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  • 1
    Online Resource
    Online Resource
    Biogeography of N 2 Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea
    American Geophysical Union (AGU) ; 2019
    In:  Journal of Geophysical Research: Oceans Vol. 124, No. 10 ( 2019-10), p. 6983-6996
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 124, No. 10 ( 2019-10), p. 6983-6996
    Abstract: The oligotrophic Kuroshio Current intrusion into the South China Sea generates a new biogeographic regime characterized by high N 2 fixation Trichodesmium contributes 〈 10% of primary production yet creates a positive correlation between N 2 fixation and primary production
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2018JC014781
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2019
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    SSG: 16,13
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  • 2
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    Global oceanic diazotroph database version 2 and elevated estimate of global oceanic N 2 fixation
    Copernicus GmbH ; 2023
    In:  Earth System Science Data Vol. 15, No. 8 ( 2023-08-15), p. 3673-3709
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 15, No. 8 ( 2023-08-15), p. 3673-3709
    Abstract: Abstract. Marine diazotrophs convert dinitrogen (N2) gas into bioavailable nitrogen (N), supporting life in the global ocean. In 2012, the first version of the global oceanic diazotroph database (version 1) was published. Here, we present an updated version of the database (version 2), significantly increasing the number of in situ diazotrophic measurements from 13 565 to 55 286. Data points for N2 fixation rates, diazotrophic cell abundance, and nifH gene copy abundance have increased by 184 %, 86 %, and 809 %, respectively. Version 2 includes two new data sheets for the nifH gene copy abundance of non-cyanobacterial diazotrophs and cell-specific N2 fixation rates. The measurements of N2 fixation rates approximately follow a log-normal distribution in both version 1 and version 2. However, version 2 considerably extends both the left and right tails of the distribution. Consequently, when estimating global oceanic N2 fixation rates using the geometric means of different ocean basins, version 1 and version 2 yield similar rates (43–57 versus 45–63 Tg N yr−1; ranges based on one geometric standard error). In contrast, when using arithmetic means, version 2 suggests a significantly higher rate of 223±30 Tg N yr−1 (mean ± standard error; same hereafter) compared to version 1 (74±7 Tg N yr−1). Specifically, substantial rate increases are estimated for the South Pacific Ocean (88±23 versus 20±2 Tg N yr−1), primarily driven by measurements in the southwestern subtropics, and for the North Atlantic Ocean (40±9 versus 10±2 Tg N yr−1). Moreover, version 2 estimates the N2 fixation rate in the Indian Ocean to be 35±14 Tg N yr−1, which could not be estimated using version 1 due to limited data availability. Furthermore, a comparison of N2 fixation rates obtained through different measurement methods at the same months, locations, and depths reveals that the conventional 15N2 bubble method yields lower rates in 69 % cases compared to the new 15N2 dissolution method. This updated version of the database can facilitate future studies in marine ecology and biogeochemistry. The database is stored at the Figshare repository (https://doi.org/10.6084/m9.figshare.21677687; Shao et al., 2022).
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    URL: Article
    DOI: 10.5194/essd-15-3673-2023
    DOI: 10.5194/essd-15-3673-2023-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2475469-9
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  • 3
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    Coupled effect of substrate and light on assimilation and oxidation of regenerated nitrogen in the euphotic ocean
    Wiley ; 2019
    In:  Limnology and Oceanography Vol. 64, No. 3 ( 2019-05), p. 1270-1283
    Details
    In: Limnology and Oceanography, Wiley, Vol. 64, No. 3 ( 2019-05), p. 1270-1283
    Abstract: Nitrogen (N), as a critical element for microbial metabolisms, recycles rapidly in the euphotic ocean. Oxidation by nitrifiers is a competing pathway for phytoplankton assimilation of regenerated N (NH 4 + and urea). Sharing the overlapping substrates may result in competitive exclusion, thus, niche separation for the two assemblages. Both pathways are sensitive to light, but whether light intensity will intensify or alleviate such resource competition in the euphotic zone remains poorly explored in the field at the community level. By using 15 N labeling techniques, paired kinetic responses of uptake and oxidation were conducted in single bottles under manipulated light intensities for both NH 4 + and urea. We found light stimulated the maximum rate ( R m ) and specific affinities ( α U ) of both NH 4 + and urea uptake. In contrast, light effects were opposite for oxidation kinetics ( R m and α O ). As irradiance increased, the rapid increase in α U and concomitant decrease in α O imply a distinctive competition advantage of photosynthetic organisms over oxidizers under substrate‐limited environments. The ratio of α U / α O for NH 4 + ranged from 0.8 to 3089 (5.8–46,788 for urea) showing a distinct increasing pattern as ambient light increases, demonstrating that phytoplankton overwhelms nitrifiers throughout the oligotrophic euphotic zone, driving down concentrations and maintaining short turnover times of the two regenerated N substrates. Moreover, phytoplankton relied equally on NH 4 + and urea; yet, nitrifiers preferred NH 4 + to urea. In the nitrate‐depleted euphotic ocean, light acts as a crucial driver for utilization pathways of regenerated N and vertical niche separation.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v64.3
    DOI: 10.1002/lno.11114
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
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    SSG: 14
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  • 4
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    Changes in isotope fractionation during nitrate assimilation by marine eukaryotic and prokaryotic algae under different pH and CO 2 conditions
    Wiley ; 2024
    In:  Limnology and Oceanography Vol. 69, No. 5 ( 2024-05), p. 1045-1055
    Details
    In: Limnology and Oceanography, Wiley, Vol. 69, No. 5 ( 2024-05), p. 1045-1055
    Abstract: The impact of environmental factors on nitrogen (N) and oxygen (O) isotope effects during algal nitrate assimilation causes uncertainty in the field application of sedimentary N isotope records and nitrate isotopes to understand the marine nitrogen cycle. Ocean acidification is predicted to change nitrogen cycling including nitrate assimilation, but how N and O isotope effects during algal nitrate assimilation vary in response to changes in seawater pH and partial pressure CO 2 ( p CO 2 ) remains unknown. We measured N and O isotope effects during nitrate assimilation and physiological states of the marine diatom Thalassiosira weissflogii and Synechococcus under different pH (8.1 or 7.8) and p CO 2 (400 or 800 μ atm) conditions. Low pH and/or high p CO 2 equally decreased N and O isotope effects during nitrate assimilation by diatoms possibly due to reducing cellular nitrate efflux/uptake ratio and decreased isotope effects for nitrate uptake, whereas they did not affect those by Synechococcus with low intracellular nitrate concentration and limited nitrate efflux. Our results provide compelling experimental evidence showing different changes in N and O isotope effects during nitrate assimilation by marine eukaryotic and prokaryotic phytoplankton at low pH and/or high p CO 2 . These findings suggest new insight into environmental controls on variability in the isotope effect during algal nitrate assimilation, and have implications for improving a predictive understanding of N and O isotope tools in acidified oceans.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v69.5
    DOI: 10.1002/lno.12546
    Language: English
    Publisher: Wiley
    Publication Date: 2024
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    detail.hit.zdb_id: 412737-7
    SSG: 12
    SSG: 14
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  • 5
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    Substrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming
    Springer Science and Business Media LLC ; 2020
    In:  Nature Communications Vol. 11, No. 1 ( 2020-07-14)
    Details
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2020-07-14)
    Abstract: In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry. Here, we show divergent thermal response patterns for marine AO across a wide onshore/offshore trophic gradient. We find ammonia oxidizer community and ambient substrate co-regulate optimum temperatures (T opt ), generating distinct thermal response patterns with T opt varying from ≤14 °C to ≥34 °C. Substrate addition elevates T opt when ambient substrate is unsaturated. The thermal sensitivity of kinetic parameters allows us to predict responses of both AO rate and T opt at varying substrate and temperature below the critical temperature. A warming ocean promotes nearshore AO, while suppressing offshore AO. Our findings reconcile field inconsistencies of temperature effects on AO, suggesting that predictive biogeochemical models need to include such differential warming mechanisms on this key nitrogen cycle process.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/s41467-020-17366-3
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 2553671-0
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  • 6
    Online Resource
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    Ambient nitrate switches the ammonium consumption pathway in the euphotic ocean
    Springer Science and Business Media LLC ; 2018
    In:  Nature Communications Vol. 9, No. 1 ( 2018-03-02)
    Details
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2018-03-02)
    Abstract: Phytoplankton assimilation and microbial oxidation of ammonium are two critical conversion pathways in the marine nitrogen cycle. The underlying regulatory mechanisms of these two competing processes remain unclear. Here we show that ambient nitrate acts as a key variable to bifurcate ammonium flow through assimilation or oxidation, and the depth of the nitracline represents a robust spatial boundary between ammonium assimilators and oxidizers in the stratified ocean. Profiles of ammonium utilization show that phytoplankton assemblages in nitrate-depleted regimes have higher ammonium affinity than nitrifiers. In nitrate replete conditions, by contrast, phytoplankton reduce their ammonium reliance and thus enhance the success of nitrifiers. This finding helps to explain existing discrepancies in the understanding of light inhibition of surface nitrification in the global ocean, and provides further insights into the spatial linkages between oceanic nitrification and new production.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/s41467-018-03363-0
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 2553671-0
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  • 7
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    Upper Ocean Biogeochemistry of the Oligotrophic North Pacific Subtropical Gyre: From Nutrient Sources to Carbon Export
    American Geophysical Union (AGU) ; 2023
    In:  Reviews of Geophysics Vol. 61, No. 3 ( 2023-09)
    Details
    In: Reviews of Geophysics, American Geophysical Union (AGU), Vol. 61, No. 3 ( 2023-09)
    Abstract: Subtropical gyres display larger spatiotemporal dynamics in biogeochemical properties than previously considered An improved two‐layer framework is proposed for the study of nutrient‐driven and biologically mediated carbon export in the euphotic zone Future research will benefit from high‐resolution samplings, improved sensitivity of nutrient analyses, and advanced modeling capabilities
    Type of Medium: Online Resource
    ISSN: 8755-1209 , 1944-9208
    URL: Article
    DOI: 10.1029/2022RG000800
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2023
    detail.hit.zdb_id: 2035391-1
    detail.hit.zdb_id: 209852-0
    SSG: 16,13
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  • 8
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    Nitrogen fixation in two coastal upwelling regions of the Taiwan Strait
    Springer Science and Business Media LLC ; 2017
    In:  Scientific Reports Vol. 7, No. 1 ( 2017-12-14)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 7, No. 1 ( 2017-12-14)
    Abstract: Recent studies have demonstrated that dinitrogen fixation can be important in nutrient-rich coastal upwelling regions. During a cruise to the Taiwan Strait in summer 2015, we found that the nitrogen fixation rate in surface waters ranged from below detection limits to 7.51 nmol N L −1 d −1 . Higher rates accompanied by low N:P ratios (1–10.4:1) associated with low temperatures occurred in the surface water where the Pingtan and the Dongshan upwelling regions met (the NE area). In contrast, insignificant rates were observed in the southwest area of the Dongshan upwelling region (the SW area) with sufficient N and deficient P, and therefore high N:P ratios (e.g., 〉 43 at station C2) due largely to the influence of the Pearl River plume. Diatom-associated symbionts (het-1; 10 4 –10 6 copies L −1 ) that are efficient in organic matter export were found to dominate the other diazotrophic groups that were surveyed, which may represent a direct relationship between new nitrogen input and export in the upwelling regions. Our results suggest a hydrographical influence on the diazotroph community and N 2 fixation in coastal upwelling regions.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-017-18006-5
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2017
    detail.hit.zdb_id: 2615211-3
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  • 9
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    The complex effects of ocean acidification on the prominent N 2 -fixing cyanobacterium Trichodesmium
    American Association for the Advancement of Science (AAAS) ; 2017
    In:  Science Vol. 356, No. 6337 ( 2017-05-05), p. 527-531
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 356, No. 6337 ( 2017-05-05), p. 527-531
    Abstract: Acidification of seawater caused by anthropogenic carbon dioxide (CO 2 ) is anticipated to influence the growth of dinitrogen (N 2 )–fixing phytoplankton, which contribute a large fraction of primary production in the tropical and subtropical ocean. We found that growth and N 2 -fixation of the ubiquitous cyanobacterium Trichodesmium decreased under acidified conditions, notwithstanding a beneficial effect of high CO 2 . Acidification resulted in low cytosolic pH and reduced N 2 -fixation rates despite elevated nitrogenase concentrations. Low cytosolic pH required increased proton pumping across the thylakoid membrane and elevated adenosine triphosphate production. These requirements were not satisfied under field or experimental iron-limiting conditions, which greatly amplified the negative effect of acidification.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.aal2981
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2017
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    SSG: 11
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  • 10
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    Effect of light on N〈sub〉2〈/sub〉 fixation and net nitrogen release of 〈i〉Trichodesmium〈/i〉 in a field study
    Copernicus GmbH ; 2018
    In:  Biogeosciences Vol. 15, No. 1 ( 2018-01-02), p. 1-12
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 15, No. 1 ( 2018-01-02), p. 1-12
    Abstract: Abstract. Dinitrogen fixation (NF) by marine cyanobacteria is an important pathway to replenish the oceanic bioavailable nitrogen inventory. Light is the key to modulating NF; however, field studies investigating the light response curve (NF-I curve) of NF rate and the effect of light on diazotroph-derived nitrogen (DDN) net release are relatively sparse in the literature, hampering prediction using models. A dissolution method was applied using uncontaminated 15N2 gas to examine how the light changes may influence the NF intensity and DDN net release in the oligotrophic ocean. Experiments were conducted at stations with diazotrophs dominated by filamentous cyanobacterium Trichodesmium spp. in the western Pacific and the South China Sea. The effect of light on carbon fixation (CF) was measured in parallel using the 13C tracer method specifically for a station characterized by Trichodesmium bloom. Both NF-I and CF-I curves showed a Ik (light saturation coefficient) range of 193 to 315 µE m−2 s−1, with light saturation at around 400 µE m−2 s−1. The proportion of DDN net release ranged from ∼ 6 to ∼ 50 %, suggesting an increasing trend as the light intensity decreased. At the Trichodesmium bloom station, we found that the CF ∕ NF ratio was light-dependent and the ratio started to increase as light was lower than the carbon compensation point of 200 µE m−2 s−1. Under low-light stress, Trichodesmium physiologically preferred to allocate more energy for CF to alleviate the intensive carbon consumption by respiration; thus, there is a metabolism tradeoff between CF and NF pathways. Results showed that short-term (〈 24 h) light change modulates the physiological state, which subsequently determined the C ∕ N metabolism and DDN net release by Trichodesmium. Reallocation of energy associated with the variation in light intensity would be helpful for prediction of the global biogeochemical cycle of N by models involving Trichodesmium blooms.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-15-1-2018
    DOI: 10.5194/bg-15-1-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2158181-2
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