Seasonal variations of unicellular diazotroph groups A and B, and Trichodesmium in the northern South China Sea and neighboring upstream Kuroshio Current

Shiozaki, Takuhei; Chen, Yuh-ling Lee; Lin, Yen-Huei; Taniuchi, Yukiko; Sheu, Der-Shyan; Furuya, Ken; Chen, Houng-Yung

doi:10.1016/j.csr.2014.02.015

Cited by 43 publications

(47 citation statements)

References 43 publications

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“…The absolute depth‐integrated abundances of UCYN‐A1, UCYN‐A2, UCYN‐B, and γ‐24774A11 revealed no significant difference between the NSCS region and KI‐affected region (Table ). In contrast, Shiozaki, Lee Chen, et al () found orders of magnitude higher of UCYN‐B abundance in the main stream of Kuroshio in summer than that in NSCS. During our cruise, we did not investigate the stations in the main stream Kuroshio.…”

Section: Discussionmentioning

confidence: 85%

Biogeography of N₂ Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

et al. 2019

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The N2 fixation and primary production rates were measured simultaneously using 15N2 and 13C incubation assays in the northern South China Sea influenced by the Kuroshio intrusion (KI) seasonally. The degree of KI (KI index, range from 0 to 1) was assessed by applying an isopycnal mixing model. The water column integrated N2 fixation and primary production for stations with KI index larger than 0.5 were 463 ± 260 μmol N·m−2·day−1 and 62 ± 19 mmol C·m−2·day−1, respectively, significantly higher than those for stations with KI index lower than 0.5 (50 ± 10 μmol N·m−2·day−1 and 28 ± 10 mmol C·m−2·day−1, respectively). Trichodesmium was the dominant diazotroph at stations with KI index larger than 0.5, with 2 orders of magnitude higher nifH gene abundance than that at stations with KI index lower than 0.5. However, the highest N2 fixation rates were found in waters with moderate KI index around 0.6, suggesting that frontal zone mixing might stimulate N2 fixation. Our results demonstrated that diazotrophs (mainly Trichodesmium) were tightly associated with the KI, which modulated the biogeographic distribution of N2 fixers. In summary, we found the transportation of Trichodesmium by KI, then, we quantified the fraction of KI and N2 fixation rates in the northern South China Sea. The results suggested that KI generated a new biogeographic regime which could significantly influence the carbon and nitrogen cycles far away from the main stream.

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Section: Discussionmentioning

confidence: 85%

Biogeography of N₂ Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

et al. 2019

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“…Seawater samples (2 L) for DNA analyses were collected onto Sterivex‐GP pressure filter units with a 0.22‐ μ m pore size (Millipore, Billerica, Massachusetts, U.S.A.) and stored at −80°C until onshore analysis. Total DNA was extracted using a ChargeSwitch Forensic DNA Purification Kit (Invitrogen, Carlsbad, California, U.S.A.), following the manufacturer's instructions (Shiozaki et al ). The DNA concentration was determined using a NanoDrop spectrophotometer (NanoDrop Technologies, Wilmington, Delaware, U.S.A.).…”

Section: Samples and Methodsmentioning

confidence: 99%

“…The DNA concentration was determined using a NanoDrop spectrophotometer (NanoDrop Technologies, Wilmington, Delaware, U.S.A.). Fragments of the nifH genes were amplified by nested PCR (Zehr and Turner ) as previously described (Bentzon‐Tilia et al 2015; Shiozaki et al ), with some modifications. The samples were selected from stations at which the nitrogen fixation rate was detected.…”

Section: Samples and Methodsmentioning

confidence: 99%

Diazotroph community structure and the role of nitrogen fixation in the nitrogen cycle in the Chukchi Sea (western Arctic Ocean)

Shiozaki

Fujiwara

Ijichi

et al. 2018

Limnology & Oceanography

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Marine nitrogen fixation occurs not only in subtropical and tropical regions but also in colder regions. However, the distribution of diazotrophs, nitrogen fixation rate, and its contribution to the nitrogen cycle in the Arctic Ocean remain poorly understood. We examined the diazotroph community structure and activity in the shelf and off‐shelf regions of the Chukchi Sea, western Arctic Ocean, during late summer 2015. The nitrate and ammonium assimilation rates were determined simultaneously to gain insights into the role of nitrogen fixation in the nitrogen cycle of the region. The diazotroph community determined by Illumina sequencing was mainly composed of Cluster III nifH phylotypes (putative anaerobes), accounting for > 80% of the total sequences examined, except for one surface sample. This result is strikingly different from previous findings in other oceanic regions. The nifH sequences other than those from Cluster III were mostly affiliated with UCYN‐A2 (symbiotic cyanobacteria), which accounted for < 15% of the total sequences. UCYN‐A2 tended to be abundant (maximum 2.9 × 103 copies L−1) in the high‐temperature low‐salinity water mass that is characteristic of Pacific‐originating water. Nitrogen fixation rate was detectable at most stations, with a range of 0.08–3.60 nmol L−1 d−1, displaying no clear relationship with depth (light intensity) or nitrate or ammonium concentration. Nitrogen fixation locally exceeded nitrate assimilation, but accounted for 1.00% at most in the total nitrogen assimilation in the euphotic zone.

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“…We used previously designed primer and probe sets (Table S1; Foster et al, 2007;Langlois et al, 2008;Moisander et al, 2010;Shiozaki, Chen, et al, 2014) in a LightCycler 480 System (Roche Applied Science, Germany) as described elsewhere (Shiozaki et al, 2015). Seven nifH phylotypes, which were considered to be the major diazotrophs in these tropical and subtropical oligotrophic waters, were quantified by qPCR: Trichodesmium, Crocosphaera, UCYN-A1, UCYN-C, Richelia associated with Rhizosolenia (RR) or Hemiaulus (HR), and a gammaproteobacterium (γ-24774A11).…”

Section: Quantitative Polymerase Chain Reactionmentioning

confidence: 99%

Linkage Between Dinitrogen Fixation and Primary Production in the Oligotrophic South Pacific Ocean

Shiozaki

Bombar

Riemann

et al. 2018

Global Biogeochemical Cycles

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The import of nitrogen via dinitrogen fixation supports primary production, particularly in the oligotrophic ocean; however, to what extent dinitrogen fixation influences primary production, and the role of specific types of diazotrophs, remains poorly understood. We examined the relationship between primary production and dinitrogen fixation together with diazotroph community structure in the oligotrophic western and eastern South Pacific Ocean and found that dinitrogen fixation was higher than nitrate‐based new production. Primary production increased in the middle of the western subtropical region, where the cyanobacterium Trichodesmium dominated the diazotroph community and accounted for up to 7.8% of the phytoplankton community, and the abundance of other phytoplankton taxa (especially Prochlorococcus) was high. These results suggest that regenerated production was enhanced by nitrogen released from Trichodesmium and that carbon fixation by Trichodesmium also contributed significantly to total primary production. Although volumetric dinitrogen fixation was comparable between the western and eastern subtropical regions, primary production in the western waters was more than twice as high as that in the eastern waters, where UCYN‐A1 (photoheterotroph) and heterotrophic bacteria were the dominant diazotrophs. This suggests that dinitrogen fixed by these diazotrophs contributed relatively little to primary production of the wider community, and there was limited carbon fixation by these diazotrophs. Hence, we document how the community composition of diazotrophs in the field can be reflected in how much nitrogen becomes available to the wider phytoplankton community and in how much autotrophic diazotrophs themselves fix carbon and thereby influences the magnitude of local primary production.

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Seasonal variations of unicellular diazotroph groups A and B, and Trichodesmium in the northern South China Sea and neighboring upstream Kuroshio Current

Cited by 43 publications

References 43 publications

Biogeography of N₂ Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

Biogeography of N₂ Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

Diazotroph community structure and the role of nitrogen fixation in the nitrogen cycle in the Chukchi Sea (western Arctic Ocean)

Linkage Between Dinitrogen Fixation and Primary Production in the Oligotrophic South Pacific Ocean

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Seasonal variations of unicellular diazotroph groups A and B, and Trichodesmium in the northern South China Sea and neighboring upstream Kuroshio Current

Cited by 43 publications

References 43 publications

Biogeography of N2 Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

Biogeography of N2 Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

Diazotroph community structure and the role of nitrogen fixation in the nitrogen cycle in the Chukchi Sea (western Arctic Ocean)

Linkage Between Dinitrogen Fixation and Primary Production in the Oligotrophic South Pacific Ocean

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Biogeography of N₂ Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea

Biogeography of N₂ Fixation Influenced by the Western Boundary Current Intrusion in the South China Sea