Abstract
The study aims to clarify the effects of a new revetment irregularly placed stones on seaweed bed formation and gathering of marine organisms. We compared the seaweed bed and gathering of marine organisms at the new revetment off Iwakuni with those(beds on masonry revetment of the mainland side and beds on rock reef or masonry revetment of island side) at the Hiroshima Bay on the basis of environmental factors such as salinity, wave height. Environment factors of the new revetment were characterized by shallow water, low wave height (H1/3), low salinity, and high water temperature. These environmental factors were more similar to those of seaweed beds at the mainland side more than they were for the island side. Seaweed biomass (wet weight) and species number of the new revetment tend to be higher than that of the seaweed beds at the mainland side. However, the biomass and the species number are equal to the level of the intertidal seaweed beds of island side. Vertical seaweed distribution and community were slightly different from those of seaweeds of island side, but they were similar to those of seaweeds beds of the mainland side. Marine organisms found at the new revetment had many species in common with seaweed beds of the mainland and island sides. Averaged densities of the new revetment showed almost higher values than that for the seaweed beds of the mainland side. These results suggest that irregularly placed stones of size 0.5–1.0 m have a higher effect on seaweed bed formation and gathering of marine organisms compared with seaweed beds on the mainland side. The method of promoting seaweed bed formation and gathering of marine organisms by arranging stones is applicable in shallow water environments, similar to those found at the Iwakuni coast.
