Development of an improved method of cultivation to obtain high biomass of the red alga Gelidiella acerosa (Gelidiales, Rhodophyta) in the open sea

This study describes a suspended stone (SS) method developed for in situ propagation of Gelidiella acerosa. The biomass yield potentials with various growth parameters were studied and compared to the floating raft method that was regarded as a superior method for Gelidiella propagation. The biomass of G. acerosa produced by the SS method consistently increased from the first to the fourth harvest (r = 0.940; P < 0.01) and ranged from 528 to 3645 g fresh wt m−2. For the raft method biomass increased from the first to the third harvest (977–1288 g fresh wt m−2) and then decreased in the fourth harvest (953 g fresh wt m−2). The DGR values of the SS method increased exponentially (r = 0.865; P < 0.05) from the first to the fourth harvest (1.33–2.62%) and these values significantly differed from those obtained from the raft method in the second to fourth harvest (P < 0.001) but did not significantly differ in the first harvest (P > 0.05). The biomass of an individual plant harvested from the SS method was significantly higher (P < 0.001) than those obtained for the raft method at all four harvests. The frequency distribution of weight of an individual plant in the SS method also constantly increased in successive harvests and 5% of the plantings in the fourth harvest attained a biomass of 200–250 g fresh wt. The in situ propagation of this species through the SS method described in this study could be a viable option for conservation and large-scale farming in the sea.