Low or variable salinity habitats - Inshore and shelf subtidal sediments and Subtidal rock

The eight layers are:

1. Faunal communities on variable or reduced salinity infralittoral rock - Very few records of this habitat exists. Examples include Firth of Forth, Shetland and Outer Hebrides and some west coast sea lochs. Typically it comprises dense beds of blue mussels which support barnacles, sea firs and sea mats.
2. Kelp in variable or reduced salinity - Very few records occur outside Scotland where it is found in saline lagoons in Orkney, Shetland, the Hebrides and west coast of Scotland. The habitat is dominated by sugar kelp and various red and green seaweeds and is only found on very wave sheltered bedrock and boulders.
3. Submerged fucoids, green or red seaweeds (low salinity infralittoral rock) - This is a characteristic lagoon community dominated by dense seaweeds with a very restricted fauna due to the low salinity. It is unique to Scotland where there are numerous records from the Outer Hebrides, Orkney and Shetland. Scotland is of national importance for this habitat.
4. Sublittoral mud in low or reduced salinity (lagoons) - This is a very characteristic lagoon community comprising various short-lived species such as blow lugworms and mud shrimps. The beaked tasselweed (Ruppia) may also be present. Only a few records of this habitat exist outside Scotland where it is found in the Outer Hebrides, Shetland and within the Beauly Firth.
5. Baltic stonewort (Chara balthica) -  Found in three locations in the Outer Hebrides the Scottish populations are likely to be of national importance but threatened by habitat loss. Listed as Vulnerable on the Red Data Book of Britain and Ireland.
6. Bird's-nest stonewort (Tolypella nidifica) -  Scottish records from Loch of Stenness, Orkney and Loch an Duin and Loch an Strumore in the Outer Hebrides are the only British records. This species is declining throughout Europe. These sites are of national and probably international importance. Listed as Endangered on the Red Data Book of Britain and Ireland.
7. Foxtail stonewort (Lamprothamnium papulosum) - Recorded from North and South Uist in the Outer Hebrides. Of national importance with the Hebridean sites thought to represent the most secure global stronghold for this species. Listed as Near Threatened on the Red Data Book of Britain and Ireland.
8. Small brackish water snail (Hydrobia acuta neglecta) - Scattered records of this small snail occur on the west coast, the Outer Hebrides, Orkney and Shetland and in Montrose Basin on the east coast.