広島湾のカキ養殖と海洋環境

概要

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The oyster culture has been prosperous in Hiroshima Bay but its product has gone down after 1990. We investigate the year-to-year variations in oyster culture and the lower trophic level ecosystem in August, when the marine environment in Hiroshima Bay becomes worst, from 1984 to 1996 using numerical ecosystem model. From the results of numerical experiments, when no oyster is cultured, the concentrations of chlorophyll-a, DOP (Dissolved Organic Phosphorus) and detritus increase in the upper layer, and the dissolved oxygen decreases in the lower layer of the northern part of Hiroshima Bay. This means that oyster culture plays an important role is preserving the marine environment of Hiroshima Bay. The product of oyster culture was highest when the concentration of chlorophyll-a in the upper layer was 7 $\mu$g l$^{-1}$ and the TP load from Ohta river was 0.5 ton day$^{-1}$. It is necessary to keep the TP load from Ohta river at 0.5 ton day$^{-1}$ for the successful oyster culture in Hiroshima Bay.
九州大学の論文