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

乌拉努奇湾夏季在底层和次表层形成强缺氧水团。(1)6~9月，底层缺氧水随着跃层的发育而增加，入侵后一度消失。入侵抬升了底层营养水，使上层水质恶化。(2)随着缺氧水的发育，底层产生的硫化氢(H_2S)通过垂直混合输送到上层，并立即被氧化。8月份H_2S氧化使底层溶解氧(DO)浓度降低2.4ppm，进一步促进了氧化作用。(3)随着底层缺氧水的发育，乌拉努奇湾中部的长崎裸藻赤潮浮游生物开始在中间层生长。当外咸水入侵时，整个表层立即发生异常增殖，表层形成赤潮。(4)亚表层氧化作用形成于1988年9月初、8月中旬和9月中旬、1993年11月初。这些都是在日光时间突然减少之后形成的。(5)甲藻白天出现在表层，夜间迁移到8-15m深处，并在次表层和中层大量消耗DO。(6)次表层DO浓度受浮游植物产生量和水体消耗的控制。由于混合和入侵造成的DO供应可以忽略不计。随着日照时数的减少，次表层产生的DO减少，甲藻的迁移增加了DO的消耗，从而在次表层形成了抗氧化作用。

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.