Effect of light on N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; fixation and net nitrogen release of &amp;lt;i&amp;gt;Trichodesmium&amp;lt;/i&amp;gt; in a field study

Lü, Yangyang; Wen, Zuozhu; Shi, Dalin; Chen, Mingming; Zhang, Yao; Bonnet, Sophie; Li, Yuhang; Tian, Jiwei; Kao, Shuh‐Ji

doi:10.5194/bg-15-1-2018

Cited by 31 publications

(39 citation statements)

References 67 publications

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“…By the end of August, the AWD shifted to a significant CO 2 source of about 0.7 mol C m −2 (Table 1). Accounting for the study period between January and August, this results in an ocean net annual CO 2 sink between 4 and 8 mmol m −2 d −1 , which are similar to the results by Yasunaka et al (2018). The winter-tosummer ocean CO 2 uptake estimates of 3.7 mol C m −2 (44 g C m −2 ) by Fransson et al (2001) in the Barents Sea in the upper 50 m, are nearly twice as large as our maximum estimate of 2.1 mol C m −2 (25 g C m −2 ).…”

Section: Monthsupporting

confidence: 86%

“…The Oceanic Sink of Atmospheric CO 2 in Fram Strait Area and Its Variability Several studies estimating the air-sea CO 2 fluxes and the annual net CO 2 sink show that the Arctic Ocean, the Fram Strait and waters around Svalbard act as atmospheric CO 2 sinks (e.g., Tynan et al, 2016;Yasunaka et al, 2016Yasunaka et al, , 2018Fransson et al, 2017). The 18-year annual average of observed seawater f CO 2 and a self-organizing mapping technique showed that the Arctic Ocean acted as an ocean CO 2 sink between 8 and 12 mmol m −2 d −1 and a daily mean in a full annual cycle of 5 mmol m −2 d −1 (Yasunaka et al, 2018). In our estimates, the study area showed a small oceanic CO 2 sink until May at an average of 0.12 ± 0.06 mol C m −2 for the period January to May.…”

Section: Monthmentioning

confidence: 99%

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Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean

et al. 2019

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The eastern Fram Strait and area north of Svalbard, are influenced by the inflow of warm Atlantic water, which is high in nutrients and CO 2 , influencing the carbon flux into the Arctic Ocean. However, these estimates are mainly based on summer data and there is still doubt on the size of the net ocean Arctic CO 2 sink. We use data on carbonate chemistry and nutrients from three cruises in 2014 in the CarbonBridge project (January, May, and August) and one in Fram Strait (August). We describe the seasonal variability and the major drivers explaining the inorganic carbon change (C DIC ) in the upper 50 m, such as photosynthesis (C BIO ), and air-sea CO 2 exchange (C EXCH ). Remotely sensed data describes the evolution of the bloom and net community production. The focus area encompasses the meltwater-influenced domain (MWD) along the ice edge, the Atlantic water inflow (AWD), and the West Spitsbergen shelf (SD). The C BIO total was 2.2 mol C m −2 in the MWD derived from the nitrate consumption between January and May. Between January and August, the C BIO was 3.0 mol C m −2 in the AWD, thus C BIO between May and August was 0.8 mol C m −2 . The ocean in our study area mainly acted as a CO 2 sink throughout the period. The mean CO 2 sink varied between 0.1 and 2.1 mol C m −2 in the AWD in August. By the end of August, the AWD acted as a CO 2 source of 0.7 mol C m −2 , attributed to vertical mixing of CO 2 -rich waters and contribution from respiratory CO 2 as net community production declined. The oceanic CO 2 uptake (C EXCH ) from the atmosphere had an impact on C DIC between 5 and 36%, which is of similar magnitude as the impact of the calcium carbonate (CaCO 3 , C CALC ) dissolution of 6-18%. C CALC was attributed to be caused by a combination of the sea-ice ikaite dissolution and dissolution of advected CaCO 3 shells from the south. Indications of denitrification were observed, associated with sea-ice meltwater and bottom shelf processes. C BIO played a major role (48-89%) for the impact on C DIC .

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Section: Monthsupporting

confidence: 86%

Section: Monthmentioning

confidence: 99%

Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean

et al. 2019

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“…The NFRs were measured using the dissolution method (Mohr et al ; Lu et al ) to avoid the problems of bubble dissolution. 15 N 2 gas (98.9%) from Cambridge Isotope Laboratories was used, and a blank was checked for contamination of bioavailable non‐N 2 15 N, as described in Dabundo et al ().…”

Section: Methodsmentioning

confidence: 99%

Biogeographic drivers of diazotrophs in the western Pacific Ocean

Chen

Lü

Jiao

et al. 2019

Limnology & Oceanography

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The global budget of marine nitrogen (N) is not balanced, with N removal largely exceeding N fixation. One of the major causes of this imbalance is our inadequate understanding of the diversity and distribution of marine N 2 fixers (diazotrophs) as well as their contribution to N 2 fixation. Here, we performed a large-scale cross-system study spanning the South China Sea, Luzon Strait, Philippine Sea, and western tropical Pacific Ocean to compare the biogeography of seven major diazotrophic groups and N 2 fixation rates in these ecosystems. Distinct spatial niche differentiation was observed. Trichodesmium was dominant in the South China Sea and western equatorial Pacific, whereas the unicellular cyanobacterium UCYN-B dominated in the Philippine Sea. Furthermore, contrasting diel patterns of Trichodesmium nifH genes and UCYN-B nifH gene transcript activity were observed. The heterotrophic diazotroph Gamma A phylotype was widespread throughout the western Pacific Ocean and occupied an ecological niche that overlapped with that of UCYN-B. Moreover, Gamma A (or other possible unknown/undetected diazotrophs) rather than Trichodesmium and UCYN-B may have been responsible for the high N 2 fixation rates in some samples. Regional biogeochemistry analyses revealed crosssystem variations in N 2 -fixing community composition and activity constrained by sea surface temperature, aerosol optical thickness, current velocity, mixed-layer depth, and chlorophyll a concentration. These factors except for temperature essentially control/reflected iron supply/bioavailability and thus drive diazotroph biogeography. This study highlights biogeographical controls on marine N 2 fixers and increases our understanding of global diazotroph biogeography.

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“…The different vertical distribution of Trichodesmium and Richelia/Calothrix is attributable to different ecological niches for adapting light and nutrients (e.g., P, Si, and Fe). Laboratory and field culture experiments showed that Richelia/Calothrix (Foster et al, 2010;Villareal, 1990) seem more tolerant to low light than Trichodesmium (Breitbarth et al, 2008;LaRoche & Breitbarth, 2005;Lu et al, 2018) in deeper water column.…”

Section: Journal Of Geophysical Research: Oceansmentioning

confidence: 97%

Kuroshio Shape Composition and Distribution of Filamentous Diazotrophs in the East China Sea and Southern Yellow Sea

et al. 2019

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The filamentous Trichodesmium and Richelia/Calothrix appear to be crucial N 2 -fixing cyanobacteria throughout the warm oligotrophic ocean, particularly in western boundary currents. The Kuroshio, the hotspot of N 2 fixation in the Pacific Ocean, intrudes into the East China Sea (ECS) and southern Yellow Sea (SYS), which may profoundly influence composition and distribution of filamentous diazotrophs. We provide high spatial resolution dataset of filamentous diazotrophs in the ECS and SYS in July and August 2013. Results showed that Trichodesmium colonies and Richelia/Calothrix were strictly restricted to warm, saline, nitrogen-limited waters of the ECS influenced by Kuroshio and were not detected in the SYS. The density of Trichodesmium in the ECS and SYS was 8.48 × 10 6 trichomes/m 2 , and colonial trichomes accounted for 40%. In addition to free filaments, Richelia/Calothrix were found to be symbiotic with diatoms Hemiaulus, Rhizosolenia/Guinardia, Chaetoceros, and Bacteriastrum with a total density at 2.13 × 10 6 heterocysts/m 2 in the ECS. The densities of filamentous diazotrophs were significantly higher in high-salinity region of the ECS (mainly controlled by Kuroshio) than in low-salinity region of the ECS and in the SYS. The densities of Trichodesmium and Richelia/Calothrix were significantly and positively correlated with temperature, salinity, and mixed-layer depth but were negatively correlated with NO 3 , turbidity, and chlorophyll-a. These results suggested that composition and distribution of filamentous diazotrophs in the ECS and SYS were largely shaped by Kuroshio and associated physicochemical properties. We hypothesize that active N 2 fixation in Kuroshio may be substantially supported by Richelia/Calothrix in addition to Trichodesmium.

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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

Cited by 31 publications

References 67 publications

Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean

Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean

Biogeographic drivers of diazotrophs in the western Pacific Ocean

Kuroshio Shape Composition and Distribution of Filamentous Diazotrophs in the East China Sea and Southern Yellow Sea

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