North Rona is a remote and very exposed island in the North Atlantic off the north-west tip of mainland Scotland and is designated for reefs and grey seals (Halichoerus grypus). Reefs are rocky marine habitats or biological concretions that rise from the seabed. They are generally subtidal but may extend as an unbroken transition into the intertidal zone, where they are exposed to the air at low tide. Intertidal areas are only included within this Annex I type where they are connected to subtidal reefs. Reefs are very variable in form and in the communities that they support. Two main types of reef can be recognised: those where animal and plant communities develop on rock or stable boulders and cobbles, and those where structure is created by the animals themselves (biogenic reefs) [1].
The islands are rarely disturbed by human activities in the breeding season. Grey seal Halichoerus grypus are found over much of the island and use many of the submerged sea caves that are found around the coast. North Rona supports the third-largest breeding colony in the UK, representing some 5% of annual UK pup production [2].
Looking out from a sea cave, North Rona. Scottish Natural Heritage.
[1] Reefs habitat account, JNCC
[2] North Rona SAC site summary, JNCC