IKEDA and MOTODA: ZOOPLANKTON PRODUCTION AND AMMONIA EXCRETION 



three parameters: zooplankton biomass, size dis- 

 tribution, and habitat temperature. Although we 

 obtained size distribution indirectly it should be 

 obtainable directly. The fitting of zooplankton size 

 distribution data to the normal distribution curve 

 may not be necessary in some instances but this 

 will facilitate calculations. To estimate production 

 from respiration data, constant values of digestion 

 efficiency andK^ were used in this study, but these 

 can be used as variables. From morphological 

 characteristics of feeding organs, Timonin (1971) 

 reported that 50-80% of zooplankton biomass in 

 the Indian Ocean were carnivores and Motoda and 

 Minoda (1972) reported that 20-277f of zooplank- 

 ton numbers in the Kuroshio region were herbi- 

 vores. These values are below the herbivore:car- 

 nivore ratios we calculated. 



Since only zooplankton data were collected with 

 0.35-mm mesh nets and smaller zooplankters pass 

 through this mesh size, we probably underesti- 

 mated zooplankton biomass. According to Beers 

 and Stewart (1971) biomass of microzooplankton 

 including copepod nauplii, ciliates, foraminifer- 

 ans, and radiolarians was 12-Il'7c (24% on aver- 

 age) of total zooplankton collected in 202-/i.m nets 

 in the eastern tropical Pacific Ocean. The impor- 

 tant role of microzooplankton as a secondary pro- 

 ducer and nutrient regenerator in pelagic marine 

 ecosystems is anticipated but suitable data are yet 

 unavailable for modeling. 



ACKNOWLEDGMENTS 



We would like to express our appreciation to A. 

 Taniguchi, Faculty of Agriculture, Tohoku Uni- 

 versity, for his constructive criticism, and M. Gil- 

 martin, Australian Institute of Marine Science for 

 his critical reading of the manuscript. We are 

 grateful to K. Kyushin, Faculty of Fisheries, Hok- 

 kaido University, and M. Iwata, Ocean Research 

 Institute, Tokyo University, for their helpful 

 suggestions on the statistical treatment of data. 

 We also appreciate the laborious work at sea by 

 participants in the CSK synoptic survey on board 

 the TS Oshoro Maru, Hokkaido University, the TS 

 Umitaka Maru, Tokyo University of Fisheries, the 

 TS Nagasaki Maru, Nagasaki University, and the 

 TS Kagoshima Maru, Kagoshima University. 



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