Culture of the brown seaweed Sargassum siliquosum J. Agardh (Phaeophyceae, Ochrophyta): from hatchery to out-planting

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The brown seaweed Sargassum siliquosum is among the most common species with economic potential in the Philippines. However, reports on its culture are non-existent. This study describes the culture of S. siliquosum from land-based hatchery to out-planting in the open sea. Zygotes released from female receptacles can be recruited in large quantities unto artificial substrates and within 24 h produce multicellular embryos characterized by multiple bundles of rhizoids, and after 48–72 h elongated into germlings. After 2.5 months, germlings formed cauline leaves, and after 4 months, developed branches as seedlings. Recruits favored clay substrate than limestone and nylon in terms of density, growth, and longevity of seedlings. Desiccation treatment at different periods resulted to lower recruit density compared with control, had inferior growth and shorter longevity in all substrate types. For a period of 16 months, growth of S. siliquosum in the hatchery tanks was very slow, but became faster when out-planted in open sea using suspension culture method. Cultivars developed more branches after 4 months, at the same time producing receptacles. Maximum growth was achieved after 6 months, reaching a mean length of 42.8 ± 30.9 cm (max recorded was 1 m), some cultivars starting to show signs of senescence. In contrast, seedlings deployed using the bottom culture method survived for 3 months only without signs of further growth mainly due to epiphytism, siltation, and grazing. In conclusion, this study demonstrated the feasibility of farming S. siliquosum from hatchery-produced seedlings using suspension culture method to produce biomass for commercial use.