Maerl is a name for a group of red seaweeds (Lithothamnion corallioides, Lithothamnion glaciale and Phymatolithon calcareum) that deposit calcite in their cell wall. When sections break off these seaweeds the bits form (in certain locations) coral beaches. There are two known coral beaches in Connemara at Ballyconneely and one at Carraroe. These gravel beaches a rare and of great conservation importance. The Coral Strand and Tran an Doilin are unusual beaches formed from the dead fragments of "maerl", a twig-like calcareous seaweed (Lithothamnion spp.). This seaweed, which is pinkish- purple when alive, changes to a bright golden-yellow once it dies. This type of beach material is washed up at only a few locations in Ireland - including Tran an Doilin, Carraroe and the Coral Strand Ballyconneely. Maerl beds are found up to 30 m down in Irish waters and can be up to 10 m thick. Radio carbon dating has found the lowest layers to be over 5000 years old. Maerl beds are slow to regenerate (1 mm per year). Beds of Maerl are ecologically important. They are a nursery for the juvenile stages of commercial species such as cod, Pollack and scallops. Maerl beds are easily damaged by dredging and towed fishing gear. It is illegal in Ireland to remove maerl from beaches. This substance was extensively dredged as a source of lime for gardens and organic farms. This is because it contains high concentrations of calcium and magnesium. ( 32.1% CaCO3 and 3.1% MgCO3 ).
