scholarly journals Responses of lower trophic-level organisms to typhoon passage on the outer shelf of the East China Sea: an incubation experiment

2013 ◽  
Vol 10 (4) ◽  
pp. 6605-6635 ◽  
Author(s):  
N. Yasuki ◽  
K. Suzuki ◽  
A. Tsuda
Keyword(s):  
Water Column ◽  
East China Sea ◽  
Trophic Level ◽  
Outer Shelf ◽  
East China ◽  
Strong Wind ◽  
The East China Sea ◽  
Phytoplankton Productivity ◽  
China Sea ◽  
Lower Trophic Level

Abstract. Typhoons can induce vertical mixing, upwelling, or both in the water column due to strong wind stress. These events can induce phytoplankton blooms in the oligotrophic ocean after typhoon passage. However, little is known about the responses of lower trophic-level organisms or changes in the community structure following the passage of typhoons, particularly in offshore regions. Therefore, we evaluated community succession on the outer shelf of the East China Sea through on-deck bottle incubation experiments simulating hydrographic conditions after the passage of a typhoon. Under all of the experimental conditions we tested, chlorophyll a concentrations increased more than 9-fold within 6 days, and these algal cells were mainly composed of large diatoms (>10 μm). Ciliates also increased along with the diatom bloom. These results suggest that increases in diatom and ciliate populations may enhance biogenic carbon export in the water column. Typhoons can affect not only phytoplankton productivity, but also the composition of lower trophic-level organisms and biogeochemical processes in oligotrophic offshore regions.

scholarly journals Comparison of buried sand ridges and regressive sand ridges on the outer shelf of the East China Sea

2016 ◽  
Vol 38 (1-2) ◽  
pp. 187-198 ◽  
Author(s):  
Ziyin Wu ◽  
Xianglong Jin ◽  
Jieqiong Zhou ◽  
Dineng Zhao ◽  
Jihong Shang ◽  
...  
Keyword(s):  
East China Sea ◽  
Outer Shelf ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
Sand Ridges

Characteristics of outer shelf water in the East China Sea

2013 ◽  
Vol 69 (2) ◽  
pp. 245-258 ◽  
Author(s):  
Shigefumi Yanao ◽  
Takeshi Matsuno
Keyword(s):  
East China Sea ◽  
Outer Shelf ◽  
East China ◽  
Shelf Water ◽  
The East China Sea ◽  
China Sea

scholarly journals Retrieving monthly and interannual pH<sub>T</sub> on the East China Sea shelf using an artificial neural network: ANN-pH<sub>T</sub>-v1

2019 ◽  
Author(s):  
Xiaoshuang Li ◽  
Richard Bellerby ◽  
Jianzhong Ge ◽  
Philip Wallhead ◽  
Jing Liu ◽  
...  
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Water Column ◽  
East China Sea ◽  
East China ◽  
Ann Model ◽  
The East China Sea ◽  
China Sea ◽  
Artificial Neural ◽  
Artificial Neural Network Ann

Abstract. While our understanding of pH dynamics has strongly progressed for open ocean regions, for marginal seas such as the East China Sea (ECS) progress has been constrained by limited observations and complex interactions between biological, physical, and chemical processes. Seawater pH is a very valuable oceanographic variable but not always measured using high quality instrumentation and according to standard practices. In order to predict water column total scale pH (pHT) and enhance our understanding of the seasonal variability of pHT on the ECS shelf, an artificial neural network (ANN) model was developed using 11 cruise datasets from 2013 to 2017 with coincident observations of pHT, temperature (T), salinity (S), dissolved oxygen (DO), nitrate (N), phosphate (P) and silicate (Si) together with sampling position and time. The reliability of the ANN model was evaluated using independent observations from 3 cruises in 2018, and showed a root mean square error accuracy of 0.04. A weight analysis of the ANN model variables suggested that DO, S, T were the most important predictor variables. Monthly water column pHT for the period 2000-2016 was retrieved using T, S, DO, N, P, and Si from the Changjiang Biology Finite-Volume Coastal Ocean Model (FVCOM).

scholarly journals Anaerobic ammonium oxidation, denitrification and dissimilatory nitrate reduction to ammonium in the East China Sea sediment

2013 ◽  
Vol 10 (3) ◽  
pp. 4671-4710 ◽  
Author(s):  
G. D. Song ◽  
S. M. Liu ◽  
H. Marchant ◽  
M. M. M. Kuypers ◽  
G. Lavik
Keyword(s):  
East China Sea ◽  
Nitrate Reduction ◽  
Nitrogen Transformation ◽  
Outer Shelf ◽  
East China ◽  
The East China Sea ◽  
N Loss ◽  
High Background ◽  
China Sea ◽  
Dissimilatory Nitrate Reduction

Abstract. Benthic nitrogen transformation pathways were investigated in the sediment of the East China Sea in June of 2010 using the 15N isotope pairing technique. Slurry incubations indicated that denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) as well as nitrate release by nitrate storing organisms occurred in the East China Sea sediments. These four processes did not exist independently, the nitrate release therefore diluted the 15N labeling fraction of NO3−, a part of the 15NH4&amp;plus; derived from DNRA also formed 30N2 via anammox. Therefore current methods of rate calculations led to over and underestimations of anammox and denitrification respectively. Following the procedure outlined in Thampdrup and Dalsgaard (2002), denitrification rates were slightly underestimated by on average 6% without regard to the effect of nitrate release, while this underestimation could be counteracted by the presence of DNRA. On the contrary, anammox rates calculated from 15NO3− experiment were significantly overestimated by 42% without considering nitrate release. In our study this overestimation could only be compensated 14% by taking DNRA into consideration. In a parallel experiment amended with 15NH4&amp;plus; &amp;plus; 14NO3−, anammox rates were not significantly influenced by DNRA due to the high background of 15NH4&amp;plus; addition. Excluding measurements in which bioirrigation was present, integrated denitrification rates decreased from 10 to 4 mmol N m−2 d−1 with water depth, while integrated anammox rates increased from 1.5 to 4.0 mmol N m−2 d−1. Consequently, the relative contribution of anammox to the total N-loss increased from 13% at the shallowest site near the Changjiang estuary to 50% at the deepest site on the outer shelf. This study represents the first time in which anammox has been demonstrated to play a significant role in benthic nitrogen cycling in the East China Sea sediment, especially on the outer shelf. N-loss as N2 was the main pathway, while DNRA was also an important pathway accounting for 20–31% of benthic nitrogen transformation in the East China Sea. Our study demonstrates the complicated interactions among different benthic nitrogen transformations and the importance of considering denitrification, DNRA, anammox and nitrate release together when designing and interpreting future studies.

Late Quaternary sedimentary evolution of the outer shelf of the East China Sea

2018 ◽  
Vol 493 ◽  
pp. 59-69 ◽  
Author(s):  
Taoyu Xu ◽  
Xuefa Shi ◽  
Shengfa Liu ◽  
Shuqing Qiao ◽  
Zhengquan Yao ◽  
...  
Keyword(s):  
East China Sea ◽  
Late Quaternary ◽  
Outer Shelf ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
Sedimentary Evolution

scholarly journals Carbonate mineral saturation states in the East China Sea: present conditions and future scenario

2013 ◽  
Vol 10 (3) ◽  
pp. 5555-5590 ◽  
Author(s):  
W.-C. Chou ◽  
G.-C. Gong ◽  
C.-C. Hung ◽  
Y.-H. Wu
Keyword(s):  
Water Column ◽  
East China Sea ◽  
Bottom Water ◽  
Atmospheric Co2 ◽  
Total Alkalinity ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
Plume Area ◽  
Bottom Waters

Abstract. To assess the impact of rising atmospheric CO2 and eutrophication on the carbonate chemistry of the East China Sea shelf waters, saturation states (Ω) for two important biologically-relevant carbonate minerals, calcite (Ωc) and aragonite (Ωa) were calculated throughout the water column from dissolved inorganic carbon (DIC) and total alkalinity (TA) data collected in spring and summer of 2009. Results show that the highest Ωc (~9.0) and Ωa (~ 5.8) values were found in surface water of the Changjiang plume area in summer, whereas the lowest values (Ωc=~2.7 and Ωa=~1.7) were concurrently observed in the bottom water of the same area. This divergent behavior of saturation states in surface and bottom waters was driven by intensive biological production and strong stratification of the water column. The high rate of phytoplankton production, stimulated by the enormous nutrient discharge from the Changjiang, acts to decrease the ratio of DIC to TA, and thereby increases Ω values. In contrast, remineralization of organic matter in the bottom water acts to increase the DIC to TA ratio, and thus decreases Ω values. The projected result shows that continued increases of atmospheric CO2 under the IS92a emission scenario will decrease Ω values by 40–50% by the end of this century, but both the surface and bottom waters will remain supersaturated with respect to calcite and aragonite. Nevertheless, superimposed on such Ω decrease is increasing eutrophication, which would mitigate or enhance the Ω decline caused by anthropogenic CO2 uptake in surface and bottom waters, respectively. Our simulation reveals that under the combined impact of eutrophication and augmentation of atmospheric CO2, the bottom water of the Changjiang plume area will become undersaturated with respect to aragonite (Ωa=~0.8) by the end of this century, which would threaten the health of the benthic ecosystem.

scholarly journals Anammox, denitrification and dissimilatory nitrate reduction to ammonium in the East China Sea sediment

2013 ◽  
Vol 10 (11) ◽  
pp. 6851-6864 ◽  
Author(s):  
G. D. Song ◽  
S. M. Liu ◽  
H. Marchant ◽  
M. M. M. Kuypers ◽  
G. Lavik
Keyword(s):  
Organic Matter ◽  
East China Sea ◽  
Nitrate Reduction ◽  
Outer Shelf ◽  
East China ◽  
The East China Sea ◽  
N Loss ◽  
High Background ◽  
China Sea ◽  
Dissimilatory Nitrate Reduction

Abstract. Benthic nitrogen transformation pathways were investigated in the sediment of the East China Sea (ECS) in June of 2010 using the 15N isotope pairing technique. Slurry incubations indicated that denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) as well as intracellular nitrate release occurred in the ECS sediments. These four processes did not exist independently, nitrate release therefore diluted the 15N labeling fraction of NO3−, and a part of the 15NH4+ derived from DNRA also formed 30N2 via anammox. Therefore, current methods of rate calculations led to over and underestimations of anammox and denitrification respectively. Following the procedure outlined in Thamdrup and Dalsgaard (2002), denitrification rates were slightly underestimated by an average 6% without regard to the effect of nitrate release, while this underestimation could be counteracted by the presence of DNRA. On the contrary, anammox rates calculated from 15NO3− experiment were significantly overestimated by 42% without considering nitrate release. In our study, this overestimation could only be compensated 14% by taking DNRA into consideration. In a parallel experiment amended with 15NH4++14NO3−, anammox rates were not significantly influenced by DNRA due to the high background of 15NH4+ addition. The significant correlation between potential denitrification rate and sediment organic matter content (r = 0.68, p < 0.001, Pearson) indicated that denitrification was regulated by organic matter, while, no such correlations were found for anammox and DNRA. The relative contribution of anammox to the total N-loss increased from 13% at the shallowest site near the Changjiang estuary to 50% at the deepest site on the outer shelf, implying the significant role of anammox in benthic nitrogen cycling in the ECS sediments, especially on the outer shelf. N-loss as N2 was the main pathway, while DNRA was also an important pathway accounting for 20–31% of benthic nitrate reduction in the ECS. Our study demonstrates the complicated interactions among different benthic nitrogen transformations and the importance of considering denitrification, DNRA, anammox and nitrate release together when designing and interpreting future studies.

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