Effects of the copepod community structure on fecal pellet flux in Kagoshima bay,a deep,semi-enclosed embayment |
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| Authors: | Toru Kobari Hiroyasu Akamatsu Masato Minowa Toshihiro Ichikawa Kazuo Iseki Ryuji Fukuda Masataka Higashi |
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| Institution: | 1.Fisheries Biology and Oceanography Division, Faculty of Fisheries,Kagoshima University,Shimoarata, Kagoshima,Japan;2.Department of Earth and Environment Science, Faculty of Science,Kagoshima University,Korimoto, Kagoshima,Japan;3.Graduate School of Biosphere Science,Hiroshima University,Kagamiyama, Higashi-Hiroshima,Japan;4.Nansei-Maru, Faculty of Fisheries,Kagoshima University,Shimoarata, Kagoshima,Japan;5.Kagoshimai-Maru, Faculty of Fisheries,Kagoshima University,Shimoarata, Kagoshima,Japan |
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| Abstract: | Seasonal changes in the shape and size composition of fecal pellets were investigated with sediment trap samples from 50 and
150 m in Kagoshima Bay to evaluate how the mesozooplankton community affects fecal pellet flux. Deep vertical mixing was evident
in March, and thermal stratification was developed above 50 m in June, August and November. Chlorophyll a, suspended particulate organic carbon (POC) and copepod abundance were uniform throughout the water column during the seasonal
mixing and concentrated above 50 m in the stratified seasons. Calanoids were the most predominant copepods in March and poecilostomatoids
composed more than 45% of the copepod community in June, August and November. Fecal pellet fluxes at 50 and 150 m were the
highest in March, nearly half of POC flux. The relative contribution declined considerably in the other months, especially
for less than 4% of POC flux in August. The decline was corresponded to the predominance of cyclopoids and poecilostomatoids.
Cylindrical pellets dominated the fecal matters at both depths throughout the study period, while larger cylindrical pellets
nearly disappeared at 150 m in June, August and November. Copepod incubation revealed that cylindrical and oval pellets were
egested by calanoids and the other copepods, respectively. We suggest that cylindrical fecal pellets produced by calanoid
copepods contribute to feces flux but the predominance of poecilostomatoids and/or cyclopoids decreases feces flux via the
increase of oval pellets and fragmentation of larger cylindrical pellets. |
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