| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 100 === Bioactive trace elements (Fe, Zn, Cu, Ni and Cd) were taken up by phytoplankton in euphotic zone through various biological processes. Accumulation in the zooplanktons mainly through feeding process (trophic transfer), any unassimilated trace elements will be rapidly packaged into fecal pellets and transported out to surface waters. However, zooplankton bio-concentration or trophic transfer of trace metals, whether caused by dietary behavior or metabolic function remain a main issue for trace metals biogeochemical cycle in marine environment. In this study, using ultraclean techniques, elemental and metals concentration of selected zooplanktons at various sizes (sizes in μm: 10~63, 63~153, 153~363, 363~500, 500~1000, 1000~2000, >2000) were analyzed. It was found, on average, that only ~73% of trace metals were intercellular, remained ~27% were adsorbed on exoskeleton. Concentrations of Fe, Zn, Cu, Ni and Cd in zooplanktons increased with sizes, on average, 361±455、98.87±60.61、8.43±4.10、5.53±3.18 and 3.02±2.02 μg g-1 respectively, with various metal to elemental ratios (TM:C, TM:N and TM:S). Fecal pellets, exoskeletons, and intracellular materials all show distinctive diverse metal concentration levels. Fe, Cu and Ni were mostly in exoskeleton (Fe: 66%, Cu: 64%, Ni:75%); but, only 1% for Cd. Incubation experiments also revealed that zooplanktons have different trace metals requirement at various growth stages, due to environmental conditions, trophic levels, metabolism mechanisms and food sources. Over all, these findings suggest that zooplankton were deliberately accumulated essential metals, not passively as previously believed. Metal detoxification is actively involved in its life cycles which have profound impact on biogeochemistry of trace metals in the ocean.
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