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

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。主要研究结果如下：1)3月中旬，沉积物捕集器中的叶绿素a浓度和沉降有机颗粒通量较差。结果表明，1997年春季浮游植物水华较弱。沿海的Oyashio水微弱地流入海湾。这就是为什么在1997.2)春季水华很弱的一个原因。海洋颜色卫星和船舶观测显示，从穆罗兰到海湾入海口中心附近地区的叶绿素含量很高。水体中的高叶绿素a区移入海湾。这表明风生洋流对浮游生物的分布和运动具有重要意义。3)东南风作用下，底层沉积物中的悬浮颗粒被困住。对此的解释如下：大风、巨浪和海湾内浅层沉积物的再悬浮是由东南风造成的，东南风影响很大。这些颗粒随着涡对向东南方向的流动而移动，落入海湾中心的陷阱中。4)桡足类无节幼体动物是大口鳕鱼早期生活阶段的主要生物。在沿海Oyashio水流入后，海湾附近的大型桡足类无节幼体变得丰富起来。当产卵区向东北方向转移时，Oyashio水有利于仔鱼的摄食条件，并能有效地将卵和仔鱼输送到海湾。这是大眼鳕鱼年级强度长期变化的原因之一。

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.