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Nitrogen cycling in the ocean: From genes to ecosystems and from the past to the future
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Salinity effect on nitrification efficiency and N2O production pathway in eutrophic estuarine
P-M5-12-S
Yutong Zhou* , author
Ehui Tan, colleague
Wenbin Zou, colleague
Shu-Ji Kao, supervisor
Presenter Email: ytzhou@stu.xmu.edu.cn |
| Strongly influenced by anthropogenic excess nutrient, estuaries are areas of intense biogeochemical processing, transporitng terrestrial inputs of fixed N to coastal waters as well as releasing greenhouse gas N2O to the atmosphere. Owing to the influence of tide and wave, estuaries experience a wide salinity range, making the complex N cycle even more tricky. Nitrification, including ammonia oxidation to nitrite and nitrite oxidation to nitrate, decides the forms and distribution of inorganic N, also serve as major contributor to atmospheric N2O. The two steps of nitrification are carried out by different performers - ammonia oxidizing microbe and nitrite oxidizing bacteria. It is reported,that these two groups of microorganisms show different sensibility to salinity shock and some may get inhibited on their activities of N2O reductase. However, not only are these existing studies almost exclusively based on bioreactors, but also the quantitative results as well as specific mechanisms behind yet to be clarified. In this study, water sample was taken at the fresh water side of Jiulong River, a typical eutrophic estuary in south-east of China, a gradient of NaCl was then added to different cultivation systems adjusting the final salinity to 1, 2, 3, 4, 5, 7, 10 and 25. By applying isotope labeling technique, we would like to figure out at what extent do ammonia oxidation and nitrite oxidation decouple when saline water invades, moreover, how would this alter N2O production among different pathways. This work aims to further our awareness of salinity effect on N cycle in field study, it may also give clues on other biogenic elements studies such as C, P, O, S and Fe which tightly intertwine with N cycle. |
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