STUDY ON THE FORMATION OF LARGE SCALE ANOXIDATION AND OUTSIDE WATER INTRUSION IN URANOUCHI BAY

天王星湾夏季在底层和次表层形成了强缺氧水团。大量养殖的黄尾鱼被杀。(1) 6 ~ 9月，随着背斜的发展，底部缺氧水逐渐增多，入侵后缺氧水消失一段时间。入侵使底层营养水上涌，使上层水质恶化。(2)随着缺氧水的发展，底部表面产生的硫化氢（H2S）通过垂直混合被输送到上层，立即被氧化。8月份，H2S的氧化使底层溶解氧（DO）浓度降低了2.4ppm，进一步促进了氧化。(3)随着底层缺氧水体的发展，龙内湾中部中层开始生长长崎赤潮浮游生物。当外界咸水侵入时，全层立即发生异常增殖，表层形成赤潮。(4)地下氧化在1988年9月初、1993年8、9月中旬和11月初形成。它们是在白昼时间突然缩短之后形成的。在氧化初期，鞭毛藻赤潮和外来水入侵出现。(5)鞭毛藻白天出现在表层，夜间迁移至8 ~ 15m深度，并在浅层和中层大量消耗DO。(6)浅层DO浓度受浮游植物生产和水体消耗的控制。混合和侵入造成的DO供应可以忽略不计。当日照时间减少时，由于地下层DO的产生减少而在地下层形成氧化，并且由于鞭毛藻的迁移而增加了DO的消耗。

In Uranouchi Bay, strong anoxic water mass was formed in the bottom and subsurface layrs in summer. A large number of cultured yellowtail fish were killed.(1)Anoxic water in the bottom grew with the development of pycnocline from June to September, and disappeared for a while after intrusion. Intrusion upwelled the bottom nutrient water, and made worse the upper water quality.(2)Hydrogen sulfide (H2S), which was produced at the bottom surface with the development of anoxic water, was transported to the upper layr through vertical mixing, and immediately oxidized. Oxidation of H2S reduced the dissolved oxygen (DO) concentration in the bottom layr by 2.4ppm during August, and further promoted the anoxidation.(3)Gymnodinium nagasakiense red tide plankton began to grow at the middle layr in the center of Uranouchi Bay with the development of anoxic water in the bottom. When external saline water intruded, abnormal multiplication immediately occurred in the whole layrs, red tide was formed at the surface.(4)Anoxidation in the subsurface was formed at the beginning of September, 1988, the middle of August and September, and the beginning of November, 1993. These were formed from just after the sudden decrease of daylight hours. At the beginning of anoxidation, red tides of dinoflagellates and outside water intrusion were developed.(5)Dinoflagellates were appeared in the surface in the daytime, but migrate into the depth of 8-15m in the nighttime, and consumed abundant DO in the subsurface and middle layrs.(6)DO concentration in the subsurface layr was controlled by the production due to phytoplankton and consumption in water. DO supply due to mixing and intrusion was negligible. When the daylight hours decreased, anoxidation were formed in the subsurface, because DO production in the subsurface layr decreased, and DO consumption were increased due to the migration of dinoflagellates.