Two free-living coralline algae occur sublittorally in Mannin Bay, Conneraara, Eire. Locally they form 30-cm high autochthonous banks which cover areas up to 1 sq km and have a diverse associated fauna. The algae are restricted by light to depths between 1 m and 16m. Within this depth range the development of the banks is controlled by wave-induced currents and the algae are broken down to form an algal gravel which supports a poor fauna. There is variation in growth form within Ihe species and a scheme is suggested for describing morphology in free-living corallines. Shapes vary from spheroidal, ellipsoidal, to discoidal. Within these shape classes branching density varies. Densely branched forms are found in the exposed areas and open-branched forms in the quiet areas of the bay. Wave-tank studies suggest that densely branched forms are most easily transported. Dense branching develops as a response to rolling on the substrate which damages the growing apex. Following abrasion, lateral branches form within the thallus. The palaeontological implications of the work are discussed and comparisons made with other algal bank deposits.
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|Published - May 1976