Subtidal mud

Undersea beds of mud

Undersea beds of mud © JNCC

Muds and sandy muds occurring in areas too deep to be exposed to the tide are mainly found in extremely sheltered areas with very weak tidal currents, such as sea lochs and some estuaries and harbours.

High numbers of worms, cockles and other bivalve shells, urchins and sea cucumbers live in muddy sea beds and sea pens, burrowing anemones and brittlestars can also be found there.

Some larger animals like muddy areas too, and the Norway lobster (better known from menus as scampi, langoustine or Dublin Bay prawns) makes its home here. The size of the animals depends on the type of mud they are found on.  On the softest mud, there are fewer animals, but they grow relatively fast, and reach a large maximum size. On sandier mud, more lobsters crowd together but they grow more slowly, and are smaller.

In some muddy areas, perhaps as a result of pollution or of limited exchange of water with the open sea, not enough oxygen is transferred into the mud.  As a result, the seabed turns black just below the surface.  Most creatures find it impossible to survive in these conditions, and there if often little living there except bacteria.

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


European distribution

Widespread in sheltered seas around the British Isles and mainland Europe.

Undersea beds of mud fact


Official habitat definition

EUNIS habitat A5.3 Sublittoral mud


Further information

JNCC Marine Habitat Classification - Infralittoral Fine Mud

JNCC Marine Habitat Classification - Circalittoral Sandy Mud

JNCC EUNIS habitat correlations table