Yuichiro Nishibe

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Seasonal changes in abundance of the testate amoeba Penardochlamys sp. and its food vacuole contents were investigated in relation to blooms of the cyanobacteria Microcystis spp. in a hypertrophic pond from April 1999 to March 2000. The behavior of the amoeba feeding on M. aeruginosa and M. wesenbergii was also observed in the laboratory. The amoeba was(More)
Seasonal change in the abundance of autotrophic picoplankton (APP) was investigated once or twice a week in relation to some environmental variables in a hypereutrophic pond, from July 1999 to June 2000. Cell density of APP ranged between 0.3×105 and 10.1×105 cells ml−1, overlapping the lower range of APP abundances given in the literature for(More)
The importance of analyzing the determinants of biodiversity and community composition by using multiple trophic levels is well recognized; however, relevant data are lacking. In the present study, we investigated variations in species diversity indices and community structures of the plankton taxonomic groups-zooplankton, rotifers, ciliates, and(More)
Planktonic heterotrophic bacteria in lakes utilize the labile fraction of dissolved organic carbon (DOC), although information about seasonal changes in labile DOC in hypertrophic lakes in terms of absolute amount and relative proportion of the total DOC is still limited. We conducted DOC decomposition experiments using GF/F filtrates in water samples from(More)
Planktonic microbial interactions in the central basin of Lake Baikal were examined on a summer day in 1999. The subsurface maxima of bacterial abundance and chlorophyll concentration were recorded at the same depth, whereas the vertical distribution of heterotrophic nanoflagellates was the inverse of those of bacteria and picophytoplankton. Release of(More)
Onboard incubation experiments were conducted to examine the feeding rates and selectivity of the cyclopoid copepod Oithona similis on natural assemblages of microplankton during the spring bloom in the Oyashio region. O. similis cleared ciliates at higher rates (2.8–11.9 mL copepod 1 d ) than dinoflagellates (1.4 mL copepod 1 d ), with no detectable(More)
We examined the growth of testate amoebae preying on Microcystis whose physiological states were different in laboratory experiments and a hypertrophic pond. We prepared three experimental systems using water samples dominated by Microcystis aeruginosa: light incubation (control), dark incubation (dark), and light incubation with addition of nitrogen and(More)
Seasonal changes in abundance of planktonic microorganisms, together with some physico-chemical variables, were monitored monthly from May 1999 to March 2002 in the surface water of a coastal bay where nutrients are mainly supplied by intermittent intrusions of deeper water (bottom intrusion). No significant bottom intrusion was detected in 1999 but large(More)
Characteristics of a magnetostrictive torque sensor were studied in the excitation current range 10~1000 mA and at excitation frequencies from 1 kHz to 100 kHz. Ni-Cr-Mo steel (JIS standard SNCM439) ferromagnetic material was used in an experimental shaft because of its high mechanical strength under applied torques ranging - 1500~1500 Nm. As the excitation(More)
Seasonal changes of zooplankton communities were monitored at two coastal marine areas, Uchiumi and Fukuura Bays located at the Uwa Sea, east side of Bungo Channel. The two sites are close to each other (c.a. 20 km) with similar habitat environments, but receive different environmental stresses from aquaculture activities, pearl oyster farming for Uchiumi(More)