Abstract
In Laminaria japonica cultivated at Date Bay, Hokkaido, we investigated the monthly varlation in alginate content and its M/G ratio together with the variatlon in mannitol and some minerals such as calcium, magnesium, iron, and phosphorous. The following result was obtained. The relative content of the MG block of alginate varied only slightly from March to October in an almost similar pattern to the total alginate content. In contrast, the content of the M block increased wlth the growth of kelp toward summer, while that of the G block showed an inverse pattern. The global pattern of variation in the content of mannitol resembled that of the M block; it increased conspicuously in summer, but decreased gradually toward the end of autumn.
The contents of inorganic elements varied with characteristic patterns. except for calcium which seemed to increase in concert with the increase of the M block toward autumn.
