SEAWEED BED RECLAMATION EXPERIMENT USING VERTICAL SEAWALL AT INNER PART OF OSAKA BAY

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More than 95% of the coastline of Osaka Bay that enclosed sea area, is surrounded with artificial structures by land reclamation. Decreasing the transparency of sea water by eutrophication, the seaweed bed has almost completely disappeared. In this study, we tried to reconstruct a seaweed ecosystem for the environmental restoration in the innermost part of Osaka Bay. We set up some terraces on the side of vertical seawall; the Brown seaweed, Undaria pinnatifida grew there.As a result, U pinnatifida grew up on all terraces and the small fauna living symbiotically with seaweed was increased. Among them, the Gammaridean amphipods, Grammaridea and the ghost shrimps, Caprellidea were the dominant. Phytal animal biomass tended to increase as standing crop of U pinnatifida was increased. This experiment showed that seaweed bed ecosystem was able to be regenerated on the terraces of a vertical seawall in the enclosed sea area where the light penetration was limited.