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General Session 3: Biological oceanography & global change |
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Nitrogen fixation in a subtropical bay in south China which strongly affect by human activities
GS3-24-S
Danyang Li* , College of Ocean and Earth Sciences
Isotope Marine Chemistry
Xiamen University
Presenter Email: 370537441@qq.com
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| Nitrogen fixation rate and its relations with other environmental and biological factors in Daya Bay were investigated during summer and winter in 2015,and spring in 2016.To our knowledge,nitrogen fixation has never been reported in Daya Bay and this is the first report of direct measurement of nitrogen fixation rate using 15N2 tracer assay here.Average surface nitrogen fixation rate was recorded the highest in summer (10.8 μmol N/m3.d),and the lowest in winter (3.2 μmol N/m3.d),which are much higher than those in the adjacent South China Sea.The relatively high nitrogen fixation rate in Daya Bay indicates that even in such an environment with high concentration of dissolved inorganic nitrogen,the nitrogen fixation activities can still happen and even reach a strong level.The growth and nitrogen fixation activity of diazotrophs are sensitive to environmental changes and since may undergo several structural-functional changes in the special environment of Daya Bay,including modifications to their growth rates and metabolism.There was a significant correlations between nitrogen fixation rate and water temperature,which means water temperature is a major controlling facor of diazotrophs in Daya Bay.In additon,we found a strong positive correlation between ntrogen fixaton rates and primary producion.However,the contributions of nitrogen fixation to primary production in Daya Bay are little.We speculate the Daya Bay has a diversity diazotrophic community,of which the heterotrophic diazotrophs symbiotic with primary producer are important components.The composition of diazotrophic community and the activities of diazotrophs in Daya Bay may reflect the influences of anthropogenic activity and eutrophication in Daya Bay. |
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