Dynamic of Particulate Organic Matter and Phytoplankton in Akkeshi-ko Estuary

This research was to clarify the dynamic of particulate organic matter (POM) and species composition of phytoplankton in an estuarine. C/N ratio was measured in a C-N Analyzer and phytoplankton was identifying under electron microscope. The seasonal fluctuation of POC and PON concentration was generally similar in all stations. POC and PON concentration were generally higher in inert part of estuary during spring and summer and its concentrations seem high at outside part during autumn. From total 128 species of diatoms identified in the Akkeshi-ko estuary, 103 and 102 species of phytoplankton occurred on the upper layer of sediments and in water column, respectively. On the upper layer sediments, there were 12 species of benthic diatoms and 2 species of pelagic diatoms were most common and dominantly occurred in all stations. In water column, 12 species of benthic diatoms and 3 species of pelagic diatoms were most common and predominantly occurred in all stations. The main reason of this condition is the concentration of POM and phytoplankton was increase during spring and summer cause of high input nutrient from outside of estuarine.