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General Session 2: Marine & estuarine biogeochemistry |
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Synechococcus assemblages across the salinity gradient in a salt wedge estuary
GS2-48
Xiaomin Xia* , The Hong Kong University of Science and Technology
Wang Guo, The Hong Kong University of Science and Technology
Shangjin Tan, The Hong Kong University of Science and Technology
Hongbin Liu, The Hong Kong University of Science and Technology
Presenter Email: xmuraji@gmail.com
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| We investigated the vertical profiles of Synechococcus abundance, taxonomic composition and pigment genetic diversity in a salt-wedge estuary (the Pearl River estuary) by flow cytometric analysis and pyrosequencing of the rpoC1 gene and cpcBA gene. A strong vertical stratification of Synechococcus assemblages was detected and Synechococcus abundance in the surface water was higher than in the bottom water in the Pearl River estuary. The surface water influenced by freshwater discharge from the Pearl River was inhabited by PC (phycocyanin-containing) Synechococcus, while the bottom water with high salinity and relatively low nutrient was occupied by PE (phycoerythrin) Synechococcus. High abundance of clade III found in the brackish water may revise our previous understanding that clade III prefers oligotrophic environment. Our data also further revealed that S5.3, a not well-understood lineage, had a preference for deep water. Clade I, a typical cold water lineage, may also ¡°hide¡± in deep layer of tropical/subtropical coastal waters. Salinity was a key factor influencing Synechococcus community composition in the Pearl River estuary. Contrasting distribution patterns of niche partitioning between pigment type 1 and type 3 Synechococcus were also observed. The salt wedge estuary provides various hydrographic conditions (or niches) for different lineages of Synechococcus, making it an environment with high Synechococcus diversity. |
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