Distribution of settled Sargassum propagules related to wave motion.

Abstract

We investigated the distribution of settled Sargassum propagules by using artificial sub strata and measured water motion around a Sargassum forest in Gokasyo Bay, Mie Prefecture, Japan. The majority of measured propagules was Sargassum homeri (Turner) C. Agardh and the number of propagules settled on the artificial substrata ranged from 0 to 2197 individuals/ 50cm2. Numbers of propagule settled on the artificial substrata in near shore region were low, while numbers were high around an offshore Sargassum forest.These results indicate that wave motion effected the settlement of propagules to the arti ficial substrata in the following manners.In a near shore Sargassum forest where wave ray concentrates, the propagules that fell onto the substrata were carried out by wave motion. And in a near shore small bay where wave ray disperses and sea bottom is muddy, settlement of silt on the substrata inhibited the settlement of propagules. On the other hand, in offshore regions where wave motion has little effect on the settlement of propagules, distribution of propagules reflected the dispersion from offshore mother plants.