Verification of Recovery Technique of Seaweed Bed in Breakwater Structure that has Rear Steps

Abstract

Barren ground is widely distributed in the sea area. The coastal structures to make the algae place have been constructed for about ten years. However, it is feared that the decrease in the effect of seaweed creation by the aged deterioration of the substrate and water temperature elevation in recent years. Field investigation concerning distribution of seaweed beds and physical environment were performed in fishing port of Hokkaido. In this study, the results of the field investigation are introduced. It is found that one of the causes is feeding pressure to seaweed by sea urchin. It is strongly dependent on water temperature in winter. To control the feeding pressure in the situation of the elevated water temperature, it is necessary to improve flow velocity by raising the rear steps.