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Roles of the inflowed coastal Oyashio Water to Funka Bay on the spring bloom as a trigger of its occurrence.

流入芬卡湾的沿海亲潮水对春季水华的作用是其发生的触发因素。

基本信息

批准号：
08458139
负责人：
MIYAKE Hideo
金额：
$ 2.69万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Hydrographic conditions and low trophic productivities were investigated with using mooring systems, satellite image analysis and ship observations during the spring bloom in 1997. Results are summarized as follows ;1) Chlorophyll-a concentrations and fluxes of settling organic particles in the sediment trap were poor in middle March. It is concluded that the phytoplankton bloom was weak in spring of 1997. Coastal Oyashio Water flowed weakly into the bay. This is a reason why the spring bloom was weak in 1997.2) Ocean color satellite and ship observations showed high chlorophyll-a areas off Muroran to the center of the bay mouth. Waters of the high chlorophyll-a areas moved into the bay. This suggests that the wind-driven currents are important for the distributions and movements of the plankton.3) Resuspention perticles from the bottom sediments were trapped under the southeasterly winds. This is explained as follows ; high wind waves and resuspentions of the shallow sediments inside the bay cause by the southeasterly winds which have a long fetch. These particles move with the southeastward flows drived from the vortex pair and fall into the trap at the center of the bay.4) Copepod nauplii are main organisms in early life stage of walleye pollock. After the inflow of the coastal Oyashio Water, large copepod nauplii become to be abundant near the bay. When spawning areas shifted the northeast ward, Oyashio Water was favor food conditions for the larvae, and it transported efficiently eggs and larvae into the bay. This is one of reasons for the long term variabilities of the year class strength of walleye pollock.

利用系泊系统、卫星图像分析和船舶观测，对1997年春季水华期间的水文条件和低营养生产力进行了调查。结果表明：1）3月中旬，沉积物收集器中叶绿素a浓度和沉降有机颗粒通量均较低。结果表明，1997年春季浮游植物水华较弱。沿海的Oyashio水流入海湾微弱。2）海洋水色卫星和船舶观测结果显示，室兰近海至湾口中心叶绿素a含量较高。高叶绿素a区的沃茨向海湾内迁移。这表明，风驱动的电流是重要的分布和移动的浮游生物。3）来自底部沉积物的再悬浮悬浮物被困在东南风。这是解释如下：高风浪和海湾内的浅沉积物的再悬浮造成的东南风，有一个长的取风。这些颗粒随涡对驱动的东南向流运动，落入湾中心的捕集器中。4）桡足类无节幼体是狭鳕早期生活阶段的主要生物。在沿岸的亲潮水流入后，大型桡足类无节幼体在海湾附近变得丰富。当产卵区向东北方向移动时，亲潮海水有利于仔鱼的摄食，并能有效地将卵和仔鱼输送到海湾。这是狭鳕年级强度长期变化的原因之一。