On infralittoral mixed muddy substrata communities characterised by the kelp Laminaria saccharina and mixed filamentous and foliose red algae can be found. This biotope contains a number of sub-biotopes distinguished by the degree of either wave or tidal exposure. In moderately strong tidal streams in exposed areas Laminaria is sparse and dense stands of red seaweeds are found attached to the boulders and cobbles that make up a large proportion of the sediment (A5.5211). As the degree of wave and/or tidal exposure decreases there is a change in community structure, with the density of Laminaria and the diversity of red algal species increasing (A5.5212). As the environment becomes more stable a number of brown algal species are able to inhabit this environment and a rich infauna develops (A5.5213). In the most sheltered examples of this biotope a diverse muddy sediment infauna can be found and the 'Trailliella' phase of Bonnemaisonia hamifera may develop (A5.5214).