VEGETATIVE REPRODUCTION IN POSIDONIA-OCEANICA - SURVIVAL AND DEVELOPMENT OF TRANSPLANTED CUTTINGS ACCORDING TO DIFFERENT SPACINGS, ARRANGEMENTS AND SUBSTRATES

In a set of balanced, experimental growth trials, cuttings of Posidoni a oceanica, a Mediterranean seagrass, were transplanted on three types of substrate: dead matte, sand clear of vegetation and fine sand bear ing Cymodocea nodosa. The following arrangements and spacings were als o tested: lines of transplants 5, 10, 15 and 20 cm apart; circles of 3 , 6 and 12 transplants, with both leaves oriented inwards and leaves o utwards; arrangement in staggered rows (quincunx); and arrangement hea d-to-foot. All sets of trials were carried out on both orthotropic and plagiotropic cuttings. Survival and development was followed approxim ately every 3 months for 3 years. The best survival and development we re obtained for cuttings transplanted close together, with survival ra tes after 3 years of 84% or more in plagiotropic cuttings planted on m atte, 5 and 10 cm apart. On fine sand with C. nodosa, 85% survival was obtained with 5-cm spacing and all the surviving transplants bore new ramifications after 3 years. On clear sand, high mortality was caused by bioturbation produced by the burrowing prawn Callianassa tyrrhena. Arrangement in circles gave no better results than in lines.