Description of [Neocrania anomala], [Dendrodoa grossularia] and [Sarcodictyon roseum] on variable salinity circalittoral rock
This variant typically occurs on lower circalittoral silty, bedrock or boulder cliffs and ridges in very wave-sheltered fjordic sealochs subjected to variable salinity regimes (such as Loch Etive, Scotland). In these sheltered conditions, there are frequently dense populations of the ascidian Dendrodoa grossularia, the brachiopod Neocrania anomala and to a lesser extent, the brachiopod Terebratulina retusa, which are able to tolerate the variable salinity. Other solitary ascidians that may be present include Ciona intestinalis, Corella parallelogramma, Ascidiella scabra, Ascidia mentula, Ascidia virginea and Polycarpa pomaria. The anemone Protanthea simplex is occasionally seen, although to a lesser extent than in unit A4.314, possibly due to the variable salinity. The hydroids Bougainvillia ramosa and Lafoea dumosa, the cup-coral Caryophilia smithii and Sarcodictyon roseum are occasionally present. The tubes formed by the polychaete Sabella pavonina may be observed standing erect from the rock surface. The rest of the rock surface is usually covered by encrusting red algae and the polychaete Pomatoceros triqueter and Protula tubularia. The sea cucumber Psolus phantapus may be found on the underside of boulders. Other species such as the hermit crab Pagurus bernhardus and the spider crab Hyas araneus may be found amongst the rock/boulders. The starfish Asterias rubens, Crossaster papposus, and Henricia spp. and the sea urchin Psammechinus miliaris are also recorded within this variant. The relatively bare, silty rock supports low numbers of a relatively few species. Although barren rock grazed by the sea urchin Echinus esculentus is found in other sea loch biotopes (see units A4.2145 and A4.2146), E.esculentus is virtually absent within A4.3142. Situation: Due to the variable or reduced salinity conditions present where this biotope is found, you tend to find reduced salinity kelp biotopes above A4.3142, such as A3.322 and A3.323. The very sheltered conditions give rise to muddy sediment slopes or plains beneath A4.314 (A5.3) where species such as the seapen Funiculina quadrangularis, the anemone Cerianthus lloydii and the Norway lobster Nephrops norvegicus are typically abundant.