This habitat is no longer an MCZ Feature of Conservation Importance. Please refer to the MCZ FOCI Review 2016

Mud habitats in deep water

Mud habitats in deep water © JNCCMud habitats in deep water are fairly stable environments typically found below 20 meters where currents are slow and they are not affected by waves. This can be found offshore and in sheltered inshore environments such as sea lochs.  Most of the animals that live here burrow below the surface.  The animal communities vary according to the levels of silt, clay, sand and nutrients found in the mud.

Bristleworms can be present in high numbers, and their tubes sticking up through the surface of the mud can make the seabed appear as if covered in a kind of turf.  Cockles and other bivalves (with their paired, hinged shells) and burrowing sea urchins also bury themselves within the mud, while brittlestars live on the surface.

The Norway lobster and other burrowing crustaceans dig burrows in deep water muds, and can be found at depths of up to 800m.  Commercial fisheries target Norway lobsters, more commonly known as scampi or Dublin Bay prawns. 

Trawling for Norway lobsters and commercial fish is the greatest threat to deep water mud communities, as it causes serious disturbance of the seabed. Anchoring, offshore oil and gas operations, mining and major construction on land can also disturb mud habitats in deep water, and pose a threat to the communities of animals living there. 

The occurrence of large numbers of gallery worms in deep water mud seascapes is often an indicator of pollution or other disturbance.

For the official habitat definition please see the documents listed below.


European distribution

This is one of the most common and abundant habitats in the UK marine environment. It can occur in both offshore and sheltered inshore environments such as sea lochs. This habitat is also common in Europe and globally.


Conservation status/need

Mud habitats in deep water fact

This is a UK BAP Priority Habitat (BAP habitats are now Habitats of Principal Importance/Priority Habitats).


Official habitat definition

UK Biodiversity Action Plan; Priority Habitat Descriptions. BRIG (ed. Ant Maddock) 2008 (updated December 2011)


Further information

UK Biodiversity Action Plan - Mud habitats in deep water

JNCC biotope classification - Offshore circalittoral mud

JNCC - UK BAP Priority Species and Habitats

JNCC EUNIS habitat correlations table