Northern sea fan and sponge communities

Northern sea fan communities comprise dense aggregations of the northern sea fan (Swiftia pallida) and the cup coral (Caryophyllia smithii) together with a wide range of other species occurring on upward-facing and vertical rock surfaces. S. pallida plays host to the nationally rare sea fan anemone Amphianthus dohmii. These communities are characteristic of the moderately exposed rocky habitats of the west coast and Outer Hebrides and occur below ~20m.

There are 4 layers: 

1. Caryophyllia smithii and Swiftia pallida on circalittoral rock - is a very species rich community supporting a range of soft corals, sea firs, sea mats, sea squirts etc. Recorded from a number of locations on the west coast and Outer Hebrides.

2. Mixed turf of hydroids and large ascidians with swiftia pallida and caryophyllia smithii on weakly tideswept circalittoral rock – is sparsely recorded with a restricted distribution in a few sea lochs and inlets on the west coast, especially around the Isle of Mull.  It represents a particularly diverse community of dense cup corals, sea firs, sea squirts, sea fans, sponges, soft corals, sea mats and feather stars, as well as sea cucumbers, squat lobsters and fish.

3. Deep Sponge Communities - are found off the west of the Hebrides and the north-east coast of Shetland as well as a few other locations along the west coast. They are very diverse communities with the majority of UK records from Scotland.

4. Northern Sea Fan - occurs in many sea lochs and inlets along the west coast of Scotland and the Outer Hebrides, from Loch Laxford in the north to Sound of Jura in the south, and out to St Kilda. It usually occurs at depths of 15-60 m but may occur up to 200m. Virtually all (97%) of UK records are from Scotland and as such is of national importance. It is also host to the nationally rare sea fan anemone Amphianthus dohrnii.