| Summary: | 碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 95 === The Changjiang (CJ) River freshwater discharge was affected by the installation of the Three-Gorges Dam (TGD) and the variation of freshwater outflow to the East China Sea was influenced by the continental ecosystem. The impact of the freshwater discharge upon the ciliate community of East China Sea was investigated during six summer cruises of the R/V Ocean Researcher I from 2003 to 2006.
When the first filling stage of the reservoir was completed in June 2003, we detected no significant changes in salinity, in the meantime the ciliate near the CJ plume reached the peak abundance, which was negatively correlated with salinity. In 2004, the highest abundance of ciliates appeared at the salinity of higher than 31 psu. The ciliate vertical distribution within CJ plume, in the area that salinity was lower than 31 psu, the peak abundance of ciliate (>400 cells L-1) occurred at the surface water (<15 m). Outside the CJ plume (>31 psu) the peak abundance (>100 cells L-1) was observed at two depths, the surface layer (<20 m ) and the subsurface layer (40~60 m). The ciliate abundance did not show significant difference among these cruises except the last cruise in June 2006, which had the lowest abundance. The ratio of mixotrophic abundance (MC) to total ciliate (TC), or MC/TC changed significantly following the water discharge. It was about 9.7~13.0% in 2003, and increased to 20~40% in 2004~2006. In 2003, the smallest ciliate (<16 μm) contributed about 30% to the ciliate community with the average size of 23~25.7μm. The ciliate body size has increased noticeably since 2004 with average size of 31.1~39.2μm, and ciliates of >36μm became the dominant group and contributed up to 30% to the ciliate community.
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