Spatial and temporal properties of water column dynamics in the East China Sea.

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.

Download Full-text

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

10.5194/gmd-2019-236 ◽

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).

Download Full-text

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

Biogeosciences Discussions ◽

10.5194/bgd-10-5555-2013 ◽

2013 ◽

Vol 10 (3) ◽

pp. 5555-5590 ◽

Cited By ~ 2

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.

Download Full-text

Features in REE and Methane Anomalies Distribution in the East China Sea Water Column: a Comparison with the South China Sea

Water Resources ◽

10.1134/s0097807819050142 ◽

2019 ◽

Vol 46 (5) ◽

pp. 807-816

Author(s):

Le Duc Luong ◽

Renat B. Shakirov ◽

Nguyen Hoang ◽

Ryuichi Shinjo ◽

Anatoly Obzhirov ◽

...

Keyword(s):

South China Sea ◽

Water Column ◽

East China Sea ◽

South China ◽

Sea Water ◽

The South China Sea ◽

East China ◽

The East China Sea ◽

The South ◽

China Sea

Download Full-text

High-Resolution Vertical Observations of Phytoplankton Groups Derived From an in-situ Fluorometer in the East China Sea and Tsushima Strait

Frontiers in Marine Science ◽

10.3389/fmars.2021.756180 ◽

2022 ◽

Vol 8 ◽

Author(s):

Qian Xu ◽

Shengqiang Wang ◽

Chiho Sukigara ◽

Joaquim I. Goes ◽

Helga do Rosario Gomes ◽

...

Keyword(s):

High Resolution ◽

Water Column ◽

East China Sea ◽

Green Algae ◽

Brown Algae ◽

East China ◽

The East China Sea ◽

China Sea ◽

Tsushima Strait

Vertical distribution of phytoplankton composition in the East China Sea (ECS) and Tsushima Strait (TS) was highly variable in the region where the Changjiang River diluted water (CDW), Kuroshio water (KW), and Tsushima water (TW) intersected. An in-situ multiple excitation fluorometer was used to obtain the high-resolution phytoplankton groups data from every meter of the water column. Sharp differences were noted in the distribution of phytoplankton groups in the CDW, KW, and TW. In the CDW, brown algae were generally present ~60% of all depths with exception of subsurface chlorophyll-a maximum (SCM), whereas cyanobacteria (>40%) and green algae plus cryptophytes (>40%) were found above and below the SCM, respectively. In TW, where chlorophyll a (CHL) was lower than in the CDW, brown algae predominated the water column (>60%) and SCM (>80%), except the surface layer where cyanobacteria dominated. In KW, a high fraction of cyanobacteria (>40%) extended up to 40 m, while brown and green algae dominated (>60%) the deeper waters below 40 m at western and eastern stations, respectively. These results can be further related to water property and nutrient concentration of the water masses in each region. This new data show that the in-situ multiple excitation fluorometer can be a powerful tool to estimate high-resolution vertical profiles of phytoplankton groups on a large scale in marine environments.

Download Full-text

Carbonate mineral saturation states in the East China Sea: present conditions and future scenarios

Biogeosciences ◽

10.5194/bg-10-6453-2013 ◽

2013 ◽

Vol 10 (10) ◽

pp. 6453-6467 ◽

Cited By ~ 25

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 the 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.

Download Full-text