| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1996: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1995: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1994: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
Relationships of bacterial, picocyanobacterial, eucaryotic picoplankton, nanoflagellate and ciliate abundances to each other and to chlorophyll a (Chl. a), total phosphorus (TP), total nitrogen (TN) and TN : TP ratio in 31 epilimnetic waters during the warm season were investigated. The abundances of bacteria and ciliates were postitively correlated with TP,TN and Chl. a, and negatively with TN : TP ratio. Linear regressions on TP and Chl. a accounted for 51% and 34% of the variability in bacterial and ciliate abundances, respectively. The abundance of heterotrophic nanoflagellates was not correlated with that of bacteria.
Polyurethane foam units (PFU) were set in the epilimnion of 15 Japanese waters and protozoan species (phytomastigophora, zoomastigophora, sarcodina and ciliata) in the squeezed water from the PFU were recorded through a high-definition (HD) TV monitor (Chu-ou mushen THMC-21BH/CH), which was connected with a HD video camera system (Nikon HQ-130C and PA-160) and the microscope (Olympus BH2) . The fauna of the protozoa in Japanese lakes was reported for first time by the present study.
The effects of silver carp on plankton communities were investigated with 6 enclosres set in Lake Kasumigaura. The 9% of the variability in heterotrophic nannofiagellate (HNF) abundance was accounted by both cladoceran (top-down effect) and bacteria (bottom-up effect) abundanes. Picocyanobacteria abundanec did not account for the variability in HNF abundance, although it is well known that HNF feeds on picocyanobacteria as well asbacteria. The variability in autotrophic flagellate abundance was closedly related with both the fish density and the dissolved inorgenic nitrogen amount.
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