Low and variable salinity infralittoral mud with beds of Potamogeton pectinatus. Other associated species are broadly similar to that of unit A5.5343, with blankets of filamentous green algae such as Enteromorpha intestinalis, Cladophora liniformis and Rhizoclonium riparium. The grazing gastropod Potamopyrgus antipodarum is found in this biotope and juvenile Mytilus edulis have been observed settled on Potamogeton leaves and amongst the algae. The nationally scarce charaphyte Lamprothamnium papulosum may be found to some extent in this biotope but more often in neighbouring habitats (see Plaza & Sanderson 1997). Mysids, trout (Salmo trutta), and sticklebacks Gasterosteus aculeatus can be found swimming amongst the vegetation. Mya arenaria may be found in some examples of this biotope, but the infaunal component of this biotope requires further investigation but is likely to contain oligochaetes, Arenicola marina, Corophium volutator and Gammarus spp.