Chinese Journal of Oceanology and Limnology Vol. 29 No. 1, P. 118-127, 2011 DOI: 10.1007/s00343-011-9106-x Marine ciliate community in relation to eutrophication of coastal waters in the Yellow Sea* XU Kuidong (徐奎栋) 1 , CHOI Joong Ki 2, ** , LEI Yanli (类彦立) 1, 2 , YANG Eun Jin 3 1 Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China 2 Department of Oceanography, Inha University, Incheon 402-751, Korea 3 Korea Polar Research Institute, KORDI, Incheon 406-840, Korea Received Dec. 23, 2009; revision accepted Jul. 6, 2010 © Chinese Society for Oceanology and Limnology, Science Press, and Springer-Verlag Berlin Heidelberg 2011 Abstract We assessed the potential of marine ciliate community as an indicator to coastal water quality using water samples collected from four stations in the Yellow Sea in the summer 2000. The four stations were characterized by different levels of pollution. The ciliate communities consisted primarily of tintinnids and aloricate ciliates that were <30 μm. A total of 78 species were classified: 55 species at Station 2, 51 species each at Stations 1 and 4, and 47 species at Station 3. The mean number of species at each site was 29.2±2.0 (Station 1), 28.5±2.9 (Station 2), 27.8±1.7 (Station 3), and 24.5±2.3 (Station 4). The abundance was highly variable: 19 331±11 187 ind./L at Station 1, 7 960±5 639 ind./L at Station 2, 29 015±12 999 ind./L at Station 3, and 8 190±4 658 ind./L at Station 4. Our results suggest that neither the simple chemical analysis (e.g. chemical oxygen demand, dissolved inorganic nitrogen, and phosphate) nor the eutrophication/pollution index adequately described the water quality at the four stations. The same was true of the number of species and their abundance, both of which had no correlation with the chemical indices. In contrast, Margalef’s diversity index values (3.12 at Station 2, 2.89 at Station 1, and 2.64 at Stations 3 and 4) generally discriminated the water quality status of the four stations. The difference in water quality among the stations was strongly supported by the pattern of species richness (i.e. the total number of species) of ciliates at each station. Our evaluation was consistent with the results of long-term water quality monitoring at the four stations. With increasing eutrophication, we observed also a compositional and functional shift in the ciliate assemblages from algivorous oligotrich/choreotrich to nonselective-omnivorous gymnostomatids to bacterivorous-detrivorous scuticociliatids. Thus, ciliates may be used to indicate the coastal water quality status of a given site. Keyword: biomonitoring; chemical evaluation; ciliates; community structure; eutrophication; marine pollution 1 INTRODUCTION Ciliates are an important component of aquatic ecosystems and are characterized by a short generation time (hours to days) and delicate membrane. Thus, ciliates are more responsive to environmental changes than other large eukaryotic organisms. For example, the community structure of ciliates is known to be affected by pollution (Cairns et al., 1972; Beaver et al., 1982; Parker, 1983; Pratt et al., 1992; Decamp et al., 1999; Madoni, 2005). Individual populations and assemblages of ciliates have been extensively evaluated as bioindicators of water quality under various types of stress (e.g. Bark et al., 1985; Dale, 1991; Kalavati et al., 1997; Xu et al., 2005). However, most studies have addressed the relationships between ciliate communities and freshwater environments. The response of ciliates to marine pollution is not well documented (Curds, 1982; Revelante et al., 1985; Lynn et al., 1992). In particular, the effect of environmental quality on marine ciliate community structure is not known. Our objective was to assess the ciliate community response to marine eutrophication. We measured a range of chemical indices and documented the relationships between ciliate community structure * Supported by the Korea Research Foundation Grant to J. K. CHOI (No. KRF-2008-013-C00064), the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-417), and the National Natural Science Foundation of China (No. 40576072, 40706047) ** Corresponding author: jkchoi@inha.ac.kr