Sheltered muddy gravels
Muddy gravels occur mainly in estuaries,
drowned river valleys and sea lochs, in areas protected from wave
action and strong tidal streams. They can be found both on
the shore and in the shallows.
Which plants and animals occupy the gravels
depends on the composition of the seabed and the influence of
freshwater. Where the seawater is undiluted, muddy gravel seascapes
tend to be dominated by worms, such as delicate peacock worms, with
their fan of feathery tentacles, which is used for trapping food
from the passing seawater. Burrowing anemones are found in
muddy gravels, as are burrowing
bivalves (with their paired, hinged shells), including
ridged carpet shells and blunt gapers. Coarse gravel and stones on
surface of the muddy gravel provide a hard substrate for seaweeds
to attach to.
Fewer species are found in the gravels when
there is a noticeable input of freshwater to the area. Worms
continue to dominate here, but cockles and oysters may also be
found.
For the official habitat definition please see
the documents listed below.
European distribution
Fully marine sheltered muddy gravel
communities are scarce in Britain. They are, however, found
extensively in the Solent and the Helford River in Cornwall, as
well as other estuaries in south-west Britain, for example the Fal
Estuary, Salcombe Harbour and Milford Haven.
Conservation status/need
Official definition
UK Biodiversity Action Plan; Priority Habitat Descriptions. BRIG
(ed. Ant Maddock) 2008 (updated December 2011)
Further information
JNCC - UK BAP Priority
Species and Habitats
Helford
VMCA - Peacock's worm
JNCC EUNIS habitat correlations table