Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

Tseng, Yu Fang; Lin, Jun; Dai, Minhan; Kao, Shuh Ji

doi:10.5194/bg-11-409-2014

Cited by 78 publications

(62 citation statements)

References 55 publications

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“…In total, 12 stations were monitored in this study. A turbidity front appeared at the salinity of ∼ 22 (see Tseng et al, 2014, for spatial distribution of TSM), and the distinctive correlations between TSM and the nitrification rate of those stations support our zonal classification (see below). Meanwhile, from the temperature distribution (see Tseng et al, this issue) we know that the upwelling had occurred and outcropped at the seaward side of the turbidity front.…”

Section: Samplingsupporting

confidence: 77%

Nitrification and its oxygen consumption along the turbid Chang Jiang River plume

et al. 2014

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Abstract. Nitrification is a series of processes that oxidizes ammonia to nitrate, which contributes to hypoxia development in coastal oceans, especially in eutrophicated regions. The nitrification rate of bulk water (NR b ) and particle free water (NR pf , particle > 3 µm eliminated) were determined along the Chang Jiang River plume in August 2011 by nitrogen isotope tracer technique. Measurements of dissolved oxygen (DO), community respiration rate (CR), nutrients, dissolved organic nitrogen (DON), total suspended matter (TSM), particulate organic carbon/nitrogen (POC / PON), acid-leachable iron and manganese on suspended particles and both archaeal and β-proteobacterial ammonia monooxygenase subunit A gene (amoA) abundance on size-fractioned particles (> 3 µm and 0.22-3 µm) were conducted. The NR b ranged from undetectable up to 4.6 µmol L −1 day −1 , peaking at a salinity of ∼ 29. NR b values were positively correlated with ammonium concentration, suggesting the importance of substrate in nitrification. In the river mouth and the inner plume, NR b was much higher than NR pf , indicating that the nitrifying microorganism is mainly particle associated, which was supported by its significant correlation with amoA gene abundance and TSM concentration. The estimated oxygen demands of nitrification accounted for 0.32 to 318 % of CR, in which 50 % samples demanded more oxygen than that predicted by by the Redfield model (23 %), indicating that oxygen might not be the sole oxidant though DO was sufficient (> 58 µmol kg −1 ) throughout the observation period. The excess nitrification-associated oxygen demand (NOD) showed a tendency to occur at lower DO samples accompanied by higher acid-leachable Fe / Mn, which implied reactive Fe 3+ / Mn 4+ may play a role as oxidant in the nitrification process. Stoichiometric calculation suggested that reactive Fe on particles was 10 times the oxidant demand required to complete ammonia oxidation in the entire plume. The potential involvement of reactive iron and manganese in the nitrification process in oxygenated water further complicated nitrogen cycling in the turbid river plume.

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Section: Samplingsupporting

confidence: 77%

Nitrification and its oxygen consumption along the turbid Chang Jiang River plume

et al. 2014

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“…5). This result would seem to oppose the idea that CDW is the main driver stimulating primary production in the nECS as has been previously suggested (Chou et al 2013;Tseng et al 2014).…”

Section: Magnitude Of Remineralized Phosphatecontrasting

confidence: 64%

Estimating Remineralized Phosphate and Its Remineralization Rate in the Northern East China Sea During Summer 1997: A Snapshot Study Before Three-Gorges Dam Construction

Kim¹,

Kim²,

Macdonald³

et al. 2016

Terr. Atmos. Ocean. Sci.

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The northern East China Sea (a.k.a., "The South Sea") is a dynamic zone that exerts a variety of effects on the marine ecosystem due to Three-Gorges Dam construction. As the northern East China Sea region is vulnerable to climate forcing and anthropogenic impacts, it is important to investigate how the remineralization rate in the northern East China Sea has changed in response to such external forcing. We used an historical hydrographic dataset from August 1997 to obtain a baseline for future comparison. We estimate the amount of remineralized phosphate by decomposing the physical mixing and biogeochemical process effect using water column measurements (temperature, salinity, and phosphate). The estimated remineralized phosphate column inventory ranged from 0.8 to 42.4 mmol P m -2 (mean value of 15.2 ± 12.0 mmol P m -2 ). Our results suggest that the Tsushima Warm Current was a strong contributor to primary production during the summer of 1997 in the study area. The estimated summer (June -August) remineralization rate in the region before Three-Gorges Dam construction was 18 ± 14 mmol C m -2 d -1 .

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“…However, NO 3 − assimilation by phytoplankton should be limited by the high turbidity in Zone 1 (Figure c) although we cannot completely exclude this possibility since fluorescence was detectable. Yet from the investigation in the same cruise, both chlorophyll and APA were reported to be allochthonous (Tseng et al, ). Moreover, the DO concentrations (2.9–6.2 mg/L, Figure d) were sufficient to inhibit denitrification in the water column (Codispoti et al, ), supported by the undetectable denitrification rates within 24 h incubation (Text S4).…”

Section: Resultsmentioning

confidence: 97%

Dual Isotope Measurements Reveal Zoning of Nitrate Processing in the Summer Changjiang (Yangtze) River Plume

Yan

Wan

et al. 2017

Geophysical Research Letters

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Riverine nitrogen input into the coastal zone has increased remarkably in recent decades. Yet its transformation and recycling within hydrodynamically active regions remains unclear. Using observations of nitrate concentration and dual isotopic composition across the Changjiang River plume within a three end-member mixing model, we found deviations between the observed and expected values for mixing alone, revealing the nonconservative behavior of nitrate. Using cross correlations between concentrations and dual isotope deviations, we identified three nitrogen transformation zones, which correspond to separate portions of the plume. Nitrification and sedimentary denitrification occurred near the river mouth, nitrification prevailed further offshore under the plume, and finally, phytoplankton assimilation occurred in the outer surface plume (>100 km offshore), where it was fueled by nitrate that had already been strongly modified by microbial processes. Information was assembled into a conceptual model offering an overview of nitrogen transformations in a large river plume.

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Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

Abstract: Abstract. The Changjiang (Yangtze) River discharges vast amount of unbalanced nutrients (dissolved inorganic nitrogen and phosphorus with N / P ratio > 80 in general) into the East China Sea in summer.

Cited by 78 publications

References 55 publications

Nitrification and its oxygen consumption along the turbid Chang Jiang River plume

Nitrification and its oxygen consumption along the turbid Chang Jiang River plume

Estimating Remineralized Phosphate and Its Remineralization Rate in the Northern East China Sea During Summer 1997: A Snapshot Study Before Three-Gorges Dam Construction

Dual Isotope Measurements Reveal Zoning of Nitrate Processing in the Summer Changjiang (Yangtze) River Plume

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