Abstract
Elucidation of the supply of substances from land to the sea is important to understand material (biomass) balances and the ecosystems in estuaries and the world's oceans. Especially in reservoirs and estuaries, masses of nutrients and organic matter change as a result of photosynthesis and flooding. This study recorded data for composition of nutrients and phytoplankton in a freshwater region and an estuary of the Kinokawa River to show their changes. Results show that the value of chlorophyll-a increased greatly in July before the Kinokawa floodgate was opened. At that time, it is presumed that dissolved organic nitrogen (DON) was taken in by organisms to form particle organic nitrogen (PON). Regarding the relation between chlorophyll-a and volatile suspended solids (VSS) during flooding, suspended solids (SS) contain much organic matter that originated from riverbed phytoplankton. Moreover, regarding the number and type of phytoplankton, we obtained results showing that diatoms were dominant in spring and summer. However, blue algae or green algae increased in summer. On 29 July, we found that dissolved silicate decreased concomitant with the increase of diatoms.
