近年の諏訪湖における生物群集の動態研究の意義

Abstract

Studies of the organic community in Lake Suwa have been performed since 1907. During the long history of such studies, lake eutrophication reached serious levels in 1960s and 1970s, and eutrophication problems occurred. These studies have, therefore, reflected the changes in the community associated with lake eutrophication. In order to solve the resultant problems, a sewerage system was built in the lake catchment area in 1979, and the residential area covered by the system has increased since that time. Nevertheless, the lake water quality had not been markedly restored for about the last 20 years. Around 1997, however, the seasonal patterns in various parameters of the organic community started to change. This may indicate that ecosystem of Lake Suwa is changing associated with changes in lake water quality, which is being markedly restored. Therefore, since current studies are starting to show how the ecosystem responds to the water quality improvement, such studies should be intensified. To effectively conduct such studies in future, it is very important to review the results of recent studies on the organic community of the lake. For this purpose, five review papers were produced and are presented in this special issue. They concern chironomid populations, zooplankton, bloom-forming cyanobacteria and its toxins, and the fish community; all of which are characteristic of the Lake Suwa ecosystem. Three of them (papers on chironomids and zooplankton) are published in the present issue, while the remaining two will appear in the next issue.