Marine Special Areas of Conservation

Marine Sites in the Western Isles

North Rona

North Rona a remote and very exposed site is in the North Atlantic off the north west tip of mainland Scotland. The islands are rarely disturbed by human activities in the grey seal breeding season. Seals 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 the British annual pup production.

Loch Roag

Loch Siadar (Details to follow)

Tob Valasay (Details to follow)

St Kilda

The St Kilda archipelago lies west of theOuter Hebrides and supports one of the most extensive sea cave systems in the UK.Throughout the island group basalt and dolerite
dykes have eroded to form caves and tunnels above and below the water. The communities these support are diverse and reflect the degree of surge to which the caves are exposed. In shallow water in the extremes of surge, the cave walls are blanketed only by the sponge Myxilla encrustans. With a reduction in surge, species such as the northern anemone Phellia guasapata are common and thin encrusting sponges, bryzoans and the anemone Corynactis virids and Sagartia elegans are abundant. Microhabitats in the deeper cavesshow a wave gradient, with species usually found in more sheltered conditions, such as the fan worm Sabella pavonina and the burrowing anemone Cerianthus lloydii, present in the inner region. Rarely recorded nocturnal
species have also been found in the inner caves, most notibly the crab Bathynectes longipes and the anemone Arachnanthus sarsi.
The St Kilda archipelago is selected to represent extremely wave-exposed reefs off the coast of north-west Scotland. The islands are formed of hard igneous rock, which forms steep and vertical reefs around the entire island group. Littoral reef communities extend several meters above mean high water because of wave exposure, and populations of the uncommon exposed-shore fucoid Fucus disticus are present. Rock faces may extend sublittorally to reach depths of 50m and support communities characteristic of very exposed conditions on rock walls, overhangs and ledges, in surge gullies and amongst boulders. The clarity of the Atlantic sea water is high and dense kelp forests may occur as deep as 35m. The sublittoral fringe communities which, elsewhere, are found only at the low-water mark, may here reach to 12 m. Circalittoral rock is dominated by diverse communities of anemones, sponges and soft corals, with different species of sponge, hydroid and bryzoan occurring in the surge gullies and caves.

Loch nam Madadh

Loch nam Madadh lagoons form the most extensive and diverse saline lagoon system in the UK. The only comparable site is Obain Loch Euphoirt which is also a selected site. There are 13 lagoons in the Loch nam Madadh complex. These connect with the extensive system of freshwater lochs and lochans in the North Uist hinterland and the fjardic sealoch of Loch nam Madadh itself. There is a wide range of types from large, complex lagoons with several sills and basins to small, shallow single lagoons. Together they encompass the full transition from fresh water to fully marine conditions, through a series of basins and sills, and have an exceptionally wide range of habitat types with associated characteristic communities. Most have one or more basins floored with soft peaty mud, and there are usually boulders and cobbles around the margins. At the entrance to some of the lagoons there are rock and boulder waterfalls. Others have rock and coarse sediment rapids that flood at all states of the tide, and yet others have a percolation barrier. Within some lagoon basins there are various types of seagrass, tasselweed, green alga and stonewort communities. Other more complex lagoons have tidal rapids which support kelps and sea oak and their associated communities.

Loch nam Madadh large shallow inlets and bay is selected as a representative of the fjardic sealochs on coast of the north-west
Scotland. This site is exceptionally complex. It is predominantly shallow, with deeper water only in its entrance, and wave exposure grades from moderately exposed to extremely sheltered in the inner basins. There are numerous rocks and islands and at least 22 shallow sills and associated basins. The fjardic marine communities on this site are more diverse than on any other known site in the EC. There is a particularly wide variety of shallow tide-swept reefs and sediment habitats and communities. There are dense beds of knotted wrack Ascophyllum nodosum and a variety of kelp forests that illustrate the wave exposure gradient of the loch. The large shallow inlets and bay transform into a complex lagoon system in its upper reaches.

Key sub-features of the lagoons habitat:

• Intertidal rapids and waterfalls
• Micro-tidal range in inner basins
• Halocline showing a marked interface between different water salinities
• Tasselweed and seagrass beds and their associated communities
• Plants of high conservation value (rare) within shallow subtidal brackish water on soft sediment. e.g. rare foxtail stonewort communities

Key sub-features of the large shallow inlets and bay habitat:

• Rapid communities in subtidal and intertidal, bedrock, boulder and coarse sediment
• Extensive areas of coarse sediment and associated comunities
• Maerl beds in rapids or tideswept subtidal coarse sediment
• Sea cucumbers in shallow, subtidal, soft sediment
• Algal mats and associated communities
• Sea pen beds in deep, soft sediment
• Intertidal reef and foreshore communities
• Deep water reef communities on silty boulders or bedrock
• A range of kelp forest/park communities

The Monarchs

The Monach Islands, Western Isles, Scotland offer a wide area of largely undisturbed habitat for breeding seals who have easy access to grassy swards and dunes systems of the island. These islands hold the largest breeding colony of grey seals in the UK, with 25% of the annual pup production.

Loch Euphort

Details to follow.