The system of biological production and ecological change in the huge lake promoted by the process of material loading and circulation of Lake Baikal

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We have got the following scientific results by our research for 4 years from 2002 to 2005.1. Composition and seasonal change of settling flux were examined in Barguzin Bay and off-shore area of Listvyanka. Significant increase of the flux by active biological production was observed from ice-covered to thawing periods of the lake.2. Bio-geochemical dynamics of urea was studied. Residence time of urea in the surface water was 3-6 days in summer, but was very long and 560 days in winter.3. Horizontal and vertical distributions, trophic state, production limiting factor of picophytoplankton was examined. Abundance of the plankton increased in off-shore area of Barguzin Bay, but was not under phosphorus limitation.4. Nutrient limitation in the primary production of phytoplankton was studied. In the southern and central Lake Baikal, the first limiting nutrient was thought to be phosphorus rather than nitrogen during summer.5. Dissolved organic matter was characterized with Fourier transfor … More m ion cyclotron resonance mass spectrometry. Alloctonus humic substances were elucidated to be brought to off-shore areas without denaturalization. Autochtonus organic matter, such as organic sulfur compounds, were produced in the area.6. Phosphate uptake and accumulation mechanisms of water plant were studied. Significant difference was not shown between their mechanisms of Elodea and Egeria in Lakes Baikal and Biwa.7. Standing crop and photosynthetic production of attached algal communities were studied at the littoral zone of the southern basin. High biomass were recorded especially in Ullothrix and Drapanaldiopsis dominated communities. The algal mat of Ullothrix developed on rocks on shallow near shore sites showed very high rate of gross photosynthesis.8. Vertical and horizontal abundance of bacteria, phytoplankton and protists were examined in Barguzin Bay. In off-shore, significant correlations were detected between concentrations of chlorophyll a and density of a filter feeding or raptorial ciliates.9. The abundance, growth and grazing loss rates of picophytoplankton were investigated in Barguzin Bay. There was a difference in the abundance, composition and ecological role in the microbial food web of picophytoplankton between the near-shore and the off-shore areas.10. Long time survey of water temperature was performed from June to October in 2004. Temperature decrease with 10℃ difference was observed at the same time in the surface layers on the western coasts of the central and southern basins in summer. Up-welling of deep lake water was suggested to occur. Less