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Habitats
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, and are probably an extension of the much more common offshore sands and gravels.
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.
Brief description of 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
UKBAP Priority Habitat
It occurs in Habitats Directive Annex 1 habitats: Sandbanks that are slightly covered by seawater all the time, and Estuaries
Further information sources
Priority habitat descriptions
(PDF 1.5Mb) (UKBAP)
Peacock worms (Helford VMCA)
Interesting fact
Empty seashells on the strandline give us a clue as to what lives beneath the muddy gravel.
