12:00 PM - 12:15 PM
[HQR23-08] Eutrophication trends of Japanese mountain lakes inferred from sedimentary diatom assemblages
Keywords:eutrophication, Japanese mountain lakes, diatom assemblages, recent past
In this study, we examined diatom assemblages in core sediments collected from mountain lakes of Niseko-Ohnuma and Lake Rausu in Hokkaido, Mikuriga-Ike in Toyama prefecture to elucidate changes in nutrient level and pH in the lake waters associated with enhanced atmospheric pollutant depositions. In Niseko-Ohnuma diatom analysis showed changes in assemblages from acidophilous and oligotrophic taxa to neutrophil and mesotrophic taxa in 1980s. In Mikuriga-ike, the result shows that oligotrophic taxa decreased and mesotrophic taxa increased after the 1990. Meanwhile, in Lake Rausu, diatom assemblages showed minor changes around 1980s.
These observations indicated that the increases in phytoplankton and zooplankton in mountain lake ecosystems reported previously resulted from increased levels of nutrients in lake waters. Our results supported the hypothesis that enhanced atmospheric nutrient depositions after 1980s may result in eutrophication in the mountain lakes and impact the lake ecosystems.