Mixed fucoids, Chorda filum and green seaweeds on reduced salinity Atlantic infralittoral rock

Description (English)

Permanently submerged mixed fucoids on rock in lagoons. The main species are the wracks Fucus serratus and Fucus vesiculosus, but the brown seaweeds Chorda filum, Ascophyllum nodosum and Ectocarpaceae can be present as well. Red seaweeds are normally present and include Mastocarpus stellatus, Polyides rotundus, Chondrus crispus, Ceramium spp. and coralline crusts. A variety of green seaweeds is also present and include Enteromorpha spp., while dense patches of Cladophora rupestris may occur on vertical rock faces. The faunal component is restricted to the mussel Mytilus edulis, the polychaete Arenicola marina and the crab Carcinus maenas. Opossum shrimps Mysidae can be present as well. The kelp Laminaria saccharina is absent, possibly due to the low salinity conditions.
Situation: Nearby rock often supports similar biotopes of submerged fucoids (units MB1-252 and MB1-254) or where salinity is further reduced unit MB1-253 can occur. Slightly deeper rock often supports Laminaria saccharina (unit MB1-23A2), usually surrounded by more extensive areas of sediment. Seagrass beds thrive well in the muddy sediments of the lagoons and often cover large areas. They include both Ruppia spp. and Zostera marina and some locations in the Outer Hebrides support dense beds of the nationally rare stonewort Lamprothamnion papulosum (units MB5-224 and MB5-223). The sublittoral mud, which abuts most of the submerged rock, can become anoxic and covered by a bacterial mat of Beggiatoa spp. (unit MB6-24C).

Source: EUNIS habitat classification