Clyde Sea Sill
Nature Conservation Marine Protected Area
United Kingdom: Scotland
The Clyde Sea Sill possible MPA stretches from the Mull of Kintyre to Corsewall Point on the Rhinns of Galloway. Below the surface in this region, the water shallows dramatically where the northern channel (between Scotland and Northern Ireland) becomes the Firth of Clyde at a distinctive sill on the seabed.
The seawater in the northern channel is much cooler than that of the Firth of Clyde due to the significant difference in the depth of these two water bodies. The boundaries between water bodies of different temperature or salinity often lead to the occurrence of fronts. Fronts can concentrate nutrients and plankton creating feeding hotspots for fish which in turn attract marine predators such as whales and seabirds.
The cliffs of Sanda Island, an existing Site of Special Scientific Interest (SSSI) for breeding birds, are home to over 400 breeding black guillemots. Unlike other auks the black guillemot is typically found feeding close inshore, rarely dispersing far from its breeding area even in winter. Black guillemot breeding areas therefore rely on the continuing productivity of rich feeding grounds such as the Clyde Sea Sill nearby.
The seabed within the pMPA (Possible Nature Conservation MPA) contains areas of coarse sandy sediment. The sediment is very mobile moving twice a day on every tide but numerous animals are adapted to live here. Clam shells and polychaete worms live beneath the sediment while fish, starfish, brittle stars and hermit crabs roam the surface looking for food.