Multiple choice Which one of the following algae is an important source of mannitol? Chlorella Gelidium Laminaria Sargassum Reveal answer Fill a bubble to check yourself C Correct answer Explanation Laminaria (brown algae) is commercially important as a source of mannitol, a sugar alcohol used as a sweetener and in medicine. Chlorella is used for protein/supplements, Gelidium for agar, and Sargassum for alginate - not primarily for mannitol.