Peat and clay exposures


Seabeds formed of exposed peat or clay, or in some cases both, are uncommon.  Where they do occur, they have been found between the tides as well as fully underwater.  They can be buried by sand or other sediments and then exposed again on a regular basis.

On the shore, the peat/clay exposures are characterised by the presence of piddocks – elongated burrowing bivalves with paired, hinged shells.  The surface of the peat or clay may be covered by mats of seaweed, such as sea lettuce.  Empty piddock burrows provide homes for small crabs and anemones, while shore and edible crabs may be found in larger crevices.

On soft clay, a few red seaweeds will attach to loose-lying pebbles or shells, while worms, such as the ragworm, sometimes hunt within it.

Subsequently less is known about the peat and clay exposures that are found below the low water mark, and no-one is sure of the maximum depth at which they can be found.  Little is known about the plants and animals that live in these habitats but they are likely to be different to those found on the shore.

These unique and fragile habitats are irreplaceable, as they were formed millions of years ago from ancient lakebeds and forested peatland.  They are threatened by coastal infrastructure development, cable laying, dredging and other activities that disturb the seabed, mussel fisheries and the collection of the piddocks for bait.

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


European distribution

Peat and clay exposures are found along the north and south coasts of Wales, and the south and east coasts of England. Clay exposures with piddocks are also found in Cumbria. Little is known about UK distribution of subtidal peat and clay exposures in deeper water, but they are likely to occur near to those on the shore.


Conservation status/need

Peat and clay exposures fact


Official definition

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


Further information

JNCC - UK BAP and priority species and habitats

Marine Life Information Network - Ceramium sp. and piddocks on eulittoral fossilized peat

European Environment Agency - [Ceramium] sp. and piddocks on eulittoral fossilised peat

JNCC - UK BAP Priority Species and Habitats

UK Biodiversity Action Plan; Priority Habitat Descriptions. BRIG (ed. Ant Maddock) 2008 (updated July 2010)

JNCC EUNIS habitat correlations table