Mill Bay estuary and salt marsh

Less than 15 per cent of the Irish coast is comprised of sandy beaches, mud flats or salt marshes. However, these intertidal shores - which range from -semi-exposed to extremely sheltered and current-swept through to still water - incorporate a complex mosaic of habitats that are important for waders and wildfowl, while supporting myriad forms of sea life. Along the Mourne coast, for example, with its steep sea cliffs, stony shores and open rock pools, the greatest concentration of bird life is to be found in the sheltered conditions of enclosed bays and marine inlets, such as at Mill Bay on Carlingford Lough.

Here, within the fjord-like inlet of Carlingford Lough, extensive tidal mud, flats are rich in shellfish, invertebrates and marine plants that have adapted to the often rapid changes in salinity and temperature produced by the rise and fall of the tide. This interaction between saltwater and freshwater is fundamental to estuaries and gives rise to complex - and fascinating - biological patterns. The incoming sea and out-flowing rivers, for example, supply Mill Bay's intertidal flats with enormous amounts of mineral nutrients and edible organisms. These in turn provide the food for Large numbers of worms, mussels, cockles, crabs and tiny saltwater snails, as well as fish including sand eels, flounder and mullet. Together with the specialised plants which grow on the mud flats (such as eel grass), this food constitutes the diet of mast of the wildfowl and waders which winter in the bay. Large numbers of resident and migratory birds are seasonally present throughout Carlingford Lough, and curlew, Oystercatcher, lapwing and Redshank may be seen at any time of the year. The greatest numbers, however, occur in winter when Arctic-breeding Brent geese, widgeon, Greenshank, golden plover and Dunlin migrate south to join populations of other shorebirds. In the sheltered bays and inlets of the Lough, rich winter-feeding areas attract diving duck (Redbreast merganser, Goldeneye and - in particular -- nationally important Scaup) and dabbling species (Widgeon, Shelduck and mallard), as well as auks, grebes, divers, cormorants and shag.

Around the edges of Mill Bay, areas of low-lying mud fiats - known as the Bents -have been stabilised and converted to salt marsh by salt-tolerant vegetation. Here, plants such as marsh samphire, annual sea blite and sea manna grass withstand periodic immersion in tidal water and thrive in the fine sediment of the bay. In drier areas of the salt marsh, reached only by high tides and storm-spray, salt-tolerant grasses, sea purslane, sea lavender and plantains form additional foraging areas for waders and wildfowl. These grazing marshes are also used as roost sites where birds sleep and preen during periods of high tide, and are pasture for rabbits and livestock. The wrack beds of Mill Bay Bay

Besides its vast expanse of intertidal sands and mud's, Mill Bay is famous for its wrack beds -. or fucus farms - which formerly supplied seaweed for the arable fields of Mourne. The high tidal range and stony beaches along the Mourne coast have long favoured an unusual wealth of intertidal seaweed's, and their use as fertilisers since the l6th century illustrates man's exploitation of every available resource of land and sea. No longer worked today, the long strip-beds - which vary in colour depending on the age of the seaweed - may still be clearly sea at low tide.

Three species were mainly grown in MiII Bay. The zone nearest high tide marked the `knotted knob' or `whang wrack', also known as sea-whistle - a course, tough weed with large air bladders that gave it buoyancy. Next came the `bladder', `box' or `black wrack', and at low tide was found the most valuable weed: the `saw' or `lazy wrack', which is lighter in weight and grows more quickly. All species proved to be excellent fertilisers, containing the three principal components of farmyard manure: nitrogen, phosphate and potash, as well as various salts. In light soils, where it was mainly used, seaweed supplied organic matter which helps to hold moisture. Moreover, as weeds or animal pests were introduced with it, as is often the case with farmyard manure.

Although the processes of gathering, carrying and spreading huge amounts of seaweed absorbed much labour, these drawbacks were not sufficient to discourage the use of wrack until the advent of artificial fertilisers. In Ireland, the seasonal gathering of people during the wrack harvest (April ~ June) still persists on a small scale today. At its height, it was associated with the old rundale system of land use, and these gatherings tended to survive longest in areas where the communal sharing of the seashore and hill pastures was maintained. Nevertheless, rights of access to wrack beds were often disputed on congested foreshores. In a country where population pressure and land hunger during the l9th century was immense, the bitter rivalries and feuds which grew out of the rights of wrack appeared to be an inseparable part of this ancient coastal tradition.