Papa Stour marine cSAC Sea Caves

Large boulders in the mouth of the caves are covered by breadcrumb sponges and have very few other animals. The nearby cave walls are mainly covered with crusts of barnacles and sea firs. Severe scour during the heavy winter storms is thought to reduce the number of different animals that can survive in these caves.

Kirstan's or Christie's Hole is probably the most well known of the caves within Papa Stour cSAC. The entrance to which is guarded by a tall stack. Parts of the roof of the cave have collapsed and this has resulted in most of the cave being fairly well lit, including the beach at the far end.

The inner walls of Kirstan's Hole are, like many caves around Papa Stour, covered in gooseberry sea squirts, lace and breadcrumb sponges. Some mobile animals also manage to survive the strong, fast water movements within the cave. These include squat lobsters, edible crabs, brittlestars, common starfish and also a starfish known as a Bloody Henry because of its bright purple colour.

Entering the cave the steep, almost vertical walls are covered with sheets of brightly coloured jewel anemones, plumose anemones and white calcareous lace sponge. The rock walls close to the sea bed are scoured clean with only a few animals able to survive, in particular the sand tolerant Dahlia anemone (see picture under cave 5). Sponges, anemones and sea firs, with occasional crusts of coralline algae cover the walls above the zone of scour. Right at the back of on the sea bed is an area of sand where hermit crabs live. The feeding tubes of worms also stick up out into the water.

On the overhanging ledges near the cave entrance sheets of sponges cover the walls intermixed with corraline crusts and small growths of red algae. Near the sea bed keel worms grow attached between the barnacles, sea squirts and sponges. Above this on the vertical walls the communities are similar to those on the overhangs although with the addition of gooseberry sea squirts.

Close to the entrance the cave walls are dominated by a turf of different species of sponges and sea squirts. Anemones such as dahlia and plumose anemones grow with red algae and coralline crusts. Inside the caves a mixture of sponges from gooseberry to purse to breadcrumb sponge line the walls. Many keel worms and some anemones can also be seen.