The Firth of Lorn SAC encompasses a complex group of islands, sounds and inlets characterised by some of the strongest tidal streams in the UK. The Gulf of Corryvreckan, Bealach a’Choin Ghlais (Pass of the Grey Dogs) and the Sounds of Clachan, Cuan and Luing are some of the most outstanding tide-swept areas in the NE Atlantic. The rich diversity of the tide-swept rocky reefs makes the Firth of Lorn SAC an excellent example of an area with this type of habitat.
Rocky reefs are widespread in northern and southern Europe and occur widely around the UK coast. They are very variable in form and in the communities that they support. Rocky reefs are generally sub-littoral but may extend as an unbroken transition to the intertidal zone, where they are exposed to the air at low tide
In the Firth of Lorn, rocky reefs extend from the intertidal zone into considerable depths (over 250 m) in many places. Reefs range from those exposed to turbulent tidal streams to those sheltered from waves and currents. In between are areas moderately exposed to wave action and tidal flow, which is where the greatest variety of fauna and flora are found. A rapid transition in communities occurs with the deceleration of tidal streams making the area and the associated communities and species amongst the most diverse in both the UK and Europe.