Abstract
We have studied environmental factors to limit the distribution of eelgrass (Zostera marina L.) by transplanting vegetative shoots of eelgrass at bare areas (0m, 1m and 2 m depth) in Zostera bed off Iwakuni airport. At 0 m control site in the Zostera bed, eelgrass shoot density decreased in a high wave season between spring and summer, showed different changes to the depth sites 1 m and 2 m. The annual mean irradiance at 2 m depth (near the deep edges of Zostera bed) was estimated to be ca. 3 E/m2/day, it was considered that the irradiance was a growth limiting factor of eelgrass. At 0 m transplanting site, all transplanted shoots disappeared because of disturbance by wave after the typhoon attack. But 1 m and 2 m transplanting sites showed almost the same changes in shoot density as control sites in spite of the typhoon. This suggests that lethal disturbance did not occurred at 1 m and 2 m trans-planting sites after the transplantation.And there was a difference in the shell appear-ance of the inside of sediments between the vegetated area and the bare area, although both physico-chemical characteristics at surface resembled each other. From these results, disturbance by wave, light intensity and physical characteristics of the sedi-ments were important as the environment factors to limit the distribution of Zostera beds.
