Flame Shell Beds: A Protected Keystone Biogenic Bivalve Habitat

Flame shells, a keystone bivalve species, live on the seabed in nests constructed from shells, stones and other materials bound together by byssus threads. Large aggregations of nests can combine to form a dense biogenic reef called a flame shell bed. Flame shell beds are rich in benthic species. While individual flame shells have been found down to depths of around 100m, beds usually occur between depths of 5–25m in areas with moderate or strong water currents. Flame shells have a widespread distribution individually however flame shell beds have a much narrower distribution and are predominately found in Scottish waters. In Scotland, flame shell beds are mostly found on the west coast, commonly associated with mixed muddy sediments, coarse sands, and gravel. Extensive beds, such as the Loch Carron bed which covers an estimated 194ha, are rare. Flame shell beds are classed as Priority Marine Features (PMFs) in Scottish waters and are protected by a suite of Marine Protected Areas (MPAs). Despite their protected status, they remain threatened and in severe decline. The habitat flame shell beds provide is sensitive and slow to recover from physical damage, being particularly vulnerable to mechanical disturbance from towed bottom-contact fishing, which is thought to be one of the major drivers behind their historic decline. They are also sensitive to siltation and changes in water quality. Protecting and conserving this biogenic habitat is essential, as any loss or degradation to the flame shell bed may result in sediment destabilisation and loss or degradation of associated communities.