Offshore deep-sea muds are fairly stable environments. At depth they are not affected by waves. They occur at depths of 200-500m, in areas where the currents are slow.
No plants can grow at this depth, and 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 also digs burrows in deep water muds, and can be found at depths of up to 800m. Commercial fisheries target Norway lobsters, which, as scampi or Dublin Bay prawns, are familiar food.
Trawling for Norway lobsters and deep-sea 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, deep-sea mining and major construction on land can also disturb offshore deep-sea muds, 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.
This is one of the most common and abundant deep-sea habitats in the UK offshore marine environment, in Europe and globally.
UKBAP Priority Habitat
Listed in Annex I Habitats Directive: Large shallow inlets and bays
Habitat Action Plan (UKBAP)
Offshore circalittoral mud (JNCC)
Potting, instead of trawling, in sheltered areas of deep water with mud is the most ecologically sustainable, least-damaging method of harvesting Norway lobster and other crustaceans.