<；P>；PROBLEM TO BE SOLVED: To provide a method for reducing nutrient salt concentration in brine utilizing a marine alga, and a system as well as its apparatus. <；P>；SOLUTION: The method for reducing the nutrient salt concentration in the brine uses an immature unialgal culture strain which a marine alga sporophyte has grown up into or the alga body in which the immature unialgal culture strain has propagated introduced to its apparatus. The marine alga sporophyte originates from a specified large-sized red marine alga, for example, the Gracilaria species having the following properties: (1) a matured female gametophyte in nature is not found, (2) a matured form of only a tetrasporophyte is found, (3) it grows in an area of natural marine water mixed with fresh water. <；P>；COPYRIGHT: (C)2007,JPO&INPIT
