3 results for 'CR.LCR.BrAs.AmenCio'
CR.LCR.BrAs.AmenCio Solitary ascidians, including Ascidia mentula and Ciona intestinalis, on wave-sheltered circalittoral rock
This biotope predominantly occurs on the upper faces of wave-sheltered (often sealochs) circalittoral bedrock, boulder and cobble slopes with little tidal flow. Apart from the solitary ascidians Ciona intestinalis and Ascidia mentula, this biotope has a rather barren, pink appearance (due to the encrusting red algae), possibly due to grazing pressure from the sea urchin Echinus esculentus. Other organisms found encrusting the rocky surface include the polychaete Spirobranchus triqueter and the cup coral Caryophyllia smithii. Other species occasionally encountered include Alcyonium digitatum, Asterias rubens, Pagurus berhardus, Crossaster papposus, Antedon bifida and Metridium senile. Crustaceans such as Munida rugosa and Cancer pagurus may be recorded in crevices. Two variants of this biotope exist: AmenCio.Ant and AmenCio.Bri. AmenCio.Bri occurs where is a dense carpet of brittlestars which sometimes completely cover the rocky substratum. Species present include Ophiothrix fragilis, Ophiocomina nigra and Ophiura albida.
CR.LCR.BrAs.AmenCio.Ant Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock
This variant occurs on circalittoral bedrock or boulder slopes in generally wave-sheltered conditions (often in sea lochs) with little tidal flow. It is frequently found on vertical or steeply-sloping rock. Apart from the large ascidians, Ascidia mentula and Ciona intestinalis, the rock surface usually has a rather sparse appearance. Scyphistomae larvae are often present on any vertical surfaces. Grazing by the sea urchin Echinus esculentus leaves only encrusting red algae (giving the bedrock/boulder substratum a pink appearance), cup corals Caryophyllia smithii and the keelworm Spirobranchus triqueter. There may be a few hydroid species present, such as Nemertesia spp. and Kirchenpaueria pinnata, occasional Alcyonium digitatum and occasional Metridium senile. Barnacles Balanus spp. and the colonial ascidian Clavelina lepadiformis also occasionally occur. At some sites, echinoderms such as the crinoid Antedon spp., the starfish Crossaster papposus and Asterias rubens and the brittlestar Ophiothrix fragilis (in low densities) may be found. The squat lobster Munida rugosa is likely to be found in crevices, under boulders, and the hermit crab Pagurus bernhardus may be observed moving around the rock surface. The brachiopod Novocrania anomala is frequently observed (especially where this biotope occurs shallower than NeoPro for example). The saddle oyster Pododesmus patelliformis may occasionally be seen attached to the rock/boulder face.
CR.LCR.BrAs.AmenCio.Bri Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata
This biotope is typically found on wave-sheltered sites (although it may be found in wave-exposed through to extremely wave-sheltered conditions), on circalittoral mixed substrata (Bedrock, boulders, cobbles, pebbles and gravel), subject to moderately strong to weak tidal streams. This biotope often has a silty appearance in parallel with AmenCio.Ant but is characterised by a dense carpet of brittlestars (Ophiothrix fragilis, Ophiocomina nigra and to a lesser extent Ophiura albida) which virtually cover the seabed. Where the underlying substratum is visible, pink coralline crusts and the white calcareous tubes of the keelworm Spirobranchus triqueter are often observed. Hydroids and bryozoans are scarce, perhaps partly due to the smothering effect of the brittlestars and possibly due to the grazing pressure of the sea urchin Echinus esculentus which is occasionally recorded. Other echinoderms present include Asterias rubens and Crossaster papposus. The solitary ascidian Ciona intestinalis may be seen attached to isolated rocks and boulders, whilst on the tops and sides of larger boulders, dead man's fingers Alcyonium digitatum may be recorded. The hermit crab Pagurus bernhardus is often recorded, whilst under boulders and in crevices the claws belonging to the long-clawed squat lobster Munida rugosa may be seen.