Fucus spiralis on sheltered upper eulittoral rock

Description (English)

Sheltered upper eulittoral bedrock is typically characterised by a band of the spiral wrack Fucus spiralis overlying the black lichen Verrucaria maura. Underneath the fronds of F. spiralis and the occasional Pelvetia canaliculata is a community consisting of the limpet Patella vulgata, the winkles Littorina saxatilis and Littorina littorea and the barnacle Semibalanus balanoides. The rock surface can often be covered by the red crust Hildenbrandia rubra. During the summer months the ephemeral green seaweed Enteromorpha intestinalis can be common. Two variants have been described: Upper eulittoral bedrock characterised by F. spiralis, the black lichen Verrucaria maura and the olive green lichen Verrucaria mucosa (unit MA1-23C1). Upper eulittoral mixed substrata characterised by F. spiralis with occasional clumps of the wrack Pelvetia canaliculata (unit MA1-23C2). Note that a F. spiralis biotope in variable salinity conditions (MA1-252) has also been descibed.
Situation: This zone usually lies below a zone dominated by the wrack (units MA1-241: MA1-23B), but occasional clumps of P. canaliculata may be present (usually less than common) amongst the F. spiralis. In areas of extreme shelter, such as in Scottish sea lochs, the P. canaliculata and F. spiralis zones often merge together forming a very narrow band. MA1-23C occurs above the wracks Ascophyllum nodosum (MA1-23E) and/or Fucus vesiculosus (MA1-23D) zones and these two fucoids may also occur, although F. spiralis always dominates. Vertical surfaces in this zone, especially on moderately exposed shores, often lack the fucoids and are characterised by a barnacle-limpet dominated community (MA1-223).

Source: EUNIS habitat classification