Application of Ferromanganese Slag of Different Sizes as Seaweed Bed Substratum

The purpose of this study is to investigate the formation of seaweed bed substrata using different sizes of Ferromanganese slag and Ferromanganese slag block in the sea area and by comparing them with the surrounding natural seaweed bed. We were unable to confirm any changes in pH or manganese concentration in seawater as a result of using FMS and FMSB. Small seaweed such as Hypnea grew five months after the material was set up. After 17 months, Sargassum horneri , Myagropsis myagroides , Undaria pinnatifida , and Ecklonia kurome grew on FMS, whereas S . horneri , Sargassum piluliferum , and Ecklonia kurome grew on FMSB. The vegetation transition progressed from undergrowth seaweed to large seaweed. About one year after the installation of the FMS and FMSB substrata, there was no significant difference in the number of seaweed species that grew on FMS and FMSB and the nearby natural seaweed bed. However, there was a small difference in the seaweed biomass between the FMS （ 30-75 mm ） and the surrounding natural seaweed bed. We found that when using smaller material, FMS （ 30-75 mm ） has higher seaweed biomass except in November 2017. By installing FMS and FMSB seaweed beds, we were able to confirm that the gathering fish are similar to those that gather around the nearby natural seaweed bed, but we were unable to confirm the relationship between seaweed biomass, material size, and fish density.