Limnological properties of large lakes in eastern Asia under the influence of climate change

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The purpose of this research was to investigate the basic limnological properties of large in the eastern Asia region where the effect of climate change on the sustainable water use has been a matter of concern. We mainly focused on two large lakes, Lake Hovsgol, Mongolia and Lake Fuxian, China, although the data analysis was also conducted for Lake Baikal, Russia The results were compared with the data obtained in Lake Biwa, the largest lake in Japan. During the research period of two years, two research trips were carried out for both Lakes Hovsgol and Fuxian. Also, information exchange was facilitated by attending the workshop and by inviting foreign scientists to Japan. We succeeded in collecting useful data that may contribute to the development of effect management policy for these lakes. The major results are as follows.1. Chemical and biological parameters observed in Lake Hovsgol indicate that this lake isoligotrophic with relatively small perturbation by human activities. Low concentrations of dissolved organic carbon also suggest the impact of terrestrial organic carbon to the carbon cycle in the lake is relatively small.2. In Lake Fuxian, dissolved oxygen concentration was low near the bottom water at the site of the maximum depth (150 m) even in winter. This could be explained by the incomplete circulation because of the presence of weak themocline near the depth of 40 m. In fact, chemical and biological parameters clearly indicated the vertical patterns corresponding to the thermal stratification.3. The data analysis on microbial distribution in the deep water column of Lake Baikal revealed ocean-like patterns in the middle of the basin, although anomalous distribution was observed near the mouth of the major river inflow. This result suggests a large input of materials through the river inflow.