利用FlowCAM研究西太平洋亞熱帶海域浮游動物體型大小與攝食率的關係

Abstract

Traditional research concerning mesozooplankton feeding has focused on adult species-specific estimates. Here, we propose to estimate in situ size-specific feedings of juvenile mesozooplankton. The motivation is based on the metabolic theory, which indicates that size plays an important role in determining predator-prey interactions. Since aquatic food webs are strongly size structured and many marine species will grow in mass by 5 or more orders of magnitude during their life cycle, we investigated size rather than species specific feeding. Moreover, our estimates provide information to evaluate community-level impacts rather than any particular target species. As such, we could investigate how much nutrition is needed for growth for mesozooplankton at the ecosystem level. In this study, mesozooplanktons are sorted into 50-80um and 100-150um size classes, which represent the two size classes that dominate the juvenile (somatic growth) biomass of the mesozooplankton community in subtropical and tropical western Pacific, and in situ incubations are carried out to calculate clearance and ingestion rates. Our experiments suggest some general trends in feeding of juvenile copepods in the subtropical and tropical western Pacific. First, clearance rates increase as food particle size increase in the big animal size fraction but no significant relationship is found in the small animal size fraction. Second, metazoan ingestion is affected more strongly by food abundance than by animal’s food preference. My results suggest that selection of food particles by juvenile copepods may be based on not only particle size but also the basis of shape, motility, taste, and previous feeding.