PIP/PP ratio as an indicator of phytoplankton activities and origin of particulate matter in Harima-Nada, the Seto Inland Sea, Japan

Abstract

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.