Abstract
It is known empirically that coastal structures such as breakwaters serve as foundations of seaweed beds. In recent years, various field experiments which aim to increase the ability as seaweed beds have been conducted so that the structures may harmonize and coexist with the surrounding environment. In this study, comparative experiments were conducted in Kutsugata Port and Oniwaki Port on Rishiri Island using ordinary concrete blocks and such blocks whose surfaces had been treated with ferrous sulfate, in order to determine differences in the ability to enable seaweed to take root. A roughly equal ability was determined for the two types of block when measured two years after installation.
