Sheltered muddy gravel habitats occur in estuaries, riads & sea loughs in areas protected from wave action and strong tidal streams. They contain diverse sediments from fine silt & mud to pebbles & cobbles.
- Site: Protection from wave action & strong tidal streams
- Main Species: polychaetes & bivalves
- Vegetation: fucoids, ephermeral green algae & red algae
- Sheltered muddy gravels typically consist of a complex mixture of sediments & as a result, in fully marine conditions on the lower shore, they can be extremely species-rich.
- Polychaetes & bivalve molluscs normally dominate, but representatives of most marine phyla can be present.
- The salinity can affect the species richness. For example, low salinity (mid to upper-estuarine) muddy gravels tend to be less species rich.
- Coarse gravel & stones at the sediment surface provide attachment sites for a variety of infauna & epiflora, such as fucoids, ephemeral green algae with associated littorinids (periwinkles) & filamentous red algae
Current Status in UK & Northern Ireland
- In Northern Ireland, sheltered muddy gravels occur in Carlingford Lough, Strangford Lough, Belfast Lough, Larne Lough & Lough Foyle.
- Muddy gravel was recorded within Larne Lough, by the NILS, on the upper shore with the catworm, Nephtys hombergii.
- Little is known about current factors which are affecting this habitat in NI. It is likely to be vulnerable to: physical disturbances (e.g. trampling), degradation of water quality by increased suspended sediment (can have smothering effect), organic pollution or heavy metals/hydrocarbon contaminants. Sheltered muddy gravels are also sensitive to changes in coastal processes, as a result of construction works (e.g. bridges, causeways, coastal defences), such as level of wave exposure or currents. Other threats include climate change, which may increase the level of desiccation in the intertidal area & prevent the settlement of fine organic & inorganic materials due to extreme events, which may result in higher wave energy. Potential collection of winkles (Littorina littorea) may have an impact on this habitat.