estimation of nutrient budget using underwater nutrient analyzer system

为了定量半封闭海湾的营养盐收支，我们开发了水下营养盐分析仪系统。在日本东京湾的台场，使用新开发的传感器与电流和水质传感器进行现场观察。结果，我们成功地观察到硝酸盐和氨的变化，每小时的间隔在半年内。这些营养盐的变化显着的潮汐高程，河流流量和浮游植物浓度的变化。这些结果也揭示了观测区水质变化的重要特征。例如，浮游植物一般在平静天气条件下增加，而在降水事件期间减少。如果降水量超过约50 mm/天，这种现象将持续约2周。然而，如果降水量很小（约。5 mm/d），浮游植物从河流进入后急剧增加。这些结果将有助于改善东京湾的水质环境。

To quantify the nutrient budget in semi-enclosed bay, we developed underwater nutrient analyzer systems. Field observation was carried out using newly developed sensor with current and water quality sensors at Odaiba in Tokyo Bay, Japan. As a result, we successfully observed variation of nitrate and ammonia with per hour interval within half year. These nutrients significantly varied with changes in tidal elevation, river discharge and phytoplankton concentration. These results also showed the important characteristics of water quality variation in the observation area. For example, phytoplankton generally increased under calm weather condition and decreased during precipitation event. This kind of phenomena continued for about 2 weeks if precipitation exceeded about 50 mm/day. However, if precipitation was small (ca. 5 mm/day), phytoplankton sharply increased since it originated from river. These results will contribute in the improvement of the water quality environment in Tokyo Bay.