Description of biotope or habitat type

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   Mixed Laminaria hyperborea and Saccharina latissima forest on sheltered upper infralittoral rock

Description

Sheltered, often silted, upper infralittoral bedrock and boulder slopes with mixed kelps Laminaria hyperborea and Saccharina latissima and red seaweeds beneath. The kelp at these sheltered sites often has large `cape-form' fronds, which form a dense canopy over the seabed and are often epiphytised by the hydroid Obelia geniculata and the bryozoan Membranipora membranacea. Beneath the kelp, red seaweeds such as Delesseria sanguinea and Cryptopleura ramosa occur on top of encrusting coralline algae. Often, a dense algal turf of Bonnemaisonia hamifera (tetrasporophyte) carpets the rock. The stipes of L. hyperborea may be densely covered with seaweeds such as Phycodrys rubens, Plocamium cartilagineum and Porphyropsis coccinea. There can also be a prominent faunal component on the stipes including the solitary ascidian Clavelina lepadiformis and the colonial ascidian Botryllus schlosseri. Brown seaweeds, occurring here in low abundance, include Dictyota dichotoma. The kelp Saccorhiza polyschides may also occur but rarely in equal abundance to L. hyperborea or L. saccharina. Beneath the kelp canopy, the faunal component is generally less diverse than the more exposed kelp forests (Lhyp). The silted rock supports a sparse fauna of gastropods Steromphala cineraria and Calliostoma zizyphinum, the tube-building polychaete Spirobranchus triqueter and occasional starfish Asterias rubens and the urchin Echinus esculentus. Steeper, less silted rock, may have the anthozoans Caryophyllia smithii and Alcyonium digitatum.Sheltered, often silted, upper infralittoral bedrock and boulder slopes with mixed kelps Laminaria hyperborea and Saccharina latissima and red seaweeds beneath. The kelp at these sheltered sites often has large `cape-form' fronds, which form a dense canopy over the seabed and are often epiphytised by the hydroid Obelia geniculata and the bryozoan Membranipora membranacea. Beneath the kelp, red seaweeds such as Delesseria sanguinea and Cryptopleura ramosa occur on top of encrusting coralline algae. Often, a dense algal turf of Bonnemaisonia hamifera (tetrasporophyte) carpets the rock. The stipes of L. hyperborea may be densely covered with seaweeds such as Phycodrys rubens, Plocamium cartilagineum and Porphyropsis coccinea. There can also be a prominent faunal component on the stipes including the solitary ascidian Clavelina lepadiformis and the colonial ascidian Botryllus schlosseri. Brown seaweeds, occurring here in low abundance, include Dictyota dichotoma. The kelp Saccorhiza polyschides may also occur but rarely in equal abundance to L. hyperborea or L. saccharina. Beneath the kelp canopy, the faunal component is generally less diverse than the more exposed kelp forests (Lhyp). The silted rock supports a sparse fauna of gastropods Steromphala cineraria and Calliostoma zizyphinum, the tube-building polychaete Spirobranchus triqueter and occasional starfish Asterias rubens and the urchin Echinus esculentus. Steeper, less silted rock, may have the anthozoans Caryophyllia smithii and Alcyonium digitatum.

Situation

This biotope occurs below Laminaria digitata on the sheltered sublittoral fringe (Ldig.Ldig) or a mix of L. saccharina and L. digitata in very sheltered conditions (Lsac.Ldig). It can also be found on isolated rock exposures amid a sediment seabed (VirOphPmax or PhiVir). Where suitable substrata allow, the kelp thins out with increased depth to form a park below the forest (LhypLsac.Pk).

Temporal variation

Unknown.

Characterising species

Similar biotopes or habitat types

IR.LIR.K.LhypSlat.Pk

Found in deeper water below the kelp forest and has a lower abundance of kelp and red seaweeds. The abundance of Laminaria spp. in the kelp park is typically only Frequent. The fauna remains much the same as the forest, unless there is a greater fraction of mixed substrata in the deeper park, in which case there may be an increase in infaunal species, brittlestars and starfish. The assemblage of red seaweeds does not differ greatly from that of the forest.

IR.LIR.K.Slat.Ft

Generally occurs in more sheltered, siltier conditions and lacks L. hyperborea.

IR.LIR.K.LhypSlat.Gz

A greater number of grazing echinoderms reduce the abundance of foliose red seaweeds and kelp (Common-Frequent).

IR.LIR.K.LhypCape

Cape-form of L. hyperborea on very silted rock (particularly in extremely sheltered sealochs of western Scotland). S. latissima can be present but does not co-dominant as in IR.LIR.K.LhypSlat.

Classification history of this biotope or habitat type