Field Surveys on the Characteristic of Changes in Concentrations of Organic Substance and Nutrient Salt at the Tidal Area of the Mouth of the Yamato River

Changes in concentrations of organic substances of the sediment and nutrient salts in the pore water of the riverbed were examined at a tidal area of the mouth of the eutrophic Yamato River in 2009-2010. TOC and TN contents of the sediment, together with NH4-N and NO2+NO3-N concentrations in the pore water drastically changed depending on time, month and station. Production rate of NH4-N in the pore water of the Yamato River was ca.10-100 times higher than that of laboratory experiments. These results suggest the importance of tidal change and wave in evaluating dynamics of organic substances and nutrients at the tidal area of the mouth of a river.