Effects of the seaweed bed construction using the mixture of steelmaking slag and dredged soil on the growth of seaweeds

Abstract

Supply of Fe ions is considered to be effective for the growth of kelp (a kind of seaweed). In the present research, a demonstration experiment in which seaweed beds/shoals were formed using a mixture of steelmaking slag and dredged soil was carried out in a marine area of Kawasaki City, Japan. The average strength of the mound for seaweed beds, which was made of a mixture of dredged soil and steelmaking slag, was 109.7 kN/m2. The shape of the mound was stable during the experiment period. The Fe content of the water above the mound made of the mixture was around 5 ppb higher than that above mounds made of natural sand. The average dry weight of the soft seaweed (Undariapinnatifida: wakame in Japanese) and brown seaweed (Sargassumhorneri) taken from mounds of the mixture including steelmaking slag were respectively 1.1 times and 2.1 times as much as that from mounds of natural sand. These results indicate that Fe ions, which dissolved from the steelmaking slag, have a positive effect on the growth of brown seaweed. © 2011 ISIJ.