Nutrient limitation of phytoplankton in anticyclonic eddies of the northern South China Sea

Abstract. Baroclinic instability modulated by topography leads to the formation of two anticyclonic eddies in the northern South China Sea: the Hong Kong Southeast Anticyclonic Eddy (HKSEACE) and the Hainan Island East Anticyclonic Eddy (HIEACE). In these eddies, downwelling caused by a depressed pycnocline leads to high temperature, low salinity, impoverished nutrients, reduced Chl-a concentrations, and picoplankton dominance of phytoplankton assemblages in the euphotic zone. We tested the hypothesis that experimental nutrient enrichment would relieve biomass limitation of phytoplankton by opportunistic response of taxa with low nutrient affinity. Our results confirm that phytoplankton samples incubated in vitro under nutrient enriched conditions attained higher biomass, change in taxonomic dominance from dinoflagellates to diatoms, and shift in size class dominance from picoplankton to nanoplankton and netplankton. These responses were evident only when limitation to more than one nutrient was relieved. Phytoplankton in HKSEACE appeared to be co-limited by nitrogen and phosphorus, whereas at HIEACE it was co-limited by nitrogen, phosphorus and also silicon.

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Formation and Dynamics of a Long-Lived Eddy Train in the South China Sea: A Modeling Study

Journal of Physical Oceanography ◽

10.1175/jpo-d-17-0002.1 ◽

2017 ◽

Vol 47 (11) ◽

pp. 2793-2810 ◽

Cited By ~ 3

Author(s):

Zhongya Cai ◽

Jianping Gan

Keyword(s):

South China Sea ◽

Wind Stress ◽

South China ◽

Northern South China Sea ◽

Anticyclonic Eddy ◽

The South China Sea ◽

The South ◽

Wind Stress Curl ◽

China Sea ◽

Anticyclonic Eddies

AbstractA process-oriented numerical modeling study was conducted to investigate the formation and underlying forcing of an anticyclonic eddy train observed in the northern South China Sea. Observations showed that long-lived anticyclonic eddies formed an eddy train along an eastward separated jet across the northern South China Sea in summer. The eddy train plays a critical role in regulating ocean circulation in the region. Forced by the southwesterly monsoon and prevailing dipole wind stress curl in the summer, the northward coastal jet separates from the west boundary of the South China Sea basin and overshoots northeastward into the basin. The anticyclonic recirculation of the separated jet forms the first anticyclonic eddy in the eddy train. The jet meanders downstream with a strong negative shear vorticity that forms a second and a third anticyclonic eddy along the jet’s path. These three eddies form the eddy train. These eddies weaken gradually with depth from surface, but they can extend to approximately 500 m deep. The inherent stratification in the region regulates the three-dimensional scale of the anticyclonic eddies and constrains their intensity vertical extension by weakening the geostrophic balance within these eddies. Analyses of the vorticity balance indicate that the eddy train’s negative vorticity originates from the beta effect of northward western boundary current and from the subsequent downstream vorticity advection in the jet. The jet separation is a necessary condition for the formation of the eddy train, and the enhanced stratification, increased summer wind stress, and associated negative wind stress curl are favorable conditions for the formation of the anticyclonic eddies.

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Summer phytoplankton assemblages and carbon biomass in the northern south China sea

Continental Shelf Research ◽

10.1016/j.csr.2020.104276 ◽

2020 ◽

Vol 210 ◽

pp. 104276

Author(s):

Jiang Gui ◽

Yuqiu Wei ◽

Jun Sun ◽

Fengfeng Le ◽

Yuming Cai ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Phytoplankton Assemblages ◽

China Sea ◽

Carbon Biomass

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Eddy characteristics in the northern South China Sea as inferred from Lagrangian drifter data

Ocean Science ◽

10.5194/os-7-661-2011 ◽

2011 ◽

Vol 7 (5) ◽

pp. 661-669 ◽

Cited By ~ 26

Author(s):

◽

Keyword(s):

South China Sea ◽

South China ◽

Large Scale ◽

Northern South China Sea ◽

Temporal Distribution ◽

Height Anomaly ◽

Spatial And Temporal Patterns ◽

China Sea ◽

Eddy Characteristics ◽

Anticyclonic Eddies

Abstract. Cyclonic and anticyclonic eddies from large scale to submesoscale in the northern South China Sea (NSCS) have been statistically characterized based on the satellite-tracked Lagrangian drifters using our developed geometric eddy identification method. There are in total 2208 eddies identified, 70% of which are anticyclonic eddies. If the submesoscale eddies are eliminated, the other eddies in the NSCS will show a 1.2:1 ratio of the number of anticyclones (210) to the number of cyclones (171). The spatial distribution of the eddies is regional: in southwest of Taiwan, the number of anticyclones dominates the number of cyclones, and most of them are the submesoscale anticyclones with small radii; in contrast, the large and medium cyclonic eddies are a little more than the same scale anticyclonic eddies in northwest of Luzon. The temporal distribution of eddy number in the NSCS has a close relation with the Asian monsoon. The number of the large and medium eddies peaks during the winter monsoon, while the submesoscale eddies are apt to generate in the summer monsoon. The spatial and temporal patterns have a good agreement with the results of the sea surface height anomaly (SSHA). The maximum and mean tangential velocities of anticyclones (cyclones) are 40 (30) cm s−1 and 25 (15) cm s−1, respectively. The calculated normalized vorticities from drifters suggest that although the mesoscale eddies may be considered in geostrophic balance, ageostrophic dynamics and centrifugal effects may play an important role for the growth and decay of the mesoscale cores.

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Contrasting Photophysiological Characteristics of Phytoplankton Assemblages in the Northern South China Sea

PLoS ONE ◽

10.1371/journal.pone.0153555 ◽

2016 ◽

Vol 11 (5) ◽

pp. e0153555 ◽

Cited By ~ 3

Author(s):

Peng Jin ◽

Guang Gao ◽

Xin Liu ◽

Futian Li ◽

Shanying Tong ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Phytoplankton Assemblages ◽

China Sea

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Three long-lived anticyclonic eddies in the northern South China Sea

Journal of Geophysical Research Atmospheres ◽

10.1029/2010jc006790 ◽

2011 ◽

Vol 116 (C5) ◽

Cited By ~ 69

Author(s):

Feng Nan ◽

Zhigang He ◽

Hui Zhou ◽

Dongxiao Wang

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

China Sea ◽

Anticyclonic Eddies

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Supplementary material to "Combined effects of elevated <i>p</i>CO<sub>2</sub> and temperature on biomass and carbon fixation of phytoplankton assemblages in the northern South China Sea"

10.5194/bg-2016-403-supplement ◽

2016 ◽

Author(s):

Guang Gao ◽

Peng Jin ◽

Nana Liu ◽

Futian Li ◽

Shanying Tong ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Carbon Fixation ◽

Northern South China Sea ◽

Combined Effects ◽

Phytoplankton Assemblages ◽

China Sea ◽

Supplementary Material

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Supplementary material to "Biological pumps of carbon, nitrogen, and phosphorus in the northern South China Sea"

10.5194/bg-2021-17-supplement ◽

2021 ◽

Author(s):

Jia-Jang Hung ◽

Ching-Han Tung ◽

Zong-Ying Lin ◽

Yuh-Lin Lee Chen ◽

Shao-Hung Peng ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Nitrogen And Phosphorus ◽

China Sea ◽

Biological Pumps ◽

Supplementary Material

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Polarity Variations of Internal Solitary Waves over the Continental Shelf of the Northern South China Sea: Impacts of Seasonal Stratification, Mesoscale Eddies, and Internal Tides

Journal of Physical Oceanography ◽

10.1175/jpo-d-17-0069.1 ◽

2018 ◽

Vol 48 (6) ◽

pp. 1349-1365 ◽

Cited By ~ 3

Author(s):

Xiaojiang Zhang ◽

Xiaodong Huang ◽

Zhiwei Zhang ◽

Chun Zhou ◽

Jiwei Tian ◽

...

Keyword(s):

South China Sea ◽

Continental Shelf ◽

South China ◽

Northern South China Sea ◽

Internal Tides ◽

Thermocline Depth ◽

China Sea ◽

Seasonal Stratification ◽

Anticyclonic Eddies ◽

The Impact

AbstractSpatiotemporal variations in internal solitary wave (ISW) polarity over the continental shelf of the northern South China Sea (SCS) were examined based on mooring-array observations from October 2013 to June 2014. Depression ISWs were observed at the easternmost mooring, where the water depth is 323 m. Then, they evolved into elevation ISWs at the westernmost mooring, with a depth of 149 m. At the central mooring, with a depth of 250 m, the ISWs generally appeared as depression waves in autumn and spring but were elevation waves in winter. Seasonal variations in stratification caused this seasonality in polarity. On the intraseasonal time scales, anticyclonic eddies can modulate ISW polarity at the central mooring by deepening the thermocline depth for periods of approximately 8 days. During some days in autumn and spring, depression ISWs and ISWs in the process of changing polarity from depression to elevation appeared at time intervals of 10–12 h because of the thermocline deepening caused by internal tides. Isotherm anomalies associated with eddies and internal tides have a more significant contribution to determining the polarity of ISWs than do the background currents. The observational results reported here highlight the impact of multiscale processes on the evolution of ISWs.

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