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Nitrogen cycling in the ocean: From genes to ecosystems and from the past to the future
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Nutrient-limitation and response to increasing CO2 of diazotrophic cyanobacteria in the South China Sea
Monday 7th @ 1030-1050, Multifunction Hall
Zuozhu Wen* , State Key Laboratory of Marine Environmental Science (Xiamen University)
Wenfang Lin, State Key Laboratory of Marine Environmental Science (Xiamen University)
Rong Shen, State Key Laboratory of Marine Environmental Science (Xiamen University)
Jian Pang, State Key Laboratory of Marine Environmental Science (Xiamen University)
Tianli He, State Key Laboratory of Marine Environmental Science (Xiamen University)
Haizheng Hong, State Key Laboratory of Marine Environmental Science (Xiamen University)
Dalin Shi, State Key Laboratory of Marine Environmental Science (Xiamen University)
Presenter Email: wenzuozhu2014@stu.xmu.edu.cn |
| We examined short-term (72h) responses of natural diazotrophic cyanobacteria to nutrient (Fe and P) amendments and ocean acidification (OA) in on-deck incubation experiments conducted between May 2016 and August 2017 in the North South China Sea (NSCS) and the upstream Kuroshio. Nutrient amendment experiments revealed distinct nutrient limitation patterns of N2 fixation between the Kuroshio and the NSCS, with P-limitation in the Kuroshio and Kuroshio-affected stations and Fe and P co-limitation in the NSCS. The results suggested that in the Kuroshio and Kuroshio-affected regions extra inputs of Fe should exist to support high standing stocks of Trichodesmiun and drive the systems to P-limitation. In acidification experiments, Trichodesmium was the dominating phylotypes based on the qPCR amplification of planktonic nifH genes, and N2 fixation rates were significantly decreased under acidified conditions in five of the six experiments. In the station where no OA effect OA was observed, hydrological data showed that it was under the strong influence of the Kuroshio instruction and thus likely received sufficient Fe, which may have greatly promoted N2 fixation and mitigated the negative effect of OA. Our study demonstrated that N2 fixation by natural Trichodesmium populations in the NSCS was suppressed by OA, and the negative effects can be modulated by the availability of nutrients. |
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