Shallow kelp community found on sand and slightly gravelly sand, in moderately exposed and sheltered conditions, with weak tidal currents. The community is characterised by occasional Laminaria saccharina with an undergrowth of red algae. Characteristic red seaweeds, as with A5.5212, include Plocamium cartilagineum, Polyides rotundus, Polysiphonia elongate and Lomentaria clavellosa. Coralline encrusting algae is much less important in this biotope as a result of a lack of suitable substrate. Brown algal species present, as with other subunits of A5.521, include Desmarestia spp., Dictyota dichotoma and Chorda filum, all at low abundance. The ubiquitous green seaweed Ulva sp. may also be present. The sandy substrate is home to a variety of typical sand dwelling infauna including polychaetes (Scoloplos armiger, Exogone hebes, and Aricidea minuta), amphipods (Ampelisca brevicornis), and bivalves (Lucinoma borealis and Abra alba). Arenicola worm casts and Lanice worm tubes may be visible at the sediment surface.