| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1989: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1988: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The responses and acclimation mechanisms of a natural microbial community to operation-of the "Bio-filter System" in Doh-Hoh-Numa Bog show that the resulting rapid oligotrophication proceeded in the reverse direction of the previous eutroppication processes, thereby restoring the original physicochemical and biological components through rapid microbial adaptation at the level of the community. These results in Doh-Hoh-Numa Bog elucidate clearly the steady-state equilibrium of a freshwater ecosystem, with special reference to the threshold theory of eutrophication (e.g., Seki, H.; Organic Materials in Aquatic Ecosystems. CRC Press, Florida, 1982).
The ecosystem of Doh-Hoh-Numa Bog was rapidly modified within a few weeks from a moderately mesotrophic down to the lower boundary of mesotrophic systems by operating a water-area purifying system. This artificial removal of nutrients has the great advantage of depressing a bloom of aquatic blue-green algae during the summer; the photosynthetic rate of the phytoplankton community was reduced to about 50% during summer as the result of a 50% reduction in nutrient concentrations. Physiological responses of all members of the bacterial community were also modified to become more oligotrophic, as the plankton and epiplankton formed a single community, with the epiphyton on solid surfaces being recruited from the plankton. These modifications of microbial processes took place through reversible alternations of the most predominant microbial species, without changing the species composition of the microbial community. Moreover, ammonium and dissolved organic carbon were the limiting factors for the phytoplankton photosynthesis and for bacterial growth, respectively, both before and after rapid oligotrophication.
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