Stock assessment of brown seaweeds (Phaeophyceae) along the Bitung-Bentena Coast, North Sulawesi Province, Indonesia for alginate product using satellite remote sensin

Indonesia needs at least 1,100 tons of alginate per year for various food and non-food industries with a value of about 420,000 US Dollars. These needs are met through imports from aboard. The raw materials for alginate, namely brown seaweed (Phaeophyceae) are very abundant in Indonesian coastal zones, but its stock level is not yet known. This study aims: to explore the biomass of brown seaweeds along the coastal areas of Bitung-Bentena, North Sulawesi Province by mapping their habitat, distribution and density using the effective and efficient tool of satellite remote sensing; and to compile preliminary results on the quality of alginate extracted from brown seaweeds. Result show that based on the isocluster analysis of Landsat-7 ETM+ and field sampling, we successfully classified 6 different habitats in the reef flats of Bitung-Bentena with map which had accuracy of 73.6%. The total area of brown seaweeds was approximately 127.1ha. Meanwhile, from 53 field transects, there were 6 species of brown seaweed with an average density for all species of 690.4 grams/m2. Thus, the biomass of brown seaweed was 2,133.5 tons wet weight, equal to 29.9 tons of alginate. This study proves that satellite remote sensing is an effective and efficient tool for such kind of works, and must be continued along the entire of Indonesian coastal zones. In this study, the preliminary results on extracting alginate from brown seaweed are also presented.