Effect of Human Activity on Oligotrophic Lake and its C onservation

北海道，这片得天独厚的土地上有许多贫营养的湖泊。这些湖泊的状况正在随着该地区的发展而改变。本报告旨在说明人类活动对北海道代表性的寡营养湖泊库塔拉湖和摩州湖的水体的影响。重点分析了湖泊营养盐的行为。此外，我们还根据数据提出了如何管理流入湖泊的水，以保持湖泊的自然状态。1999年，我们调查了湖泊水质和流入湖泊的河流的实际情况，并于2000年对库塔拉湖进行了更精确的水质研究。研究了贫营养湖泊营养盐和其他污染物的负荷产生机理，以及贫营养湖泊的流域管理。[结果]（1999）通过调查掌握了库塔拉湖和马舒湖的水质概况。通过以往的数据采集，可以明确库塔拉湖水质的变化趋势。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，并在年底时可以使用。（2000年）5月至10月，我们对库塔拉湖进行了7次研究，8月与环境部一起对马舒湖进行了一次研究。特别是在库塔拉湖，我们先后在8月份的雨季进行了研究。我们从9个层中采集了水样，最深处为146米。从研究中，我们看到硝酸盐氮最近略有增加，但透明度没有变化太多。由于流域内硝态氮浓度高于马驹湖，因此有必要对流域进行管理。从库塔拉湖的叶绿素范围，我们可以找到关于藻类（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).