Loch of Stenness

General site character

• Tidal rivers, Estuaries, Mud flats, Sand flats, Lagoons (including saltwork basins) (100%)
  

Annex I habitats that are a primary reason for selection of this site

• 1150 Coastal lagoons  * Priority feature

  Loch of Stenness has a single basin characteristic of Coastal lagoons in Orkney, and has features of both silled lagoons and lagoonal inlets. It is the largest brackish lagoon in the UK and is of particular importance on account of its large size, stability, reduced salinity regime and northern location. There is a salinity gradient in the lagoon, and communities representing sheltered marine, brackish and freshwater conditions are found. Loch of Stenness is predominantly sedimentary: the lagoon basin is floored by soft mud, while round the shoreline muddy sediments with sand and gravel grade into pebbles, cobbles and boulders. The soft sublittoral mud supports mats of filamentous green algae and large numbers of burrowing worms, and the bivalve Mya arenaria and the snail Hydrobia ulvae may be dominant. Littoral boulders are dominated by filamentous green algae or fucoid algae, with Fucus ceranoides, characteristic of brackish conditions, abundant in places. Submerged boulders in more saline areas of the lagoon support clumps of mussels Mytilus edulis, the brown alga Fucus serratus and species of foliose red and filamentous green algae. In the inner parts of the loch, where salinity is reduced, the cobbles and gravel support stands of beaked tasselweed Ruppia maritima, F. ceranoides and filamentous green algae. Extensive stands of pondweed Potamogeton spp. are present in areas of particularly low salinity.

Annex I habitats present as a qualifying feature, but not a primary reason for selection of this site

• Not Applicable

Annex II species that are a primary reason for selection of this site

• Not Applicable

Annex II species present as a qualifying feature, but not a primary reason for site selection

• Not Applicable