CULTIVATION TECHNOLOGY OF Sargassum duplicatum APPLYING OFF BOTTOM METHOD IN TOMINI BAY, GORONTALO PROVINCE, INDONESIA

Sargassum duplicatum is one of alginate producer seaweed which thallus is brown and generally flat. It has round thallus on the main stem and slightly flattened on branching, smooth and slippery surface, oval blades, serrated edge,and thick. Vesicle attached to the stem and blades, with a small size. It is relatively abundant in the tropical waters, so does in Indonesian waters. But in certain season its existance is hard to find, hence it is necessary to find some technology to cultivate this algal for its continuance. This study aimed to obtain a seaweed cultivation technology components by determining the optimal weight of seed, optimal space between clumps, and optimal space between the rope span to cultivate S. duplicatum.

A three stages study was conducted in April - October 2015 in the waters of Tomini Bay, Gorontalo Province, Indonesia. Cultivation of S. duplicatum applying off bottom method in a 25x10m construction, use a completely randomized design. To determine the optimal weight of seed, four kind of weight of seed (25 g, 50 g, 75 g, and 100 g) were tested in this study. The optimal space between clumps were reached by tested five space (15 cm, 20 cm, 30 cm, 40 cm, and 50 cm), and  the optimal space between  the rope span was determined by testing five space (20 cm, 40 cm, 60 cm, 80 cm, and 100 cm). The weighed seed were tied up into a rope then maintained for 45 days for each stage. Daily growth rate observed by weighing cultivated S. duplicatum two times per month. To support the cultivation, several aquatic environment parameters physicaly and chemically were measured once in a week. The results showed that the initial weight of seed, the space between clumps, and the space between the rope span significantly (P<0,05) affect the growth of cultivated S. duplicatum. Thus, cultivation technology components needed to support optimal growth of S. duplicatum by applying off bottom method are the initial weight of 100 g, space between clumps of 15 cm, and the space between rope span of 60 cm.