アマモ生育に及ぼす葉上堆積浮泥の影響

概要

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The objective of this study is to investigate the shading effect of the deposition on leaves on the survival of eelgrass to clarify the factors responsible for the loss of eelgrass habitat in an eutrophic coastal zone with small disturbance by flow and waves in Hiroshima Bay. We investigated environmental conditions of a healthy eelgrass bed as a reference site and a site located outside of the bed with no vegetation. Also, we transplanted eelgrass into these sites and observed their survival.The transplanted eelgrass into the unvegetated site was difficult to survive, whereas those in the vegetated site could survive. The poor survival in the unvegetated site was due to the high levels of suspended solids deposited on the leaves of eelgrass. The higher deposit resulted in 64% decrease in the light intensity on leaves. The shading resulted in the decrease in the daily periods of irradiance-saturated photosynthesis required for eelgrass growth in the unvegetated site clown to 68-19% of that in the vegetated site.Contents of silt and accumulation of mud in the unvegetated site was higher than that in vegetated site. It is most probable, therefore, that effect of flow in the unvegetated site was lower and not enough to prevent the deposition in leaves.