Loch Sunart is a long, narrow, winding loch comprised of a series of interconnecting basins which plunge to a depth of 124 metres. The loch is exceptionally rich and diverse in marine life due to the complexity of the system, with its many channels and sills and the differences in exposure along the 31 kilometres of its length.
Species from both northern and southern waters, not usually found together, meet in Loch Sunart where their ranges overlap. For example, red sea fingers (a southern species) flourish on steeply plunging, deep underwater cliffs, at the northerly limit of their range. At the same time, small snow-white spiky anemone and northern sea fan (both northern species) occur in the loch, at the southern limit of their range.
The floors of the deep basins are covered with mud and support forests of sea-pens, some of which can reach 2 metres tall. Burrowing into the mud are crabs and prawns such as the Dublin Bay prawn or Norway lobster, an important catch for local fisherman. Beds of brittlestars also occur on the loch floor.
On the basin sides, and the towering underwater pinnacles within the loch, vertical and overhanging bedrock cliffs plunge sharply into the depths. These ‘reefs’ provide a home to a myriad of thriving organisms. Massive grey elephant’s ear sponges jostle for space with dead man’s fingers, seasquirts and cup corals for a place to anchor.
Elsewhere in the loch, flame shells (up to four hundred per square metre) and horse mussels are packed in so tightly that they form reefs themselves on which other marine creatures thrive.