⌘K
Biotope - Typologie Européenne EUNIS
B3.11 - Niveau 4 : Lichens ou petites algues vertes sur roche du supralittoral et de la frange littorale
Description
Lichen communities typically form a distinct zone or band in a 'splash' zone on most rocky shores. This splash zone occurs above the main intertidal zone (i.e. that subject to regular covering by the tide) and blends into angiosperm-dominated communities of coastal (terrestrial) habitats at its upper limits. The width of the splash zone varies considerably, depending on the degree of exposure of the shore to wave action. On very exposed coasts the zone is very wide, extending 10s of meters up cliffs, whilst in very sheltered sites it may be only a metre or so high. Several biotopes have been identified. Yellow and grey lichens such as Xanthoria parietina, Caloplaca marina, Caloplaca thallincola or Ramalina sp. dominate the supralittoral rock (B3.111) with the distinctive black band of Verrucaria maura occurring below in the littoral fringe (B3.1131, B3.1132). Small green seaweeds can sometimes be found in this splash zone, where localised conditions allow growth in what would otherwise be inhospitable conditions for seaweeds. Such an example is the green seaweed Prasiola stipitata which occurs in areas of nitrate enrichment from nearby roosting seabirds (B3.112). The littoral fringe on soft rock can be characterised by the green seaweed Blidingia minima (B3.114) while steep and vertical rock influenced by freshwater in the littoral fringe can be dominated by the green seaweeds Ulothrix flacca, Urospora penicilliformis and Urospora wormskioldii (B3.115). The winkle Littorina saxatilis is one of the few 'marine' species found in this environment.
Situation: This habitat type is found in the littoral fringe and the supralittoral zone on all rocky shores if there is sufficient seawater spray to maintain a viable community.
Taxons (Liens actifs si espèces présentes)
B3.112 - Niveau 5 : Prasiola stipitata sur roche du supralittoral et de la frange littorale enrichie en nitrates
Description
Exposed to moderately exposed bedrock and large boulders in the supralittoral and littoral fringe that receives nitrate enrichment from nearby roosting sea birds and is characterised by a band or patches of the ephemeral tufty green seaweed Prasiola stipitata or Prasiola spp. This typically grows over the black lichen Verrucaria maura in the littoral fringe or yellow and grey lichens in the supralittoral zone. In damp pits and crevices, species such as the winkle Littorina saxatilis, amphipods and halacarid mites are occasionally found. B3.112 often covers a smaller area than 5m x 5m and care should be taken to notice/record this biotope. The biotope can be associated with artificial substrata such as septic tanks, and in supralittoral areas influenced by sewage seeps or agricultural run-off.
Situation: This biotope is found at the top of rocky shores in the splash zone below colonies of nesting or roosting birds growing. B3.112 may also be found at the entrances to and on the ceilings of littoral caves or in patches on large boulders, where birds may be roosting. It can be found in the B3.111 or B3.1132 zones.
Temporal variation: P. stipitata reaches its maximum abundance during the winter months. It generally dies out during the summer in southern Britain, when the biotope reverts to either B3.111 or B3.1132. In the cooler northern areas it may be present all year round.
Taxons (Liens actifs si espèces présentes)
Prasiola stipitata Suhr ex Jessen, 1848 ( Esp. caract. )
Analyse Ecologie du milieu (En fonction des espèces présentes)