Size-fractionated N2 fixation off the Changjiang Estuary during summer
Recent evidence has shown active N2 fixation in coastal eutrophic waters, yet the rate and controlling factors remain poorly understood, particularly in large estuaries. The Changjiang Estuary (CE) and adjacent shelf are characterized by fresh, nitrogen-replete Changjiang Diluted Water (CDW) and sal...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2023-05-01
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| Series: | Frontiers in Microbiology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmicb.2023.1189410/full |
| _version_ | 1797831009093287936 |
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| author | Zhibing Jiang Zhibing Jiang Zhibing Jiang Zhibing Jiang Zhibing Jiang Yuanli Zhu Yuanli Zhu Yuanli Zhu Zhenhao Sun Hongchang Zhai Feng Zhou Feng Zhou Xiaojun Yan Quanzhen Chen Jianfang Chen Jianfang Chen Jiangning Zeng Jiangning Zeng |
| author_facet | Zhibing Jiang Zhibing Jiang Zhibing Jiang Zhibing Jiang Zhibing Jiang Yuanli Zhu Yuanli Zhu Yuanli Zhu Zhenhao Sun Hongchang Zhai Feng Zhou Feng Zhou Xiaojun Yan Quanzhen Chen Jianfang Chen Jianfang Chen Jiangning Zeng Jiangning Zeng |
| author_sort | Zhibing Jiang |
| collection | DOAJ |
| description | Recent evidence has shown active N2 fixation in coastal eutrophic waters, yet the rate and controlling factors remain poorly understood, particularly in large estuaries. The Changjiang Estuary (CE) and adjacent shelf are characterized by fresh, nitrogen-replete Changjiang Diluted Water (CDW) and saline, nitrogen-depletion intruded Kuroshio water (Taiwan Warm Current and nearshore Kuroshio Branch Current), where N2 fixation may be contributed by different groups (i.e., Trichodesmium and heterotrophic diazotrophs). Here, for the first time, we provide direct measurement of size-fractionated N2 fixation rates (NFRs) off the CE during summer 2014 using the 15N2 bubble tracer method. The results demonstrated considerable spatial variations (southern > northern; offshore > inshore) in surface and depth-integrated NFRs, averaging 0.83 nmol N L−1 d−1 and 24.3 μmol N m−2 d−1, respectively. The highest bulk NFR (99.9 μmol N m−2 d−1; mostly contributed by >10 μm fraction) occurred in the southeastern East China Sea, where suffered from strong intrusion of the Kuroshio water characterized by low N/P ratio (<10) and abundant Trichodesmium (up to 10.23 × 106 trichomes m−2). However, low NFR (mostly contributed by <10 μm fraction) was detected in the CE controlled by the CDW, where NOx concentration (up to 80 μmol L−1) and N/P ratio (>100) were high and Trichodesmium abundance was low. The >10 μm fraction accounted for 60% of depth-integrated bulk NFR over the CE and adjacent shelf. We speculated that the present NFR of >10 μm fraction was mostly supported by Trichodesmium. Spearman rank correlation indicated that the NFR was significantly positively correlated with Trichodesmium abundance, salinity, temperature and Secchi depth, but was negatively with turbidity, N/P ratio, NOx, and chlorophyll a concentration. Our study suggests that distribution and size structure of N2 fixation off the CE are largely regulated by water mass (intruded Kuroshio water and CDW) movement and associated diazotrophs (particularly Trichodesmium) and nutrient conditions. |
| first_indexed | 2024-04-09T13:45:49Z |
| format | Article |
| id | doaj.art-48424ce00dbc478caead45e5dc9a8330 |
| institution | Directory Open Access Journal |
| issn | 1664-302X |
| language | English |
| last_indexed | 2024-04-09T13:45:49Z |
| publishDate | 2023-05-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Microbiology |
| spelling | doaj.art-48424ce00dbc478caead45e5dc9a83302023-05-09T04:33:47ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2023-05-011410.3389/fmicb.2023.11894101189410Size-fractionated N2 fixation off the Changjiang Estuary during summerZhibing Jiang0Zhibing Jiang1Zhibing Jiang2Zhibing Jiang3Zhibing Jiang4Yuanli Zhu5Yuanli Zhu6Yuanli Zhu7Zhenhao Sun8Hongchang Zhai9Feng Zhou10Feng Zhou11Xiaojun Yan12Quanzhen Chen13Jianfang Chen14Jianfang Chen15Jiangning Zeng16Jiangning Zeng17Key Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Ocean Space Resource Management Technology, Ministry of Natural Resource, Hangzhou, ChinaKey Laboratory of Nearshore Engineering Environment and Ecological Security of Zhejiang Province, Hangzhou, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaObservation and Research Station of Marine Ecosystem in the Yangtze River Delta, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Ocean Space Resource Management Technology, Ministry of Natural Resource, Hangzhou, ChinaObservation and Research Station of Marine Ecosystem in the Yangtze River Delta, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaObservation and Research Station of Marine Ecosystem in the Yangtze River Delta, Ministry of Natural Resources, Hangzhou, ChinaMarine Science and Technology College, Zhejiang Ocean University, Zhoushan, ChinaKey Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaKey Laboratory of Ocean Space Resource Management Technology, Ministry of Natural Resource, Hangzhou, ChinaRecent evidence has shown active N2 fixation in coastal eutrophic waters, yet the rate and controlling factors remain poorly understood, particularly in large estuaries. The Changjiang Estuary (CE) and adjacent shelf are characterized by fresh, nitrogen-replete Changjiang Diluted Water (CDW) and saline, nitrogen-depletion intruded Kuroshio water (Taiwan Warm Current and nearshore Kuroshio Branch Current), where N2 fixation may be contributed by different groups (i.e., Trichodesmium and heterotrophic diazotrophs). Here, for the first time, we provide direct measurement of size-fractionated N2 fixation rates (NFRs) off the CE during summer 2014 using the 15N2 bubble tracer method. The results demonstrated considerable spatial variations (southern > northern; offshore > inshore) in surface and depth-integrated NFRs, averaging 0.83 nmol N L−1 d−1 and 24.3 μmol N m−2 d−1, respectively. The highest bulk NFR (99.9 μmol N m−2 d−1; mostly contributed by >10 μm fraction) occurred in the southeastern East China Sea, where suffered from strong intrusion of the Kuroshio water characterized by low N/P ratio (<10) and abundant Trichodesmium (up to 10.23 × 106 trichomes m−2). However, low NFR (mostly contributed by <10 μm fraction) was detected in the CE controlled by the CDW, where NOx concentration (up to 80 μmol L−1) and N/P ratio (>100) were high and Trichodesmium abundance was low. The >10 μm fraction accounted for 60% of depth-integrated bulk NFR over the CE and adjacent shelf. We speculated that the present NFR of >10 μm fraction was mostly supported by Trichodesmium. Spearman rank correlation indicated that the NFR was significantly positively correlated with Trichodesmium abundance, salinity, temperature and Secchi depth, but was negatively with turbidity, N/P ratio, NOx, and chlorophyll a concentration. Our study suggests that distribution and size structure of N2 fixation off the CE are largely regulated by water mass (intruded Kuroshio water and CDW) movement and associated diazotrophs (particularly Trichodesmium) and nutrient conditions.https://www.frontiersin.org/articles/10.3389/fmicb.2023.1189410/fullN2 fixationTrichodesmiumunicellular diazotrophsChangjiang EstuaryChangjiang Diluted WaterKuroshio |
| spellingShingle | Zhibing Jiang Zhibing Jiang Zhibing Jiang Zhibing Jiang Zhibing Jiang Yuanli Zhu Yuanli Zhu Yuanli Zhu Zhenhao Sun Hongchang Zhai Feng Zhou Feng Zhou Xiaojun Yan Quanzhen Chen Jianfang Chen Jianfang Chen Jiangning Zeng Jiangning Zeng Size-fractionated N2 fixation off the Changjiang Estuary during summer Frontiers in Microbiology N2 fixation Trichodesmium unicellular diazotrophs Changjiang Estuary Changjiang Diluted Water Kuroshio |
| title | Size-fractionated N2 fixation off the Changjiang Estuary during summer |
| title_full | Size-fractionated N2 fixation off the Changjiang Estuary during summer |
| title_fullStr | Size-fractionated N2 fixation off the Changjiang Estuary during summer |
| title_full_unstemmed | Size-fractionated N2 fixation off the Changjiang Estuary during summer |
| title_short | Size-fractionated N2 fixation off the Changjiang Estuary during summer |
| title_sort | size fractionated n2 fixation off the changjiang estuary during summer |
| topic | N2 fixation Trichodesmium unicellular diazotrophs Changjiang Estuary Changjiang Diluted Water Kuroshio |
| url | https://www.frontiersin.org/articles/10.3389/fmicb.2023.1189410/full |
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