Importance of planktonic community respiration on the carbon balance of the East China Sea in summer

Abstract. A tremendous amount of organic carbon respired by planktonic communities has been found in summer in the East China Sea (ECS), and this rate has been significantly correlated with fluvial discharge from the Changjiang River. However, data related to this issue in other seasons have rarely been collected. To evaluate and reveal the potential controlling mechanism of organic carbon consumption in spring in the ECS, research using stations covering almost the entire ECS shelf was conducted in the spring of 2009 and 2010. During both periods, the fluvial discharges were similar, and these rates were comparable to high riverine flow in summer. Interestingly, planktonic community respiration (CR) varied widely in both springs; in 2009, the level of CR was double that of 2010, with mean (± SD) values of 111.7 (± 76.3) and 50.7 (± 62.9) mg C m−3 d−1, respectively. The CR was positively linearly regressed with concentrations of particulate organic carbon and/or chlorophyll a (Chl a) in 2009 (all p< 0.01). These results suggest that the rate was dependent on planktonic activities, especially that of phytoplankton, in 2009. During this period, phytoplankton growth flourished due to allochthonous nutrients discharged from the Changjiang River. Furthermore, higher phytoplankton growth leaded to the absorption of an enormous amount of fugacity of CO2 (fCO2) in the surface waters, even with a significant amount of inorganic carbon regenerated via CR. In 2010, there were even more riverine runoff nutrients into the ECS than in 2009. Surprisingly, the growth of phytoplankton in 2010 was not stimulated by enriched nutrients, and its growth was likely limited by low water temperature and/or low light intensity. Low temperature might also suppress planktonic metabolism, and this could explain why the CR was lower in 2010. During this period, lower surface water fCO2 might have mainly been driven by physical process(es). To conclude, these results indicate that organic carbon consumption (i.e. CR) in the ECS in spring might be controlled by the magnitude of planktonic activities and physical factor (e.g. temperature), and that the latter is especially important during a cold spring season. This further suggests that the high intraseasonal variability of organic carbon consumption needs to be kept in mind when budgeting the annual carbon balance.

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The influence of episodic flooding on a pelagic ecosystem in the East China Sea

Biogeosciences ◽

10.5194/bg-14-2597-2017 ◽

2017 ◽

Vol 14 (10) ◽

pp. 2597-2609 ◽

Cited By ~ 1

Author(s):

Chung-Chi Chen ◽

Gwo-Ching Gong ◽

Wen-Chen Chou ◽

Chih-Ching Chung ◽

Chih-Hao Hsieh ◽

...

Keyword(s):

East China Sea ◽

Extreme Rainfall ◽

Sea Surface Salinity ◽

East China ◽

Community Respiration ◽

The East China Sea ◽

Pelagic Ecosystem ◽

Surface Salinity ◽

China Sea ◽

Flooding Period

Abstract. This study was designed to determine the effects of flooding on a pelagic ecosystem in the East China Sea (ECS) with a focus on plankton activity and plankton community respiration (CR). In July 2010, a flood occurred in the Changjiang River. As a comparison, a variety of abiotic and biotic parameters were monitored during this flooding event and during a non-flooding period (July 2009). During the flood, the Changjiang diluted water (CDW) zone covered almost two-thirds of the ECS, which was approximately 6 times the area covered during the non-flooding period. The mean nitrate concentration was 3-fold higher during the 2010 flood (6.2 vs. 2.0 µM in 2009). CR was also higher in the 2010 flood: 105.6 mg C m−3 d−1 vs. only 73.2 mg C m−3 d−1 in 2009. The higher CR in 2010 could be attributed to phytoplankton respiration, especially at stations in the CDW zone that were not previously characterized by low sea surface salinity in 2009. In addition, zooplankton (> 330 µm) were another important component contributing to the high CR rate observed during the 2010 flood; this was a period also associated with a significant degree of fCO2 drawdown. These results collectively suggest that the 2010 flood had a significant effect on the carbon balance in the ECS. This effect might become more pronounced in the future, as extreme rainfall and flooding events are predicted to increase in both frequency and magnitude due to climate change.

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Effects of flooding on organic carbon consumption in the East China Sea

Biogeosciences Discussions ◽

10.5194/bgd-12-5609-2015 ◽

2015 ◽

Vol 12 (7) ◽

pp. 5609-5639 ◽

Cited By ~ 2

Author(s):

C.-C. Chen ◽

G.-C. Gong ◽

W.-C. Chou ◽

C.-C. Chung ◽

F.-K. Shiah ◽

...

Keyword(s):

East China Sea ◽

Sea Surface Salinity ◽

East China ◽

Community Respiration ◽

The East China Sea ◽

Surface Salinity ◽

Mean Values ◽

China Sea ◽

Flood Period ◽

The Mean

Abstract. This study was designed to determine the effects of flooding on plankton community respiration (CR) in the East China Sea (ECS). In July 2010, a devastating flood occurred in the Changjiang River; the mean monthly discharge was 60 527 m3 s−1. To compare, the variables were also examined in the low riverine flow of July 2009 (33 955 m3 s−1). During the flooding, the Changjiang diluted water (CDW) zone, the sea surface salinity (SSS) was ≤ 31 psu, covering almost two thirds of the ECS, which was approximately six times that in the non-flooding period. The mean nitrate concentration was higher in 2010 (6.2 μM) than in 2009 (2.0 μM). However, in the 2010 flood, the mean values of Chl a and the bacterial biomass were only slightly higher or even lower than in 2009. Surprisingly, however, the CR was still higher in the flood period than in the non-flood period, with mean values of 105.6 and 73.2 mg C m−3 d−1, respectively. The higher CR in 2010 could be attributed to vigorous plankton activities, especially phytoplankton, at stations in the CDW zone, which were not mostly covered by low SSS in 2009. There was a huge amount of fCO2 drawdown in the 2010 flood. These results suggested that the devastating flood in 2010 had a significant effect on the carbon balance in the ECS. This effect might become more pronounced as extreme rainfall events and flooding magnitudes increase dramatically throughout the world.

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The influence of episodic flooding on pelagic ecosystem in the East China Sea

10.5194/bg-2016-246 ◽

2016 ◽

Author(s):

Chung-Chi Chen ◽

Gwo-Ching Gong ◽

Wen-Chen Chou ◽

Chih-Ching Chung ◽

Chih-Hao Hsieh ◽

...

Keyword(s):

East China Sea ◽

East China ◽

Community Respiration ◽

The East China Sea ◽

Pelagic Ecosystem ◽

Mean Values ◽

Chl A ◽

China Sea ◽

The Mean ◽

Flooding Period

Abstract. This study was designed to determine the effects of flooding on pelagic ecosystem in the East China Sea (ECS), especially on plankton community respiration (CR). In July 2010, a flood occurred in the Changjiang River. As a comparison, a variety of both abiotic and biotic parameters were monitored, as well as in July 2009, a non-flooding period. During the flooding, the Changjiang diluted water (CDW) zone covered almost two thirds of the ECS, which was approximately six times that of the non-flooding period. The mean nitrate concentration was higher in 2010 (6.2 μM) than in 2009 (2.0 μM). However, during the 2010 flood, the mean values of Chl a and bacterial biomass were only slightly higher or even lower than in 2009. However, the CR was still higher in 2010 than in 2009, with mean values of 105.6 and 73.2 mg C m−3 d−1, respectively. The higher CR in 2010 could be attributed to vigorous plankton metabolic activities, especially phytoplankton, at stations in the CDW zone, which were not characterized by low SSS in 2009. In addition, zooplankton might be another important component contributing to the high CR rate observed in 2010. Furthermore, there was a significant amount of fCO2 drawdown in the 2010 flood. These results suggest that the flood in 2010 had a significant effect on the carbon balance in the ECS. This effect might become more pronounced in the future, as extreme rainfall events and flooding magnitudes are predicted to increase globally due to climate change.

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