Abstract
Field surveys and indoor experiments were conducted in 2011 to clarify the dynamics of refractory nitrogen along the Osaka Bay and at the lower areas of the Yodo and Yamato rivers. In the process of dispersion of brackish waters from the inner areas to the mouth of Osaka Bay, most of the dissolved organic nitrogen (DON) changed to a refractory form. A small amount of nitrogen was available for primary producers in offshore areas of Osaka Bay since the percentage of non- or less-biodegradable DON to total nitrogen was high. These results demonstrate that emphasis should be placed on the establishment of environmental quality standards for water based on the nitrogen available for coastal organisms, along with the regulation of water quality by total nitrogen.
