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General Session 3: Biological oceanography & global change |
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Habitat controls on phytoplankton community structure and primary productivity in the northern South China Sea
GS3-61
Yuyuan Xie* , State Key Laboratory of Marine Environmental Science, Xiamen Univerisity, China
Bangqin Huang, State Key Laboratory of Marine Environmental Science, Xiamen Univerisity, China
Xin Liu, State Key Laboratory of Marine Environmental Science, Xiamen Univerisity, China
Wupeng Xiao, State Key Laboratory of Marine Environmental Science, Xiamen Univerisity, China
Presenter Email: xieyuyuan@xmu.edu.cn
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| Phytoplankton plays an important role in structuring marine ecosystem. The relationship between primary productivity and environmental drivers is basic and necessary to quantifying the carbon cycle to which phytoplankton contributes. The previous study [Xie et al. (2015) JGR-Oceans 120: p4178] has implied that the light and temperature dependence of photosynthesis varies with the structure of phytoplankton community in the northern South China Sea (NSCS). In this study, we aim to assess the physical and chemical controls on primary productivity by distinguishing the effects of species diversity. The clustering algorithm shelf-organizing maps (SOM) was used to categorize the phytoplankton community structure. Seven categories were identified and found to occupy in the habitats that are separated by depth, temperature, nutrients, salinity and structured by physical processes such as upwelling, river plume, summer stratification and winter mixing. Along the two gradients: (1) coastal-basin gradient varying with nutrient supply; (2) vertical gradient of light, temperature and nutrient; the diatoms-dominated coastal category and the Synechococcus-dominated river plume category displayed the highest primary productivity which was supported by the highly available nutrients, the prokaryotes-dominated category occupied in the stratified ocean surface and the nutrient-limited primary productivity was relatively low, and the haptophytes usually dominated in the bottom of euphotic zone and those two categories showed the lowest primary productivity that was light-limited. The primary productivity shows significant but differential temperature-dependence for the diatoms-dominated coastal category, the haptophytes-dominated categories and the mixed category. These results revealed that the physiological acclimation can pose effects at a high taxonomic level when the ecological adaptation at the community level (succession in species composition) usually occurs in a complex marine ecosystem. These findings also offer the evidences that support the explicit use of phytoplankton functional groups in marine ecological models. |
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