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| 1.
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辻井, 宏之 ; 酒寄, 淳史 ; 川幡, 佳一 ; 井原, 良訓 ; Tsujii , Hiroyuki ; Sakayori, Atsushi ; Kawabata, Keiichi ; Ihara, Yoshinori
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| 2.
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Urabe, Jotaro ; Kawabata, Keiichi ; Nakanishi, Masami ; Shimizu, Kensuke
概要:
金沢大学教育学部理科教育<br />Community grazing rate of zooplankton larger than 98 μm in body size were examined at the north and so
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uth basins of Lake Biwa in late summer, 1993. The lake seston labeled with 14C was divided into different size fraction (<2,2-8,8-20 and 20-70 μm), and the grazing rate of each size fraction was determined under ambient food condition. During the study period, Eodioptomas japonicus dominated followed by Daphnia galeata at both sites. In all experiments, the grazing rate was higher for middle size fractions (2-8 and 8-20 μm) than the smallest and largest size fractions, indicating that the zooplankton communities selectivity remove section in the size range of 2-20 μm. Community ingestion rate estimated from the grazing rate and abundance of ambient seston revealed that seston in the middle size fraction was main food of zooplankton. When abundance of sestor, <20 μm was low relative to those >20 μm, however, the largest size fraction contributed 57% of the ingested carbon, suggesting that the food source of zooplankton is not necessarily restricted to the small sestonic particles, even if feeding efficiency was low for large sestonic particles. Based on grazing rate, 6 to 10% of total seston was estimated to be removed by the zooplankton community within a day.
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| 3.
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Kawabata, Keiichi
概要:
Clearance rate of the planktonic cyclopoid copepod Mesocyclops dissimilis on the planktonic calanoid copepod Eodiaptomus
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japonicus was measured in laboratory experiments. Ontogenetic changes were investigated using several combinations of different developmental stages of the two species. To minimize the side effects of laboratory experiments, predation was examined for a short duration using field-captured animals at natural prey densities and temperatures. Individual predators showed a large variation in the clearance rate even within replicates of the same experiment. The clearance rates of adult female predators on late naupliar prey were similar (about 0.15 L ind. -1 d-1) within a range of prey density 12-31 ind. L _1. Ontogenetic tendencies in clearance rate, though seldom significant, translated to an increase with development of the predators and a decrease with that of the prey. Present clearance rates and the natural densities of predators and prey suggest that M. dissimilis was sometimes an influential predator of E. japonicus in the field. © The Plankton Society of Japan and The Japanese Association of Benthology.
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Kawabata, Keiichi
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