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Nitrogen cycling in the ocean: From genes to ecosystems and from the past to the future
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The effect of nitrogen cycles in the Kuroshio on the marine environment of East China Sea
Monday 7th @ 1430-1450, Multifunction Hall
Wentao Wang* , CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences
Zhiming Yu, CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences
Xiuxian Song, CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences
Yongquan Yuan, CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences
Zaixing Wu, CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences
Presenter Email: wtwang@qdio.ac.cn |
| In 2014, in the southern East China Sea (ECS) and east of Taiwan, nutrient and isotope samples were collected and analyzed. Also, dissolved oxygen (DO), chlorophyll-a, and physical parameters were determined. The Kuroshio subsurface water intruded into the ECS and separated into two branches on the continental shelf: the nearshore Kuroshio branch current (NKBC) and the offshore Kuroshio branch current (OKBC). The NKBC was able to extend to nearshore area in spring while it was hardly to be described in autumn. In spring, the variations of DO, nitrate and nitrogen isotopes in the bottom water showed that continuous nitrification occurred in the NKBC after intrusion into the ECS. This process might contribute to the hypoxia zone near the coast of Zhejiang Province, China. However, in autumn, the biogeochemical process was weak to lead the nutrients variations. Additionally, higher phosphorus (P) concentrations was transported onto the ECS continental shelf in autumn. Through the water columns analysis, we speculate that the distinctions among the seasonal variations of P-enriched water masses were attributable to the different intrusion positions of the Kuroshio. Moreover, according to the Rayleigh model, primary production in most of southern ECS was supported by the intrusion of the Kuroshio subsurface water, causing 5бы isotope fractionation. In some of nearshore stations which located in the northern investigated area, the assimilated nitrate was contributed from both the NKBC and coastal currents originated from the Changjiang diluted water. |
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