中海中浦水道における水質動向

Salinity, dissolved oxygen and water temperature were continuously measured in the Nakaura channel, the outlet of the Lake Nakaumi, from April 1, 1999 to April 4, 2000. The measurements are carried out near the surface (1 m deep) and near the bottom (11 m deep). As a result, the salinity showed large daily and seasonal variation near the surface, whereas it was comparatively steady near the bottom. Fast Fourier transformation analysis detected its periodic fluctuation with the cycle of 12.52 hours near the surface, and 12.36-and 25.52 hours near the bottom, suggesting influence by tide. The salinity near the bottom also showed 14- and 28 days cycle, corresponding to the lunar tidal changes. Near the bottom, the temperature and the dissolved oxygen also showed periodic pattern corresponding to the tide. In contrast, they showed clear daily cycle near the surface.