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General Session 2: Marine & estuarine biogeochemistry |
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Seasonal variations of ammonium uptake and regeneration rates in the Changjiang (Yangtze) River estuary
Wednesday 11th @ 1130-1150
Conference Hall
Zaixing Wu* , Key laboratory of marine ecology and environmental sciences, Chinese Academy of Sciences;Laboratory of Marine Ecology and Environmental Science, Qingdao National laboratory for Marine Science and Technology
Wentao Wang, Key laboratory of marine ecology and environmental sciences, Chinese Academy of Sciences;Laboratory of Marine Ecology and Environmental Science, Qingdao National laboratory for Marine Science and Technology
Xiuxian Song, Key laboratory of marine ecology and environmental sciences, Chinese Academy of Sciences;Laboratory of Marine Ecology and Environmental Science, Qingdao National laboratory for Marine Science and Technology
Xihua Cao, Key laboratory of marine ecology and environmental sciences, Chinese Academy of Sciences;Laboratory of Marine Ecology and Environmental Science, Qingdao National laboratory for Marine Science and Technology
Yongquan Yuan, Key laboratory of marine ecology and environmental sciences, Chinese Academy of Sciences;Laboratory of Marine Ecology and Environmental Science, Qingdao National laboratory for Marine Science and Technology
Zhiming Yu*(corresponding author), Key laboratory of marine ecology and environmental sciences, Chinese Academy of Sciences;Laboratory of Marine Ecology and Environmental Science, Qingdao National laboratory for Marine Science and Technology
Presenter Email: wuzx@qdio.ac.cn
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| The ammonium uptake and regeneration rates in different seasons (spring, summer and autumn) of the Changjiang (Yangtze) River estuary were measured by conducting onboard time course experiment, with 15NH4+ as a tracer. Isotope dilution models were also utilized for calculation of these rates. The ammonium uptake rates in three seasons exhibited a wide range which were between 0.2¦̀mol•L-1•d-1 to 18.17¦̀mol•L-1•d-1, while regeneration rates between 0.07¦̀mol•L-1•d-1 to 8.32¦̀mol•L-1•d-1. The ammonium uptake rates in three seasons were almost higher than the regeneration rates for most sampling sites. Both the rates of ammonium uptake and regeneration in the upper water column (surface layer or subsurface chlorophyll maximum layer) was higher than that in the bottom layer in the three seasons. Nitrification, as another important removal process of ammonium, might be responsible for these low uptake and regeneration rates at bottom waters. Temporally, the ammonium uptake rates in summer were the highest, followed by spring, with lowest rate observed in autumn. Comparatively, the lowest ammonium regeneration rate was observed also in autumn, while regeneration rates in spring and summer did not differ significantly, which may be regulated by the phytoplankton/bacteria biomass. Measurement of ammonium uptake and regeneration rates directly helped to gain further insight about the seasonal variations of the ammonium biogeochemical processes in the Changjiang (Yangtze) River estuary. |
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