Artificial reefs for the development of valuable fishery resources wereplaced on sandy substrates at 8, 10 and 13 m depths in Muronohana,Ikata, Japan, and observed monthly or bimonthly from February 1999 to June2001.Enteromorpha intestinalis and Colpomeniasinuosa were the primary dominants in spring. The number of seaweedspecies at all the sites gradually increased in winter. Each reef reached aclimax stage of Sargassum spp., Eckloniakurome and Padina arborescens within 18 months.Overall, 38 seaweed species were found during the study.The settlement of kelp, such as E. kurome, was promoted byreduced sand cover as a result of turbulence. Large-scale surface roughnesscould be important in maintaining the communities after initial establishment.