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198 results on '"Ho, Tung‐Yuan"'

36. Sectional Distribution Patterns of Cd, Ni, Zn, and Cu in the North Pacific Ocean: Relationships to Nutrients and Importance of Scavenging

Author

Zheng, Linjie, Minami, Tomoharu, Takano, Shotaro, Ho, Tung‐Yuan, and Sohrin, Yoshiki

Subjects
nickel, cadmium, copper, zinc, the North Pacific Ocean, seawater
Abstract

The North Pacific Ocean is located at the end of the thermohaline circulation of deep water. This study reports on basin-scale full-depth sectional distributions of total dissolvable (td), dissolved (d), and labile particulate (lp) Cd, Ni, Zn, and Cu along three transects: the GEOTRACES transects GP18 (165°E) and GP02 (47°N), and along 160°W. We find that scavenging is an important factor that significantly affects the distributions of dZn, dNi, and dCu, of which the magnitude of influence increases in the order of Cd < Ni, Zn < Cu. The relationships between the four dissolved metals with Si(OH)₄ and PO₄ differed considerably from those in other oceans. The spot concentration ratio of dCd/PO₄ was 0.34 ± 0.02 nmol/μmol (n = 296) in waters >800 m deep, which is in the range of the phytoplankton Cd/P ratio. This is indicative of the dominant effect of water circulation and biological processes on dCd distribution. The dissolved metals (dMs) to PO₄ ratios of other examined metals were either partially or completely outside the range of typical biomass ratios. They generally increased with depth in waters >800 m deep; the magnitude of increase was the highest for Cu and moderate for Ni and Zn. Below 800 m, an increase in the apparent oxygen utilization from 150 to 300 μmol/kg was concurrent with a decrease in the dMs/PO4 ratios: 4 ± 3% for Cd, 21 ± 4% for Zn, 21 ± 3% for Ni, and 69 ± 7% for Cu.

Published
2021

40. The effects of Ni availability on H2 production and N2 fixation in a model unicellular diazotroph: The expression of hydrogenase and nitrogenase.

Author

Li, Hsin‐Ting, Tuo, Sing‐How, Lu, Mei‐Chen, and Ho, Tung‐Yuan

Subjects
NITROGENASES, HYDROGENASE, EUPHOTIC zone, H2 control, NITROGEN, OCEAN
Abstract

We investigated the effects of Ni concentration on hydrogen (H2) net production and nitrogen (N2) fixation rates in a model unicellular diazotrophic cyanobacterium, Cyanothece. We quantified NiFe uptake hydrogenase of the diazotroph to examine how Ni deficiency affects the expression of hydrogenase and nitrogenase and N2 fixation rates. We found that Ni availability controls its H2 net production and the expression of HupL, the major subunit of the uptake hydrogenase. Low Ni availability induced low HupL expression levels while yielding high H2 net production, and vice versa. We also identified the threshold range of Ni concentrations that may differentiate low and high H2 net production patterns in the diazotroph. However, the substantial variations in Ni availability and H2 net production did not affect nitrogenase expression and N2 fixation rates in Cyanothece. From two independent studies in the Atlantic tropical and subtropical oceans, we found that dissolved Ni concentrations and H2 oversaturation percentage exhibited a statistically significant negative correlation, which is consistent with the findings of this culture study. Overall, these results indicate that Ni availability may affect H2 net production and concentrations in the euphotic zone of the oceanic regions. H2 concentrations may be used as a promising proxy to reflect N2 fixation activities in tropical and subtropical oceans only under Ni‐deficient conditions. [ABSTRACT FROM AUTHOR]

Published
2022
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42. The evolutionary inheritance of elemental stoichiometry in marine phytoplankton

Author

Quigg, Antonietta, Finkel, Zoe V., Irwin, Andrew J., Rosenthal, Yair, Ho, Tung-Yuan, Reinfelder, John R., Schofield, Oscar, Morel, Francois M. M., and Falkowski, Paul G.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): Antonietta Quigg (corresponding author) [1]; Zoe V. Finkel [1]; Andrew J. Irwin [1]; Yair Rosenthal [1, 2]; Tung-Yuan Ho [5]; John R. Reinfelder [3]; Oscar Schofield [1, 4]; Francois [...]

Published
2003
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47. The effects of Ni availability on H2production and N2fixation in a model unicellular diazotroph: The expression of hydrogenase and nitrogenase

Author

Li, Hsin‐Ting, Tuo, Sing‐How, Lu, Mei‐Chen, and Ho, Tung‐Yuan

Abstract

We investigated the effects of Ni concentration on hydrogen (H2) net production and nitrogen (N2) fixation rates in a model unicellular diazotrophic cyanobacterium, Cyanothece. We quantified NiFe uptake hydrogenase of the diazotroph to examine how Ni deficiency affects the expression of hydrogenase and nitrogenase and N2fixation rates. We found that Ni availability controls its H2net production and the expression of HupL, the major subunit of the uptake hydrogenase. Low Ni availability induced low HupL expression levels while yielding high H2net production, and vice versa. We also identified the threshold range of Ni concentrations that may differentiate low and high H2net production patterns in the diazotroph. However, the substantial variations in Ni availability and H2net production did not affect nitrogenase expression and N2fixation rates in Cyanothece. From two independent studies in the Atlantic tropical and subtropical oceans, we found that dissolved Ni concentrations and H2oversaturation percentage exhibited a statistically significant negative correlation, which is consistent with the findings of this culture study. Overall, these results indicate that Ni availability may affect H2net production and concentrations in the euphotic zone of the oceanic regions. H2concentrations may be used as a promising proxy to reflect N2fixation activities in tropical and subtropical oceans only under Ni‐deficient conditions.

Published
2022
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