Verrucaria maura on very exposed to very sheltered upper littoral fringe rock

Description (English)

Upper littoral fringe bedrock, boulders and stable cobbles on very exposed to very sheltered shores which have a blanket covering of the black lichen Verrucaria maura. The winkle Littorina saxatilis is often present. Due to the nature of this biotope it is species poor, but occasionally a range of species may be present in low abundance. These species include the yellow lichen Caloplaca marina and the winkle Melarhaphe neritoides, the barnacles Chthamalus montagui and Semibalanus balanoides or the ephemeral seaweeds Porphyra umbilicalis and Enteromorpha spp. can be present in low abundance (see B3.1131). If one or more of these species is present compare with B3.1131. On northern shores Littorina saxatilis var. rudis can dominate along with the occasional presence of the lichens Verrucaria mucosa and Xanthoria parietina. V. maura can be found overlying stable mud in N. Ireland sea loughs.
Situation: The black lichen zone is normally found below the yellow and grey lichen zone (B3.111). In very sheltered areas there is not always a clear transition from one zone to the next and a mixed zone of B3.111 and B3.1132 is common. The wrack Pelvetia canaliculata can occur on these more sheltered shores. With increasing wave exposure the two lichen zones become wider and more distinct, and B3.1132 gives way to a lichen and barnacle dominated community (B3.1131) in the lower littoral fringe.
Temporal variation: In areas with nitrate enrichment V. maura can be overgrown by the small green seaweed Prasiola stipitata (B3.112) which reaches its maximum abundance during the winter months. It generally dies out during the summer in southern Britain, reverting the biotope to B3.1132.

Source: EUNIS habitat classification