratus with under-boulder communities (Fser.Bo) with sponges. Lastly, a F. serratus and piddocks community on soft rock has been identified (Fser.Pid). Dense F. serratus with fewer red seaweeds occurs on more sheltered shores (Fserr).

Moderately exposed lower eulittoral bedrock characterised by mosaics of the wrack Fucus serratus and turf-forming red seaweeds including Osmundea pinnatifida, Mastocarpus stellatus or Corallina officinalis. The hydroid Dynamena pumila can occur in dense populations on the F. serratus fronds whilst the sponge Halichondria panicea can cover the bedrock beneath. Underneath the canopy a number of other red seaweeds may be present including Palmaria palmata, Lomentaria articulata,Membranoptera alata and Chondrus crispus. Green seaweeds such as Cladophora rupestris, Ulva intestinalis and Ulva lactuca are present though usually in small numbers. In addition, such shores provide a greater number of permanently damp refuges between the stones and underneath the seaweed canopy. Within these micro-habitats species such as the limpet Patella vulgata, the barnacle Semibalanus balanoides or the whelk Nucella lapillus can be found in lower abundance than higher up the shore. If a few boulders are present then the winkle Littorina littorea and the crab Carcinus maenas can be found on or underneath the boulders.

The lower eulittoral zone on soft rock shores (e.g. chalk) characterised by the wrack Fucus serratus. Much of the community associated with this biotope is the same as the biotope Fserr.FS, but certain taxa are specific to the soft underlying substrata. Rock-boring fauna including the piddocks Barnea spp., Pholas dactylus and Hiatella arctica can occur in dense aggregations. Burrowing polychaetes such as Polydora spp. can also occur in high numbers only visible due to their long, slender palps waving in the water as they occupy holes in the top few centimetres of the rock. A dense red algal turf occurs beneath the F. serratus and includes Gelidium pusillum, Osmundea pinnatifida, Palmaria palmata, Lomentaria articulata and Rhodothamniella floridula, but also calcareous algae such as Corallina officinalis and coralline crusts including the red-violet encrusting algae Phymatolithon lenormandii are present. Infaunal taxa such as various amphipods may be common amongst the seaweeds. The empty piddock holes may provide a refuge for species such as the anemone Actinia equina and the mussel Mytilus edulis while the barnacle Semibalanus balanoides, the limpet Patella vulgata can be present on the surface of the soft rock. The whelk Nucella lapillus, the winkles Littorina littorea and Littorina fabalis and the top shell Steromphala cineraria are all present on the soft rock among the seaweeds. The high number of characterising species is partly caused by the low number of records used to define this biotope. The high % frequency of occurrence is partly a result of the low number of records. More data is needed to validate this biotope description.

Exposed to moderalety exposed lower eulittoral boulders with the wrack Fucus serratus community of a high species richness as the presence of the boulders increases the micro-habitat diversity. The upper surfaces of the boulders are colonised by a very similar fauna to the other F. serratus biotopes, including species such as the limpet Patella vulgata, the whelk Nucella lapillus, the anemone Actinia equina and the barnacle Semibalanus balanoides. The shaded sides of the boulders are, depending on environmental conditions, often colonised by a variety of foliose red seaweeds, including Mastocarpus stellatus, Lomentaria articulata, Osmundea pinnatifida, Palmaria palmata and Chondrus crispus. Coralline algae such as Corallina officinalis and coraline crusts, as well as the green seaweeds Ulva intestinalis and Ulva lactuca, can be found underneath the F. serratus canopy or in patches on the boulders. The species composition underneath the boulders varies considerably depending on the underlying substratum. On muddy shores the fauna living under the boulders may be limited to a few infaunal species, such as the polychaete Cirratulus cirratus. Where more space is available beneath the boulders there may be a rich assemblage of animals. Characteristic mobile species include the crabs Porcellana platycheles and Carcinus maenas. Also present on and beneath the boulders are the tube-forming polychaete Spirobranchus triqueter, spirorbid polychaetes and a few winkles such as Littorina and Littorina littorea or even the top shell Steromphala cineraria. Encrusting colonies of the sponge Halichondria panicea are also typical of the undersides of boulders, while the hydroid Dynamena pumila colonies can be found on the F. serratus fronds. The richest examples of this biotope also contain a variety of brittlestars, ascidians and small hydroids.