SOME QUESTIONS ANSWERED
RICH Beach sand is nutrient-poor and most plants and animals are especially good at making the most of what exists or in some cases creating or fixing their own. Very coarse, pebbly beaches are the least rich in life. In contrast the silty sands found near the mouths of rivers and sea loughs, are rich in organic sediments and are home to associated fauna from worms and shellfish to fish and birds. Beaches like Magilligan Point and Portballintrae Bay are noted for their shell deposits. Check out a range of insects hopping over the surface in search of damp shaded surfaces like clumps of seaweed. Beachcomberâ€™s tip: Magilligan and Downhill are good for checking out lugworm casts (smooth piles of
spaghetti -like casts) and other marine life. Make your own shell collection (see back for ID). Take them home and paint on a little clear varnish to capture their true colours. Q. HOW ARE SAND DUNES FORMED? WINDBLOWN Beach dunes are simply piles of windblown sand which have been secured by a range of specialised plants. As beach sediments were being deposited on shore by the sea, prevailing winds blew the drying sands first into small parallel ridges and then gradually into a complex series of vegetated hills (dunes) and hollows (slacks).
EROSION The dunes and the beach are one and the same mass of sediment with a recognisable boundary between them in the form of a plant frontier (the limit of successful plant growth). At Mill Strand, Portrush and part of Curran Strand, Portrush the beach and dunes are separated by concrete promenades. This interrupts natural cycles of erosion and deposition and can lead to increased erosion and undermining. Sand is constantly on the move and dunes are prone to erosion and collapse. Equally, new dunes can form over a very short period of time (see Portstewart). The oldest sand dunes in Ireland have been recorded on the west bank of the Lower Bann estuary at Grangemore near Articlave.
Portstewart N.McD J.A.
Published on Jun 15, 2011