Effect of Human Activity on Oligotrophic Lake and its C onservation

北海道，这片大自然赐予的土地上有许多富营养化的湖泊。随着该地区的发展，这些湖泊的状况正在发生变化。这份报告旨在展示人类活动对库塔拉湖和马须湖水的影响，马须湖是北海道具有代表性的营养湖。重点分析了湖泊营养盐的行为。1999年，我们对库塔拉湖水质和入湖河流的实际情况进行了调查，2000年，我们对库塔拉湖进行了更精确的水质研究。[结果](1999)通过调查，掌握了库塔拉湖和马舒湖的总体水质状况。在收集了过去的数据后，我们可以清楚地了解库塔拉湖的水质趋势。由于我们在1999年购买的Chlorotec(水质监测仪)效果不佳，我们进行了一些改进，年底可以使用它。(2000)5-10月，我们与环境部对库塔拉湖进行了7次调研，8月对马舒湖进行了1次调研。特别是在库塔拉湖，我们先后在8月份的雨季进行了调查。我们从9个水层采集了水样，最深处146米。从研究中，我们看到硝酸盐氮最近略有增加，但透明度并没有太大变化。由于马树湖的硝态氮浓度高于马树湖，有必要对集水区进行管理。从库塔拉湖的叶绿素范围，我们可以发现关于藻类(浮游植物)运动的新概念。

Hokkaido, the land blessed with nature has many oligotrophic lakes. The state of such lakes is changing by development of the area. This report means to show how human activities effect on water of Lake Kuttara and Mashu, the representative ologotrophic lake of Hokakido. Especially we analyzed the behavior of nutrients of the lakes. Besides that, we proposed the way to manage water flow into the lakes to keep them natural depending on the data.In 1999, we investigated the actual conditions of lake water quality and rivers flowing into lake, and in 2000, we made more precise water quality research on lake Kuttara. And we also studied load-production mechanism of nutrients and other pollution matters and management of catchments area to keep oligotrophic lakes in desirable state.【Results】(1999)We grasped general water quality of Lake Kuttara and Lake Mashu by our survey.. After the collection of data in the past, we could make clear the trend of water quality of Lake Kuttara. As Chlorotec(water quality monitoring instrument), which we purchased in 1999, did not work well, we made some improvements and at the end of the year, we could make use of it.(2000)We researched on Lake Kuttara for 7times, from May to October, and on Lake Mashu, once in August with Ministry of Environment. Especially on Lake Kuttara, we made the research in rainy season in August successively. We took water samples from 9 layers, at the deepest, 146m. From the research, we saw nitrate-nitrogen increases a little recently but transparency did not change so much. As the concentration of nitrate nitrogen is more than in Lake Mashu, it is necessary to manage the catchments area. And from the chlorophyll range in Lake Kuttara, we could find the new concepts about the movement of algae(phytoplankton).