Research of role, biodiversity, and material metabolism in oligotrophic lakes

点击翻译按钮获取中文摘要

Lake Akan-Panke is in oligotrophic level, and small sized phytoplankton (<2μm) produced organic matter dominated in stratified period. In contrast, large sized phytoplankton (>20μm, mainly diatoms) dominated in circulation period. In May, phytoplankton distributed in deep layer (before formation of thermocline) derived from large sized phytoplankton (mainly diatoms) grown in surface layer (or near). Those sank slowly to the bottom, and maintained 20% of photosynthetic activity as compared to the activity of phytoplankton in the surface layer. Primary production in this lake was maintained by picophytoplankton except for May and November in circulation period.Acid and oligotrophic Lake Inawashiro was so low level for biomass of phytoplankton as compared to Oligotrophic Lake Akan-Panke. Although nutrient concentration was so low level, this lake was lack in COィイD22ィエD2 needed for photosynthesis of phytoplankton (<0.5 mgC/l). In addition, population number of bacteria decomposed organic m … More atter was also low (<5X10ィイD15ィエD1 cells/l) as compared to neutral oligotrophic lake. These facts mean that metabolism of organic matter in this lake is so different to general type of lake. Biodiversity of this lake is also markedly different to general lakes. The limiting factor in acid lake for primary production, origin of organic matter in lake, and its decomposer must be made clear in near future.Eutrophic Lake Barato was researched to compared the variation in biodiversity and selection of dominant phytoplankton species in oligotrophic lake, and this lake dominated Aphanizomenon flos-aqae, Anabaena sp. And Microcystis aeruginosa (Cyanophyce). Although these species selected from May to July raised water temperature, the selection could not be proved the reason. In this lake, nutrient concentration, excepcially change of orthophosphate concentration, was so important with water temperature. Change of biodiversity in Lake Barato at least concerned cell population dominant diatom besides raise of water temperature and orthophosphate concentration. Less