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Circulation, biogeochemistry and carbon cycling in ocean margins
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Regulation mechanism of phytoplankton community on Particulate Organic Carbon export based on sediment trap in northern South China Sea
P-M1-20-S
Yiwei Shang* , College of Environment and Ecology, Xiamen University
Yong Qiu, College of Environment and Ecology, Xiamen University
Wupeng Xiao, College of Environment and Ecology, Xiamen University
Xin Liu, College of Environment and Ecology, Xiamen University
Bangqin Huang, College of Environment and Ecology, Xiamen University
Presenter Email: yshang@stu.xmu.edu.cn |
| The oceanic biological pump drives photosynthetically produced organic matter from the surface layer to depth via sinking particles which main composed of phytoplankton, zooplankton fecal pellets (FPs) and organic aggregates. Because of the unique environmental settings in northern south China sea, and the temporal-spatial variations of biological communities, regulation mechanism of phytoplankton community on Particulate Organic Carbon export is still unknown. We investigated phytoplankton community and Particulate Organic Carbon export from coast to basin in the South China Sea during two cruises in Aug. 2017 and Aug. 2018. Sediment traps were deployed in slope, shelf and basin stations, respectively. Generalized additive models (GAMs) were used to analyze the regulation mechanism of phytoplankton community on zooplankton fecal pellets sinking rates and POC content. From trap samples, it shows that cylindrical fecal pellets from copepods are the main contributors to POC flux. Meanwhile, fecal pellets POC flux (34.2-102.1mg C m-2 d-1) and contribution ratio to total POC flux increased (about 27~84%) at the bottom of euphotic zone in stations located in coast-shelf-slope-basin. In the water column, the cylindrical FPs from copepods are the dominant groups of FPs as well. Besides, POC content of zooplankton FPs decreased, but the contribution ratio to total POC increased (t-test, p<0.05, .5) in the section from coast to off-shore. POC content of FPs was positively related to total phytoplankton biomass as revealed by generalized additive models. Moreover, we found that biomass of dinoflagellates and diatoms can explain 60% of variation in the sinking rate of FPs. We concluded that POC content of FPs was controlled by phytoplankton total biomass, while phytoplankton community structure plays an important role in regulating sinking rates of FPs. Large phytoplankton (Diatom and Dinoflagellate) are the main groups affecting the sinking rate of fecal pellets. Thus, the change of phytoplankton community in biomass and structure affect zooplankton fecal pellets POC content and sinking rate, in turn, affect the POC flux, regulating the biological pump efficiency. |
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