Reconstruction of historical nutrient levels in Korean and Japanese coastal areas based on dinoflagellate cyst assemblages |
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Authors: | Hyeon Ho Shin Koichiro Mizushima Jong Sick Park Mitsunori Iwataki Yang Ho Yoon |
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Institution: | a Coastal Ecological Processes Research Division, South Sea Institute, KORDI, Geoje 656-830, Republic of Korea b Faculty of Marine Technology, Chonnam National University, Mipyeongro 386, Yeosu 550-749, Republic of Korea c Institute for East China Sea Research, Nagasaki University, 1551-7 Taira-machi, Nagasaki 851-2213, Japan d National Research Institute of Fisheries and Environment of Inland Sea 2-17-5, Maruishi, Hatsukaichi, Hiroshima 739-0452, Japan e Korea Inter-University Institute of Ocean Science, Pukyong National University 599-1, Daeyeon-dong, Nam-gu, Busan 608-737, Republic of Korea |
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Abstract: | Dinoflagellate cysts acquired from sediment cores were analyzed in order to reconstruct historical nutrient levels in Gamak Bay, Korea and Ariake Bay, Japan. Dinoflagellate cyst assemblages in Gamak Bay were characterized by high proportions of heterotrophic cysts such as Brigantedinium spp., Protoperidinium americanum and Polykrikos cysts, which suggested that nutrients levels may have already been high before 1970s, and then increased further to the hypertrophic conditions of the 1990s. In contrast, dinoflagellate cyst assemblages in Ariake Bay were characterized by high relative abundances of Lingulodinium machaerophorum and Spiniferites spp., which suggested that nutrient levels in Ariake Bay had increased gradually since the mid 1960s, and may have been significantly enhanced by the mid 1980s. Dinoflagellate cyst assemblages reflecting environmental changes in the two bays are contrasting, perhaps due to different nutrient enrichment mechanisms. This suggests that the indicators of nutrient levels encoded in dinoflagellate cyst assemblages may exhibit site-specific information. |
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Keywords: | Dinoflagellate cyst Heterotrophic cyst Lingulodinium machaerophorum Nutrient level Gamak Bay Ariake Bay |
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