A Field Study on Salinity Circulation in Lake Ogawara

采用野外实验和数值模拟的方法，研究了青森县小川原湖的水流和盐度循环机制，以及它们对小川原湖主要渔业产品小川原蛤的生物学影响。1997年，通过野外实测，阐明了该湖盐度环流特征的流下盐度动态。本文还提出了一种新的测定粳稻生长速率的方法，作为粳稻生物学研究的第一步。1998年，通过野外试验研究了湖出水口高濑河的海水入侵与混合过程。对湖泊中日本Corbicula Japonica幼蛤的空间分布进行了调查。由于藻类是日本Corbicula Japonica的主要食物，因此通过野外测量和数值模拟研究了藻类的分布及其繁殖所需营养物质的运输途径。1999年，对湖管所收集的与盐度环流有关的水力资料，对缺失的部分进行恢复，对不准确的部分进行修正，并利用这些资料建立了海水入侵的概率模型，以估计海水入侵和湖泊盐度状况的随机特征。通过详细的野外测量，还澄清了强风和密度效应引起的湖泊内部振荡和垂直混合。从水力学的角度，通过野外实测和数值模拟，研究了日本Corbicula Japonica在湖口附近浅水区产卵条件的发展。结合1998年的研究结果，从水力学的角度对湖中的日本Corbicula Japonica的生物学特性进行了探讨。

The currents and salinity circulation mechanism of Lake Ogawara, a large brackish water lake in Aomori prefecture, is investigated by field experiments and numerical simulations as well as their effects on the biology of Corbicula Japonica that is a species of Clams and the major and important product of fishery in the lake.In 1997, the dynamics of salinity under flow, which is a characteristic of the salinity circulation of this lake, was clarified by field measurements. A new techniques for measurements of growth rate of Corbicula Japonica was also developed as the first step of the study on its biology. In 1998, the seawater intrusion and mixing process in Takase River, the outflow from the lake, was studied by field experiments. In the lake, the spatial distribution of infant clams of Corbicula Japonica was surveyed. The algae distribution and the transportation routes of nutrients for its propagation were also investigated by field measurements and numerical simulations because algae is a major food for Corbicula Japonica. In 1999, hydraulic data concerned with the salinity circulation, which have been collected by lake management office, were restored for missed parts and modified for inaccurate parts, and then a probabilistic model of seawater intrusion was constructed by using the data so as to estimate the stochastic feature of the seawater intrusion and the salinity condition of the lake. Internal oscillations and vertical mixings in the lake caused by strong winds and density effects were also clarified by detailed field measurements. As for Corbicula Japonica, the development of their spawning condition at shallow area near the lake exit was investigated from the standpoint of hydraulics by field measurements and numerical simulations. With the results obtained in 1998, a view about biology of Corbicula Japonica in the lake was obtained from the hydraulic standpoint.