Dissolved organic matter was measured by using Fluorescence Spectroscopy (FS) along with salinity from snowmelt season to summer at a tidal flat in Lake Komuke at the northeast of Hokkaido. Seasonalities of dissolved nitrogen and phosphorus concentrations were also examined to clarify the dynamics of nitrogen and phosphorus in sediment-water interfaces. Salinity decreases during the snowmelt season, and FS revealed that fulvic acid-like and humic acid-like fluorescence intensities were higher in sediment pore water than in surface water especially in tidepool due to accumulation of organic matter production. It is likely that NH4-N and PO4-P concentrations in surface sediment were mainly affected by redox condition change triggered by tidal action and infiltration flow in shore side.
