Sub - Tidal Habitats

Sub-tidal mud sediments:

Occur mainly in sheltered areas of sea loughs. Locally associated with this sub-tidal mud (.PDF 62Kb) are extensive mussel beds e.g. Lough Foyle (which is also notable for the presence of native oyster beds ). In Strangford Lough, extensive horse mussel beds (.PDF 63.9Kb) occur; these are colonised by the bivalve and a highly diverse association of other species. Other communities occurring in fine mud in deeper water in Strangford Lough are dominated by the Dublin Bay prawn . This species forms the basis of an important fishery in the Irish Sea all along the Coounty Down coast and beyond. In Carlingford Lough, a community dominated by the sea pen and the opistobranch mollusc, is abundant on fine very stable mud.
 

Sub-tidal sand:

Is a habitat generally found adjacent to intertidal sand in Lough Foyle, along Magilligan and the Causeway Coast (where much more extensive areas of relatively barren sand occur further offshore) and Dundrum Bay. Typical species include the sand eel, the burrowing brittle star, the lugworm, and the sea potato.
 

Sub-tidal gravel and cobbles:

Are often typified by extensive beds of the brittle star, Ophiothrix fragilis. These are mainly found in Strangford Lough and the Ards Peninsula, Lecale and the Mourne Coast. In some areas, such as at the mouth of Belfast Lough, the brittle star, Ophiocomina nigra, is abundant in muddy gravel (.PDF 71.22Kb). In areas of coarse, clean, shelly gravel the burrowing sea cucumber, is often a characteristic species.
 

Maerl beds:

Maerl beds (.PDF 30.74Kb) consisiting of a free-living calcareous algae occur at Garron Point and Ballygalley Head on the North-east Coast.
 

Rocky sub-tidal habitats:

Include both bedrock and boulders. Algal communities dominate the shallow or infralittoral rock habitats. These algal communities are mostly dominated by one or more species of kelp.Where rocky habitats (.PDF 62.9Kb) occur at greater depth and where tidal currents are stronger, animal groups such as bryozoans, hydroids and sponges dominate.

Kelp beds:

Are best developed around Rathlin Island where the kelp Laminaria hyperborea is dominant to a depth of 20-30 m and the beds are very species-rich. In contrast, kelp beds in the more turbid waters of the Mourne Coast extend only to 5m and are species poor. Laminaria saccharina is the dominant kelp in the sea loughs where beds extend to a depth of less than 10m.
Below the depth of algal growth, sponges, anemones, bryozoans and hydroids assume a greater importance. A particularly diverse range of communities and species is associated with the basalt and limestone terraced bedrock and caves and fissures on the north coast of Rathlin Island. These include northern populations of the sea cucumber, Holothuria forskali, and the cave inhabiting sponges, Sryphnus ponderosus and Derictus bucklandi.

Tidal rapids:

Found in the narrows at the entrance to Strangford Lough also have an important assemblage of species. Sand scoured rocks are the habitats (.PDF 28.64Kb) for a characteristic range of sponges, hydroids and bryozoan species. One associated habitat is formed by the polychaete worm, restricted to the seabed of Magilligan in Northern Ireland.
 

Saline lagoons:

Are mainly associated with sea loughs in Northern Ireland and are mostly man-made. Dominant plant species include tassel weeds and fennel-leaved pondweed . Several species of invertebrates are mainly found in this habitat (.PDF 27.06Kb) including water beetles, corixids and molluscs.