Chemical and elemental components of surface particulate matters were investigated during 4 seasons all over the Harima-Nada, the eastern part of the Seto Inland Sea, Japan. We measured concentration of particulate organic carbon （POC）, particulate organic nitrogen （PON）, and chlorophylla （Chl.a）. We also determined the particulate phosphorus （PP） divided into organic （POP） and inorganic （PIP） fractions. In this paper, the seasonal variations of the C/Chl.a, C/N and PIP/PP ratios of particulate matter were discussed. In summer, Chl.a was high, and Chl.a and PIP/PP ratios indicated phytoplankton activities were also high. Our dataset also indicated that surface particulate matter contained a large amount of non-phytoplankton particle in the coastal water, even when phytoplankton biomass was high in summer. We found that the PIP/PP ratio was a good indicator to predict the phytoplankton activity and the origin of particulate matter of surface seawater as well as the C/Chl.a and C/N ratio.

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To clarify the current status of ballast water and aquatic organisms in the water transferred from and to Japan, available information on the transferred volume of the ballast water and the migration of aquatic organisms in Japan was reviewed and summarized. It was made clear that Japanese export of ballast water is approximately 30 folds of its import, showing that Japan is an export surplus country of ballast water. Among various organisms migrating with the ballast water, molluscs and crustaceans were found to be the most substantial. We stress the importance of repeating this kind of revewing research after the implementation of the Ballast Water Convention （International Convention for the control and management of Ship's Ballast Water and Sediments）, and can evaluate the effect of the treaty.

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